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7075 Crush Tubes, Acetal Bushes
43655 - 20/9/15 at 08:55 AM

hi all,

I am planning to use 7075 bar for my wishbone 'crush tubes', or possibly 6082 but I was concerned about deformation.
Has anyone done this before? Any issues?
My thinking is the only load is compression of the bolt within it which can be a locking nut, so not massively torqued up either (M12 12.9 bolt, A4 nyloc nut)

Bushes would be Acetal (Delrin) self lubricating plastic, 19.1 ID pressed into 1.25" seamless tube on the wishbones

redturner - 20/9/15 at 11:50 AM

I use Acetal in all the lower wishbones on my single seater, nice to machine and cheap of course.......

43655 - 21/9/15 at 10:20 AM

yeah we use it in work quite a bit.
not seen it used much
Fallback would be machining some Poly bushes, fitted with sintered bronze bushes inside for slight cushioning and self aligning

Ian-B - 21/9/15 at 06:25 PM

Used acetal bushes with 2014 crush tubes without issue on the race cars, several seasons completed, greased the joint to prevent binding from corrosion.

redturner - 21/9/15 at 07:02 PM

Absolutely essential to make sure the tubes have grease, 'cos if they sieze to the bolt, Oh dear.....

Ian-B - 22/9/15 at 06:57 AM

The comment above suggests I wasn't clear enough, the grease is only between the tube and bush, it should be avoided on the end faces, as the tube needs to be locked by the bolted joint and not rotate. The purpose of the grease is primarily to prevent the corrosion of the outer surface of the tube due to very active nature of 2xxx and 7xxx aluminiums and the creation of crevice corrosion due of the geometry of the bearing.

redturner - 22/9/15 at 07:04 AM

Yes we know that and I will repeat, you do not want the through bolt siezing to the tube, which as you say is locked. But it does rotate around the bolt. I have recently done a rebuild and found that one was siezed and we had to hacksaw it out. Dont want to be doing that too often....

40inches - 22/9/15 at 07:57 AM

quote:
Originally posted by redturner
Yes we know that and I will repeat, you do not want the through bolt siezing to the tube, which as you say is locked.But it does rotate around the bolt . I have recently done a rebuild and found that one was siezed and we had to hacksaw it out. Dont want to be doing that too often....


The tube should be locked against the mounting brackets, the bush should rotate around the tube.

43655 - 22/9/15 at 09:48 AM

I had intended to have it anodised, from a bit of research it seems to be a bit of a pig to do right!
Maybe 6082 would suffice, just didn't want it deforming under the compression load really.
Dimensions would be 12mm ID 19/20mm OD