How would you manufacture a wishbone?

[tathan]

Cast steel?! I meant aluminium. I thought that was obvious, which OEMs use cast steel arms?

I didn't go into any detail in earlier post cos was dashing off on way out house, used to work in warranty for a tier 1, saw a few broken suspension arms so familiar with failure modes. Your "real engineers" have already thought their way around it and don't use an unreliable process to manufacture critical parts. They are NOT going to test every one, they don't even do that with stuff like oil pumps or pistons

Like marcush said they are very intent on reducing waste - you must be from a racing background though not OEM because even the piffling dollars they save is HUGE if they sell 10mill cars!

The best engineering solution is usually the simplest too, not the most exotic or expensive, it's not F1 ;

edit: disclaimer, it's bank holiday, had a few shandies

[Greg Locock]

I have had parts that have been strength tested as part of their production process. Every single one. I have had other parts that have been X rayed. Every single one. Typical production volumes of those parts were 60000 and 130000 per annum respectively


I have seen cast steel for suspension arms in the past. We specced the loads and the envelope and the weight target, Hitachi did the whole job.

[Tommy Cookers]

I doubt anything metal will match the strength, fatigue life and weight of MIG welded CroMo tubes put together by a good fabricator.

wishbones are not necessarily a good place to seek weight saving by using a high strength steel

steel tubing as mentioned above would be about twice as strong as (cheap) general-purpose grades
but if we design to use that higher strength ie to halve the weight by using thinner wall and smaller dia tube
we have greatly reduced the buckling strength (which can then be a problem, unless the wishbone is fairly short)

similarly, higher strength materials will give relatively poor fatigue lives (if their strength is fully utilised in the design)
because the fatigue limit doesn't increase proportionately in stronger grades of material

in the impact case, the fracture work of the cheap wishbone will be higher even when both are built to the same weight
(because of the great plastic range of the general-purpose material)
and very much higher if the 'good' wishbone is built to maximal weight saving

although F1 likes 'frangible' wishbones, my guess is that mass producers don't ??
I assume they design in part for impact loads on wishbones

a specific-strength-competitive lower density material could give better buckling behaviour and weight saving
(didn't the Honda NSX, and others ? have Al alloy wishbones ?)
though Titanium was the usual choice for racing ?

[flynfrog]

I would look at semi solid metal casting for Numbers around 10K. Light can be complex shape high rate of production. Die charge could be a little on the high side but cheaper than stamping.

[strad]

GM used cast aluminium to good success.
For small batches I would think tube steel.
But then I have no degree.