Material for trailing arm

Question

Material for trailing arm

gmoyer (Mechanical)

(OP)

8 Nov 02 19:05

A friend of mine was grumbling about the cost of a set of trailing arms and toe links found at the bottom of the page on: http://www.m2performance.com/psuspen.htm

I was just wondering if anyone here had an educated guess as to the material of the rod. Would it be a mild steel, mid-carbon (heat-treated?), or an low-alloy like chrome-moly (would this end up being heat-treated after being machined too?). Also, could it be aluminum?

Probably not much info for you but I thought asking wouldn't hurt. If the material is a mild steel, it does seem like a lot for round stock with some holes tapped in the ends and some rod ends with bushings...

TIA,
Grant

GregLocock (Automotive) · Answer 1 · 2002-11-08 19:17:41

I'd use a decent steel for that job. It is nice that they've tapered them, this is the most efficient shape for the job if they wok in comprerssion (which they do). The material would be machined in its heat treated form, no need to post heat treat.

I'd figure on about 60 bucks to make them, so 240 selling price is about right.

Cheers

Greg Locock

CoryPad (Materials) · Answer 2 · 2002-11-09 00:42:17

I would guess they use either alloy steel like SAE 4130 or a High-Strength Low Alloy (HSLA) steel.

Greg, that price seems high to me, unless they plan to make < 1000 or so per year. I guess that would be the right ballpark for an aftermarket manufacturer.

gmoyer (Mechanical) · Answer 3 · 2002-11-09 23:50:45

Greg and CoryPad,

Thank you both for your input.

Greg, your comment about the taper has caught my attention. I don't recall ever seeing anything about a most efficient shape for a member in compression. Just out of curiousity is there an ideal taper?

Thanks again,
Grant

GregLocock (Automotive) · Answer 4 · 2002-11-10 16:14:19

Yes, if you look at an old biplane you'll see that the compression members have a nice shape to them, roughly parabolic.

This comes about from the elastic buckling mode, where the important bit of the section is in the middle, whereas adding material at the ends has little effect on the buckling strength.

Now if you were hoping for a handy equation for the shape you are out of luck, but if you work out the buckling equation from first principles then I /guess/ it will be fairly easy to calculate.

<CoryPad> Exactly. In volume production we make much the same thing for about $20 a pair

Cheers

Greg Locock

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Material for trailing arm