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PTO clutch
#1
G
gregjo1948
G
gregjo1948
What would cause a new clutch to burn up? About 5 hours and looks like a bearing seized and ruined the clutch on a 24hp. Z mower. Had torqued it to 55lbs per instuctions, belt pulleys aligned, and mowing normal height grass. (not stressing the machine at all) gregjo1948:confused2:
#2
R
Rivets
R
Rivets
If the bearing seized after only 5 hours of operation, I would suspect a bad clutch. Only other thing I can think of could be a problem with the electrical system,causing the pull-in coil to over heat.
#3
G
gregjo1948
G
gregjo1948
What could cause the coil to over heat? Is there a constant 12 volts going to the clutch or does it somehow drop after once it has been engaged? Thanks, gregjo1948
#4
M
Mad Mackie
M
Mad Mackie
With a properly functioning charging/electrical system, the clutch will get 13 plus volts DC.
Did you burnish the clutch correctly? If not, the clutch will slip which creates unwanted heat that could cause the bearing grease to either burn or run out past the seal. I did receive a new clutch with one bearing that had no grease in it. Since then I always inspect the bearings on new clutches by carefully lifting up the edge of a seal to look in. I have had clutches last 1,000 hours down to 100 hours.
Check the wiring diagram for your specific machine to see if there is a diode installed in the clutch wiring and if so, isolate it and check it with a ohmmeter.
Mad Mackie in CT
Did you burnish the clutch correctly? If not, the clutch will slip which creates unwanted heat that could cause the bearing grease to either burn or run out past the seal. I did receive a new clutch with one bearing that had no grease in it. Since then I always inspect the bearings on new clutches by carefully lifting up the edge of a seal to look in. I have had clutches last 1,000 hours down to 100 hours.
Check the wiring diagram for your specific machine to see if there is a diode installed in the clutch wiring and if so, isolate it and check it with a ohmmeter.
Mad Mackie in CT
#5
R
Rivets
R
Rivets
Mad Mackie, please educated me on electric PTO clutches used on today's lawn tractors. Where is the bearing seal? Where are you putting grease? To my knowledge the top half of the clutch contains a electromagnetic coil and has a self contain key which fits into the keyway on the crankshaft. When the PTO switch is engaged, the coil draws the clutch cup (which is also part of the clutch pulley) up against the magnet making it one solid unit. Most clutches also have return springs to push the two halves apart when the power is turned off. There is also a clutch stop which keeps the top half housing from turning. No posse that I have ever seen calls for grease or has a grease seal. Is there a new type of clutch that I have never seen or heard about.
#6
M
Mad Mackie
M
Mad Mackie
Hi Rivets,
I hope that you are "pulling my leg" about electric PTO clutches, but here goes!!
Having been an aircraft mech over the years I have a set of tools for safely removing O rings and I use some of these tools to lube bearings that have non metal seals installed on them.
Every electric PTO clutch that I have dealt with has at least two bearing and clutches with more than one pulley may have more than two bearings.
I use a new scribe that I have gently removed the sharp tip from using a sharpening stone. This I use to initially get under the bearing seal. I follow it up with another tool which is a brass rod that has been hammered flat and I use this to gently lift the seal so I can slip in a hypodermic needle that has a grease fitting installed onto it. This is an automotive tool that is used to do a fast and dirty lube to a CV joint on a front drive vehicle by sticking it thru the boot and pumping in some grease. The grease that I use is sold by some bearing manufacturers, but there are aftermarket suppliers that package similar grease.
All electrical PTO clutches for power equipment have a brake incorporated into them and many are directionally sensitive. New clutches need to be burnished when installed, otherwise they will slip which causes excessive heat that can adversely affect the bearings and the V belt. Most have an adjustable airgap so the brake will properly clear when the clutch is engaged and not drag which also can also cause unwanted excessive heat.
Go online for both Warner and Ogura and there is technical info for PTO and other types of electrical clutches, however nothing about lubing the bearings.
The pulley bearing turns when the PTO is not engaged, the coil plate bearing turns all the time the engine is running and at the same RPM as the engine. This is the bearing which has the sleeve with the key slot that engages the key slot in the crankshaft.
Mad Mackie in CT :laughing::biggrin::smile:
Was Boomer able to help you finding an Onan flywheel???
