Drive Shaft Twisting

[Callum]

I was at Doune Hillclimb (in Scotland) a couple of years a go and was talking to a competitor when drive shafts came in to the conversation. He said that Formula One Drive shafts twist around 1080 degrees (three complete rotations!) when doing a proper standing start. He said that because of this they are limited to doing around three standing starts per drive shaft.

Does anyone know if there is any degree of truth behind it, as three complete rotations seems incredibly much for it to spring back from.

Thanks

[mep]

I don't believe this.
Maybe 180° degree (half a rotation) but even that sounds much.

[Callum]

He was apparently 'in the know' but I still find it hard to believe.

[gcdugas]

Be serious... no more than two-four degrees...

Those numbers you throw out would made it impossible to shift without the shafts "unwinding" during the brief few milliseconds in between gears. Then they would wind up again during the next gear. The shafts haven't changed that much from when they had TC and TC needs precise response not an unpredictable and load variable amount of "torsion cushion". It would confuse the electronics as the wheel speed sensors would relate very indirectly to the electronically governed engine input. Where do these ridiculous numbers of 1080 degrees or even 180 degrees come from?

[piast9]

I also think its a BS. The shaft twisted that much would become much shorter which would ruin the differential, joints, hubs, everything.

[tok-tokkie]

Do you not know anything about elastic & plastic deformation? What material may only be elastically deformed thrice? Let alone the concept of using a torsion spring as a drive shaft.

[Scuderia_Russ]

He was either...
1)pulling your leg.
2)a complete half wit.

[Callum]

Do you not know anything about elastic & plastic deformation? What material may only be elastically deformed thrice? Let alone the concept of using a torsion spring as a drive shaft.

Hey, hey don't shoot the messenger!

[riff_raff]

Here's an interesting paper on F1 half shaft torque sensors. It's a few years old, but still relevant.

http://www.magcanica.com/files/SAE2000.pdf

riff_raff

[ringo]

Be serious... no more than two-four degrees...

Those numbers you throw out would made it impossible to shift without the shafts "unwinding" during the brief few milliseconds in between gears. Then they would wind up again during the next gear. The shafts haven't changed that much from when they had TC and TC needs precise response not an unpredictable and load variable amount of "torsion cushion". It would confuse the electronics as the wheel speed sensors would relate very indirectly to the electronically governed engine input. Where do these ridiculous numbers of 1080 degrees or even 180 degrees come from?

2 to 4 degrees?
What's the material of the shaft, the inner and outer diamter and the length?

[gcdugas]

Be serious... no more than two-four degrees...

Those numbers you throw out would made it impossible to shift without the shafts "unwinding" during the brief few milliseconds in between gears. Then they would wind up again during the next gear. The shafts haven't changed that much from when they had TC and TC needs precise response not an unpredictable and load variable amount of "torsion cushion". It would confuse the electronics as the wheel speed sensors would relate very indirectly to the electronically governed engine input. Where do these ridiculous numbers of 1080 degrees or even 180 degrees come from?

2 to 4 degrees?
What's the material of the shaft, the inner and outer diamter and the length?

I admit that I do not know any of those things about the material or diameter but I do know what design parameters the engineers would have in mind if the shafts were to successfully perform and relate to other systems such as the gearbox. It must be very stiff otherwise it would retain "spring torque" which would hinder shifting and possibly cause damage to the actual gears during the few milli-seconds that it was "disengaged".

[ringo]

I also think that there is design limit to the twisting.
It's possible i think, that the shafts may even twist less. I don't know but the material and dimensions could give a good indication.

[RH1300S]

I heard exactly the same thing years ago - I'm sure it was Eddie Jordon on the TV (when he was a team owner). Drive shafts twist an astonishing amount.

So armed with this baffling information I was at a visit to the Renault F1 facility - and opened my mouth with the very silly question (I felt silly after asking it). The Renault guy's take was the least twist the better, anything else wastes energy. It seemed so obvious when he put it like that.

Probably an urban myth.

[strad]

Seems far fetched at first...But then I recall that in the past...the V12 era I think,,but it could extend to V10s or even today..the camshafts would twist at high RPM and they would have to grind them to allow for that twist. If a relatively short camshaft can twist, I have to wonder just how much a half shaft does twist.

[Ciro Pabón]

Seems far fetched at first...

At first, at second and at third.

Let's see.

Shaft length, exaggerating, 1 meter (L).

Twisting moment (T) of 274 N-m, which I find in the Wikipedia article on Formula One engines.

Let's make the shaft of structural steel so I don't have to google for the modulus of rigidity (G), which I know is around 80 GPa (twice the one of titanium, btw).

I would like to have a manly shaft of 10 cm in diameter (D) and let's make the hollow part 9 cm in diameter (d).

So, torsional deflection (θ) is:

θ = 32 L T / (G π (D4- d4))

θ = 32 * 1 m * 274 N-m / (80000000000 N/m2) * 3.14 * ((0.1)^4-(0.09)^4))

θ = 0.0010 rad

θ = 0.06 degrees

That's around 6 hundredths of a degree. Am I mistaken? Thanks for any check.

Who would have thought that? Everybody seems to be wrong (probably, me too).

My verdict: