Question on hydraulic motors

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perry

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Aug 22, 2006
Messages
869
How difficult to change out a bush hog gear drive for a hydraulic motor, and what would I need to look for in the hydraulic motor?.

Thanks
 

TriHonu

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Joined
Apr 15, 2007
Messages
486
I would not remove the gear box. I would remove the PTO shaft and use a hydraulic motor to turn the gearbox. I would also incorporate a shear pin in the drive assembly if the gearbox doesn't have a slip-clutch.
Both the neighbor an I have looked at the same conversion. You can buy pto brush mowers for a fraction of the cost of one already set up for a skidsteer.
You will want to know what speed PTO the mower was designed for. Most PTO's were either 540 or 1000 rpm. You will have to know the hydraulic flow in your auxiliary circuit to calculate what size hydraulic motor will give you the correct speed. If you use a chain drive from the hydraulic motor to the gear box your choice of motors is greatly increased since you can vary the chain sprocket sizes to get the correct RPM to the gearbox. Note that the larger the mower the more HP you need to turn it. Hydraulic HP is a function of pressure and flow. Your loaders engine HP is higher than the HP you can create from the auxiliary circuit. Keep this in mind when deciding how large a deck to convert.
Safety is up to you. The commercial units set up for skidsteers have a valve that will stop the hydraulic flow to the mower if it is raised off the ground. The instructions for my snowblower even state to use the intermittent switch when blowing and not to use the constant flow switch. I believe the same would apply to a mower.
 
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perry

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Joined
Aug 22, 2006
Messages
869
I would not remove the gear box. I would remove the PTO shaft and use a hydraulic motor to turn the gearbox. I would also incorporate a shear pin in the drive assembly if the gearbox doesn't have a slip-clutch.
Both the neighbor an I have looked at the same conversion. You can buy pto brush mowers for a fraction of the cost of one already set up for a skidsteer.
You will want to know what speed PTO the mower was designed for. Most PTO's were either 540 or 1000 rpm. You will have to know the hydraulic flow in your auxiliary circuit to calculate what size hydraulic motor will give you the correct speed. If you use a chain drive from the hydraulic motor to the gear box your choice of motors is greatly increased since you can vary the chain sprocket sizes to get the correct RPM to the gearbox. Note that the larger the mower the more HP you need to turn it. Hydraulic HP is a function of pressure and flow. Your loaders engine HP is higher than the HP you can create from the auxiliary circuit. Keep this in mind when deciding how large a deck to convert.
Safety is up to you. The commercial units set up for skidsteers have a valve that will stop the hydraulic flow to the mower if it is raised off the ground. The instructions for my snowblower even state to use the intermittent switch when blowing and not to use the constant flow switch. I believe the same would apply to a mower.
Found a 4' for $400 and thought it might be a good conversion, I like the hyd. to gear box idea...
 

skidsteer.ca

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Joined
Jan 20, 2006
Messages
3,853
Found a 4' for $400 and thought it might be a good conversion, I like the hyd. to gear box idea...
Perry
I have the same setup on a 60" king kutter.
The "crazy wheel" was moved to the front and the loader pushes it from the back end. It pivots up and down in front of the loader and the front end is lifted with chains coming forward from the top of the QA plate
I gave up renting it because the customers don't know how to baby it and I was forever fixing it. Front wheel ripped off, bent, broken hub. deck bent and punctured. Just running it myself has been alot better.
I see some mowers with the blades hung directly off the hyd motor, I don't know what motor they use but they would require vary heavy bearing and would have to be designed for such heavy use. Far cheaper would be to keep the gear box, new ones can be had for $160 to $250 and let it hold the blades and take the abuse.
The 60 hp gear boxes are made better with tapered roller bearing with adjustable preload where as the 40 hp gear boxes use ball bearing. I'm surprized the seals last at all, but they seem to. You can look at all the parts at www.kingkutter.com many makes and models use the same 40 or 60 hp gear boxes
Pesonally I would not want a chain drive for maintenance reasons, I had no trouble buying a motor that matched up with my loader to run the cutter "direct drive" near 540 rpm.
Also speed is not that critical. The ones I sell use 2 motors, One for std flow and one for hi flow. My cutter was originally set up for my 13 gpm 753, but it did ok on my 553 at 8.5 gpm.
When I got my 17 gpm 773 I resized the motor to maintain 540 rpm with a big increase in torque, but it was not as noticable as I thought it would be.
Honestly, I would look for a 5 or 6' cutter, because the 400.00 for the cutter will be the cheap part if you count your time and other materials. You will over time do quite a bit of re-inforcing of the deck. Fab mounts for the motor, set up a coupler to the gear box.
The 4' will work, but if you want to mow grass/fields your wheels will be tramping it unless you offset it to one side....
If you going to do alot of mowing your likely better off with a factory built skidsteer cutter. They have alot more steel in them. Erskines 6' is 1400 lbs
I keyed the shaft on my gear box to mount the coupler tight to it as I was finding the 5/16" shear pin allowed the outer coupler to wobble around and it was wearing itself out. The relief valve serves as a shear pin
You should also have a bypass loop with check valve in the system so when you stop the oil flow from the machine, the cutter can circulate its oil in a loop and wind down at its own pace as opposed to stopping right now.
Skidsteer cutter are alot more money, but most are made with 1/4" thick decks as opposed to 1/8" and have better bracing.
Also the "crazy wheel" on the front of my cutter, I have busted the hub out of it and bent/broke it off where it swings around.
The dish in the center that holds the blades had to be re-inforced as it bent and allowed the tips of the blades to come up and rub the underside of the deck All of this stuff would be much easier to beef up while it was still straight.
I can post you some pictures if you like.
Talk to the folks a www.surpluscenter.com for the hydraulics, or your local hyd shop.
Overall these do work quite well, but mowing brush is a tough job, hidden rocks,stumps, rough/uneven terrain. Skidsteer is way more nimble then a tractor and the hyd drive has some cushion so your gears and shafts will last much longer.
Ken
 
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perry

Well-known member
Joined
Aug 22, 2006
Messages
869
Perry
I have the same setup on a 60" king kutter.
The "crazy wheel" was moved to the front and the loader pushes it from the back end. It pivots up and down in front of the loader and the front end is lifted with chains coming forward from the top of the QA plate
I gave up renting it because the customers don't know how to baby it and I was forever fixing it. Front wheel ripped off, bent, broken hub. deck bent and punctured. Just running it myself has been alot better.
I see some mowers with the blades hung directly off the hyd motor, I don't know what motor they use but they would require vary heavy bearing and would have to be designed for such heavy use. Far cheaper would be to keep the gear box, new ones can be had for $160 to $250 and let it hold the blades and take the abuse.
The 60 hp gear boxes are made better with tapered roller bearing with adjustable preload where as the 40 hp gear boxes use ball bearing. I'm surprized the seals last at all, but they seem to. You can look at all the parts at www.kingkutter.com many makes and models use the same 40 or 60 hp gear boxes
Pesonally I would not want a chain drive for maintenance reasons, I had no trouble buying a motor that matched up with my loader to run the cutter "direct drive" near 540 rpm.
Also speed is not that critical. The ones I sell use 2 motors, One for std flow and one for hi flow. My cutter was originally set up for my 13 gpm 753, but it did ok on my 553 at 8.5 gpm.
When I got my 17 gpm 773 I resized the motor to maintain 540 rpm with a big increase in torque, but it was not as noticable as I thought it would be.
Honestly, I would look for a 5 or 6' cutter, because the 400.00 for the cutter will be the cheap part if you count your time and other materials. You will over time do quite a bit of re-inforcing of the deck. Fab mounts for the motor, set up a coupler to the gear box.
The 4' will work, but if you want to mow grass/fields your wheels will be tramping it unless you offset it to one side....
If you going to do alot of mowing your likely better off with a factory built skidsteer cutter. They have alot more steel in them. Erskines 6' is 1400 lbs
I keyed the shaft on my gear box to mount the coupler tight to it as I was finding the 5/16" shear pin allowed the outer coupler to wobble around and it was wearing itself out. The relief valve serves as a shear pin
You should also have a bypass loop with check valve in the system so when you stop the oil flow from the machine, the cutter can circulate its oil in a loop and wind down at its own pace as opposed to stopping right now.
Skidsteer cutter are alot more money, but most are made with 1/4" thick decks as opposed to 1/8" and have better bracing.
Also the "crazy wheel" on the front of my cutter, I have busted the hub out of it and bent/broke it off where it swings around.
The dish in the center that holds the blades had to be re-inforced as it bent and allowed the tips of the blades to come up and rub the underside of the deck All of this stuff would be much easier to beef up while it was still straight.
I can post you some pictures if you like.
Talk to the folks a www.surpluscenter.com for the hydraulics, or your local hyd shop.
Overall these do work quite well, but mowing brush is a tough job, hidden rocks,stumps, rough/uneven terrain. Skidsteer is way more nimble then a tractor and the hyd drive has some cushion so your gears and shafts will last much longer.
Ken
Valuable info.....thanks Ken............
 

Butters

Well-known member
Joined
Jan 23, 2007
Messages
72
Perry
I have the same setup on a 60" king kutter.
The "crazy wheel" was moved to the front and the loader pushes it from the back end. It pivots up and down in front of the loader and the front end is lifted with chains coming forward from the top of the QA plate
I gave up renting it because the customers don't know how to baby it and I was forever fixing it. Front wheel ripped off, bent, broken hub. deck bent and punctured. Just running it myself has been alot better.
I see some mowers with the blades hung directly off the hyd motor, I don't know what motor they use but they would require vary heavy bearing and would have to be designed for such heavy use. Far cheaper would be to keep the gear box, new ones can be had for $160 to $250 and let it hold the blades and take the abuse.
The 60 hp gear boxes are made better with tapered roller bearing with adjustable preload where as the 40 hp gear boxes use ball bearing. I'm surprized the seals last at all, but they seem to. You can look at all the parts at www.kingkutter.com many makes and models use the same 40 or 60 hp gear boxes
Pesonally I would not want a chain drive for maintenance reasons, I had no trouble buying a motor that matched up with my loader to run the cutter "direct drive" near 540 rpm.
Also speed is not that critical. The ones I sell use 2 motors, One for std flow and one for hi flow. My cutter was originally set up for my 13 gpm 753, but it did ok on my 553 at 8.5 gpm.
When I got my 17 gpm 773 I resized the motor to maintain 540 rpm with a big increase in torque, but it was not as noticable as I thought it would be.
Honestly, I would look for a 5 or 6' cutter, because the 400.00 for the cutter will be the cheap part if you count your time and other materials. You will over time do quite a bit of re-inforcing of the deck. Fab mounts for the motor, set up a coupler to the gear box.
The 4' will work, but if you want to mow grass/fields your wheels will be tramping it unless you offset it to one side....
If you going to do alot of mowing your likely better off with a factory built skidsteer cutter. They have alot more steel in them. Erskines 6' is 1400 lbs
I keyed the shaft on my gear box to mount the coupler tight to it as I was finding the 5/16" shear pin allowed the outer coupler to wobble around and it was wearing itself out. The relief valve serves as a shear pin
You should also have a bypass loop with check valve in the system so when you stop the oil flow from the machine, the cutter can circulate its oil in a loop and wind down at its own pace as opposed to stopping right now.
Skidsteer cutter are alot more money, but most are made with 1/4" thick decks as opposed to 1/8" and have better bracing.
Also the "crazy wheel" on the front of my cutter, I have busted the hub out of it and bent/broke it off where it swings around.
The dish in the center that holds the blades had to be re-inforced as it bent and allowed the tips of the blades to come up and rub the underside of the deck All of this stuff would be much easier to beef up while it was still straight.
I can post you some pictures if you like.
Talk to the folks a www.surpluscenter.com for the hydraulics, or your local hyd shop.
Overall these do work quite well, but mowing brush is a tough job, hidden rocks,stumps, rough/uneven terrain. Skidsteer is way more nimble then a tractor and the hyd drive has some cushion so your gears and shafts will last much longer.
Ken
I would love to see some pictures.
Did you use a 3 point hitch adapter plate to attach the mower?
 

skidsteer.ca

Well-known member
Joined
Jan 20, 2006
Messages
3,853
I would love to see some pictures.
Did you use a 3 point hitch adapter plate to attach the mower?
blades.JPG

I find it better to remove the blades and the holder from the gearbox. This way I don't disturb the blade bolts torque. I have never had a problem with the blade holder coming loose off the gearbox, but I have had trouble with the blade bolts. They must be vary tight
bypass%20loop%20and%20relief%20valve.JPG

Bypass loop has a check valve to prevent pressure from the loader escaping into it. Its purpose is for shutdown. During shutdown, the motor become the pump driven by the inertia of the rotating blades. Then the check valve opens and allows oil through the loop and back to the inlet side of the motor so the blades can wind down as opposed to being forced to stop instantly
Coupler%20motor%20to%20gear%20box.JPG

Original L110 lovejoy coupler was replaced with this. A separate single sprocket on the motor and gear box, coupled by a double wide roller chain. I cut a 1/4 keyway into the gearbox shaft with zip cuts on a angle grinder and quit using the 5/16 shear pin.

cutter%20deck%202.JPG

1/2 by 6 flat iron was run from the fron to rear of the deck at 1/3 and 2/3 the way across to prevent the fron of the deck from bending up further (like a ski) Also notice where the blade tips were rubbing the underside of the deck and the paint can be seen missing in a circle around the outside of the deck This was caused by dumping the bucket cylinders too much and making the crazy wheel carry the front of the loader (bottoming the pivot at the QA
cutter%20deck.JPG

Note the dents in the side of the 1/8 thick I beam that makes up the sides. 1/4 would be better, or a second layer in the hi impact areas.
Unpainted 1/2 by 6" flat can be seen standing on edge on top of the deck.
Note the old lovejoy coupling between the gear box and motor, this needed new rubbers every 20 hours.

Dents%20on%20side.JPG

closeup of dents on the side.
front%20wheel.JPG

This is the old crazy wheel mount. Way too light. The new one is made from 1.5 by 3 by 3/16 box iron and the wheel pivots around on a trailer hub and stub axel assemble that is still to light. I used a 4 stud 2k lb hub, should have used a 6 stud 6k lb hub. Also the hub in the center of the wheel has been rewelded in a few times.
Motor%20tag.JPG

Char Lyn Hyd motor tag. This motor has roller bearing to support the shaft. it was $375.00 at www.surpluscenter.com if I recall correctly and puts out @ 550rpm at 17 gpm flow.
I had a cheaper dan foss for 13 gpm originally, which siezed up. Likely from dirt in the quick couplers. It had no bearing though and worked like a engine crankshaft,floating on a cushion of oil. I could have replaced it for @ $200.
I also have a hi pressure filter I want to ad to the pressure line from the loader to protect the motor.
QA%20Pivot.JPG

Qa pivots here and is height adjustable
reinforced%20blade%20holder.JPG

I added the upright bracing on each side of the center hub, the blades were bending the holder up and the blade tips were hitting the underside of the deck. The 1/2 by 6 they layed flat was not strong enough.
Also blade bolts must be vary tight. Read 3/4 impact wrench tight.
Torque, run and retorqued after removal.
Ken
 
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OP
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perry

