PTO clutch

[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

 

[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:

 

[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!!

 

[Mad Mackie]

Burnishing a new clutch info link.
http://www.ganos.com/electricclutchtesting.pdf
Mad Mackie in CT

 

[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:

 

[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:

 

[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

 

[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

 

[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.

 

[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 ))