Searching for a gearbox to drive with PTO, 1:6...

Glenn9643 · Sep 14, 2005

I've been searching for a gearbox with a speed increasing ratio to drive a generator head at 1800RPM without running the tractor at full PTO speed. I figure 1:6 ratio, with 300 PTO RPM would be about right for my tractor to drive a generator head requiring 30HP, but it's a pure guess. My 1455v is 47hp at the PTO I believe. If I can run it at 300PTO RPM it'll use a lot less diesel. I've not had any luck yet locating the gearbox, but looking at the rotary cutters on the Howse Implements site I saw this chart that says their medium duty cutter's gearbox has a 1:47 ratio.
At 540 PTO RPM the output spindle would be turning 25,380 RPM. Somehow I don't believe that's correct.
I believe it's probably 1:4.7.
Anybody have any ideas where a guy can buy something like I'm needing?

JerryG · Sep 14, 2005

Glenn,
Have you looked at Surplus Center . They have lots of gear boxes.

Taylortractornut · Sep 14, 2005

SurplusCenter has a few sets of pto gear boxes fairly cheap for certain applications. One thing we use here is an old transferr case off a 4x4 to with the pto connected to the output shaft on the transfer case with the input connected to the pump or gen head.that way the low gear becomes a higher gear.

Glenn9643 · Sep 14, 2005

Jerry, I’ve looked at the website and their paper catalog. I’m afraid if I go with a reducing gearbox (which is common) and apply drive power to the designed output side it won’t stand the torque and I don’t want to waste the money. I’d rather pay a little more and get something designed to hold up under the load if I can’t find a field expedient. I’ll keep checking back with them though, because you don’t ever know what they’ll have next.

Taylor,

Do you have any idea what the ratio is on the transfer cases?
And talking about applying the drive power to the traditional “output side”, what about a manual transmission from a junked car or truck? From what I can tell they gear down in the lower gears and “high” is usually 1:1, and overdrive gives a little increase. What do yo think about using say a 5-speed transmission from a pickup and applying the PTO drive to the output end? Then you would have several gear ratios to play with to find the most efficient for your needs. Would it hold up to the load with the load being reversed from the intended design?
Here’s what I’m interested in doing. A 15KW or 24KW genny head from Http://www.oldstylelisters.com/st_heads.html.
I know I can buy a 12KW PTO Gen set from Northern for $1100 or so, but it has to run at 540. At 540 my tractor drinks a lot of diesel. 540PTO RPM on my tractor is about 2600 engine RPM. If I can make one up that I can run at 2000 engine RPM or a little less it’ll cost a lot less to operate, and if there’s a requirement to use it fuel costs can mount up pretty quick. I also believe this generator head will be easier to work on if necessary. Changing brushes isn’t rocket science. Look at the difference in the weight of this one vs a 12KW Northern Tools... From what I’ve been able to find and read I would rather have the ST-15K at the above website I think. There’s less to go wrong, and if it goes wrong it’s not that difficult to fix.
I had thought about trying to drive it with pulleys and V-Belts. Communicated with SoundGuy about that and have about decided against it. 30HP or so is a pretty good load for belts.

Soundguy · Sep 14, 2005

One thing I was thinking about.. won't fuel usage be based on load? That is.. if the genny is using 30hp.... it's using 30hp... rpm not making much bearing ont he fuel used to make that 30 hp?

Sounds like you are going to alot of trouble to make a rube goldberg style contraption to drive a slightly less expensive genny head, vs simply getting a gear drive genny that is a no muss / no fuss deal.

I don't recall seeing any tractor gensets that drive off of anuthing but gearbox.. When i see engine coupled gennies.. it is usually direct couple, with engine governed at geny rated speed, based on number of poles... etc.. same for welder/gennies.

Soundguy

rdbrumfield · Sep 15, 2005

Keep it simple. Any 3-4 speed tranny would work by driving the output end of it and connecting the input shaft to the generator. Just use the gear suitablem and adjust rpm for your needs.

California · Sep 15, 2005

( any idea what the ratio is on the transfer cases? )

The original Jeep transfer case was about 2.5:1 and the later 'silent' transfer case, after about 1970, was about 2:1.

Taylortractornut · Sep 15, 2005

Yep a 3 0r 4 speed that is hooked up the same way will work to. that would dfinatly give more speed controls. I took an old varialbe speed belt drive off an old MF combine and make it work on a pto to run a gen head a few years ago for a friends grandad.

TBone · Sep 16, 2005

Glenn,

A company called Drummond makes pto generators that put out maximum output with 460 pto rpms. I don't know why others don't design theirs the same way. It seems like overkill to run a 50 hp tractor wide open to turn a small generator that only needs 20hp.

Here is a link to one of their generators for sale on EBay. They make a good pto generator (brushless, self-exciting, clean power) that mounts on the 3ph but they ain't as cheap as Northern Tool and places like that.

Good luck - I am interested in one I can use on my tractor but I would not buy one that would require running my tractor at high rpms continuously either.

PTO GENERATOR

TBone

Soundguy · Sep 21, 2005

( It seems like overkill to run a 50 hp tractor wide open to turn a small generator that only needs 20hp.
)

If I had a 50hp tractor.. I'd get the 24kw unit that needed 48 hp..

I'm not sure what genny you have that only needs 20hp.. My 12.5kw unit needs 24 pto hp.

I have seen 7 an 8 kw heads that would need 13.4 and 15.3 pto hp respectively.

Rather than complain about how the pto gen is setup.. it would be better to size your gen to the load and available tractor hp. 540 pto rpm puts a tractor in its power band.. if you need hp.. that's where you want to run it, imho

Soundguy