Just found an interesting model paddler on youtube. It is listed as "paddle steamer at bushy park" and placed by richard barnett. It is a lovely model of PS UNICORN an early trans atlatic paddler operated by Cunard. What is more interesting the drive train is all LEGO and works extremely well!!! Regards, Walter.

furtter to the above. Apparently there is no model boat club at  Bushy park,  but a group of modellers sail there on a Sunday on an informal basis. This is maddening- I wont sleep tonight! The lego set-up is brilliant, only I cant work it out as a dfferential? seems to drive a second shaft and a chain drive I assume to drive the two beam engine arms which looks superb on the water. Pleese if any one from the bushy area who may know the builder put me in touch through paddleducks PLEASE or I will spit my dummy out and pour my cocoa all over the cat!. Regards walter.

A very nice model.

Hello Walter,

After looking for a while at the Lego mechanism it seems to me that it is a "superimposition gear" arrangement. Kind of difficult to explain, but I found a lot of images on Google.
Basically (I think) the main motor is to the right (not visible) and moves the chain. The small motor seen below in the middle must be the one that provides the superimposed movement.
When the small motor is stopped both shafts move at the same speed as provided by the main motor. When the small motor moves left or right it turns the differential cage and "superposes" a second movement which makes one shaft turn slower and the other shaft turn faster.
This is used in track vehicles like tanks or bulldozers and also on some clamshell excavators to syncronize the drums of the hoisting and opening ropes.

Not 100% sure, but I think that's where to look for.
Hope it helps to let you sleep again. 

Regards Jurgen

Thanks Jurgen. I love the clean lines of that drive but as I still live in the dark ages it is too much for me to take in!. I am still hoping to hear from someone who knows the builder of the model!!!! regards, walter.

Hello Walter,

I've sent you a message about the builder.

Tony

Thanks Tony, I will follow that link up. I am not very keen on computers hence my delay in messge reading! Regards, Walter.