Impossible weld?

[Jacques]

Hi folks,

I spent a year and a half re-building my 1982 Vespa smallframe from a hulk of rust to something very respectable. I even managed to teach myself some MIG welding and replaced the floor on my scoot and a few other bits....

Unfortunately I recently had a bit of a setback...A bearing housing lip cracked inside my engine casing (all Aly) and these casings are are scarce as rocking horse pooh! (They are 125cc ET3 casings...)

Is it possible to TIG / lathe / reform the lip? I really don't want to throw otherwise good casings away too be honest! I suspect the lip would have to be tigged and then the bearing housing lathed down to get rid of any excess weld? I'm not after pretty...just sturdy!

Pics below.

The lip is at 2 o'clock on the top left hand bearing. This is the crank bearing so there is a bit of lateral pressure from the crank and 2kg flywheel.

If it's possible, who would I ask and what should I expect to pay? Suspect this will be some very fine work!!!

And here is my baby!

Any advice appreciated!

Jacques

 

[rtbcomp]

It looks like the rest of the lip is about to come off.

Would it be possible to remove the lip entirely and machine a groove to take a circlip?

 

[Jacques]

I don't think there is enough meat there for a circlip. If you take the lip off there wouldn't be anything to form the groove in...interesting idea though!

Break off the lip, blob on some weld and machine it down???? Or is this wishful thinking?

 

[Shox Dr]

I take it the bearing is installed from the rear, and butts up against the lip, been kept in place by a circlip you can just see in the foreground.


Welding it will not be hard part, keeping the casing, true, and then machining the back again will be the hardest part, but doable

 

[rtbcomp]

.........

Break off the lip, blob on some weld and machine it down???? Or is this wishful thinking?

I should think that would be doable - could you get away with say half a dozen blobs of weld rather than a contiuous run?

 

[hotrodder]

Doesn't look like a difficult weld but obviously you'd want to find someone experienced with ali, particually casting repair. Dunno about where you are but round my way most gearbox specialists can get this sort of work done (i do the welding for three gearbox reconditioners round my neck of the woods, they do their own machining in house). Engine reconditioners will usually know of welder handy with castings too

Break off the lip, blob on some weld and machine it down???? Or is this wishful thinking?

That's pretty much it! Dye pen it, prep and weld, dye pen and machine. Machining (set up) will probably be the most time consuming part of the repair

Are these cases know for failing like this or did a thrust bearing or something let go?

 

[chunkolini]

It's a scooter.
Put it in the canal.

Chunko'.*

*only joking, keeping old vehicles alive is a noble cause even if they are twostrokes.
Jacques you obviously love your baby they are superb photographs.
Another option, there was a maniac in the 80's putting RD350LC motors in scooters. He is probably dead though.

 

[Mephisto]

Can be done!

A couple of things you have to understand before going down this road. First, all aluminum is not created equally! Companies like to make casting that are proprietary and love to mix percentages of zinc to make them almost unweldable. Secondly, the casing has to be completely disassembled. The thermal (heat) transmission to adjacent parts will be substantial. The bare case will have to be prepared if determined to be weldable. It will have to have some ports or deep dimples drilled along the entire lower arc of the crack, if your going to weld it, drill a hole. These will serve to mechanically anchor the weld deeper then the mere surface welding. A form made of copper will have to be positioned and will serve as a mold for the weld to conform to, don't worry, the aluminum will not stick to the copper. Then the whole thing will be placed in an oven and heated to about 700 degrees. Welding will progress in layers and returned to the oven if long periods of down time welding it will occur. Once finished, it will be step cooled for about 24 hours until cool. Then the machining occurs and hopefully you have no voids in the weld that will shatter while milling its surface. Price, whats the casing worth? I know some old masters down some dark alleys that work their alchemy for about $300/400 bucks. A shop will probably not touch it because if it breaks during operation, in the location it sits, your looking at critical failure at the least. Thats a handlebar flip to you laymen.

 

[steeo]

It looks like the rest of the lip is about to come off.

Would it be possible to remove the lip entirely and machine a groove to take a circlip?

I'd look into this idea with the possibility of getting a new bearing slightly narrower than the original bearing thus giving you a little more room to play with if that was possible.

