Power Loss measurment on Eddy current dynamometer
Power Loss measurment on Eddy current dynamometer
(OP)
Hello.
I want to know more about dynamometers, namely Eddy current dynamometers.
My issue is Power Losses Measurement, i know that after reach max desired rpm one should press the clutch till the car stops and the computer in the dyno take the power loss values.
But when you press the clutch the engine stops transmiting torque to the engine rollers, so the load cell isn t submited to any force in that period...i think...
My question is:
How exactly the Eddy current dyno measures Power Losses when you press the clutch?
Thanks.
I want to know more about dynamometers, namely Eddy current dynamometers.
My issue is Power Losses Measurement, i know that after reach max desired rpm one should press the clutch till the car stops and the computer in the dyno take the power loss values.
But when you press the clutch the engine stops transmiting torque to the engine rollers, so the load cell isn t submited to any force in that period...i think...
My question is:
How exactly the Eddy current dyno measures Power Losses when you press the clutch?
Thanks.





RE: Power Loss measurment on Eddy current dynamometer
Wanted to say dynamometer rollers.
Sorry.
RE: Power Loss measurment on Eddy current dynamometer
Roll down time can be used to measure inertia in the system downstream of the flywheel or drag in the system downstream from the flywheel.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Power Loss measurment on Eddy current dynamometer
So roll down time and variation of roller speed (acceleration) can be used to calculate kinetic energy and then power losses.
The dynamometer computer do this if we input car and driver weight is it right?
RE: Power Loss measurment on Eddy current dynamometer
It is inertia type dynos that calculate power from rate of acceleration of a heavy wheel or roller. They use a coast down procedure to calibrate them, BUT the engine should be in gear as that is done so the inertia of the engine is also measured.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Power Loss measurment on Eddy current dynamometer
Yes i understand, but i have seen people in Eddy dynos doing the "coast down procedure" after a test, and i want to know what kind of data and what is behind the procedure to calculate power losses.
Can you clearly tell me that?
Thanks.
RE: Power Loss measurment on Eddy current dynamometer
Many years ago I worked for a well-known UK manufacturer of DC-motor chassis dynos and developed a coast down procedure to calibrate the roller bearing friction out of the equation. Bearing temperature makes big difference to accuracy.
RE: Power Loss measurment on Eddy current dynamometer
My conclusion: The transmission losses are estimated ( calculated) in every chassis dynos based on coast down time and speed of the rollers among others.
Am i right?
Thanks.
RE: Power Loss measurment on Eddy current dynamometer
If you do a coastdown on the track, and get the same speed vs time curve as you do on the dyno, then you are telling fibs, but it is possible to get it pretty close. One problem is that a real coastdown test is a great way of measuring the gradients and local variations of wind speed and direction on your test track.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?