Miata Mailing List: November 1996, Message #97
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   From: Lance Schall <76760.2754@CompuServe.COM>

Subject: How do dynamometers?

   Date: Fri, 1 Nov 1996 20:23:42 -0500



I am not a dynamometer historian but I can tell you how at least one unit works.



The rollers are geared together and connected with no reduction to a large

electric generator.  Generator output can be routed two places: 1)  a resistor

grid on the roof where energy was disipated as heat.  The grid had an auxilliary

cooling fan.  2) a variable control sent some current to the stator winding of

the generator.  This varies torque required to rotate the generator shaft.



To measure torque, the generator is not securely fixed.  It is free to rotate

and the load on a lever arm attached to the generator housing is measured.

Force time length of arm is torque.  Rotational rate of rollers and torque give

power.



It would be easy to invent a hydraulic system in which the work done was pumping

fluid around instead of generating unneeded electricity.



Torque wrenches are calibrated using the definition of torque.  A precise

weight, a pulley of known diameter, and a strong lightweight cable would make a

servicable apparatus.



Lance Schall

Peak To Peak Miata Club

Boulder, Colorado













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