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Author Topic: Running hyd motor in fwd and rev.  (Read 1548 times)

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Online Hilltop366

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Re: Running hyd motor in fwd and rev.
« Reply #20 on: June 02, 2021, 08:10:14 PM »
I have read before (don't remember where) that any hyd motor that turns anything with inertia should use a open centre valve, a motor valve should be easier to adjust feed rate. Could add a park break somewhere in the shaft or drum if worried about the carriage creeping. 

Offline Jim1934

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Re: Running hyd motor in fwd and rev.
« Reply #21 on: June 02, 2021, 08:15:14 PM »
I wish I knew more about this subject. The hyd. motors I run are on conveyers and they reverse through motor spool valves. A sawmill carriage takes a serious jolt every time you gig back. You also use the feed for a brake constantly. The old belt or friction feeds are slipping all the time. On a commercial sawmill the hyd. feeds start out at 50 h.p. So a small hyd. feed must be heavy enough and be cushioned somehow or it will surely break.
Good point. I will have a gear reduction of 32:1 between hyd. motor shaft and the cable drum shaft. Existing gears are heavy duty.
Four are 3 diametrical pitch and 3 inches wide. Diameters are 18,4 1/2, 16,4. I will add another reduction of 2 with chain and sprockets at the motor end. This reduction results in the motor seeing one tenth of one percent of the carriage inertia.
I'm guessing the motor will not be damaged. Thanks for the post. Jim



Offline mike_belben

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Re: Running hyd motor in fwd and rev.
« Reply #22 on: June 02, 2021, 10:18:40 PM »
You a machinist jim?
Psalm 37:16

Offline Southside

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Re: Running hyd motor in fwd and rev.
« Reply #23 on: June 02, 2021, 11:04:19 PM »
I don't know if it's because your young or because your form Mass.   On a sawmill carriage going into the log is called crowding and backing up is called gigging or gigging back.  At some point in history sawyers allowed frog spearman to use their term :D.
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Offline mike_belben

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Re: Running hyd motor in fwd and rev.
« Reply #24 on: June 03, 2021, 12:41:33 AM »
I know what that one means.  But my kids still dont obey.

;D
Psalm 37:16

Offline Jim1934

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Re: Running hyd motor in fwd and rev.
« Reply #25 on: June 03, 2021, 09:33:47 AM »
You a machinist jim?
Ha, yes, old school, self taught, just so I can repair my toys
like the Knight mill. Made a living as an engineer, many years ago.
Wonder why you asked. Probably the "diametrical pitch" did it. :D

Offline mike_belben

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Re: Running hyd motor in fwd and rev.
« Reply #26 on: June 03, 2021, 10:15:26 AM »
yeah.. normal people dont mention DP

;D
Psalm 37:16

Offline Machinebuilder

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Re: Running hyd motor in fwd and rev.
« Reply #27 on: June 03, 2021, 11:21:13 AM »
My Hydraulics salesman/expert stopped by this morning.

the correct valve will be a A/B to tank center. This is what is refered to as a motor control valve.
A blocked port center will cause large pressure spikes from inertia.

He started to explain the reverse rotation option and it has to do with changing the flow paths inside the motor,for easier plumbing.

You will need a bidirectional motor.
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Offline Jim1934

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Re: Running hyd motor in fwd and rev.
« Reply #28 on: June 03, 2021, 11:51:57 AM »
I think that motor is not bidirectional. When ordering there is a special order option for reverse direction.

to be sure call the tech support line and ask before purchasing one.

There are many other hydraulic motors that are bidirectional.

For the valve I think you want a 3 position spring return to center, A to B center valve. this would allow free wheeling in the center position.


I'm not an expert on hydraulic motors but do a lot of industrial hydraulic work.
Thanks! Calls to manufactures help lines give opposing answers. Some make no sense. But a call to 1-219-762-2059 has
convinced me you are correct. Unfortunately  I can't find one that is low speed hi torque. All are in the thousands of RPM.

Offline Tacotodd

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Re: Running hyd motor in fwd and rev.
« Reply #29 on: June 03, 2021, 12:57:46 PM »
Like so many things in life, gearing is your friend. For example, your typical Warn electric winch is 315-1 and 3 sets of gears; but the Warn hydraulic industrial winch , I forget the gear reduction ratio, is 2 sets. Thatís why you need the proper gearing. 

Iím not trying to step on toes, just wanted to throw that example out there.
Trying harder everyday.

