Vacuum Engine

Mick has built a number of engines (see list at the end of this article) and has already built a vacuum engine from a plan. The vacuum engine is also known as “Atmospheric Engine” and as a “Flame Eater”.

This engine is different in that it is one of Mick Cherry′s own designs and when you see it running in the youtube video, you will see that it runs very well indeed.

It′s had a lot of running so is looking on the tatty side. The engine has a 1 x 1.500 inch bore and stroke. I did my usual method of making it up as I went along, using the old adage if it looks right it should be OK.

The cylinder and piston are made from stainless steel, this being the only thing I had to buy. I used free cutting stainless for it′s machining and ware qualities, mind you it′s expensive at £40 for two bits. The rest came out of the junk box, bits left over from other projects. I already had the flywheel casting which saved a bit.

All moving parts are running on ball bearings, the water tower is an old Yorkshire fitting with the solder removed.

As far as friction is concerned, you have to make all moving components with good working clearance. All my engines apart from the Anzani have a lapped bore and piston, but made to hold good compression. I did the same with the vacuum engine and it seized up five times, so all I did was to strip it down put the lap through the bore and polish the piston and try again, and after five times I had a runner.

With regard to the timing cam. I turned up four blanks out of aluminium and using a file made up a starting shape, I continued to alter the shape until I got it to run. I then made one of the other blanks to this shape and played about with that. Then from that I shaped a third cam and got it to run as it is now, then I made up a working cam from steel the same as the third cam, a bit long winded but you get there in the end.

For lubrication I use sewing machine oil, I have set the lubricator to give just enough however, at one time when it was getting too much oil it was actually burning it and blowing smoke out of the exhaust pipe, it looked good but gummed up the engine after a while. To the right you will see a very quick sketch of the valve arrangement it works fine, but you have to keep it nice and clean to stop it sticking, I just give it a squirt of WD40 and brush it over with a small paint brush after a few runs.

The burner is mounted on a sliding tray and by moving it back and forward I get quite a good throttle response.

One thing that I was pleased with was that it runs on the Meth′s you can buy from the local DIY shop, nothing fancy like some articles will have you believe.

I still have some trial and error to do on the flame shroud, if I can I would like to be able to run it outside, but as you can imagine the most gentle breeze will blow the flame away.

 

These engines are not cold start. What I do is light the wick, then boil up a kettle, while the kettle is warming up this lets the port face get nice and hot. When the kettle has boiled I pour the water into the water tower, and the engine only takes a few turns to get it running. It will start without all that hassle but it takes ages to get the cylinder up to temperature, so I find this is the best way.

Lastly, a video showing the throttle response.

About Nigel 125 Articles

Have been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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