What size to make the Flywheel.

[allen56am]

I am new here, I hope I am asking this question in the correct place ? I am in the process of building my first Flame Licker Engine, I am using a 20cc weed wacker engine and modifying it to have a open crankcase and a walking beam on the top to operate the slide valve I am making for the cylinder head, My question is how do you figure out what size and weight to make the flywheel, I have decided to use just one flywheel.
Thank you.

 

[Blogwitch]

I have the plans for some of Gerd Litty flame lickers, and they have bores of between 2.125" and 2.5".

The flywheels are between 9" and 12" with very heavy outer rims.

The reason for this size and weight is to carry over the single vacuum power stroke onto the next power stroke.

I don't know what size bore your engine is, but from the figures I have quoted above should be able to get you in the right ball park.

So if you bore is say 1", then you should be able to use an outside weighted flywheel of say 4.5 to 5" diameter.

BTW, the largest engine that I have plans for uses two 12" flywheels that weigh maybe 15 - 20lbs, I think he used so much inertia because it has a water pump for the cooling of the unit so that requires a lot of power (in vacuum motor terms) to keep it running.

John

 

[kvom]

My theory is that the larger and heavier the better.

 

[allen56am]

Thank you so much for your time and information, By the way, My piston is a metric size just bigger than 15/16" Now I am wondering what happens if the Flywheel diameter is to big or to heavy ?

 

[Blogwitch]

What will happen is that there is not enough energy in the vacuum power stroke to keep the flywheel turning, it will gradually slow down until it can't turn over any more.

All you would need to do is skim some material off the diameter until things balance out.

Vacuum engines are nothing like i/c engines, they have very little power and even a small deficiency or inefficiency in one area can stop things working at all, but once you find that balance, they will run until the fuel runs out.

John

 

[allen56am]

Ok, John that totally makes sense to me, So it sounds to me like it is best to go kinda big on the wheels that it is to start out to small, Sounds to me like I should go big within reason and have very thick outers so you can cut them back to get it (Just Right) Thank you John.