What's the best/strongest material for RC car models? 1

[imbuter2000]

I like to play and abuse RC car models like this:

http://rccaraction.com/Media/CorePages/4_0.jpg

However, when making big jumps or high-speed crashes (they can even reach 90mph), even steel parts gets damaged and needs to be substituted. See these damaged/broken parts for example:

http://img169.imageshack.us/img169/4286/cimg1700.jpg

Is there, in theory, a material better than steel for these parts, that could be mass produced with a price to consumer <$1000 for all the critical parts of these cars (let's say 200 grams or 1/2 oz)?

 

[CoryPad]

There probably is not such a material. Try ultrahigh strength steels like 300M, maraging steel, and AerMet 100. Maybe nonferrous alloys MP35N or titanium (e.g. Ti-6246, Beta C, LCB) or aluminium alloys (7075, 2090).

 

[imbuter2000]

Thanks CoryPad for all the suggestions.
I'm not in the field but... what about the kevlar that has a yield strengh of 3600 MTa compared to the 800 MTa of a medium steel?

 

[CoryPad]

Kevlar has fantastic strength properties as a fiber, as do carbon fiber and polyolefin fibers. But they are expensive. Also, you have to put those fibers together with a matrix to make an actual part. This process is expensive. Plus, these fiber composites have limited damage tolerance, so they are likely to fracture into multiple pieces rather than bend or deform when loaded during jumps or crashes.

 

[Tmoose]

If tubular parts subjected to compression are bending or buckling, make the OD 10% greater and try again. At some point the parts applying the end loads will become the weak link.

It would be helpful to see the broken surfaces on The (threaded?) end-fittings that broke. If fatigue is indicated there are probably geometry changes that could be made to reduce stress concentration and get huge life increases.
I hate Using super materials to compensate for bad geometry.

 

[CoryPad]

Amen on the geometry comment, Tmoose. One must use geometry to resist forces, then materials to resist stresses.

 

[Bribyk]

The scale of RC cars kinda rules out composites too, at least without them being even more expensive than they already are. Stuff like carbon fibre and kevlar are globally very strong and limit damage to local regions but the relative size of the fibres and any defects almost guarantees component failure.

Materials crash course...

Steel - heavy but strong and resists impact loads well (more chance of bending before breakage). Very rigid. Cheap. Welds easiest and machines well.

Aluminum - about the same strength to weight ratio as steel but doesn't resist impact loads well and WILL eventually break. Requires very good understanding of loading conditions to prevent excessive deflection and/or failure. Easiest to machine though.

Titanium - somewhere in between aluminum and steel on properties, absorbs impact well, expensive and tougher to machine.

Disclaimer: these are obviously generalities and can not account for every composition of these materials.

As far as I know, you can get RC parts in all of these materials and some plastic components. I think the manufacturer's have the material choices that are economical nailed down.

 

[imbuter2000]

Thanks Bribyk, interesting contribution

 

[EdStainless]

If you are talking about a limited range of parts (the ones that keep breaking) there may be options.

As has been stated, redesign first to minimize stress concentrations and excessive flexure.
Then it is time to find a shop with a small 3 axis model mill and select an alloy.
Personally I like the idea of Maraging 250 or a PH stainless (Custom 455 or 465 come to mind). The advantage of these alloys is that the final heat treatment is at low temp (1000F) so there is minimal distortion.

Just remember, you make one part stronger something else will break.


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[HgTX]

RC = radio-controlled? I thought maybe this was a variation on the theme of the concrete canoe!

Hg

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[ShortWood]

Before you go exotic and expensive, try something less hard and more tough, lower BHN with higher Elongation rate