Setting up generator off PTO

loaderman18 · Jan 1, 2009

Would like to know if anyone could tell me what sprockets to use to run my generator off my pto. I have a 540 pto and want to run my 10kw gen head with it. the gen needs to run @ 3600rpm. Since 540 goes into 3600 6.66 times, if I use a 2" dia sprocket on gen and a 13 1/2" on shaft it will turn my gen @ 3600. Am I not thinking right or will this work? Any help would be greatly appreciated. Thanks!!!

RodinNS · Jan 1, 2009

If you've got a ratio of 6.66 to 1 then you need a drive sprocket with 6.66 times as many teeth as the driven sprocket.
Tooth count is the way to deal with sprockets, not size though there is probably a mimimum size driven that you would want...
It's not really too critical with a 10KW unless you're running it with a very small tractor.
I would suggest that you stick a multimeter in a receptacle once you have it up and running and set your engine speed such that you achieve 60 cycles on the multimeter.

Rod

RayP(MI) · Jan 1, 2009

A multi-meter probably won't give you the frequency, unless it has a freq counter. There are frequency meters available, however. Since you are running it off a tractor, you can vary the throttle position some to get the necessary 60 cycles. so your math on the gearing doesn't have to be that exact. I would suggest a double shiv (2 belt) V-belt drive instead. This may be easier to match pulley dimmensions, as the math in the above post.

loaderman18 · Jan 1, 2009

So diameter doesn't mean anything? My shaft sizes are both 1" so I was considering the rpm @ the shaft. I'm not an engineer by any means, i'm trying to use common sence.

Paul from MI · Jan 1, 2009

Most multimeters won't tell you if you are on 60 cycles or not since they only measure voltage. A cheap simple way to tell is to plug in an old style electric clock(not digital) with a second hand. Compare the speed of the second hand on the clock to the second hand on your watch and alter the speed of the generator so they match. I used this method for years without problems with my tractor driven generator.
Paul

john in la · Jan 1, 2009

I would also use a V belt setup rather than gears.

The gear diameter does not mean much but the ratio to the two gears does. In other words you do not need a 2" you could use a 3" but would have to change the other gear to a larger one also.

Fixer · Jan 1, 2009

Another thought. I would set it up so the tractor didn't have to run full throttle to keep the generator at proper rpms. Bernie Steffen

IaGary · Jan 1, 2009

How big of tractor are you putting on it?

You could gear it higher and then not have to run the tractor at as high of RPMs if you have enough HP.

And the ratio is figured on circumference of the sprockets and not diameter as others have said.

loaderman18 · Jan 1, 2009

I HAVE A 20 HP COMPACT, SO I AM PLANNING ON RUNNING @ SPEED. I WAS ALSO PLANNING ON ROLLER CHAIN AND SPROCKETS, NOT DIRECT DRIVE.

RAW in IA · Jan 1, 2009

The ratio is the same figuring circumference or diameter.

RodinNS · Jan 1, 2009

Cheap don't.... FLUKE does.
Mine spent several hours today sitting in the socket. Come to think of it, I forgot it when I shut the gen down and it's there yet.
You can also set them pretty close by voltage if you know what voltage it makes when it hits 60 cycles.
I've never had any trouble just setting ours to 540 on the shaft and goig with it, but I do like to keep an eye on it no less...

Rod

IA Roy · Jan 1, 2009

If you are determined to use chain and sprokets instead of a belt drive, have someone who has done some driveline design look over your plans. There are a large number of things to be considered on chain drive. At 3600 rpm, a 2" sprocket is probably too small. The drive will not be as smooth if the sproket is too small. The ratio of 6.66 to one has to be figured into the calculations. The number of cylinders the engine has changes the service factor in the calculation. A chain drive needs to be lubricated. A belt drive does not. Sprocket alignment is more critical than pulley alignment, although it should be as close as possible. Noise is also a consideration. The nosier the drive, the less efficient.There are many other considerations. Please take all these things into your decision.

Don-Wi · Jan 1, 2009

I'd go with the approx. diamter of the sprocket or pulley. I would also consider using a jackshaft and step it up 2x, instead of once. Then the sprocket or pulley doesn't have to be as big of a diameter. The flip side is you'd need 4 sprockets instead of 2.

