Competition Best input/output/intermediate shaft material

[Hohn]

Say a guy was building a no-holds-barred auto transmission and needed indestructible shafts.



Isn't there something better than Billet? I mean, billet what? 4340? H11? 300m?







300m is the strongest that I'm aware of, but I'm sure there's something better.



What materials would YOU choose?



There's gotta be something that can handle a 35-40psi launch w/slicks.

 

[Bob Wagner]

Justin, you should see the stuff that nw bomber member "OPIE" sells



not sure if Opie has a website or not

 

[ELake]

Carbide?

 

[DRAG DIESEL]

What about my Diamond Input Shaft? Just kiddin'.



On a serious note I would consider the upgraded input shaft ATS uses in their transmission. The diameter is the biggest you can run without changing the spline size or count. It takes advantage of all of the space where a typical stock shaft or most "billets" neck down after the splines. If my math is correct it will hold 30% more torque than any other shaft made of a like material, just from the increase in diameter. It's also ONE PIECE so "spline out's" are never an issue.



Just remember, no matter what the material, all input shafts will fatigue. The balance comes when you find a material that will flex enough not to break, but have a long service life and give you many happy 40+psi launches.

 

[zstroken]

I think the 300M stuff should be adequate. I would rather blow an input shaft, than a planetary.

 

[RKerner]

elongation is a good thing

Say a guy was building a no-holds-barred auto transmission and needed indestructible shafts.



Isn't there something better than Billet? I mean, billet what? 4340? H11? 300m?







300m is the strongest that I'm aware of, but I'm sure there's something better.



What materials would YOU choose?



There's gotta be something that can handle a 35-40psi launch w/slicks.

Like Drag Diesel said, you need strength and toughness. Toughness is a combination of elongation percentage and Charpy notch energy numbers. The H11 has very low elongation at break which is an indicator of potential brittle material even though its tensile strength is big.



4340 has good elongation and is commercially available in round bar stock.



300m seems to be a proprietary material which may limit its usefulness and availability.



Also look at shear modulus. Shafts will fail in torsion which is almost pure shear as there usually is some eccentric loading due to a slight bending load between its supports.



If you make your own shafts, also consider 4140 and 8620 alloys. They also make good shaft stock. Make radii or fillets as large as possible as any discontinuities in OD will create a stress concentration, typically around 3 as any fillets on a shaft over 1" in diameter will not allow big fillets.



Happy machining.

 

[RustyJC]

RKerner is spot on. Don't make a material selection based solely on ultimate tensile strength (UTS). Ductility, Charpy notch sensitivity, etc. are also critical factors that have to fit into the material selection tradeoff.



Rusty

 

[banshee]

For the best of the best - use a maraging steel (18% Ni).



Carpenter has a couple of excellent Alloys as well (AeroMet 100).



You'll pay big bucks for any of the top materials, unfortunately.



300M is a VAR (Vacuum Arc Remelted) 4340... in other words it's a cleaner version of basically the same steel. H-11 has a little better fracture numbers, but none of them compare to the superalloys.

 

[biggy238]

So what educational background/experience do you all ahve to have acquired this knowledge? Just curious. I know metalurgy but i'd like some elaboration. .