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[kiwimodeller]

Greetings all, I am in the process of building a twin cylinder oscillator by coupling together two single cylinder engines (where have I heard of that before?) but this will be an in line twin. They are 1/2" bore by 3/4" stroke and double acting so it should be reasonably powerful and self starting. Initially I will test it in my paddler which gets used for all my experiments but eventually it may go in to another paddler or a prop driven boat. My question is whether, on a double acting engine like this, I might be able to get away with not running a flywheel as this would make the engine easier to build and also allow me to take the chain drive for the paddler off the centre. Has anyone tried running without a flywheel? Thanks, Ian.

[SteamboatPhil]

I don't think it will work Ian, however you could go for a balanced crankshaft which I have done in a couple of my high speed engines. 

[gondolier88]

No is the simple answer- many launch engines were made without a flywheel- using the flywheel effect of the prop- however these were usually 180deg crankshafts and high speed engines that were for speed not useability.

Saying that- if you propose using it for a paddler- i've never seen a paddle engine with a flywheel- the paddles should do it for you.

Greg

[Bunkerbarge]

A flywheel is basically a storage of energy and, particularly in the case of a single cylinder single acting engine, it is essential to give back some energy to the engine to rotate it through the exhaust stroke and bring the engine round to the next inlet stroke.

In multi cylinder double acting engines though it still performs a valuable function in so far as it smooths out the torsional oscillations of the power delivery.  Your engine might run but it may well be very lumpy and generate quite a lot of vibration in the boat.

[derekwarner]

mmmmmmmm both the French JMC & Anton + the OZ Steam Models use a fly wheel in their respective horizontal engine models & most manufacturer's of vertical model steam engines also install a fly wheel....however most manufacturers of full size steam engines did not use a fly wheel  

A most respected member of Paddleducks [Sandy Campbell] years back advised that a fly wheel was technically not needed, however would balance out certain rotational forces & hence provided an harmonic effect

Before computer games....40 years ago we had string pulled gyroscopes that would gently rotate on their multi axis plane  & how difficult was it to alter the rotational axis or position of this rotating monster

Possibly a chopper [helocopotor] sky pilot member could offer comment here....Derek

[Colin Bishop]

i've never seen a paddle engine with a flywheel- the paddles should do it for you.

The inertia might work on a full size ship - not so sure about a model though as the viscosity of the water doesn't scale down.

Colin

[tobyker]

I was test running my little ST DA V-twin (see other thread for latest news this pm) without a flywheel and it seemed to work surprisingly well - but it was smoother and faster with one.

[gondolier88]

The inertia might work on a full size ship - not so sure about a model though as the viscosity of the water doesn't scale down.

Colin

Yes your quite right 'you can't scale nature'- however if the viscosity is enough to stop it dead in the first place, I doubt any effect a small flywheel on the crankshaft would have in  overcoming that.

Greg