# It Begins; Trailmaker #1 - Fatbike



## TrailMaker (Sep 16, 2007)

*Step 1 - ST-to-BB housing;*








How accurate can this jig be?



















Left; measurement at BB housing. Right; measurement near seat end.

.018" would seem to be pretty good, no? Acceptable?
-
-
(EDIT) I modified my gauging setup, replacing the ineffectual clamp arrangement with a threaded rod post and using my shouldered BB housing mandrels. The measurement is actually only .012" deviation.


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## Walt (Jan 23, 2004)

Don't bother with too much alignment checking until the front tri+chainstays are all on the bb shell. Until then, you'll just keep distorting the shell and going crazy trying to figure out why things won't stay in alignment. 

Once you have everything welded to the BB shell, face the shell and do your measuring. 

If you're asking if this is good enough to continue, hell yes. I'd say if the ST is off by more than a mm or two after you tack the shell on, that's probably too much, but obviously it depends on the length of the seat tube and how picky you are - everyone has a different number for what is acceptable and what is not. You won't feel most alignment "problems" when riding a bike with 4" squishy tires!

-Walt


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## TrailMaker (Sep 16, 2007)

Thanks Walt;

At the least, I will use the information from this measurement to choose which side of the ST to weld first, hoping to draw it back in the right direction a bit.

I can say very certainly that I do not like what I am getting trying to connect the CSs to the DOs. Not happy at all, but it will be what it is and I'll have to figure out some more pleasing and effective method for #2. That or scrap it and start again, this time with a bend at the DO end (3-bend stays) to make the stays arrive there on a more parallel footing.


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## Walt (Jan 23, 2004)

*Maybe we can help*

Is it the acute angle/outboard side of the joint? Might be time to get some scraps and practice a bit.

-Walt



TrailMaker said:


> Thanks Walt;
> 
> At the least, I will use the information from this measurement to choose which side of the ST to weld first, hoping to draw it back in the right direction a bit.
> 
> I can say very certainly that I do not like what I am getting trying to connect the CSs to the DOs. Not happy at all, but it will be what it is and I'll have to figure out some more pleasing and effective method for #2. That or scrap it and start again, this time with a bend at the DO end (3-bend stays) to make the stays arrive there on a more parallel footing.


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## TrailMaker (Sep 16, 2007)

Frankly;

I came to it and had no real idea how to make this interface work. I've been considering it for 
some time, but there was no magic when the curtain rose. If there is an elegant way, I did not 
find it. I flattened the end of the tube a bit and then slotted it. Now I have the feeling I should 
have simply left the profile round and mitered the DO tab into the outside surface. I really don't 
know, but I'm sure I don't want to waste a lot of tubing trying to figure it out! :madman:










I've got some scrap stays from the bending discovery that I might better fool with and figure
this out. Any insights or strategies are appreciated.


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## TacoMan (Apr 18, 2007)

Cut the tube at an angle and weld a cap on it. Then weld the drop-out to the end of it. That is a very common way to do it.

What is your CS length on the fat bike?


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## kampgnar (Apr 13, 2007)

TrailMaker said:


> Frankly;
> I came to it and had no real idea how to make this interface work. I've been considering it for
> some time, but there was no magic when the curtain rose. If there is an elegant way, I did not
> find it. I flattened the end of the tube a bit and then slotted it. Now I have the feeling I should
> ...


For this type of fitup, miter the DO tab to the inside of the CS ID and cut the outside of the CS to a nice profile and cap it off. My latest frame had this with 7/8" stays and Paragon horizontal drop outs.


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## RCP FAB (Jun 15, 2011)

Paragon makes steel bullets. I have yet to try them though.


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## TrailMaker (Sep 16, 2007)

Hmmm...

Good food for thought. I just need to sit and stare at it for a while. One thing's for sure, those stays are coming off! Thanks guys.

The CSs are 17.875.


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## MDEnvEngr (Mar 11, 2004)

TM, 

IMO, brazing is better when using plate dropouts. Cut the dropouts to get some insertion into the CS. File a (round) vertical slot - doesn't have to be too deep into the end of the stay. Braze and file to the shape of your preference. It seems like there are a tons of wacky ways the TIG-builders use to mimic this simple and fast brazing technique.

If I was a TIG dude, I would use the hooded wright-style dropouts only.

Whatever you go with, good luck and have fun! B


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## kampgnar (Apr 13, 2007)

MDEnvEngr said:


> It seems like there are a tons of wacky ways the TIG-builders use to mimic this simple and fast brazing technique.


I would agree that it would be faster and less work to straight up braze a plate style DO, but wouldn't discredit it as wacky. TIG welding this style is common especially with titanium a la Firefly and IF.
Hobby level fab is typically limited (budget, space etc...) to one form of joining, TIG or O/A. Both have clear advantages over the other when comparing different operations, but more often than not just "run what ya brung" starting out.

TM, great to see you are on your way.


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## TrailMaker (Sep 16, 2007)

Thanks All;

On principle, I tend to like a true socketed joint where the DO tab was inserted and welded, but the angles here don't lend themselves to that. I thought of bending the tabs to more closely match the tube angle, but the disc mount tabs on the left side DO foiled that idea. I never thought of capping and welding the tab onto that surface, but it does have some appeal. In this case, my stays will mount on the back side of the tab, as I have it drawn in my mind.

And thanks Kamp. I've been on my way for quite a spell, but now I'm heading somewhere, eh! :thumbsup:


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## MDEnvEngr (Mar 11, 2004)

kampgnar said:


> I would agree that it would be faster and less work to straight up braze a plate style DO, but wouldn't discredit it as wacky.


Oh, no discredit intended! Just an observation that it is a lot of extra steps to essentially mimic something so simple. With Ti there is no option such as brazing, so you're stuck if you want to use plate-style dropouts.

B


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## Meriwether (Jul 26, 2007)

kampgnar said:


> For this type of fitup, miter the DO tab to the inside of the CS ID and cut the outside of the CS to a nice profile and cap it off. My latest frame had this with 7/8" stays and Paragon horizontal drop outs.


Kampgnar- Thanks for sharing this method, I always have wondered how the heck IF and others did that! Do you have a picture of the inside DO/CS before welding? Looks great btw.

TM- nice on getting goin!! Looking forward to the process. 
Cool BB-CS fixture setup and that's plenty accurate IMO. Sounds like you are plenty aware of tig tips but if you put a heavier tack on the side you want to pull the top of the ST towards that may correct the slight offset. If that doesn't do it, lay a 2nd pass on that same side. But I leave it alone if it's less than 1mm...


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## Meriwether (Jul 26, 2007)

I think hooded dropouts would serve you better for this sharp an angle and large diameter CS's at the DO. So if you are still wanting to use the dropouts you have and aren't adverse to extra work... I stumbled across this...http://anthonymaietta.wordpress.com/2011/04/19/dropout-modification/
interesting solution if time consuming.
You could fab as big a "hood" on there as you need!


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## j-ro (Feb 21, 2009)

MDEnvEngr said:


> TM,
> 
> IMO, brazing is better when using plate dropouts. Cut the dropouts to get some insertion into the CS. File a (round) vertical slot - doesn't have to be too deep into the end of the stay. Braze and file to the shape of your preference. It seems like there are a tons of wacky ways the TIG-builders use to mimic this simple and fast brazing technique.
> 
> ...


LOTS of little details in ths picture. Looks great man


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## Eric Malcolm (Dec 18, 2011)

TM

Great to see you on your way.

I went back to another post by you on Frame Jigs to see what you were using for the drop outs. 

To me, they are too short on the chainstay tab. I did a set-up where I made my own Drop-outs out of 1/4" flat steel, and bent them in so that they lined up slot-wise with the centre line of the chainstay.

Looking at the drawing above, this could easily correct your problem, and as you say, you enjoy the journey, so you could halt the build, step back, get creative, and produce a better fitting drop-out and keep us in suspense for a little while more. A little longer won't kill us, and we want to see a good effort for the time you've been keeping us waiting....368 posts later.

Great tube bending by the way.

Eric


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## edoz (Jan 16, 2004)

MDEnvEngr said:


> TM,
> 
> IMO, brazing is better when using plate dropouts. Cut the dropouts to get some insertion into the CS. File a (round) vertical slot - doesn't have to be too deep into the end of the stay. Braze and file to the shape of your preference. It seems like there are a tons of wacky ways the TIG-builders use to mimic this simple and fast brazing technique.
> 
> ...


Who makes those dropouts?


