# welding disc tabs to heat treated cromoly frame



## isa.alp (Dec 1, 2008)

I have an Atomlab trailpimp frame, it has slotted type tabs originally like in the picture but this separate tabs have known problems like causing dropouts to snap, so i want to weld disc brake tabs to the frame. The frame is made of air hardened cromoly, and heat treated after welding. I am planning to make tabs from cromoly and weld it with tig. Would it be safe to weld disc tabs to this frame? I am wondering if welding causes the seatstay to be weaker.


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## scooter916 (Jan 2, 2006)

Not sure about welding and not heat treating afterwards but just make sure to add a seatstay to chainstay bridge to add stiffness to the stays while your at it


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## verticult (Jan 18, 2005)

you will need to add a reinforcement from under the new brake mount to the chainstay. Not to worry on the welding as long as it is done properly. I am assuming you are aware that attaching the caliper to a fixed location with your wheel able to move will be cause some braking issues when it comes to adjustment.


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## Cracked Headtube (Apr 16, 2006)

This might save you some time.









www.bikelugs.com/store/index.php?strWebAction=item_detail&intItemID=91


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## isa.alp (Dec 1, 2008)

Thanks for the advices. Surely, i could put a gusset between chainstay and seatstay, and the tabs i was thinking was similar to the tabs in the picture, so caliper can move a little. But sadly i live in Turkey, and there is not any parts like this sold here. Ordering from U.S. is also would be expensive, best way i could think is making it myself. This way tabs could also better fit and look.

About welding, i heard somewhere that welding to a heat treated frame causes the metal near the weld area becomes very soft and a new heat treatment required for hardenening the metal again after welding. But i am not very sure what metal it is, it could be for aluminium frames,so that is why i asked this question here.


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## verticult (Jan 18, 2005)

yes this is true for both heat treated steel and aluminum. 4130 can be aquired in three conditions, annealed, normalized and hardened. (soft medium hard). recently, manufacturers have been building frames from material hardened after the tubes are shaped, rather than normalized. some also harden the dropouts. 

If you are able to limit the area effected by the welding heat it is less likely that you will change the condition of the material much. Even normalized alloy steel has a tensile strength around double that of mild steel. 

I have owned a few atomlab products, most only lasting a few days. 

what process will you use to attach the part? weld, braze?


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## isa.alp (Dec 1, 2008)

verticult said:


> yes this is true for both heat treated steel and aluminum. 4130 can be aquired in three conditions, annealed, normalized and hardened. (soft medium hard). recently, manufacturers have been building frames from material hardened after the tubes are shaped, rather than normalized. some also harden the dropouts.
> 
> If you are able to limit the area effected by the welding heat it is less likely that you will change the condition of the material much. Even normalized alloy steel has a tensile strength around double that of mild steel.
> 
> ...


I was thinking tig welding, 
do you have any suggestions about welding or should i just forgot it?


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## disease (Nov 27, 2007)

isa.alp said:


> I was thinking tig welding,
> do you have any suggestions about welding or should i just forgot it?


What about brazing something to the frame? Silver solder is very strong, and the low brazing temperature will have much less of an effect on the steel tubes that welding or even brass brazing.

You could design a disc tab with a contoured contact surface that allows it to be brazed. The work can be done by anyone. You will not have to search for a specialized TIG welder.

There must be frame parts suppliers in Europe that can sell you one without expensive shipping costs. I have heard that there are even a few framebuilders in Italy, almost next door to Turkey. Can it really be true? 

Your other option is to put some sort of support under the tip of the disc tab that is there now. If it is true that these tabs break dropouts, it is probably caused by the tab acting as a moment arm, pivoting around the axle. A support under the forward tip of the disc tab would transfer some of the force to the tube. This would share the braking load between the dropout and the seatstay, which is closer to the normal arrangment for rear disc tabs.


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## isa.alp (Dec 1, 2008)

disease said:


> What about brazing something to the frame? Silver solder is very strong, and the low brazing temperature will have much less of an effect on the steel tubes that welding or even brass brazing.
> 
> You could design a disc tab with a contoured contact surface that allows it to be brazed. The work can be done by anyone. You will not have to search for a specialized TIG welder.
> 
> ...


Why not? As soon as brazing do the job. Sorry, i don't really have any experience neither brazing or welding, i supposed that best way to do this job is tig welding but thinking about low temperature of brazing, it is making sense. Is it really could be strong for disc tabs, because i really don't want to ruin this frame.

About disc tabs, yes, i sometimes have my dinner in Italy, you can't have good macaroni anywhere except Italy nowadays. I could check out for some frame builders when go next time  

I also think of not to weld or braze, simply fixing disc tabs to the seatstays like in the picture but i couldn't trust this solution, it is a temporary, not good looking and have some issues with wheel removal.


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## isa.alp (Dec 1, 2008)

so i think the real the question is, how high we can heat steel avoiding damage to heat treatment?
I would be much appreciated if anyone can help me with this.


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## verticult (Jan 18, 2005)

isa.alp said:


> so i think the real the question is, how high we can heat steel avoiding damage to heat treatment?
> I would be much appreciated if anyone can help me with this.


the only correct answer is " you can not heat metal enough to weld it without changing it's conditions" the answer you need is "a skilled welder/fabricator can weld this to your frame without causing eventual failure at that joint".


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## isa.alp (Dec 1, 2008)

verticult said:


> the only correct answer is " you can not heat metal enough to weld it without changing it's conditions" the answer you need is "a skilled welder/fabricator can weld this to your frame without causing eventual failure at that joint".


Thanks for all the help , there are many skilled welders/welding companies in my city, but i don't think they have any experience with bike tubes. So i decided to take my chance with brazing first.


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