Offline moodnacreek

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Re: Running hyd motor in fwd and rev.
« Reply #30 on: June 03, 2021, 01:00:26 PM »
I would look at the wheel motors in Surplus Center. Also would get the tapered hub and attach sprocket to that. Lack of knowledge would make me go this way because you see machines like black top rollers forward and reverse constantly plus the weight of the machine. Alot depends on the hyd. flow you have on your mill. Prince makes a rotary valve that looks interesting.          Lanetec made a kit to put hyd. feed on a small sawmill. I believe it was spec't for the gig back speed and a return to tank flow control was used to slow down the feed speed, that's almost too simple.

Offline mike_belben

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Re: Running hyd motor in fwd and rev.
« Reply #31 on: June 03, 2021, 01:25:51 PM »
They do make wheel hub motors with integrated drum brake for hydraulic equipment.  Surplus center will have them and they are low speed high torque generic reversibles. Zero turns use em.


I am still on the fence about a motor center valve.  Send the log down the line and when you let off it slams into the end of the track and jumps off the carriage?  Or switch directions on the valve to stop it and now you get a reverse pressure spike anyway that the motor center was supposed to alleviate in the first place?   Which is the lesser of two evils i dont know.  


If there isnt a mechanical device like a brake to dissipate the carriage inertia before changing directions, theres gonna have to be a hydraulic one.  In my opinion anyways.. I am benchracing here and wish someone who has actually done this and dialed it in perfect would chime in.  I dont want to spend the OPs money but im still thinking its gonna take a cylinder spool with an adjustable cushion valve in each work port to bleed off the pressure spikes to tank.


A wheel motor with integrated brake hub could use a small bimba air cylinder with a DC solenoid pushbotton on a top gun joystick handle to blip the brakes when needed.  Thats the only way i can see a motor spool working.  Or maybe i guess a motor spool with a cushion valve so you dont snap anything when slamming it in reverse. 


I hope you keep us posted on the hurdles.
Psalm 37:16

Offline PoginyHill

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Re: Running hyd motor in fwd and rev.
« Reply #32 on: June 03, 2021, 01:52:34 PM »
A small accumulator on each of the lines to a hyd motor might absorb the worst of shocks if using a closed center valve. Heavier motors can withstand a fair amount of shock. If using an open center valve, a shock absorber at each end of the carriage travel might be all that is needed.
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Offline Machinebuilder

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Re: Running hyd motor in fwd and rev.
« Reply #33 on: June 03, 2021, 02:10:09 PM »
I think that motor is not bidirectional. When ordering there is a special order option for reverse direction.

to be sure call the tech support line and ask before purchasing one.

There are many other hydraulic motors that are bidirectional.

For the valve I think you want a 3 position spring return to center, A to B center valve. this would allow free wheeling in the center position.


I'm not an expert on hydraulic motors but do a lot of industrial hydraulic work.
Thanks! Calls to manufactures help lines give opposing answers. Some make no sense. But a call to 1-219-762-2059 has
convinced me you are correct. Unfortunately  I can't find one that is low speed hi torque. All are in the thousands of RPM.
I just spoke with my supplier and the Dynamic motor is bidirectional, it is a knockoff of similar CharLynn etc motors
Dave, Woodmizer LT15, Husqvarna 465 and 435, Bobcat 751, David Brown 770

Offline moodnacreek

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Re: Running hyd motor in fwd and rev.
« Reply #34 on: June 03, 2021, 06:34:59 PM »
They do make wheel hub motors with integrated drum brake for hydraulic equipment.  Surplus center will have them and they are low speed high torque generic reversibles. Zero turns use em.


I am still on the fence about a motor center valve.  Send the log down the line and when you let off it slams into the end of the track and jumps off the carriage?  Or switch directions on the valve to stop it and now you get a reverse pressure spike anyway that the motor center was supposed to alleviate in the first place?   Which is the lesser of two evils i dont know.  


If there isnt a mechanical device like a brake to dissipate the carriage inertia before changing directions, theres gonna have to be a hydraulic one.  In my opinion anyways.. I am benchracing here and wish someone who has actually done this and dialed it in perfect would chime in.  I dont want to spend the OPs money but im still thinking its gonna take a cylinder spool with an adjustable cushion valve in each work port to bleed off the pressure spikes to tank.


A wheel motor with integrated brake hub could use a small bimba air cylinder with a DC solenoid pushbotton on a top gun joystick handle to blip the brakes when needed.  Thats the only way i can see a motor spool working.  Or maybe i guess a motor spool with a cushion valve so you dont snap anything when slamming it in reverse.