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## TrailMaker (Sep 16, 2007)

Continuing Thanks for the Ideas and Chatter;

They are informative, and stimulative, at the least. Well, seeing a few ideas suddenly popped my brain into gear and I saw my solution straight away. A new set of stays were bent in minutes, mitered, tacked, and... WAIT. :madman: :madman::madman:

Houston........ I had to have a serious chat with the design department. Seems they got so carried away with chain ring clearance, and tucking those stays tight to the wheel all the way back, that they neglected to leave room for such niceties as the brake rotor and the cassette!!! Who knew? They assured me that it was only a minor tweak to the design and so I... um, they whipped up a quick revision over lunch time and the new stays were set in place before the end of the day, this time with the rotor & cassette ON the wheel, just for good measure. 

It's all I can do to keep from welding and finishing up these DO junctions, but given the possible need to adjust for other deviations, that would not be wise until everything else is ready for final welding. They will look slick, and all the parts will fit to boot!

Old...










New...


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## TrailMaker (Sep 16, 2007)

Eric Malcolm said:


> TM
> 
> Great to see you on your way.
> 
> ...


No. no....

Of course the bending is good, but don't try and lube up at the end. Yur not building up Rep with this stuff, Bub. Besides, I never told anyone to stop breathing while I had my fun. It's yur fault if you turned blue.  But don't let me stop you. You look good in blue. Carry on!

The DOs were a gift from a friend, and happen to match the angles of my stays perfectly. However, they are a little short of tab, and they are Moly and stiff as hell. No bending these! I've got it licked anyways. I thought of making my own, but with integrated brake tabs and derailleur hanger, it was just a bit much. Things like these DOs and braze-ons can come along when I've figured out the basics better. This is already complicated enough.


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## Meriwether (Jul 26, 2007)

edoz said:


> Who makes those dropouts?


Those are Naked boomerang dropouts if I'm not mistaken...?


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## J_K (Jan 18, 2010)

Meriwether said:


> I think hooded dropouts would serve you better for this sharp an angle and large diameter CS's at the DO. So if you are still wanting to use the dropouts you have and aren't adverse to extra work... I stumbled across this...anthonymaietta.wordpress.com/2011/04/19/dropout-modification/ Dropout Modification | Maietta Handbuilt Bicycles[/url]
> interesting solution if time consuming.
> You could fab as big a "hood" on there as you need!


Thanks for sharing that link, look interesting :thumbsup:

Trailmaker, it's a very interesting project you've got going on here!


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## kampgnar (Apr 13, 2007)

Meriwether said:


> Kampgnar- Thanks for sharing this method, I always have wondered how the heck IF and others did that! Do you have a picture of the inside DO/CS before welding? Looks great btw.


Thanks! I don't have any pictures but it's fairly simple in concept. After figuring how far the tab should extend into the CS, I scribe a line and use a file to contour the inside of the tab to the shape of the CS ID. This takes a while to dial in and ends when comfortable with how well it fits up. Swaging/flattening the inside of the CS a bit where it meets the DO helps with fit up and will reduce the amount of material needed to remove from the DO tab.

The process was with the front triangle complete and loaded in the fixture. The DOs were loaded, the CSs bent and mitered to the BB, and I continued filing/adjusting until everything was correct. I tacked in the CSs to the BB and DOs, and then tacked in the caps (created from down tube drop cuts). After everything was tacked I finished welding out. The cap was fused all the way around and smoothed down for aesthetics.


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## TrailMaker (Sep 16, 2007)

This actually fits with all the components on the wheel.
I thought that would be a nice touch, this time.




























Not welded to the DO yet (just tacked), but the tube joinery itself is finished.


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## Eric Malcolm (Dec 18, 2011)

TM

Looking good now.

I had another look at another post by you, At Last - Yet Another Bending Thread.

O/K. I see 4 S-bent stays. Are these to be used as both C/S and S/S?

If so, you need to have a look at the S/S. All 4 have been made with 71/4" straight between bends.The problem here is that this will work with even length D/Outs from axle centre. The ones that you are using are C/S short, with S/S longer by maybe 2"? to accomodate the disc caliper. This will mean that when you fit up the S/S to get the nice rounding past the tyre to the Seat Tube the lower end joining the DO tab will be out by that 2". The Bend should start at 51/4"? or whatever. When you put on the 'brake bridge' it needs to match the chainstay bridge you have now fitted, you get the idea? 

TM, I'm not trying to "P" you off here. If I'm reading the Pic's correctly, I am attempting to put you in right direction. Its important to get it right. The correction to the C/S is very good.

Eric


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## TrailMaker (Sep 16, 2007)

I know;

You were giving me the gears, and in an act of true selflessness, I was offering them back to you! 

Yes, those are 4 CSs, none of which were the final ones, by the by. I have already 
overlooked some really obvious stuff, but that was not one of them. I never intended them 
to be SSs. Indeed the DO/SS tab is far longer, and also the length of the SS at the ST end 
is longer as well. While I will freely admit that the SSs are giving me some trouble, I was 
aware they were different.

Because the SSs are confounding me a bit, I have decided that the next step that needs 
taking is to miter the CSs for introducing the BB/ST assembly. No sense fighting the SS 
fitting until there is somewhere to fit them!


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## NEPMTBA (Apr 7, 2007)

Late to the party...

...but subscribed

Look'in good!


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## Eric Malcolm (Dec 18, 2011)

TM

Thanks for clarifying. I hoped I was wrong.

Good call on going back to the frame. The seat stays really should be the last item to go on as you can 'see' the final picture better when you fit a wheel in there. The alignment is much easier to do also. Visually, when approaching a bike from the rear, the seat stay is a bikes defining expression.

You will get it right I'm sure.

Eric


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## TrailMaker (Sep 16, 2007)

Eric Malcolm said:


> You will get it right I'm sure.


I hope to be worthy of your confidence, and prove it well given.

It occurred to me when the smoke was thickest that I could not fit them unless the space for them existed. I was trying to fit them to the stay jig, it simply was not working, and I was not sure why. I'm still a little confused, as they did not seem to work like my drawings suggested. However, I'm an "it is what it is" type of person, so they will be made to fit where they go.

Best laid plans of mice, and frame builders...

I have them shaped and tacked together, waiting to be mitered to the ST/BB assy. after it is tacked to the CS assy, hopefully tomorrow.


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## Clockwork Bikes (Jun 17, 2006)

I copied this method from Steve Potts. Start here: 7/8" CS to Dropout | Flickr - Photo Sharing!

-Joel


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## TrailMaker (Sep 16, 2007)

Thanks Joel;

Very sanitary. I'm sure Mr. Potts would approve!


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## ross413 (Apr 26, 2009)

Eric Malcolm said:


> TM
> 
> Looking good now.
> 
> ...


Eric,
Help all you want, please... But you are talking to a guy with a quote of himself in his sig line.

Trail, 
I like the the threads, and you are on your own path and all. But with this crowd I am surprised you have not been given a harder time for not having built about 20 frames by now... Keep up the good work though, and keep sharing.

Not busting balls. Back to business as usual, me lurking...

Thanks Ross


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## TrailMaker (Sep 16, 2007)

What;

You don't like the quote?


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## ross413 (Apr 26, 2009)

TrailMaker said:


> What;
> 
> You don't like the quote?


Its really not a terrible quote. That said, it is a little pompous to have a personal quote with a by line in it in your sig line, and to be all caps happy with it. All good, keep on blazing your trail.

Thanks Ross


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## TrailMaker (Sep 16, 2007)

*Uh... back on topic...*

...after that pointless interlude 

Lesson for the Weekend; Don't settle.

When working through unfamiliar territory, it is sometimes necessary to catch yourself trying to settle for something that will work, -vs something that you know to be good. I was doing OK. I had the wheel in the rear stays and the cranks in the housing. I even had ring clearance! But..... I didn't like the CSs. I was having trouble getting the idea of the SSs. I just did not like the fact that while my hard points were good, what went between them was not good enough. Stop. Breath. Go cut up that tree that blew down in the lawn last week.

Yes, it is an old lesson learned many times._ I can do this, this, and this, and to a very high level. I should be able to do that!_ Despite that familiarity, The Lesson still attempts to elude, and it must be recognized, caught, and overcome. Every time.

Result; What took days to do poorly before took hours this time, and is crisper, cleaner, more accurate, and far more pleasing. Stays with accurate plain-of-bend, better angles, and a different and much more appealing bridge design than before, right off the cuff in the spur of the moment.

