School me on hydraulic motors

crmorse

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Equipment
'20 RTV-XG850, '16 L47 TLB, '06 JCB 506CHL, '99 JD 455G, 1953 Ford 8N
Nov 28, 2016
102
0
16
Anniston, AL
I am trying to build a hydraulic capstan winch like the Norwood Skid Winch (they won't sell theirs unless you buy a mill too). http://www.norwoodsawmills.com/products-log-skidding/skid-winch

I've found hydraulic drive gear motors that should be perfect for the application... it's designed for high axial load and has gobs of torque.
http://www.surpluscenter.com/Hydrau...-DYNAMIC-BMSY250E2KS-HYD-MOTOR-9-7080-250.axd

But I have a question about proper system design. I get that the rear remote valve is going to control the hydraulic flow rate and direction but if I understand it correctly. The full PSI of the system will be present almost immediately, right? So I need to either get a motor that's rated for the full pressure or lower the pressure somehow.

Can I just plumb in an adjustable pressure relief like this?
http://www.northerntool.com/shop/tools/product_200335623_200335623

I suspect the answer is no. I'm thinking once pressure goes over the set-point that valve will open and dump all of the pressure until it drops down again. I thinking that instead of balancing the system it'll end up "hammering" open/closed again until something breaks. Right?

So... a few questions:
1) if I'm right about the above how can I lower the pressure to the pump?

2) Does anybody know the actual system pressure of an L47? I can't find it anywhere

3) how do I calculate the total pulling force available given the pump's in-lbs of torque and a 2.5" diameter capstan?
 

North Idaho Wolfman

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L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
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#1 Hydraulic flow (GPM) is more important with a motor than pressure (PSI).

Your tractor (It is somewhere in the range of 11.8GPM), it does not have the GPM to handle that big of a motor (around 19 GPM).


In fact you only have enough GPM to handle the smallest of hydralic motors, but the good news is even with the smallest motor, if you run a gear driven drum you can pull a whole lot of weight.

When sizing the motor, you need to look at GPM to RPM ratio.
what you really need is a gear reduction motor as the torque will be through the roof.

You also want a motor with a brake or the dynamic force will be too great to start it under load. ;)

You don't need to do anything with the PSI values as the tractor will take care of that with it's own system.
Just as a note: the pressure relief valve you show would not work with that motor as it only has the capacity of 16 GPM.
 

crmorse

Member

Equipment
'20 RTV-XG850, '16 L47 TLB, '06 JCB 506CHL, '99 JD 455G, 1953 Ford 8N
Nov 28, 2016
102
0
16
Anniston, AL
North Idaho Wolfman, thank you for that info. If I may, I have a few follow up questions...

I have looked at the RPM tables and for the motor I picked out it shows about 5GPM required to get to 60 RPMs which is my desired speed. So if I'm only ever desiring 60 RPM can I use that motor?

Also, with the capstan style winch there really is no startup load. The actual load on the motor is controlled by how tight you pull the rope. (you have to see the video for it to make sense) https://www.youtube.com/watch?v=b1BETKXmfBM

So if I follow you so far, what I'm thinking now is there'll be no startup load but lets say I try to pull too large of a log and stall the motor. That will cause the PSI to shoot up to the full ability of the tractor (~2500 PSI think) and blow the motor seals. Right?
 

Ike

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Kubota L 3301, Farmall Cub. JD B. Ferguson TE 20
Jul 18, 2015
324
1
0
Mich
North Idaho Wolfman, thank you for that info. If I may, I have a few follow up questions...

I have looked at the RPM tables and for the motor I picked out it shows about 5GPM required to get to 60 RPMs which is my desired speed. So if I'm only ever desiring 60 RPM can I use that motor?

Also, with the capstan style winch there really is no startup load. The actual load on the motor is controlled by how tight you pull the rope. (you have to see the video for it to make sense) https://www.youtube.com/watch?v=b1BETKXmfBM

So if I follow you so far, what I'm thinking now is there'll be no startup load but lets say I try to pull too large of a log and stall the motor. That will cause the PSI to shoot up to the full ability of the tractor (~2500 PSI think) and blow the motor seals. Right?
Go to the surplus center web sight and search for item #9-064-38. I am running my wood conveyor using this valve and you can control the speed from 0 to max by moving the lever on this flow control valve. I have a 500 rpm motor that I am using it on
 

North Idaho Wolfman

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L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
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If you use the valve that Ike put up it will work, and it has the proper relief valve already built into it.
I would still drop down in motor size because you will increase the torque with a smaller motor.
 

Yooper

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May 31, 2015
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You may need to reduce the speed, depending on the diameter of the capstan. In the video, I'm guessing its turning 60-80 rpm. Gear reducer, chain and sprocket, either would work and increase the torque. Surface speed on the capstan where your rope will be pulling from is the key number you'll need. Smaller diameter = higher rpm. Larger diameter = lower rpm. Figure what feet per second you need, and calculate from there.

