Mountain bike

admin

First of all, this is my first post here.  I have been a lurker for quite some time now.  This forum is an awesome vat of knowlage!Anyway, I decided I wanted to build a Rigid 29" wheeled mountain bike.  So I bought a Cromo tubeset from nova cycles.  The two main tubes are .9/.6/.9 (mm) butted.  All the rest are also butted tubes.  Thin stuff, in fact the thinnest I have ever welded.  I built a quick jig, and started going at it, after many many calculations/measurements.  Everything was tig welded on my Miller 180.  I also did some brazing as 'body filler'. The tubes inside are automotive hyd. brake tubing for internal cables. Overall it came out pretty straight, and pretty good for my first frame build.  Good learning experience.And I sprayed it with HOK hot rod flatz daytona blue metallic.Last edited by Timekiller; 06-17-2009 at 06:39 PM.
Reply:BTW... Constructive criticism welcome!Do the welds seem to be overheated?  Mind you most of them have been sitting in a garage for about 5-6mo. before pix were taken.
Reply:One note I see, if for any reason you ever need to do a repair, those brazed places will really F with you. I had to redo some "repairs" someone else had done in the past. Unbeknownst to anyone, he brazed the joints rather than weld them as was originally done. I had a he!! of a time getting all the braze off without ruining the original parts beyond use.I do like to blue paint.
Reply:That was an afterthought of mine... but If i do have to repair it, I would replace the whole tube.
Reply:I've rode MTB's for years and have been a PT bike shop emp sporadically over the years and I would like to respectfully suggest that a straight downtube would be stronger and safer. The downtube/headtube junction is a very common failure point in a mountain frame. That's also why we have 1 1/8" and even some 1 1/2  headsets (as opposed to the previous 1") now because the bigger tube allows for a much stronger durable headset and for more weld area. The downtubes you'll see that aren't straight, are usually either hydroformed or gusseted  or both. Cool project, think a 29'er will be my next bike. The Oury grips are damn comfortableLast edited by regularfella; 06-17-2009 at 09:47 PM.
Reply:Wow that is so so cool Did you fab all the tube for the frame and forks or can you buy the pieces? I would love to build one some time so any advice or tips and tricks would really be nice. Do you have any pics of the jig you used? It turned out really nice you did a really good job. How does it ride?
Reply:Looks good, but u need to gusset the down tube, and top tube where it meets the head set, ive snapped 1 and cracked 2 one all differnt bike companys. Also i wouldnt trust that 2 piece down tube. id snap that frame the frist 30 seconds i rode it. what do u plan on doing with it. looks like a street setup. I ride down hill and trails.lincoln weld pac 100Hobart handler 120Lincoln  "BuZZ box"Lincoln Precision Tig 225
Reply:Impressive build.  ^^-- Gusset plate on the front end, good idea.Great color - now I gotta find some of that for my next project ....
Reply:First off , don't say "awsome"!!!!Just a bunch of guys in front of keyboards that give advice that they don't have to live with.I'm feelin' grumpy tonite"Any day above ground is a good day"http://www.farmersamm.com/
Reply:And that doesn't mean the preceding posts are bad, it's just something you have to use your intuition, and common sense to weighLike I say, I ain't in a real good mood tonite"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Sam, no need to get riled up here.  Grab yourself a cold one, go put your feet up, and take it easy for a while.  Don't think about whatever's bothering you, just enjoy the beer and the breeze on your front porch.Last edited by SpyGuy; 06-18-2009 at 02:52 AM.
Reply:I've been wanting to do this for a while. Did the bottom bracket come with the tube kit ?
Reply:Originally Posted by Mega Arc 5040DDWow that is so so cool Did you fab all the tube for the frame and forks or can you buy the pieces? I would love to build one some time so any advice or tips and tricks would really be nice. Do you have any pics of the jig you used? It turned out really nice you did a really good job. How does it ride?
Reply:Originally Posted by beamed94OneFiddYLooks good, but u need to gusset the down tube, and top tube where it meets the head set, ive snapped 1 and cracked 2 one all differnt bike companys. Also i wouldnt trust that 2 piece down tube. id snap that frame the frist 30 seconds i rode it. what do u plan on doing with it. looks like a street setup. I ride down hill and trails.
Reply:Originally Posted by SpyGuyImpressive build.  ^^-- Gusset plate on the front end, good idea.Great color - now I gotta find some of that for my next project ....
Reply:Originally Posted by farmersammAnd that doesn't mean the preceding posts are bad, it's just something you have to use your intuition, and common sense to weighLike I say, I ain't in a real good mood tonite
Reply:Originally Posted by neat-oI've been wanting to do this for a while. Did the bottom bracket come with the tube kit ?