Don't settle and don't give in. The wall will crumble.. eventually. :madman: Or... you'll find a door!


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## TrailMaker (Sep 16, 2007)

*Seat Stays... Still*

Hey;

Not having done this before, I am left to guess at a lot of things. Sometimes those guesses - based on other experience - are OK, and sometimes... not so much. One of the things that has me wondering is how folks go about mitering in their SSs?

My guess is that you use the angle information from your drawing and miter the ST end first. Then you miter in the tails to the DO flanges. On the face of it, this seems obvious. Yet, I am not quite certain I am seeing all possibilities for accomplishing this most effectively.

What's your method?


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## Eric Malcolm (Dec 18, 2011)

TM

I have done it both ways, but prefer the S/T route.

Eric


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## RCP FAB (Jun 15, 2011)

I do the dropout end first. With the anvil fixture it keeps everything aligned.


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## TrailMaker (Sep 16, 2007)

LMAO!

PotAYtoe, PotAHtoe.

What I have done is to craft my SSs to fit my full size drawing, mitered the ST junction of these tubes and welded them together to form an assembly. I also have my bridge tacked in place to hold them in position. I might imagine that by doing this I have limited myself to doing the ST miter first and then fitting the tails as I suggested above. In thinking, I can see how this might be a bit limiting. There might be some advantage to having the freedom to be able to move them separately. I guess I figured that doing this more accurately fixed their symmetry to each other and the frame.

I guess we will see....


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## RCP FAB (Jun 15, 2011)

I think you need to post more pics. :thumbsup:


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## dr.welby (Jan 6, 2004)

The way I see it, there's not as much room for variation in fitting the seatstay to the dropout, so I do it first to make sure it's right. But at the seat tube end, I could move that joint up or down within a half inch or so and not care too much.


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## Walt (Jan 23, 2004)

*Do the bridges last*

IMO it's better to do the seatstay/chainstay (if you have one) bridges last to allow you to adjust the dropout spacing - which is almost never going to end up where you want it without some fine tuning (at least in my experience).

I do the seat tube end first and then miter the dropout side, but either way is fine, just do whatever makes the most sense for you and your setup. I do a lot of non-symmetrical dropout setups (offset dropouts, dropouts that are two different sizes/shapes, etc) so seat tube first works best for me - I can then do the individual miters on each stay to get them where I want them.

-Walt


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## Eric Malcolm (Dec 18, 2011)

As a general comment on Seatstays, back in the day (1980's) pre S-Bend, Seatstays were often supplied with the DO slot pre-cut and SS were straight. They fitted straight onto Campagnolo styled DO's on the frame types of the day. So the method was to attach DO end, then mitre to ST, or side of the Lug.

With the S-bend, and different DO's now available, there is freedom to do this either way.

I have found with S-bend in either CS & SS that there is a tendency for them to pull inwards to the frames centre line which requires aligning. This is why it is better to do CS first, then add SS after the re-aligning is done. It is very hard to align both after welding. It seems to me that the heat from welding affects the tube which wants to bend by little, perhaps due a little tension in the steel due to the bending.

This why we add the bridges later, as they are closer to the bends or within the bend.

The bicycle frame is a very simple device, yet there are many challenging influences.


Anyway TM, have fun, enjoy.

Eric


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## TrailMaker (Sep 16, 2007)

Good stuff guys;

Thanks! I may find that the bridge will be coming off and I will be doing one end or another.
I just hope I do not ruin the SSs trying to figure out what works best for me. That is the 
problem with not knowing.... Not knowing you are about to waste some bits, doing it 
wrong.

These are my stays as they sit at the moment. Right now, with all this new info, I am
really vacillating HARD on whether to try the front miter as is or slit them apart and try 
them individually, one way or the other. I guess my thinking was that they were assured to 
be even and flush this way...










So, I had the CS assy. tacked to the ST already...










I love this axle fixture... (Thanks Peter! :thumbsup










The SSs are freaking with my mind so much, I punted. Instead, I picked some low hanging 
fruit... sort of. Other than the tricky double miter at the ST/BB junction, this was pretty 
easy and success was relatively assured.










I made this little doodad to make the double miter easier. It worked like a charm. I did the 
lower double miter first, made it perfect thanks to the doodad, and then walked into the 
easier upper single miter.










































Good day, eh? Sometimes you need to go for the easy ones to keep your momentum up!
-
-
-
Should I weld the ST under their before tacking the DT in place?
-


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## RCP FAB (Jun 15, 2011)

I fully weld the seat tube to the bb shell first.


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## Eric Malcolm (Dec 18, 2011)

Re: Seatstays

I think it would be OK to proceed as is. I presume the weld at the ST end is fully around the joint so if you mitre it is most likely that the triangular shape will remain together in part, so I do not think it will do dastardly things on you.

And YES, do fully weld the seat tube to the BB.

My friend at the LBS tells me that early factory bikes were not done this way due to speed of manufacture and they 'Squeeked' as the pedal pressures worked there flex down there. You're a big Guy, you don't want that.

Eric


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## TrailMaker (Sep 16, 2007)

Good Lord No;

I can't stand squeaks & creaks. One of the reasons I hated to go back to an ISIS BB, but I just could not see dropping the silly coin they want for a 100mm ex-bearing crankset.


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## G-reg (Jan 12, 2004)

*Two things TM:*

I humbly consider the first item a qualified opinion, though maybe a dissenting retro grouchy one:

Use a Phil Wood square taper BB in that big ass 100mm BB. ISIS should have been stillborn. External cups will NEVER be as precisely aligned as the bearings in a Phil shell, that likely goes doubly on frame #1 with 100mm of shell to warp. White Industries and Middleburn make BAD ASS square taper cranks in any configuration you could wish for. The ShimGianTrekAlized Marketing monster will tell you a external crank is eleventeen% stiffer than xxx....You should know better, especially on a Fatbike. Crank stiffness isn't the limiting factor on a bike with big goofy rims/tires/chainstays. I have nearly 10k mi on a 73mm Phil, and pushing 3k on my Pugsley's Phil. In both cases those miles were in crappy weather, with ZERO maintenance....for years. I'll rein in my rant there, I got more if you want it! But after all the thought you've put into trying to insure #1 is not just *a* bike, but a nice bike. Don't dump some compromised ass crappy ISIS BB into the thing.

Slightly OT rant out of the way, here's a unqualified Noob opinion:

I've used BikeCad on both my builds, and the miter templates give me a pretty good starting point for the CS/BB miter. I'll miter the CS/BB joint which takes into account all the important tight clearances around the BB. Then make the CS/Dropout cuts as required to maintain the CS/BB joint/location. Tack everything together. Alignment from there, without a surface plate that amounts to strings/rulers/straight edges/Park FFG2. If it's not pretty damn close it's time to break the tacks and start over. Once the CS are set I'll miter the ST/SS joint, and then SS/Dropout joint to match and tack....check alignment. A built wheel and tire are thrown in early and often to make sure dimples/bends make it from planning to reality properly.

CliffsNotes: Use a Phil Wood 100mm BB, miter the stays to the BB or Seat Tube and make the dropout cuts to match.


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## TrailMaker (Sep 16, 2007)

Man... this is fun!










The stay fixture, propped up on my Palmgren 4" Angle Vise, purchased off of Ebay for the 
princely sum of $35 (10% of new price. It did not look like that when I bought it).










Angle indicated to the column. Wobbler installed, run into true, and set to the miter center 
point.










The deed.










The result.


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## TrailMaker (Sep 16, 2007)

Yesterday at quitin time.










Today at Beer:30.










Right off the hole saw. No fitting or messaging yet. I am getting really stoked here!

As things are working out, the SSs seem like they are going to be very easy to fit in the end, even as an assembly as pictured. Some of that might have to do with rapidly building stay experience, and perhaps some to luck. A little of both will be fine as long as the result is good.

One large revelation came on this day, and it was a process mystery solved. On paper this jig and the frame hard points could not be easier to set up. Of course, this aint no Anvil, and there is some fiddling and checking needed to get things square and true, but by and large it is pretty straight forward. That is why it was particularly vexing to find that the rear CS angle to the ST that I calculated for was not even close when tacked in place.

I went back over everything - drawing and jig - multiple times to no avail, yet it was plain to see that I was way off somewhere, and I knew it was something obvious. So obvious it hid in plain sight. I decided to avoid further frustration and forge ahead using other known parameters to set things right, trusting that it would all work out in the end. In the back of my mind I knew it was going to be a dope slap moment... and it was.

