Wishbone Material
 

Hi This is my first post so please be gentle!

I am coming to the end of building the chassis for my MX5 based roadster using the Saturn (or NTS?) plans (with a few tweeks). Looking forward to the next stage which looks to be the suspension wishbones.

Maybe I need to go to specsavers but I cannot find any specs for the material used for the wishbones apart from the obvious dimensions. Do I need ERW or seamless and what wall thickness?

All help greatfully recieved
Steve

The Haynes book says to use 19mm and 25mm Seamless (CDS). I don't think a wall size is given. I am planning to use approx 2mm wall thickness but I have read on this forum about people using as thin as 1.6mm. I recall someone saying that westfield use 1.6mm on theirs.

Regards

Andy

Ive just started making my bones.... I went for 19mm and 25mm CDS, and its really expensive!!! Think its 3mm wall! The tube bushes are made from 33.7mm x 2.6mm ERW, but i think you can only get 2.5mm or 3mm in general. Its pretty cheap per length, but you dont need a full length obviously. I could only get 3mm wall, so i will be machining mine down just a touch to fit the bushes.

As far as i know, the book spec for the saturn/NTS wishbone adjusters is 25mm diameter mild steel bar stock, threaded to M18x2.5mm. This is a bugger of a job to do in my opinion! I drilled the holes in the lathe, then hand tapped the thread, took me 2 hours to do all 8!!!! If i was doing it again i would use M16x2.5, or M20x2.5, as M18 is a hard size of bolt to get!!! I have got some M18x2.5mm threaded rod, but the problem is its only 4.6 grade, but ive calculated that this should take more load than it will ever recieve. Only problem would be hitting a kerb or such like i guess!? M18 bolts seem to be hard to come by from local suppliers, and are expensive where i did find some!!

The front upper wishbone takes a 30mm diamater mild steel bar stock, threaded to M14x1.5 to suit the BMW drag link. Im sure at some point andy (saturn) said that 25mm round was used for this, but im sticking to book spec, to keep the angle the same.

One thing that isnt in the saturn guide, is the angle of the front upper wishbone jig, but im assuming its the book 78 deg! Maybe andy / nathan could verify this for you?

Hope this is of some help, best get back out to the garage and get my next wishbone made...

Cheers gents.

Have just got a quote for CDS tube, eek :eek:

That decides it I'm gonna be lazy and buy some ready made :rolleyes:

What was the damage?
I have been quoted £40 for a 6m length of 20mm
And £42 for a 6m length of 25mm.
Only tried one stock holder so not sure if this is good or not.

Out of interest, any idea What total length is needed?

Think thats not a bad price at all! What wall is that for?

I was £170 (and that was mates rates), for

1 x 6.1m length 19mm CDS (think the wall is 3mm)
1 x 6.1m length 25mm CDS (think the wall is 3mm)
1x 6.1m length 33.7mm ERW tube x 3mm
1 x 6.1m length 40x3mm flat bar
1 x 6.1m length 25x3mm flat bar

I did two of my wishbones yesterday, and to be honest they aren't that bad. Just get the jig spot on, and you're laughing.

It was £50 + very annoying tax for 25mm x 6m, 2mm wall CDS.

I gave up asking after that as I reckon by the time i've made all the jigs, mucked about with loads of silly angles, brought and machined the threaded bits and bunged the pro welder in the unit next door a few quid for tigging them up they'll probably only be 100 quid cheaper than buying them in. Not to mention the many hours involved.

http://www.rorty-design.com/content/tube_work.htm

A bit about the differences between the tube types and why the are used. This end of things is more important as your health and well being are at stake, when it comes to any of the suspension stuff I wont short change anything just to save a few quid. Have seen enough failures in this department and its never pretty.

Bob

Good find Robo

Trouble is I fancy building one of those buggies now :eek:

ERW is fine for wishbones, wishbones should be seen as expendable items in the event you clout a curb or worse they want to absorb the impact and bend, that way the chassis suffers less damage.:) Use 14swg (2mm wall)