Hydraulic Motor Help

[kruszert]

I am new to hydraulic motors and know little about them other than what I have picked up from reading past posts on this forum so please excuse some dumb questions.

To give some background - - I have a 6" Jinma chipper. The chipper works well for my needs but the feed system does not. I made a new feed drum that actually grabs the branches, then snapped in the shaft in the drum (cold rolled steel), replaced the shaft (better steel), then snapped the drive shaft to the drum, replaced with the newer design from Jinma (works well), now bent the output shaft from the right angle gearbox! I would have thought the A section v-belt would have been the weak link in this system but the belt has held up perfectly without slipping. I looked at heavier duty gearboxes but they get too big and would require a bunch of modifications.

Fancy chippers (read that as expensive chippers that I can't afford) use hydraulic feed systems so - - I would like to replace the feed drive with a hydraulic motor run off the hydraulic system on my tractor. I have no idea if this is practical but am just investigating.

The tractor is a Kioti DK-35. Hydraulic output is 12.5 gpm, 2300 psi I assume at 2400 engine rpm. I usually run at a little slower RPM say around 2000.

I need very low rpm for the feed drum. The gear reduction takes it down to 28 rpm at 2400 engine rpm.
If possible I would like to be able to vary the speed with a max of 28 rpm down to maybe 12 rpm for when I feed in larger branches like 6".

I have looked at hydraulic motors on different websites (Suplus Center, Baileys, etc). Seems like they have more than enough torque, require pump volume well within my tractor's capability, are small and easily adaptable to what I need but have way too much output speed with 12.5 gpm flow.

Are there control valve/bypass valves that would allow me to set a flow/motor speed? Will this mess up my pressure to the motor? Any suggestions would be appreciated.

Thanks,
Reggie

 

[allenr]

I've used these to good effect, infinitely variable with no drop in pressure to the motor. 3 ports - pressure in, out and bypass.

Fitted one on the delivery conveyor of a grape harvester to slow that belt alone and another on a fertilizer spreader to slow the delivery chain speed - very effective in both applications.

Surplus Center - 1/2 NPT HYD FLOW CONTROL VALVE W/RELIEF RDRS150-16

 

[J_J]

I agree, as that is similar to the valve that my PT-1445 uses for the PTO output which is variable from 0- to max, using 13 GPM.

As far as hyd motors, the larger the cu in motors you use with same GPM , the rpm will decrease.

If you have 13 GPM and a 5 cu in motor, the rpm will be 601. Torque at 3000 psi will be about 2389 in lbs.

A 10 cu in motor using 13 GPM = 300 rpm Torque = 4777 in lbs

a 20 cu in --------------13 GPM = 150 rpm Torque = 9554 in lbs

You will have almost constant torque throughout the speed range.

If you gear down the rpm from the hyd motor, you can get even more torque.

Your tractors rated pump GPM is at max speed.

You can reduce your engine rpm down to produce less GPM, and therefore less speed for the hyd motors.

I used 3000 psi for the torque, so your torque will be less but still good.

 

[kruszert]

allen and JJ - - thanks for the quick replies.

I looked at the flow control valve and it looks like it will do just what I wanted. I did the calculations on GPM flow vs. pump speed and pretty much understand that. I can't reduce the tractor speed too much for this application since the chipper flywheel is coupled to the PTO and I need to keep that speed up.

Just a couple more questions (at least for now).

first: The hydraulic motor and the valve need to have return lines to the tractor reservoir. Can I
tie them in together and go to the tractor hydraulic fitting or will this cause a problem?

second: The valve has a relief valve setting. Looks like my choices are 800, 1600, 3000psi. My tractor
hydraulic system is 2300psi - - does this mean I have to use the 3000psi valve or is the
pressure rating for what the motor sees. Meaning that if the motor stalls and the pressure
on the valve discharge to motor exceeds the setting it will relieve to the tank? If the latter is
the case then 1600 would protect the pump and based on torque rating still likely produce way
more torque then I had using the gearbox. Based on size and weight of the chipper gearbox as
compared to gearboxes at Suplus Supply it doesn't produce much torque - - although it is
enough to twist a small shaft or two (or three). I would like to end up with the valve relieving
BEFORE I break anything else.