A friend/colleague/mentor stopped by today for a look see. Being that he is a singularly sharp and inquisitive sort, I immediately enlisted his help by way of going step by step through the setup process. I got all the way through when it hit me. :madman: I had made a tiny yet fundamental mistake, and I was caught out by my own design. I had thought it was moderately clever when I milled the inspection slot in the center of my BB fixture base to offset that slot so that one edge was on the exact center line of the BB spindle. Merely line up that edge with the Starrett tape below, and lock it down. Brilliant... IF you remember to spot on the correct edge!

What was supposed to be set on 1076mm was actually about 9mm short of that mark. This explained the rather shallow angle of the stays when tacked in place. Of course, this lightening strike came AFTER the front tubes had been snugly mitered. It took a long time to miter these babies, and I'm not inclined to waste them. SOOoooooooooOO... after all the refitting was completed, my frame will be about 14mm shorter in the Front Center than designed. DOINK. Well... since it had the proportions of a sand rail to begin with, I can loose 14mm in there somewhere and not really notice. Some may argue that, but I'm prepared not to listen. 

Moving on...


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## TrailMaker (Sep 16, 2007)

I keep stumbling along. I've made what I consider some major blunders to this point, but I suppose they are not frame threatening, nor really unexpected. No matter how much fab experience you have, each new realm presents its own challenges that must be recognized, embraced, and overcome. Perhaps what is most difficult is understanding well enough what exactly happened and why, on what step in the procedure began the blunder, all put toward devising strategies for not repeating them.

What I guess I am most amazed by is the extent to which this little tubing moves around. I am used to the big roll cage stuff and how it handles. This small stuff is shockingly mobile when heat is applied. I've certainly learned by bashing my head against the idea, that one should not weld in the bridges until late in the process. I just could not see that it would be that critical, and learned how it could be. Of course it is a nice idea to avoid such vagueries through refined technique, but that comes with time. Let's just say for now that I am fortunate to be pretty beefy and well equipped for the challenges presented by alignment.

One thing that is driving me nuts is the tire. Of course you would like to have the tire in place to check your gaps, but the run out on this thing can be measured with fingers as feeler gauges! I've never seen a lumpier, buldgier blob in my life. Chinese QC, quite possibly. I've already dealt with the closing of the DOs together, and I've got some misaligment of the ST relative to the wheel. I'm hoping the welding of the ST/BB has not sent everything off the reservation, but it is a possibility. I had a previously documented deviation after tacking, and I purposely welded the side opposite that first to hopefully draw it back. Perhaps I was too successful in that regard. We'll have to see.

And so......


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## TrailMaker (Sep 16, 2007)

It's funny...

I've built hundreds of things. I know there is a sequence to things. A necessary sequence. A sequence that makes the outcome far more certain, successful, and satisfying. I don't think it is until I have built the same thing several times that I can overcome the excitement that breeds the impatience that nearly forces me to do things ahead of their time. Can't overcome it. It takes more patience than I have, until I'm at least partially bored with it. Then it is easy to be patient because it is merely repetition and the outcome is not unknown.

Excitement & Patience.


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## modifier (May 11, 2007)

Good tech. Subscribed.


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## Walt (Jan 23, 2004)

*Check your butts!*

TM - I am *guessing* that you've drawn the butt locations on with a marker - and it looks like you're planning to weld in your brace past the end of the butt. Don't do that! You want to keep all your joinery at least ~50mm from the end of the butt (you can do less if you're good about not heating things up too much, I never do less than 30mm or so). Otherwise you're welding to the transition/thin section, which is not going to be good for the longevity of the frame.

Quick question - what size seatpost are you planning on? Looks like oversized of some kind (ie >27.2).

Looks great - and yes, bridges last next time! 

-Walt


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## TacoMan (Apr 18, 2007)

I agree with Walt. Unless everything is straight gage tube, you should be joining only at the ends of the seat tube and top tube. Even if the butt is long enough, the flex of the tube will cause a localized stress point at the welded brace preventing the tube from bowing evenly along the entire length. Why not use a longer seat post instead? By the length of the head tube I guess this is for a tall rider?


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## Eric Malcolm (Dec 18, 2011)

TM

Great work. A good learning curve.

I am not surprised at your trials and tribulations. I have a friend similar in approach to his work and experience as yourself and approaches the frame with modular concepts as you would find in automotive work. But he gets confounded by the heat of the torch... so to speak.

Eric


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## TrailMaker (Sep 16, 2007)

Nope;

Walt, it's straight 035. Remember from way back, I was keeping it simple in that regard. There are enough things to learn without having to fret over my butt(s). You were quite right about the bridges, of course. In honor of that lesson learned (again), and in order to fight off more of those excitement induced mistakes, I have managed to resist tacking the seat tube brace in place until AFTER I have welded the TT fully, at least across the front.

The ST is 1.250 into which I am sliding a 2.8mm shim to use an old Rockshox suspension seat post I've had kicking around since my hard tail days. I figure purists will scoff at the shim thing, but it worked before and it will work here. I figured the seat post would be a good idea on a rigid bike, and it was long ago paid for.

I DO NOT LIKE a lot of exposed seat post. Perhaps it is a result of always having to do it. It has never made me feel comfortable from a strength standpoint, although I have never broken one either. I've always had to get Thompson x-long jobs to get one high enough. This design will very purposely only expose about 190mm of post. As you have guessed, this is a big bike at 1194mm wheelbase, and that is a full 180mm HT you are looking at.


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## TrailMaker (Sep 16, 2007)

*Is it too soon for Glamour Shots?*


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## TrailMaker (Sep 16, 2007)

Well...

I managed to correct the side sway on the ST. I had recorded a .012" deviation after tacking. Since the DT is mitered over a large portion of the ST, as previously discussed, I welded the ST solid yesterday. I could visibly note that the rear wheel and ST were not parallel, and I had the notion this might be from this welding. Ummm... yeh! I had planned to weld it opposite the side to which it listed to bring it back, as it were. And then some. It came back a country freakin mile. Bolted it down to the mill bed, a handy piece of bar stock, and I hauled on it pretty damn hard. Cold set, they say. Downright cruel!

Only one thing is really bugging me right now. My rear wheel is offset slightly, making the clearance gap a little close on one side. It drops right into the jig nice and smooth, even now, so I'm not sure where the deviation lies. Of course I will check the jig for square again, but other than that I will have to search the frame for the problem. it could also be my SS bridge fiasco coming back to haunt me. I'd like to solve for it before proceeding any further. The absolute last thing to be welded will be the DOs so that I can fudge any inconsistencies, if need be. Don't wanna hafta, but.....


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## RCP FAB (Jun 15, 2011)

Wheel dish?


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## TrailMaker (Sep 16, 2007)

RCP FAB said:


> Wheel dish?


Hmmm...

I had not considered that. Probably never would have. Although I know the rear one is not perfectly true, I just assumed they were built properly. I'm far more inclined to think it was me. Won't hurt to flip the wheel backwards for a quick check, eh?

Thanks!


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## teatreetim (Nov 14, 2011)

A 4" tire will need dish for a casette for sure. Try putting a straight edge between the smallest chain ring and the largest cassette cog!


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## shandcycles (Jan 15, 2008)

He means if the wheel isn't dished properly, it'll appear closer to one stay than other. Flipping the wheel will show.


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## scottybinwv (Jun 29, 2010)

Dude that thing is looking sweet!


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## TrailMaker (Sep 16, 2007)

Thanks Scotty;

And all. The rear clearance issue is in the frame, as I suspected. I'm going to try and isolate it to either the jig or the rear triangle. I'm going to guess that the only recourse will be a very slight re-positioning of the right side DO. It amounts to about 5-6mm at the rim, so we're only talking 1-2 at the DO, I'd wager.

I'd prefer it to have been perfect, but this is a pretty small fudge... all things (noob) considered.


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## G-reg (Jan 12, 2004)

TM what are you using for a dummy axle? If one of your dropouts is "clocked" relative to the other it could cause a straight wheel to sit off kilter in pretty much all dimensions. Anvil's dummy's with the D shape prevent that from happening, well worth the investment. *Side Note* Why are D shaped axles more common? I can only think of the old school Ringle hubs...and they didn't exactly fly off shelves.


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## TrailMaker (Sep 16, 2007)

Capital D!

Perfect alignment, at least in that regard.


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## teatreetim (Nov 14, 2011)

shandcycles said:


> He means if the wheel isn't dished properly, it'll appear closer to one stay than other. Flipping the wheel will show.


Read 2012 Mukluk Lineup | Salsa Cycles "millimeters matter". A little bit of dish is a compromise to avoid rub. The OP can always true it but I'd check it out first. I use 135mm rear so have to dish and offset the rear on my bikes. With 4" and 170/100 he might be ok true I don't know.


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## TrailMaker (Sep 16, 2007)

Hey;

I still have not had time to look for the deviation that has set my wheel a little tight on the right side stay clearances, nor have I gotten to measure the actual deviation at the stays. Suffice to say that it is pretty small, in numbers, if not visibly. However, in an idle moment, and for the benefit of those into extreme minutia, I can tell you that for every 1mm that one side of the axle is moved fore/aft in the DO - or 0.35* if you prefer - you get approximately 2.85mm of movement at the widest point of the tire profile. By eyeball I'd wager that 2mm - likely less - longitudinal movement of one of the DOs will fix it.

I've had what I consider to be the brilliant idea to wait until after I weld everything else to fix this. Others might consider that an obvious point.... They've already done this frame thing before, no doubt.

EDIT - This morning I measured the offset at approximately 4.19mm to the right at the rim. That is with my cheap Chinese calipers. My set at home are off by a full .009", so who knows...  There's still a "problem" somewhere, but I am fairly at ease with a deviation like that. Can't wait to see how much everything moves when I weld it.


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## TrailMaker (Sep 16, 2007)

Hey;

I popped the cranks in and set the wheel w/cassette to have a first look at chain line. Holy Shite. Gonna take some pretty serious finagling to get that working. Just from eyeballing it without a chain, I'm going to be adding at least one drive side BB spacer and dropping at LEAST 2 cogs off the cassette. We're looking at 12-14 speeds tops (which is fine by me). Fatguys are used to this sort of gamesmanship, but it's a bit jarring when you've not taken those leaps before.


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## TrailMaker (Sep 16, 2007)

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>....

I was playing around with drive lines and brakes today.

I hung a chain on it for the first time today. Looks like I will be able to get away with using only 1 drive side spacer on the BB, and only 1 less cog on the cassette. I actually wouldn't mind losing another cog just to improve chain line a bit, but I'd have to relieve the tube at the DO joint a little more. Might not be worth it. I'll study my other bikes for comparison. With it being far more critical in this application, I see I've never really studied it that closely before and don't really know how much cross there typically is.

Of course, I do not have the proper adapters in my little stash to hook up the rear caliper. The two I have that work on the front don't on the rear. Since I've got every 6" rotor I've ever removed from my other machines, that's what Fatty is getting... for now. If this thing ends up being fun in the dry, I can see at least a 7 if not an 8 going on the front. All my other machines have 8/7. With the weight and grip, it might be absolutely necessary!

So, why don't the brake companies - well, Hayes, which I use - publish engineering drawings so you had the specs to make the correct choice without all the guesswork?


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## TrailMaker (Sep 16, 2007)

Well...

After a couple of days of looking at various things like crank and chain clearances and the like, I welded the frame up solid today. The DOs still remain open so that I can make further adjustments as needed. I'm nobody's idea of a world class TIG welder, and I'm using the unloved and scoffed at Miller Econotig 180, but the welds are at least serviceable and don't look like cottage cheese on there.

So, now we get to see just how far out of whack everything has gone. I'm sitting here, contemplating the crank fest that likely awaits in terms of setting things straight, and it occurs to me to wonder how others handle this phase?

What are the things you are looking at, how are you measuring, and how are you coaxing things around to where you want them?


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## RCP FAB (Jun 15, 2011)

Pics!

I try to weld the frames so no cold setting is needed. If you do need to cold set it;

Step 1 is to face the bb shell.


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## TrailMaker (Sep 16, 2007)

Hmmm...

Never done it. Maybe the LBS has the tools? They're not in my budget.


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## TrailMaker (Sep 16, 2007)

All Welded, except DOs;


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## Walt (Jan 23, 2004)

*Nice!*

Random comments:

-If you can't face the shell, you can't really check anything meaningful about the alignment. That said, you can get on the bike and ride it - if it goes straight and the parts don't interfere with other parts when riding, it's aligned as much as it needs to be. It's a bike, not the Hubble telescope.

-Following up on that, assuming you do face the shell, you want to do your aligning (by whatever technique you like) *before* you put the seatstays on. Once the seatstays are on, it's very hard to change much without pulling some other part of the frame out of alignment at the same time. And unless you really screw up, adding the seatstays won't affect the alignment. So do them last.

-You need to do some experimenting with your TIG setup and/or technique. You are getting a LOT of contamination there - you should see a shiny rainbow color on the bead, not dark grey. I don't think you'll have any problems (my first frame has welds that look a LOT worse and it's still functioning) but better shielding will help not only with weld appearance/strength, but also will make it easier to lay a nice smooth bead, especially when you graduate to thinner/butted tubing.

Build it up and ride it!

-Walt


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## TrailMaker (Sep 16, 2007)

Yep;

I like all of that, Walt. Very pragmatic. Although the flanges threaded in after welding, I had the BB housing chased at the LBS, and when he installed the facing die, it grazed evenly around the surface with very little cut taken, and so a big cut was not really indicated. Given drive side sensitivity on Fatbikes, I left well enough alone.

I am not thrilled with the welds. As both of us have said, they are serviceable, but not to be envied. I have gotten the rainbow welds before, but it did not happen here. Not sure why. No change other than a small cup. I'll have to play with it.

In any event, I am pretty well satisfied with it. I do not see anything here that really turns me off. Need a reamer for the seat tube. Thought I might get away with it but it needs it. The welds can be better. Process can be improved for sure, but mostly in detail. I'm going to toss it on the post and indicate the ST and HT for square, but I'm not going to get nuts over it.

In the end, it is all solid, there is nothing way out of whack, and I think it will work reasonably well for the task at hand, which is donking around in the parts of the woods that nobody else rides because their bikes won't go there. Ride straight down the creek bed? No problem. No trail? No problem. 5" of snow? No problem.

One very interesting side note. My stupid, pointless, waste of time tubing sander may have a side benefit. For whatever reason, and I don't really know why, the only tube that got seriously sanded on it - the ST - has remained bright and shiny almost like a stick of stainless. The other tubes sanded by hand are variously tarnished and even beginning to oxidize a little. Hmmm... Maybe it was not so stupid after all?

OH... Forgot to mention. 6lbs 10oz. bare. Considering there are over 13' of straight .035 steel there, I think that is pretty reasonable. For reference, an 18" Pugsley weighs 5.6lbs. My seat tube alone is 6" longer than that!


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## TacoMan (Apr 18, 2007)

The welds are overheated which makes them look contaminated, actually the over heating can cause contamination. You were either using too much heat or welding to slow or both. You also don't want to weld too much of the joint all at once unless you have good control of the heat. I have a bunch of close-up pictures on my website, click to zoom, to compare for reference.


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## TrailMaker (Sep 16, 2007)

Yes, TM;

I believe you are correct. While I did not spend a whole lot of time cleaning before welding, and I had the machine set at 52A max, to be completely honest, most of those are not single pass welds. They simply did not look very good to me and so I was passing over them a second time to flow them out a bit. Some of it is down to looser miters than would be ideal in some spots. A lot of it is simply not being that experienced at TIG in general, and specifically welding around tubes fitments, and even more so in tight places. 

There's only one way to get better at TIG welding, and that's TIG welding. It also helps to have some coaching, which I have never had access to. I do not like my welds on a flat piece of stock in a straight line, but some of them approach reasonable at times. They certainly do not look good around a miter joint. I get in very momentary zones of what I call TIG Bliss where Puddle & Dab hits that magic cadence, but all too soon it is time to re-position to get around the next bend, and the thrill is gone.

For now, I will be satisfied if they are strong enough to work. If I start breaking things apart, I'll be forced to get better, but it will come no sooner without some set up refinement, but mostly simple mask time.

I would love to lay down perfect orbs like some guys I see. I don't think I'll ever be that good, but I know I can be much better.

1st Frame........


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## RCP FAB (Jun 15, 2011)

Word of advise for next time. It didn't matter how ugly or bad the first pass was, a second pass only made it weaker.


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## jay_ntwr (Feb 15, 2008)

Good to see it came together. Looks like it'll be a fun ride.


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## TrailMaker (Sep 16, 2007)

jay_ntwr said:


> Good to see it came together. Looks like it'll be a fun ride.


