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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Thx Todd.

This helps me understand KW where I just used to ignore it.

KW sounds like a different measurement unit for 'P', Power, or HP.

If this is true, then I suspect or our P formula above might just have a different factor under (TxW) and or T might be something other than ft lbs. Just guessing.

Simplistically, I suspect the way an Inertia Dyno works is it times rate the large drum accelerates. This measures power at the wheel and gives them load by time measurement. Yes, the sensors probably compute this in Ft Lb's. And it dose meet the definition of and is TQ. However, this is not motor TQ. Much more needs to be done.

They also monitor the motor RPM. From this they can compute an effective gear ratio between the wheels and the motor.

From there they can compute or back into the wheel HP by RPM.

Then I suspect they should be able to by timing how long the mass of the roller and the wheel drive train combined take to run down and they should be able to calculate an estimate of how much the drive train loss is. From they should be able to come close to a number for HP at the crank to.

Once we have WHP or CHP we can multiply that by 5220 and then divide by RPM to compute the motor's TQ values.

So I am guessing motor TQ, as we know it, is the last conclusion in an Inertia Dyno's computation.

Never really thought about this before.
Old 03-01-2010, 10:06 AM
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