Generator hookup bulid and Belt / shiev questions.

[Kendrick]

I am getting started on a generator frame that will allow me to use both my tractor pto and my lawnmower to power the generator as needed. I am having issues finding some reasonable information about shaft sizing for the shievs. I also wonder if it may be more reasonable to use 2 steps from pto to 3740 rpm or if 1 step would be best. I plan to put a mechinisim in so that i can easily disengage the pto blt when I am running off of mower power so the pto set doesnt flop around as well as to save on wear on those parts. id rather have belts wear out than bearings.

1) where is a good shiev / shaft calculator or info that is easy to understand.

2) is the thoughts about the 2step to high speed vs 1. The system needs 20hp to get full use of the generator. the manual wants a 4-5" shiev on the generator.

 

[Baby Grand]

Assuming your PTO speed is 540 rpm on both?
3740/540 = 6.926, so about a 7:1 step up ratio.
If you want single stage & your genny sheave is 4", then you'll need a 7x4=28" sheave on the PTO shaft - not very practical.
Definitely consider a 2 step speed increaser.
First stage 12": 5" will get you to 1296 rpm.
(12/5)x540 = 1296
Second stage 12" : 4" will get you to 3888 rpm.
(12/4)x1296 = 3888
With this arrangement 519 PTO rpm will get you 3740 at the genny.
(3740/3888)x540 = 519

 

[Kendrick]

My pto is 540 on the tractor the mower will be direct dirive from the moter which is 36xx rpm which is close enough to needed speed.

thats about what i figured now for the big question how do you figure the size of shaft on the shiev's that is something i couldent find any good info on. my gen is 28mm shaft so I could easily go with that for all of them but was wondering what the proper method of calculating it would be.

 

[CalG]

Just stick with one shaft size (if you can), everything will be so much easier.

28mm in an Imperial world can be a *****!

 

[franklin2]

If the generator shaft is 28mm(1 inch is 25mm) I would go a little bigger than that for the other shafts. As the shafts turn slower and slower and you make your way to the tractor's 540 rpm, the torque is going to get higher and higher. The 540 input shaft can be the largest, the intermediate shaft can be a little bit smaller, and then you will hit the 28mm shaft. From the first shaft to the intermediate shaft, you made need double belts. Slow speed with lots of torque in that first stage.

 

[Brad_Blazer]

Just to be clear the shaft diameter does not affect the ratio. The shaft only needs to be strong enough to handle the loads. A lot the strength requirement depends on how the shaft is supported on it's bearings.

It is totally the size ratio of the sheaves or gears that determines the transmission ratio. A simpler option may be to get something like this that will get you close, then having to make just a small step up with the pulleys. SPEED INCREASER

Here is some belt selection info. You may want to use double or triple sheaves to transmit 20hp at 3600rpm.
http://www.emersonindustrial.com/en...missionSolutions/Catalog/Form_8586E_Sec_B.pdf

 

[jejeosborne]

Why a target of 3740? Unless you have an inverter generator you will be running at a speed divisible by the frequency depending on the number of poles your generator has. Also consider the rpm you plan on setting your tractor at. If the generator doesn't require the max pto Hp, I would consider running the tractor at a reduced rpm.

 

[franklin2]

Just to be clear the shaft diameter does not affect the ratio. The shaft only needs to be strong enough to handle the loads. A lot the strength requirement depends on how the shaft is supported on it's bearings.

It is totally the size ratio of the sheaves or gears that determines the transmission ratio. A simpler option may be to get something like this that will get you close, then having to make just a small step up with the pulleys. SPEED INCREASER

Here is some belt selection info. You may want to use double or triple sheaves to transmit 20hp at 3600rpm.
http://www.emersonindustrial.com/en...missionSolutions/Catalog/Form_8586E_Sec_B.pdf

The horsepower will be a constant. You can have the same power at a low speed or at a higher speed. The low speed will require a lot of force(torque), the higher speed will be less torque to transmit the same horsepower.

The slower part of his pulley system will have to be more heavily built. Larger shafts, double belts, etc. The last stage that drives the generator does not need double belts and large shafts, as is shown by looking at the design of the generator shaft.

Look at any gearbox or car transmission, the input shaft is small, the slower output shaft is very large compared to the input.

 

[franklin2]

Why a target of 3740? Unless you have an inverter generator you will be running at a speed divisible by the frequency depending on the number of poles your generator has. Also consider the rpm you plan on setting your tractor at. If the generator doesn't require the max pto Hp, I would consider running the tractor at a reduced rpm.

Most generators I scrounge up do run at 3600 rpm. I have a setup on my Kubota pto, luckily I have a 2 speed pto, the high speed is direct to the engine rpm. I wanted to run my Kubota in the neighborhood of 1500-1700 rpm. So I only had to approx double my pto speed to drive the generator I have. I bought a 12 inch diameter pulley and weld-on hub from tractor supply. My generator has a 5 inch pulley on it, and it's metric so I didn't want to have to mess with it.

 

[Kendrick]

Why a target of 3740?

NorthStar Belt Driven Generator Head 10,000 Watt | Generator Heads| Northern Tool + Equipment

have to be picky about rpm as it will be running electronics and I dont care to let the specs out of really good power.

Required HP 18 (3,480 - 3,780 RPM)

your looking at 200 ftlbs of torque @ the pto shaft 80 ish iirc at pully 1 and 30 at pulley 2 the one attaching to the pto I was suspecting I would have to attach a shaft to a square pto insert or possibly put in an appropriate keyway then round the square off. the other two not to sure about though.

at what torque should 2 belts start being used?

I found this site interesting as it gives a bit of info in many areas. Notes on Pulleys and Belts