Ok smart guys tell me how a dynometer measures hp. I bet a few of us learn a thing or two from the answers on this thread.

It measures torque via strain gauges, LVDT's or some combination there of. Using that value and RPM the HP is calculated since there is a direct relationship.

Is this a trick question?

It is a trick question.

A dyno MEASURES torque and rpm. It then uses those to numbers to CALCULATE horsepower.

Torque = HP x 5252 / rpm
Dynos measure torque and the hp is calculated with the formula above

Dont most of them use water pressure in a pump to load the motor, or maybe thats old school

Most of the dynos you see for marine motors use a water brake.
The motor is attached to a shaft hooked to a turbine. The case or housing of the turbine pump is supported by members equipped with load sensors that have a metal rod of known diameter and material with a foil strain gauge bonded to it.
The turbine pumps water through the housing, and the flow of water is varied, causing the turbine to act as a brake which absorbs torque.

As the brake absorbs torque, it transmits it to the load sensors which stretch a tiny amount under the load, and the foil strain gauges respond by varying the electrical resistance through the circuit.

The brake can be adjusted to hold the motor at a given rpm, and a datalogger notes the resistance of the load cells in the circuit. This is done at different rpm all the way up to whatever the max planned reading.

Then each rpm/load cell resistance entry can be converted into a rpm/torque reading, which the hp is calculated from.

Water brake dynos have a tank of water attached to them because the water brake heats up the water as it creates braking force. After a hard pull behind a big motor, most dynos have to go through a cooldown cycle to let the water cool back off. The larger your tank, the more pulls you can do before you have to shut down and let it cool.

MC

its measured in pressure then converted..

do you know how torque is measured???

well this is how,,its when you wake up in the morning blinded and confused with a pi s s hard on and you mis the toilet and this is when you have to bend over to hit the toilet and you slip on yourown pi s s and fall forward and chip your tooth on the rim or the porslin toilet,,,nowthat's how phuckin torque is measured..

That's not torque, that's the Rockwell Hardness Scale. Either that or fluid dynamics.

Good job guys. Ill bet the average OSOer didnt know that a dyno measures torque and then Hp is simply a calculation. I didnt until yesterday while doing a little research. I found it pretty interesting.