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Shifting/Torque/Mechanical Advantage/Traction (was Re: Shift times)

To: geez@autox.team.net
Subject: Shifting/Torque/Mechanical Advantage/Traction (was Re: Shift times)
From: Todd Green <tag@cs.utah.edu>
Date: Tue, 09 May 2000 07:29:18 -0600
>We have a wonderful combined hand clutch and shifter on our Formula SAE
>cars (you can download an in-car video from one of our cars on our website

So does the U of Utah's SAE car :)  Now if I could just convince the
students that they should actually come out to every SoloII event so
they'd know how to drive, we might do better.  (Their advisor harps on
them too.)

>Now, before someone thinks that engine torque alone relates to
>acceleration, and that you should shift to keep your engine at peak torque,
>let me state the following.
> [clip]
>The car is accelerated by the torque on the rear axle, not the engine.

Technically the car is accelerated by the torque applied by the tires on
the ground.  If you can't get traction, all the rear axle torque in the
world does you no good.  (Yes, I'm sure you already know this, but I
think it is a point worth noting where we spend most of our time in 1st
and 2nd gear with large mechanical advantages, as opposed to road
racing, where you are in 2nd, 3rd, 4th, and it is a much different world.)

The problem I see, in autox, is that more often than not the course will
dictate where you have to shift.  Rarely does the course just go out in
a 'straight' line long enough to do the 1->2 shift (my 1st is gear
limited at ~37 mph).  Also many SoloII cars have enough power to light
up the rears very easily near peak torque in 1st (assuming you are also
pulling decent lat G's at the time).  I've found that it is easier to
just short shift into 2nd and focus on keeping the car as balanced as
possible (without having to micro-manage the throttle) if the shift
point is near a critical maneuver.

Todd

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