[Vwdiesel] something worth trading the A4 in for

[James Hansen]

Now, For the $101.00 question, how many of you have actually used a 
Prony Brake?

I have :-) With a few gas tractors, and a steam engine.

It's an external brake band that is free to rotate with the brake drum. 
  It's kept from rotating by an arm that rests on a scale.
Turn the brake drum with your motor, tighten the brake drum to the point 
where rpm starts to drop off and read the scale.  Multiply pounds on the 
scale by number of feet of length of the arm that is attached to the 
brake band, you have foot-pounds of torque, then you calculate the h.p.

Originally, it's use was to settle this very discussion in reference to 
steam engines, to be able to reproduceably demonstrate the power produced.
Another method was with a Baker Fan, just a big power soaker flat bladed 
fan, with a mechanical tachometer but the prony brake was much more 
accurate, and not variable with atmospheric conditions.

-james

Sandy Cameron wrote:
> At 11:06 AM 07/07/2008 -0600, you wrote:
>> It is called "brake" horsepower because the first dynomometer used a "pony
> break" to apply resistance (torque) to the output shaft being measured.
> 
> I think it was called a Prony brake, after the guy who came up with it.
> 
> Wiki calls it a De Prony, (probably French)
> 
> 
> Sandy
> 
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