 

[rtbcomp]

A form made of copper Could you use an old bearing instead?

 

[Jacques]

Some super ideas guys, thanks!! Im in Bristol, UK.

If I had to buy new PK casings (which means I'd have to bastardise my frame!!!) it would cost me £390!

The ali is quite weldable as loads of guys tune these motors to insane specs. The casing is completely stripped of all bearings / seals and parts so no problems there. The only thing I would do is pop a bearing in the housing to stop it from deforming. There is a lot of meat in this area but having a copper lug in there may help soak up some heat.

The cases are usually very good, if a bit soft. The issue is this case ali case is 30 years old and has seen it's fair share of transplants.

Thought about another option last night...Get rid of the lip or take 1mm out from the bearing side. Enlare the bearing housing and shim it with a 0.8mm lining and form a lip as part of the shim. Just have to find a way to tack the shim onto the casing so it doesn't move. That gets rid of any welding???

Am seeing a machinist on Sunday morning for some other suggestions...

Jacques

 

[rtbcomp]

Instead of a thin shim, would a machined bush work with a slightly smaller bearing? This would give a meatier lip.

I suppose it could be bonded in place, but I'm not a great fan of glues and potions!

Couild you machine the lip out and make a top-hat retainer held in place with setscrews through the flange into the casting?

 

[piman]

Hello Jaques,

if it were mine I would consider drilling the remaining lip where it is weak and screwing in some countersunk head screws to reinforce it. These will need to be small diameter I guess so helicoil the casing and have the screws at least as long as the helicoil. (consider two?)

Accurately make up some steel clamps to replace the broken section and screw in in a similar manner. It requires careful work but I believe it is a viable option to welding. Thread lock also would be adviseable.

Alec

 

[schnappi]

Hmmm... How about ream out the inside of the case to a larger diameter and then get a steel insert made up which is interference fit. Then press it in cold like you would with a motorcycle head bearing race or hardened valve seat when doing an unleaded conversion?

No welding. Dimensions preserved. Simple machining. Tougher end result.

 

[rtbcomp]

Hmmm... How about ream out the inside of the case to a larger diameter and then get a steel insert made up which is interference fit. Then press it in cold like you would with a motorcycle head bearing race or hardened valve seat when doing an unleaded conversion?

No welding. Dimensions preserved. Simple machining. Tougher end result.

Would there be a danger of it moving when you drift bearings in and out?

 

[schnappi]

Would there be a danger of it moving when you drift bearings in and out?

Possibly a problem, however the bearing looks like it goes in from the inside.

I'm thinking that to fit the bearing you could use a large washer inside and a large washer outside with a bolt through the middle sandwiching the insert and the bearing. Tighten the bolt and the bearing will be pressed into the insert exerting no force on the mating faces of the insert and casting.

When removing the bearing, the insert will not be able to travel further into the hole because of the lip so removal shouldn't be an issue either?

 

[rtbcomp]

Good plan, better than drifting anyway.

 

[backpurge]

Hi mate, good to see a fellow scooterist on here (although I'm more into my Lambrettas), welding the casing isn't a problem, have done a lot of modifications on Vespa engines for guys who sprint them and the alloy quality is usually very good, as has been pointed out the hard part will be the machining but this will just be a case of finding someone with the right equipment. Best of luck

 

[Jacques]

Would there be a danger of it moving when you drift bearings in and out?

I don't usually drift bearings if I can help it. I usually end up freezing the bearing with compressed air and heating the casing very slightly with a hairdryer...bearings drop in no problem. Always follow up with a bit of wd40 to get rid of any condensation and then some gear oil.

Just checked and the existing bearing housing is a bit worn, so may need to get it shimmed in any case And yep, the bearing goes in from the other side and is retained on the crank end by a circlip.

Jacques.

 

[RichardM]

Would I be correct in assuming:
1/ all the casing and bearing locating flange (230 ish degrees of it) are there in the photo and that the flange cracking off is not going through the main part of the cases?
2/ the casing is not starting to crack at 12 o-clock?

Try SEP at Kegworth, I expect they would be able to weld and re-machine it fairly easily, alternatively as already suggested tap the casing and put a small panhead screw in to secure the part of the flange that is cracking off.

Though I do think Chunkos' canal idea does have its' merits as well