# Frame Build Proposal Advice Wanted



## TrailMaker (Sep 16, 2007)

Like the Title Says;

I am looking for any and all constructive criticism/advice on this *Fatbike *proposal.
Any information seemingly omitted is likely because I haven't learned about that yet.
I have never done ANY of this before, and this represents my first attempt at a first attempt, so be kind... if at all possible.


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## dr.welby (Jan 6, 2004)

A 454 fork with 25.4 legs might be pushing it.

I like flexy bikes, but a 25.4 diameter top tube 27 inches long seems really undersized. I'm sure some will say the same about the down tube.

If your fatbike is for snow, you might want to consider that if you step off and posthole, you will want more standover clearance.


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## Walt (Jan 23, 2004)

*Quick thoughts*

First, I agree with everything Dr. Welby said.

Other thoughts -

-Is there very large front triangle intended to make lots of room for a frame bag or other stuff? IMO you don't need *that* much room - you can shorten the seat tube quite a bit.

-Seat tube extends WAY too far above the toptube - IMO you don't want more than about 50mm at most (I like 30-35mm) so that when you insert a seatpost, it will insert to all the way below the toptube/seat tube joint. Otherwise you risk having a post that seems like it's far enough in, but can break your frame in certain situations.

-The big challenge with fatbikes is tire clearance and chainline. You need to work on the rear end and figure out where you want to put everything (and how long your chainstays need to be) before you do the front end, IMO. Are you going to try to fit a BFL? 135 offset, 150, 170 rear end? Single, double, triple ring? Singlespeed-able?

-I think your trail number is kind of high. Why the 35mm (if I'm reading that right) fork offset? I'm not saying there is anything wrong with it, but 97mm trail seems excessive to me. If you look at the Pugs or the Fatback they're in the ~80mm range, depending a bit on the tire you run.

What material/process are you planning to use to build it?

-Walt


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## TrailMaker (Sep 16, 2007)

Hmmm....

First, thanks much Gentlemen. I should have added "any information that seems dumb and/or clueless" to my qualifier. I don't know nuthin from nuthin, my friends. I have been reading a lot (thanks for all the stickies, Mr. Walt), and PM-ing some (thanks for your interest, Jay!), but it's a lot to read let alone retain, and my brain aint that good. Not as good as the seat-o-my-pants in most cases!  Let's see if I can intelligently answer some of these questions;

I'm a large guy! 6'5"/240, 36" inseam/sleeve. 

- Basic geo; poached and sort of amalgamized from my XL RIP9 and the XL Mukluk. The numbers here are pretty close to those, for the most part, and what I am riding VERY comfortably now (GOOD LORD that 9'r is comfortable after years of Nose-Over-Axle!).

- Fork; Yeh, I guessed. That answer will fit a lot of this. I figured I'd probably buy a fork, since it is a pretty important piece (I don't know the specs for any of these to include them in my design). Tube sizes were all pretty much a guess, based on very little knowledge of what to use, let alone what is available.

- Trail; Yes, I agree. Most of what I have been able to poach has seemed to be around 3.5"/88.9mm. To the point that I already have the same basic layout with a 45mm offset.

- Seat tube; 3.5" unsupported tube in that layout. Always made me feel leery with 200+mm of seat post out in the breeze. Then again, I've never broken a post or seat tube either, so it is likely an unfounded fear. An ST in the 21-23" range might be a better idea, I guess (the XL Muk is 21").

- Material/process; Honestly, I sort of figured TIG welded straightwall 4130 just because it is "easy to deal with." What diameter & wall is very much beyond my experience at this point, but the KISS approach was leading me toward .035. Maybe larger D and thinner wall where possible, but ????

- Hub Size; My gut says 170mm centered will be where the standard lands, eventually. With the fun everyone is having on these, I thought I'd like an all'rounder. I like the idea of running fats or 2-9'r wheels depending on the season. 80-90mm rims with Nates is what I'm thinking now. 2x9, 12-36, I'd prefer X-type BY FAR. ??? I'd think this would come AFTER the basic layout decision.

Of course, it occurred to me that a Fattie might be a bit fraught for a first build too, spacing concerns being what they are. I have two projects in mind; Do I pick the one that I can use all the time (Fattie), or one that might be "easier" (a custom chopper/cruiser bike) that I have no real use for? In reality, any bike will be a big challenge, so might as well build a useful one?

Perhaps my short term goal should be to avoid becoming tedious.


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## Drew Diller (Jan 4, 2010)

Fattie rider here. Why do you want the bars below saddle level? Do you find the rear plunging into crust too much while having plenty of float up front?

