# Modern MTB Constuction - 2021 in review



## natzoo (Jan 21, 2009)

Happy New Year!

The past year I started working with Nick at Neuhaus Metalworks to design and build some pretty cool bikes. We have made a lot of progress, so I thought it would be good to do a recap to benchmark our progress and serve as a reference/inspiration for other framebuilders.

To give some background, Nick is the framebuilder, I am the armchair engineer/CAD monkey. We work together to figure things out. I bring his bikeCAD into the 3D CAD world, handle the 3D printing process, then he builds the frames. 











*3D Printing:*
Over the past year, we spent several hundred hours and several thousands of dollars designing and printing prototypes. I found that the design freedom of 3D printing has really enabled some really cool workflows.































After all the expensive dust settled, I think 3D printing is the future of custom framebuilding. The only limiting factor is people’s CAD skills. Better fire up those Fusion360 tutorials. I think 3D printing is more accessible than most people realize.

*How to build a rear end:*








*Chainring and tire clearance:*
One of the most challenging aspects of designing a modern mountain bike is getting enough clearance for the tires. The worst pinch point happens at the chainstay, between the tire and the chainring. 










These are the clearances I design to:

Tire clearance: 6mm on each side
Chainring clearance: 2mm
SRAM publishes their crank and chainring and dimensions: https://www.sram.com/globalassets/d...ons/mtb/2021-mtb-frame-fit-specifications.pdf
Shimano’s are not published but are floating around. They are slightly more conservative than SRAM's

*Tire Clearances:*
Go/no go based on 6mm tire clearance, 6.5mm thick yoke, and 2mm chainring clearance.

Wheel and TireChainstay52mm (boost)55mm (mid boost?)56.5mm (super boost)29x2.6420yesyesyes29x2.8420no (1.5mm short)yesyes29x3.0420nono (.3mm short)yes29x2.6 *without yoke**440 32t chainringyesyesyes27.5x3.0 *without yoke**430 32t chainringyesyesyes29x2.4 *without yoke**430 32t chainringyesyesyes
 
*Your mileage will vary without a yoke, it all depends on how much you dimple the stays and the exact profile of your tire.

The chainstay is constructed with .75x.035in tubing with a single 11deg bend. I have found all pre-made chainstays are a trap.












*Seat tube Design:*
The seat tube is made with straight 1.375x.035” Chromoly tubing a welded on topper for several reasons:

availability
they allow for 31.6 droppers
the thick topper distorts less and is easier to ream
the thick topper reinforces the TT to ST junction










There are two things you need the seattube to do:

You want to clear the tire
You want the saddle to be in the right spot for pedaling
You get two parameters to fiddle with:

offset
actual seat tube angle
The combination of the offset, angle, and saddle height gives you an effective seat tube angle. This is what I have found works well:








Even in an edge case, it gives enough clearance for a 29x2.6









A few tips:

It is better to minimize the offset. large offsets cause the seat tube to be slacker at full saddle extension
Taller riders tend to need steeper seat tube angles
shorter riders tend to need slacker angles
*Seatstays:*
I don’t have much to say about seatstays, except that the material is super limited at the moment. Single bends are cool, S bends are cool too.

Typical Seatstay Tubes:

1/2x.035
9/16x.035
5/8x.035


*Design Examples :*
Here are a few construction drawings of a Solstice. Hopefully, they can help shed some light on the design and fabrication process. 

These are construction drawings, so some dimensions are missing. For example, the wall thicknesses and butts are specified by Nick’s experience and expertise.

*Medium:*














































*Large: *















































Moving forwards, I am going to make an effort to put more information and answer questions on this forum. I have learned a lot from the mid-school builders that have taken the time to document and publish their processes. I hope to do the same and encourage others to do so as well. Having a positive, open, and inclusive community benefits us all.


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## neongreen (Jan 6, 2010)

Thanks for sharing. It gives a beginner like me a lot of good info to stew on.

Just for contextual information, how much would one expect to pay for a 3D printed yoke? And what material?


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## natzoo (Jan 21, 2009)

neongreen said:


> Thanks for sharing. It gives a beginner like me a lot of good info to stew on.
> 
> Just for contextual information, how much would one expect to pay for a 3D printed yoke? And what material?



Great question. Parts are printed from 316 stainless steel. Printing prices are more or less by weight, and my yokes weigh ~130g.

The majority of printing fabs in the US view additive manufacturing as a means for prototypes or as a novelty. They have a more traditional workflow: sales rep > account manager > drawing > technician > print > metrology. The cost of prints reflects this: ~$4/g. The benefit is they handle all the potential issues with 3D printing for you. Yoke Price: $400-500

I think the fabs in Asia have a much better approach towards low volume production. The price is much cheaper, but you need to have a solid understanding of the printing process to design your parts properly. You give them a file, and they just print it. There are no guarantees about print warpage and support removal. I actually prefer it this way.

Jens at 3dpbs prints in Asia. He charges $1.14USD/g. Since he has a lot of experience printing bike parts, he is a great bridge to the printing process. That being said, you still need to design your parts properly for additive. Yoke Price: ~$150-200

Hope that sheds some more light.


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## Kmccann137 (Jul 10, 2017)

I would like to learn to do carbon work. From my perspective that’s where you can really innovate because very few are doing carbon work.


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## Blatant (Apr 13, 2005)

Not a frame builder, but wanted to give a thumbs up for an excellent post.


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## chomxxo (Oct 15, 2008)

Kmccann137 said:


> I would like to learn to do carbon work. From my perspective that’s where you can really innovate because very few are doing carbon work.



Agreed. Look, great post informing what it takes to design a frame, I appreciate the detail and the amount of work it takes.

That said, as a potential buyer: what does Neuhaus Metal Works do that hasn't been done by custom frame builders all over? The Custom option is where I'd start.

The geometry and performance of the stock models is decent but nothing outside the box. There are some people who want to have a brand that nobody else has, but beyond that niche market I don't see the value.

Now, build me a carbon 36er and you'll be onto something revolutionary! I know a custom carbon builder and he was willing to take a shot at a project like this, except for the fork. I'm just saying, do something that stands out, if you're going to put so much work into it.


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## AdamR83 (Jan 21, 2021)

Great post, thank you!

I love the seatstay yoke. A damn sight easier than doing that same joint manually too!

Interested, if you wouldn't mind expanding, in your comment about pre-shaped chainstays being "a trap"... I've not built many frames but the two I have with Columbus stays (one single bend, one double bend) worked out nicely. I did perhaps have to design 'around' the stays a bit, but I do think I ended up with a better result overall using these rather than a plain round tube.


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## Prognosticator (Feb 15, 2021)

I don't know jack about frame fabrication, but I appreciate the detail of this post. Very interesting! Wishing much success!


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## Little_twin (Feb 23, 2016)

AdamR83 said:


> I did perhaps have to design 'around' the stays a bit


This is the “trap”. You compromise your design based on what is available. 


Sent from my iPhone using Tapatalk


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## natzoo (Jan 21, 2009)

AdamR83 said:


> Interested, if you wouldn't mind expanding, in your comment about pre-shaped chainstays being "a trap"... I've not built many frames but the two I have with Columbus stays (one single bend, one double bend) worked out nicely. I did perhaps have to design 'around' the stays a bit, but I do think I ended up with a better result overall using these rather than a plain round tube.


To me, modern construction is about building the bike that you want: the chainstay you want, the tires you want, the wheel size you want. I find a lot of people design bikes around what tubes are available. They fall into the trap of buying the "29er tube set" which was designed for bikes in 2010. You end up limited to 440mm long chainstays and 2.3in clearance.

To be clear, there is nothing wrong with a bike with long chainstays and narrow tires, but to me, you shouldn't let the tube someone had made 10 years ago tell you how to design your bike.

All the premade stays look great, they just don't give you enough freedom to build a modern bike.


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## natzoo (Jan 21, 2009)

I realized the original post did not easily allow you to view the small drawings, so I am re-posting them here larger.

I'm also going to include an all-inclusive geo chart here. We call it "Full Spectrum Sizing". It is way more than a colorful chart. There was a lot of testing to establish the size range and there is an entire backend and digital workflow that allows us to fabricate the frames without being a total pain in the ass.



















*Medium:*












































*Large: *


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## natzoo (Jan 21, 2009)

[place holder]


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## a_j_p (May 19, 2019)

I have virtually no experience with additive metals but quite a bit with additive plastics. Your comment about knowing how to design for additive makes me curious: how do you account for additive material properties? Do you worry about part orientation during printing, etc.? Is this part of what your initial money spending was investigating?


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## natzoo (Jan 21, 2009)

a_j_p said:


> I have virtually no experience with additive metals but quite a bit with additive plastics. Your comment about knowing how to design for additive makes me curious: how do you account for additive material properties? Do you worry about part orientation during printing, etc.? Is this part of what your initial money spending was investigating?


Printing metals have the exact same design constraints and considerations as printing plastic:

heat warpage
orientation
support material
Since you can print plastic, you can print metals too!

There are a few differences for metal prints:

If a small part fails during a build, it will likely ruin the entire batch of parts
You need to account for powder removal
support material is much harder to remove (grinder, rotary tools, etc...)
You can see examples of the supports below, circled in red. These need to be removed manually by a technician. Notice how my yoke designes are self-supported, with minimal support material.









With regards to mechanical and material properties, the jury is still out on that one. It varies by printer model, print settings, print orientation, post-heat treatment, etc... There are several papers out there that try to nail that down. The general consensus and the testing we have done point to printed stainless is within 10% of the yield stress of bulk stainless, but reduced elasticity, and most likely reduced fatigue life.

