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

 

[jejeosborne]

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.

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)
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I am not trying to be pushy but I am still not understanding why your target rpm is 3740. Now that you have posted your generator info I still don't understand. In addition you mentioned that your mower was close enough at 36xx rpms when in fact I consider that perfect. I would suggest your target to be exactly 3600 rpms to maintain 60 hz frequency. Now if you want your days to fly by and go to bed earlier due to your faster running clocks, go ahead and run your generator at 62.33 hz like your planning. Your 24 hour day will fly by in 23.1 hours which many days I have desired this but you'll age quicker. Lol

What pto Hp is your tractor? If it is much greater than 18, I wouldn't start with 540 rpm either and would run the tractor at a reduced throttle.

 

[franklin2]

I found this design pdf. http://www.bandousa.com/html/pdfs/bu-143manual.pdf

Without getting into too much, I "think" you are going to at least need a "B" belt for the initial stage. I looked and looked and could not seem to find anything simpler. It all depends on the diameter of the pulleys and the design speed, and a bunch of other factors. I figured you might make the first stage 1 to 2 ratio, which would mean the second stage would be turning approx 1000 rpm.

 

[bigdeano]

I am not trying to be pushy but I am still not understanding why your target rpm is 3740.

The rpm under load will be less, depending on how good the tractor governor is. Everything should still work fine at 3740. Sorry if I stepped on anyone's toes.

 

[jejeosborne]

The rpm under load will be less, depending on how good the tractor governor is. Everything should still work fine at 3740. Sorry if I stepped on anyone's toes.

Are you saying to set the rpm at 3740 then? What happens when a load is lifted off the generator and the governor doesn't catch it quick enough causing even a higher frequency? The OP mentioned something about electronics and logic tells me to operate as close to 60 hz as a base line. I'm just wanting to express the importance of frequency and always try to achieve 60 hz plus or minus rather than 62.33 hz plus or minus.

 

[bigdeano]

Are you saying to set the rpm at 3740 then? What happens when a load is lifted off the generator and the governor doesn't catch it quick enough causing even a higher frequency? The OP mentioned something about electronics and logic tells me to operate as close to 60 hz as a base line. I'm just wanting to express the importance of frequency and always try to achieve 60 hz plus or minus rather than 62.33 hz plus or minus.

The OP is just going to have to try it under load and see how it behaves. They're are a lot of variables. The rpm can easily be adjust with the throttle for the best compromise.

 

[franklin2]

Most things don't care about frequency, as long as you are in the ballpark. I am thinking you will be most worried about refrigerators, freezers, and other appliances in the house. Even a computer can tolerate some variation. Those cheap square wave inverters are the ones that cause the problems, with all that noise and harmonics in the waveform. He might be off a couple of hertz, but it will be a smooth, clean, true sine wave.

My setup does the same thing. The tractor will vary about 100 rpm with the load variations.

We have several huge generators at work. All of them have v-12 diesel engines. Two of them are 2000 amp 480v 3 phase, and the other is a 1500 amp 480v 3 phase. They purposely run them a little slow or a little fast(I forgot to ask which way) so they can be synchronized and matched to the incoming power before they are switched for testing and such when we still have good power from the power company. I don't think it's much, maybe 1 hz or so.

 

[CNC Dan]

The rpm under load will be less, depending on how good the tractor governor is. Everything should still work fine at 3740. Sorry if I stepped on anyone's toes.

So 3740 RPM at no load, will bog down closer to 3600 under load.

In use I would set the throttle to run at 60HZ at half of expected full load.
Then as load changes, up and down, the frequency will change a little above and below 60 Hz.

 

[Kendrick]

The OP mentioned something about electronics and logic tells me to operate as close to 60 hz as a base line. I'm just wanting to express the importance of frequency and always try to achieve 60 hz plus or minus rather than 62.33 hz plus or minus.

of the load 3-4kw will be used for electronics so yes 60hrz is quite important to me. once i get a solar install in that supports batterys/gen it will be a bit more forgiving in that matter but for right now. it is important.The manual said 3400-3700 im guessing is the maximum tolerance now that it think about it, not it must run @ 3780 for best results.... if 3600rpm is what is needed to get 60hz then yes that's the intended target.

My DK45 is 40 or 42hp @ pto iirc so not an issue there. the govener is another story all together though I may stick a flywheel on it if need be to keep the speed. The gen setup will be aprox 2-3 feet off the ground 70 or so" wide what ever length is most conveniant at the mill if they have 1/4 or 1/3 steel plate thats 60" then it will get built 60" wide. about 2-3' deep I was planning to put the pto center of that and that would give 20-30" from center to the side for the first stage. the 2nd stage would go down as much as 20" diagnal fashion so that it would be in a foot or 2 from the side. the generator would be any where on the other side of the pto connection that would allow the belt to fit properly and angle/length be easiest to manage. the belts for the pto would be furthest away from the tractor side of the 60-70" side where as the gen belts would be closest to the tractor. a frame on either side of the plate would allow enough room for belts to go inbetween the plate and the outside edge so that a metal cage could be constructed to enclose the moving parts. i may use a mesh for around the leggs and possibly on top as well.

 

[franklin2]

They make 1800 rpm generators don't they? That must be what they are using on a "official" pto generator that you buy. I did a search on the web and they all have a small gearbox on the front, and it doesn't look like it could be much more than 1 to 2 ratio. It's not very big.

I thought "why re-invent the wheel" and thought I could find a factory setup, but none of them use belts.

P.S. I guess a 540 to 1800 gearbox would be closer to a 1 to 3 ratio.

 

[jejeosborne]

of the load 3-4kw will be used for electronics so yes 60hrz is quite important to me. once i get a solar install in that supports batterys/gen it will be a bit more forgiving in that matter but for right now. it is important.The manual said 3400-3700 im guessing is the maximum tolerance now that it think about it, not it must run @ 3780 for best results.... if 3600rpm is what is needed to get 60hz then yes that's the intended target.

My DK45 is 40 or 42hp @ pto iirc so not an issue there. the govener is another story all together though I may stick a flywheel on it if need be to keep the speed. The gen setup will be aprox 2-3 feet off the ground 70 or so" wide what ever length is most conveniant at the mill if they have 1/4 or 1/3 steel plate thats 60" then it will get built 60" wide. about 2-3' deep I was planning to put the pto center of that and that would give 20-30" from center to the side for the first stage. the 2nd stage would go down as much as 20" diagnal fashion so that it would be in a foot or 2 from the side. the generator would be any where on the other side of the pto connection that would allow the belt to fit properly and angle/length be easiest to manage. the belts for the pto would be furthest away from the tractor side of the 60-70" side where as the gen belts would be closest to the tractor. a frame on either side of the plate would allow enough room for belts to go inbetween the plate and the outside edge so that a metal cage could be constructed to enclose the moving parts. i may use a mesh for around the leggs and possibly on top as well.

Sounds like you are on the right page with the 3600 rpm target and that was my concern. Flywheel option would probably not be necessary unless you have a real large startup load. It won't be a benefit to your governor unless it is a very quick on/off load. If it is a continuous load, the flywheel energy and load will still need to be governed at the engine anyway.

Have you considered having your setpoint on your pto lower than 540 rpms? You have more than 2 times the necessary HP so you could throttle the tractor back from the 2500 engine rpm which is necessary to get your 540 PTO speed. At 2000 rpm engine speed, your pto would be at 432 rpm for example.