My current bike has the same BB drop and crank length - pro is that it is mild mannered and corners well, con is that you have to pay attention to pedal scrapes. A Pug has less drop and more of a monster truck feel (go over whatever / pay more attention in the corners).

What fork are you going to use? Or building that too?

Don't get discouraged because it's a lot to absorb - I'm a newb on my fourth frame, each one is an eye opener.


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## TrailMaker (Sep 16, 2007)

Drew Diller said:


> Fattie rider here. Why do you want the bars below saddle level? Do you find the rear plunging into crust too much while having plenty of float up front?
> 
> My current bike has the same BB drop and crank length - pro is that it is mild mannered and corners well, con is that you have to pay attention to pedal scrapes. A Pug has less drop and more of a monster truck feel (go over whatever / pay more attention in the corners).
> 
> ...


Thanks, Man;

A guy showed up for a group ride last weekend on a Pugs. First ride on it, and he was having a BLAST. I was going nuts on Fat BEFORE that day. This was my first in-person sighting, and it's KILLING me now.

I don't want bar drop. That part is just sort of in there right now. I don't know nuthin from head tubes. Haven't factored in headsets yet either. REALLY early days... obviously. As that lays out, it is with about 0 stack height. I've never HAD a bike with less than 2" stack height, even with all the XLs. Even my XL RIP9 is stacked at about 2.5" right now!

I'd probably just buy a fork from Surly or such. I'd prefer something I can rely on there.

BB drop is right off the Muk specs. I like the Monster Truck thing, for sure, but not at the expense of stability. I might ease that drop a bit. Both my Heckler and my new RIP9 are peddle bashers, and I can't say I care for that much.

Right now I'm trying to work out as much as I can so I know WHAT to start acquiring. The first thing would be a clue.


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## TrailMaker (Sep 16, 2007)

Revision #3,454...


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## FTMN (May 10, 2010)

I'm about your size (a bit taller and slightly lighter), and I hope to build my first bike (a fat bike) later this year. I'm very interested to see what you come up with and how it turns out. Any updates along the way would be much appreciated!!!

What program/software are you using to draw your plans?


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## Meriwether (Jul 26, 2007)

I just finished my first fatbike and with only two rides on it i'm now an expert 

I find myself walking more than I thought, so as low a BB height is a good thing since you'll be jumping off a bunch and needing to dab even more...but not so low that you'll be brushing the pow with your toes, I'd go with 11.75" - 12" but not sure what BB drop that is on your design. 
I basically copied the Surly Neck Romancer geometry because it is more relaxed than the Pugsly and i think that is better for snow riding -- so a slacker HT like you have is right on IMO, but i'd go with a 72 deg ST angle. 
If you get a Surly fork (43mm offset) and stick with the 70deg HT angle, you'll get about 84mm of trail which is great...97 is insanity!) If you have more weight on the rear wheel it's good for climbing traction and you won't be washing out on the front wheel as much. Higher bars help this too.
Use 5mm shorter cranks than you usually do because it's better to spin that crank on snow (i'm sure you know this but I'll say it anyways since it's not obvious to some - i don't know how people use singlespeed fatbikes unless they ride only hardpack flat roads) and shorter cranks will help with a lower BB height too. 

Fatbikes are by nature...well, FAT. So if I were you i'd use butted (9/6/9) tubing, not straight gauge. My frame weighs 5 lbs and the bike total is 34lbs!! I have the Rolling Darryl rims and 3.7 endo's on it...so if you use straight 4130 be prepared for a boat anchor.

Honestly thou, if this is your first build, i'd build something easier. The rear triangle is pretty 'unique' like Walt said. You can also get a complete Surly for really cheap and then have a 'template' to help you build your own fatbike later on...?


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## TrailMaker (Sep 16, 2007)

FTMN said:


> I'm about your size (a bit taller and slightly lighter), and I hope to build my first bike (a fat bike) later this year. I'm very interested to see what you come up with and how it turns out. Any updates along the way would be much appreciated!!!
> 
> What program/software are you using to draw your plans?


Hey;

I know little of a lot, and that includes CAD... as in _very_ little. I downloaded *rattleCAD* from Sourceforge, and found Manfred's enterprise to be pretty well intuitive, if marginally useless. Perhaps if I had more skill in the realm of bicycle creation, I would find it more useful. Yet, it falls moderately flat. Sorry, I'm watching _Cyrano_, so verse doth freely flow!  The above rendering was done in CorelDRAW, with which I am relatively familiar from doing vinyl graphics.

*rattleCAD* works from the premise of the rider's spec, as would a professional fitment. I know very little of that in any formal sense. I only know what I have and what I like, and that is based, as with most things, on the seat of my pants... as it were. The RIP9 fits me like no other bike I've owned. The 9ZERO7 has specs astonishingly close to that. The Mukluk's specs are published. I've used this to come up with my design, and it is virtually the same as the Muk. I'm sure it will change, often.

