I am in the process of bulding a 4wd hydrostatic drive articulating tractor. I am wanting to drive implements such as a mower deck, sickle bar mower, and a tiller via hydraulic drive. The hydrostatic drive is done via a driveshaft to two cub cadet hydrostatic transmissions. My hydraulic orbital steering valve does not have power beyond. So in order to steer this thing while running attachments am I correct in understanding that I will need a second smaller pump just for steering or is there another way to plumb this in so that I can steer this thing while using the implements? I don't have specs on most of these things yet, as I am still in the planning stages for those, but the implements will all require a lot of flow.
Hydraulics on custom tractor
- Thread starter dodge85rc
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J_J
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aczlan
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There are two ways to do what you what to do, one is to use separate pumps (IE: a auto PS pump for steering and a large pump for implements), the other way is to use a flow divider
Aaron Z
Aaron Z
kennyd
Advertiser
A true hydrostatic machine has a minimum of two pumps counting the hydrostat transmission. Most medium sized machines and larger will have at least three, with one pump dedicated to the steering.
To ensure you can steer, you need a priority valve the dedicates a certain amount of flow to the steering no matter what else is happening.
How may HP are you working with?
In that case I already have 3 pumps running. 
The two axles are hydrostatic transmissions out of old cub cadet mowers that are run off of a comon driveshaft. So there is 2 pumps there, one for each tranny and the 3rd is for hydraulics at the moment. This project is one that is being done for as little as possible so I am going to try to track down a priority valve. Or mount a second smaller pump (which I have) just for the steering. The only thing that concerns me, is in regards to your quesion is I only have 20 hp to work with on the engine. I already have a driveshaft from the engine to first tranny, an alternator and 1 big hydaulic pump. Now if I add a second pump, I'm afraid that may be too much for this engine.
The two axles are hydrostatic transmissions out of old cub cadet mowers that are run off of a comon driveshaft. So there is 2 pumps there, one for each tranny and the 3rd is for hydraulics at the moment. This project is one that is being done for as little as possible so I am going to try to track down a priority valve. Or mount a second smaller pump (which I have) just for the steering. The only thing that concerns me, is in regards to your quesion is I only have 20 hp to work with on the engine. I already have a driveshaft from the engine to first tranny, an alternator and 1 big hydaulic pump. Now if I add a second pump, I'm afraid that may be too much for this engine.
kennyd
Advertiser
Dodge,
Please take this with all due respect, but there is no way you will power 2 hydrostatic units, steering and then a mower or tiller hydraulically with 20 HP.
Please take this with all due respect, but there is no way you will power 2 hydrostatic units, steering and then a mower or tiller hydraulically with 20 HP.
J_J
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What are the displacement on your three pumps? 20 HP will only support 10 GPM, with a total displacement of 6.4 cu in, on all your pumps. You may be able to drive it, but you will not cut much grass or till.
No offense taken. 20 hp is not much to work with, however it is all that I have to work with for this tractor I am building. This project is being done for as cheaply as possible and I got a heck of a deal on a new 20 hp engine so that is what I went with. Having enough power to run the mower deck is the only thing that I am concerned about, as it is a fairly large deck. In which case I'll find another engine plop that down on the mower deck itself and forget about hydraulics for it. More of a pain, but no big deal really. The tiller is run via a small motor going into a gearbox, which actually goes into another gearbox on the tiller, so that will be no problem as it is only a 40 inch tiller that, again, came off of a cub cadet. For this tiller model some of the mowers only had 7 hp engines in them. I am also playing the pulley size game for the accessories that are being run to maximize the torque aspect of it, where I can anyways. thanks
I don't have specs on my pump. The hydrostatic drive pumps are complete transaxles off of old cub cadets, a 129 and a 127 I believe. Pump, controls, gears, axles ect...The whole shebang. Still trying to decifer and find the specs on my main pump.
