Newest project--A Flyball Governor

[Captain Jerry]

The dash pot that I envisioned is just a small double ended cylinder with a hole in the piston that allows oil or some other fluid to flow between the chambers. The size of the hole controls the damping effect. A simple lathe project.

Jerry

 

[Brian Rupnow]

Finally, in yesterdays mail, the 5/8" brass balls I ordered 2 weeks ago off e-bay showed up. Very nice quality, as good or better than advertised. I am now thinking about buying a digital non contact tachometer, so that I can get some accurate, real time RPM values, to know what difference they will make in the engine speed, once installed.

 

[artrans]

brain about that tach not sure if you no it or not . Go to a hobby shop that sells r/c planes
they have great tachs and cheap and work very well for what you trying to do and they will usually have both types contact and optical and you will pay a lot less then getting it from a supply house.If you do not have a hobby shop near you then hobby lobby or tower hobbies
also carry them and the work very well I have used them over the years and are great.
also merry Xmas and your posts are great and a joy to follow that's a gift in it self thank you art
.

 

[Brian Rupnow]

Thanks for the Christmas wishes Artrans. I lucked out this morning. Went over to Princess Auto Supply (A purely Canadian thing) and picked up a nice Laser tach for less than half price. They are listed at $66 and were on today for $28!!!

 

[Brian Rupnow]

Okay--Here is some good information for people who have been following this thread. At a constant regulator setting of 50 PSI, with 1/2" diameter brass balls, the steam engine ran at a very consistent 500 RPM. When I switched over to 5/8" diameter balls, the engine ran at a consistent 375 RPM. Since the 5/8" balls are heavier, they fly into a "balls out" configuration at a lower RPM. I noticed that when running with the 1/2" balls, the shifter fork that runs from the bottom slider on the stem post over the pivot to the valve link was setting almost level when the engine was running. When I put the heavier balls on, running at the same PSI, the shifter fork is tipped at almost 15 degrees, which of course shuts the air/steam flow into the cylinders down quite considerably. Also, with the larger balls, the governor seems more sensitive to load on the engine, and has more of a tendency to "dither" (oscillate) a bit before it settles into a changed configuration when more load is applied to the engine. This concludes my testing of the flyball governor, although I will probably add more information about its reaction to varying loads when I complete the build of the Varying Load machine.---Brian

 

[mklotz]

Brian,

That's interesting.

The 0.625" ball is 1.95 times heavier than the 0.5" ball. Now, the force needed to hold the balls in a given orbit is proportional to the square of their rotational speed.

If I take the square root of 1.95, I get 1.4. Your speed ratio, 500/375 yields 1.33.

Considering that I've ignored friction, the angle of the arms and a few other nasty real world effects, that's a pretty good corroboration of the laws of physics. Newton would be pleased.

 

[ChooChooMike]

Of course this semi-scientific ball study brings up ALL kinds of jokes/puns/chucklers, but I'll leave those to your imagination :big:

 

[AlanHaisley]

There are 3 ways to change the regulated speed. A weaker spring will let the balls fly out sooner, which will choke off the air/steam supply sooner, thus causing the engine to run slower at its regulated speed. Larger/heavier balls would fly out sooner and accomplish the same result.---Or I could change the pulley to make the stempost on the governor rotate a bit faster. There were ways to vary the spring tension "on the fly" on some full size steam engines, but the mechanics of doIng so are just to complex to recreate in a miniature scale. I will probably just take my side cutters and remove one coil at a time from the spring untill it slows to the regulated speed I want. I don't think a spring elsewhere in the system would have the same effect.

Brian,
I'd think that the easiest flexible way to vary the speed would be with a pair of step pulleys. While this would not allow for on the fly speed setting, it would certainly let you select different speeds for different model loads.
Alan

 

[Brian Rupnow]

Alan---Take a look at Captain Jerrys earlier post in this thread, the one with the attached .pdf file. I have done a bit of experimenting with a rubber band, and it seems that Captain Jerry is correct.--I can modify the speed of the engine "On the fly" by using a spring at some other fulcrum point in the governor linkage train to either offset or add to the compression of the spring on the main stempost. I haven't explored this fully, but with just a rubber band looped around the end of the lever which runs from the moving bottom slider over to the valve linkage, I was able to modify the engine speed by pulling different tensions on the rubber band.---Brian

 

[Brian Rupnow]

I have added the drawings necessary to make this governor as a 3 ball unit to the following thread. 15-jan.-2009
http://www.homemodelenginemachinist.com/index.php?topic=3559.0