How to adapt gas engine to 540 rpm's to generator??

[jburd964]

I purchased a 15kw PTO generator and have a tractor. I also have a practically new 30hp Kohler engine that I'd like to use. I'm going to go into a little bit of useless info to possibly prevent someone from making the same mistake I made. Back in 2005 I bought a Generac stand by generator. It had automatic start and would transfer power within 20 seconds of lights going out and ran on natural gas. I live in SW Louisiana and used it after hurricane Rita and a couple other occasions. It would run a self check once a week by starting and going through the motions of a actual power failure to check for problems. I did this regularly without any problems. Then in late summer of 2008 we had another storm come through and it ran for like a hour and shut down. I did all the trouble shooting I could to no avail. After weeks of trying to get a service call they showed up and charged me $150 for a thirty minute service call to tell me that the windings had came apart. The whole set up including installation was around $8000. (#&$(#*.. Saying all of that to tell you the reason the generator was reasonably priced is that they cut one major manufacturing cost. Not using copper wire, but use aluminum wire with a copper coating that expanse to much for reliable use. Hopefully this will save someone somewhere the price of my lesson. But back to my project. The generator requires a 30hp engine and that power to be transferred to 540 rpm's. I'm wondering if I could find a transfer case of some type that would have spline drive inlet and out. How could I do this as cost efficient as possible.

 

[J_J]

In order to run the PTO generator at 540, you will need to reduce the engine 3600 rpm to around 540, which will require a reduction of 6.666. You need to consider that with a load on the generator, the generator will pull down the engine rpm, and if you are already running at 3600 engine rpm, then you should only reduce the engine down with a 6:1 ratio, which will allow you to run the generator up to 600 rpm for those extra rpm's under load. There are circuits that will adjust the engine rpm to match the generator rpm's necessary to provide the correct voltage.

With the smaller reduction, you will not have to run the engine at max rpm to get correct generator voltage. The 6:1 ratio, will let the engine run at 3240 and the generator to run at 540 rpm.

Automotive axle ratios are in the range of 2.71 up to 4.31. Surplus Hydraulics has gear boxes with a 5:1 ratio, but none around 6:1. The 5:1 ratio will allow the generator to run up to 720 rpm with the engine at max, but I don't know if the generator will take that kind of rpm.

You might come across a differential to meet your needs. Other ways for reduction is with belts and pulleys, or sprocket and chain.

 

[rjmack]

what about a 4speed transmission and transfer case combo out of an old 4x4.

you have splines in and out, and if you put the t-case in low range, there must be some combo that will give you something close to what you need.

 

[brokenot]

After weeks of trying to get a service call they showed up and charged me $150 for a thirty minute service call to tell me that the windings had came apart.

There are lots of places that can do a rewind if new parts are cost-prohibitive.

Here's one example:

Eurton Electric | Motor Rewinding & Parts

Their site says motor rewinding, but they'll do rotors and stators for gensets too. Going that route will be much easier than adapting several mis-matched components together. Download their complete rewind catalog and take a peek....they do have a couple of generator pages that can give you some ideas on pricing.

 

[jburd964]

Thanks for input. Sounds as though you have a better understanding of gear reduction/rpm required then myself. The gear & chain or belt pulley sounds feasible.

 

[jburd964]

The new part is $1000 plus labor and I figured I'd be no better off then when I started. If it was rewound that would include the stator as well to remove all aluminum at best guest .but still no guarantee

 

[alco141]

first thing to do is call the manufacturer and complain a lot, let tem know how unhappy you are about the shoddy manufacturing process they used, talk to the supervisory personnel and go to the big boss , they may give you a deal on the repair. this is a substandard manufacturing process, and needs to be addressed. i would not let this go without voicing my displeasure to the powers that be, write a letter, make some noise, you may be pleasantly surprised at the outcome, what is doing this cost you?

alex

 

[lostcause]

i'm going to question the reduction ratio... i didn't see the original poster mention 3600rpm, though i may have missed it somewhere. generally small gas engines (sub-10hp) are in the range of 3600rpm, but most of the larger 15hp & up ones i've seen are meant to run closer to 1800rpm speed. at that speed you'd be looking at more of a 3:1 or 3.5:1 ratio. again, i'm just guessing as to the engine. it could be 3600rpm, but i'd bet closer to 1800.

i know it doesn't seem as elegant, but i'd go for a belt drive. i assume there is a straight shaft on the engine, and maybe there's a way to put a pulley system on the generator head? enough of a straight shaft before the splines? i don't know what you can find easily for pulleys and belts, but for that kind of power i'd think it would require a larger than normal v-belt, or a multiple belt pulley setup? again, just guessing. i'd bet that there are some small engine shops that could make suggestions based on what they may have seen. if it is an 1800rpm engine, a 3" pulley on the engine and a 10" pulley on the generator would be exactly 540rpm at the generator.

 

[aczlan]

first thing to do is call the manufacturer and complain a lot, let tem know how unhappy you are about the shoddy manufacturing process they used, talk to the supervisory personnel and go to the big boss , they may give you a deal on the repair. this is a substandard manufacturing process, and needs to be addressed. i would not let this go without voicing my displeasure to the powers that be, write a letter, make some noise, you may be pleasantly surprised at the outcome, what is doing this cost you?

You might get lucky and they might replace the whole unit for you. Then you could sell it and get another one.

Aaron Z

 

[J_J]

i'm going to question the reduction ratio... i didn't see the original poster mention 3600rpm, though i may have missed it somewhere. generally small gas engines (sub-10hp) are in the range of 3600rpm, but most of the larger 15hp & up ones i've seen are meant to run closer to 1800rpm speed. at that speed you'd be looking at more of a 3:1 or 3.5:1 ratio. again, i'm just guessing as to the engine. it could be 3600rpm, but i'd bet closer to 1800.

i know it doesn't seem as elegant, but i'd go for a belt drive. i assume there is a straight shaft on the engine, and maybe there's a way to put a pulley system on the generator head? enough of a straight shaft before the splines? i don't know what you can find easily for pulleys and belts, but for that kind of power i'd think it would require a larger than normal v-belt, or a multiple belt pulley setup? again, just guessing. i'd bet that there are some small engine shops that could make suggestions based on what they may have seen. if it is an 1800rpm engine, a 3" pulley on the engine and a 10" pulley on the generator would be exactly 540rpm at the generator.

If he is talking about this 30 HP Kohler engine, then it will run at 3600 rpm.

Kohler Engines: CH750: Command PRO: Product Detail: Engines

Even the Kohler diesel runs at 3600 rpm.

http://www.kohlerengines.com/onlinecatalog/productDetail.htm?productNumber=KDW1003

What is the model number of your Kohler?