Thanks Jay;

I'm really looking forward to plonking around in usually unrideable areas and seeing just what this thing can do. Plonking is what I do best, after all.


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## TrailMaker (Sep 16, 2007)

Hey;

I took a bunch of photos of the paint job, and when I went to edit them, there was no bike 
there.  It took me a while to figure it out, but it eventually hit me that I had done 
too good a job on the paint scheme. I had to crank up PhotoShop and play around with the 
contrast and shading to make the bike show up at all!






























Down and dirty rattle can job. Who knows if this thing is even going to work or hold 
together for more than a few peddle strokes, so I did not see the point in getting wild with a 
fancy paint job. Besides, this thing is SUPER easy to touch up if it gets boinked.


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## unterhausen (Sep 28, 2008)

I would tie pink streamers to it so it doesn't get lost when you stop on the trail.

Looking good.


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## Eric Malcolm (Dec 18, 2011)

Hey TM

BIG bike. I mean morphed up tyres and all. The Frame tubes are of a good size to match the wheel proportions. Only the chainstays look as if lacking in substance.

I've been doing some numbers and guess 35-40lbs when ready to ride? Poor snails under tyres when you crush them....

Overall looks good. Reminds me of Sargent Schultz riding out of Stalug 13 on his sidecar motorcycle or this PuddleJumper Suzuki

Eric


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## TrailMaker (Sep 16, 2007)

Ummm...

Certainly hoping for closer to 35... 

Frame is 6lbs-10 bare. Didn't add a whole lot in paint! If all goes well as it is I'll look to do such things as drilling the rims and lighter tubes.


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## Eric Malcolm (Dec 18, 2011)

TM

How are going to tie your cables to your frame?

There appears to be no guides in place.

Eric


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## Drew Diller (Jan 4, 2010)

Run these ****ers for a "light" tube to fill out that fat tire. Saves a total of one pound compared to Surly tubes and can actually fill out an 80mm rim with Big Fat Larry tires (no fooling).

http://www.amazon.com/Q-Tubes-Extreme-2-35-2-75-Presta-Valve/dp/B000G9PN6Q


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## TrailMaker (Sep 16, 2007)

Indeed Eric;

No add-ons of any kind. Frankly, I just did not want to devote the thought to them at this point. There were enough other things that I felt were more important. They are something I was willing to put off until I felt I had a good working design, and that the placement of them would become more obvious to me when I saw how the cables would lie. For now it will be zip ties and good enough.

Thanks a ton Drew! :thumbsup: I was looking at tubes just last night, wondering which of them might manage to stretch enough to fill out those porkers. When I am convinced that the wheels can hold up to whatever abuse I will put them through, I will explore some weight savings. A lighter tube is a good in-the-mean-time thing. Besides... I'd need a bigger pack to carry a spare Surly! Great tip at a great moment in time!!


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## TrailMaker (Sep 16, 2007)

Project Creep;

Details, details.

Reamer arrives, seat tube reamed, cleaned out, rust proofed, and seat assembly installed. BB spacing worked out and cranks installed. Discs mounted. Looking at shifters and cables and hoses in a general way. Never used grip shifters before...

Waiting for longer hoses, caliper adapters, FD and Problem Solver mount bracket, new bars, proper 110 stem, headset spacers, spoke protectors, ring bolts, etc......

I threw on some pedals and took it up a small hill for a test coast. Not enough air in the front tire for pavement. Slightly squirrely steering at low speed because of tire mush. 70mm stem too short and 25" bars feel too narrow now that I've gone wider with my current machines. Other than those correctable items, I'm not sure I've ever been so excited just coasting in a parking lot!!


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## GrayJay (May 16, 2011)

TM- Since you are running a 2X crank (in non-moonlander offset), you might check and see if you can get an conventional tube-clamp mount front derailler to shift out to cover your larger chainring (in middle crank position). On my DIY fatbike, even though the crank is further out, since I didnt use the outer chainring position, I didnt need a problem solver mount bracket for my 2X fatbike, regular tube clamp mount FD was able to make the shift. 

Bontrager 2.8" innertubes also work as lightweigh fat tire option.


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## G-reg (Jan 12, 2004)

I'd recommend the problem solvers direct mount thingy that is oem on Salsa Mukluks. The 2x10 direct mount Shimano Derailleur bolts right up and, most importantly in your case, has an integrated cable mount.


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## TrailMaker (Sep 16, 2007)

*FIRST RIDE...sort of.*

YES, FIRST RIDE UNDER POWER;

In keeping with my penchant for doing things before I should all throughout this build, I made the bike rideable this morning and was cruising around the parking lot and off through the lawn, ditches, over curbs and sidewalks, etc. No front derailleur. No rear brake. A piece of seat tube used as a headset spacer. What cables there are taped to the frame. All while waiting for proper bits to arrive this week.

- It takes a concerted yank on the bars and stiff pedal stroke to loft the front wheel. 1194mm WB, 741.93mm FC, 73* ST, 453.89mm CS. It should have really good leverage derived climbing grip - as a snow bike should - but it will be less automatic to pop the front over obstacles. Of course, the monster tire will mash most stuff flat anyway. 

- When steering, it has a noticeable penchant to tuck the front wheel under on turn-in. I have not ridden it on trails yet, only pavement. This could be from excess trail, but I'm speculating it is actually due to all that tire drag pulling on the fork and trying to spin it around. The trail was calculated at 3.47". Either getting this thing in the dirt will alleviate that feeling, or it would indeed benefit from less trail. The longer bars that are coming (25" now) will certainly help. One thing is for sure, it aint meant for pavement!

- The 32T front ("middle") ring along with the 12-36 Shimano cassette offers what feels like incredibly low gearing, even to a slug like me. Almost seems like I could increase the front a few teeth and still climb buildings. Toeing the chain over onto the granny ring and I'm peddling along at a fraction of a walking pace in 1st.

At least the frame hasn't broken yet. Can't wait to get the rest of the bits and take this thing for a real honk!


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## Drew Diller (Jan 4, 2010)

You're right that dirt will help.

It's kind of spooky, really. Ride from pavement onto pretty much any kind of dirt, and it feels like you accelerate. Turning on pavement at typical riding pressure does feel pretty ridiculous.


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## TrailMaker (Sep 16, 2007)

Thanks Drew;

As an experienced _Fatman _and builder, I value your input.

I continue to evaluate what I have here in little jaunts taken between bouts of actual work. I didn't want to push too hard, as I only have two of the four front ring bolts in place (waiting on a single ring set). I was sitting pretty far back and torquing up a fairly steep bank. The front end didn't even begin to come up, and I think the climbing traction is going to be fairly freakish. I noted something else while cruising around a few minutes ago. I was pushing a little harder speed-wise, even given only a front brake with a little 6" rotor. Speed reveals what seems like a pretty strong gyroscopic effect. "They" say this about 29ers, although I've never noticed it on mine. I do on this thing. Moving the bars around at speed does not encounter resistance so much as a weight like one feels with a top spinning in ones hand.

The familiarization process should be interesting. Wonder how many times I will finger trigger the grip shifters?

Now that I am at that stage, I sort of wish I had given some thought to cable stays. At least it will be easy to tell exactly where I want them this way!


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## TrailMaker (Sep 16, 2007)

So...

Fleshing out a previous thought. My understanding is that Fatbikes are designed with longish stays to create a more substantial lever moment that increases rear end bite for traction. If it does play out that this bike does require some serious effort to loft the front wheel, and one sought to create a more year round friendly trail bike geo, what would be the revisions you would pick to accomplish that?

I can think of two things that might work. #1 would be shorter stays. #2 would be less incline on the ST. The latter would be quite easy, but I'm unsure as to its effect compared to #1. The former would start to force me into things like dimpling for clearance around the tire/rings.

It occurs to me that a rear-set seat post would be an easy way to gauge the effect of the latter revision.


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## Drew Diller (Jan 4, 2010)

TrailMaker said:


> The former would start to force me into things like dimpling for clearance around the tire/rings.


This problem has bothered the **** out of me.

I've lost sleep over it.

I don't like the concept of dimpling chainstays very much. Lots of bikes do it, so maybe what I don't like doesn't match up much with reality. Also food for thought is the new Surly Krampus frame, have a look see at the chainstay yoke. Also check out the PhatSchtickel. Solid bar.

But fat tires are only getting fatter, and speaking from experience, my knees enjoyed an 83mm BB shell more than they enjoy a 100mm BB shell. I'm doing all right this year on 100, but I'm running short (160mm) cranks.

