TOPIC:

Nice job JCW

Great thread! - pretty soon I'm going to have everything off my frame and I'm considering doing some bracing at that time.
I don't have cheap access to a TIG - I can MIG, but I get that it could cause issues.
Would brazing be strong enough? That to me is probably the most accessible way of doing this, but if it's not strong enough there's no point in doing it.
Thanks
Iain

Mcgoo wrote: Great thread! - pretty soon I'm going to have everything off my frame and I'm considering doing some bracing at that time.
I don't have cheap access to a TIG - I can MIG, but I get that it could cause issues.
Would brazing be strong enough? That to me is probably the most accessible way of doing this, but if it's not strong enough there's no point in doing it.
Thanks
Iain

Brazing will be just fine, but so will MIG. Since you have access, your could also Oxy-Acetelene weld as well with the right steel rod. Long story short, any weld method will work just fine if you know what to do with the method you use and take the appropriate precautions. The thing about bracing is that you are simply adding ridigity, so in my mind they are slightl less critical joints when compared to actually welding the main tubes together. Also if you are unsure, take some scrap tube that is the same thickness and practice your technique and setting until you are comfortable. I tend to do this when it has been a while between welding, then my vise, big a$$ hammer, and anvil get a working as I try and break the weld. If it doesn't break no matter what I do, I know I am set to burn I the actual pieces. Also, FWIW I MIG'd my frame modifications for various reasons....

Good luck with what ever you choose.

Cory

Mcgoo wrote: Great thread! - pretty soon I'm going to have everything off my frame and I'm considering doing some bracing at that time.
I don't have cheap access to a TIG - I can MIG, but I get that it could cause issues.
Would brazing be strong enough? That to me is probably the most accessible way of doing this, but if it's not strong enough there's no point in doing it.
Thanks
Iain

Norton frames used to only be brazed. I wanted to do it that way just for bragging rights but its my only bike so I did not want to take the chance. I have not used oxy/acl in a long time. My brother has a Cobra Torch which is a much better way to braze. It uses a 1/4 of the heat but does the same job. What ever you do make sure you share your experience and get us some pics.

These poor frames are already so overstressed from the original mig welding ,brazing will not stress the frame the way mig welding does,if anything Id say it may help distress the frame if done properly.

PLUMMEN wrote: These poor frames are already so overstressed from the original mig welding ,brazing will not stress the frame the way mig welding does,if anything Id say it may help distress the frame if done properly.

I have to respectfully disagree with you Plummen- I did extensive lab testing on the metal of these frames in 2008, and there are a lot of issues- but not the welds really. This is what I found in the lab:

1) The metal is extremely "dirty"- lots of contaminates. Lots of silica in it.
2) It is welded tube- NOT DOM. it appears that they oriented the welds to face each other- don't know if this was intentional or just part of the industrial process as they came off the machine- for instance, the swing arm welded tubes, the welds faced each other to the inside. I did not even see the welds, I guess they were so old or something- even after sandblasting. I sure did see them in x-ray though.
3) The pipe/tubing that they used would not pass inspection entities in the US today.

The worst thing about any welding process would be deforming due to heat. Tig obviously would be the better process in that regard. I did my frame and had no deformation at all. I also did mine in a frame jig, locked down tight! I used a mig, and also x-rayed, magnafluxed and even did some electron microscoping and mass spectrometer testing on some bits of my frame. Fun to be in school back then- let me tell you LOL

Cruise,

When you did your analysis, what did you find the main tube wall thickness to be?

Cory

Welding puts stresses on the metal from the heat of the welding,and as it cools it tries to pull in different directions.
Back when I did foundry work I talked to the plant engineer about coming up with a really stout jig to tie a frame together with then shove it into the oven where they heat treated castings .
The plan was to heat it to a pre determined temp for a certain amount of time then cool it down slowly to "destress "
the frame.
Its the same reason they use frame jigs when building a frame to help control distortion from the welding and cooling of the materials.
The excessive heat of the welding also makes the material more brittle,same reason why you should never weld straight up and down the side of a car/truck frame,you should put a step or atleast an angle where the 2 pieces of frame are butted back together.

NakedFun wrote: Cruise,

When you did your analysis, what did you find the main tube wall thickness to be?

Cory

Very thin! Id say it would land somewhere between 14-16g,I make frame braces out of 14g.
With a little practice you can stick weld on these frames

www.google.com/url?sa=t&rct=j&q=&esrc=s&...vm=bv.78972154,d.cGE

This is all good information, but I think many people over think this bracing process a bit. The idea of adding some gussets to help add ridigity to the frame is straight forward and can be accomplished in a variety of ways. One of the keys are to minimize the HAZ to the area that you are welding to prevent a crystalline structure shift in the base metal. Basically keep the good property's like strength and ductility in the alloy instead of making it brittle. MIG is actually good at minimizing the amount of heat that goes into the base metal beyond what is needed for proper fusion. This is one reason why it is the preferred method for repairing HSS sections of automobile frames and subframe. No matter what method you use, you are still melting the base and filler metals together. Whether it is straight up OA heat from flame or through arc welding via stick, MIG, or TIG, you need X amount of heat to get fusion based on material, material thickness, and joint type. Go beyond this and you start to get brittleness, material creep/warpage, and cracking.

Unless you simply apply some hammer blows along the weld seam as stated earlier in this thread, all other relief methods are out of the hands of most builders on here, and most likely not needed for the non-critical joints we are doing through bracing. It is not a bridge that need to have proof coupons tested prior to fabrications.

Per Ram's comments, really the poor quality of the material is the weakest link in all of this discussion. Not saying it is so weak that it is not upto the task of being a safe motorcycle frame, but out of the variables of weld type, gusset material, material thickness, etc in the overal structural integrity of the bike, it is the"weakest link".

I don't want this discussion to intimidate new comers to the hobby and make it out to be much more involved than it really is.

Good discussion though.

Cory

You could shot peen the frame. I looked into it a while ago and found a company that would do a frame for $250 but i ultimately decided it was overkill.

www.metalimprovement.com/shot_peening.php