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Cub Genset

Wed Oct 31, 2012 4:59 pm

Hello Everyone,
Being the power is out and we are being told that it will not be restored for another 7-10 days I got to thinking. In the Northern Hydraulic Tools magazine I saw that they have 3500 watt generators that are made to run off a pulley. They say that they need at least 6hp to run at pull output. From what I can tell the Cub will have more than enough power to run that and the pulley could be run off of the PTO being that a Cub pto runs at engine speed and not 540. My real question is this a feasible idea? Has anyone ever done something like this? It seems like it would fairly easy to pull off and would be great to find yet another use for the Cub.

Thank you,
A.J.

Re: Cub Genset

Wed Oct 31, 2012 5:03 pm

AJ the cub pulley 3 times larger in diameterthan the cub pulley does the speed change for you.

Re: Cub Genset

Wed Oct 31, 2012 5:34 pm

Just so I am understading you, you mean that I need a pulley on the pto, three times larger then that normal pulley?

Re: Cub Genset

Wed Oct 31, 2012 6:07 pm

Bit of a math problem. Most generator heads operate at 3600 rpms. You need to leave your engine with a bit of room/more throttle to adjust the rpms up or down. Generator head rpms determine output voltage. I have the feeling that a Cub's throttle settings may not be accurate enough to precisely set the engine rpms.

I have the 10 KW generator head featured in Northern Tool, powered by a 25 hp Kohler engine. When I did the math on pulley sizes I anticipated running the engine at about 2400 rpms. Throttle on this engine is infinitely adjustable. Periodically I check the generator head's output voltage with a multimeter. The reason I build the 10 KW generator set was because I had all of the parts on hand except for the generator head; engine, trailer, metal, etc..

My thought is that it will be cheaper to buy a slightly used generator set at auction. Wait until the power outage is over and there will be a bunch of generator sets listed in the newspaper, for sale. Next thought is that it will be cheaper to buy a complete generator set that to build one.

OK. Rather than using the Cub to power a generator set, I would use a single cylinder engine, Briggs, Kohler, with a bit more horse power than required.

Re: Cub Genset

Wed Oct 31, 2012 6:10 pm

I agree with Eugene. In about 2 weeks, go to Lowes and buy one that someone used for a week and returned.

Re: Cub Genset

Wed Oct 31, 2012 6:22 pm

I used the three times larger pulley on the generator than on the PTO because you seemed to indicate the gen set you were looking at needed 540 RPM. This ratio slowed the Cub !800 RPM to about 600 RPM. If as others suggested you have a Gen set the needs 3600 RPM you need a pulley twice as large on the PTO as the one on the generator.

Re: Cub Genset

Wed Oct 31, 2012 6:41 pm

thank you all for your replies. While I have a nice running 5000 watt one already. This idea was more to do as a possible project and was courios as to what issues i might run into. Thank you all for your answers, as I can now see there are some issues and numbers that need to be looked at

Re: Cub Genset

Wed Oct 31, 2012 7:11 pm

I wanted to do this same project just more for fun than anything, but someone mentioned to me that it would be hard to keep it at the right frequency? Whatever that mean.... They said to much rpms and it's too high and too little...well then it's low. And they said if the frequency wasn't right you could burn you appliances up. I don't know as I'm not big into technical detail stuff. Any more thoughts on. This would be interesting. Im gonna keep watching this one :D

Re: Cub Genset

Wed Oct 31, 2012 7:55 pm

Chris D wrote:They said to much rpms and it's too high and too little...well then it's low. And they said if the frequency wasn't right you could burn you appliances up.
If you own or plan on building a generator set, keep the output voltage at the rated voltage, plus or minus 5%. So, rated at 120 volts, some where between 114 and 126 volts. Closer to 120 volts the better.

Frequency. Some appliances such as electric clocks, frequency is critical to keep accurate time. Other appliances such as heating elements, electric motors, not so much. When stationed in Germany we use a transformers to drop the local 50 cycle electric current to 110 volts, 50 cycles. Most of our appliances were wired for USA voltage/frequency (120 volts/60 cycles) worked just fine, perhaps just a bit slower.

Re: Cub Genset

Fri Nov 02, 2012 7:55 am

Eugene wrote:
Chris D wrote:They said to much rpms and it's too high and too little...well then it's low. And they said if the frequency wasn't right you could burn you appliances up.
If you own or plan on building a generator set, keep the output voltage at the rated voltage, plus or minus 5%. So, rated at 120 volts, some where between 114 and 126 volts. Closer to 120 volts the better.

Frequency. Some appliances such as electric clocks, frequency is critical to keep accurate time. Other appliances such as heating elements, electric motors, not so much. When stationed in Germany we use a transformers to drop the local 50 cycle electric current to 110 volts, 50 cycles. Most of our appliances were wired for USA voltage/frequency (120 volts/60 cycles) worked just fine, perhaps just a bit slower.



Keep in mind that many appliances are controlled by electronics these days, which are very unforgiving of large variations in voltage/frequency

Re: Cub Genset

Fri Nov 02, 2012 9:44 am

Motors in washers and dryers are induction motors and the speed of those is dependent on the Hz of the AC power supply. A 60 Hz motor will usually run OK at 50 HZ but will run slower, at about 83% of the nameplate RPM. So washing the clothes will take longer, the dryer blower and drum will run slower. The dryer heating element is happy with either of the frequencies.
Most VFDs/inverters have 3-phase output and would not be useful for this situation. But a single phase inverter ( I do not know where to buy one of those as a stand-alone item ) could be a great solution. The inverter takes the input power, converts it to DC, then "manufactures" the desired AC from that. So an inverter could deliver 60Hz from a 50 Hz input.

Re: Cub Genset

Fri Nov 02, 2012 6:42 pm

So from what I can tell from these answers, this cub mounted generator would/is possible if I can find a way to first increase the speed to run the generator at required speed. I then next need to make sure that the engine can be run at a constant rmp that will allow the generator to produce constant power. Also if this is achieved it will keep the issues to a min with frequencies and other possible problems. If I am missing something major please chime in. This is a project I would really like to attempt and find a way to make it work.
Thanks
A.J.

Re: Cub Genset

Fri Nov 02, 2012 7:27 pm

DelValCub wrote:If I am missing something major please chime in.
Nope. Not missing a thing.
Frequency in most small generator sets is rpm dependent. So basically, if you can set the voltage at 120 or 240, you are good to go. We operated a generator set for 10 days straight on one occasion and close to 5 days straight on another with out any problems in computer controlled appliances.

OK. On my generator sets the engine rpms can be adjusted manually in very small increments. On your Cub, you will need to find some method to adjust the throttle in minute increments so that you can accurately set the generator head's rpms/voltage.

Thinking. 6 hp to power the generator head. I would start out by checking the engine rpms starting at 1/2 throttle, testing each notch up to about 3/4 throttle. Once engine rpms are established at each throttle position, determine the possible pulley combinations to get the generator head to operate at or closest to 3600 rpms.

Minor engine rpm tweeks at the throttle linkage to governor.

Re: Cub Genset

Fri Nov 02, 2012 8:22 pm

Eugene, thank you for your reply. I think I am going to do some investigating as to the rpm's of the engine and how steady they will stay. I will also then look into pulley arangements. Then maybe I will attach it to a generator head. Thank you all for your replies, you have been more then helpful.
Thanks,
A.J.

Re: Cub Genset

Fri Nov 02, 2012 8:57 pm

Not a generator expert but won't the size of the electrical load applied have an effect on the engine speed thus the generators output? Will the Cub's governor be up to the task of keeping the engine speed constant under varying electrical loads?
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