Framebuilders - tig welded frame. welding order?
Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.
so, i was looking at strong cycles website along with articles on the anvil tool page and they both mention an order for welding tubes.
i was wondering how important this is(i guess its to keep the frame in alignment as much as possible)
and if so, what is a good order?
ive built a few tig welding frames and ive done almost all the welding in the frame jig. wouldnt this get rid of the need to have an order?
01-31-06, 12:01 AM
Most builders will tell you that you should tack the frame in the jig and then weld/braze with the frame free so it can expand and contract while heated. Not sure about welding order. You might want to search on the framebuilders archive, I know this topic has come up before.
this is copied from the framebuilder's list, originally written by Tom Teesdale, http://www.tetcycles.com/
I will let someone else do the lug and fillet....for tig...this is a main
triangle that is tacked
(BTW--for any type of joint construction--finish the joints in this order,
BB, DT/HT, TT/HT, ST/TT. theory is if you are going to build stresses
frame from welding/brazing, have them accumalate at the least stressed
start at the top of the joint between the seat tube and down tube. weld to
the bb then continue quarter way around dt and quarter way around seat tube.
Turn frame over and repeat with the other side.
go back to the first side and weld the back side of the seat tube all the way
to the other side..completes the seat tube.
start at the bottom of the dt on the bb and weld one side up
start at the same point on the bottom of the shell and complete the other
side of the dt. BB is now done
I do the tt and dt head tube joints at the same time.
weld 12:00 to 3:00 on the TT and then the DT
turn frame over and weld 6 to 9 on the dt then tt
turnover and weld 6 to 3 on dt then tt
turn and do 12 to 9 ,dt then tt HT is now done
12 to 9
6 to 3
6 to 9
12 to 3
I am left handed so you right handers might do a different order
12 to 6 on the outside of each
12 to 6 on the inside of each
I always have an axle in the drops spaced just a bit wide
Tom @ TET
You can't use a jig to totaly force out welding stress. Some jigs are alignment jigs, and other jigs are for welding also. Normally welding jigs hold tube runs in multiple places. But even with that, if the welding process isn't done properly as the individual welds shrink they can pull the tubes out of alignment.
The order is basically a way of ensuring that you don't get too far ahead of yourself and leave the most fundamental, most heat input, and dissimilar wall sized to the end when a bad job can't be corrected. So your mileage may vary depending on nature of the frame assembly.
There is also a correct way to weld the actual tubes, which takes the above into consideration and also deals with issues like gravity slump and so forth.
01-31-06, 08:46 PM
I tried to tig weld one frame(mtb) about 8 years ago . I first tacked it in the jig and then welded it on a bike stand, I don't recall what sequence I used but it certainly wasn't the correct one! When I finished the frame had almost 9mm of twist in 36" . It took three of us, two holding the frame down and me with a 8' length of pipe to twist it back into alignment and it still crept back out of alignment a few days later though only about 3 mm in 36". I filed the slot deeper on one rear drop out to align the wheels and it rode surprisingly well for 4 years until I smacked it into the garage door header.
i have used a similar welding order and as i am also left handed, its about right. for the most part it seems like common sense to do it this way (welding the sides that are more critical to alignment first). i came to this by just finding the easiest way to weld the frame together. as far as the chainstays, i weld the inside first. the first frame i built, the drops had too small a gap, so the next time i did the insides first and then the outsides, this seemed to pull the stays outward.
thanks for the insight.
I'd recommend using a dummy axle in the drops when welding in the stays. I think the anvil one's are 3mm wider than the expected spacing to allow for the heat distortion. I use a threaded rod and some nuts/washers I got from the hardware store.
i have a bringheli frame jig and the dropout spacing is exactly 120(or 130 for when building other frames)
so i have to put washers in the drops when welding.
that anvil stuff is good isnt it?
i have the mitering fixtures.
Powered by vBulletin® Version 4.1.12 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.