One of the best pieces of advice my professors taught me is that strength comes from geometry, not material properties. With 3D printing, you have total freedom to create strong shapes and put material where you need it. This can easily overcome the limitations of printed materials.











That being said, will the printed parts I designed eventually break? No one knows for sure. Every new technology comes with risks. To give some perspective, traditionally constructed steel frames crack all the time. All my parts are pretty beefy, designed to weld easily (heat stress from welding is the real frame killer), and none of them are in cantilevered locations (stems, forks, bars), so I have reasonable confidence in their strength.


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## a_j_p (May 19, 2019)

It's definitely interesting to see this - I'll have to read/investigate more. Printing has not ever struck me as practical/approachable for someone like me who just builds a few frames a year for myself... but certainly things will change as printing advances and maybe I am completely wrong to begin with.

Anyway, appreciate the response and you throwing this out there for everyone.


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## AdamR83 (Jan 21, 2021)

natzoo said:


> To me, modern construction is about building the bike that you want: the chainstay you want, the tires you want, the wheel size you want. I find a lot of people design bikes around what tubes are available. They fall into the trap of buying the "29er tube set" which was designed for bikes in 2010. You end up limited to 440mm long chainstays and 2.3in clearance.
> 
> To be clear, there is nothing wrong with a bike with long chainstays and narrow tires, but to me, you shouldn't let the tube someone had made 10 years ago tell you how to design your bike.
> 
> All the premade stays look great, they just don't give you enough freedom to build a modern bike.


Thanks for your thoughtful response!

I do agree to a point - certainly if you mindlessly stick together a full tube set from X manufacturer you will end up with the sort of geo / clearances you mention, but with some thought it doesn't have to be that way.

Not a lot of us have access to 3D printing, or can justify $500 for a BB yoke when that will buy a full set of 853 tubes, but it is possible to do short chainstays on a 29er (sub 420) with off the peg chainstays, clearance for a 2.5 tyre, without a BB yoke and without crimping the hell out of the tubes. Light, cheap, strong: all three. Holy grail.

Sorry for the thread drift - I'm stoked to see the tech I studied for my degree nearly 20 years ago making it to bikes!


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## natzoo (Jan 21, 2009)

AdamR83 said:


> Not a lot of us have access to 3D printing, or can justify $500 for a BB yoke when that will buy a full set of 853 tubes, but it is possible to do short chainstays on a 29er (sub 420) with off the peg chainstays, clearance for a 2.5 tyre, without a BB yoke and without crimping the hell out of the tubes. Light, cheap, strong: all three. Holy grail.
> 
> Sorry for the thread drift - I'm stoked to see the tech I studied for my degree nearly 20 years ago making it to bikes!


No worries, there are multiple ways to build a bike, that's part of the fun with framebuilding!

I do want to make a slight correction though, a printed yoke is not $500USD. It is much less. You can print a single-sided yoke for as low as $60USD, or buy a CNC yoke for that price. The price is only going to come down over time.

One of the points I am trying got make is that the barrier to 3D printing is not the cost, it is the design knowledge and CAD ability.


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## fuzz_muffin (Dec 24, 2017)

That ss/st junction is the tits!

Thanks a ton for the info dump. I do often wonder how much all this extra effort is worth compared to just compromising the design slightly to reduce cost, especially considering the ultimate limitation of the hardtail platform. Coming from a guy that rode a "modern" hardtail for a bit on all the things, whilst you can ride almost everything on one, they will always be limited capability wise compared to a good full squish. 

I guess what I'm getting at is the goal of design effort seems to be more "Optimise the hardtail so it can be as 'good' as possible", rather than using the same resources to "Design the 'best' two wheeled vehicle for terrain x". 
At what practical point is it just throwing money at it for the fun of design? Thoughts? 

Cheers. 
Also excuse the spelling and grammar, written on the throne.


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## AdamR83 (Jan 21, 2021)

Apologies Daniel, I must have skimmed your pricing post even more poorly than I thought! The 3dbps service sounds very well priced, especially for a one sided version.

Hadn't seen the Cobra yoke before, that is an excellent option too!

I agree about learning CAD and learning to design for 3D printing... Two different things and quite a time investment, even individually. Definitely more of a barrier than cost right now, but perhaps we will start to see more off the shelf options cropping up in the future.

This all makes me want to build another frame, dammit...


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## BadgerOne (Jul 17, 2015)

After reading what you've written about the printing of stainless junction components, to me the next logical step and in my mind the most exciting is material advancement. Specifically, you mentioned stainless printed parts approaching the characteristics of bulk stainless. Of course there are many grades of stainless. I'd be interested in attempting to print maraging stainless. If this were possible, it could be combined with air hardening steel such as 853 or even another maraging steel like 953, and in theory the result would be the ability to join thin-walled steels of exceptional strength and toughness but with high compliance for comfort and liveliness. Combining these kinds of alloys actually increases the strength of the HAZ at the joins during welding due to precipitate hardening. Just something to think about.


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## pvd (Jan 4, 2006)

This is an interesting take on your first year working around bicycles. Definitely, there is some perspective worth sharing especially what you've done with printing.

The good:

1. I love the clear drawings and measures.
2. If folks learn from this that 3D parametric CAD are crucial skills for advanced design, we are all better off.
3. It's good for folks to hear from someone doing real CAD work to understand it's value.

There are a few problems with all this on a fundamental level:

1. The frame geometry being presented is largely circa 2014-2017. That's fine for the current era as that's almost to where the wall is hit using current control systems. Most modern COMMERCIALLY AVAILABLE geometry is a little beyond this, essentially 2017 era. It's difficult to call this 'modern' within the context of custom, one off work.

2. If the intent is to present a modern methodology for design and construction, the geometry matrix does a lot to counter that. It gives the impression that a long antiquated method (or two) are being applied to compute and compile it. It's apparently using driven rather than driving parameters to describe the bike, calculate, and scale around. This should be corrected as it's a problem for the builder as well as the consumer. Reference dimensions may be presented but as such in a clear way. As it stands, it destroys all credibility...and this is just a simple matrix.

3. Several important dimensions such as front center, height of ESA calculation, wheel diameters, fork length, offset, and applicable sag are left out of the matrix when they are crucial to understanding the bike in question. I understand that this is just work copied from old catalogs but it really doesn't reflect what is being done in the modern era.

4. STA is inappropriately labeled.

5. There is a lot of important information that could be communicated in the detail 'prints' but isn't. If this is being presented outside of the workshop it would be worth detailing them.









This sketch from another thread points to the exact problem.


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## reynoldswrap (Mar 10, 2020)

Wow, thank you for posting all of this info. I can only imagine the amount of hours that went into creating parametric models for each of these parts, but it looks like it will be well worth it. I'm eagerly waiting for the day when I can I can send a bikecad file or frame drawing and get a custom printed "lugset" at a reasonable price. Definitely would like to learn more about printing conscious design


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## dr.welby (Jan 6, 2004)

What's going on with that ST/DT/BB piece in the second picture? I was hoping to see that instead of bent seat tubes.


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## pvd (Jan 4, 2006)

dr.welby said:


> What's going on with that ST/DT/BB piece in the second picture?


From my understanding, that is a $150 part that eliminates two scalloped miters and replaces them with two square miters and another joint. It's a little weaker than just connecting the tubes in a traditional way but it's printed.


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## dr.welby (Jan 6, 2004)

pvd said:


> eliminates two scalloped miters


And a bending operation, and having to clock one miter to the bend, and the other miter to the miter at the other end of the down tube.


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## natzoo (Jan 21, 2009)

pvd said:


> There are a few problems with all this on a fundamental level:
> 
> 1. The frame geometry being presented is largely circa 2014-2017. That's fine for the current era as that's almost to where the wall is hit using current control systems. Most modern COMMERCIALLY AVAILABLE geometry is a little beyond this, essentially 2017 era. It's difficult to call this 'modern' within the context of custom, one off work.
> 
> ...


You have a strong view of how to design and ride a bike. That is fine, and I appreciate the work and documentation to reach that conclusion. However, that does not mean that it is the only view of how to design and ride a bike.

People come in different shapes and sizes, ride in different terrain, and enjoy different aspects of mountain biking.* There is no singular design philosophy that fits all people,* *nor should there be*. This diversity should be encouraged in the frame-building community, rather than pressuring every new builder into a singular worldview.

Your opinions on geometry might be the future of mountain biking, or they might not. We will never know what is "better" if people are not trying different things. 

To me, the true meaning of "progressive geometry" is about choice. It's the freedom to design the best bike for you, and how you ride, without the physical limitations of what is available, and without the bias of what marketing or others tell you that you should be riding. Some people love climbing. Some people love descending. Some people are afraid of descending. Some people just want to ride fire roads. Some people just want to ride a bike they are used to. That's all cool, and there is a design out there that complements how you like to ride.


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## pvd (Jan 4, 2006)

natzoo said:


> You have a strong view of how to design and ride a bike.


I do. That comes from over 30 years of experience working in this area and doing the hard work and long rides to find out how to do it.

Your math is bad. You need to fix that. You can design and build a bike any way you please but in this post and some others you're teaching others how to do it wrong. There are plenty of places where someone can chose a different scheme to build with but that doesn't change the fundamentals of chassis design.

Take a look at what you are using as driving parameters. They are wrong. Fundamentally wrong. Systematizing using driven parameters is insane.

Frame reach isn’t a driving dimension | Peter Verdone Designs


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## natzoo (Jan 21, 2009)

dr.welby said:


> What's going on with that ST/DT/BB piece in the second picture? I was hoping to see that instead of bent seat tubes.


