Wobbler Steam or Air Engine

[jjr2001]

There are a lot plans on the net for these little wobbler engines.
Easy to make and only a few parts. The base is steel and the flywheel is steel.
The rest is brass.


Cheers, JR

[mklotz]

Very nicely done, JR. As you probably know, the wobbler is the engine form most often recommended for folks who are starting out in the engine building hobby. That said, the basic engine design can be elaborated considerably. Here's a picture of one I built from a Verburg design that is both double-acting and reversible...

The wobbler is simple and dependable. They can be surprisingly powerful given their simplistic valving design. Plans for multi-cylinder versions exist where one cylinder won't do the job.

Folks looking for model engine plans should be aware of the John-Toms site...

John-Tom Engine Plans

where they will find plans for Elmer Verburg's engines, a staple of the model engine building folks...

Elmers Engines Steam Engine Plans

[jjr2001]

Man, you have a lot of engines Marv. I like the Scotch yoke and will have to build your horizontal version
to go with my vertical mode.
I liked them all but this one may be a good match for my vertical:

STANDBY.jpg Photo by mklotz | Photobucket

I have been to john-toms and have several projects planned from there. That is the super source for old engine plans.

Thanks for the links,
Cheers, JR

[mklotz]

Interesting that your attention is drawn to Standby. It, a Verburg design, was the first engine I completed, though not the first I started.

In a fit of bravado, I had optimistically started my engine building career with Rudy Kouhopt's two cylinder vertical marine engine. I was working then and only got to work on it sporadically. Every time I went back to it I would pick up a piece, mutter "I can do better than that", and start remakiing it. There are parts in that engine that have been made five or six times. As you might expect, very little progress was made.

One day my wife saw the box of parts and commented, "If you're having trouble finishing it, maybe you should build something simpler.. That will motivate you to finish it." I took her advice, built Standby, got a huge rush the first time it ran, and the rest is history. My collection today numbers over three dozen engines, steam, Stirling and atmospheric, as well as machine tool models and artillery.

Eventually Rudy's engine turned out pretty well...

It taught me a lot - fabricating crankshafts, how D-valves work. and eccentric fabrication.

[jjr2001]

Now that is another good one! Two cylinders and vertical orientation.
The best part of these model engines is that you learn how the valving works.
I always admired steam locomotives and wondered just how the valving worked and now
I am getting a little bit of how they work. They are so much more interesting than diesel electric.

Cheers, JR

[mklotz]

Most steam locomotives had D or piston valves.

If you have a piston valve, the cylinder must be outfitted with blowdown valves. Condensation after engine shutdown can lead to water in the cylinder. If you attempt to start the engine this can lead to a hydraulic load on the piston and the valve. In the worst case something bends or breaks. Opening the blowdown valves at startup provides an escape route for water. You can see the blowdown valves in this three poster...

On the other hand, in the D valve the 'D' piece is free-floating on the rod that pushes it back and forth. Condensed water forced backward at startup will simply lift the 'D' and the water will have a clear path to the exhaust stream. You'll notice that the marine engine has no blowdowns which indicates that it has D valves, as indeed it does.

Another tidbit that making the marine engine taught me...

If a single cylinder steam engine stops at exactly TDC or BDC it has no lever arm to turn itself over on startup. This means it would have to be hand cranked into a starting position. When the engine is down in the bilges somewhere, that's neither an easy or appealing thing to do.

The marine engine has its two cranks out of phase by 90 degrees. No matter where it stops at least one of the cylinders will have leverage to restart the engine; all that's needed is to apply steam.

The rope drive engine has offset cranks for a similar reason. Hand cranking a big engine isn't an easy job. In fact, some of the early single cylinder engines had separate small "barring" engines that were used to turn over the big engine. A gear on the little engine engaged, via a clutch, gear teeth on the periphery of the big engine's flywheel. Once the big engine got going the small engine was disengaged.