AssemblyAssembly consisted of:
• lubrication of the cleaned shaft and other inner components
• placement of springs, washers and shims on the sprocket side before bolting that clutch pulley on,
• ditto with the battery side
• replacement of the shaft bearings, and
• replacement of the sprocket.
I used powered graphite as the lubricant for the cleaned up square shaft and inner plates. It has been mentioned elsewhere in the forum, as well as spray on silicone dry lubricants. In the past I’ve had better results with carbon over the spray ons, and I think it is possible to apply more and have it last longer. It is messy but being generous won’t cause a problem. A nickel anti-sieze compound had also been recommended but the version of that I got was somewhat gritty and not smooth like a lubricant, so it wasn’t suitable. After lubrication with plenty of smoothed-on graphite, both inner plates and the yoke bearing were suitably free on the square shaft.
Next were the washers, springs and shims. Having read posts in this forum, their adjustment appears to be a dark art. Having looked at the mechanism I think that it’s quite clear. Starting from the outside in, the large nut holding an outer clutch pulley onto the shaft bears on the inner race of the clutch pulley bearing, which in turn bears on the shims and a washer, which butt up against the sharp shoulder of the inner square section of the centre shaft. Same for the other side. I think that any shims that are used should be installed between the bearing and the washer, not between the washer and the shaft, because the shims are not strong enough to resist deformation if the outer pulley bolt is done up extra hard – one of the shims that I removed had been so distorted.
The inner plates and yoke bearing form a constant-width assembly that is centred in the gap between the outer clutch pulleys by the spring on each side of the inner assembly. The springs rotate with the square shaft between the hubs of the inner plates and the washers of the outer pulleys. The gap between the large outer pulleys is set by the width of the square section of the shaft, the thickness of the washers and the thickness of any added shims. Because my problem was with binding of the plates I added shims to ensure that I had plenty of clearance between the cork linings and the outer pulleys. I added the same amount of shims to each side, mostly to establish a baseline for behaviour of the transmission once assembled again.
It is apparent from looking at the transmission that the only things that the shims can do is increase (by adding shims) or decrease (by removing) the gap between the two outer clutch pulleys, which similarly increases or decreases the pedal travel before engagement of either clutch. As the cork pads wear, the only way of compensating is to disassemble the transmission to remove a corresponding number of shims. Biasing the shim stack to one side or the other is the only way of moving the pedal neutral position, which is a major design oversight IMHO. If I get tired of pushing the pedal too far forwards and backwards then I might pull it out again and remove the shims on the reverse (sprocket) side to reset the pedal position a bit more forward.
Getting it all together is reasonably easily done by assembling the reverse (sprocket) side first. Put the washer and shims for the sprocket side clutch pulley onto the shaft followed by the pulley and nut, done up only hand tight at this stage. *** GOTCHA WARNING – the clutch pulley used at the sprocket end as to be the one WITHOUT the cut out for the bolt head at the hub, because the one WITH the cut out HAS to go onto the Battery end of the shaft.*** If you get it wrong you have to pull it apart again to swap them around – did that
. Put the drive sprocket back onto the transmission shaft (remember its now a firm but not hard fit) and use that to mount the transmission upright in a vice again. With the interior part of the shaft now sitting up, install the spring and mating inner plate for the reverse side, then yoke bar with bearing, other inner plate, spring, large washer and shims, other clutch pulley (again, the one with the bolt cut out at the hub) and other large nut in sequence onto the shaft. Note that the springs will hold the upper clutch pulley above the height of the thread of the upper large nut, so press the upper clutch pulley down a bit to get the nut started.
It was now necessary to add the thread locker to the large clutch pulley nuts before doing them up snugly. At my workbench it was possible to turn the assembly 90 degrees such that the shaft was horizontal whilst still prevented from rotating. I was then able to compress each clutch pulley enough to reveal the nut shaft thread so I could apply a blob of medium strength thread locker (Loctite 243) before doing up the nut firmly, not hard, no more than 20 ft.lbs I estimate.
With the clutch plate/pulley assembly now bolted together on the shaft, the shaft bearings were then installed, with the inner bearing plates between each shaft bearing and pulley. As mentioned above I did carefully record the distances from inner race to end of shaft, but upon installation it transpired that they simply need to be pushed on as far as they can go. The Greenfield guys apparently got everything sized just so. *** GOTCHA WARNING: The extended inner races of the shaft bearing have different orientations– the battery side has the grub screws towards the battery while the sprocket side has the grub screws away from the sprocket. Not hard to fix but annoying if you get it wrong. *** Leave doing up the grub screws until the transmission has been mounted back in the mower frame.
Installing the sprocket was now a simple matter. Make sure that the second bearing plate for the sprocket end bearing is put in place before the sprocket itself is installed. The nickel anti-seize originally intended for the inner shaft was now used to ensure that the sprocket stayed removable. The chain guard washer and retaining bolt could be installed at this point, but I left them off to facilitate re-installation of the drive chain by the wind-on method.
