On Jul 9, 3:55*pm, Robert Neville wrote:
I recently spent some time in Teignmouth and had occasion to take a FGW train
to/from Exeter. I don't know what models FGW uses - the set going to Exeter was
definitely an older 2 car set, the return trip was still two car but much newer.

I thought most modern trains were diesel electric. That is, the diesel ran at
constant speed power an genset, which in turn provided electricity to *drive
electric motors.

What seemed strange to me was that the engineer raised the RPM of the diesel
prior to leaving every station - almost as if he were engaging a clutch. Was the
the diesel directly driving the train?

Smaller multiple units are a form of diesel hydraulic. A fluid
flywheel engages when the throttle is opened. This effectively
provides a clutch up to around 45mph when you will hear a step change
in the revs as direct drive is engaged.

George