Hydraulic motor sizing - weird project

[MossRoad]

So how is it going to roll? Two axles, one front and one rear, or 4 independent axles, one at each corner?

I see you have two hydraulic motors.

If you go with two axles, one front and one rear, you could put one hydraulic motor on each axle to turn the differentials. Steer with the front or rear as you desire. Then you'd only need one valve to control forward, reverse on the variable volume pump, and one valve to operate a steering ram on the steering axle.

 

[MossRoad]

Hook the two hydraulic motors powering the two axle differentials in series. If one motor starts to slip due to the tires spinning, the other motor will stop it.

 

[oldnslo]

Cmaas
For Sun pilot ratio typically is 8:1 or 10:1 range for motor applications. The old printed books from the 90's had some helpful information in them in a section called technical tips. I suspect Sun put this information on-line for assistance in selecting the correct valve but I am familiar with their website.

The counterbalance valves will apply back pressure to the motors to slow or prevent running away down a slope so you may need case drain lines on the motors. If this is not possible you will have to look at some other form of braking or unwanted motion control.

A gear pump produces flow whenever it is turning and all of this flow is produced at the highest system demand pressure so you in theory can climb the hill using similar power at full speed Vs half speed and be more efficient at full speed since all the pressure is doing work across the motor Vs being bled off across some metering device or relief valve.

You can purchase directional valves with good metering over that flow range but they will not be inexpensive. Proportional Danfoss PVG is a very common valve in various sizes. If you get meter in and meter out style you might want to consider a 4 -ported counterbalance with spring chamber vented directly to tank. This eliminates the potential for valve back pressure causing the counterbalance to go unstable.

I know throwing lots of stuff at you but hopefully some of it is helpful and prevents an oh shucks moment.

 

[cmaas]

So how is it going to roll? Two axles, one front and one rear, or 4 independent axles, one at each corner?

I see you have two hydraulic motors.

If you go with two axles, one front and one rear, you could put one hydraulic motor on each axle to turn the differentials. Steer with the front or rear as you desire. Then you'd only need one valve to control forward, reverse on the variable volume pump, and one valve to operate a steering ram on the steering axle.

Have a look at the photo on page on page 4. Each wheel leg is independent and can pivot up out of the water.

 

[cmaas]

I know throwing lots of stuff at you but hopefully some of it is helpful and prevents an oh shucks moment.

Thanks, that's all helpful information. I am looking at Sun's Dual Counterbalance Assembly with Crossport Relief and Shuttle, 10:1 Pilot Ratio. It seems to be rated at 15gpm which is a little less than I can get from my pump's 35gpm intermittent capacity (after being split by the 50/50 flow divider). Not sure if that's a problem.

I've just had a look at Sun's video about choosing a counterbalance valve. Woah! That was mind bogglingly confusing! I knew I was getting in over my head with this hydraulic stuff but I had no idea just how complex the subject is.

 

[cmaas]

Cmaas
For Sun pilot ratio typically is 8:1 or 10:1 range for motor applications. The old printed books from the 90's had some helpful information in them in a section called technical tips. I suspect Sun put this information on-line for assistance in selecting the correct valve but I am familiar with their website.

I just received my Rexroth counterbalance valves from the Italian distributor. Those guys were great. Good price and got them here in about 2 weeks.
Can you tell me if they can be mounted 2' away from the motors? With hose rather than steel tubing?

 

[oldnslo]

You can mount them with hose but only concern is hose breaks you have lost your braking capability on that motor. Same if steel line breaks.

 

[cmaas]

Here's a dumb question - do C1 and C2 go from the counterbalance valve to the motor or do V1 and V2?

 

[oldnslo]

C1 and C2 go to motor
V1 and V2 go to valve

since counterbalance is more commonly used on cylinders C = cylinder and V = Valve

 

[cmaas]

Thanks.
I'm not sure what's happened to my thread here. I can't see some of the more recent posts.