7 replies to this topic

[hydra]

Hey all, here's a question that out to get the creative juices flowing... Which of the following would be best for a high-end ROAD car with 400bhp+ , >1000kgs that will probably be driven on some pretty bumpy roads; Chromoly-Tubing, 6xxx/7xxx Aluminum, or even Titanium? I'm automatically discounting Carbon Fiber on account of its significant expense and brittleness, again, this is intended for a ROAD car. As always your input would be highly appreciated. Thanks

[Marzal]

Probably steel, to avoid fatigue issue. On a road car, this parts must be calculated with an infinite lifespan in mind. It can be done with Aluminium or Titanium but it's more complicated...

[hydra]

If its any help, I'll probably be using ProMechanica/ADAMS/whatever...
btw, more and more road cars are being equipped with aluminum control arms, so surely fatigue can't be that much of a problem?

[12.9:1]

Originally posted by hydra
If its any help, I'll probably be using ProMechanica/ADAMS/whatever...
btw, more and more road cars are being equipped with aluminum control arms, so surely fatigue can't be that much of a problem?

Die cast - then forged, aluminum parts can use 100% automated production.

Steel stampings - 100% automated, are heavier

Tubular Alloy-Steel fabrications = man hours + costly materiel. But a light, strong, reliable part can
be made almost anywhere.

A hand fabricated Aluminum part, requires special techniques, or strength and reliability would be in question.

This goes double - no make that quadruple - for Carbon Fiber !

[mudpuppy]

The McLaren F1 used cast aluminum which was then machined. There is an excellent description of the design and build process in the book "Driving Ambition".

I have a question: how are titanium parts usually made, such as titanium connecting rods, watch bands, bolts, etc? I guess these parts are machined after being cast into a rough shape, such as a block or disc? I know that welding titanium must be done in a vacuum and until recently casting titanium directly into a complex shape (such as a gearbox, Minardi 2002 and Ferrari 2003) was not possible. So, what is the conventional way? What is the benefit of "explosive casting"?

[Leo]

As far as I know titanium uprights on old F1 cars were fabricated from a solid block by carving the redundant material.

[Cory Padfield]

Leo,

Titanium alloy uprights in Formula 1 are made by 3 different processes, depending upon the team:
1) machine from billet
2) investment casting
3) welded from sheet

mudpuppy,

Titanium connecting rods and bolts are made by forging - using solid titanium bar and compressing it between matched dies that have an impression of the desired shape. Titanium watch band parts are stamped from sheet metal. I don't know what explosive casting is.

hydra,

The reason more road vehicles are using aluminium control arms is that, in addition to fatigue strength requirements, they must not buckle elastically during compression. The Performance Index P for buckling resistance is proportional to rho/sqrt(E), where rho is the material mass density and E is the elastic modulus. Thus, aluminium alloys are better than titanium alloys or steels.

[desmo]

Re: "Explosion casting"- This process whereby a section of metal sheet or tubing is immersed in water and then forced into a die or dies by capacitive disharge or actual high explosive detonation is usually referred to as explosion or explosive forming. One engineer doing a rather "blue sky" investigation into a multiphase steel fabricated crankcase design said this was the means selected to produce a prototype for further testing and evaluation. A google search on "explosion forming" will bring up some useful further information on the process. BOOM!