If this ever all comes together - and there are many impediments - not least of which is my lack of specific knowledge, then I plan to do an expose like the WWTP thread that Jay did, and hopefully nearly as effective.


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## TrailMaker (Sep 16, 2007)

Good Points, *Meriwether*;

And all well taken. I will look forward to reaping your vast knowledge many times, I'm sure. :thumbsup: The tubing question is yet another that relies on learning a lot more. Your point is at once obvious, and elusive. The cost and difficulty of using "real" tube sets is beyond me at this point, in terms of understanding if not means... or skill. The tubes I mentioned might be far better spent on that Cruiser, as I have no particular desire to build a snow anchor.

I am probably better off buying the main component parts - wheels, fork, crank/cogset, etc. - that will set many of my parameters, and working from there. I am all questions with very few answers, but I'll try my best to carry the flag for the clueless masses out there. I might even get a bike built. It might even work!

Maybe I'd be better suited to a RatRod?


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## TrailMaker (Sep 16, 2007)

Hey;

I just went looking around at tube sets on Henry James (time for a real website... ya think?) and Nova. Shakes head. Looks like I'd have to make so many substitutions that the set would not be itself anymore. Straight 4130 may be heavy, but at least I can wrap my brain around it. Choices, choices. :crazy:


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## Walt (Jan 23, 2004)

*Don't buy a set*

Just pick the individual tubes you want and order them. Get the Verus stuff from HJ (a bit nicer, IMO) or Nova brand tubes, but pick every tube out individually. The sets are fine for doing something straightforward, but a fatbike is not straightforward.

You'll actually find that 9/6/9 double butted tubes really aren't much more expensive than straightgauge.

-Walt



TrailMaker said:


> Hey;
> 
> I just went looking around at tube sets on Henry James (time for a real website... ya think?) and Nova. Shakes head. Looks like I'd have to make so many substitutions that the set would not be itself anymore. Straight 4130 may be heavy, but at least I can wrap my brain around it. Choices, choices. :crazy:


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## TrailMaker (Sep 16, 2007)

Walt said:


> Just pick the individual tubes you want and order them. Get the Verus stuff from HJ (a bit nicer, IMO) or Nova brand tubes, but pick every tube out individually. The sets are fine for doing something straightforward, but a fatbike is not straightforward.
> 
> You'll actually find that 9/6/9 double butted tubes really aren't much more expensive than straightgauge.
> 
> -Walt


Yes;

I can see that you are right. Thank you very much for your input. It also occurred to me to wonder if stainless might be a viable option for this frame. Beyond the obvious corrosion resistance, I do not really know what the comparison would be to 4130 in terms of user-friendliness, strength:weight, ride quality, etc. I have TIG'd some stainless, and it is nice to work with. Bending was another story!

Questions after looking at tubes; Given the large size of the myself, the frame, and the length of the tubes, should I be looking at 38-.8/.5/.8, 42-.9/.6/.9 for the DT. 28.6/31.7/38.1 for the TT, probably a pretty big seat tube, 19/22.2/25.4 for the CS/SS? I do need the strength of size, but don't want more weight than necessary, and I do not know the relative strengths of the many tube sizes available. Still more questions than answers, I know, but once I know where I am going I can start toward getting there.

Lots of thread views.... ALL ideas appreciated! :idea:


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## dr.welby (Jan 6, 2004)

TrailMaker said:


> Yes;
> 
> It also occurred to me to wonder if stainless might be a viable option for this frame.


do re me fa so la ti NO.


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## Walt (Jan 23, 2004)

*Stainless = junk*

I have some personal bias against stainless after all my failed attempts at building frames with it, but at the very least, it is totally inappropriate for a beginner for a bike frame.

Get 9/6/9 for everything.

-Walt



TrailMaker said:


> Yes;
> 
> I can see that you are right. Thank you very much for your input. It also occurred to me to wonder if stainless might be a viable option for this frame. Beyond the obvious corrosion resistance, I do not really know what the comparison would be to 4130 in terms of user-friendliness, strength:weight, ride quality, etc. I have TIG'd some stainless, and it is nice to work with. Bending was another story!
> 
> ...


