Friday 9 October 2015

Gearbox Re-assembly - Part 1

 Reassembly of the gearbox is a work in progress and will be over a couple of posts as it involves both manufacture of special tools as we go and also the progressive manufacture of shims of correct thickness as various components are part assembled, measured and dimension / alignment checked. 
The gearbox is being fitted with a new Ring & Pinion, all new bearings, new seals and new gears as well as a new oil pump plus new selector forks, 

The above two photos are merely a reminder of the assembled and partly assembled innards. The photo directly above illustrates the two gear shafts with the gears removed, the upper being the Pinion shaft and the lower the Layshaft. The back of the gearbox oil pump is on the lower left.

Repairs First

The gearbox has had a bit of hard work during it's racing career and it appears that the Ring and Pinion was changed a couple of times, perhaps once at the track in a hurry as there is some damage to the mounting hole for the Pinion bearing and also the Pinion Bearing Mount was a bit distorted and no longer a tight shrink fit in the mounting hole.

This necessitated Crawford Hall boring out the pinion baring hole oversize by a few thou and also making a new Pinon Bearing Mount to fit the oversize hole and two thou oversize to the new hole so that it is a heat shrink fit. 

Boring out oversize the Pinion bearing hole.

Manufacture of new slightly oversize Pinion Bearing mount. Original on the left and new component on the right in the photo above.

Assembly Begins

The first step (photos above) being to press fitting the new bearings and seal into the bearing carrier for the removable side plate, heating the side plate to fit this assembly and then fitting the (crack tested) drive shaft axle. 

The next step involves doing the same on the other (LH) side of the gearbox case, ie; press fitting in the new bearings and seal into the removable bearing carrier, heat up the gearbox to expand it and fit in the bearing carrier, them install the drive shaft axle for that side.

The next step is the setup of the Pinion height, There is an exact measurement (4.440 inches) from the base of the pinion gear to the centre line of the drive shaft axles. Crawford Hall has made a dummy (identical dimension) bearing that has sufficient clearance to allow the Pinion to be installed & removed while this height is measured and shims made to achieve the correct alignment. The photo above showing the Pinion installed before setting up the measuring jigs. 

To be continued.....