Welded sealed tub/drum bearing replacement - options for fixing it back together

I'm attempting a bearing replacement on an Electrolux/AEG washer. The complete tub+drum assembly is circa £200, and the individual bearings and original AEG seal are about £25 for all three parts.

I thought I'd share my thoughts on this in case it's useful for others...

A viable repair must be water-tight, and mechanically strong enough to withstand the forces on the drum whilst the washer is in use.

It must withstand the full temperature range that the tub will operate at - from not much above 0℃ when filled with cold water in late winter to 60℃ or 90℃ depending on the hottest program the washer has, (in any case it's best to assume this will be 100℃ near the heating element).

It must also withstand chemical attack from washing detergents, bleaches and cleaners.

There are three strategies for fixing the tub together:

Place a watertight seal between the two halves of the tub, and use another method of fixing to keep it mechanically compressed, and to hold both halves of the machine together.

A weld (jointing both halves by melting the material that the tub is constructed from to fuse both halves into one).

An adhesive (glue) join.

For the original construction, all manufacturers use one of these three strategies. If your machine uses "1." then no problem, buy a new seal for <£10. The other two are known as "sealed tubs", and rightly cause much gnashing of teeth and agitation for right-to-repair legislation.

I'm trying to repair a tub with a welded joint, but most of the below will also go for a factory glued joint.

The repair attempts I've seen online for welded and glued tubs have all involved cutting open a welded or glued tub along the joint line, and then used the first strategy - e.g. applying silicone sanitary sealant compressed by bolts which have been drilled through the joint flange (the flange is the flat bit of plastic which stand out at 90° from the side of the tub along the line of the joint to increase the joint area).

I decided not to try a sealant + mechanical fixings because:

The sealant won't stick well to (most?) plastics used for tubs (see below).

The tub will have to cope with the concentrated mechanical strain at the fixing points. It hasn't been designed for that, so doing this reliably sounds like a significant challenge.

Some other tub designs might make this viable, but I decided my tub probably couldn't be reliably repaired like this.

The plastic used for most tubs is Polypropylene ("PP" - commonly used for car bumper, and microwave cooking containers). The advantages of this material include very good chemical resistance, reasonable strength at 100℃, and good resistance to the repeated stresses caused by vibration. Dirt doesn't stick to it very easily either.

I've done some plastic welding in the past, and if you're sufficiently skilled at this, it would work. You would need the necessary equipment (temperature controlled hot air gun, and some polypropylene filler rod) and working around the fixing points on the tub (e.g. for the dampers) might be tricky.

That leaves gluing the tub back together.

The challenge is that PP is a difficult material for glues and sealants. Its chemical composition and small scale structure makes it hard for them to get a grip on it. The only common plastic which is harder to stick to is PTFE - the original Teflon™.

To glue PP, you can:

Use a specialist adhesive which is designed to work with PP.

Modify the surface to adhere better (using a chemical "adhesion promoter", an oxygen-rich (lean) gas flame, or a plasma).

A neighbour gave me a scrap tub which I did a few quick tests on, and getting the flame treatment to work well is very fiddly - if you get it wrong you can actually make it worse.

Using some aerosol brake cleaner actually worked pretty well as an adhesion promoter for an MS-Polymer sealant that I had (I stuck some bits of wood to it, and when I forced them apart, the join failed where it touched the wood instead of the PP). The brake cleaner was a light petroleum-only type - without any other more aggressive solvents that some brands have - I used this because that's what I had at hand, but it's possible the more aggressive brake cleaners would work better). Whilst this is probably a lot better than just sanitary silicone, I still think it'd be a bit risky without extra mechanical fixing.

I'm currently planning to use a specialist glue which has been formulated for PP (a methacrylate based one - a bit like Loctite), I think it'll be good enough for chemical resistance, and temperature, but if you use a lot of laundry bleach that might change that assessment.

I'd be interested to hear about anyone who's tried this. If I decide to go ahead, I'll probably glue it up in the next couple of days, and I'll report back in a few months if it's holding up (or sooner if it fails before then).