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## TrailMaker (Sep 16, 2007)

I think I have made a tubing decision;

Thanks to Peter @ Whipsmart Fabrication, who has been beyond helpful, I think I have decided what tubing to use. First frame, cheaper, easier, less hassle, bendable even... I've decided to go with straight wall .035" 4130 CroMo tubing. Using just the downtube as an example, it works out like this;

Nova 38.1x750 8/5/8 = 1.15lb = .467lb/ft = $10.06/ft = $24.75
Aircraft Spruce 1.5 x750 .035 = 1.34lb = .548lb/ft = $ 6.00/ft = $14.76

.035 is .081lb/ft heavier, but $4.06/ft cheaper. Not that much weight... in the larger scheme of this project. Price is not the overriding factor, but cheaper is always nice. Even if I have the math all screwed up, which is entirely possible for me to accomplish, it still makes good sense to me. I'll save the "better" stuff for my SECOND frame.


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## rocwandrer (Oct 19, 2008)

frame number 14 for me was my fat bike. My thoughts in brief and rough order of importance:

That drawing is the easy one. The hard drawings are in the other planes. Start with an axle and a rough tire cross-section. Add cranks, chain paths, chainrings, frame tubes, etc. You can build a good bike without a perfect chainstay drawing, but not without at least thinking about the issues present in that drawing.

That fork is WAY too wimpy for you.

Do you want fat for summer or for winter/beach/soft conditions? Winter you may want longer stays, more standover clearance, a lower BB, a longer head tube/taller stem, etc.

Treat tire choice and tire pressure the same as you would with suspension travel. When you figure BB height, don't forget that the rolling diameter of the tires depends on pressure. A BFL measures out at nearly 30" diameter, but at 3 psi with a heavy rider the rolling diameter is less than 28"... A Nate at 15 psi has got to be near a 29" rolling diameter. That's a whole inch of BB height change between a potential winter setup and a potential summer setup, in this case in the right direction, but that'll depend on your own personal setup preferences, so keep it in mind.

I bet you'd be happier with a LOT beefier downtube.


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## Walt (Jan 23, 2004)

*True Temper!*

Despite the fact that I have vowed to destroy them, I must suggest the HOX2DT01 (available from Henry James). It is nice and strong, it is easy to work with, and it's pretty cheap too - about $24, I think. You'll need head tube stock from somewhere anyway, so you're going to need to order something from one of the actual bike tubing shops.

If I were doing this bike:
Head tube: MHT or MHT44
Downtube: HOX2DTO1
Toptube: AVRTT (should be long enough, if not AVRDT)
Seat tube: AVROBST (requires 26.8 post, but highly forgiving/easy to work with)
BB/dropouts: Paragon

Get the chainstays and seatstays from Nova, but do your homework on tire/crank clearance first. The front end of the bike will be the easy part!

-Walt



TrailMaker said:


> I think I have made a tubing decision;
> 
> Thanks to Peter @ Whipsmart Fabrication, who has been beyond helpful, I think I have decided what tubing to use. First frame, cheaper, easier, less hassle, bendable even... I've decided to go with straight wall .035" 4130 CroMo tubing. Using just the downtube as an example, it works out like this;
> 
> ...


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## Meriwether (Jul 26, 2007)

rocwandrer said:


> That drawing is the easy one. The hard drawings are in the other planes. Start with an axle and a rough tire cross-section. Add cranks, chain paths, chainrings, frame tubes, etc. You can build a good bike without a perfect chainstay drawing, but not without at least thinking about the issues present in that drawing.
> 
> Treat tire choice and tire pressure the same as you would with suspension travel. When you figure BB height, don't forget that the rolling diameter of the tires depends on pressure. A BFL measures out at nearly 30" diameter, but at 3 psi with a heavy rider the rolling diameter is less than 28"... A Nate at 15 psi has got to be near a 29" rolling diameter. That's a whole inch of BB height change between a potential winter setup and a potential summer setup, in this case in the right direction, but that'll depend on your own personal setup preferences, so keep it in mind.


Great point about tire pressure. I didn't even think of it as "sag" and to account for it in the CAD drawing! How the heck to measure it?! Depends on tire pressure but also rider and frame weight, etc.. I run 10lbs in the snow so i bet i lose a good amount of BB height...I'll have go get my wife to measure the sag some day.

The other thing in the quote above that is super important is to draw out the rear tire clearance and how far apart you'll need the chainstays and seat stays. I used S-bend chainstays with the 100mm wide BB and still had a pretty good dimple for the tire clearance. If I hadn't drawn it I would've gone through two sets of stays to get it right.

Great math BTW, i am surprised it's not that much different in weight! I think it's good to use 4130 for practice welding but I would go with 'real' bike tubes for a bike. I like (prefer) Walt's tubing suggestions to straight 4130 but I bet you could get some tubes from Nova that would work since they are probably much cheaper.

PS- I was totally joking about being an expert after one fatbike build, i think you know that but just wanted to say it aloud. It was only my 9th frame ever.


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## Meriwether (Jul 26, 2007)

really not sure how i double-posted! i need help deleting this one...


