Flywheel weight

[Bruce R.]

Got a case of cabin fever so I’m in the middle of building my third Deppenbusch engine. I’ve scaled it up slightly and decided to go with heavier flywheels, I’m thinking this would make the engine coast longer between hits and run slower. Anyone out there have any thoughts on this ?

 

[TonyM]

For full scale engines heavier flywheels or even adding a second flywheel was used as a means of reducing the surges especially for generator sets so the hit and miss effect is reduced. In small scale the effects you desire may be more achievable, certainly slower running.

 

[Bruce R.]

The slower the better, I’m thinking that I should’ve gone with a longer stroke as well but I’m too far along with it now.

 

[Brian Rupnow]

Flywheel weight is one of those "Try it and see" situations. Yes, for a given impulse by the piston, the flywheel should revolve a bit longer with heavier flywheels. However, you have to take mass and inertia into consideration. If the flywheel is heavier, it has more inclination to stay "at rest". That means that with the weight increased but the piston giving the same "push" as it did with the lighter flywheels, the heavier flywheel won't revolve as fast as it did with lighter flywheels. It might rotate longer before the engine "hits" again, or since the starting rpm from the piston will be a bit less due to the heavier flywheel weight, it may not. I already tried this heavier flywheel thing with my Kerzel hit and miss engine, and it didn't work out very well.

 

[Rustkolector]

In my experience replacing a flywheel with a heavier flywheel of the same diameter yields only small operation improvement. However, changing to a larger diameter flywheel usually does improve running. The most effective mass of a flywheel is at the rim. Foos, Otto, Nash, etc. electric lighting engines used very large diameter, but not overly heavy flywheels.
Jeff

 

[Bruce R.]

Did a little more

 

[awake]

Looking good! Is this your own design, or ??

 

[Bruce R.]

Deppenbusch, I just stray a little from the prints

 

[awake]

A bit of searching turned up this link - looks like the book is still available:

http://www.angelfire.com/ks2/modelengines/

 

[Bruce R.]

Yes, I got mine back in the 90’s I think it’s still in print.