Building a Prony Brake
Posted: Wed Dec 18, 2013 11:22 am
hello everybody,
To test engines, i want to make a so called prony brake. I searched the internet, but there is not that much info that is helpful.
I looked at this diy prony brake, and i think i understand the working of it now.
To test engine power, you have to attach a clamp or similar to the axis of the engine. That axis then presses on a scale, where you can read how much pressure is applied.
The clamp on the axis must then be slipping, slowing down the engine. You then have the momentum, and with the engine-speed you can calculate power output.
wikipedia learns me this:
The constant 5252 is the rounded value of (33,000 ft·lbf/min)/(2π rad/rev).
If i convert that to the units we use in the Netherlands i come up with the following:
P(Hp) = T(N/m) * f(rpm) / 7121
and
P(Watt) = T(N/m) * f(rpm) / 9,682
Is the above correct? I hope there is somebody that can confirm the formula's above, we don't work with feets en pounds here in the Netherlands, we use meters and kilos.
Also, is there anybody that has built a prony brake? If you did, i'd love to see the photo's of it.
Thanks in advance!
To test engines, i want to make a so called prony brake. I searched the internet, but there is not that much info that is helpful.
I looked at this diy prony brake, and i think i understand the working of it now.
To test engine power, you have to attach a clamp or similar to the axis of the engine. That axis then presses on a scale, where you can read how much pressure is applied.
The clamp on the axis must then be slipping, slowing down the engine. You then have the momentum, and with the engine-speed you can calculate power output.
wikipedia learns me this:
The constant 5252 is the rounded value of (33,000 ft·lbf/min)/(2π rad/rev).If i convert that to the units we use in the Netherlands i come up with the following:
P(Hp) = T(N/m) * f(rpm) / 7121
and
P(Watt) = T(N/m) * f(rpm) / 9,682
Is the above correct? I hope there is somebody that can confirm the formula's above, we don't work with feets en pounds here in the Netherlands, we use meters and kilos.
Also, is there anybody that has built a prony brake? If you did, i'd love to see the photo's of it.
Thanks in advance!