I'm not saying you should do the following, but the only solution I've come up with to shorten the chain stays and fit all that rubber is to have "chain"stays that completely clear the radius of the crank path. Super elevated chainstays.

But, those frames (tend to) break.

A single-strut rear, short stay rear could be reasonably realized in the form of a full suspension frame...


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## dr.welby (Jan 6, 2004)

TrailMaker said:


> My understanding is that Fatbikes are designed with longish stays to create a more substantial lever moment that increases rear end bite for traction.


You might want to sketch that out, looking at which way the mechanical advantage works.


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## Drew Diller (Jan 4, 2010)

dr.welby said:


> You might want to sketch that out, looking at which way the mechanical advantage works.


I glossed over that part. He has a point.

I'd argue that fat bikes have long chain stays for even weight distribution in soft surfaces. The tire that tends to punch through crust is the rear.

I have a frame with freakishly long 19" chain stays, but didn't get to test it adequately in snow due to the unseasonably warm winter last season.

So far it's awesome on sand. But, previous fat bikes I've tried were also great on sand. So I won't know til more snow.

As far as mechanical grip on hard surfaces, the tires are ridiculous and that is generally enough.


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## Eric Malcolm (Dec 18, 2011)

WOW, someone mentioned E-stays?!?!

Only way to go for a Fat-bike for a short chainstay.

Breakage? Only the money making quick buck bikes had breakage issues. The well thought out and engineered ones did not (Gecko) I mean, do you expect a rigid bike with a bolt on rear end not to break? Study the frames more closely and you will discover the weakness in the designs, and the inappropriately thin walled tubes used in the wrong places and you will answer that question.

Make one correctly and you won't break a frame and it will make Fat bikes with shorter chainstays without severe contortions to them achieve a good set-up.

Eric


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## TrailMaker (Sep 16, 2007)

Getting real close. FD & Problem Solver mount arrived Wednesday. That was easy. Got the brake bits. Rebuilt the rear caliper, installed new (longer) hose, IS adapter bracket, and got the rear brakes hooked up. NOT impressed with the bleeding procedure (first time ever on a bike!), so I abandoned it and did it my way. Worked much better. Real spacers for the headset instead of a scrap of seat tube. Crud Catchers are pretty slick, especially the rear one. Front one not so much, but other than somewhat marginal mounting scheme it looks very functional. Not that there's much mud around this year!

Still no cable stays, but it is far more obvious where they need to be now. Need to install the longer front brake hose. 27" handlebars were back ordered, but these are OK for now. The 100mm stem seems a little long, but happily the one I just got is a 90. Hopefully a first shakedown ride tomorrow with my 13YO nephew going on his first MTB ride on my girlfriend's KHS.

*So, no one knows which would be better to make it loft easier; shorter CS or slacker ST?*


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## Eric Malcolm (Dec 18, 2011)

Hey TM

Looking at the picture, Your seat appears to be 80-90mm behind the BB. For your height, efficient pedalling. You sit high and up right, so your weight is more to the rear of the bike. Shortening the chainstay by 40mm would bring the pivot point forward for easier lift, but only acheivable by going to E-Stay. The front wheel I guess will weigh 6lbs? and is more likely to be the limiter here. It is more likely what goes with the genre than anything you can alter with the bike.

It looks quite well balanced to me. Plough on.

Eric


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## TrailMaker (Sep 16, 2007)

Plow on, Indeed;

First real trail ride on my favored terrain last night, albeit punctuated by numerous stops to coach/encourage/console my 13yo nephew on his first real MTB ride, and stopping to pick up all the garbage blown down by the rude storm (Tornado WATCH) we had last week. Lots of good cleanup accomplished. Despite this NOT being a smart place to take new riders (FAR too technical), he ended up doing well and wanted to go right back in! Also got a decent taste of what it is like to Fatbike this rough and tumble terrain.

Overall the bike rides very well. It didn't break! I thumped the front rim a couple of times, which on my 26er would have meant an INSTANT flat. As I expected, the 6" front rotor is far from adequate in the more extreme. I pull them equally about as hard as can be, and can lock the rear, but will only slow at a leisurely pace from speed. I was riding at least some of the usual trails (skipped the rudest ones for my nephew's sake). It is interesting that in many ways I did not notice the bike, which is always a sign that things are as they should be, or as you subconsciously expect them. I was torquing along in the usual gears, which means the weight is not an issue. The balance was very good, and although it does get a little bouncy if you are sitting, overall the big tires make for a good suspension. Not a single pedal strike or touch on a technical roll-over, which is a HUGE improvement over my RIP9. I'd forgotten how nice ground clearance is.

Other than the sound of the monster tires roaring at speed, there is only one issue that I am trying to sort out in my mind. *I hope that some of you experienced and technically gifted frame dudes will weigh in here.* I'd prefer this help rather than building 3-4 frames to find out for myself. I have no Fatbike experience, so I cannot tell if it is typical or not. Posting on the Fatbike forum first yielded no specifically useful info, unfortunately.

The steering is a little strange. It functions well enough in general, but there is an odd characteristic that I can only speculate about. As best I can describe it, there is a pull on the bars off-center that feels as if it will create an automatic bar spin if I do not counter it. It is not a wheel flop that I would associate with a long trail situation. I had a chopper when I was a kid, so I know what that feels like. That is the feeling of working against the weight of the wheel flopping, where this is a definite mechanical pull that must be countered by a deliberate push back on the bars. This makes the bike a bit less intuitive and automatic in trickier low speed situations. The first easy ride was done with a 110mm stem and started on pavement. The bike seemed like it wanted to speed wobble. Pretty frightening. Using a 90mm stem made a large difference in this, and I immediately recalled my argument with Walt over the stem length issue. This bar pull is far more noticeable when traction is high. Definitely on pavement, somewhat less on hard pack dirt, and not so much on loam or mud. The 25" bar is nice for our tight trails, but a bit narrow for leverage, and a 27" bar is on the way.

I can think of one definite possibility for this, and it is the substantial scrub of those huge tires gripping and trying to twist the wheel inward. The question is, is this a normal result of having this much tire surface, or is there an underlying aspect of the geo that is contributing to this? I'll include the spec sheet for reference, and mention that other than wheelbase (+1.5"), ST length (+3), and BB height (+.5"), it is a copy of the Salsa Mukluk.


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## Drew Diller (Jan 4, 2010)

Hmm. I notice you're using Husker Du tires. I haven't tried those, though many have. This may or may not apply, but the Surly Endomorph tires that everybody used to use due to lack of options... those things had crazy self steering effects up front. Then the Larry arrived and steering got a lot more sane.

Is the radial cross section of your tire kinda square, or kinda round?


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## Drew Diller (Jan 4, 2010)

Also, I glossed over your claims of rim strikes. I'm lighter than you, but when PSI is low enough for me to do that, front end handling gets really dependent / increasingly sensitive on the lean of the bike.

You might try adding some air pressure. As long as we're talking about firm ground here.


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## G-reg (Jan 12, 2004)

Figure the side knobs on a standard 2-ish inchtire are about 1in away from the steering axis. Make that tire 4in wide and those knobs are ~2in away from the steering axis. So they have more leverage on the system. The Endo's were terrible for this because they had such a square profile, even on the now "narrow"63mm rims. Pretty much all other options have a rounder profile which helps.

The relatively slack ht angles/long trail #'s on the Muk/Pug don't really help with the self steer...they do make the big bikes nice and stable for adventure/snow riding. Not ideal for trail riding. I've always preferred the Pugsleys handling (steeper ht angle/shorter headtube/shorter a-c and lower rake fork). It felt more like a MTB than a goofy adventure bike to me. I think the general "Fat Community" says the Muk handles better, but I blame first impressions from the OG Endomorph Pugsleys for that. An Endo on the front of a Muk would be awful.

If you want to throw parts at it to minimize the "self steer" I'd do one of two things: Go bigger, and use a Big Fat Larry or one of the new 4in tires. That will give you a rounder profile on the front and even more cush. Or go smaller and use a rim like the Large Marge/Marge Lite, which will also create a rounder tire. 

Or give it some time. You do get used to the effort required to counter steer. And when you mindlessly blitz through a rock garden or across a plowed field it will be worth it.

I'm not done with #3, but I'm planning #4 to be a fatbike so we'll see if I can do better than Surly.


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## TrailMaker (Sep 16, 2007)

Now THAT'S what I'm talkin about!