I hope that you are "pulling my leg" about electric PTO clutches, but here goes!!
Having been an aircraft mech over the years I have a set of tools for safely removing O rings and I use some of these tools to lube bearings that have non metal seals installed on them.
Every electric PTO clutch that I have dealt with has at least two bearing and clutches with more than one pulley may have more than two bearings.
I use a new scribe that I have gently removed the sharp tip from using a sharpening stone. This I use to initially get under the bearing seal. I follow it up with another tool which is a brass rod that has been hammered flat and I use this to gently lift the seal so I can slip in a hypodermic needle that has a grease fitting installed onto it. This is an automotive tool that is used to do a fast and dirty lube to a CV joint on a front drive vehicle by sticking it thru the boot and pumping in some grease. The grease that I use is sold by some bearing manufacturers, but there are aftermarket suppliers that package similar grease.
All electrical PTO clutches for power equipment have a brake incorporated into them and many are directionally sensitive. New clutches need to be burnished when installed, otherwise they will slip which causes excessive heat that can adversely affect the bearings and the V belt. Most have an adjustable airgap so the brake will properly clear when the clutch is engaged and not drag which also can also cause unwanted excessive heat.
Go online for both Warner and Ogura and there is technical info for PTO and other types of electrical clutches, however nothing about lubing the bearings.
The pulley bearing turns when the PTO is not engaged, the coil plate bearing turns all the time the engine is running and at the same RPM as the engine. This is the bearing which has the sleeve with the key slot that engages the key slot in the crankshaft.
Mad Mackie in CT :laughing::biggrin::smile:
Was Boomer able to help you finding an Onan flywheel???
#7
Carscw
Carscw
I don't understand what the advantage is with the electric clutch over a manual clutch ( pto set up with a lever )
At $250 a pop I don't think I want a mower with one.
(( racing is the only sport that you need two balls ))
At $250 a pop I don't think I want a mower with one.
(( racing is the only sport that you need two balls ))
#8
M
Mad Mackie
M
Mad Mackie
First off the Feds safety folk got involved in the 80s and mandated that a brake be incorporated into the mower clutch system. Secondly, the design of ZTR machines doesn't lend to having a manually engaged deck clutch.
I know what it is like at $250 or more at a pop, one of my machines is on it's 5th clutch, but the machine has almost 2,500 hours on it and an operator, me, that pushes machines hard year round!!!
Mad Mackie in CT:laughing::biggrin::smile:
I know what it is like at $250 or more at a pop, one of my machines is on it's 5th clutch, but the machine has almost 2,500 hours on it and an operator, me, that pushes machines hard year round!!!
Mad Mackie in CT:laughing::biggrin::smile:
#9
G
gregjo1948
G
gregjo1948
Rivets-- I believe Mad Mackie is talking about the seal on a sealed bearing, not a seperate seal. Mad Mackie-- I did not burnish the clutch. I wasn't awear of the need to do so. Wouldn't you think they would supply that info with installation instructions. There were no instuctions on the torque specs either, but I found that online. Thanks for the education!:smile: gregjo1948
#10
R
Rivets
R
Rivets
No, I was not pulling your leg. In my 40+ years of teaching and working on small engines and the equipment they run, I have never greased a clutch bearing, nor heard of it being done. That being said, I don't work on the larger clutches. Have been going to up-date schools and was certified for warranty work by many of the equipment manufacturers and that was never brought up. Don't remember the last time I had to burnish one before installing, although I have had to send a few back that were so far turned over that they would not go on. With seals, I would understand if you were talking about the bearing seal and not a grease seal. I have see clutches that have failed due to being seizure, but 90% are due to coil failure, 5% due to bearing seizure and 5% due to stupid operators. The bearing seizures that I can remember happen either in the first 25 hours or after many years of use. From your description, I don't think I am going to change my procedure when working on them, but it will be in the back of my mind, what's left of it.
