Hydraulic Drive system.

[socoj2]

Thanks JJ. I found the calcs on Surplus center and started doing some more math. Didnt realize how much HP it took to drive these things.

I Am going to look at the following pair i think it should be more in my range:

https://www.surpluscenter.com/item.asp?catname=hydraulic&item=9-7795-B

https://www.surpluscenter.com/item.asp?catname=hydraulic&item=9-7773

At least that brings the price down by a bit. and it makes it a lot easier to find the proportional Flow control valves as well.

 

[oldnslo]

Not that i want to disagree.

But if i am creating a side by side drive with out electronics.

Normally i would have 2 motors. 2 pumps. 2 Control valves and 2 resevoirs.

Now if i want to control it electronically. im just increases the valves to 2 Inline Solenoids and 2 Flow Control valves.? Is there something im missing?

I have never seen an aftermarket electrohydraulic motor, Ebay Surplus center etc. The problem with a new engine is i dont have $4000-$5000 to spend on one.

On a typical HST drive system that is mechanical you would only have 2 pumps, 2 motors and one reservoir. No valves are required if you are using a variable displacement True HST pump. Only one reservoir is required also.

If you are looking at a standard fixed displacement pump that has an inlet and outlet and planning on using proportion directional control valves for controlling speed and direction you making a system that will burn lots of horsepower and create lots of heat doing nothing.

Explanation to the best of my abilities.

Using a fixed displacement pump that provides 10 GPM @ 3,000 PSI which will give you travel speed of 10 MPH.
If you want to travel at 2 MPH you must divert 8 GPM of this oil to tank. If you are using proportional control this is usually done with a valve called a hydrostat block which senses pressure in the work ports and meters flow across your proportional. Now if you are climbing a hill that requires a system pressure of 2,000 PSI the extra 8 GPM is being dumped to tank also at 2,000 PSI which equals about 9 HP wasted power in heat.


Same system using tue variable volume HST style pumps will probably have around 1.5 - 2 HP loss. This is from the charge pump and inefficiency of the system.

Does any of this make sense?

Roy

 

[VroomVroom]

Hope you continue the project.

 

[AKKAMAAN]

On a typical HST drive system that is mechanical you would only have 2 pumps, 2 motors and one reservoir. No valves are required if you are using a variable displacement True HST pump. Only one reservoir is required also.

If you are looking at a standard fixed displacement pump that has an inlet and outlet and planning on using proportion directional control valves for controlling speed and direction you making a system that will burn lots of horsepower and create lots of heat doing nothing.

Explanation to the best of my abilities.

Using a fixed displacement pump that provides 10 GPM @ 3,000 PSI which will give you travel speed of 10 MPH.
If you want to travel at 2 MPH you must divert 8 GPM of this oil to tank. If you are using proportional control this is usually done with a valve called a hydrostat block which senses pressure in the work ports and meters flow across your proportional. Now if you are climbing a hill that requires a system pressure of 2,000 PSI the extra 8 GPM is being dumped to tank also at 2,000 PSI which equals about 9 HP wasted power in heat.


Same system using tue variable volume HST style pumps will probably have around 1.5 - 2 HP loss. This is from the charge pump and inefficiency of the system.

Does any of this make sense?

Roy

AGREE 100% with you Roy!!
Why not use proper pumps when they are available!
The simplest systems work on a 1500$ ride on mower!!

 

[VroomVroom]

just wondering how the project is coming. Im interested. There is another posting here by a david duvono on a tracked dumper. He is doing a similar project.

 

[David Devuono]

Lots of good but (confusing to me), information here. Some of the information above, regarding 10gpm pump having to divert 8 gpm if you want to go 2 mph. I would think that in an ATV like vehicle, you would want to throttle down the engine driving the pump to control speed. On a mower you want full speed to spin the blades and so I can see where you would need a different set up to control the speed. On an ATV or in my case a tracked dumper, the only work is moving the thing, it takes little GPM to dump, so I would expect good performance dumping at idle with the kind of pumps we are going to run. In SOCOJ2's example he went from 450 ft lb motors to 85 ft lb motors. I don't believe he would get much ground speed. I would be pleased if my unit would match the 7.5 MPH top speed of my Kubota B4200.

 

[David Devuono]

In other words and correct me if I am wrong, If my ATV can go 10MPH at 3300 RPM driving the pump, could I not go 3.3 MPH at 1100 RPM if the rolling resistance does not change? My pump produces 2500 PSI at 1000 RPM (planning 2:1 reduction) so 1100 engine RPM will turn my pump at 550 RPM. Max speed I will run my pump is about 1850 RPM (max speed rating 3000RPM). I have less then $150 into pump and motor so if it does not work I will go to plan B. thanks

 

[AKKAMAAN]

Diverting or throttling flow for low speed usually means that you use more energy(100% heat) for the by passed oil than the oil used to travel forward...
It can be OK if you can deal with the excessive heat in the system, increased fuel cost and limited control of speed and torque.....

 

[oldnslo]

In other words and correct me if I am wrong, If my ATV can go 10MPH at 3300 RPM driving the pump, could I not go 3.3 MPH at 1100 RPM if the rolling resistance does not change? My pump produces 2500 PSI at 1000 RPM (planning 2:1 reduction) so 1100 engine RPM will turn my pump at 550 RPM. Max speed I will run my pump is about 1850 RPM (max speed rating 3000RPM). I have less then $150 into pump and motor so if it does not work I will go to plan B. thanks

Your theory is correct for the most part. One concern might be will you gas engine have enough power idled down to do the work? Your pump will still generate the same PSI regardless of RPM input.

I guess you won't know unless you try.

Best of luck

Roy

 

[David Devuono]

I bought a 723 CC 27 HP twin cylinder Briggs and Stratton. Its a verticle shaft engine so I am hoping that the pump will have no issues operating on its nose? I am told that to operate my pump I would need Min 15 HP. Thats the good thing about building things yourself, if something does not work, cut it out and put something else in.