Reply:That  is a great job I to bike and would like to try a frame. Just got a Tig/Plasma need to do some more practice before a proj like that maybe horiz dropout mod on old steel Stumpy.Nice shop area.
Reply:Nice job on the bike.  Nova ( www.novacycles.com )is a great source of framebuilding supplies.  Also, some aircraft tubing suppliers are a resource for tubing.    I hope to get another bike built this summer.  A lugged frame road bike. Is that flux on the internal cable tube. If it is, hope you got it all out.
Reply:not to be overly critical , but comming from a framebuilders stanpoint, you definatly should gussett the head tube, and the brazing over the filler? really? think about how much heat your putting in to the tubset..if you really want to , some use body filler. The welds need practice, for sure, but I give you props for getting after it..just my 2centstry Spruce Goose for cro mo tubingOwner - Certified Welding & Fabrication / 22yrs in businessSteamboat Springs, Co(970) 879-5491AWS structural shopHMI 70t iron worker2 field trucks specailizing in structural steel, aluminum and stainless steel
Reply:Originally Posted by tapwelderIs that flux on the internal cable tube. If it is, hope you got it all out.
Reply:Originally Posted by IH 392not to be overly critical , but comming from a framebuilders stanpoint, you definatly should gussett the head tube, and the brazing over the filler? really? think about how much heat your putting in to the tubset..if you really want to , some use body filler. The welds need practice, for sure, but I give you props for getting after it..just my 2centstry Spruce Goose for cro mo tubing
Reply:Time killer- Props for building your own frame, it looks great. Don't let anyone run down your welds just cause they aren't pretty. They look a little too hot judging by the pictures, you probably went too slow, but that's nothing that a little heat treatment won't fix. I think the kink in your down tube might actually add fatigue strength by straightening the joint at the head tube and allowing the whole system to flex instead of hammer. I can only think of one good way to test it... have fun.
Reply:Originally Posted by fortyonethirtyTime killer- Props for building your own frame, it looks great. Don't let anyone run down your welds just cause they aren't pretty. They look a little too hot judging by the pictures, you probably went too slow, but that's nothing that a little heat treatment won't fix. I think the kink in your down tube might actually add fatigue strength by straightening the joint at the head tube and allowing the whole system to flex instead of hammer. I can only think of one good way to test it... have fun.
Reply:Couple other pics...The frame before any hacking:And the jig I built:The jig is 80/20 T-slot.  I turned cones on the lathe to hold the tubes, a large spacer to hold the bottom bracket, and a dummy axle for the spacing on the rear chainstays.  I also built a separate fork jig.  Its a simple 'L' of 80/20 with a set of dummy axles.and an update on the bike...I took it out for a ride in a mall parking lot.  Jumped off a few curbs, did a couple wheelies.  Nothing crazy. No signs of fracture in the downtube joint.  The bike is so ridiculously comfortable and tracks very well.  Hopefully I will hit the trails next week.Jig is amazing!Hopefully you won´t put much stress on the bike because I would suggest the brace too and stress relieving the bike. Color is great too!Why you didn´t choose some front shocks?Nice project thou  and watch out for small cracks, cromo is very susceptible to those when not stress relieved.My Babies: HF Drill pressHF Pipe Bender3   4.5" Black and Decker angle grindersLincoln Electric PROMIG 175that´s it!
Reply:Originally Posted by elvergonJig is amazing!Hopefully you won´t put much stress on the bike because I would suggest the brace too and stress relieving the bike. Color is great too!Why you didn´t choose some front shocks?Nice project thou  and watch out for small cracks, cromo is very susceptible to those when not stress relieved.
Reply:Originally Posted by TimekillerThank you and... Some others have said my welds need work... but yet no one can tell me why.  Can you suggest a problem/solution for me.  I really want to fix my mistakes because all these years and I thought they were ok.
Reply:Thanks IH 392! Ill try the gas lens, I have one but was using std. ceramic cup. @ 18.  I thought there might be too much heat, but is it from the machine, or should I be waiting longer between welds? I was set between 35-45A max on the Syncrowave 180, using a footpedal. 1/16 tung, and .035 ER-70S-2Update on the bike..I have logged probably close to 30 off-road miles on the bike the past 4 days.  Everything is still in one piece.  The bike tracks perfect, and is surprisingly light (in corners/jumps)  Trust me I have beat this bike the past few days.  Rocky downhills, log hops, jumps (small doubles), rooty fast singletrack, and even a stream crossing up to my knees.Had to ride through a bit of mud yesterday:Last edited by Timekiller; 06-29-2009 at 04:33 PM.
Reply:Was there a reason for the extra bend in the down tube?   I really like the nice simple clean design.  What do you do about water?  A camelback perhaps?
Reply:Originally Posted by tapwelderWas there a reason for the extra bend in the down tube?   I really like the nice simple clean design.  What do you do about water?  A camelback perhaps?