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Wishbone Welding - Bearing Bore 'Heatsinks'?

43655 - 6/11/17 at 01:14 PM

Hi all, fabricating some wishbones soon, outer end is to take a 3/4" spherical and inner end to take OEM sealed spherical bearings (Saab/GM rear axle bearings, huge and heavy but IMO doesn't impact unsprung mass)
Anyway, while I can use machine tools here in work, I'd much rather machine to size on the lathe, then weld up, thinking of using a to-size heatsink/fake bearing in place during welding & cooling.
Any thoughts?
Steel for strength or aluminium for heat-shedding?
I know I'm not the first to do this but struggling to find any results via google currently...

loggyboy - 6/11/17 at 03:37 PM

Pictures dont work for me.

bart - 6/11/17 at 03:55 PM

well here we go

1) the correct way to do this is make a bush with the correct id for tube , bush has to have an internal slow taper hole say 10 to 15 deg inclusive
then make an male taper pin to go inside to match . cut bush in half , put bush in tube drive tapered male pin into bush to tight snug fit , weld up arm , cool down, knock out tapper male pin . easy lemon easy , will stop most of distortion , oh turn a top hat lip on the bush for location.

well that's the engineers solution used on welding fixtures , don't forget small slot for flash inside tube if using erw tube .

2) alternative make a pin about 2-4 thou down on tube id ( slot for flash ) turn end down so that when you hammer it out , and you will do ! it wont affect the working diameter.

3) weld it up without and ream it out afterwards

mark chandler - 6/11/17 at 07:49 PM

I machined up some threaded inserts for the tube, drilled a couple of holes to plug weld and fish mouthed the end, hammered them in weld and cleaned up the threads afterwards with a tap, no point trying to remove heat from the work with a heat sinkas it's not that precise.

1/2" UNF rose joints, strong and cheap, 3/4" tube for the lower bones.

Because I went from standard bushes on the frame I used the original mounts with dislocation bushes either side of the Rose joints, making new I would turn the brackets on the frame 90 degrees and fitted the the eye of the Rose joint.

[Edited on 6/11/17 by mark chandler]

907 - 6/11/17 at 09:26 PM

quote:
Originally posted by 43655
Hi all, fabricating some wishbones soon, outer end is to take a 3/4" spherical and inner end to take OEM sealed spherical bearings (Saab/GM rear axle bearings, huge and heavy but IMO doesn't impact unsprung mass)
Anyway, while I can use machine tools here in work, I'd much rather machine to size on the lathe, then weld up, thinking of using a to-size heatsink/fake bearing in place during welding & cooling.
Any thoughts?
Steel for strength or aluminium for heat-shedding?
I know I'm not the first to do this but struggling to find any results via google currently...

If you use a fake bearing, then weld, you will shrink the machined surround onto the bearing and not be able to remove it.

Paul G

coyoteboy - 6/11/17 at 10:49 PM

Wet towel? Worked for loads of stuff for me but maybe I'm not seeing the difficulties here.

43655 - 7/11/17 at 08:17 AM

Bart, I really like the sound of your solution, very properly engineered, I shall see if we have anything to make tapers with here...
ERW yes probably, but has to be machined out slightly to take the 45mm bearing!

Hmm rose joints on the outer end of the wishbone? Nope.
Will be a much beefier design than that, 1 1/4" tube, 1.37"x 0.75" spherical bearing.
My upper control arms will be threaded inserts with rod ends though, probably 12mm.

Hadn't considered struggling to remove the insert post-weld.
I think I'll try TIG welding small sections at a time to try and reduce distortion

Wet towel, what over a fresh weld? I'm skeptical about quenching a weld due to localised hardening possibility?

Thanks so far all

43655 - 9/11/17 at 04:14 PM

Also, sort of on topic, what do people do about protecting components against corrosion?
I've been considering using 304 stainless for the bearing bores on both ends of the wishbones, although I'm not over the moon about the idea from a strength point of view. the inner bearings are huge though, would probably be fine there but I'm worried about the outer end with the spherical bearing in tension. Will probably use EN8/1040

Zinc passivate doesn't seem to last very well, I would expect the fitting of bearings to scrape it off the surface.
Nickel?

FuryRebuild - 9/11/17 at 05:03 PM

I get mine plated. Looks nice and shiny as well.

coyoteboy - 9/11/17 at 11:09 PM

quote:
Originally posted by 43655

Wet towel, what over a fresh weld? I'm skeptical about quenching a weld due to localised hardening possibility?

Thanks so far all

No, not over the weld, near it and around any surfaces close. As the steam flashes off you keep the surface temp in low hundreds except at the site of the weld. If you let it heat right up and then drop the cold towel onto the weld then sure you'll cause excessive contraction and quenching. Has worked on a number of things I've done but it's not a proper solution, it's a workaround with negatives.