#11
M
Mad Mackie
M
Mad Mackie
Hi Rivets and group,
For sure the bearing regreasing thing is only practiced by a few. I have a set of regreasing tools that was intended for aircraft use primarily on flight control bearings most of which never make a full turn during normal operation. I do use these regreasers on the pulleys on my GTs and ZTRs. Occasionally when regreasing a pulley bearing, the seal will get damaged or roll under some. If the seal rolls under, I get out one of my "special tools" and attempt to pull it back to its normal position without damaging it. It is easy to over grease a bearing using these regreasers, one must be careful. The seal on the other side will lift up to relieve the grease and pressure from the grease gun. I have also regreased bearings that have metal seals or shields as they are sometimes called. There is a small gap on the inside diameter of the shield that will let grease flow into the bearing. However some metal shielded bearings also have a soft seal underneath.
Most of the replacement clutches that I have received had burnishing instructions included in the package with the clutch. My Scag Tiger Cub operators manual had an additional loose page in it covering the procedure for burnishing a new clutch. I will look thru my tractor stuff to find an instruction sheet, scan it and post it here.
The purpose of burnishing is to allow the two surfaces to become accustomed to each other before high RPM and load is applied while mowing which increases the torque loading of the clutch.
Generally done at 2,000 RPM with 2-10 second periods of on and off for up to 20 cycles or even more. Then some recommend a small increase in RPM and do the same thing, letting the clutch cool for sometimes up to 1/2 hour between.
This insures better engagement of the clutch mating surfaces and prolongs clutch life. Each manufacturer has a burnishing procedure and they vary depending on the torque rating of the clutch. Some clutches are rated up to 350 FT LBS for example ZTRs with deck widths of 60" and more.
I always check the airgap on a new clutch prior to installing it and bring it to within the specs if needed.
I gotta get rolling, got up to six lawns to do today!! Still recovering from a nasty tooth extraction, but I'll live!!!!
Mad Mackie in CT
For sure the bearing regreasing thing is only practiced by a few. I have a set of regreasing tools that was intended for aircraft use primarily on flight control bearings most of which never make a full turn during normal operation. I do use these regreasers on the pulleys on my GTs and ZTRs. Occasionally when regreasing a pulley bearing, the seal will get damaged or roll under some. If the seal rolls under, I get out one of my "special tools" and attempt to pull it back to its normal position without damaging it. It is easy to over grease a bearing using these regreasers, one must be careful. The seal on the other side will lift up to relieve the grease and pressure from the grease gun. I have also regreased bearings that have metal seals or shields as they are sometimes called. There is a small gap on the inside diameter of the shield that will let grease flow into the bearing. However some metal shielded bearings also have a soft seal underneath.
Most of the replacement clutches that I have received had burnishing instructions included in the package with the clutch. My Scag Tiger Cub operators manual had an additional loose page in it covering the procedure for burnishing a new clutch. I will look thru my tractor stuff to find an instruction sheet, scan it and post it here.
The purpose of burnishing is to allow the two surfaces to become accustomed to each other before high RPM and load is applied while mowing which increases the torque loading of the clutch.
Generally done at 2,000 RPM with 2-10 second periods of on and off for up to 20 cycles or even more. Then some recommend a small increase in RPM and do the same thing, letting the clutch cool for sometimes up to 1/2 hour between.
This insures better engagement of the clutch mating surfaces and prolongs clutch life. Each manufacturer has a burnishing procedure and they vary depending on the torque rating of the clutch. Some clutches are rated up to 350 FT LBS for example ZTRs with deck widths of 60" and more.
I always check the airgap on a new clutch prior to installing it and bring it to within the specs if needed.
I gotta get rolling, got up to six lawns to do today!! Still recovering from a nasty tooth extraction, but I'll live!!!!
Mad Mackie in CT
#12
M
Mad Mackie
M
Mad Mackie
Most of the larger clutch failures that I have seen are due to bearing failure. I have seen a clutch failure where the coil shorted to ground but not enough to quickly blow the fuse. The operator kept replacing the fuse and continued operating the machine until the engine had a major internal failure. The engine failure was do to the shorted clutch coil seeking the path of least resistance to ground which happened to be thru the engine main bearings. The bearings being the least noble of the metals involved, deteriorated and caused a serious drop in oil pressure which lead to the engine failure. This is rare but it does happen.
I have a grounding bond wire on the clutch on my 4018 Ingersoll which has a horizontal crankshaft engine. The clutch on the 18 Briggs Vanguard is a Warner 5215-88.
Anyway, I gotta go to work and do some mowing today!!