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## rocwandrer (Oct 19, 2008)

its a choose your own adventure post... it looks like a double post, but they don't end the same way!


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## TrailMaker (Sep 16, 2007)

rocwandrer said:


> frame number 14 for me was my fat bike. My thoughts in brief and rough order of importance:
> 
> That drawing is the easy one. The hard drawings are in the other planes. Start with an axle and a rough tire cross-section. Add cranks, chain paths, chainrings, frame tubes, etc. You can build a good bike without a perfect chainstay drawing, but not without at least thinking about the issues present in that drawing.
> 
> ...


Great Stuff;

- This will be a year-round machine. Another trail bike capable of overlap with, but reaching into the more unrideable conditions for, a normal bike.

- I have never done a BIKE before, but having built many things over the years, I can see clearly from the outset that the rear of the bike is the trick. All the spacing will take hard parts in hand to measure and mock, and lots of fiddling.

- As previously mentioned, I plan on BUYING a fork from someone; Salsa, Surly, Vicious, ??? I basically just drew any old fork on there for geometry purposes.

- I will give some more thought to the lower geometry. I want the monster truck roll over height without making it less stable. I'd like to be able to boondock this thing through the woods without worrying, but I also don't want it to suffer from too high a CG.

- Great point on "sag". I plan to use 80-90mm rims with Nates. Accurate measurements of just such a setup from someone would be a good start for me!

- I look at tubing, and when I see 1.5x.035 4130, I know exactly what that is. When I read DFGC^^%XVZ#^#$... my head starts spinning again. More study.

*Thanks for great posts, Walt, Whit, Roc, EVERYBODY. Keep the stream flowing!*


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## TrailMaker (Sep 16, 2007)

Walt said:


> Despite the fact that I have vowed to destroy them, I must suggest the HOX2DT01 (available from Henry James). It is nice and strong, it is easy to work with, and it's pretty cheap too - about $24, I think. You'll need head tube stock from somewhere anyway, so you're going to need to order something from one of the actual bike tubing shops.
> 
> If I were doing this bike:
> Head tube: MHT or MHT44
> ...


Thanks Walt;

However, let me ask you an honest question; what are your reasons for preferring these specific bicycle grade tubes over "generic" 4130 tubing? I imagine you have some very specific reasons, and I'd like to hear them for my own edification (and others following along, for that matter).


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## Walt (Jan 23, 2004)

*Several reasons*

I like the True Temper stuff for several reasons:

-Most important: Made in the USA. I am one of those people who wants to buy something from a real person earning a real wage who I might actually get to talk to on the phone (let's not start a political discussion here; that's just my personal opinion) and support the local economy.

-It is available in bulk in relatively small quantities (ie, I can order a box of 50 tubes direct from TT, and the price is ~1/2 that of buying individual tubes). This is huge for those of us who make a living building bikes but don't build thousands a year.

-It tends to be high quality and I don't find as many blems/problems as other similarly-priced tubes. This is entirely anecdotal, of course - you should always check your butts and QC every tube (don't ask how I learned THAT little lesson!) regardless of the manufacturer. Some people may have very different experiences (ask Richard Sachs about TT sometime!)

-True Temper has been really excellent at making new tubes happen. They were some of the first to do downtubes and chainstays that would work for 29ers, they did a sweet lightweight steerer tube when rigid forks came back in style, and they built the first head tube stock for the 44mm/tapered headsets. Awesomeness.

Of course, I'm also implicated in all sorts of efforts to destroy them by popularizing their products. So I've got that going for me, which is nice. :madman:

-Walt



TrailMaker said:


> Thanks Walt;
> 
> However, let me ask you an honest question; what are your reasons for preferring these specific bicycle grade tubes over "generic" 4130 tubing? I imagine you have some very specific reasons, and I'd like to hear them for my own edification (and others following along, for that matter).


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## TrailMaker (Sep 16, 2007)

You're the Tubing Terminator!

All good points, and thank you. I also expected you to say that the physical properties of those tubes make it nicer to machine, file, weld, etc. I'm going to assume that is the case as well. I'll just have to decide...
-------------------------------------------------------------------------------------------------------------------------------------------------------
I really was a bad boy today. I blew off paying work and spent the day mitering and TIGing some tubing for practice. Just some generic run of the mill 1" x .030-something ERW, but I was using 70S2 filler. It was an old clothes rack or some such that I harvested for the tubing. I was playing with different settings on the welder (Miller Synchrowave 180SD) and trying to get some of those beautiful "machined" looking stacks of dimes. Well, I had some areas of TIG Bliss, and overall I am not too disappointed in them. They are not my idea of artistically satisfying, and I do aspire to be better at it, but they are probably 80% there, and should at least be sound. I am wondering if the very low grade nature of this material has bearing on how well one can weld it? For my own sake, I will assume that is does. I had to grind off the powder coat, probably using far too aggressive an abrasive disc on my die grinder, and I was not being overly fussy about cleaning it either. I'm guessing a nice clean high quality tube would yield better results, and I look forward to that.

I started somewhere around 85A/20 gas flow and worked my way down in 10s to 45A/15 flow at the end, where I got my best and most consistent results. I noted that I am far better at getting a nice flow when the tungsten is pointed into a miter where the pieces are somewhere closer to 90*, and not really very good when the two parent surfaces are nearer parallel. I note it is much easier to burn the mitered piece out on the flats, and I probably need to concentrate more of my heat in the non mitered piece, and also get the filler in there sooner to sink the heat away. I'm going to have to play with my positioning, angles, and possibly how I prep the miter there to make for a more successful weld.

I actually started by trying to bend this stuff on my Pro Tools 105, 3'CLR die set. Fail! Interestingly, the worst bend was the one I packed with sand. The best one - unacceptable as it may be - was the first one that I just hammered out as fast as I could. Wonder if good tubing bends better too? Wonder if a 4"CLR die set would get me through better?

Some answers, more questions. Process.


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## TrailMaker (Sep 16, 2007)

Thanks to all who have commented;

I continue to refine my layout with intuition, study, and the help of a couple of very generous folks privately. Little tweaks include adding crown races, and a riser bar. More serious mods include raising the BB drop a half inch to only 2", gaining the same for BB height to around 12.8. This shortened the CS length a touch, but not too significantly I don't believe. I also decided to lengthen the HT to an even 7". This also raised my bar height a touch, and may consequently lower my stack height, which I am interested in reducing relative to all my other bikes. I also have settled on a 24" ST, which I hope offers me a similar reduction in unsupported seat post length, which has always bothered me on my other bikes. Someone mentioned standover. Both my 7" travel freeride sled and my 4.5" travel RIP9 have about the same standover as this design, ironically, even both having curved drop top tubes.

I still need little things like final dropout choice so I can calculate my SS angle and junction point with the ST. I'm sure there are many others I have not considered. It's about time to start buying components for measuring purposes. The harder calculations and drawings are yet to come!

Comments on this or anything pertaining thereto are still welcome.


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## TrailMaker (Sep 16, 2007)

*Update:*

Just in case you thought this was just another... um.. pipe dream;

- Fat Wheels are here!
- Husker Du's & tubes, cranks, BB, cassette, grips, shifters, headset, all coming Wednesday.

Many many many things to learn and figure out yet, but it WILL happen. We got 4" of snow last night too!! :madman:


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## TrailMaker (Sep 16, 2007)

Step upon Step upon Step;

Amongst the many aspects of this project I've been mulling, my thinking leads me to believe that while I may be able to bodge this thing together without one, a jig would make the job MUCH easier. So too will it be useful in the future, given proper configuration. To that end I have been working out my own unique design for the ubiquitous aluminum T-slot arrangement popularized by Dear Dr Welby, as it does seem to be the "easiest" row to hoe. After much search and debate, I have decided to use 80/20 products, and I have further decided to source all of it through Fastenal. Neither of these are the cheapest way to go, but in the case of 80/20, they offer a very comprehensive menu of widgets to get'r done, and Fastenal won't charge me shipping.

Not including the fixtures to hold the bike bits to it, the cost for the jig materials is around $315, before tax.


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## TrailMaker (Sep 16, 2007)

Jig design;



















With any luck, I might get one of these ^^ in on my Fatbike... this decade!
-
-


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## Blaster1200 (Feb 20, 2004)

That jig design leaves so much room for misalignment while tacking, that you're probably better off not using a jig at all. And if you're only planning on making a dozen frames or so, I don't see why the bother with a jig like that. Even the best commercially available jig won't ensure even a reasonably straight frame for a newb.

Look at Dr Welbys' Instructables for his jig named something like "almost not a jig, jig." That will be far more useful for you, I think.


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## dr.welby (Jan 6, 2004)

Blaster1200 said:


> Look at Dr Welbys' Instructables for his jig named something like "almost not a jig, jig." That will be far more useful for you, I think.


Almost Jigless Bicycle Frame Building

Shiggy built a really cool fancier version of it, but I think all the pictures were in the now defunct FrameForum?


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## TrailMaker (Sep 16, 2007)

Blaster1200 said:


> That jig design leaves so much room for misalignment while tacking, that you're probably better off not using a jig at all. And if you're only planning on making a dozen frames or so, I don't see why the bother with a jig like that.
> 
> Look at Dr Welbys' Instructables for his jig named something like "almost not a jig, jig." That will be far more useful for you, I think.


