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Author: Subject: Wishbones 3mm or 5mm plate?
geedle

posted on 15/4/20 at 03:53 PM Reply With Quote
Wishbones 3mm or 5mm plate?

Hi,

I can't find a thickness for the plates used in the wishbones in the Saturn manual. Are they 5mm as per the Haynes book or is 3mm enough?

Thanks.

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mtt mark

posted on 15/4/20 at 07:37 PM Reply With Quote
I have some westfield ones on my car, they are 3mm plate, 5mm seems overkill and heavy.





It will fit,.....smack, told you so

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geedle

posted on 15/4/20 at 08:09 PM Reply With Quote
Yeah - 5mm did seem a bit thick given the wall thickness of the tubes. Thanks.
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ianhurley20

posted on 15/4/20 at 08:56 PM Reply With Quote
DO NOT USE 3mm! If you look on my build blog you will find that the professionally made wishbones with 3mm bent on their first trial, my replaced 5mm ones never failed. Your choice!





My build blog http://ianhaynes20.wordpress.com IVA passed 3/10/16
written off 23/9/18
Aug 2019 completed Tiger Avon with ST170 on TB's
Now restoring 1968 Ginetta G4
And - a series 1 Land Rover - don't ask why!

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rusty nuts

posted on 15/4/20 at 09:00 PM Reply With Quote
Do a search on here for failed wishbones
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MikeR

posted on 16/4/20 at 07:17 AM Reply With Quote
The design is important. If you have a straight line between wishbones closest to the chassis as per Ron's design it fails. You need a curve as per mk wishbones.
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mtt mark

posted on 16/4/20 at 07:47 AM Reply With Quote
Just re-measured westfield ones, 5mm, so theres your answer.





It will fit,.....smack, told you so

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ianhurley20

posted on 16/4/20 at 07:50 AM Reply With Quote
quote:
Originally posted by MikeR
The design is important. If you have a straight line between wishbones closest to the chassis as per Ron's design it fails. You need a curve as per mk wishbones.


Sorry Mike - that certainly wasn't the case with mine. In the accident that wrote the car off both the rear wheel and front conneted with trees and in both cases the standard wishbones escaped unscathed, the rear suspension was ripped off completely and the front bent the lower chassis rail. Whilst I wouldn't advise such , both front and rear wishbones could have been reused





My build blog http://ianhaynes20.wordpress.com IVA passed 3/10/16
written off 23/9/18
Aug 2019 completed Tiger Avon with ST170 on TB's
Now restoring 1968 Ginetta G4
And - a series 1 Land Rover - don't ask why!

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Mr Whippy

posted on 16/4/20 at 08:05 AM Reply With Quote
On safety critical items your staking your life on, a bit of extra weight is worth it. I had one of the factory made rear trailing arms snap at the weld on my Bluebird and by just pure good luck missed a 50 mph head on with a Golf. Don't skimp where it matters.
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MikeR

posted on 16/4/20 at 08:11 AM Reply With Quote
quote:
Originally posted by ianhurley20
quote:
Originally posted by MikeR
The design is important. If you have a straight line between wishbones closest to the chassis as per Ron's design it fails. You need a curve as per mk wishbones.


Sorry Mike - that certainly wasn't the case with mine. In the accident that wrote the car off both the rear wheel and front conneted with trees and in both cases the standard wishbones escaped unscathed, the rear suspension was ripped off completely and the front bent the lower chassis rail. Whilst I wouldn't advise such , both front and rear wishbones could have been reused


Interesting reply, it's been s long time since a read the wishbone threads, but what I stated is what I recall the consensus on the design flaw with the wishbones as the straight line design creates a stress raiser and the wishbones bend at that point. The curved design feeds the stress into the wishbone over a larger area. I guess the advice to the original poster is to find the thread and double check.