It is a prototype that we are still testing, particularly with really large 6'5+ riders to see if we can increase the pedaling stiffness. It also happens to be a stepping stone towards a full-suspension design


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## pvd (Jan 4, 2006)

dr.welby said:


> And a bending operation, and having to clock one miter to the bend, and the other miter to the miter at the other end of the down tube.


The part in question does not replace a bent tube. It 'replaces' a straight tube.


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## dr.welby (Jan 6, 2004)

pvd said:


> The part in question does not replace a bent tube


I'm sorry, is that _your_ part?


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## cassieno (Apr 28, 2011)

pvd said:


> From my understanding, that is a $150 part that eliminates two scalloped miters and replaces them with two square miters and another joint. It's a little weaker than just connecting the tubes in a traditional way but it's printed.


What makes you say weaker? What information are you using to assume it's weaker?


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## pvd (Jan 4, 2006)

dr.welby said:


> I'm sorry, is that _your_ part?


Definitely not. I've just seen it's placement on the bike.


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## pvd (Jan 4, 2006)

cassieno said:


> What makes you say weaker? What information are you using to assume it's weaker?


Two welds turning into three with something in the middle that depends on a host of other varaibles.


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## cassieno (Apr 28, 2011)

I guess that's my point. Those host of other variables could be stiffer. Could be more flexy. Just not enough information to accurately assess.

Seems like a "you're trying something new. How dare you!" attack more than anything.


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## pvd (Jan 4, 2006)

cassieno said:


> I guess that's my point....Seems like a "you're trying something new. How dare you!" attack more than anything.


No. It's just not solving a problem.


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## natzoo (Jan 21, 2009)

pvd said:


> I do. That comes from over 30 years of experience working in this area and doing the hard work and long rides to find out how to do it.
> 
> Your math is bad. You need to fix that. You can design and build a bike any way you please but in this post and some others you're teaching others how to do it wrong. There are plenty of places where someone can chose a different scheme to build with but that doesn't change the fundamentals of chassis design.
> 
> ...












Easy there buddy. You can rest assured, I can math pretty well and understand your design philosophy. When I design a bike for myself, I design around my grip position.

Designing a bike for others has totally different constraints than a custom one-off for yourself. Normal people don't have time to be prowling obscure forums to understand the effect of spacers and bar roll on their grip position relative to the BB. They want to compare to something they can already understand, and that is totally fine. Not everyone is looking for a radical bike, some people just want to ride what they are used to.

I respect your perspective. let's have some mutual respect here, keep it positive. Otherwise, it's not worth my time to engage you futher.


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## cassieno (Apr 28, 2011)

pvd said:


> No. It's just not solving a problem.


My last comment on this and then I will stop engaging with you because I literally cannot stand your smug opinion and useless attitude that you bring to any online discussion - Doesn't solve a problem that you know. Because you have never tried.

You spend forever analyzing your designs and building for yourself. Then you spend the rest of your time telling everyone else how worthless they are because they are not you.

You have good documentation but your experience/opinions are so far outside the realm of consumers and professional framebuilders that you are irrelevant to that industry. Your "encouragement" of new framebuilders is the definition of gate-keeping. Every word you type online is to make someone feel like **** for even trying. You actively discourage any form of actual discussion and post obscure links to your website as responses. But I get it, you are the "smartest" guy in the room. It's a true burden to be you and be right all the time. Us plebs are just thankful you are here.... /s.

Where are you opinions on geometry backed up by real world results? Who else has ridden your bikes? What fast riders (because you have said you aren't fast) have been able to take your bikes to the bleeding edge of performance. Actual performance, not just designed performance? 



pvd said:


> That's fine for the current era as that's almost to where the wall is hit using current control systems.


Like wtf is this ****. How dare a frame builder design a frame that works with current control systems. What could they possible be thinking....

3D printed **** is cool. Trying new things is cool. Iterating (instead of staring at numbers on a screen without ever building those iterations) is cool. Building a shitty bike to go on to build better bikes is cool. Learning by doing (including success and failure) is cool.

Your smug as **** attitude is not cool.


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## dr.welby (Jan 6, 2004)

natzoo said:


> let's have some mutual respect here


I have some bad news for you...


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## pvd (Jan 4, 2006)

natzoo said:


> Easy there buddy. You can rest assured, I can math pretty well..


But you're using a completely erroneous method. Who taght you this stuff? You've been drawing for a year and using bad parameters. Why wouldn't you change that?


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## pvd (Jan 4, 2006)

cassieno said:


> My last comment on this and then I will stop engaging with you because I literally cannot stand your smug opinion and useless attitude that you bring to any online discussion - Doesn't solve a problem that you know. Because you have never tried.


Gold.


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## Little_twin (Feb 23, 2016)

pvd said:


> Two welds turning into three with something in the middle that depends on a host of other varaibles.



How about 0 welds turning into 2 with something in the middle?


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## dr.welby (Jan 6, 2004)

Little_twin said:


> How about 0 welds turning into 2 with something in the middle?


I see your two welds and raise you to 4 welds and 28 stress risers


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## Little_twin (Feb 23, 2016)

dr.welby said:


> I see your two welds and raise you to 4 welds and 28 stress risers
> 
> View attachment 1963925


I fold 


Sent from my iPhone using Tapatalk


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## pvd (Jan 4, 2006)

Little_twin said:


> How about 0 welds turning into 2 with something in the middle?


What problem was being solved? What other problems were solved along with it?


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## pvd (Jan 4, 2006)

dr.welby said:


> I see your two welds and raise you to 4 welds and 28 stress risers


What problem was being solved?

Honestly, with the stars, I was trying a different way of designing and trying to not "do everything right". It didn't work. I learned thwt the way I do things is better than other options.


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## Little_twin (Feb 23, 2016)

..


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## eMcK (Aug 22, 2007)

Can we trade pvd for Walt?


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## natzoo (Jan 21, 2009)

Alright now that everyone has gotten it out of their system, let's get the train back on the tracks, and keep it positive.



fuzz_muffin said:


> Coming from a guy that rode a "modern" hardtail for a bit on all the things, whilst you can ride almost everything on one, they will always be limited capability wise compared to a good full squish.
> 
> I guess what I'm getting at is the goal of design effort seems to be more "Optimise the hardtail so it can be as 'good' as possible", rather than using the same resources to "Design the 'best' two wheeled vehicle for terrain x".
> At what practical point is it just throwing money at it for the fun of design? Thoughts?


Totally a valid criticism that I have dwelled on too. If "optimal" means: "the best two wheeled vehicle for terrain X", then a full suspension is going to be the solution. Actually, an e-bike... but that's a can of worms.

There are some intrinsic advantages that hardtails have:

they are more efficient on smooth terrain
require less maintenance
they hold way more water
they are timeless (opinion)
To me, the last point is very important. In 10 years, a full suspension will cost more to fix than it is worth. A custom steel/titanium hardtail will still ride great, and they still have the same cool factor. Mountain biking is already a pretty lavish and wasteful sport. If I am designing toys for adults, I want the toys to last as long as possible to minimize their impact.

Both these bikes are 10 years old. Which would you rather own? I am definitely putting some 2.0 slicks on the waltworks and riding it around town.

















I’m lucky enough to own both a full suspension and a hardtail. The hardtail makes mellower trails exciting, holds a lot of water for long rides, and is always ready to go. The full suspension makes me feel like a super hero. Both are really fun. If I had to choose one, It would be a hardtail.


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## fuzz_muffin (Dec 24, 2017)

natzoo said:


> Alright now that everyone has gotten it out of their system, let's get the train back on the tracks, and keep it positive.
> 
> 
> 
> ...


I honestly don't post much on here or MTBR in general, specifically because of the way this thread was getting derailed. It's not that I can't handle serious review from peers (when it's been solicited), because I'm very familiar with *proper* peer review practices. It's just the vibe here tends to be rather childish and particularly nasty.

Anyway...

Cheers for the reply, I appreciate all those points. To me, 'Fun' beats all other objective reasons, and yes I agree that hardtails are both mad fun and distinct from full squish MTBs. I do love seeing thought and detail being put into fancy hardtail designs, just sometimes I wonder what the practical limit is. Of course it will be different for different people/builders. Personally, I'd rather be riding than nerding on design and trying to reduce a rear centre by 2mm on a trail hardtail, for example.

I should put my cards on the table and say that I've assembled some tubes into a hardtail before, but had to accomodate the design to facilitate the construction method (brazed with pre-formed tubes). It wasn't actually compromised in the end, mainly because I wanted to use 650b wheels and they were an easy fit for the numbers I was chasing. For me, cost is a massive driving factor and I didn't end up desiring anything more complex than simple mitred tube junctions for that bike.

However... I've recently fabbed up a 24" DJ and have thought about making some 'fancy' BMX frames. Here, more considered design choices and compromises had to be made to get it working with simple tube mitre style construction. Unfortunately cost is still a major factor!

And then there's carbon fibre composites...

I'm just rambling now, you make some nice looking bikes and kudos for the post.

-FV


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## fuzz_muffin (Dec 24, 2017)

I suspect your question of which I'd prefer might be strongly dependent on era, a 90s-00s rigid MTB makes for a fantastic road/everything bike, my 1991 Haro escape with drop bars and a rack does alright on fire roads and light trails. Adding FS to that makes them kinda **** at pedalling, which defeats the point.

... I'll take the rigid with slicks please.


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## driver bob (Oct 12, 2005)

monitoring...


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## Ben.land101 (Dec 25, 2012)

fuzz_muffin said:


> That ss/st junction is the tits!
> 
> Thanks a ton for the info dump. I do often wonder how much all this extra effort is worth compared to just compromising the design slightly to reduce cost, especially considering the ultimate limitation of the hardtail platform. Coming from a guy that rode a "modern" hardtail for a bit on all the things, whilst you can ride almost everything on one, they will always be limited capability wise compared to a good full squish.
> 
> ...


