Welding Tips and Tricks

These item are the crown wheel and hub from a BMW motorcycle.
The silver bit is the new hub and I cant tell if its stainless or a bright steel.
The crown wheel is whatever type of steel crown wheels get made out of.
Now I have NEVER heard or seen a crown wheel being welded to the hub before, this type is ensuring a complete rebuild and reshim when ever the wheel drive teeth on the hub wear out. Yes the Germans taught the Japanese everything they knew.
There is a shop in England that replaces the hubs, but dont do it if you live outside the UK.
They cant tell me what the material of the hub is made from and only that they use "normal" steel mig wire to replace the weld.

So over to the gurus.
My TIG skills are in serious need of a brush up, which I'll do before I go anywhere near this. I'm thinking TIG as the weld was only around a 1/8 " bead and I can possibly use a stainless filler to join these 2 bits together.

Old and new hubs



Crown wheel


Pressed together


The bead is required around the shiny lip on the inside of the crown wheel, where the bevel on the hub meets it.
Sorry no arrows I a pc klutz.
Any advice you guys can give would be much appreciated.

If 70S mig wire works you should be fine with 309 stainless.

I use 309 a lot on old "metric" motorcycle frames where they "laminated layers together".
With all that trapped rust and contamination you constantly fight porosity with 70S wire.
Switching to 309 seems to control that and the tensile strength is still comparable.

Hmmm

Assuming you can weld it OK, what methods will you use to get it to run true?

Given the damage that has occurred, I think keeping axial and radial concentrically aligned will be quite challenging. The crown-wheel run-out will probably need to be within only a couple of thou (0.002"). Otherwise there will be tight and loose mesh points.

How much backlash should the mesh have?

You might work around this by building up both surfaces separately, getting each part running true and machining leaving an interference fit, then press the two parts together, check alignment, tack in multiple places, then weld.,

Trev

You probably need to run it hot and fast so that the heat doesn't soak out to the teeth. Gears are usually made from a 8000 series steel. I don't know what the hub would be made from.

Trev,
They are about a 5 thou interference fit, even with the hub at -18 C and the crown wheel at 120 C it took 4 tons to press them together.
I have yet to check for runout but will be doing that before I weld it. Backlash is between .006 and .008"
The hub is new and I assume square at the mounting flange, hopefully it will have minimal run out.
Multible tacks then weld is in the plan.

Rake
Thanks for the tip, I'll see if the LWS has any 309 stainless.

Thanks guys.