Quote:
Originally Posted by Frank Lee
I bump start by releasing the clutch as it would be for normal shifting operations- nonna this double clutching crap. There's no need for it. And, I fail to see the failure mode for dumping the clutch in P&G- no excessive rpms, no excessive torque loads.
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So you got me thinking.... just how much torque is there? So some engineering maths.....
Lets assume we only have to spin up a flywheel... that is, no piston friction, accessory load, etc. etc. Just spinning up a ~20lb mass in a 12" disk. I'm going to do this in SI and convert to ft-lb because, lets face it, Slugs are a retarded.
mass = 9kg (slightly less than 20kg)
radius = .3048m (12 inches)
assume uniform weight distribution (this is not true, there's typically more weight near the out edge)
So Angular momentum (L):
L=I*(omega)
where
I=Moment of Inertia (again, assume uniform distribution - also assume a 0 height disk)
(omega) = angular velocity
angular velocity = 136.78 rad/sec - about 1500rpm
So,
L= 57.18 (kg*rad/s*m^2)
Torque is the differential of angular momentum with respect to time (dL/dt)
Time from 0 to 1500 rpm....
Staring with 50ms and converting to ft-lbs
843.52746 ft-lb
421.76373 foot pounds for 100ms
210.881865 foot pounds for 200ms
And 200ms is starting to get slow for something like this.... Add on top of this that, in reality, these numbers are higher when friction, and accessory loads, reciprocating and other rotating mass are considered.... I'm fairly confident that the load will be more like a gradient - the closer you are to 0rpm, the higher the torque and the closer you are to your final rpm, the lower the torque (approaching 0) with the value above being the average over the entire range.
Now, my car makes a max of 122ft-lb at 2600rpm.....
Not to gloat... but the last owner of my car (and only other owner) babied the transmission... I too am nice with my transmission.... I've got 115K miles on the factory clutch
I'm fairly confident that's not from dumping the clutch
Feel free to check the maths - remember, it's a simplified calculation (something I could do using notepad and the calc that comes with windows
).