New Primary Gearing

The second time is the charm

Recently the primary gear (22A1493) started to make some noise and it has always been slightly non-centric.  Well this was motivation enough to make a second attempt at attaching the gear to the ME0913 motor.

In the original Mini engine, the primary gear spins on the crankshaft and couples the clutch plate to the transfer gears which go to the transmission.  Normally, the gear spins with press-fit bronze bushings which is oil fed through feeder holes in the gear.

With Jane, the primary gear is firmly attached to the electric motors shaft and transfer power to the transfer gears.  The challenge is the Primary gear has an ID of about 1.75" and the ME0913 motor's shaft is 7/8".

A shaft coupler can be used to adapt these two, however, the inside of the Primary Gear is not a consistent diameter but actually 3 different diameters.  These vary by about 0.1" by design (1.5" - 1.62").  The center section has a smaller ID (~1.504") than the outer sections.  Therefore, additional adapters (bushings) must be made to permit a press-fit between the coupler and the gear.  The two new bushings were designed to match the diameter of the inner section (shoulder) so that the coupler will have consistent contact through the length of the gear.  The gear is hardened steel and could not be easily machined.

Here the keyed shaft coupler is shown press fit in bronze-aluminum bushing pressed into the primary gear.

This is the other end of the assembly showing all three elements (Gear, bushing (bronze),  coupler (inner black)).  Note the thickness difference in the bronze bushings (Front vs. rear)

Additionally, a grade-8 bolt was installed through the gear-bushing-coupler to transfer power and hold the assembly together.  With only 40 HP, the Grade-8 bolt should provide sufficient shear strength.  The coupler was cut flush with the front of the primary gear.  The other end of the adapter fits flush with a feature on the motor and is held in place with a bolt through the shaft.

You can also see a new seal (black rubber LUF10005) installed that will keep oil from leaking along the gear.

The first time this assembly was made, the original bushings were turned to accept the coupler but since the gear is difficult to chuck-up in a lathe, it was impossible to machine the inside of the bronze bushings concentric with the outside of the gear.  This resulted in a slight acentricity and it was visible as the gear was turned by the motor.  I suspect this added to the noise coming from the primary gear.  The new custom bushings should be perfectly concentric resulting in a better fit and hopefully reduced noise.

Success

The new gear assembly is in and here is a video of it in motion.  No visible non-concentricity and it is much quieter. Also visible is the good oil circulation for the primary gear train.  

Some photos for higher details.