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What is the best option? Okay! Second best option?

Repair suggestions please

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Giuseppe Saroli12/02/2018 09:42:44
189 forum posts
247 photos

JB Weld trust me what have you got to lose and you have plenty leftover for more repairs

Also very good to join carbon tube i use all the time just make sure the repair is secured and leave it alone for 48 hours

Good luck

Manish Chandrayan12/02/2018 09:44:44
452 forum posts
56 photos


Having reread your suggestion, I think that bracket idea should be doable. Will fabricate one in brass first to see if it works. If it does I will get one made in steel. That bracket along with the original piece glued in should hold the carb good enough.

The engine is (or was) on a Cub so would not experience much of G forces, and the engine being an even twin has advantage of very low vibrations.

Cuban812/02/2018 09:54:34
2029 forum posts
3 photos

I bought some JB Weld to experiment with rather than getting into proper welding/brazing for a small job. I bonded a length of 1/2" dia aluminium tube to a sheet of 1/8" ali plate (drilled to suit) with JB Weld and was very impressed with the result.

The 'weld' is stronger than the materials being joined and I can't break the pieces apart without bending either.

Only tips I'd give, if you haven't used it before, is to make sure the surfaces to be joined are absolutely clean and free of oil/grease - lightly key mating surfaces if possible and build up as much of a fillet of the weld as is practical.

The joint strength increases markedly with time, so leave for at least a week at room temperature to cure fully, in fact as long as possible.

Manish Chandrayan12/02/2018 10:03:25
452 forum posts
56 photos

Yes have already ordered the JB weld, will take few days to come in. Will update here once I have worked on the engine

Engine Doctor12/02/2018 16:14:21
1991 forum posts
19 photos

Welding the case is hit and miss due to the rubbish alloy used in manufacture.  Techno weld would work ok but be very careful with heat application as any part that gets too hot might cause distortion,sagging or bubbling in the casting.Try the JB weld and then buy a new case  if and when it fails . Check carefully that the impact hasn't cracked or distorted the case. 

ken anderson.12/02/2018 17:23:54
8065 forum posts
729 photos

this thread has a bit of aluminium work on it...check out with the author...maybe he can advise you.

ken ali dept.

Engine Doctor13/02/2018 16:17:46
1991 forum posts
19 photos
Posted by ken anderson. on 12/02/2018 17:23:54:

this thread has a bit of aluminium work on it...check out with the author...maybe he can advise you.


ken ali dept.

Hello Ken. The Mercos featured in that post have a much better quality alloy than the engines of today as did most early British engines of that era. I experimented some time ago trying to repair some broken fins on an old Magnum GP40 case .I just wanted to see if it was possible. I managed to build up the broken fins ok with Techno-weld intending to reshape them .I was very careful with the heat but the air trapped in the case when it was made/molded expanded while heating the case to required temp making the case useless . Some cases are doable but many are made of rubbish pot metal to start with and and I have found that they are just not not worth messing with . A new Crank case costs about £76 but at least he will know that its not distorted and wont fail in the air

Edited By Engine Doctor on 13/02/2018 16:19:27

Manish Chandrayan13/02/2018 16:29:42
452 forum posts
56 photos
Gents I have no intention of taking any heat source anywhere near that case. If it was an OS I may have considered that but not with an ASP.
Engine Doctor13/02/2018 22:50:53
1991 forum posts
19 photos
Posted by Manish Chandrayan on 13/02/2018 16:29:42:
Gents I have no intention of taking any heat source anywhere near that case. If it was an OS I may have considered that but not with an ASP.

I hope you repair goes ok . Even  OS cases are made of an  alloy that is pressure moulded for lightness and  doesnt take well to welding. It's unlike proper aluminium that is easier to weld with Tig,Mig or low temp techno weld.

David Ovenden14/02/2018 08:33:36
323 forum posts
16 photos

Given that the carburetter is partially mechanically retained/located where it fits into the inlet pipe "T shaped" aluminium block, I feel that a JB weld repair reinforced by a bracket is very likely to be entirely successful. OK it won't be aesthetically beautiful, but inside the cowl nobody will see the repair.

Manish Chandrayan19/02/2018 12:42:12
452 forum posts
56 photos

JB weld tubes arrived mid week and having cleaned the parts very well with soap and water, then nitro cellulose thinner and in the end with Meth. Parts were allowed to dry out overnight.

Next morning mixed a small batch of JB weld and applied that liberally on the parts to be joined. Care was taken to see that it did not go in to threads.

The tiny broken part was taped up to keep it mated and in correct position. Tape was removed late in the night when I returned from work and all looked to be in good order. For good measure further 24 hours curing was allowed before handling the engine and the glued part.

Once the glue looked hard enough tried to mate the carb and saw that the glue fillet on the mating side was interfering with the carb body. Having taped the carb plenum to prevent debris the fillet was sanded and the little casting on the carb outer body was also sanded and filed a little to ensure there was no interference. Once done the carb was bolted back. No attempts were made to dress up the glue filled under the bracket .

As of now it looks good. Will mount the engine back and fly the model the coming weekend and see if it holds. From the looks of it, it should hold.

In hindsight I think I can build up a fillet under the bracket after roughing up the existing JB weld, that should provide some more strength   

JB weld repair 3

JB weld repair 2

JB weld repair 1

Edited By Manish Chandrayan on 19/02/2018 12:50:46

Edited By Manish Chandrayan on 19/02/2018 12:52:03

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