Printable Version | Subscribe | Add to Favourites
New Topic New Poll New Reply
Author: Subject: Has anyone made their wishbones from ERW?
adrianreeve

posted on 9/5/19 at 01:20 PM Reply With Quote
Has anyone made their wishbones from ERW?

Hello, just wondering if anyone has made their wishbones from ERW instead of seamless tubing? Looking at the mechanical properties of each, it would seem that either would be suitable? If so, 1.5 or 2mm wall thickness? Would be nice to hear from people with cars on the road to see if there have been any issues.

Thanks very much

Adrian

[Edited on 9/5/19 by adrianreeve]

[Edited on 9/5/19 by adrianreeve]

View User's Profile View All Posts By User U2U Member
rusty nuts

posted on 9/5/19 at 01:55 PM Reply With Quote
There was a spate of wishbone failure several years ago , worth doing a search. There was also issues with the wishbone crush tubes being too short on at least one manufacturer’s items which I think may have been a contributing factor to at least some failures. Personally I would prefer to make them stronger rather than have them fail.
View User's Profile View All Posts By User U2U Member
907

posted on 9/5/19 at 02:03 PM Reply With Quote
Like the old song... Ya knee bones connected to ya thigh bone....


Or.. A ten tonne hook on a five tonne chain...


If for instance you were to use CDS; that is material that gains strength by cold working (work hardening), and then you weld it,
thus changing its crystal structure back to a semi annealed state you have lost most of the gains. (around the weld area)

To carry that a little further into the chassis then your W/B's are attached to an ERW square box frame. (maybe)



Personally I feel that unless weight is of critical importance then better to use a bigger diameter tube or/and increased wall.

My own are 22.2mm (7/8" with a 2mm wall, but still seamed tube.

Paul G





Member of the Suttol Owners Club, the MX5 Owners Club and the BMMC

View User's Profile View All Posts By User U2U Member
Sam_68

posted on 9/5/19 at 02:31 PM Reply With Quote
If you design them correctly (and yes, I know that involves quite a big 'if', then the individual tubes in a wishbone should be in pretty much pure tension or compression, so ERW or CDS should make too much difference, in theory.

In practice, I'd need a damned good reason not to use CDS, though.

View User's Profile View All Posts By User U2U Member
AdamR20

posted on 9/5/19 at 02:50 PM Reply With Quote
Cost?

ERW here, as on all the 7 (quantity, not type) kit cars I've owned, and I'm still alive with all my limbs intact.

7/8" bottom and 3/4" top, 14G all round. Way overbuilt but still much lighter than off the shelf offerings due to sensible design - no huge 4mm plates holding things together and not a transit van ball joint in sight!

[Edited on 9/5/19 by AdamR20]

View User's Profile View All Posts By User U2U Member
Slimy38

posted on 9/5/19 at 03:08 PM Reply With Quote
quote:
Originally posted by AdamR20
Cost?



Same here, it was all cost related. The one thing I did read about (and made sure I adhered to) was to make sure the weld seam was inside the joins. Once I'd finished, there was only a small portion of ERW seam left visible.

Of course, I don't actually know whether welding on a weld is a good idea, the joys of reading random stuff on the internet I guess!!

I've just had a look at what I used, it was 19mm x 1.5mm and 25mm x 1.5mm. The bush outers were made from a length of 33.7mm x 2.6mm. With shipping and VAT that was £50, an equivalent CDS was four times more if I remember correctly.

[Edited on 9/5/19 by Slimy38]

View User's Profile View All Posts By User U2U Member
Mr Whippy

posted on 9/5/19 at 09:58 PM Reply With Quote
Tbh when you see what modern production cars use these days those on a 7 look beefy
View User's Profile Visit User's Homepage View All Posts By User U2U Member   Mr+Whippy 's Aim
steve m

posted on 10/5/19 at 06:53 AM Reply With Quote
Mine are ERW and not CDS as at the time I couldn't find any CDS, or not at a price that i liked!
however, i did buy thicker walled ERW, than the book said for the whishbones

never had an issue

steve





Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at




View User's Profile View All Posts By User U2U Member
adrianreeve

posted on 10/5/19 at 06:55 AM Reply With Quote
Thanks, what wall thickness did you go for? Was thinking 2mm.

Cheers

View User's Profile View All Posts By User U2U Member
MikeRJ

posted on 10/5/19 at 12:15 PM Reply With Quote
As Sam says the design of the wishbone is of more importance than the exact type of tube in this case. The spate of failures we saw on here years back was mainly caused by a terrible design to turned the wishbone from a triangle (with pure tensile/compression stress) to a parallelogram with significant bending forces around a big stress raiser.

Horrible
Description
Description


Better
Start of the front suspension.
Start of the front suspension.

View User's Profile View All Posts By User U2U Member
steve m

posted on 10/5/19 at 07:16 PM Reply With Quote
I don't remember what thickness, I bought,
But do remember why, a Friend used to make fairground rides, and he said they only used ERW, as it was cheap, and some of those fairground rides weighed several tons, and lots of kids!

My car doesn't, but does have one big kid inside!

steve





Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at




View User's Profile View All Posts By User U2U Member
mark chandler

posted on 11/5/19 at 06:55 AM Reply With Quote
Pop down your local independent landrover dealer, they will have a pile of steering drag links with fused track rod ends being thrown out from 90's, they buy complete replacements from Bearmach so it's not worth the effort freeing up.

My car has the shock pointing at the lower all joint using this steel and just 1/2" ERW for the top..

View User's Profile View All Posts By User U2U Member
myke pocock

posted on 11/5/19 at 05:30 PM Reply With Quote
For what its worth and putting my six penny worth in, considering the overall cost of the car to completion I cannot see a reason why you wouldnt get seamless for the job. Peace of mind to me!
View User's Profile E-Mail User View All Posts By User U2U Member
bozla

posted on 11/5/19 at 08:59 PM Reply With Quote
You'd probably be alright with erw, just shot blast after welding - will add strength in the surface. 750 formula book states that cds is only required for roll over bar and anti-roll bars.
18 awg (1mm), I'd probably go for 1.6mm.

[Edited on 11/5/19 by bozla]

[Edited on 11/5/19 by bozla]

View User's Profile View All Posts By User U2U Member
coyoteboy

posted on 12/5/19 at 08:35 AM Reply With Quote
quote:
Originally posted by Mr Whippy
Tbh when you see what modern production cars use these days those on a 7 look beefy


Really?
https://images.app.goo.gl/K4hxgax6rDJ2rBUx8





Report your local potholes, it actually works!

View User's Profile Visit User's Homepage View All Posts By User U2U Member
perksy

posted on 12/5/19 at 05:05 PM Reply With Quote
I was behind a lad in a Formula 27 once on a club run

He had a front wishbone fail just as we pulled up to a junction

If it had happened two minutes earlier gowd knows what would of happened as we weren't hanging about

Wishbones need 'over engineering' if anything

View User's Profile View All Posts By User U2U Member
AdamR20

posted on 12/5/19 at 06:39 PM Reply With Quote
A tenner says they would have failed anyway even if made in CDS It's much more about design than material IMO.
View User's Profile View All Posts By User U2U Member

New Topic New Poll New Reply


go to top






Website design and SEO by Studio Montage

All content © 2001-16 LocostBuilders. Reproduction prohibited
Opinions expressed in public posts are those of the author and do not necessarily represent
the views of other users or any member of the LocostBuilders team.
Running XMB 1.8 Partagium [© 2002 XMB Group] on Apache under CentOS Linux
Founded, built and operated by ChrisW.