Hydraulic pump/motor

[jwiereng]

Drove a drum roller today at work and looked under the hood. It is powered by a horizontal 8 hp honda. From the engine there is a pulley (no clutch) that runs a belt that goes to a pulley on a transmission case. The output of the transmission has a sprocket that goes to the the drive axle indirectly via a jackshaft. On the bottom of this trans there is a shaft connected to the lever. When the shaft is rotated the power is transmitted variably to the output shaft, reverse is accomplished by using the lever to rotate the shaft in the other direction. I have the link here to the manual

Please look at pages 46-48.

What type of transmission is this? I am pretty sure it is hydraulic since is has a large fill cap. The whole trans is very compact, and capable of some high torque output at low speeds. This got my mind spinning about the possibility of two of them being employed in an AATV. This would solve some of the problems others have stated about hydraulics eliminating weight and bulk of pumps, motors, hoses, and reservoir.

I am at a dead end in my research about this, b/c I don't know what it is called. I google hydrostatic variators and came always to things like this

Any ideas and help would be great.

[jwiereng]

After some more research I am come to realize it was probably something like an EATON 700 hydrostatic transmission commonly employed in law tractors.

Has anyone put a pair of these in an AATV? I like the idea, you have a heap of torque at low speeds, smooth accelerations, ability to counter rotate all in a fairly compact arrangement.

[thebuggyman1]

It has been discussed alot. The problem is you are limited to about 6-8mph without "gearing it up". If you do that you lose the power and stress the drive.
If you can live the slow speed it should work well, and a small hp motor would drive it. Research a drive from a woods mower or a grasshopper, they are pretty small and I've seen them on ebay.

[kunzmm137]

The problem is you are limited to about 6-8mph without "gearing it up".

buggyman is right about this, I have a tracked attex built with two cub cadet hydrostatics. I built it for snow and was not concerned about the speed of the machine. As far as the engine required, you have to remember that you are driving two of these transmissions, I originally had a smaller engine in the attex, I think it was 10 or 12 hp and it would bog down trying to go full speed. I now have a modified 16hp (probably 20 - 22hp) in it, and it does well for torque, but still only about 8 mph. Just some food for thought.

[jwiereng]

What would be the best way to gear it up? I envision still using the belt/clutch CVT to input to the hydrostats

[kunzmm137]

I don't think I would put a cvt on it. Hydrostatics want to keep turning when the engine is at idle so they keep pressure built up, and you do not want to turn them faster than 3600 rpm, they can't handle any more than that. You will want to have a lower final drive ratio after the output of the hydrostatics to get higher speed. You want to do all driving at full engine rpm, assuming that you have a governor on the engine. You will also have to ease forward on the controls, hydro's have the most torque when you just start to move the controls, if you push them all the way forward too quickly, you will stall the engine. Also, you might have to play with the gear ratio to get the most speed, if you get the controls all the way forward, but the engine is bogging down, you will have to use a higher drive ratio. Hydro's use up some hp, so there will be a point where you just can't go any faster without a bigger engine. Sorry for the long answer, just want you to be informed before you spend a bunch of money. Hydro's are very torquey and fun to drive, but they will never reach the speeds of a machine with a t-20 and a cvt clutch.

[jwiereng]

thanks for all the good advice.

What is the top speed of the Mudd ox? Is my understanding correct that it uses a hydrostatic just as you discribed?

[mudbug3]

kunzmm137

I own a Mudd-Ox and when I,m running at a slow or fast walking pace with no load, I use about a quarter throttle. If I,m in thick deep mud, I run about 3/4 to full throttle ,depending on what rpms I think I need to keep my engine from stalling.


jwiereng

The smaller sprockets on a Mudd-Ox will give you about 15 mph , and the larger sprockets I,ve read will give you about 20-21 mph.