Need Some PTO-Driven Generator Advice

[rrausch]

OK... I've got a tractor with a variable speed PTO which I am mounting a PTO driven 4000 Watt Generator on. OK, the PTO will be turning at around 430 RPM and the Generator has to turn at exactly 3600 RPM.



I am running a u-joint shaft off of the back of the PTO and then through a 2:1 increasing gearbox and then going from a big pulley to a little pulley, which will get the RPM's up to around where I need them.



But the question begs... how can I tell when the Generator is turning at EXACTLY 3600 RPM. The generator is a Winco, industrial design, with a voltmeter on it. Can I rely on the voltmeter? Or is there some sort of inexpensive tach-o-meter I can get? Or will some other type of electronic volt/amp/watt/ohm meter be sufficient to tell me when the RPM is exact?

I don't want to burn out my saws!

 

[illflem]

Ever notice that electric motors and generators run at multiples of 60? It's because it's the 60 cycles per second you're looking for, most average voltmeters don't measure hertz. If you run at the wrong rpm your 60 cps will be off. I have a digital infrared rpm meter, $39 from Harbor Freight that works great. Sled Puller used it to set his PTO speed for much the same thing. There are also low price hand held tachs that touch on to the rotating shaft if that is possible for you.

Here's something that may throw a monkey wrench into your calculations, some older tractors, you didn't say what you have, have a gear right behind the PTO shaft that is easily reversed to give you 1000 rpm. That will let you run the tractor at a more fuel efficient rpm.

 

[rrausch]

Illflem, it's a rusty old Farmall H that I put a new motor in in '96. (Should be good for another 50 years!) I use it mostly for bush hogging, and for lifting things up in the air with the Du-Al loader, but will also use it for running the Gen. Thanks for the offer, I'll e-mail you.

 

[Skydiver]

Try this.

rrausch,

Get an anolog 110 volt clock with a second hand and plug it into the gen. 110 volt clocks use the cycles per second for the actual time keeping. Use a stopwatch along with the clock to tell if the gen is turning too slow or too fast.

On non-electronic items it won't hurt to be between 57 and 63 seconds per minute on the analog clock.

I wonder if this would also work on a digital 110 volt clock?Never tried it.

Will need to keep the voltage between 108 and 128.

Hope this works.

Tim

 

[rrausch]

Great idea Skydiver, thanks! I had forgotten about a/c clock motors.