Truck parts Dynamometer.

[Terry Sare]

What about the surplus DC generators they use for welders? They are 400 Amp 
units -- what horsepower would they use up?

_

-> our facility.  Building the rolls is a large task.  They have to be 
-> machined on large lathes and balanced.  If you go with small diameter 
-> rolls they must be carefully balanced as they will be spinning faster 
-> then large rolls.
     
 The rolls on my Clayton chassis dyno are 8" in diameter and about 7
feet long.  Appropriate tubing for new rolls is $7/ft locally, and any 
driveshaft shop should be able to spin balance them.
     
     
-> The tires slip on the rolls at higher powers, and there is a lot of 
-> energy lost by the tires heating up as they deflect at the roll
     
 Yes.  They're only useful as full-range dynos for less powerful cars,
but they're quite handy for doing low speed and part throttle work on 
any car.
     
     
-> our engine and chassis dynamometers is to use regenerative DC motors 
-> as PAUs.  The DC motors operate as generators to absorb the power and
     
 I checked that out once.  An appropriately sized DC motor, new, appears
to be in the $15,000 range.  Apparently they sometimes show up on the 
market as scrap, but I haven't found one.
     
     
 It's ironic that getting rid of horsepower is more difficult than
making it in the first place...