Later
Mad Mackie in CT:laughing::biggrin::smile:
I have a grounding bond wire on the clutch on my 4018 Ingersoll which has a horizontal crankshaft engine. The clutch on the 18 Briggs Vanguard is a Warner 5215-88.
Anyway, I gotta go to work and do some mowing today!!
Later
Mad Mackie in CT:laughing::biggrin::smile:
#13
M
Mad Mackie
M
Mad Mackie
One more thought before I have to hook up and go!!!
Corrosion in electrical connectors on machines can cause high resistance which will decrease the system voltage when a load is applied such as turning on the PTO switch. When the voltage is decreased, the amperage demand increases.I have cut out many connectors on machines particularly where I find the plastic connector has been melted from heat. Depending on what connector this is, I may reconnect using butt connectors or spade terminals as in the case with a switch. I always make note of this whether my machines or customers machines, usually in the operators manual.
Later
Mad Mackie in CT 55 years of wrenching, from bicycles to corp jets!!
Corrosion in electrical connectors on machines can cause high resistance which will decrease the system voltage when a load is applied such as turning on the PTO switch. When the voltage is decreased, the amperage demand increases.I have cut out many connectors on machines particularly where I find the plastic connector has been melted from heat. Depending on what connector this is, I may reconnect using butt connectors or spade terminals as in the case with a switch. I always make note of this whether my machines or customers machines, usually in the operators manual.
Later
Mad Mackie in CT 55 years of wrenching, from bicycles to corp jets!!
#15
G
gregjo1948
G
gregjo1948
Mad Mackie-- While burnishing a new clutch, being a directional sensative unit, it seems to me that engaging it many times at that high rpm would damage the fingers. I use "fingers" because I don't know the proper term for the internal parts of the clutch. I am under the belief, that engaging the clutch at high rpms, will damage the clutch enough to shorten the life span of it. gregjo1948:confused2:
#16
M
Mad Mackie
M
Mad Mackie
Correct burnishing of a new clutch is critical to its service life and this is more important with clutches of higher torque ratings. Burnishing is done at lower RPM and as most engines idle around 1,700-1,800 RPM, so burnishing at 2,000 RPM is not considered to be high. Part of the purpose of burnishing is to correctly seat the clutch brake.
Some but not all mower manufacturers will burnish the clutch on new machines as they reach the end of the assembly line and test run the machines prior to shipment.
When a clutch is replaced, then it becomes the responsibility of the installer/operator to check the air gap to be within spec, correctly install and torque the bolt and properly burnish the new clutch.
Both Warner and Ogura have burnishing instructions for their clutches and the procedures vary between clutch types and series.
Most or all electric PTO clutches are directionally sensitive. Clutches have three or six "fingers" and tension loading of these fingers is the correct direction. On clutches of opposite direction, these fingers will be connected in opposite directions. The idea is that the clutch pulley is pulled by these fingers, which are called armature springs. These armature springs not only pull the pulley, they flex and allow the clutch torque mating surfaces to make contact and drive the pulley when a magnetic field is created by the clutch coil. The directional orientation of a clutch is as one looks directly at the pulley. If a clutch is setup to be installed with the pulley close to the engine, then it is a CW clutch. If it is setup so the pulley is away from the engine, then it is a CCW clutch. This configuration is not consumer changeable. All engines that are used on power equipment turn CW as one views the flywheel. So "viewing" the engine from the flywheel thru the crankshaft output reduces the confusion of rotation. All PTO clutch manufacturers recommend that the clutch be engaged at a lower RPM to extend its serviceable lifespan, however this is much more easily said than done! As I mow, I frequently turn the PTO on and off at 3,600 RPM as conditions change in the area that I am mowing. I am aware that this will reduce the service life of the clutch and it is something that I must deal with as I operate and maintain my machines.
Mad Mackie in CT:laughing::biggrin::smile:
Tomorrow there will be a quiz on clutches!!! HaHa!!!:laughing:
Some but not all mower manufacturers will burnish the clutch on new machines as they reach the end of the assembly line and test run the machines prior to shipment.
When a clutch is replaced, then it becomes the responsibility of the installer/operator to check the air gap to be within spec, correctly install and torque the bolt and properly burnish the new clutch.
Both Warner and Ogura have burnishing instructions for their clutches and the procedures vary between clutch types and series.
