Hydraulic Question. Using Two Motors

[Industrial Toys]

I am building my own immitation Flip Screen Bucket. You need to Google it to understand it. I did a test last night to determine RPM on the Char Lynn, Eaton Geroler motors I am going to use. I tried to get displacement data but haven't got that yet.

I don't have any large flow on my loader remotes for my Kubota R510 Loader, but I got:

122 RPM at 950 RPM Engine Idle
206 RPM at 1500
260 RPM at 1900

The question is. I am going to use two. One at each end of the bucket. What will this do to my speed? I am thinking that I will effectively double the displacement and hence my speed will decrease but someone has told me it will not decrease appreciably.

Anybody know? And how does load affect speed?

Thanks

 

[J_J]

Are they in series or parallel?

Two motors ii series, uses same GPM, and the pressure is developed across both.

Two motors in parallel, the flow divides and each motor will get 1/2 pump flow , and equal GPM if same cu in.

10 GPM and 10 cu in = 231 rpm

10 GPM and 20 cu in = 116 rpm

 

[Industrial Toys]

Thanks. You're the guy, I hoped would respond.

I was thinking of running them in parallel. They are both the same. So would they go half speed of only one?

 

[J_J]

Yes, that is correct.

 

[Industrial Toys]

Thank You

 

[Industrial Toys]

Can I put a small hydraulic cylinder across the motor circuit so it goes one way or the other depending on motor direction? And basically leave it under pressure at the ends of its travel? The motors should relieve some of the pressure, I would imagine but is this enough? I would like the cylinder to engage an arresting cam in one direction of travel only. And disengage in the other. The torque requirments to do this would be very modest and I would only require a tiny cylinder.

 

[J_J]

The hyd motor would have to be at stall to allow the hyd cyl to develop the max pressure.

The motor would take most of the flow as it would have the least resistance, and as you place a load on the motor, the cyl will develop pressure.

Why not use a splitter valveand give the motor say 5 GPM and feed the cyl whatever GPM.

 

[Industrial Toys]

Actually that is not a bad idea. Although the parts count and complexity is increasing. Is a splitter bidirectional? One way works the same as the other? And isn't the potential pressure that the cylinder might see still relatively high? My thinking was that if the rings and seals can hold constant pressure at end of stroke, the cylinder really should not rob any flow from the motors. Only while in motion. I am also just guessing that a very small cylinder could withstand constant pressure at end of stroke better then a larger one.

Thanks

 

[Jim Timber]

The problem is that your cylinder won't see anything unless the motor loads up to develop pressure between the two.

Poke a hole in the middle of a straw, then hold a balloon over that hole and blow through the straw - nothing happens to the balloon because there's no resistance in the straw. Now plug the end of the straw and your balloon inflates, but as soon as you release the end of the straw it deflates again from the tension in the rubber.

Same thing will happen with your cylinder in a hydraulic motor circuit. What JJ's saying is that until you load down your motor, no pressure will develop in the line and it'll never cause any work on the cylinder in either direction.

You really should just throw another valve in there or figure out how to run it with a diverter on a flow divider so you'll get some pressure to work with.

 

[bigdeano]

The motors will develop some back pressure even without a load, especially if they're new, because they're hard to turn when new. If you only require a small amount of force from the cylinder, what you propose should work.

A cylinder can hold it's max rated pressure indefinitely with no problem.