I started in the workshops of a transport company in Mansfield in 1962 and the main vehicles were Scammell Highwaymen, with a few AEC Mercurys and for some reason just one Commer 2stroke tractor unit. This vehicle stood out from the others by the sound it made and as I remember it was rather prone to brake failure but I remember the drivers saying it had plenty of power. I saw the engine when it was stripped down for a rebuild and it seemed a very unusual set up as I remember it was a 6 cylinder with 12 pistons with the combustion taking place between between the two pistons in each cylinder. An other thing I remember about it were the two big silencers under the front bumper. If I'm wrong on any of these details I'm sure someone will correct me, after all its 50+ years ago that I last saw the Commer.
P/S, I'm glad some of you liked my 2 photos of the Scammell Scarabs, I can recall seeing one in the 1950s with an all wooden cab that must have been a very old one.

Don't know what engine that was that you saw but if you cut the number of cylinders and pistons by half that would be a TS3. They had 3 cylinders and 6 pistons which were horizontally opposed, the con rods were connected to the crank shaft by means of rocker arms. I did post a picture of one some time back with the side covers off and it gives you good view of all the bits and pieces.

Hello coachman, thinking about it I think you're right, I knew there was a 6 in it somewhere it was 6 pistons and 3 cylinders, as for the rocker arms I seem to recall they were very hefty about the most solid bit in the engine.

An animation here.
 

Thanks G-CPTN, very interesting reading, the rockers are exactly as I remember them, I'd love to hear one running again.

[QUOTE=pbowler;14328]Thanks G-CPTN, very interesting reading, the rockers are exactly as I remember them, I'd love to hear one running again.[/QUO

It was not unknown for the nuts that secured the rocker arms to work lose but it never seems to cause any damage if it was rectified in time, all I remember doing is re-torqueing them and off they went back on the road again. I was only just 21 when I first got to work on them and used to love the job of taking them back to their home depot on night shifts after they had been serviced during the day. If the driver had reported that the blower pressure was high then it would have had the manifolds off for a de-coke, this meant that when it warmed up you got a firework display out of the exhaust as the rubbish blew out of the engine.

Commer TS3
 

A couple of years ago I was at a place in Manchester looking for some spares at this dealer's place (he deals in obsolete spares) and lo & behold there was only a TS3 engine complete in a cut down Commer chassis frame waiting for someone to buy it and presumably out on display possibly in a transport museum!

This guy as far as I know still has a set of pistons in stock for a TS3!