Welding 35 VH chaincase

[ian.scott]

Hi
I found part of the chain cover on the inner chaincase had broken on my 35 VH.
I tried to get it welded but the ex F1 and Moto GP welder couldn't repair it . Every time he finished the weld it cracked away from the chaincase as it cooled down , even after preheating it.
Has anyone else welded a chaincase ok ?

Ian

[Vincent.vanGinneke]

Alloy saturated with oil can be a pig to weld.
Maybe heat it long enough in a stove/kiln to burn all old oil away, this can take a long time.

[ian.scott]

It can't really be saturated in oil - it is a chaincase which never keeps much in for long !
I realise that may be the case but it seemed very clean inside and wasn't a problem to weld but every time he took the torch away , there was a ping and the weld cracked away from the main casting.

Ian

[Bob.Murphy]

it seemed very clean inside and wasn't a problem to weld but every time he took the torch away , there was a ping and the weld cracked away from the main casting.

It sounds as though the coefficient of expansion was different between the case and the weld metal. Was he using TIG, MIG or Gas ?? Different types of Alloy rods are available but drums of MIG wire can be an expensive option if you need to experiment.

Bob.

[ian.scott]

He has been a fabricator for Renault F1 and Roberts Moto GP so I assuume he knew what he was doing and he builds custom bikes for a living. I think it was TIG welded . I would agree about the different rates of expansion but he said immediately he stopped welding, before it had time to cool down it would crack. I have now sealed it with araldite and will try making do with that, and perhaps look for another case.

Ian

[paul.jameson]

Assuming you have a 3 bearing crank 1935 VH then the inner chaincase should be the same as that used on all subsequent singles up to introduction of the swinging arm frame.

[john.whiting]

I suggest you take a vintage bike part to a welder who is experienced in vintage bike parts........I have had personal ,working ,experience of specialized welders.....F1,aviation,etc,and they didnt have a clue outside of their square,nor were they interested..........Ive taken parts to several bike specialists,and never had a problem,apart from the fact that some charge way more than others....ask around before you are landed with a 100 quid bill....

[nevhunter]

It can be done if preheated and cooled carefully afterwards. 5% silicon is usually OK. You can even weld this stuff with Oxy and flux but TIG is better although the heat is more intense. Cooling is where the problem arises, if you just withdraw the heat and do nothing else. (especially in the centre bit where the footrest goes through.) The rubbish floats to the top in the weld melt. Nev

[brenton.roy]

If it is in danger of ruining the chaincase, it might be worth using lumiweld or similar.
Lumiweld flows at a much lower temperature. https://www.youtube.com/watch?v=IPfb5eSY9yo
It's not invisible though - which might not matter in your situation.

[ian.scott]

I think I will try and find another chaincase and use that while I try re-welding the old one which is the original.

Ian