Most or all electric PTO clutches are directionally sensitive. Clutches have three or six "fingers" and tension loading of these fingers is the correct direction. On clutches of opposite direction, these fingers will be connected in opposite directions. The idea is that the clutch pulley is pulled by these fingers, which are called armature springs. These armature springs not only pull the pulley, they flex and allow the clutch torque mating surfaces to make contact and drive the pulley when a magnetic field is created by the clutch coil. The directional orientation of a clutch is as one looks directly at the pulley. If a clutch is setup to be installed with the pulley close to the engine, then it is a CW clutch. If it is setup so the pulley is away from the engine, then it is a CCW clutch. This configuration is not consumer changeable. All engines that are used on power equipment turn CW as one views the flywheel. So "viewing" the engine from the flywheel thru the crankshaft output reduces the confusion of rotation. All PTO clutch manufacturers recommend that the clutch be engaged at a lower RPM to extend its serviceable lifespan, however this is much more easily said than done! As I mow, I frequently turn the PTO on and off at 3,600 RPM as conditions change in the area that I am mowing. I am aware that this will reduce the service life of the clutch and it is something that I must deal with as I operate and maintain my machines.
Mad Mackie in CT:laughing::biggrin::smile:
Tomorrow there will be a quiz on clutches!!! HaHa!!!:laughing:
#17
G
gregjo1948
G
gregjo1948
I've never checked idle rpm on a lawn mower. I'm looking at idle rpm of cars, trucks, tractors, dozers,backhoes, and etc. The idle rpm is usually 500 to 900. If you're running a diesel, the max rpm may be governed at 2150. If the idle rpm on mowers is 1700-1800; what is the governed max rpm? A quiz will only show my inability to learn at my advanced years. ( Can't teach an old dog new tricks):laughing: gregjo1948
#18
M
Mad Mackie
M
Mad Mackie
Most or all small engines are governed and accomplished by different systems however accomplishing the same results.
The governor has a low idle stop and a high idle stop and springs of various strengths are installed to change the high idle RPM. On most gasoline twins the low idle is from 1,700-2,000 RPM and the high idle is usually 3,600 RPM but some machines have been changed to 3,200 RPM to extend engine life.
With the engine governor setup at the factory to the mower manufacturers specs, the throttle cable connects to the governor and when the throttle position is changed, the engine governor will react to get to and maintain the selected RPM by controlling the throttle position in the carburetor.
The low idle speed of small aircooled engines has to do with maintaining cooling air flow and hydraulic oil flow in the drive units and not relative to the idle RPM of any vehicles most of which are not governed.
Mad Mackie in CT
The governor has a low idle stop and a high idle stop and springs of various strengths are installed to change the high idle RPM. On most gasoline twins the low idle is from 1,700-2,000 RPM and the high idle is usually 3,600 RPM but some machines have been changed to 3,200 RPM to extend engine life.
With the engine governor setup at the factory to the mower manufacturers specs, the throttle cable connects to the governor and when the throttle position is changed, the engine governor will react to get to and maintain the selected RPM by controlling the throttle position in the carburetor.
The low idle speed of small aircooled engines has to do with maintaining cooling air flow and hydraulic oil flow in the drive units and not relative to the idle RPM of any vehicles most of which are not governed.
Mad Mackie in CT
#19
M
Mad Mackie
Diesel engine on machines that having mowing capabilities need to turn close to or at 3,600 RPM and governed in order to turn the mower decks to the correct blade speed.
M
Mad Mackie
I've never checked idle rpm on a lawn mower. I'm looking at idle rpm of cars, trucks, tractors, dozers,backhoes, and etc. The idle rpm is usually 500 to 900. If you're running a diesel, the max rpm may be governed at 2150. If the idle rpm on mowers is 1700-1800; what is the governed max rpm? A quiz will only show my inability to learn at my advanced years. ( Can't teach an old dog new tricks):laughing: gregjo1948
Diesel engine on machines that having mowing capabilities need to turn close to or at 3,600 RPM and governed in order to turn the mower decks to the correct blade speed.
#20
Carscw
Could they not just use a bigger pulley on the engine and a smaller one on the deck?
