Re: [DML] Input Shafts

[Martin Gutkowski <webmaster@xxxxxxxxxxxxxx>]

content22207 wrote:

>Smaller splines also = weaker splines. 
>
Yes, but there are twice as many of them! In fact the surface area they 
cover is larger, so as a total, you've got a stronger link. Are the 
splines precisely half the size on the newer ones? Explain to me how 
there are 21 instead of 20?

> And
>they're shaped differently (angled sides vs straight), reducing the
>amount of material even further. 
>
But the "base" of each spline is the same size, so the amount of 
material taking the shear force is exactly the same.

>I fail to understand the inherent weakness of Renault input shafts.
>
There isn't one. I've stated this many. many times before - it's been 
designed as the weakest link deliberately to prevent anything more 
expensive breaking instead. BUT that's not to say they're "weak". These 
gearboxes have a deserved reputation for being absolutely indestructible 
over here - a special race edition of the Alpine A610 GTA V6 Turbo put 
out well over 400bhp from the factory! For the gearbox to break was 
unheard of. The UN1 and 369 gearboxes (which are interenally identical) 
are very sought after - Lotus used it in the Esprit, and you don't head 
of many Esprit owners breaking input shafts, and that's a twin turbo V8.

THE REASON THEY BREAK IS THE FINAL DRIVE. On the DeLorean it's 3.4:1 - 
on the 25 turbo, Alpine, Esprit, they're all 3.8:1 - this puts less load 
on the clutch and gearbox, and dumps it to the back tyres.

>Ford runs theirs on the 460 (425 lbs torque) no problem. Apparently a
>Chevy 350 will snap the Renault. Or does it just strip the splines?
>
I bet it snaps the shaft - the size of the splines has little to do with 
the "grip" - ever used taper-lock tools? That relies on friction at a 
molecular level - nothing more than one cone knocked inside another cone 
with little force, is enough to hold a 1/2" chuck on my 3kW pillar drill.

Martin

>  
>





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