# Working with Bike CAD - Samples and a few Questions



## MMcG (Jul 7, 2003)

Bike CAD via Bikeforest is a really cool and nice resource and it can become a bit addicting once you get in there and start working with it.

I've saved a few of my "Samples" and figured I'd post them up as a sort of show and tell Bike CAD design Friday thing.

I have a few Questions for builders/Bike CAD experts.

What are some of the head tube and BB diameters that are "standard" for steel frames?

Also, what are standard tubing diamters say for the following:
1. XC race steel frame
2. All Mountain Steel Frame
3. Freeride Steel Frame

Also, Can anyone give tips/advice for the seatsay and chainstay portions of BikeCAD? Curved vs. straight etc. etc?

Anyway on with a few samples of my time spent with a few different designs:

29er Single Speed:









Geared 29er:









135mm Travel Trail Bike - think the HT angle is too slack?










And I finished up this one earlier today - went with a lot of white on it (didn't even realize you could pick colors for everything on the bike before) and it is based around an On One Inbred 29er rigid fork (470mm AC height with 47mm or offset) and is designed to be a single speed frame.










Whattya guys think?

Oh and also - does anyone know how I can save my BikeCAD images as larger sized jpegs?

Thanks.

Mark


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## Schmucker (Aug 23, 2007)

I think you missed the mark for the purpose of the On One fork. They designed it to work with their Inbred, which has a 72 degree HTA. I'm using it on a KM, also 72d, and it works great. It's to make a 29er be able to get through tight and twisty single track. You seem to have it setup with quite a bit of trail. G2 geometry is 51mm offset and 69.9d HTA which many consider to be a neutral steering setup.


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## MMcG (Jul 7, 2003)

Schmucker said:


> I think you missed the mark for the purpose of the On One fork. They designed it to work with their Inbred, which has a 72 degree HTA. I'm using it on a KM, also 72d, and it works great. It's to make a 29er be able to get through tight and twisty single track. You seem to have it setup with quite a bit of trail. G2 geometry is 51mm offset and 69.9d HTA which many consider to be a neutral steering setup.


So what is the trail figure on your Karate Monkey with that fork? And what would the trail figure be with a 1 degree slacker HT angle? It wouldn't change thing much would it?


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## toddre (Mar 1, 2004)

Slow day at work, huh??


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## MMcG (Jul 7, 2003)

I only did the last one this morning!


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## MMcG (Jul 7, 2003)

I did this one at lunch - based it around a Niner Rigid fork with their 490mm AC height and 40mm of offset:










And here is a second version with a little bit more offset (43mm) and slightly different angles:










So looking at the two - the 3.19 and 3.2 figures (are those the trail numbers?) - in theory both of these bikes should have similar "front end" handling characteristics right??

And here is Version 3.0 featuring a 72/72 and a 470mm AC fork with 47mm of offset (On One)










This Version would be the "quickest" yes?


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## SSdaveo (Nov 10, 2008)

This is my 26". The fork is a beefed up version of the Vicious 413.









How do I fix this?


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## pvd (Jan 4, 2006)

S-bend and double check all your numbers.


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## SSdaveo (Nov 10, 2008)

S-bend must come with the paid version.


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## pvd (Jan 4, 2006)

Nope. BikeCad sucks for bends. Get good at cad for best quality.


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## Schmitty (Sep 7, 2008)

To answer the op's questions on 'standard diameters' I don't think there are any. At best, for an xc race frame you could argue 1.125 st/tt and 1.25 dt (I would do all 1.25). Of course, it could be all kinds of variations. All Mountain and Freeride, forget about trying to nail it down.


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## jmoote (Aug 31, 2007)

I don't know how you guys can do frame drawings in inches. I work in all different units all the time, but for bikes all the geometry numbers I use are in milimetres.


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## MMcG (Jul 7, 2003)

I guess I'm just old school! LOL - that and I sucked at math in school, especially metric conversion stuff.


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## SSdaveo (Nov 10, 2008)

Not that I build frames, but I can visualize 25" better than 635mm. If I were to build a frame, or design one to be built, it would be different.


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## pvd (Jan 4, 2006)

jmoote said:


> I don't know how you guys can do frame drawings in inches. I work in all different units all the time, but for bikes all the geometry numbers I use are in milimetres.


