A question of lubrication

Letters to the editor

I have been, over the last few weeks, working on a rather rare de Normanville Safety Gearbox fitted to a 1930s Humber Snipe Pullman. Needless to say, it is the first one I have seen. If you are not familiar, this is an epicyclic gearbox, all gears contained on a central rotor with engagement controlled by pressurised oil through a piston block, brake shoes and control rods. It came in with no second gear, the fault being traced to a newly manufactured part being fabricated incorrectly and breaking. This has been repaired and the whole thing is reassembled and back in the car.

Now to the lubrication question: the workshop manual calls for Castrol H and states that 'thin' engine oil can be used temporarily but should be immediately drained out when the correct lubricant is available. Other than a gear-set that is much the same as the Laycock-de Normanville overdrive the only other related factor is, I think, that the seals in the piston block are leather. I have been unable to find any information online about Castrol H so what I am asking is: what would you use?

The photo shows the gearbox from below with the sump, oil pump and filter removed. The piston block runs down the left side, the fourth-speed piston down the right, and you can make out the rotor, brake shoes and control rods running down the centre (with the pump having been mounted on the long studs at the top).

Thanks,

Chris McPheat

Publiziert:

Freitag September 16th, 2022

Leo van Stirum

19 September 2022, 17:16

"light engine oil" corresponds roughly with modern 20 to 30 SAE rating, a modern ATF (Dexron II or III) is about the same but is full of detergents which might attack the leather seals.
Another option might be a 5 or10W30 for motorcycles with a wet clutch, but still the future will tell if the leather seals will hold up...
You could off course submerge a piece of leather in the chosen oil type for a couple of days/weeks and see what happens.
Good luck !

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David Scott

18 September 2022, 06:57

Well if it were I, the leather seals would have been replaced whilst undertaking this quite comprehensive overhaul, as they are bound to be trouble in future. Had I replaced the seals, I should have used ATF? I would have replaced the rubbers in the mounting too?

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Peter Caunt.

18 September 2022, 00:06

Most popular preselector gearboxes such as Armstrong Siddeley or ENV used to use Castrol PSGE which is no longer available. Alternate oils were "straight" SAE 30 or 40 oils but no multigrades - which allow the bands to slip rather than grip the drums.

I would imagine that SAE 30 would be OK but the other PS boxes do not have leather seals so can't comment on how this would effect SAE 30 - or 40.

My experience of PS boxes is from ownership AS Sapphires and Crossley Regis with driving experience on Daimlers and Lanchesters with fluid flywheels rather than the Newton centrifugal clutches of AS and Crossley. Good Luck.

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A question of lubrication

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