Hmmm...

Better off without this jig? Better off with the almost-not-a-jig-jig... even though it is a non-jig, it is more of a jig than my jig-jig is? OK...



> Even the best commercially available jig won't ensure even a reasonably straight frame for a newb.


So... it's more down to mitering precision and studious tack/weld sequencing? Then the jig is only to improve speed in setup & repetition? One wonders why anyone bothers with one, except that they look good in pics! 

Of course you would have no idea that I have far more structural experience than might be apparent. This is the fixture that picks up the hard points and holds the key bits. Items to brace these can and will be added when push comes to shove.


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## JaquesN (Sep 14, 2009)

*quick 2 cents from another novice, on the jig thing*

Here's why you don't need a jig: you won't be tacking the whole frame together all in one pass.

You'll do down tube to head tube, seat tube to bb, down tube assembly to bb, etc. In between you'll check angles and alignment.

So* you only need a way to hold two tubes to each other at the angle you want them to be joined*. You can do that with angle iron and some clamps. Even easier with some tube blocks like the ones from Paragon.


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## GrayJay (May 16, 2011)

I recently completed conversion of an old hardtale into a cheap fatbike. I utilized an old rev1 Manitou suspension fork and that dictated most everything else for the re-build. Because the fat suspension fork was so tall and had relativly little rake, I wanted the re-fitted rear triangle to result in a 70° HTA so that I would not have excessive fork trail. (think I wound up around 90mm trail). I didnt really think through the implication of all this and just slapped it together using the HTA as my primary goal. I wound up with a REALLY tall bottom bracket, measures around 14" off floor and essentially has zero BB drop. First time I rode it, it felt wierd to be positioned so high but my perspective and reflexes quickly adapted. I really wouldnt say that a super high position feels terribly less stable than a low BB, it is very rideable and has miles of pedal clearance for riding in ruts. Only downside is that getting up on the saddle and getting moving is tricky on deep snow/loose conditions. Sort of takes a coordinated jump up like getting up on a horse and then using the momentum of your jump to move until you can quickly start pedaling and generate enough stability to stay ballanced. Not ideal but it is somewhat viable. I have enough standover clearance to safely straddle the TT on hard surface but if I loose it on deep snow I've leaned to just let the bike lean over first before dismounting to one side rather than landing strait over the TT. Build album here;

https://picasaweb.google.com/110245208849091527987/FatbikeBuild#

For the rear end, I started with a set of offset fat wheels/tires, added dropouts to the new chainstays and just slowly started adding bends to the stays until they cleared the tires and then connected to the BB. Bending the stays was suprizingly easy (used my road fork bending jig). I used Nova chainstays that were delivered as single bend but it probably would have been easier to just start with strait chainstays and put the bends where they were needed, definitly better than pre-bend S chainstays. THe seatstays were originally strait and were even easier to bend. Once I had the chainstays cut and mitered to the BB shell, I made a really simple jig that clamped to the ST and DT to hold a dummy axel in place which in turn held the dropouts and chainstays in place while brazing. I previoulsy had built a lugged steel frame just using a surface plate and V-blocks, but this simple jig was a great addition for holding the chainstays in alignment to the triangle, picture as per below link...

https://picasaweb.google.com/110245208849091527987/FatbikeBuild#5699625420043921186


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## Meriwether (Jul 26, 2007)

Going back to the "sag" question on fatbikes with low pressure...i have a quasi-scientific answer.
Furthering my effort to be elected DOTW (dork of the week), I did a quick test tonight.

In my garage (cement floor), I put my tires at 5lbs each, put the end of a pencil in the crankarm bolt attached with some duct tape, leveled the bike against the wall to be vertical, and measured the BB height without any weight (other than the bike obviously) and it was 12". I then got on the bike, and used a yardstick to slightly 'swipe' the pencil against the yardstick and mark where the center of the BB was with sag. Not an exact measurement of course but after several iterations I found it was around 0.25" lower than without my weight (I weigh about 165lbs). So...since 5lbs of tire pressure is at the low end of what people use on fatbikes so from now on i'll add 1/4" to the BB height in my frame specs. I was kinda surprised it wasn't more sag! I was expecting at least a 1/2" or more.


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## TrailMaker (Sep 16, 2007)

Jaques - I have indeed absorbed those ideas from my studies, which are not nearly concluded, of course. What can I say. I'm a very visual person, and I will very much enjoy staring at all those tubes fit together in a jig before I start welding anything. I have a very good mind's eye, and I can see my design on the computer screen, but even beyond pulling a full size print off my plotter, there will be nothing like seeing it in the flesh to make a final judgement as to whether it pleases me or not, or even works at all. The real animal will be the final arbiter. 