Again, thanks for your help,
Reggie

 

[J_J]

Here is a Prince PDF that might explain some things.

You might have to get a different valve to get adjustable relief.

By the way, you can always add an external relief valve to any hyd circuit.

Just run the relief port to tank




http://www.surpluscenter.com/item.asp?item=9-4127&catname=hydraulic

http://www.surpluscenter.com/sort.asp?catname=hydraulic&keyword=HAR1

 

[oldnslo]

A word of caution, make that the motor you are using will operate at 12 -28 RPM. Some LSHT motors will not run that slow.

 

[allenr]

I reckon you could use the 3000psi relief setting, it'll just mean the tractor's inbuilt relief will blow off at 2300.

I think it should be ok to plumb the bypass in to the motor return - the bypass will have to go through the breakaway and the tractor valve but they shouldn't cause much back pressure.

 

[J_J]

If the tractor relief valve is 2300 psi, the chipper motor valve will never go off, as the chipper valve, relief at 3000 psi, is before the tractor relief which is 2300 psi and on the 3pt valve.

You can always add an external relief valve before the first valve, and just after the pump output, which will protect the tractor pump.

Surplus Center - 1/2" NPT 30 GPM 1500-3000 PSI RELIEF VALVE RV-H4

To protect the hyd chipper motor, add this valve across the chipper motor.

Surplus Center - 1/2 NPT 30 GPM 1500-3000 PSI HYD CUSHION VALVE

Since your hyd system pressure is 2300 psi, set all other relief valve to 2300 psi.

Are you going to send the EF, excess flow to tank or to the hyd flow path?

Excess flow is any fluid not used by the hyd motor.

 

[dfkrug]

The tractor is a Kioti DK-35. Hydraulic output is 12.5 gpm, 2300 psi I assume at
2400 engine rpm. I usually run at a little slower RPM say around 2000.

A couple of points on using a hyd motor to drive your feed system:

The DK35SE and the older DK35 tractors put out about 7-9 GPM from the implement pump. You
have to have the service manual to get he spec. 12.5GPM includes the power steering pump and is
not useful here.

Turning 30-odd RPM direct-drive will require a large displacement motor, as mentioned. The price
goes up a lot when you get north of 5 or 6 cubic inches, and you may need as much a 20 or more
ci for that low speed. That's huge and spendy.

So you can use a diverter to slow down a smaller motor (as mentioned), or you can use a chain or
belt-drive system to do the same. Each costs more.

Note that common cheap hyd motors, like those from Charlynn-Eaton, or White are limited
to 2000 psi. That means you need to protect it from your 2300psi, or buy a more expensive
motor. What I would do is add a conventional AUX hyd spool to your Kioti. This valve will
be quite useful for other things (hyd toplink, etc), and have its own RV. Set the RV to 2000psi,
and you will protect your motor. Gear a cheaper motor down with a belt or chain to get
the speed you want.

Finally, you will need to think about how you want to control the drive. Modern chippers with
hyd feed use a safety bar that shuts off the hyd valve quickly if you are being dragged into
the maw of the chipper. That is why you do not want to power the feed motor with a motor-
type valve.

A Vermeer 525 chipper I use operates this way (Charlynn S motor) off of a 25hp engine.

 

[J_J]

kruszert ,

Have you considered one of the wheel motors like this?

Surplus Center - 10.3 CU IN ROSS HYD WHEEL MOTOR MB100208AAAF

Use the above valve to adjust the speed you want. The hyd motor will develop the pressure to get the job done. Install that double relief valve across the motor and you are set to chip.