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Theshed

posted on 16/4/20 at 01:30 PM Reply With Quote
Were all the wishbone failures (in the worlds longest thread) not in the tubes rather than the plates? In which case would putting on a thicker plate not make things worse? The best approach must be to avoid bending loads on the tube but, if you cannot do that completely make sure that the tube is loaded over as wide an area as possible. A curved plate is one way of doing that.
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rusty nuts

posted on 16/4/20 at 05:17 PM Reply With Quote
Think I would rather use 5mm than take a chance especially since the amount of potholes we have now. Also suspect some of the failures at least were down to the well known crush tube issue with some cars?
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Theshed

posted on 16/4/20 at 09:43 PM Reply With Quote
Rigid crush tubes plus thick plates is the problem. All the bending forces act on the tube in between. If this debate was about 5mm thick walled tubes then fine but it isn't. the plate at the end of the wishbone needs only to be thick enough to take the load between the tubes (front to back). Anything else is to add strength to the tubes themselves. Beyond the plate and crucially at the junction, they are on their own.
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geedle

posted on 20/4/20 at 12:41 PM Reply With Quote
OK - sound advice. 5mm it is.

Does anyone know if the plates used on the Saturn diagrams are 3mm or 5mm? If they are all 3mm and I use 5mm plate, I'll need to correct the measurements.

Thanks for all the input.

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PorkChop

posted on 20/4/20 at 02:03 PM Reply With Quote
To me, Ian's failure looks to be different from the common failures discussed on LCB. Looking at Ian's blog, the failure was the plate bending at the lower balljoint end on Sierra spec wishbones?

In any case, the SSC wishbones are very different at the outboard end to allow standard MX5 lower balljoints to be used instead of Maxi ones. From memory the plates were all 5mm (but I don't have my car any more, so can't measure to double check) and from what I remember of speaking to Andy Hugill, if anything plates were made thicker compared to the Sierra version rather than thinner.

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ianhurley20

posted on 20/4/20 at 03:18 PM Reply With Quote
quote:
Originally posted by PorkChop
To me, Ian's failure looks to be different from the common failures discussed on LCB. Looking at Ian's blog, the failure was the plate bending at the lower balljoint end on Sierra spec wishbones?

In any case, the SSC wishbones are very different at the outboard end to allow standard MX5 lower balljoints to be used instead of Maxi ones. From memory the plates were all 5mm (but I don't have my car any more, so can't measure to double check) and from what I remember of speaking to Andy Hugill, if anything plates were made thicker compared to the Sierra version rather than thinner.


The wishbone failure is as you describe, and yes they were Sierra spec wishbones that were made in stainless steel by a professional welder where the bottom ball joints bent the 3 mm steel when I had access to an oval racetrack for a day. I am glad I had that day to discover the fault and they were replaced by standard book spec sierra wishbones with 5mm steel. This page amongst others was posted on the Viento thread earlier. https://www.eastangliankitcars.co.uk/apps/photos/album?albumid=16133545
You can see 19 photos which show the damage to my car both at the scene and at my home later (and yes, I was very lucky to walk away from this one)





My build blog http://ianhaynes20.wordpress.com IVA passed 3/10/16
written off 23/9/18
Aug 2019 completed Tiger Avon with ST170 on TB's
Now restoring 1968 Ginetta G4
And - a series 1 Land Rover - don't ask why!

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steve m

posted on 20/4/20 at 04:02 PM Reply With Quote
I really don't see what all the fuss is about, nor care

But on my book built Locost built in 1997, from Rons first ever book, Edition 1, 1996

It clearly states 3mm plate, and that is EXACTLY what my suspension was made off, and to the design in the book with a radius

My car lasted 20 years, and had more than 25000 miles done on those whishbones, and tracked a couple of times, until an engine fire destroyed my car, so the design was sufficient to do the job

steve





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




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steve m

posted on 20/4/20 at 04:05 PM Reply With Quote
oh, and to add to the woes, I couldn't find any CDS, so made my bones from welded tube

I suppose I had better go and sit on the naughty step now for 6 months

steve





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




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geedle

posted on 20/4/20 at 04:57 PM Reply With Quote
I did manage to get CDS, but it had to be ordered specially and was not cheap.
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