Rx7carl

Does anyone have experience with lightened running gear? Things like gun drilled axles, pinion shafts, transmission shafts. Lightened ring gears and axle flanges etc.

Source for lightweight driveshafts? I know someone used to make an aluminum shaft for the 1st gens, just don't know who.

Cost, Advice, Durability?

j9fd3s

iTrader: (3)

i have heard <--- key words! that the spec miata people do this kind of thing. on something like a 12A with a Nikki, that isn't going to make much power, i'd think doing all the gun drilling would be fine reliability wise, provided you started with the bigger 84-85 axles.

benefits are probably pretty small?

j9fd3s

iTrader: (3)

i build a little test rig in solidworks, and its interesting, you loose strength as you start drilling the axle, but not that much, until you get stupid with it.

for instance going from a 6mm hole to a 15mm hole has a small impact, but a 25mm hole actually starts tearing.

the other important thing is the way the axle is machined does matter, big fillets help a bunch

Shredduuhh

iTrader: (11)

i know someone that has a drag car, he owns a shop, ****** shack ...
his drag car has lightened spool, gun drilled axles, scalloped hubs, ultra lightweight brakes, aluminum driveshaft lots of ti. hardware all over the car.. he gets all his customers aluminum driveshafts from inland empire driveline in upland ca.

elwood

iTrader: (1)

Semi-floaters, like the OEM axles: Gun drilling of axles is very common in drag racing, where the stress is almost purely torsional. Road racing adds the bending force to the axle, which is very different. The loads are different enough that the axle makers even use different types of steel for road race vs. drag race. I don't know if gun drilling is common for road race semi-floaters.

Did you apply a bending force to your FEA, in addition to the torsional?


Full floaters: Gun drilling works fine for either drag or road race, since this design removes the bending force from the axle shaft.

elwood

iTrader: (1)

I agree. Since the weight savings won't be much and all of these things are so close to the central axis of rotation, there won't be much of a savings in inertia.

That said, I do have an aluminum driveshaft. I got one because I had a hell of a time getting an aftermarket steel one that was properly balanced, and I had been told that the lighter weight of the aluminum shaft made it easier to get right. The shaft was made by Quarter Master. They only use 1310 style u-joints, so you would need to supply the transmission yoke, pinion yoke, and adapter style u-joints. I wrote this up in my Toyot 8 build thread (post #50) --> https://www.rx7club.com/build-thread...a-8-fb-992844/

j9fd3s

iTrader: (3)

easy enough to do, with JUST a bending force a 2mm hole has a safety factor of 1.36, and going to a 10mm hole its 1.32

15mm gets you 1.23...

so its a similar curve, small hole and you loose almost no strength, but after a fashion strength drops way off.

and B it HEAVILY depends on the ACTUAL construction of the axle, fillets and radii matter, so i think the trend works, but i wouldn't go and drill a 15mm hole in my axle based on this!

so i have an axle sized iron thin, and its 7.95lbs, with a 2mm hole, and with a 10mm hole its 7.53lbs, that's more than i'd expect

elwood

iTrader: (1)

I have seen axle shops that offer lightened ring gears, but don't know the risks or potential "offsets". For example, if you remove material, you might cryo treat and stress relieve the component and end up better off than beforehand.

I'd say to call and talk to an engineer at some of the better shops like Mark Williams and Strange. I talked to a few guys at these places in the past, and they seemed to know their stuff and not offer up any BS.