Generator contraption (safety conscious stay away)

[getut]

Ok.. I've noticed the generator threads firing up again (with good reason with Katrina looming) and my interest is also gearing up again.

I have thought of a cheap but slightly dangerous way to build a generator. I myself can live with the risk, so with that in mind here is my idea:

Take a standard brush cutter like my Kioti 5' cutter and disconnect the U-joint at the cutter side and mount a belt pulley of correct size in between the gearbox and the U-joint when it is put back on.

Manufacture a removeable carriage/mount for one of the cheap belt driven generator heads available at various places and with the correct calculations put the matching pulley size on it for correct speed. Drill and install studs in the surface of the cutter (in sufficiently beefy locations) and make slotted holes in the genny head carriage so that the carriage can be slid back and forth for belt tension.

Of course I would drop the tail wheel all the way down and maybe set some saw bucks up at the rear of the cutter, but this seems like a very workable idea. The cutter would even act like a massive flywheel to pull the generator through peak loads.

I havn't done calculations, but I think the only limitations may be pulley size because of the slow spinning pto shaft.

 

[Donman]

I can't visualize how the pulley would connect to the shaft without some kind of spline and leave enough room to put it back together. If you had one of those pulley driven finish mowers you'd be further ahead.

 

[Jagmandave]

I think with a little ingenuity it might be possible to slide on a pulley on the splined end. I could see this working OK, if you were concerned about the blades, take them off, but leave the pan as a flywheel as mentioned.

 

[Taylortractornut]

Depending on your mower most of the brush cuters have a shear pin. The input shaft on the mower has a 1 and 3/8ths shaft that has room for a set screw and a thin puley. I have also bored out a pulley to fit the collar of the pto shaft. then pin it wih a longer shear pin. Getut and old Woods mower with the pulley on the back thatwas horizontal that had the belts that turned down to the spindles. You can take one of them and remove the spindles and make a genhead bracket. That way you could have a stand with rollers and a safer generator mount with bearings already installed. I think someone here made a leafblower like that to.

 

[Jim_in_Omaha]

If you get a 4 pole gen head it is 1800 rpm, while 2 pole is 3600 rpm. The low cost units are typically 2 pole. To get your 540 up to 3600 is around a 6.7:1 ratio. So if you have a 2 1/2 pulley on the generator and a 16 3/4 on the shaft for the 2 pole unit. I guess if you have room from the shaft of the gear box to the top of the deck for around 9 inchs it would fit. If you have too small a pulley on the generator and your running standard V belts, they may not have enough surface area on the pulleys during peak loads and slip.

Surpluscenter.com has an excellent selection of 2 belt pulleys that would cover the sizes and they are not that expensive.
Jim

 

[Charlie_in_TX]

....So if you have a 2 1/2 pulley on the generator and a 16 3/4 on the shaft for the 2 pole unit...

Your math is off by 2. With a 2.5 in pully on the gen you would need a 8.375 on the pto shaft for a 2 poll.

That does bring up another problem you mentioned though. If you are running a 5000 watt generator, you will need 10 hp thru the belt/pully. You will need beefy double-v pullies at 2.5in or the flat belt (like a harly).

 

[Slamfire]

I'm waitin' for photos. My gas engine has pretty much worn out on my 8kW unit after 9 years and I'd love to replace it with the old draw type cutter just rustin' away in my yard. /forums/images/graemlins/grin.gif

 

[Jim_in_Omaha]

</font><font color="blue" class="small">(
Your math is off by 2. With a 2.5 in pully on the gen you would need a 8.375 on the pto shaft for a 2 poll.
)</font>

This is the math I was using. Maybe it is feel good math or something.
PTO dia / GEN dia * PTORPM = GENRPM
8.375 / 2.5 * 540 (pto) = 1809 (4-pole generator)
16.75 / 2.5 * 540 (pto) = 3618 (2-pole generator)