If you measure circumference or diameter, you'll get the same ratios. Could use radius if you really wanted also.

Donovan from Wisconsin

RodinNS · Jan 1, 2009

DOH!!
You like trying your luck a bit, eh?
Definitely figure out where maximum power is on that engine and do your gearing so that you have the tractor running at it's point of maximum power or just above it's peak. That will be a load on it.
Personally I think I'd run sprockets as you're planning rather than belts. You really can't afford the friction losses on a belt with the power you have, on top of which if you have snow or rain you'll have wet slipping belts. Gears would be better again, but sprockets are cheap and easy.
I think I'd go with a #60 chain and a 12-15 tooth driven sprocket, so that will leave the driver between 80 and 100 teeth give or take a tooth or two.
You could probably get by with less (smaller pitch) chain... if you can source good reliable chain (lol), or conditions are perfect. Load cycles on generators can apply so pretty big shock loads, so you really need some overkill in the drive unless you like fixing it in the dark.
Some resistance to shock loads would be the main benefit to a belt drive, but you need to keep it dry.
I think the shaft sizes you're talking about are fine for the power you're dealing with. Other than that the shaft size doesn't really matter beyond getting the corect bore sprockets.

Rod

Janicholson · Jan 1, 2009

Reverse a small manual transmission to drive from output to input. Many have a gear in the range needed. Fluke meters do read frequency.
Another way is to use a laptop with Zelscope software (20 $) download. 20 days free. Then use a ) to 20K Ohm variable resistor (pot) to vary the input voltage into the audio in (mic) jack. Start with high resistance, and set the wave form to be stationary at 60HZ. JimN

John B. · Jan 1, 2009

If you're using sprockets count the teeth on both of them and divide the drive sprocket into the driven sproket.This will give you your ratios. It's just like using gears.

The bigger the drive sprocket the faster the driven sprocket will run providing you didn't change the size of the driven.

If it were me I would be using belts. If you have an 8 inch drive pulley driving a 4 inch pulley the 4 inch pulley will turn twice as fast. This is the easiest way to explain it but there are other calculations for figuring it. I just tried to put in the simpliest term.

If you use whole numbers such as a PTO speed of 400 you would need a ratio of 9 to 1. Generator would turn 9 rpms for every 1 rpm of the pto. You're talking some series size pullies for this.

If I'm wrong someone please correct me.

buickanddeere · Jan 1, 2009

Unless the chains are running in an oilbath, forget it. Either belts or the gearbox.
Best & cheapest solution? Quit trying to make a silk purse out of a sow's ear. Sell the existing generator and find a complete pto generator at a farm sale or somewhere.

teddy52food · Jan 1, 2009

The RPM's x the # of sprocket teeth of one will equal the RPM's x the # of sprocket teeth of the other.

Anonymous-0 · Jan 2, 2009

Did your gen. used to have its own engine? Using chains or belts to run it could make it self destruct if the bearings are designed for side loading. The same thing is true for hydraulic pumps and motors. Chain ratios are determined by the number of teeth. Double V belts might be a better set up? Another thing you could do is adapt a right angle gear box off of a mower or something similar. You could use a portable tach to check rpms and once you find where 3600 is, make a mark on the tractor tach. Dave

Anonymous-0 · Jan 2, 2009

Commercial generators run a gear box, wonder why?
Find one and you wouldnt regret it.

J.Wondergem · Jan 2, 2009

I used to use a small portable TV set. Plug it into the generator, and watch the picture. The picture will roll down, then speed up to where the picture will stop rolling. Too much speed if the picture rolls up. Jack

Brian Jasper co. Ia · Jan 2, 2009

A few years ago I saw at the Orange Spectacular show in Hutchinson MN some one was using a B Allis power unit with a chain drive to run a generator. To say it was noisy was an understatement. They used a spring loaded tensioner to keep the chain tight. With the mass of the generator's rotor and probably varying electrical loads and maybe engine speeds, the chain kept bouncing. I would find a pto generator for reliability. If you're bound and determined to make what you have work, use belts with a rigid tensioner, or no tensioners at all.

Setting up generator off PTO

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