BTX24 mid PTO generator drive question

[Soundguy]

And at 6.5kw... the 10kw genny head ought to last ..

Soundguy

 

[Skyco]

Actually there are some caveats with the HF "10Kw" generator- 10Kw is MAX while continuous is rated at 7.2Kw so we aren't far off. HF claims 16 HP needed to drive it, presumably at the max of 10Kw. Kubota claims 17.7 HP at the PTO output on my BX24.
Granted there will be some losses in the added ratio changes to get 3600 RPM at the generator shaft. Kubota rates the mid shaft at 2500 RPM at 3125 engine RPM so dropping the mid shaft PTO RPM to 1800 would equate to 2250 engine RPM, then a 2x increase in speed to the generator via belt/sheaves. Not sure where this falls on the torque curve since apparently Kubota doesn't publish them. If the engine does indeed need to run at 3125 to get maximum torque/horsepower then the ratio would have to be adjusted to less than 2x.

I don't want to use the rear PTO because 1> I don't want to to take the BH off and 2> the gearing step up from 540 to 3600 would be even more difficult

Yup I'd rather have an 1800 RPM generator but the HF one when on sale is a deal

 

[Skyco]

Tracked down the part numbers for the factory coupler and it is $151
The whole shaft is $221 - I didn't pay much more than that for the whole freaking generator
I think I'll dig deeper into using generic parts and the adapter sleeve that is about $25.

Well I wore out my "shovel" digging deeper for a suitable/cheaper way around buying the factory setup Could not find a way to easily drive off the front PTO since it is an odd size...got a adapter in after 3 weeks on order to step it to the 1 3/8 6 spline "standard" configuration, then I couldn't find a 6 spline universal joint end that didn't have a quick release button...and even if I did how would I secure it? The adapter is made to be pinned on and of course there is no hole in the OEM pto stub to pin it and then no groove in the adapter for the quick release...

So off to get prices online for the complete factory Kubota drive shaft off a mower, lists apparently for something like $220+ but I did find one dealer to sell it to me for $200 shipped so in a weak moment I ordered it

Stay tuned....

 

[tommu56]

Skyco
I didn't think of it before what about a 1800 rpm generator and no belts?

what about cross drilling the yoke and use a 1/4" bolt and nylon lock nut?


tom

 

[Skyco]

An 1800 RPM generator would be better but they cost way more than the Harbor Freight unit on sale

Cross drilling the yoke would also entail cross drilling the PTO shaft- not a task I would take lightly...besides trashing the warranty I bet that is some hard metal to drill....

 

[Skyco]

Discovered a quirk in Kubota's PTO strategy...the safety systems won't let you engage the mid-PTO when off the seat! The rear PTO- yes you can. The manual doesn't mention this in the procedure for using the PTOs off the seat..had me head scratching awhile since I was following the procedure in the owners manaul exactly but it kept killing the motor. One cannot engage mid only or a combo of mid and rear and get off the seat.
So...I suppose I'll get my service manual ordered pronto to look at the wiring. In the meantime, if I get my mid-PTO generator finished I'll have to strap down the seat switches to fool it..

 

[Volfandt]

Discovered a quirk in Kubota's PTO strategy...the safety systems won't let you engage the mid-PTO when off the seat!

Not a quirk, just another added level of protection for those that have never operated dangerous machinery before.
There are two switches under the seat. One is a std on/off plunger and the other is make/break/make lever switch.
If one had the need to bypass the safety switches for TESTING purposes, one can make up a shorting plug for the plunger switch and tie wrap the lever switch in the middle position, ones mid PTO will run when one lifts their rear off the seat. One would also be able to depress the HST pedal & drive the tractor forward and/or reverse also, so be careful with this TESTING mod.....

 

[Soundguy]

Not to rain on anybodies parade.. however.. i'll bet this project easilly ends up costing as nearly much or more than a pre-fabbed unit in the same hp/KW range... and with way more fabrication and work.

I'm looking a tthe northern 7kw pto unit as a comparison.. etc..

Soundguy

 

[DiezNutz]

Not only that, but stepping up the rpm X2 to run the generator is also going to reduce the effective HP (torque) to run the generator by a factor of 2 (also ignoring any additional frictional loss). Assuming the torque curve is linear (for lack of any other data), at 1800 rpm the PTO HP would be 12.7 (leaving only 6.85 for the generator). In reality the curve is probably more flat, but you would expect to get significantly less than 17.7 HP at 1800 rpm.
All of these things conspire against getting little better than 5kW output when all is said & done.

 

[Soundguy]

Any idea whether the pto hp number kubota publishes is for the rear pto, mid or both?

Soundguy