Aspin Rotary Valve Engine


Live Aspin Number 2

This is the Leyland based 8.6L straight 6 cylinder engine that was used in the Northern Ireland single decker bus and later to generate power and then a saw-mill. Being dismantled in October - December 2002. Thank you Nigel from East Midlands for this gem.
Leyland 8.6L Leyland 8.6L Leyland 8.6L
Leyland 8.6L Leyland 8.6L
After I got the Aspin bits back home, the first task was to get the seized pistons out. Not too difficult I thought, just tug it with a hoist.

Leyland 8.6L Leyland 8.6L Leyland 8.6L
The block was upside-down and the bores were filled with diesel (pause while a week goes bye) the first con rod came out with about half a tonne, but the second rod/piston would not budge. I stressed the hoist to its two tonne maximum and not even a glimmer of movement. Time for the BIG GUYS. I borrowed a two inch diameter steel pole about five foot long (I could scarcely lift it) and I used it as a lever with a fulcrum near the rod and pushed upwards on the other end with a 12 tonne bottle jack. Man, the rod was bending. I guess with the leverage I had, it took near 20 tonnes to draw the con rod and piston out. I looked in for damage, severe seizure, what have you. Nothing. Nothing at all! The bore looked as clean as the others. You will see that I had to strap the engine down to the legs of the hoist quite securely. Five of the rotors will turn now, one is still stuck, the one whose piston came out last, of course. The head is still firmly stuck to the block, it seems so firm that I should believe that it is still bolted down but I can find no further bolts to undo.

Below are some more pictures detailing the head/block to see if anyone who knows these engines can suggest if they can be split. I realise that this head/block is a special and not manufactured by Leyland as a production item, but I bet the design is very similar.
Aspin head Aspin head Aspin head
Aspin head Aspin head

Well, I still have not managed to split the head from block, but I have the rotors out, well, part of them anyway.
Aspin piston Aspin rotors Here is the piston that took around 20 tonnes to pull out
No indication at all for all that trouble
and a selection of the rotors
Aspin rotor Aspin rotor Here are two rotors. This one is in good shape except for some significant burning.
One has obviously suffered from being in an English garden hedge for 15 years
Aspin rotor Aspin rotor Photos taken up the bore, you can see a steel cone inside, this was keyed to the alloy rotors above. I ask WHY? Why have an alloy rotor keyed to a steel cone "shroud". The steel shroud was driven from above, and a simple woodruff key drove the inner alloy cone. If the inner alloy cone was protected by the steel shroud, why the burning?

I will attempt to answer my own question.
I read somewhere, I think in one of the 1940 era publications, that the bus in Northern Ireland from which this engine came, suffered some rotor damage in that the coatings began to lift off. For that reason the bus was withdrawn from service for repair. While the bus was certainly successful in that it performed very well, much better than the existing Leyland diesels, but the complexity and maintenance certainly offset that. What ever the reason, the Northern Ireland bus company did not seek its return. The engine was repaired and powered the Aspin works standby generator for many years. From other sources, I am sure that it powered a saw mill for some years, but why it was replaced I do not know. I mean, that I do not know if it broke or was just replaced. It then became part of a deal to repair a single decker bus, but it was not needed and it passed to me.

If the rotor coating did burn off or became patchy then perhaps the Aspin works repaired it by making conical sleeves to cover the burned and peeling rotors, This would explain the two piece construction. And what happened to the rotors with the wavy oil grooves. I see no wavy oil grooves here. I was sort of expecting to see some kind of sealing grid as well. Nothing apparent as yet, but I have yet to discover how to remove these steel shrouds. The rotors themselves seem to show no signs of the (suggested) lead beryllium mix that they were plated with, to aid bedding down and sealing.
Hummm ... more to come later ....

I have tried repeatedly to free the cylinder head, I have used heat from a large propane burner, and as much force that I can muster. I regret to say that I have not moved it or loosened it one bit, but neither have I broken it (yet).