CHUK, the evolution of my vacuum engines.

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Alyn Foundry

Active Member
Jan 27, 2022
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North Wales
My fascination with the Vacuum/Flame gulper engines started about 25 years ago with the acquisition of a Victorian Ernst Planck engine. I was amazed at how simple they were to get running and, dare I say, play with. At the time I was working for Chester UK machine tools as their engineering manager. Several discussions with the MD about doing some castings to go with their range of machines inevitably brought CHUK 1 into existence. CHUK an abbreviation of Chester UK and my Planck engine were melded into CHUK 1 a vertical vacuum engine with a bore of 40 mm and a stroke of 50 mm. Several kits were produced here in North Wales with a view to moving production to the Far East in the not too distant future. Needless to say my own body threw a real wobbler forcing me into shelving the project. After several years of convalescence I had got round to CHUK’s 2&3 ( 2 inverted vertical, 3 a horizontal ) all these engines were using the simple, flat shutter to open and close the flame port. Several CHUK 2’s were produced and built over the years, being an inverted design it was rather simple to build and ran exceedingly well. Only one CHUK 3 was built and it proved almost impossible to run unless the environmental conditions were perfect.

The “ rotary “ valve.

I had built a rotary valve version of a vacuum engine around the time of CHUK’s inception, called ALF, it was water cooled with a little hopper around the cylinder. Although the rotary valve worked well the provision of an exhaust was difficult to achieve, the engine ran rather fitfully. It was shelved too. Many years later I decided to have another look at ALF and managed to get the engine running much better than it had before.

This prompted me to think about the CHUK 3. Turn the cylinder through 90 degrees and place the flame port underneath. A short length of 12 mm diameter Silver Steel was used for the valve. This was then milled with a 5 mm cutter along its centre line. The cylinder was then drilled and reamed to carry the valve and then the 5 mm port was carried through from the outside and into the cylinder. At this point I should mention that all the CHUK’s have an enormous exhaust port, in fact the valve is just a little bit larger than the bore. This ensures total removal of all the spent fluid and makes for perfect running. CHUK 3 Mk 2 ran beautifully with the new valve so this was used in my latest creation, CHUK V .

I must add that CHUK V was greatly helped along with patterns made by Jason Ballamy using CNC equipment. I greatly appreciated his input with both design and patterns.

Currently there’s no video of CHUK V in operation but I’m posting some stills of the whole CHUK Range.

I have spent a lot of time developing these vacuum engines and have amassed a fair amount of knowledge in the process. Feel free to ask for any advice, hints or tips.

Cheers Graham.


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I thought I had seen some video of CHUK V running:confused:

And you have left out CHUK IV, think someone needs a poke to get that one finished.

Chuk did have a few off shoots like this smaller version at 24mm bore.