Posted by: Mike Clark
You are right there is very little lubrication to the drive and differential gear. It is usual to take off the rear axle cover and oil the diff by oilcan at the start of a day's steaming - there is a hole in the diff spider into which oil goes to lubricate the inner ends of the half shafts. There is also a lift-up flap on the top of the engine case which allows you to pour oil onto the crankshaft gear and the eccentrics.
The weakness of the dry engine is poor oiling of the wrist pins (liitle ends) and no amount of squirting of chain grease helps with this. I have put a small brass tank at the front of the engine into which I pour an eggcup full of oil each time I water the car. This is accessed through the front engine cover flap and is connected with 4 pipes which drip oil onto the wrist pins. I also have four more pipes with nipples through which I can inject oil into the main bearings and the eccentrics. Finally, below the engine, clipped to the frame rods is an aluminium tray which catches the dripping oil and channels it back to the crank gear by which it is then thrown all over the links and valve gear and onto the axle gear. It all works really well and the only bits which are out of range are the diff itself, the bigends and the pump link all of which get the oilcan now and again.
Going back to your diff question the drive gear is surprisingly quiet - just about detectable when driving and better than many normal old cars. It does not seem to wear - my gears are induction hardened EN24 and I set it up with backlash between teeth of about 5-6 thou. You can only do this if the gears run true and are not eccentric. It is important to get the perch rods and diagonal braces square on as they can pull the engine out of line (by bending the axle!) and cause noise in the gears.
Stanley used unusually large sun wheels on their halfshafts - this is because any gear needs a few thou clearance and the large sun wheels cause less magnification of this clearance by the time the motion gets out to the o/d of the tyre. If everything is right there is no more than 1/2inch backlash at the tyre o/d.
There is naturally more clatter when the wheel is jacked up to pump and runs with no load but it is no worse on a dry engine than a wet one. The effect of bad adjustment is far greater