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Nigel (egi)10/09/2018 20:04:06
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I'm building a steam engine that has been converted to run on petrol. What I'm not sure about is how well it will run using eccentric cam drives?

Has anybody tried this before?

More details and images are here: **LINK**

JasonB11/09/2018 07:17:22
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If 4-stroke then it is possible to use a "steam" engine type eccentric but you need a way to half the amount of times the eccentric moves as you only want the exhaust to open every other rev of the crankshaft. A "Star Wheel" is one method that was used on the early engines, an epicyclic gear box inside the eccentric strap is another. Or you simply need to add 2:1 gearing to drive the exhaust valve and a lobed cam.

The inlet valve is easiest dealt with as an atmospheric one where it is held closed by a light spring and the suction of the moving piston on the induction stroke will pull it open drawing the fuel/air mix with it, again found on most open crank engines so typical of this type of engine.

Star Wheel in action on an Sphinx

Epicyclic gearbox on my Robinson X-type
Inside the gearbox ( made on an x series mill)
Ian S C11/09/2018 13:22:05
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I remember something in ME in the 1990s I think of some(maybe Tubal Cain) built an IC motor using a horizontal Stuart Turner steam engine.

I wonder if it would be possible to make it double acting, I know there would be the problem of sealing the piston rod gland.

Ian S C

Nigel (egi)11/09/2018 20:43:41
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The eccentric will result in a sinusoidal motion and simple comparison to a cam profile shows it is close. I will see if I can do a full comparison.

I have made a 2:1 reduction drive to the camshaft, early picture below:

Gears were cut using an Amadeal XJ12 mill and Warco HV4 rotary table

 

Edited By JasonB on 12/09/2018 15:25:14

Brian Oldford11/09/2018 20:53:36
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Posted by Ian S C on 11/09/2018 13:22:05:

I wonder if it would be possible to make it double acting, I know there would be the problem of sealing the piston rod gland.

Ian S C

It would also make for an odd-ball shaped combustion chamber too.

JasonB11/09/2018 21:00:08
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The Mery is a double acting engine and a bit of a half breed being built early on in the evolution of IC engines, and not too odd looking.

JasonB12/09/2018 07:49:06
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Posted by Nigel on 11/09/2018 20:43:41:

The eccentric will result in a sinusoidal motion and simple comparison to a cam profile shows it is close. I will see if I can do a full comparison.

Simply leave a large tappet gap between rocker arm and valve stem, this will make part of your sinusoidal motion zero where there is a gap and then a peak where the rocker and valve are in contact. It won't give the quick opening and closing times of a lobed valve but will work. I would still make the intake an atmospheric one as then that will open and snap shut faster.

Edited By JasonB on 12/09/2018 07:49:29

Gary Wooding12/09/2018 08:23:33
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Jason's post of 11/09/2018 07:17:22 appears to be a response to an earlier post which doesn't show in my system. It's the first one in this thread - what's happened to the others?

Brian H12/09/2018 08:28:00
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Jason, thanks for putting on the video on the 1895 Mery Explosive Engine. I've never seen a double acting ignition engine before.

Brian

JasonB12/09/2018 11:00:49
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Gary, there is some moderating going on.

Ian S C12/09/2018 15:23:46
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I was doing some reading today on converting a double acting steam engine to IC, the front side of the piston being used as a compressor to supply cooling air for the cylinder.

Ian S C

Nigel (egi)12/09/2018 20:42:05
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I like the idea of the tappet gap, trouble is my current head design is for a sliding valve, with an air-cooled head and cylinder - I might have to change this and make this more "steam-enginish" (happy if you can moderate this to a real phrase!).

I'll add some images of the current head and cylinder design.

Nigel (egi)15/09/2018 21:06:08
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22 forum posts
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An image of the current engine, shows the air cooled cylinder and head, intention is to have sliding intake and exhaust, but based on the exchanges in this forum I might make a different cylinder, head and intake/exhaust system

transitional-001.jpg

a second image of the engine at a slightly different angle so that you can start to get a feel for it

transitional-002.jpg

I will post some more images as I start to change the design.

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