Gearbox Number Three

click on any photo to enlarge
As has already been described below in "The Mystery Gearbox", once the gearbox had been separated before the engine was lifted out, we were slightly surprised to find it was a post war type GB211P, with all straight-cut gear wheels.
By an extraordinary chance Craig found a real pre-war box at the Loftus tram museum (see the link at the top of the page) , and with top cover lifted off, we found as expected, helical teeth on the third speed gear wheels, but not on the clutch shaft or front wheel of the countershaft. Yet we knew such things existed: I have them in my collection of Albion spare parts, brand new if a little rusty on the surface.
All this time we knew that the bare chassis of Albion 1619 was still sitting forlornly in the bush beside the old shed which used to be the depot building of the tram museum. It carried a 6LW Gardner engine and another pre-war gearbox, this time with an undamaged casing. About a year ago it was moved inside into the old depot building, and late in winter 2008 we arranged to meet there and get the box out (after some dramas with keys to the gate outside the shed, due to a truck owner who, given permission to park inside the gated area, proceeded to lock up with his own padlock, not the jointly operable one).


The box from 1619, out in the weather for at least the previous 30 years, yet the gear wheels are in beautiful condition, with only slight rounding off on the leading edge of the second speed wheel, second from the right. Every time a driver selects 2nd to start off, there is a little crunch here.

With much strong arm work the gearbox which must weigh about 100 kg. came out easily enough, despite the bolts having sat and rusted in the weather for ten years. We whipped the top cover off to discover...... straight cut teeth on all gear wheels.
However the case, of prewar design with no external ribbing, is in near perfect condition. All the available top and third gear wheels with helical teeth and a later type counter shaft with a double-instead of single-row rear bearing can now be used in a sound casing. And yet the two cases are not quite identical. This one below, from an unknown bus has a much smaller aperture for access to the clutch finger adjustment.

Just for comparison: the spare gearbox found loose at Loftus some years ago. It contains the precious third speed helical gears. The damage to the clutch housing is pretty bad, but now there is no need for a very expensive weld job. The smooth curves of the two cases make a strong contrast with the heavy ribbing on post-war boxes. The reason for the ribs is not obvious, either.
See the earlier post: "Engine Out".

Showing the very good condition of the case around the top of the mounting ring. During overhauls these probably got damaged by the use of chains for lifting the box in and out.

From the front, the throwout bearing, incorporating the clutch brake. The hub of the friction-lined clutch disc mate with the splines in the centre, allowing the disc to move in and out slightly when disengaging.

The disc closest to the camera spins with the clutch disc, but the throwout bearing remains fixed, only moving fore and aft to operate the clutch release fingers. So if the clutch pedal is depressed hard, the clutch disengages then the throwout bearing (carrying a small friction lining) hits the spinning brake disc and stops the clutch plate dead. This makes it easier to perform an upward gear change quickly, especially on a hill start.
Next step: dismantle this box, and when funds permit, have the case shot blasted to clean it thoroughly. Then the varied collection of gears, shafts and bearings can be assembled to build a gearbox with helical gears on top and third, which will produce a sound none of us has ever heard.

photos David Griffiths