Good stuff guys! Exactly what I had been thinking, but I was looking for some more experienced confirmation. The HD has a very round profile, but it is still 4" wide and running pretty soft. It stands to reason it would add a lot of grip that otherwise is unheard of, and create some level of moment when turned off center.

Now, the question would be which would be a better way of correcting for that? HT angle or trail? HT angle would be much easier, unless you could build your own fork to increase offset/trail. I am a little bit loathe to do a fork, to be honest. Would there be any negative side effects created by either of these remedies?

In comparing the Muk to the Pug, the differences are subtle, but quite possibly real. The Pug is .5* steeper at the HT, 1* slacker on the ST, 2mm shorter in trail, and the fork is shorter by .81". A lower front, steeper HT, and less trail. Hmmmm. The lower front is likely countered by the slacker ST to make the weight distribution similar. That leaves the steering numbers as the substantive difference.

That's how it looks to me. Whatcha think?

-----------------------------------------------------------------------------------------------------------------

As a fairly simple test for the tire scrub, I thought of tossing the wheel/fork off my Niner on there. Although some of the numbers may not match up directly, with its 2.2 tire it should reduce that scrub feel considerably and give a truer feel for the underlying geo.

I am also seriously wondering about buying a Pug fork to test that. Shorter with less rake. Not that much of a difference, but an interesting trial.


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## TrailMaker (Sep 16, 2007)

Additionally;

Below is a reasonably accurate rendering of the standard XL Pugsley (black outline) and the XL Mukluk for comparison.


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## DWF (Jan 12, 2004)

If you feel it pulling more to one side than the other, head tube twist will make the bike self-steer and pull in one direction. It's also amplified by running bigger/wider tires. If it self steers both directions equally, it's just the tires pulling on the steering axis on the loaded side of the tire. Slacker angles & big trail numbers counter this just like it does on a DH bike.


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## TrailMaker (Sep 16, 2007)

DWF said:


> If you feel it pulling more to one side than the other, head tube twist will make the bike self-steer and pull in one direction. It's also amplified by running bigger/wider tires. If it self steers both directions equally, it's just the tires pulling on the steering axis on the loaded side of the tire. Slacker angles & big trail numbers counter this just like it does on a DH bike.


Hmmm...

Interesting. This is the kind of stuff I would not know because I do not have the breadth of experience in building many different types of bikes. I've only built one.

So, this begs the question for me; which is more effective at countering this, trail or HT angle? Is it a combination deal, and do you need more of both? It would be pretty easy to crank the HT out a degree or so. Maybe even less. Surly goes .5* more than Salsa. Is that enough? The bike climbs quite well as it is, and I would not want to mess that up. My slacker Freeride sled is a real bear to try and climb anything with, just wandering all over the place with the front wheel in the air most of the time. Not looking for that, certainly.

This "problem" is not that bad, but it does lend a feeling of slight uncertainty to the front end that you would just as soon do without. Perhaps an adjustable headset would be the best place to start........


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## TrailMaker (Sep 16, 2007)

Hey;

I rode the bike hard for the first time last night with a weekly Wednesday group. Besides all the tremendous attention this thing draws, it is also fun! The steering behavior was present to varying degrees on varying terrain. It is manageable, but in certain circumstances it can put you in less than ideal situations if you do not stay right on top of it. As such it would be nice to mitigate it as much as possible.

I would be interested in hearing specific recommendations for how much trail and/or HT angle might be added to effect the desired result. I think the Angleset idea is a good one in the interim, to prove/disprove any geo theories.


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## TrailMaker (Sep 16, 2007)

Below is a representation of the standard Mukluk geo on the left, and a 1* change on the 
right. I'd be interested in what people think the change in handling - pro & con - would be with 
such a revision.


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## scottybinwv (Jun 29, 2010)

As a fat biker I can say that I like a slacker head angle. The newer prototype frames seem to be playing around 69-67ish. You could try an angleset to tweak it. Also echo what DD said about the tires, Endo=bad Larry=GOOD. 

I posted in your other thread to play with your tire pressures, sounds like you need a pound or so more to me. Of course too much pressure and you will be bouncing and pinballing down the trail.

I know when I clamped my Mav SC32 on my Pugs that it felt better with the longer length of the suspension. Did not help my stand over but I can live wit dat. 

I have been running the latest HuDu tires up front and they have no bad steering traits as long as they have proper air # in them.


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## t0pcat (May 7, 2012)

Was wondering if you tried a shorter stem yet? I have a muk with hudu's and run 9-10 psi in the tires and i weigh 225lbs soooooo


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## Stevob (Feb 27, 2009)

I would have put tyre pressure at the top of my list for causing that steering issue, sounds like it's too low.


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## TrailMaker (Sep 16, 2007)

Well;

The test I developed for setting the pressure in the tires was to rather crudely and uncaringly ride over a curb outside my shop, and if I thumped the rim it needed more air. I added quite a lot, but then the ride got bouncy so in the end I don't really know how much is in there. Doing the feel thing is not very accurate with such a low pressure. Probably should have a gauge.

None of this had a pronounced effect on the steering feel. Even at the higher pressure, if at speed, the pull was still there. Perhaps some of it can be attributed to a gyroscopic effect as speed increases. 

I started with a 110 stem, and the bike almost wanted to speed wobble on pavement. Not nice. Changing to a 90 seemed to help that a lot. I don't want to go any shorter because that starts getting me out over the bars again, which I am right tired of at this point in my career.

One thing I did today was retention my headset. I wanted to make sure it was not dragging. I don't think it was, but having said that, I was able to back it off a significant amount and still have no play in the bearings. The next thing will be longer bars, once they arrive.

Still only crickets on the geometry questions.......


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## TrailMaker (Sep 16, 2007)

UPDATE;

I have been riding this thing pretty hard - as a normal trail bike - for over a month now. I have not necessarily been blown away by it, as many people claim to be, but it does indeed eave an impression on you in many different ways. A perma-grin is starting to form!

The process of letting this all sink in, and some consultations with my guru, have lead me to discover that whoever built this thing managed to create a head tube angle of 71.8* as it sits on its considerable tires, against a proposed setting of 70*. Hmmmm..... I am guessing now that this may be largely responsible for the steering issues.

To reiterate, this has not made the bike at all unrideable. In this instance, I might wonder if the fat tire might actually mitigate the rather large geo boondoggle that the builder managed. Now knowing the numbers involved, I am pretty surprised it works as well as it does.

So, now we get to do more discovery. What was it that caused this mistake? Jigging? Component measurement? Frankly, I'm having too much fun riding it to tear it down for inspection. The next thing to figure out is how to go about fixing it, or whether to just ditch it and build another one? 

More to come...


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## GrayJay (May 16, 2011)

71.8° HTA should get you around 76mm of fork trail, compared to around 89mm for a pug. Did the STA also wander from the design spec or just the HTA? 
My suggestion for a fix would be to add front suspension fork (or build a taller conventional fork) to jack the front end upward by around 40mm and get you to your desired 70° HTA.


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## TrailMaker (Sep 16, 2007)

Hey;

I don't see any way those two angles wandered, given the jig setup. My assumption at this point is that the height of either the HT or DO is at fault. I know of one parameter that did wander, and that was a direct mistake in setup that I found mid way along. I set the BB too close to the HT, but right now I have not discovered how that might have contributed to this discrepancy. At the time I assumed it would simply make my wheel base shorter, and I had room there to spare so I didn't worry about it too much. As I said, I'm having too much fun riding it now to worry too much.

Wait... that's it. I built this to have a suspension fork on it. Yeh... that's it! :skep:


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## Drew Diller (Jan 4, 2010)

Blessing in disguise? My 110mm travel suspension fork messed up the handling a bit on my bike with a 70 deg HTA. Too much flop.


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## Eric Malcolm (Dec 18, 2011)

*Tm*

:cornut::bluefrown: The naivety is bliss


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## TrailMaker (Sep 16, 2007)

You know...

It is rather ironic to think about all the crap I took from so many people about paying so much attention to process, and yet that is exactly what failed here. The truth is that good product is impossible without it.... unless you are counting on dumb luck.


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## bikeabuser (Aug 12, 2012)

TM,
I'm digging on it, and appreciate the effort to graphically document your procedures :thumbsup:


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## TrailMaker (Sep 16, 2007)

bikeabuser said:


> TM,
> I'm digging on it, and appreciate the effort to graphically document your procedures :thumbsup:


Thanks Man!

The Versatile & Intrepid Humvee; facilitating noble pursuits.


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