Jay - Great "junk yard" build. I had read your thread previously, but it was good to go back and peruse the pics again. Thanks for the refresher. I am paying CLOSE attention to BB height/drop. I don't need a monster truck, but I'm trying to avoid a peddle basher too. As of now, I have a 12.8 height to center and a 2" drop, which I think is a good compromise.

Whit - Speaking of BB heights. Very interesting finding. I too would have thought it would offer well more sag than that. I am far heavier at 240lbs, but I also would be running higher pressures because of that, so the figure might actually stay fairly uniform. Now you just need to consult Rube Goldberg again, this time for a tire/frame flex test procedure to compliment your brilliant sag routine.


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## TrailMaker (Sep 16, 2007)

OK;

Here's a question. How do you index and mark your miters to get them on the same centerline on either end? I imagine people have differing ways of doing it, and I'd like to hear yours.


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## JaquesN (Sep 14, 2009)

*Centerlines.*



TrailMaker said:


> Here's a question. How do you index and mark your miters to get them on the same centerline on either end? I imagine people have differing ways of doing it, and I'd like to hear yours.


When I first clean the tube, I mark a line on it with a piece of angle iron and a scribe. I line that line up with my tubing blocks. I have the Paragon blocks, and I've made a centerline mark on most of them to make this easier.

The other way is to mount one or two tube blocks to the tube and not remove them until the mitering is done.


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## coconinocycles (Sep 23, 2006)

Check out my latest blog posts below, I've been documenting an "average" build. 
Have you thought about if the wide fork will hit the DT when turned, and have you thought about the fact that trail increases when you are actually riding in snow or sand? 
The contact patch is forward/larger. 
- Steve Garro, Coconino Cycles.


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## dr.welby (Jan 6, 2004)

coconinocycles said:


> Have you thought about if the wide fork will hit the DT when turned, and have you thought about the fact that trail increases when you are actually riding in snow or sand?
> The contact patch is forward/larger.


I think you mean trail decreases, since the contact patch moves forwards.


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## coconinocycles (Sep 23, 2006)

dr.welby said:


> I think you mean trail decreases, since the contact patch moves forwards.


That's it. It's why when you hit a sand bog your steering goes all wonky.
- Steve Garro, Coconino Cycles


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## TrailMaker (Sep 16, 2007)

coconinocycles said:


> Check out my latest blog posts below, I've been documenting an "average" build.
> Have you thought about if the wide fork will hit the DT when turned, and have you thought about the fact that trail increases when you are actually riding in snow or sand?
> The contact patch is forward/larger.
> - Steve Garro, Coconino Cycles.


Hmmm...

Interesting points. The sort of things that hit you after you have COMPLETED your first frame. Spoken like someone who has learned these lessons through experience!

Some of this has been answered by Salsa, since I took much of the basic geo from the Mukluk. One of the bits of previous advice was to wait until all parts were in hand before cutting and welding. Indeed, the Salsa Enabler is coming from our good friend *MendonCycleSmith* next week. I did not plan to anything permanent until I had all the bits, and when the fork comes I will take some measurements and add that check to my list!

As for trail, it decreases and the steering goes wonky because the front wheel sinks into softness, and does this not only exist before the rear tire hits the same soft patch and the chassis levels again? If one is prepared and sitting back, ready to peddle, that is the fix. If not, well... we've all face planted before, eh?

Thanks, Mr. Garro.


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## TrailMaker (Sep 16, 2007)

TrailMaker said:


> OK;
> 
> Here's a question. How do you index and mark your miters to get them on the same centerline on either end? I imagine people have differing ways of doing it, and I'd like to hear yours.


Hmmm...

It occurs to me that I could rig up some sort of pen holder and center line the tubes on my gauging table.


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## TrailMaker (Sep 16, 2007)

Well;

I took me so long to wade through all of the stellar advice as to how to get information on measuring/calculating drive side CS clearance that I haven't been able to post. I finally came up with the brilliant idea that since no one actually had that information, I would have to simply measure the actual parts. I do not have my 100mm BB shell yet, so I measured from the centerline of a 73 and added 13.5.










It looks like if I want to use full diameter tubes, I can get by using two 2.5mm BB spacers. If I decided to go through the tribulations of manipulating the tubes in that area, I might be able to eliminate 1 or both of the spacers, which would be ideal. The small little squares next to the tire are .5" wide, so in reality I likely have lots of room to play with.

Moving forward....


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## TrailMaker (Sep 16, 2007)

Mill Again Mill, for my Jiggity Jig.


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