scag tiger cub electric clutch.

[Mad Mackie]

Is that center sleve stepped to hold the baring's in place?
Or is there shoulder in the clutch for the bearings?

Hi John R,
I have no idea as I've never had one of these Ogura clutches apart yet. Several years ago I thought that I was having a clutch problem with my Tiger Cub so I bought a spare. Turns out that I had a ground problem on one of the terminals that are mounted on one of the engine mounting bolts.
I would think that there was at least one shoulder on the center sleeve to facilitate factory assembling, possibly two.
I'll look closer at my spare and check it out. There is an internal snap ring on the pulley bearing which is somewhat promising.
Lower torque clutches stake in the bearings and the stakes need to be ground off in order to both remove and install a new bearing, not easy to do without damaging the stamped sheet metal pulley and housing.
My Ingersoll 4018 garden tractor has a horizontal engine with the clutch on the front of the engine. I remove this clutch periodically, carefully lift the plastic seal and with a needle grease gun adapter, lube the bearings, but this is an easy job to do. This clutch gets overheated from hot engine cooling air and close location to the muffler. I have installed a heat shield on this machine, but I'm not convinced that it does much. I even bought special high temp ball bearing grease for this application.

 

[Mad Mackie]

Hi again John R and group,
Just looked at my spare Scag clutch, I can't see in at the center sleeve, but I measured the ID of each bearing and the pulley bearing (brown seal) has a smaller ID than the housing bearing (blue seal). This leads me to believe that the sleeve has at least one shoulder and I'll bet that it has two shoulders. This sure would make assembling and reassembling this clutch with new bearings an easy job on a press.
The pulley bearing, brown seal, Japan 34 NACHI 6008NSE
The housing bearing, blue seal, Japan 612 NACHI 6007/37NSE

 

[bertsmobile1]

Must admit, have never looked that closely at the bearings.
I am staggered to find out they are 60 series bearings which are the lightest duty bearings in the metric numbering system.
The second number gets higher as the bearings get stronger.
Thus on domestic ride ons the spindle bearings are generally the 62 series typically 6203, 6205 & 6207
Commercial ride ons generally have heavier duty bearings typically 63's
60's are very light bearings so it is no wonder they collapse .

Working on the Henry Ford principle the bearings would have a working life within 10% of the expceted life of the clutch face & spring.

 

[Mad Mackie]

I know operators with similar clutches with 3,000 hours on them.
A few years back I repowered an older Scag Turf Tiger for a fellow operator and reinstalled the original clutch as there wasn't anything wrong with it.
Turf Tigers have a horizontal engine and the clutch is easy to replace.
My Tiger Cub has 800 hours on it with no signs of bearing or airgap problems. I turn the PTO on an off at full throttle.
All of my commercial machines have tapered roller bearings in the deck spindles.

 

[Mad Mackie]

Evidently the bearing "Japan 612 NACHI 6007/37NSE" is a specialized bearing and not available.
This bearing may have a brass bushing of some sort attached to one side which may have something to do with the brake as these clutches are clutch/brakes.
Just my thoughts!!
If and when the clutch on my Tiger Cub fails, I will disassemble it, but this may be a long time away!!!!

 

[scagman2]

Electric clutch/brakes last just so long. Usually one of the bearings uses up its grease and overheats. One bearing turns all the time that the engine is running, the pulley bearing turns unless the clutch is on.
Replacing these bearings is not recommended due to their precise positioning and the high probability of damaging the clutch parts when both removing and installing the bearings.
These clutches when mounted on a vertical shaft engine are in a nasty environment being under the machine.
As reynoldston has mentioned, an over greasing situation would destroy the clutch.
Before installing a new clutch, cleaning up the crankshaft where the clutch mounts and applying a very slight amount of anti-seize compound to the crankshaft before installing the clutch is recommended, applying the correct torque to the clutch mounting bolt is highly recommended, do not apply anti-seize to this bolt, the torque spec is for a dry torque.
I remove the screen above the flywheel and hold the flywheel nut with a socket and a breaker bar as I torque the clutch bolt to the correct dry torque spec.
Generally easier to do with one side of the machine jacked up and a rear wheel removed.