I know that would increase blade speed (rpm )
But thinking it would not be able to hold the speed when in thick grass ( under a load )
(( racing is the only sport that you need two balls ))
Carscw
Diesel engine on machines that having mowing capabilities need to turn close to or at 3,600 RPM and governed in order to turn the mower decks to the correct blade speed.
Could they not just use a bigger pulley on the engine and a smaller one on the deck?
I know that would increase blade speed (rpm )
But thinking it would not be able to hold the speed when in thick grass ( under a load )
(( racing is the only sport that you need two balls ))
#21
djdicetn
djdicetn
WOW, what an intersting read.....everything I always wanted to know about PTO clutches and was definitely afraid to ask:0)
Mad Mackie,
If my PTO clutch on my Gravely(heaven forbid) ever goes south, can I just load er up on my trailer and bring it to you to repair?? You sure do know the ins-n-outs of these things!!! It would be worth a nice relaxing trip from Tennessee to Connecticut just to feel comfortable that the new clutch would be installed properly!!!
P.S.
The extent of my knowledge is that I do follow the Gravely User Manual and ALWAYS engage my PTO at no more than half-throttle. Maybe that'll help it last a very long time. It's an Ogura GT 2.5 so is that a "good one"???
Mad Mackie,
If my PTO clutch on my Gravely(heaven forbid) ever goes south, can I just load er up on my trailer and bring it to you to repair?? You sure do know the ins-n-outs of these things!!! It would be worth a nice relaxing trip from Tennessee to Connecticut just to feel comfortable that the new clutch would be installed properly!!!
P.S.
The extent of my knowledge is that I do follow the Gravely User Manual and ALWAYS engage my PTO at no more than half-throttle. Maybe that'll help it last a very long time. It's an Ogura GT 2.5 so is that a "good one"???
#22
M
Mad Mackie
M
Mad Mackie
Hi djdicetn,
Thank you for your comments!
From TN to CT would be a long trip and for sure not relaxing having to go thru NJ, NY, and western CT!!!!
To ensure correct torque on a clutch bolt I would have a second person hold a breaker bar with a socket on the flywheel nut as the clutch bolt is torqued. The debris screen would need to be removed from the flywheel and on some engines this means that the blower housing needs to be removed to gain access to the debris screen.
The best things to do are to periodically check the clutch coil continuity with an Ohmmeter to see if the coil is still in spec and also not shorted to ground, and check the airgap which affects the clutch brake. The airgap is adjustable and can be brought back to spec, however a tricky adjustment to do as there are three adjusting nuts 120 degrees from each other. I use three short thickness gauges to do this and I do it with the clutch removed from the engine.
Having discussed electric clutches with several dealer friends, Both Ogura and Warner have some great and not so great units in their lines!!! I see that another company has come out with a line of clutches that have turned pulleys verses stamped ones and replaceable bearings, not sure of the company name, but I see more numbers as time passes.
I've got an old Gravely walk behind here for service, early 1980s machine. I need to return it to the customer but it has been raining all day here and muddy at the customers place, I don't want to get my truck and trailer stuck!!!
Mad Mackie in CT:laughing::biggrin::smile:
Thank you for your comments!
From TN to CT would be a long trip and for sure not relaxing having to go thru NJ, NY, and western CT!!!!
To ensure correct torque on a clutch bolt I would have a second person hold a breaker bar with a socket on the flywheel nut as the clutch bolt is torqued. The debris screen would need to be removed from the flywheel and on some engines this means that the blower housing needs to be removed to gain access to the debris screen.
The best things to do are to periodically check the clutch coil continuity with an Ohmmeter to see if the coil is still in spec and also not shorted to ground, and check the airgap which affects the clutch brake. The airgap is adjustable and can be brought back to spec, however a tricky adjustment to do as there are three adjusting nuts 120 degrees from each other. I use three short thickness gauges to do this and I do it with the clutch removed from the engine.
Having discussed electric clutches with several dealer friends, Both Ogura and Warner have some great and not so great units in their lines!!! I see that another company has come out with a line of clutches that have turned pulleys verses stamped ones and replaceable bearings, not sure of the company name, but I see more numbers as time passes.
I've got an old Gravely walk behind here for service, early 1980s machine. I need to return it to the customer but it has been raining all day here and muddy at the customers place, I don't want to get my truck and trailer stuck!!!
Mad Mackie in CT:laughing::biggrin::smile: