Brazing old exhaust

[kelsham]

Hi all, I am trying to repair an old exhaust off my 1932 BSA Trike. It is the shape of a rams horn and fits the twin cylinder Vee twin. It has two ordinary flanges that are brazed into position. They attach to the individual cyllinders. The pipes sweep round and enter a cast lug where they are joined.

My problem is that the cast lug is leaking where the pipes enter. The old braze has cracked, probably due to vibration.

Can I just reheat and melt the old braze, then add new bronze to the joint?

I am concerned that I may have to dismantle the joint as I will then need to make a jig.
I have Mapps gas and oxygen available.

Regards Kels.

 

[mike os]

should be able to rebraze the joint withoug disassembly, assuming you can get it hot enough

 

[chunkolini]

as Mike OS suggests, though will Mapp gas be hot enough?
the joint might need cleaning before rebrazing, this sounds like a job for the pro's.
Sounds beautiful, can we see some pics.

Chunko'.

 

[brightspark]

mapgas with oxygen wont be a problem for heat . but as u say clean the joint well use plenty of flux and build up with brazing rod

 

[mike os]

deffo on the pics

not used mapp & o2 on an exhaust..... all i recall is they loose heat fast

 

[hotrodder]

While the max flame temp is lower almost all of the acetylene alternatives produce more heat energy. Max temps and heat distribution (inner/outer flame) here... http://www.twi.co.uk/content/jk49.html

If the oxy MAPP is in the form of something like the rothenberger kits you might struggle due to the torch size, depends on how heavy wall the lug is.

 

[casement]

You may want to make some tiny, discreet punch marks or similar so you can realign the parts if they move during brazing.

 

[kelsham]

Hi, I have made a jig up to hold the three flanges in the correct positions. I have heated the flange up and begun to clean out the old braze, harder to do than I thought.

Is the general conscensus that I will get away with reheating the flange and applying more brazing rod to it?

Sorry about the lack of pictures I have not got the technical know how to post any.

Regards Kels.

 

[Paul.]

Sorry about the lack of pictures I have not got the technical know how to post any.

Uploading pictures is quite easy, have read through the tutorial here http://www.mig-welding.co.uk/forum/showthread.php?t=5016

 

[mike os]

no need to remove teh old braze unless you need to remove the part, just clean off any corrosion & away to go.