What is the torque spec? Will be installing new clutch soon, spec, not in my operator's manual.

 

[mechanic mark]

http://ogura-clutch.com/files/pdfIMP/PTOinstallation.pdf

 

[scagman2]

http://ogura-clutch.com/files/pdfIMP/PTOinstallation.pdf

Thanks mechanic mark... great link... ready to install... thanks to all who joined in.

 

[scagman2]

Electric clutch/brakes last just so long. Usually one of the bearings uses up its grease and overheats. One bearing turns all the time that the engine is running, the pulley bearing turns unless the clutch is on.
Replacing these bearings is not recommended due to their precise positioning and the high probability of damaging the clutch parts when both removing and installing the bearings.
These clutches when mounted on a vertical shaft engine are in a nasty environment being under the machine.
As reynoldston has mentioned, an over greasing situation would destroy the clutch.
Before installing a new clutch, cleaning up the crankshaft where the clutch mounts and applying a very slight amount of anti-seize compound to the crankshaft before installing the clutch is recommended, applying the correct torque to the clutch mounting bolt is highly recommended, do not apply anti-seize to this bolt, the torque spec is for a dry torque.
I remove the screen above the flywheel and hold the flywheel nut with a socket and a breaker bar as I torque the clutch bolt to the correct dry torque spec.
Generally easier to do with one side of the machine jacked up and a rear wheel removed.

Hi M.M. Could you explain in detail the bearing rotation/operation for the ogura 3.5 mco7 clutch? refer to each as upper or lower please. I understand the constant upper rotation, but not the lower... can't wrap my head around that one. Could you please explain?

 

[Mad Mackie]

Hi scagman2,
I am very aware that the engineering drawings of the clutch components are not easy to identify.
Here are the basic requirements of a mower clutch:
Be able to turn a V belt that drives the mower deck with the engine running.
Be able to stop the V belt from driving the mower deck with the engine running.
Provide an "clutch" that will allow the above mentioned to happen.
The clutch being the parts that engage/disengage as desired.
Provide the power/force needed to operate the clutch.
In the Ogura clutch assembly that we have on our Scag Tiger Cubs and many others machines, electricity is the power provided and magnetism is the force.
An electrical coil, when power is applied, provides the magnetic force to operate the parts of the clutch. This coil does not rotate with the crankshaft of the engine.
It is mounted on the lower triangular plate of the clutch assembly which has a bearing pressed into it. The rest of the clutch assembly rotates with the crankshaft with the exception of the deck V belt drive pulley, which also has a bearing installed in it. All of this is mounted onto the sleeve that pushes up against the pump drive pulley and is held in place by a keyway, key and the bolt that threads into the center of the crankshaft.
When the PTO switch is in the on position, power causes the coil to make magnetism which brings the two steel clutch plates together and turns the mower deck.
When the PTO switch is in the off position, the magnetism stops and the clutch plates separate stopping the mower deck from turning.
"Burnishing" of the clutch is when at lower engine RPMs, the clutch is operated intermittently to allow the friction surfaces of the clutch plates to wear into each other gradually so they will not slip during normal mower operation.
The six fingers shown in the Ogura diagrams are what flex when the clutch is engaged and also pull the V belt pulley when the PTO is on.
As these clutches are actually a clutch/brake, when the PTO switch is turned off, the brake engages to stop the clutch quickly. This braking action is adjustable by changing the air gap adjustments. Too small of an airgap will cause the brake to drag, to big of an airgap will cause clutch slippage and slower braking action.
The bottom line to the bearings is that the lower bearing turns all the time that the engine is running.
The pulley bearing turns all the time that the PTO is off and stops turning when the PTO is on as it now turns with the crankshaft.
Time for Mad Mackie to refill his adult beverage container!!!:laughing: