Ngine running at 900 RPM to power a generator

[Josh111]

I am trying to use an engine running at 900 RPM to power a generator that needs to run at 1800 RPM ( This will go through a pulley)

My question is is half the available horsepower to the generator lost since the RPM's are doubled?
In other words, do I need to double the horsepower of the engine to do this?

 

[Airman]

I don't think so. The RPM's are doubled, so the torque is halved, but I think the same amount of energy will be transferred, so you will have the same horsepower. Aside from the energy lost in the pulley (depending on its efficiency), I think the same engine will still work.

 

[Josh111]

Thanks Airman.

 

[Airman]

I would still like someone to back me up on that. Does it sound right to the rest of you?

 

[Turv]

Airman,

Yes you are correct, the faster pulley will half the torque but the motor torque will remain the same.

Torque = Watts/ (2xpi x revs per sec) in Nm

the rest of your answer is correct also.