Well-known member
Joined
Aug 22, 2006
Messages
869
I find it better to remove the blades and the holder from the gearbox. This way I don't disturb the blade bolts torque. I have never had a problem with the blade holder coming loose off the gearbox, but I have had trouble with the blade bolts. They must be vary tight

Bypass loop has a check valve to prevent pressure from the loader escaping into it. Its purpose is for shutdown. During shutdown, the motor become the pump driven by the inertia of the rotating blades. Then the check valve opens and allows oil through the loop and back to the inlet side of the motor so the blades can wind down as opposed to being forced to stop instantly

Original L110 lovejoy coupler was replaced with this. A separate single sprocket on the motor and gear box, coupled by a double wide roller chain. I cut a 1/4 keyway into the gearbox shaft with zip cuts on a angle grinder and quit using the 5/16 shear pin.

1/2 by 6 flat iron was run from the fron to rear of the deck at 1/3 and 2/3 the way across to prevent the fron of the deck from bending up further (like a ski) Also notice where the blade tips were rubbing the underside of the deck and the paint can be seen missing in a circle around the outside of the deck This was caused by dumping the bucket cylinders too much and making the crazy wheel carry the front of the loader (bottoming the pivot at the QA

Note the dents in the side of the 1/8 thick I beam that makes up the sides. 1/4 would be better, or a second layer in the hi impact areas.
Unpainted 1/2 by 6" flat can be seen standing on edge on top of the deck.
Note the old lovejoy coupling between the gear box and motor, this needed new rubbers every 20 hours.

closeup of dents on the side.

This is the old crazy wheel mount. Way too light. The new one is made from 1.5 by 3 by 3/16 box iron and the wheel pivots around on a trailer hub and stub axel assemble that is still to light. I used a 4 stud 2k lb hub, should have used a 6 stud 6k lb hub. Also the hub in the center of the wheel has been rewelded in a few times.

Char Lyn Hyd motor tag. This motor has roller bearing to support the shaft. it was $375.00 at www.surpluscenter.com if I recall correctly and puts out @ 550rpm at 17 gpm flow.
I had a cheaper dan foss for 13 gpm originally, which siezed up. Likely from dirt in the quick couplers. It had no bearing though and worked like a engine crankshaft,floating on a cushion of oil. I could have replaced it for @ $200.
I also have a hi pressure filter I want to ad to the pressure line from the loader to protect the motor.

Qa pivots here and is height adjustable

I added the upright bracing on each side of the center hub, the blades were bending the holder up and the blade tips were hitting the underside of the deck. The 1/2 by 6 they layed flat was not strong enough.
Also blade bolts must be vary tight. Read 3/4 impact wrench tight.
Torque, run and retorqued after removal.
Ken
Appreciate the photos Ken, something to go by.....
 

dirthog28

Member
Joined
May 1, 2011
Messages
18
Appreciate the photos Ken, something to go by.....
Been a while since anyone has put up a update was curious if anyone had anything new to add or new ideas that they've done. I'm getting ready to convert a bush hog over to use on my skid steer. My machine puts out 18gpm and I was leaning towards a 5' to be able to handle more dense brush and small trees. I figured smaller deck would help keep Rpm moving or will a 6' handle it? Is there any differences in the 540 rpm gear boxes that will do better for working with a hydraulic motor?
 

dirthog28

Member
Joined
May 1, 2011
Messages
18
Been a while since anyone has put up a update was curious if anyone had anything new to add or new ideas that they've done. I'm getting ready to convert a bush hog over to use on my skid steer. My machine puts out 18gpm and I was leaning towards a 5' to be able to handle more dense brush and small trees. I figured smaller deck would help keep Rpm moving or will a 6' handle it? Is there any differences in the 540 rpm gear boxes that will do better for working with a hydraulic motor?
I was curious if you could do away with the gear box and place a direct drive motor if that would be any better, don't know what the cost would be compared to smaller motor going through gear box though.
 
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