Fully Hydraulic Tractor

[JoelD]

I've been wondering for some time, why aren't tractor transmissions hydraulic?

Specifically, you've got a pump off the motor running a hydraulic motor (like a skagg or the like), with that motor tied to a transmission.

Seems to me like the best of both worlds, infinate adjustability in speed and ability to forward, reverse like a hydro. And talk about super easy maintenance. Either rebuild motor, which is really no different than rebuilding a hydro pump (super easy stuff), or rebuild a simple valve assembly.

I am no excavator expert, but isn't this how some of them work to drive the tracks?

Obviously would need an oil cooler, but that's no big deal.

Looking forward to engineers out there to tell me why this is a silly idea, which must be or they'd be out there.

Thanks,
Joel

 

[aczlan]

I've been wondering for some time, why aren't tractor transmissions hydraulic?
Specifically, you've got a pump off the motor running a hydraulic motor (like a skagg or the like), with that motor tied to a transmission.

Hydrostatic transmissions are just like that, some even have hydraulic PTOs. the problem is that for heavy ground engaging work they aren't quite as efficient as a gear transmission.


Aaron Z

(edit to add 2nd sentence)

 

[JoelD]

Thanks,
I saw a post one time on rebuilding a hydrostatic, looked a whole lot more complicated than a straight hydraulic motor tied to a tranny. I probably did not look close enough.

Joel

 

[IXLR8]

Joel, The Terrimite T-9 I rented was all hydraulic drive, 1 pump, 4 motors, one on each wheel. It had a 32 hp turbo Kubota engine in it... it didn't seem to have much power going up hills, it must have weighed a several tons. But on the level... it was like a small bulldozer.. nothing stopped it. BUT the whine of 1 pump and 4 motors drove me nuts, for that reason alone I would never own one.

 

[JoelD]

Hey IXLR8, thanks for the note. I can imagine it must take a whole lot of GPM to run something like that. But man, it's so simple. I've often thought that that set up would be about the simplest there could be.

Again, would take one big pump and a lot of HP spinning that pump.

I rented a T-5 once, I think it had hydrostatic, was super slow up hill, but must admit, it never stopped.

Have a great weekend.

Joel

 

[kennyd]

The Power Trac (PT for short) and the Steiner machines are all hydraulic...

 

[JoelD]

Thanks KennyD, did not realize the steiner was hydraulic, surprised at limited capacity of loader, steiner seems more like a machine you'd see at golf course, I've seen golf courses selling them used on occassion. The other machine looks very interesting, great capacities.

I just think the hydro-motor drive would be super simple and easy to fix if gone wrong.

Thanks again,
Joel

 

[Cyberroc]

Terrimite T-9 I rented was all hydraulic drive... the whine of 1 pump and 4 motors drove me nuts, for that reason alone I would never own one.

Same Here!

I have rented, I beleive the same one, a terrimite and it was really bad on hills as others have stated, the one I rented was 'used and abused' and it would stall on the hill on my property 1/2 the time...

The whine, oh the whine... just not sure I will ever get it out of my head.

I was actually getting ready to rent again, but decided to buy this time, but never, NEVER a Terrimite... At least not one with that driveline and that horrible whine...

 

[dfkrug]

I saw a post one time on rebuilding a hydrostatic, looked a whole lot more complicated than a straight hydraulic motor tied to a tranny. I probably did not look close enough.

They are fairly simple and robust, as long as you don't run out of fluid
or it gets dirty. The pumps and motors are just not like what you are
used to: they are axial piston motors/pumps, rather than gear motors/
pumps. I posted a bunch of pix in my B21 rebuild thread.

That said, try out a modern skid steer....all hydraulic and lots of whine.
Even a mid-size machine has a 50hp Diesel and tons of hyd flow. In modern
dozers, hyd drive is the bees knees.

It is interesting the tractors that use automotive-style hydraulic trannies,
like some old Fergies, which use torque converters, but do not have
auto-changing wet clutches.

 

[JoelD]

dfkrug, was your rebuild I referred to. Very impressive project. You left no stone unturned.

I tested out an old machine once with the torque converter. Seemed like another fairly simple set up and intuitively should be straight forward to fix.

Joel