Does a Steam Engine need a flywheel?

[kiwimodeller]

Greetings, I am building an engine for my next paddler project by coupling together two single cylinder double acting oscillators with 1/2" bore and 3/4" stroke. This should make a reasonably powerful engine and as it is double acting there should be no worries about it being self starting. With (in effect) four power strokes I am wondering if I can get away without fitting a flywheel as this would allow the engine to be more compact. Has anybody tried running an engine with no flywheel? Are the paddle wheels enough of a rotating mass? All opinions welcome. Cheers, Ian.

[Eddy Matthews]

I'm certainly no expert Ian, but my Marten Howes and Baylis paddle engine didn't have a flywheel, and it ran perfectly even without the paddlewheels acting as a flywheel!

http://www.paddleducks.co.uk/smf/index.php?topic=1445.msg4845#msg4845

Regards
Eddy

[Hankwilliams]

Hi, Ian,

I`ve built several steam driven paddlers and also some screw steamers and I generelly can say: a flywheel is not necessery for a paddler engine with two double acting cylinders.
Even with a gear reduction from 1 : 2 to 1 : 5, a flywheel you must not installate,  the weight of the paddlewheels is sufficient for the smooth motion of the engine.

Even a  engine for a screw steamer in many cases doesn`t need a flywheel, it depends in the weight of the screw and also in the precision of the engine. Generally for simple and cheep engines like Wilesco a flywheel is better for smooth running,  but the precision engines like Marten& Hoves, Anton etc. doesn´t need it.

Thomas

[kvom]

It might be useful for breaking in on the bench.

[monarch]

In short-no you don't.  The thrust of the water against the paddle wheels is generally enough to overcome dead centres and flywheels have to be perfectly balanced in order to have any effect.  Leave it off-you'll be happier!

[derekwarner_decoy]

mmmmmmmm not sure PD's.......

Anton + JMC + Monahan all use flywheels...so why?  ...well I asked Sandy Campbell & his response was similar to the following

Technically not needed BUT considering we are turning a rotary motion into a linear motion & force....we accelerate to top DC STOP..change direction to bottom DC then repeat the exercise again & again & again

It consumes power to accelerate the flywheel.......it consumes power to maintain the speed of the flywheel

Sandy suggested that the extra mass of the flywheel was an investment in greatly improved mechanical harmonics of the engine.....we cannot measure this with a multi meter....however todays condition monitoring technicians & engineers with their fancy computer driven software & mega $ vibration sensors would be able to plot out chart recordings which confirmed that the steam engine with the flywheel provided far greater harmony ............Derek 

[kiwimodeller]

Thanks for all the feedback guys, it will certainly make life easier if I can couple the two engines up together "face to face" and not have to find a way of making room for the flywheel. Cheers, Ian.

[philbutton]

I have built several steam engines in various sizes and found that none of them needed a flywheel to operate satisfactorily. Engines concerned were:

Twin cylinder double acting in-line oscillator (10mm bore x 10mm stroke)
Vee twin double acting slide valve compound (14.5/21mm bore x 16mm stroke)
In-line twin double acting slide valve compound (14.5/21mm bore x 16mm stroke)
E T Westbury double diagonal paddle engine (3/4" bore x 1.5" stroke)

The only time I have found a flywheel useful was during construction when I wanted to run only one cylinder at a time for testing. To do this, I have an old flywheel and make up an adapter to fit it as needed to the engine.