Gearbox Refurbishment - Part 1

Clutch Problems

The Ruston gearbox fitted to Queen Anne has three gears - slow, medium and fast.  The different gears are in constant mesh, but each ratio has its own friction plate clutch.  Gear selection is achieved by engaging the appropriate clutch via the gear change lever.

 

We have known for some time that slow gear is not very effective - its clutch slips.  There is an adjustment for the spring that applies pressure when the clutch is engaged but while this can make the clutch more effective the resulting pressure is obviously excessive.  The friction plates are riveted to steel disks and it is very likely that the friction material for slow gear has worn down to the rivets.

The replacement of the friction linings is part of normal maintenance for this type of gearbox and is described in the locomotive manual.  Other restoration groups have carried out this work and there are companies who specialize in relining friction plate clutches for heritage vehicles.

The whole gear assembly can be lifted out once the gearbox cover is removed and the assembly stripped down on the bench.

Gearbox Cover Removal

Queen Anne has been kept in the carriage storage shed recently so the first step was to get her moved into the locoshed.

 

Queen Anne being manoeuvred into place

On Road 4 ready to start work

 

The first step is to remove the central floor sections - no problem as they are now secured using stainless steel screws/bolts.  Then the gear change unit must be unbolted from the side of the gearbox.

Central floor removed

Once all the nuts and bolts for the gearbox cover have been removed lifting eyes are screwed into the two positions on the top of the cover.  Because the cover weighs 3 cwt it was decided to use two steel bars and four jacks to lift the cover off.  Since the cover needs to be lifted to at least cab floor level, this required "jacking and packing" using wood blocks.

Jacking system in place

Packed up with wood blocks

Poles inserted underneath the cover

Once the cover had been lifted high enough, poles were rolled underneath and the cover lowered onto them.  The cover could then be slid sideways to sit on the floor at the left-hand side of the cab.

The gearbox mechanism

The above picture shows the gearbox assembly.  From left to right, the main components are :-

• The output gear to the forward/reverse box.
• Bearing.
• The input gear from the drive shaft in the gearbox casing.
• Fast gear clutch operating ring. 
• Medium/Slow gear clutch operating ring.
• Drum containing the clutch plates.
• Gears providing the different ratios.  The lay gear for this can be seen underneath.
• Bearing.
  

As can be seen, the whole assembly simply lifts out.  Further updates will be published as work progresses.