I still very much consider myself a FNG in the framebuilding world, but I have built a few frames and have had a taste of the magic kool-aid.
There is still so much more left on the table for the "ultimate" hardtail.
And of course that is the biggest problem with the commercially available frames out there. They're missing the last few percent of 'secret sauce' that make the bike truly next-level. Making a frame for the masses, vs. optimizing the frame for the rider.
Tiny tweaks in optimization have massive performance benefits.

I'm just lucky enough to have gone down this rabbit hole, and have had a chance to build these bikes for myself and experience it first-hand.
Most folks will watch a YouTube review of some new bike that's hyped up to infinity, then ultimately be disappointed when they ride it. All while never truly understanding why.
Squish bikes are a crutch. Just about any flaw in the design can be hidden with enough suspension travel.



It's no secret I've been following and working with PVD for a while now. AFAIK, he's the only one out there laying the groundwork for truly defining what makes mountain bikes work the way we want them to work, without the marketing and trend-following BS.
Bikes are not magic, and they are not more than the sum of their parts. All of the performance on a bike is quantifiable.
PVD can come off as abrasive online, sure. But you all would be foolish to dismiss his work outright.


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## Little_twin (Feb 23, 2016)

..


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## Ben.land101 (Dec 25, 2012)

Little_twin said:


> ..


Is there a reply in there? or just ".."?


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## dr.welby (Jan 6, 2004)

Ben.land101 said:


> PVD can come off as abrasive _abusive_ online, sure.


FTFY



Ben.land101 said:


> But you all would be foolish to dismiss his work outright.


There's only one person "dismissing work" in this thread.


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## Ben.land101 (Dec 25, 2012)

dr.welby said:


> FTFY
> 
> 
> 
> There's only one person "dismissing work" in this thread.


I'm pretty much socially inept in real life, much less on the internet. Are you referring to me dismissing work? or someone else.
Honest question.


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## dr.welby (Jan 6, 2004)

Ben.land101 said:


> I'm pretty much socially inept in real life, much less on the internet. Are you referring to me dismissing work? or someone else.
> Honest question.


Nah you're cool


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## Little_twin (Feb 23, 2016)

Ben.land101 said:


> Is there a reply in there? or just ".."?


Redacted because being a dick isn’t productive 


Sent from my iPhone using Tapatalk


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## Ben.land101 (Dec 25, 2012)

Little_twin said:


> Redacted because being a dick isn’t productive
> 
> 
> Sent from my iPhone using Tapatalk


Ah. Gotcha


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## Ben.land101 (Dec 25, 2012)

natzoo said:


> Printing metals have the exact same design constraints and considerations as printing plastic:
> 
> heat warpage
> orientation
> ...


To actually add to the conversation though, I am curious.
From what I understand, (which is not much) the machine lays a bed of powder, then a laser welds the 'layer', adds another layer of powder, etc.

So why are the supports still needed? Wouldn't the powder building up provide support?

I've never 3D printed anything, but I will be getting one soon (plastic) to start playing and learning more. With the end goal of course to start getting metal parts printed. 

Also, you go by underpaid intern on IG right? I think we chatted a while back about the hose ports.


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## natzoo (Jan 21, 2009)

fuzz_muffin said:


> Personally, I'd rather be riding than nerding on design and trying to reduce a rear centre by 2mm on a trail hardtail, for example.


Totally agree. Before the thread got derailed, I purposefully did not mention anything about what modern geometry is. I think people should build and ride what they like. I actually spend way more time designing cable ports so they can be easily routed and noise-free, than obsessing about chainstay length.

The fundamental purpose of my designs is to *bring down the cost of custom framebuilding, *while maintaining or even improving functionality. 

The biggest driver of cost is skilled labor. The workflow Nick and I developed probably saves 20-30% of the time. We have some designs that save even more, but the world is not ready for them.

*I'll give a few examples....*

*The dual-sided yoke:*











The cost of the printed yokes is already cheaper than a CNC yoke.
It is half the weight (not that it really matters)
It comes pre-mitered
its easier to weld
It locks in the important clearances for you, so you don't end up with an oopsie moment when you put the cranks on.
All that amounts to significant cost and time savings while improving tire clearances and rear end alignment. AND its cheaper!

*UDH dropouts:







*

The simple chainstay and seatstay plugs with the integrated brake mount probably save 50% of the time of rear-end construction
The total system design is lighter
the rear end is more compliant
With these dropouts, combined with my other parts, we can construct an *entire* frame with only four miters (1 toptube, 2 downtube, 1 seattube).
These dropouts are definitely expensive. For reference, the NDS FM160 dropout weighs 180g and costs ~$130 to print. We haven't had the time to do any lab testing on this design, so for now, I just overspec the wall thicknesses, which probably increases the cost of the part by 30%. Even at this inflated price, if you factor in the time savings, this method of construction is still cheaper.

*Bottle Bracket:*
This is a design that I am really excited about (still testing). Long dropper posts and seat tube mounted bottles don't mix well (the bottle boss interferes with dropper insertion). Most custom builders spec studs, but they are expensive ~$5/ea and are frustrating for people to own (no one has a nut driver on their multitool).

My bracket design:

angles the bottle stud, which pulls the top bottle stud out of the seat-tube
it improves the bottle clearance on small frames (5'4 and below)
doubles as a tool strap if you don't want another bottle.
only requires one hole to be drilled, and self indexes against the tube
is *cheaper *than two bottle studs!































These are just a few examples of the stuff I care about and obsess over to fractions of a millimeter. All my designs aim to save time and improve functionality. Some parts are already straight up cheaper than existing methods of construction, which is something that surprises even me.

Now let's take a step back from our egos, and visualize a positive future. As @reynoldswrap posted earlier, there is a world where you can update a CAD model, print out a lug set, and have a frame ready to go. Now imagine, these can be assembled locally, with moderately skilled labor, at an accessible price point. That's the end goal. Right now if you want a custom frame, it costs ~$2000-3000 and you have to wait for 6mo to 1 year. Only "disruptive technology" can get those numbers down to something more accessible to the average mountain biker.

And to give people some perspective. I only started printing frame components 6 months ago as a hobby. Imagine if we could all get along and work together, where would we be in 5 years?


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## natzoo (Jan 21, 2009)

Ben.land101 said:


> From what I understand, (which is not much) the machine lays a bed of powder, then a laser welds the 'layer', adds another layer of powder, etc.
> 
> So why are the supports still needed? Wouldn't the powder building up provide support?


Good question, it took me a while to wrap my head around this too. two reasons:

The parts are heavy, so gravity can cause your part to tip or rock
the parts warp and change shape during printing. The supports "tie" down the parts



Ben.land101 said:


> Also, you go by underpaid intern on IG right? I think we chatted a while back about the hose ports.


Correct!


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## a_j_p (May 19, 2019)

I would assume Natzoo would know quite a bit. But my understanding is there are likely as many process variations to metal printing as there are to plastic printing... And every plastic printing process has its own advantages and disadvantages depending on what your desired end result is.

My limited experience with metal printing is that they are effectively printing the end result of what you would get with a MIM (metal injection molded) part, then de-binding and sintering... when I saw it done there were a few methods of laying the metallic powder+binder, including one version that basically copied the process of an FDM plastic printer. But that was many years ago I was looking into it and I'm positive things had to have changed since then.

But I am very curious about this - since I know for certain I would not use some process of printed plastic parts for certain applications but have no insight for what I'd want with metal prints.


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## dr.welby (Jan 6, 2004)

natzoo said:


> The fundamental purpose of my designs is to *bring down the cost of custom framebuilding, *while maintaining or even improving functionality.


This reminds me of the Tim Isaac lugs at Trek that were designed to speed up the process, but without the constraints of investment casting.


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## Ben.land101 (Dec 25, 2012)

That bottle bracket is nifty. So the whole thing gets brazed on, with the bottom lug into the seat tube, and then the top hole gets a regular stud added?


One other thing that's always been bugging me about the 3d printed parts, is the joining of them to the bicycle tubing.
For reference, I am a welding "expert" (I work in welding inspection, education, and non-destructive testing for my day job)

A while back someone asked me for advice about welding the 316L printed part to (what is essentially) 4130 tubing. I'm gonna copy and paste the email I sent as a reply below with personal stuff redacted, lots of stuff in it to unpack.
But TL;DR, I would love to see some academic research about welding them together If anybody knows of any, mainly just because of the grain structure. The dissimilar materials is not really an issue.
I've seen lots of anecdotal stuff, and maybe I'm just afraid of the unknown, but It'll take more convincing for me to put 3DP structural parts on my bike.



_I would definitely get some 309L filler, if you don't have it already.
It's the go-to for stainless to mild (and low alloy) steel. It will get you more ductility in the finished weld, while still having a tensile strength in the 80k range.
The way I understand it, it has more Chromium & Nickel in it to help prevent it becoming brittle after mixing and diluting with the 4130.

But that's just the 'standard' knowledge of welding dissimilar metals. Welding 3D printed stuff is still somewhat uncharted territory.
All of the industries really pushing the boundaries of what can be done with it are still pretty quiet about it. Trade secrets, defense, NDA's and all that.
We have to wait a few more years for the trickle down of technology to get to us.
Or in other words, I just can't find anything academic about welding 3D printed metals. Maybe your Google-Fu is better than mine.

My biggest concern is how homogenous the 3DP part may or may not be. Any small voids (or contamination in the powder they used) can cause trouble once you start an arc on it and begin melting things together.
So I would definitely get everything as clean as possible before welding, including sanding the printed part down just a bit to make sure it's as pristine as possible in the weld area. 
And I mean sanding it, not sandblasting. I always try to avoid sandblasting for something that's going to be welded.
That of course doesn't help for anything internal, but every bit helps. I also am guessing that any defects or unbonded particles are most likely to be near the surface of the part.

That, and the overall grain structure of the printed material.
You mentioned it had a sintering heat treatment done after printing, which should help.
Although I think (hope) that is the wrong terminology. Sintering implies the metal particles are just 'stuck' together, instead of being truly bonded into one solid piece.
I suspect the post-print heat treatment is more of a normalizing or annealing step to get rid of any stresses from the printing process.

I would also purge it.
You don't have to go crazy like high-purity stainless or titanium, you just need to prevent the severe oxidation (sugaring) that stainless can get.
It'll also make it weld a bit smoother, preventing any extra contamination mixing in from the backside of the weld.

I may also just be overly concerned, I just don't have any real world experience with 3D printed metal yet.
That, and everything I've been able to read about it is just the 'sensationalized' sort of useless article._

But yeah. Lots of talking points there (and maybe some un-answered questions) just from the welding of the parts.


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## pvd (Jan 4, 2006)

dr.welby said:


> ...abusive...


How is informing someone that they are not doing their geometry calculation correctly abusive? If the intent of this thread was to talk about modern methods and a systematized geometry matrix is in there, why would pointing out a fundamental error be an issue. A discussion doesn't mean that the person that began it is assumed to know what they are talking about. Here, someone with about a year of 'experience' is doing something incorrectly and being informed as such. This isn't a point where there is much design leeway. He is simply doing it wrong. Worse, he's telling others that it is how to do it. That hurts others.


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## dr.welby (Jan 6, 2004)

The bottle mount thing is slick.

With the arms race for adventure bosses, I'm _this close_ to just riveting essentially a 64mm cheese rail  to the down tube.


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## dr.welby (Jan 6, 2004)

pvd said:


> How is informing someone that they are not doing their geometry calculation correctly abusive?


I'm not your therapist.


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## a_j_p (May 19, 2019)

natzoo said:


> to give people some perspective. I only started printing frame components 6 months ago as a hobby. Imagine if we could all get along and work together, where would we be in 5 years?


I would be willing to invest some time and as needed some $$ to working on this together... I am nearing completion of an FS frame currently where the shock mount would have been a great candidate for a printed part - but I was honestly too intimidated with unknowns to try it and settled for long 4130 mounts and machined aluminum adapters... It would be nice to at least know/try more and collaboratively is always better for me.


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## eva_k (Apr 25, 2021)

This is all quite interesting, thank you so much for sharing all you've learned! My day job is in a 3D printing-adjacent space and it's been super cool to see the technology and methodology evolve from hobbyist/tinkering/esoteric prototyping to producing real useful parts. I'm looking forward to DMLS tech making its way to desktop machines although I'm not sure I'd want Titanium Chloride in my home... 



natzoo said:


> And to give people some perspective. I only started printing frame components 6 months ago as a hobby. Imagine if we could all get along and work together, where would we be in 5 years?


Such a dream! imo it's both powerful and vulnerable to share your process and results with others. I hope the community can recognize this for the valuable resource it is. You've obviously put a lot of time into writing this all up and I know I'll be referring back to this thread years from now.


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## shirk (Mar 24, 2004)

natzoo said:


> *UDH dropouts:*
> 
> 
> the rear end is more compliant


Do you have numbers to back to that up? 






Rob English: The myth of vertical compliance and stiffness


Multiple NAHBS Awards winner, Rob English, explained to the Outspoken Cyclist why vertical compliance and stiffness are commonly misunderstood or misused.




www.handbuiltbicyclenews.com





You're going to need to show some real data to back up that claim. It gets batted around over and over but nobody ever has any data to show.


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## shirk (Mar 24, 2004)

natzoo said:


> After all the expensive dust settled, I think 3D printing is the future of custom framebuilding. The only limiting factor is people’s CAD skills. Better fire up those Fusion360 tutorials. I think 3D printing is more accessible than most people realize.


In order to advance the game I'd like to see more info shared on the CAD info. Pretty things can be modeled in CAD, but without being able to test it most of us home gamers are in the dark. We can run some basic FEA in Fusion but to my knowledge there is no information out there for what numbers to test to. 

For example this info on Pole testing at EFBE is the first time I've seen testing force numbers shared. 



https://www.pinkbike.com/news/pole-voima-emtb-passes-efbe-tri-test.html



So someone with full CAD / FEA want to translate this into a digestible set of figures for setting up a crude FEA workflow to ensure that this access to inexpensive 3d printing can make some safe parts?


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## natzoo (Jan 21, 2009)

a_j_p said:


> I would be willing to invest some time and as needed some $$ to working on this together... I am nearing completion of an FS frame currently where the shock mount would have been a great candidate for a printed part - but I was honestly too intimidated with unknowns to try it and settled for long 4130 mounts and machined aluminum adapters... It would be nice to at least know/try more and collaboratively is always better for me.


I think a shock mount is a good candidate for printing. You could spread the force over a large area, and reinforce the downtube. Maybe even silver braze to reduce heat? (this is not my area of expertise). If you make a design and create a separate thread, I would be happy to consult/work on it together


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## a_j_p (May 19, 2019)

I will put together a thread about the bike I am building and the details for what I considered printing sometime this next week. In the past I have tended to only post after completion just to share, but I can swap that up a bit this time around I guess.

For now, I have already machined the mounts for this bike (haven't welded them on yet) and will proceed with them for this frame... It's a single pivot without a linkage so, pretty much exactly as you are describing, the shock at full compression puts a large bending moment on the down tube that is/can be reinforced through however the shock is mounted.

Although I'm using what I've already machined for this frame, I could start learning and solicit advice to come up with something for the next time around.


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## fuzz_muffin (Dec 24, 2017)

natzoo said:


> Totally agree. Before the thread got derailed, I purposefully did not mention anything about what modern geometry is. I think people should build and ride what they like. I actually spend way more time designing cable ports so they can be easily routed and noise-free, than obsessing about chainstay length.
> 
> The fundamental purpose of my designs is to *bring down the cost of custom framebuilding, *while maintaining or even improving functionality.
> ...


Great stuff, cheers. 
I may have missed it in all the drama, but are these components available to other builders? those dropouts look pretty slick.

Not so sure about the compliance claim though. I agree with shirk, never seen any evidence that supports compliance and vibration reduction claims.


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## natzoo (Jan 21, 2009)

Ben.land101 said:


> _All of the industries really pushing the boundaries of what can be done with it are still pretty quiet about it. Trade secrets, defense, NDA's and all that.
> We have to wait a few more years for the trickle down of technology to get to us.
> Or in other words, I just can't find anything academic about welding 3D printed metals. Maybe your Google-Fu is better than mine._


Some good points for sure. You raise a good question about expertise, and where it lies. This is my own personal experience: I was in academia for many years, now I work in "the industry". Both have their own biases. At the highest level, everyone is just trying to figure it out.

Academia has a novelty bias. You get recognition from proposing new things and only get to show your successes. Have I published papers that I thought were dumb ideas? Yup. And for every success, I probably failed ten times, and learned the most from the failures. But would anyone publish a paper on things that didn't work? Nope.

Industry has a different bias. It needs to make money and meet deadlines. That means pushing stuff out, even if it's not totally done yet. Have I shipped products that I knew needed more time? Yup. Have I made grave mistakes, and had to fix them later with software? Yup. If you ask any engineer, their designs are never done. They can always be better. But products have to ship. It's just part of the process, and that's a good thing. Even the "3D printing experts" get things wrong: see olympics. Not throwing any shade, I totally understand how that happens.

Point is, if there is no consensus on welding 3D printing metals, there might not actually be one. I'm pretty sure the big defense and aerospace companies have entire teams that have already found _their _best solution. But we are not designing jet engines, nor do we have access to their resources haha. There is probably a bicycle-specific welding solution, and I think its really cool that discussions like this will help answer these questions.



Ben.land101 said:


> _My biggest concern is how homogenous the 3DP part may or may not be. Any small voids (or contamination in the powder they used) _


It is in the fab's best interest to have a clean, pure, environment. The printing process is very sensitive, and they print in large batches. If there is contamination, it will be an expensive mistake. That being said, there is always contamination in every process.

Regarding voids, this is still an active concern of mine. Not really for welding, but in general. To be clear, we have not seen voids yet, but I have some process controls in place to mitigate the risk. Companies are working on solutions to this exact problem: (coincidentally named velo3D).



Ben.land101 said:


> _You mentioned it had a sintering heat treatment done after printing, which should help.
> Although I think (hope) that is the wrong terminology. Sintering implies the metal particles are just 'stuck' together, instead of being truly bonded into one solid piece.
> I suspect the post-print heat treatment is more of a normalizing or annealing step to get rid of any stresses from the printing process._


Correct. It is just normalizing and annealing, not sintering. I think this stems from the confusion over the different the printing process.

*Metal binder jet* printing glues the powder together, then the part is baked at high temps to sinter the metal. These parts are porus, because the glue takes up space and evaporates during sintering.

Most people are printing with *DLMS (Direct Laser Metal Sintering)* and *SLM (Selective Laser Melting)*. I think the two names are the root of a lot of people's confusion (including my own). I have looked into this in-depth, and _my_ conclusion is that they refer to the exact same process, the difference being a trademark battle. Regardless of the naming scheme, every printer is going to have different hardware (laser wavelengths, laser engine), different firmware (motor speeds, motor control), and different software (motor commands, support generation, etc..) driving the printing process. In the end, a laser beam lets metal together, but every printer is going to do it slightly differently. Just like there are different pulse, speeds, amps when welding.

If someone knows the difference between the two process, then I am all ears.

I will add, anecdotally, Nick has not had any issues welding the printed parts. There are also things that I design to make welding easier (and more reliable). For example:

I thicken the parts at the weld
I consider the torch angle and cup at every joint
I make every miter joint perpendicular


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## Ben.land101 (Dec 25, 2012)

natzoo said:


> Some good points for sure. You raise a good question about expertise, and where it lies. This is my own personal experience: I was in academia for many years, now I work in "the industry". Both have their own biases. At the highest level, everyone is just trying to figure it out.
> 
> Academia has a novelty bias. You get recognition from proposing new things and only get to show your successes. Have I published papers that I thought were dumb ideas? Yup. And for every success, I probably failed ten times, and learned the most from the failures. But would anyone publish a paper on things that didn't work? Nope.
> 
> ...


That's good stuff. Kind of funny, my personal experience pretty much revolves around "sure things" as in, very well established procedures, processes, etc. Like the AWS and ASME codes I'm in every day. They've been around for quite a while now and are true industry standards.

No doubt the new stuff just makes me uncomfortable without the work of smarter folk and years of experience to reference. Haha


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## Little_twin (Feb 23, 2016)

Ben.land101 said:


> That's good stuff. Kind of funny, my personal experience pretty much revolves around "sure things" as in, very well established procedures, processes, etc. Like the AWS and ASME codes I'm in every day. They've been around for quite a while now and are true industry standards.
> 
> No doubt the new stuff just makes me uncomfortable without the work of smarter folk and years of experience to reference. Haha


Every one of those codes and processes was a new idea at some point. 

This train just showed up, it may not be the smoothest ride but tickets are cheap right now. 

It’s also important to remember one thing, the assembled structure of a part plays a big role in its failure mode. Plenty of bikes are built today with a complete disregard for that. 


Sent from my iPhone using Tapatalk


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## life behind bars (May 24, 2014)

Personalities and interacting with them is complex and can be a minefield at times, I simply ask that we all do our best to minimize the casualties that come with a discussion that can be at times passionate. Before dismissing someones opinions because the delivery strikes you as wrong please try to see the message being delivered, you may glean some wisdom in the process. Remember, not everyone excels in the social graces but still may offer something of value to the the conversation. Or, you can simply ignore the static that offends and move on but please remain civil. Many thanks.


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## natzoo (Jan 21, 2009)

shirk said:


> In order to advance the game I'd like to see more info shared on the CAD info. Pretty things can be modeled in CAD, but without being able to test it most of us home gamers are in the dark. We can run some basic FEA in Fusion but to my knowledge there is no information out there for what numbers to test to.
> 
> For example this info on Pole testing at EFBE is the first time I've seen testing force numbers shared.
> 
> ...


Alright, last response, then I need to find a therapist to help unpack this thread for me.

That Pole testing link is great. Thanks for sharing it. And I think you are right, it is the first time I have seen someone publish real numbers.

I think what you are getting at is the robustness of printed parts. It's the right question to ask, and that is my number one concern as well. I'll get that to the end.

But first, I want to make some comments on FEA and lab testing. That is on my ever-growing list of things to do, but it's not near the top (maybe someone else can take on this challenge). All tools have their limitations, and I think it is important to put things in perspective.

FEA is only as good as:

your model
the inputs to your model










FEA on additive materials is still an active research topic. Even if we did have a simulation, we would still need to validate the model and input parameters with real-world testing. A model without a way to validate it is just a model. In my opinion, FEA at this stage of design is good for sanity checks and to visualize stress concentrations.

Lab testing also has massive blind spots. Take for example, Pole. Why are they being so public and transparent about their testing? It is because their Stamina frames failed, and they were jerks about it. I am pretty sure the Stamina passed ASTM testing. There were probably colorful FEA pictures too. And yet it still broke. Why? Because tests are only as good as the parameters of your experiment, and the real world parameters are extremly difficult to know. I don't fault them for making a bike that broke: new designs are always risky, and I applaud them for trying. I fault them for being jerks about it.

another MTBR classic: Catastrophic failure Pole Stamina 180mm



















Back to the original question about the strength of 3D printed parts in frames. Here are a few things to consider, so people can make up their own minds robust the process is:

The printed parts are designed with significantly thicker wall thickness. Stiffer parts => less strain => longer fatigue life
My yokes don't require dimpling chainstays which create stress risers and make the material brittle
On average, frames with additive joints have better alignment. Less cold setting is needed. Again, cold work makes metals brittle.
The designs make welding easier. Every joint is perpendicular, designed to minimize awkward torch angles. Easier welding => more consistent => less heat
The mechanical testing on printed samples gives me confidence in my designs. Why don't I show this? Because the testing was not free.
I think most importantly, all the structural components I print are supported by more than one tube. I do not print anything that is cantilevered: stems, handlebars, forks, (I'm still debating headtubes). Not only are the stresses significantly higher, but also the failure mode is catastrophic.

These are the active questions I have about the robustness of additive parts on bikes:

Do additive materials experience fatigue the same way as bulk materials?
What is the probability of a gross defect during the printing process, and what does that look like?
What is the variation of mechanical properties from printer to printer and batch to batch?
I think these problems will be solved in the next 5 years, but until then, I just crank up the wall thicknesses on my parts. It increases the price, but it's an insurance policy until these questions are answered. The tried and true: solve problems by throwing money at it.

Anyways, it was a great question, and I am glad you asked it. It made me think more about my process and review my notes. This is just my perspective from the last 6 months of printing pipe fittings. I encourage people to come to their own conclusions.

I spend a lot of time writing these responses in the hopes that the quiet lurkers out there can get some inspiration to try something cool. That was me 10 years ago. Anyways, hope that was helpful.


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## speedygz (May 12, 2020)

natzoo said:


> Alright, last response, then I need to find a therapist to help unpack this thread for me.
> 
> That Pole testing link is great. Thanks for sharing it. And I think you are right, it is the first time I have seen someone publish real numbers.
> 
> ...


Coolest thread on the forum. I'm too old to get into this properly, only been into 3D CAD modelling a couple of years now, - when I went to school personal computers were in their infancy, like 2 computers for a school of 600+ students, but I can see the near unlimited potential for it when combined with additive manufacturing. Like someone else said -may have been you even, it's only going to get better & cheaper. Look at Laser cutting for example. Only a few years back it was crazy expensive, only used on exotica & used as a last resort. Now it's used everywhere, often cheaper than drilling holes in flat bar with a drill bit for example. I think that's brilliant, & I feel I've been lucky to see it progress. Even CAD itself. It wasn't that many years ago you need a supercomputer to run it, & million dollar programs. Now a lot of it will run on your smartphone. Absolutely astounding. I think it's fantastic to see this tech being accessible to normal, everyday people, & those people finding different uses for it. Even better, those people sharing their stories & learning curves on the interwebz, where anyone can see & learn from. Hats off dude, keep it up. I'll be watching & reading for sure


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## OldSchoolMBer (May 25, 2013)

natzoo said:


> FEA is only as good as:
> 
> your model
> the inputs to your model
> FEA on additive materials is still an active research topic. Even if we did have a simulation, we would still need to validate the model and input parameters with real-world testing. A model without a way to validate it is just a model. In my opinion, FEA at this stage of design is good for sanity checks and to visualize stress concentrations.


Thats the way I see it too. I think with additive materials the emphasis should be on the testing end. With solid predictable numbers the models become more accurate.

Somebody mentioned compliance and vibration reduction, if somebody was inclined to do so, they could throw some strain gauges on the frame


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## dr.welby (Jan 6, 2004)

natzoo said:


> The printed parts are designed with significantly thicker wall thickness. Stiffer parts => less strain => longer fatigue life


This line of thinking, that fatigue life is based on preventing the part from flexing, isn't really correct. Since stress and strain are related a reduction in one will also reduce the other making them almost interchangeable. But for low stress, long cycle life elastic loading, the focus is really about reducing stress, especially localized stress risers. Which is something a 3d printed part, at least geometrically, can potentially do well.


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## natzoo (Jan 21, 2009)

dr.welby said:


> This line of thinking, that fatigue life is based on preventing the part from flexing, isn't really correct. Since stress and strain are related a reduction in one will also reduce the other making them almost interchangeable. But for low stress, long cycle life elastic loading, the focus is really about reducing stress, especially localized stress risers. Which is something a 3d printed part, at least geometrically, can potentially do well.


Thanks, you are correct. I was looking at it too one-dimensionally.


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## dr.welby (Jan 6, 2004)

Have you considered using a silver solder preload and induction brazing your joints?


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## natzoo (Jan 21, 2009)

dr.welby said:


> Have you considered using a silver solder preload and induction brazing your joints?












No, but that's a really crazy idea for mass production.

I have considered printing channels to pre-load wire, but I am not an expert in brazing, so I didn't want to play with fire (literally)


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## dr.welby (Jan 6, 2004)

Yeah, I haven't priced the equipment out but I wonder what the breakeven is on a small induction heater that does one joint at a time. How amazing would it be to press a button and have the joint done in seconds, with minimal heat distortion, and no weld sequencing?


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## Little_twin (Feb 23, 2016)

dr.welby said:


> Yeah, I haven't priced the equipment out but I wonder what the breakeven is on a small induction heater that does one joint at a time. How amazing would it be to press a button and have the joint done in seconds, with minimal heat distortion, and no weld sequencing?


I would think the time saved would be nearly even. As is tig welding these isn’t a very time consuming process as they are a dropout/chainstay/yoke subassembly………..at least it seems………


Sent from my iPhone using Tapatalk


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## dr.welby (Jan 6, 2004)

Little_twin said:


> I would think the time saved would be nearly even. As is tig welding these isn’t a very time consuming process as they are a dropout/chainstay/yoke subassembly………..at least it seems………
> 
> 
> Sent from my iPhone using Tapatalk


It’s not so much the time savings as the skills and focus savings


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## Little_twin (Feb 23, 2016)

dr.welby said:


> It’s not so much the time savings as the skills and focus savings


I guess it depends on what you’re starting with. I personally can’t stand brazing. I’d much rather tig weld everything. Bottle bosses and other small braze on’s are my least favorite part of every frame build. 


Sent from my iPhone using Tapatalk


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## dr.welby (Jan 6, 2004)

Little_twin said:


> I guess it depends on what you’re starting with. I personally can’t stand brazing. I’d much rather tig weld everything. Bottle bosses and other small braze on’s are my least favorite part of every frame build.


But you're not doing anything, the silver rod is preloaded in the joint and the induction heater does the heating for you.


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## Little_twin (Feb 23, 2016)

dr.welby said:


> But you're not doing anything, the silver rod is preloaded in the joint and the induction heater does the heating for you.


I get it, drink coffee while the work is done for you. It’s just such a small piece that still requires a very manual front and back end. 

I personally feel that there are better ways to “automate” the process, having something heat the metal for me isn’t enough of a benefit. This is just my opinion based on what I do and my skill set. 


Sent from my iPhone using Tapatalk


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## dr.welby (Jan 6, 2004)

Little_twin said:


> I get it, drink coffee while the work is done for you.


No, flux and and load the next assembly.

This is all a just a "what if", you don't actually have to devote three posts to being skeptical about it.


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## Little_twin (Feb 23, 2016)

dr.welby said:


> No, flux and and load the next assembly.
> 
> This is all a just a "what if", you don't actually have to devote three posts to being skeptical about it.


Is t that what forums and the internet are for? Disagreeing? Besides, I’m fine playing the “what if” game as long as it can remain civil. 

I also know that for me personally, the idea of cleaning flux off of a brazed part is what nightmares are made of. 


Sent from my iPhone using Tapatalk


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## letsgethurt (May 7, 2020)

Wouldn't you rather use a shield gas to get rid of using flux entirely, like with tig brazing, or at least program your induction rig to not burn the flux?


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## Darth Lefty (Sep 29, 2014)

natzoo said:


> What is the variation of mechanical properties from printer to printer and batch to batch?


You probably don't have an instron but you can surely print a dogbone in some dead space in your batch of pieces and find a way to break it. At each orientation, even


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## Ben.land101 (Dec 25, 2012)

Darth Lefty said:


> You probably don't have an instron but you can surely print a dogbone in some dead space in your batch of pieces and find a way to break it. At each orientation, even


Along those same lines, it would be fun to do some testing on samples. Both as-printed and welded.

I test weld samples all the time. Tensile, Charpy V-Notch and a Macroetch would be what I would be interested in seeing.
At least comparing to 'regular' 316L could be informative.

Natzoo, if you ever want to do some of those tests hit me up. I can probably sneak a few samples in if you know what I mean.


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## natzoo (Jan 21, 2009)

Ben.land101 said:


> I test weld samples all the time. Tensile, Charpy V-Notch and a Macroetch would be what I would be interested in seeing.
> At least comparing to 'regular' 316L could be informative.
> 
> Natzoo, if you ever want to do some of those tests hit me up. I can probably sneak a few samples in if you know what I mean.


Awesome! I'll print some tensile samples next time, and we can dump the results onto this thread. There were still some question marks with the previous testing I did, but it was too expensive to keep chasing.



Darth Lefty said:


> Surely print a dogbone in some dead space in your batch of pieces and find a way to break it. At each orientation, even


This is what I have tried:










I'm pretty sure/hope the big companies are already doing this (bastion):










It makes sense for Bastion, because they are printing cantilevered parts (fork crowns and stems), and because they are making a* $14,000USD frameset*. I'm not trying to use 3D printing that way, I am trying to be the Harbor Freight of framebuilding.

For what I have access to, I was comparing the cost of test vs printing, it was cheaper to just jack up the wall thickness than to test every batch. I also believe that style of testing is good at detecting systemic printing issues, but those typically are obvious and cause the entire print to fail. DSLM printing is a very serial process, and I think it's very possible a part has a flaw, but the adjacent test dogbone is still good.

Also, to be clear, I'm not a test/materials/manufacturing engineer. It is not my area of expertise. There is definitely more work here that should be done.

RE: Induction


dr.welby said:


> It’s not so much the time savings as the skills and focus savings


Totally agree. I think this is a really good idea. Imagine if your frame fixture had built-in induction coils at every joint, and you just set up your fixture, push a button, and your frame is done. Then even I could weld a frame


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## OldSchoolMBer (May 25, 2013)

The induction version of furnace brazing


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## dr.welby (Jan 6, 2004)

The other hands-off brazing method I think Bridgestone Japan was using is dip brazing - basically you drop your whole frame with preloaded lugs into a vat of hot molten flux, which wicks right into your joints as the whole frame comes up to temperature and melts the preloads. Probably a little harder to DIY, but fun to think about frame fondue.


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## compositepro (Jun 21, 2007)

dr.welby said:


> I see your two welds and raise you to 4 welds and 28 stress risers
> 
> View attachment 1963925


WTF WAS THAT?


dr.welby said:


> Yeah, I haven't priced the equipment out but I wonder what the breakeven is on a small induction heater that does one joint at a time. How amazing would it be to press a button and have the joint done in seconds, with minimal heat distortion, and no weld sequencing?


500$ You can even buy the solid state ones cheap ,


cassieno said:


> My last comment on this and then I will stop engaging with you because I literally cannot stand your smug opinion and useless attitude that you bring to any online discussion - Doesn't solve a problem that you know. Because you have never tried.
> 
> You spend forever analyzing your designs and building for yourself. Then you spend the rest of your time telling everyone else how worthless they are because they are not you.
> 
> ...


beautiful


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## bentmettle (Jul 2, 2018)

OldSchoolMBer said:


> Somebody mentioned compliance and vibration reduction, if somebody was inclined to do so, they could throw some strain gauges on the frame


Somehow I got older and didn't realize it, but in a previous job we used strain gauges to measure stress wave propagation speed. Basically when you impact some material, the stress doesn't instantaneously appear in the part, and instead travels through the material at some measurable speed.

If a person were to put gages in two different spots, say a seatstay, you'd see the stress signals be out of phase with each other for a specific impact. The stay is pretty short compared to the rock drilling rods we were working with, but you do need to be aware there will be some phase delay if a person were trying to do vibration studies using strain gages.

I built a test stand (very simple a frame) for a friend in grad school doing air bag research. He instrumented it to measure strain while igniting gas canisters and you could see the high frequency ringing in the stand after the initial impulse of the canister igniting. That all had to be removed via low pass filtering - I can't remember if he did it electrically on the signal input side, or cleaned it up in software.

These are basically all reason I presume most of the time they use accelerometers to quantify vibration. They measure the signal of interest without all the other issues.

I had a master's degree in mechanical engineering and had never even heard anyone talk about stress waves before that job, so it was a serious surprise me _laugh_


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## dr.welby (Jan 6, 2004)

I got a demo of a device that was an accelerometer that could be clamped to your structure, and a hammer with an accelerometer, both connected to a computer peripheral (this was before we had computers in our pockets). Then you would tap around your structure and the device would do Fast Fourier Transform to tell you all about how different frequencies were transmitted and damped.


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## compositepro (Jun 21, 2007)

"Somehow I got older and didn't realize it, but in a previous job we used strain gauges to measure stress wave propagation speed. Basically when you impact some material, the stress doesn't instantaneously appear in the part, and instead travels through the material at some measurable speed.

If a person were to put gages in two different spots, say a seatstay, you'd see the stress signals be out of phase with each other for a specific impact. The stay is pretty short compared to the rock drilling rods we were working with, but you do need to be aware there will be some phase delay if a person were trying to do vibration studies using strain gages.

I built a test stand (very simple a frame) for a friend in grad school doing air bag research. He instrumented it to measure strain while igniting gas canisters and you could see the high frequency ringing in the stand after the initial impulse of the canister igniting. That all had to be removed via low pass filtering - I can't remember if he did it electrically on the signal input side, or cleaned it up in software.

These are basically all reason I presume most of the time they use accelerometers to quantify vibration. They measure the signal of interest without all the other issues.

I had a master's degree in mechanical engineering and had never even heard anyone talk about stress waves before that job, so it was a serious surprise me _laugh_ "

In the early days of designing health monitoring and doing ballistics for composites we borrowed something similar from the deep hole drilling mob , obviously down the line there were embedded solutions (on the 777, AH64s) works the same for effectively figuring out dampening in seatstays (flax was the main modifying element)


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## bentmettle (Jul 2, 2018)

Can we seriously not delete posts? Good gravy.


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## shirk (Mar 24, 2004)

Again on the steel frames and rear end vertical compliance, has anyone ever backed up their claims with shown data?


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## compositepro (Jun 21, 2007)

shirk said:


> Again on the steel frames and rear end vertical compliance, has anyone ever backed up their claims with shown data?


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## Ben.land101 (Dec 25, 2012)

shirk said:


> Again on the steel frames and rear end vertical compliance, has anyone ever backed up their claims with shown data?


I once watched a youtube review where the guy said the frame was super compliant. 
lol

Kidding aside, I would like to see the same thing, if anyone has ever quantified 'compliance' in a bike frame, then compared it to others.