I hope you keep us posted on the hurdles.
Mike, I suggested a wheel motor for strength and slow speed. The brake would not be used. Everything is done with the spool valve like mowing with one side of a 0 turn [even though that's closed center]  I put in a petition with the town of Greenville to name that section of 84 into Port 'Mike Belben Hill'

Offline Don P

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Re: Running hyd motor in fwd and rev.
« Reply #35 on: June 03, 2021, 07:13:21 PM »
I wonder if we're overthinking it. If I stay on the crowd it'll plow into either end of the mill till something breaks, I feather down at the end of the tracks. Release it and I'm in "neutral" I can roll the carriage by hand. If I slam it from forward to reverse it'll either shear the roll pin in the cable drum or snatch the eyebolts at the end of the carriage. I don't see hydraulics being different in that regard, just feather the levers  ???. I've been turning the bobcat around between tight block walls and posts in a basement all afternoon just nursing the controls.
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Offline Dangerous_Dan

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Re: Running hyd motor in fwd and rev.
« Reply #36 on: June 03, 2021, 08:19:52 PM »
Use a variable displacement pump.
It will give you forward and reverse with variable speed, torque and hydraulic braking.
First you make it work, then you trick it out!

Offline mike_belben

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Re: Running hyd motor in fwd and rev.
« Reply #37 on: June 03, 2021, 10:01:54 PM »
dan probably has the best suggestion of all there. 

if i were building a hydraulic carriage it would use a swash plate variable pump and a fixed displacement wheel motor.  basically hydrostatic and that will be comparable to operating a skid steer or zero turn because thats exactly what they are.  


now if you were using a fixed gear pump and modulating a valve to a fixed displacement motor it would be exactly what a Case hi-drive tractor is, which are about the jerkiest riding machines you can experience, ive had 2. it would take very long levers with completely tight pins to get the resolution necessary on the spool to feather a fixed displacement system.  they dont drive like hydrostatic at all and if they did, skid steer manufacturers would save a BUNDLE using them instead of variable piston pumps.   



@doug..  the hill did what hills do, i cant blame it for me being a moron.  now wawayanda court on the other hand..  ill never have nothing nice to say about them.  
Psalm 37:16

Offline Jim1934

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Re: Running hyd motor in fwd and rev.
« Reply #38 on: June 04, 2021, 09:18:04 AM »
dan probably has the best suggestion of all there.

if i were building a hydraulic carriage it would use a swash plate variable pump and a fixed displacement wheel motor.  basically hydrostatic and that will be comparable to operating a skid steer or zero turn because thats exactly what they are.  


now if you were using a fixed gear pump and modulating a valve to a fixed displacement motor it would be exactly what a Case hi-drive tractor is, which are about the jerkiest riding machines you can experience, ive had 2. it would take very long levers with completely tight pins to get the resolution necessary on the spool to feather a fixed displacement system.  they dont drive like hydrostatic at all and if they did, skid steer manufacturers would save a BUNDLE using them instead of variable piston pumps.  



@doug..  the hill did what hills do, i cant blame it for me being a moron.  now wawayanda court on the other hand..  ill never have nothing nice to say about them.  
Great info and insight!. If I could salvage a hydrostatic drive from say a 12 HP garden tractor
I think that would be ideal. Buying a $1k pump and separate wheel motor is out of the question.
We run the mill twice a year for our own use. Our big problem is the gig speed- about 8 ft/sec. Scary
even with feathering. An option to reduce carriage speed is to replace the 18 in. cable drum with an 8 inch one.
Might have to replace wire rope with smaller size. Nearly to the point of abandoning hyd. idea.
Thanks again. Jim.

Offline mike_belben

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Re: Running hyd motor in fwd and rev.
« Reply #39 on: June 04, 2021, 10:14:56 AM »
Actually its not as bad as you think.  You can get a new variable piston pump with the spring centering shaft gear for $130 then $20 for one half of the splined lovejoy L090 coupler.. $100 for a new fixed gear motor plus shipping.. Maybe tax, then hoses and whatever sprockets or belting to couple the motor.  Maybe $40 for the AA pump mount.  Could drive it with gas or electric.  $500 will surely do new everything except the engine.  A reservoir, filter and cooler obviously needs to be rigged up too. 


Old hydrostatic mowers used the best of parts but generally integrated the pumps and rears... Youd have quite a project separating them.  Walk behinds and zero turns did use independant components but most people arent gonna find a serviceable parts pile for less than new price at surplus center.


Jackshafting your current drum slower or dropping down in drum OD is still probably the way to go.
Psalm 37:16


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