A consumer may have this opinion, but once you start honest fabrication of both frames and tooling things change. The world isn't perfect and to get results we work within it. I use mixed dimentions all the time when designing frames. Sometimes imperial trumps metric, sometimes it's the other way around.

Just try bringing a job to a machine shop dimentioned entirely in metric units. They are going to be really happy with you.

I love metric. It rules. It's better, but I like getting results even more.


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## SSdaveo (Nov 10, 2008)

pvd said:


> S-bend and double check all your numbers.


Something tells me an S-bend isn't the only answer. Both of my bikes have single bend Cstays. I think it's just that the program has only one crank for every bike.


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## jmoote (Aug 31, 2007)

I'm quite familiar with the workings of a machine shop and as stated will work in whatever units are necessary for the job. All I was saying is that for nominal dimensions of a bike frame I don't see a point in using inches. It seems like a mtb idea to give a frame a "size" in inches, but on bikes of all types geometry charts are most often found in metric.


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## MichauxYeti (Nov 10, 2005)

Double check your Q-factor dimension. I believe most road cranks are about 140mm whereas mountain cranks are closer to 170mm.


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## pvd (Jan 4, 2006)

jmoote said:


> It seems like a mtb idea to give a frame a "size" in inches, but on bikes of all types geometry charts are most often found in metric.


Who uses charts to design a frame? I use drawings.

I'll bet that if you take a closer look at all those metric numbers you will see that they are just converted nominal imperial numbers. If you take a Japanese sportbike engine apart and start measuring parts, you'll be amazed at how many 'metric' components are in fact imperial or bastards.


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## SSdaveo (Nov 10, 2008)

MichauxYeti said:


> Double check your Q-factor dimension. I believe most road cranks are about 140mm whereas mountain cranks are closer to 170mm.


Thanks! You would think that choosing MTB would set that for you, but....


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## MMcG (Jul 7, 2003)

Here's a Trail Bike I did via BikeCAD yesterday based around a Manitou Nixon Comp fork - It is nice that you can plug in suspension fork AC height and offset into the program.

It would be cool if they added a 650b wheelsize option to the free software in addition to their other wheelsize options.

What do you guys think of this one. It takes inspiration from the likes of the Chromag frames, the Chameleon, the Sinister Ridge, the Evil Sovereign, and a little bit of what I liked from my old Surly Instigator:










A couple of questions.

1. If I were to go to a slightly longer fork - the wheelbase would get longer and also - the effective top tube would decrease right?

2. Is the head tube tall enough for that much travel if properly reinforced/gusseted? I wanted to try and keep the front end a little lower to prevent against the loop out effect on short but steep climbs.


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## MichauxYeti (Nov 10, 2005)

The free version does allow you to do a custom wheel size.


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## brant (Jan 6, 2004)

MMcG said:


> 1. If I were to go to a slightly longer fork - the wheelbase would get longer and also - the effective top tube would decrease right?


Press the padlock button and change the fork. It'll show you what happens.



MMcG said:


> 2. Is the head tube tall enough for that much travel if properly reinforced/gusseted? I wanted to try and keep the front end a little lower to prevent against the loop out effect on short but steep climbs.


Loop out effect mostly to do with chainstay length, BB height and seat angle in my opinion. Lengthening stays, steepening seat angle, and dropping BB will diminish this.


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## MMcG (Jul 7, 2003)

Thanks Brant - but I don't want to go any longer than that, so my other options are slightly steeper ST angle and a straight 12" bb height.

The idea was this was to be the basis for a 650b wheeled bike. But I couldn't plug that wheelsize into the free software. So it was just a start of something that will hopefully evolve a bit.


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## tozovr (Jul 26, 2006)

MMcG said:


> Thanks Brant - but I don't want to go any longer than that, so my other options are slightly steeper ST angle and a straight 12" bb height.
> 
> The idea was this was to be the basis for a 650b wheeled bike. But I couldn't plug that wheelsize into the free software. So it was just a start of something that will hopefully evolve a bit.


Do not obsess on your CS length.

here's an example...So many folks seem to think we designed the Simon Bar around a sub 17" CS. We didn't. We designed the bike around a feel and an ethos. Everything is dependent on another. The Simon bar just worked out that you could run a 16.85 CS length...in fact, the bikes sweetspot is at 17.25". 279 people on the 29er forum would toss their cookies at that number...unless they rode the bike. FTW knows his sh1t.