 

[kruszert]

Again thanks for the replies,

I am still working on a design for the feed system and it gets more complicated as I go - - - and more expensive. I found a large displacement pump 23.6 cu. in. in surplus center (~$160 anything bigger the price goes way up fast) but it is still too fast at 12.5 gpm. About 122 rpm. Then I need to put in a belt or chain to reduce even further. From what I have read it would be best if the pump ran in its upper rpm range rather than trying to slow way down with the flow control valve. Also I don't want to be able to accidently over speed the feed drum.

dfkrug -- I got the 12.5 gpm off the internet. My tractor is a DK35 all gears - - about 6 years old. I will check the specs. If it is less that would be very helpful. I have added a second aux spool already (tractor had one). I use one for adjustable top link and one for adj side link. My plan is to remove the side link when using the chipper and use those fittings. Since when I use the chipper the tractor is stationary I assumed the full flow would go to the aux spool - - maybe not? Also, I didn't know I could adjust the relief on the aux spool but installing a seperate relief valve isn't that difficult.
I do need to consider a safety system to turn it off.

Design is still in progress.

Reggie

 

[J_J]

kruszert ,

You do know that cu in and pressure determines the torque, so the torque is about constant throughout the rpm range. The load on the hyd motor causes the pressure to develop.

GPM's determine the speed of the motor.

So, determine the torque you need and use a large wheel motor with variable flow valve and control the motor speed with full torque.

If you want even more torque, just use belt and pulley or sprocket and chain at 1:2 or 1:3 reduction and gain more torque, and reduced rpm.

 

[dfkrug]

I found a large displacement pump 23.6 cu. in. in surplus center (~$160
anything bigger the price goes way up fast) but it is still too fast at 12.5 gpm. About 122 rpm. Then I
need to put in a belt or chain to reduce even further. From what I have read it would be best if the pump
ran in its upper rpm range rather than trying to slow way down with the flow control valve. Also I don't
want to be able to accidently over speed the feed drum.

That motor at SurpCntr runs at 1450psi, continuous. Once you pick a motor, go to the manufacturer's spec
sheet in their online catalog and look up the characteristics. You want to pick an operating point somewhere
in the midrange of pressure/RPM; they get very inefficient at the extremes.

If you have an aftermarket AUX valve already, then you are set with a relief, as long as it is adjustable. Full
flow is fine if you are going to pick a motor and gear it down to fit your flow. If you don't want to adjust the
AUX valve RV, and don't use a motor rated at least at 2300psi, then a simple crossover RV like this I recently
used for my hydraulic chainsaw works well, and is not too spendy. Factory AUX valves often do not have their
own RVs because they count on the system RV. My Kioti OEM AUX valve is like that, which required I add an
RV. Also, some hyd motors have an optional RV built in.

I try to simplify the design as much as I can.

 

[J_J]

Do you have 15.8 GPM for the motor you found at Surplus. You said you only have 12.5 GPM, so right away, the motor will run less speed at 123 rpm, and the hyd motor pressure limit is only 1450 psi. Torque, using your 2300 psi would be about 8643 in lbs.

The limb/wood inches per delivery speed is determined by the roller pulling the limb into the chipper.

Otherwise, how fast the wood is moving into the chipper.

You regulate that by the lever on the variable flow valve.

If the hyd motor will run at say 30 rpm, why would you need any more reduction. You might gain more torque.

The wheel motors on my machine can probably run at 1 rpm. We use the hyd pump speed control lever to control the speed of the wheels in our closed loop hyd system.

 

[kruszert]

The 23.6 cu. in. motor runs at 150 rpm at the 15.8 gpm so I figured with my system at 12.5 gpm it would slow down to ~123. I still need to find the factory specs to see if I am running less gpm. As for torque I think I am way over what the right angle gear drive provides so I am not worried about that even if I put in a RV at around 1400 psi. I may actually have to reduce the RV pressure if I go back to twisting the shaft off my feed drum (again).

I do need to look into wheel motors - - I never looked at them.

As for more reduction - - when I try to grind up branches 5" to 6" in dia the tractor has trouble handling them. Usually I cut up this large stuff for firewood but on pine I prefer to just grind it. I was thinking if I could vary the speed down it would go in easier.

Thanks for the suggestions. Still working this out. It is looking like a winter project rather than a quick fix.

Reggie

 

[hydraulicmotor]

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