As far as the system pressure goes, it will be like my hydraulically driven stump grinder. Free wheeling with no resistance, the gauge reads 50 psi. Its not until the wheel meets resistance from the stump that the pressure will rise.
 

crmorse

Member

Equipment
'20 RTV-XG850, '16 L47 TLB, '06 JCB 506CHL, '99 JD 455G, 1953 Ford 8N
Nov 28, 2016
102
0
16
Anniston, AL
Good guess! From my research it sounds like 100fpm of rope pull is the goal and I have a 2.5" diameter capstan which works out to 60rpm.
 

crmorse

Member

Equipment
'20 RTV-XG850, '16 L47 TLB, '06 JCB 506CHL, '99 JD 455G, 1953 Ford 8N
Nov 28, 2016
102
0
16
Anniston, AL
So I've been doing a lot of researching and learning and I've gathered a few things.

First, when spec'ing a hydraulic motor max pressure is very important. The tractor's relief valve protects the tractor's system; not your pump. If your pump can't handle full pressure it will leak or break.

Second, my tractor appears to be an open-center system which means full flow needs to be maintained at all times. So if I'm not using the full flow I need to give the extra a path back to the system. The usual spool valves do this as part of their normal function.

Now, in my case that still leaves me with a solve-for. I plan to hook into my backhoe's swing pump port. That gives me 6.6gpm of flow and it is individually switchable from the main backhoe port. (I can leave the main off and only turn on the swing pump outflow). My selected motor can handle full pressure so I'm good there but for my desired ~60rpm I only need about 5gpm. The full 6.6gpm would spin up to nearly 120rpm.

So my plan is to use the flow control valve that Ike pointed out. http://www.surpluscenter.com/Hydrau...ONTROL-VALVE-W-RELIEF-RDRS150-16-9-064-50.axd

However, I'm not sure how to plumb it in. That valve has a return for the overpressure, which is good, but I can't just "tee" it into the motor's return line or that flow would go into the motor stalling it or reversing the direction. I don't think an inline check-valve will work either but I might be wrong.

So my question is this? Where do I go with the motor return and the flow control valve's overflow return? I only have 1 return on my tractor.
 

crmorse

Member

Equipment
'20 RTV-XG850, '16 L47 TLB, '06 JCB 506CHL, '99 JD 455G, 1953 Ford 8N
Nov 28, 2016
102
0
16
Anniston, AL
S That valve has a return for the overpressure, which is good, but I can't just "tee" it into the motor's return line or that flow would go into the motor stalling it or reversing the direction. I don't think an inline check-valve will work either but I might be wrong.
Ok, I think I've found my problem. The above is incorrect. My flow control valve isn't going to allow reverse flow and since the return is an open drain it's pressure will be close to zero. So both the flow control valve drain and motor drain can both dump in at the same time.

Can anyone confirm this for me please?
 

North Idaho Wolfman

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Staff member
Lifetime Member

Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
28,286
4,853
113
Sandpoint, ID
Ok, I think I've found my problem. The above is incorrect. My flow control valve isn't going to allow reverse flow and since the return is an open drain it's pressure will be close to zero. So both the flow control valve drain and motor drain can both dump in at the same time.

Can anyone confirm this for me please?
Yep you got it! ;)
 

Ike

New member

Equipment
Kubota L 3301, Farmall Cub. JD B. Ferguson TE 20
Jul 18, 2015
324
1
0
Mich
So I've been doing a lot of researching and learning and I've gathered a few things.

First, when spec'ing a hydraulic motor max pressure is very important. The tractor's relief valve protects the tractor's system; not your pump. If your pump can't handle full pressure it will leak or break.

Second, my tractor appears to be an open-center system which means full flow needs to be maintained at all times. So if I'm not using the full flow I need to give the extra a path back to the system. The usual spool valves do this as part of their normal function.

Now, in my case that still leaves me with a solve-for. I plan to hook into my backhoe's swing pump port. That gives me 6.6gpm of flow and it is individually switchable from the main backhoe port. (I can leave the main off and only turn on the swing pump outflow). My selected motor can handle full pressure so I'm good there but for my desired ~60rpm I only need about 5gpm. The full 6.6gpm would spin up to nearly 120rpm.

So my plan is to use the flow control valve that Ike pointed out. http://www.surpluscenter.com/Hydrau...ONTROL-VALVE-W-RELIEF-RDRS150-16-9-064-50.axd

However, I'm not sure how to plumb it in. That valve has a return for the overpressure, which is good, but I can't just "tee" it into the motor's return line or that flow would go into the motor stalling it or reversing the direction. I don't think an inline check-valve will work either but I might be wrong.

So my question is this? Where do I go with the motor return and the flow control valve's overflow return? I only have 1 return on my tractor.
I use the flow control valve to control the elevator on my wood processor. I have 6 double acting valves in a row and I teed the inlet line off before the valves and put the flow valve in. As you face the flow valve the inlet line goes on the left side of it and the out let to your winch goes on the top right. The third line is just plumbed back into the return line where it comes out of the control valve. Hooked up this way I am using the flow control valve to control the speed on the elevator which is run by a 500 RPM hyd motor. I have my power out line run thru a reg control valve so that I can reverse the elevator if needed. Hope this helps