Same thing happene3d when we designed the new 29er fully. You were tweakin about the CS length, but not seeing the big picture. Sure, we could drop the CS length to 17.3, but it would compromise the bike holistically.

Don't obsess over the CS length...you've ridden a bunch of these 26" bikes...compare and contrast them and talk to Ted again. Think about what bikes were just "nice" and what bikes were magic.


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## MMcG (Jul 7, 2003)

Not obsessing RJ - just asking for input from guys who've designed and built is all.

I agree 17.25 is pretty sweet for a 29er - that's where the Monkey Butt is too and it ride great.

I'm still not a big fan of those long chainstayed 29er fullies though. Maybe you can prove me wrong this spring though.


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## tozovr (Jul 26, 2006)

MMcG said:


> Not obsessing RJ - just asking for input from guys who've designed and built is all.
> 
> I agree 17.25 is pretty sweet for a 29er - that's where the Monkey Butt is too and it ride great.
> 
> I'm still not a big fan of those long chainstayed 29er fullies though. Maybe you can prove me wrong this spring though.


17.7 isn't long LOL


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## pvd (Jan 4, 2006)

17.7 is totally huge. What are you folks talking about? CS length and wheel diameter are two totally differerent performance parameters.


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## tozovr (Jul 26, 2006)

pvd said:


> 17.7 is totally huge. What are you folks talking about? CS length and wheel diameter are two totally differerent performance parameters.


On a 26er it's huge. What are you talking about? We're talking about something entirely different.


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## pvd (Jan 4, 2006)

The effects of chainstay length have nothing to do with wheel size. A 16" stay is different from a 17" stay in exactly the same way no matter the wheel size. It's a radius. The wheel has nothing to do with it other than finding a way to squeeze it in.


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## tozovr (Jul 26, 2006)

pvd said:


> The effects of chainstay length have nothing to do with wheel size. A 16" stay is different from a 17" stay in exactly the same way no matter the wheel size. It's a radius. The wheel has nothing to do with it other than finding a way to squeeze it in.


Right-o then.. Have fun with your 29er with 15" Chainstays LOL.


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## MMcG (Jul 7, 2003)

tozovr said:


> 17.7 isn't long LOL


Like I said - perhaps you can prove me wrong with the Sinister fully.


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## DWF (Jan 12, 2004)

tozovr said:


> Right-o then.. Have fun with your 29er with 15" Chainstays LOL.


'cept, IMHO, he's right. Chain stay length doesn't care what size your tire is, the load path is always perpendicular from the ground to the axle center regardless of tire radius. Design should be based on front/rear weight bias so what works on a 26" inch wheel will work the same on a 29" wheel. Tire clearance (seat tube, chainrings, front D, etc.) is a whole other issue. Meeting the requirements of both is the challenge and it seems that too often the compromise leans towards excessive chain stay length.


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## tozovr (Jul 26, 2006)

DWF said:


> 'cept, IMHO, he's right. Chain stay length doesn't care what size your tire is, the load path is always perpendicular from the ground to the axle center regardless of tire radius. Design should be based on front/rear weight bias so what works on a 26" inch wheel will work the same on a 29" wheel. Tire clearance (seat tube, chainrings, front D, etc.) is a whole other issue. Meeting the requirements of both is the challenge and it seems that too often the compromise leans towards excessive chain stay length.


I agree. In a perfect world we wouldn't need to worry about front derailleurs or fitting a 2.5" tire back there without using an 83mm BB etc. My point was that, all aspects of a design need to be harmonious and if you lean too far towards one particular number, it can be detrimental to the bike as a whole. MMcG and I discuss this daily and I think our friendship and familiarity with each other led my replies to appear rather vague to an outsider. Since I'm posting on a public forum, I should have prefaced my posts a bit.

RJ


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## MMcG (Jul 7, 2003)

MichauxYeti said:


> The free version does allow you to do a custom wheel size.


It does?

Can you email me to give me a rundown of how to do it?


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## pvd (Jan 4, 2006)

tozovr said:


> In a perfect world...


I gave up on the perfect world model a long time ago. We have what we have. You give here to get there. The better we understand what's going on in all it's complexity, the more powerful our tools become and the more specific our compromises can be.


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