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## xy9ine (Feb 2, 2005)

shirk said:


> Again on the steel frames and rear end vertical compliance, has anyone ever backed up their claims with shown data?


steel is real, dammit! that's all you have to know. 

good question. i imagine actual differences in frame deflection are fairly insignificant relative to the other squishier / flexier components of the system. _subscribed_


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## bentmettle (Jul 2, 2018)

xy9ine said:


> steel is real, dammit! that's all you have to know.
> 
> good question. i imagine actual differences in frame deflection are fairly insignificant relative to the other squishier / flexier components of the system. _subscribed_


And with the relative lack of constraints (you essentially have several degrees of freedom that prevent significant load creation) - at some point I'd think the higher frequency content will be dominate what's felt by the rider.


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## eva_k (Apr 25, 2021)

I do a lot of very precise distance measurement for my day job and use Keyence laser sensors a ton. I wonder if something like that paired with a rigidly mounted target would be useful for measuring tube deflection. Something like the IL-600 has a repeatability of 0.05mm over 600mm which I'm guessing would be enough to observe tube flex at least in the <100Hz domain. Ideally you'd want 2D measurement but 1D would be a starting place.


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## natzoo (Jan 21, 2009)

Anecdotally, with A-B testing between two frames, one with thinner SS's and swapping the same wheelset, it's very noticeable to me. I went in equally as skeptical as everyone else here, believing that there is no way you could feel it with such a soft tire, but I proved myself wrong.

This is a great article written by James Huang with quite a few quotes from actual engineers, not internet ones like us: https://cyclingtips.com/2018/04/jra-with-the-angry-asian-does-frame-compliance-still-matter/

I think the important takeaway is that under large compressions, the nonlinear nature of the air spring makes the tire much stiffer, equaling that of the frame stiffness. Thus, the frame stiffness contributes just as much as the tire when it matters the most. I am sure this matches up with a lot of people's own experiences: some frames just take the sting off big hits.

With regards to qualitative/lab data, it would be amazing to have, but I don't think it is necessary to drive frame design.

Ultimately, a frame's stiffness is some linear combination of each individual tube stiffness
A tube's stiffness is a quartic (4th power) relationship to its diameter, so small changes in diameter have a massive impact on stiffness
A 14.3mm seatstay is ~33% less stiff than a 16mm seatstay
I think the question of _*exactly*_ how much the SS stiffness contributes to the overall stiffness is open to debate, but I don't think you can argue that it does not make a difference. That would be against the laws of physics.

Let's say I spent 1 month and $5k testing and found that frame A was 300N/mm less stiff than frame B, that number alone would mean nothing to me. I would still need to ride the bikes to see if that translates to a real-world benefit. As I said in an earlier post, testing has its own blind spots. Quantitative data is great, but not always useful.

If that argument does not convince you, then maybe colorful pictures will. 

*16mm SS: *

Load: 1000N down at the BB
BB displacement: .13mm
Vertical BB stiffness: 7500N/mm
Note: the displacements are shown magnified









*14.3mm SS: *

Load: 1000N down at the BB
BB displacement: .15mm
Vertical BB stiffness: 6500N/mm









*To be clear, I don't believe these numbers mean anything.* However, they do show some trends:

the seat stays experience the most strain/displacement in this load case
the frame with 14.3mm SS is 13% less stiff than the 16mm. (I think this is totally believable, considering the tubes themselves are 33% less stiff)
There are plenty of holes to poke in this quick study, but I think it's pretty clear that the seat stays are the driver of vertical stiffness/compliance. In retrospect, I think this makes a lot of sense: the SS is the skinniest tube, loaded in compression, with a bending moment built-in.

Side note: if you are wondering why these results are much higher than the numbers in the cycling tips article, they measured the stiffness with the force at the seat. I simulated the force being applied to the BB (more relevant to MTB).

*TLDR:*

anecdotally, I can feel the difference between different seat stays
under large compressions, the tire is very stiff, so frame stiffness starts contributing 
according to some quick simulations:
the seat stays are the main driver of vertical compliance

qualitative data is nice to have but not definitive


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## compositepro (Jun 21, 2007)

Can someone tell me the difference between an actual engineer and someone with a qualification in a mechanical engineering discipline is.


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## *OneSpeed* (Oct 18, 2013)

I don't need data from a lab, and I don't need an engineer to present load graphics. I've owned and ridden enough frames that the difference is clear as day. 

On the subject of "vertical compliance", I don't care if a steel frame actually deflects 3mm or 4mm, and I don't care how that compares to an aluminum frame or a carbon frame. I can feel the difference when riding, that's where it counts.


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## Ben.land101 (Dec 25, 2012)

*OneSpeed* said:


> I don't need data from a lab, and I don't need an engineer to present load graphics. I've owned and ridden enough frames that the difference is clear as day.


Were _all_ of the variables accounted for each bike you have ridden? That is the big question that nobody has been able to answer. Otherwise we start pointing our fingers at stuff without anything to back it up. 
It's like the old arguments about 27.5 vs. 29ers (RIP 26ers). Someone upgrades to *a totally different bike* with a different wheel size, and says "wow, this rides so much better/worse! it must be the wheel size!" while completely ignoring every other variable. 

I think we all believe "steel is real" anecdotally (myself included) But if we cannot quantify what makes a bike more compliant than another, then we cannot design around it.


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## natzoo (Jan 21, 2009)

compositepro said:


> Can someone tell me the difference between an actual engineer and someone with a qualification in a mechanical engineering discipline is.


Sorry, that statement was a self deprecating joke. I was referring to the fact that those guy and girls get paid to “engineer” frames. They know way more than me. I’m just poking around in CAD.


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## natzoo (Jan 21, 2009)

After looking at the sims with a fresh eye, I realized that the mode with which the seat stays are flexing can be prevented by a SS bridge:









*14.3mm SS w/ Bridge:*

Load: 1000N down at the BB
BB displacement: .099mm
Vertical BB stiffness: *10,100 N/mm*

Adding the seat stay brace prevents the seat stays from bowing out, and significantly stiffens up the bottom vertical bracket deflection

The brace also eliminates a stress riser at the seattube:






















Again, I don't trust any of the absolute numbers here, but I do believe in the trends that are being shown by the FEA. They align with both my gut feelings and my qualitative experiences


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## eMcK (Aug 22, 2007)

Ben.land101 said:


> Were _all_ of the variables accounted for each bike you have ridden? That is the big question that nobody has been able to answer. Otherwise we start pointing our fingers at stuff without anything to back it up.
> It's like the old arguments about 27.5 vs. 29ers (RIP 26ers). Someone upgrades to *a totally different bike* with a different wheel size, and says "wow, this rides so much better/worse! it must be the wheel size!" while completely ignoring every other variable.
> 
> I think we all believe "steel is real" anecdotally (myself included) But if we cannot quantify what makes a bike more compliant than another, then we cannot design around it.


ALL the variables? That seems like an impossible high bar to set.

I've been watching a lot of car shows lately (Dirt Every Day, Road Kill, etc), and it is particularly interesting to watch someone like Dave Chapelle(not the comedian) build off-road trucks. No computers, just a lot of cardboard templates and years of fabrication experience. Very seat of the pants, but very effective. I see nothing wrong with taking a similar approach to framebuilding, assuming a builder is erring on the side of overbuilding things.



I'm also very much a results > process person and find that having enough data to move forward is more important than having all the data, FWIW.


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## fuzz_muffin (Dec 24, 2017)

I do think vertical compliance is a good thing. My current bike has about 180mm of it. However, I've yet to measure it properly.


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## speedygz (May 12, 2020)

*OneSpeed* said:


> *I don't need data from a lab, and I don't need an engineer to present load graphics. I've owned and ridden enough frames that the difference is clear as day.*
> 
> On the subject of "vertical compliance", I don't care if a steel frame actually deflects 3mm or 4mm, and I don't care how that compares to an aluminum frame or a carbon frame. I can feel the difference when riding, that's where it counts.


You do -you just don't realise it. How do you think the frame/bike builders arrived at the designs you like the feel of? Back in the olden days, it was years of design, prototyping, building, testing, modifying, rinse and repeat. Now, with CAD modeling & FEA,, you can get a very good idea on how your frame will behave, and more importantly, when you want to change certain characteristics, you have a very good idea of where, & how much your design needs to change. 
What you're saying as as silly as saying "I don't need scientists & medical researchers, I just go to the Doctor & he gives me what I want to get better" Where do you think those medicines originated?


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## Ben.land101 (Dec 25, 2012)

speedygz said:


> You do -you just don't realise it. How do you think the frame/bike builders arrived at the designs you like the feel of? Back in the olden days, it was years of design, prototyping, building, testing, modifying, rinse and repeat. Now, with CAD modeling & FEA,, you can get a very good idea on how your frame will behave, and more importantly, when you want to change certain characteristics, you have a very good idea of where, & how much your design needs to change.
> What you're saying as as silly as saying "I don't need scientists & medical researchers, I just go to the Doctor & he gives me what I want to get better" Where do you think those medicines originated?


This is the correct answer. Kind of what I said earlier, but in different words.
The Rider / racer , i.e., consumer, does not care _how_ it works. They only care that it does work. It is up to the designer to determine why something works. That way we can actually design around it, and potentially use it to our advantage.
And the only way to figure out something as marginal as a steel frame flexing, is yes, to control ALL of the variables.
Otherwise we are just guessing, and going off of rumors.



fuzz_muffin said:


> I do think vertical compliance is a good thing. My current bike has about 180mm of it. However, I've yet to measure it properly.


This is also the other correct answer. lol


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