Single Sleeve Valve 'diesel' Engine

hello again chaps,

I have been working on this one on cad for the last couple of months.
It all revolves around a stihl fs 66 piston and rings.
It is a Four Stroke Single Sleeve Valve 'diesel' Engine. It isn't a true diesel, but it is ignition compression.
the bore is 31 mm or 1.220' inch and the stroke is 26 mm or 1.024'inch yielding a 19.6cc capacity with a 1.192: 1 bore to stroke ratio.

My plan is for it to run on petrol or naphtha etc, by the use of a contra piston, thereby being able to change the compression ratio, like the 'diesel' model airplane engines that run on ether. Being a sleeve valve engine there is conveniently lots of space in the 'junk head' for the contra piston and lots of turbulence in the combustion chamber, decreasing the burn time, so the gases can expand the 'full length' of the power stroke. Also you can optimise the combustion chamber shape. Anyway, enough talk, here are some screenshots.


Greg

 

I would not make it a "diesel". The contra piston needs to be a very snug fit in the cylinder liner. That's fine in a stationary liner, but the sleeve needs to move freely in a sleeve valve engine. Below is a diagram from Sir Harry Ricardo's book, "The High Speed Internal Combustion Engine" that shows how to layout a sleeve valve for an engine with a shared port. This is the design all the aircraft sleeve valve engines used because it groups the intakes and exhausts together. It is possible to use all individual ports. That results in alternating intake and exhaust ports. However, that layout provides the maximum port area for a high speed engine.

I hope this helps. Good luck with your project. I love sleeve valves. It's too bad they were just beginning to be used in aircraft engines before advanced piston engines were eclipsed by the gas turbine. I've also posted two articles on sleeve valve engines.

Lohring Miller

 

Here is some more views and diagrams for those who are interested in my project. Hopefully I can get these cast by the end of the year.

 

That gives me a better idea of what you are proposing. I've worked with a lot of two stroke cylinders in this size range and still feel that you will not be able to seal the cylinder well enough to get compression ignition. I'm not aware of any production model compression ignition or glow ignition engines as large as yours. I've also tested similar size engines converted to glow ignition running nitro/methanol/oil mixtures. A spark ignition system taken from one of these small engines is a more reliable solution on both gasoline and methanol fuels. Davis Diesel has done more work with compression ignition engines than any other recent company. They may be some help.

Lohring Miller

 

There are two larger compression ignition engines that I am aware of, the Lohmann bicycle engine and this recent engine that was to run a water pump in developing countries.
Thanks
Greg

 

here is the timing diagram (half speed) runs clockwise.
Blue is intake. Red is exhaust.
the intake port opens
0 degrees TDC and has 190.6 degrees duration (crank speed)
the exhaust port opens
0 degrees BDC 190.6 degrees duration (crank speed)
the ports have a 21.2 degrees overlap (crank speed)




the second image shows the port shapes at TDC during the overlap of the exhaust and the intake valve
the red port is the exhaust port that is stationary
the blue port is the intake port that is stationary
the dark blue and red are the portions of the valves that are open
the grey port is the revolving port that is cut into the sleeve

let me know what you think

Thanks
Greg

 

That's very interesting. What fuel do they run on? I'll think about your port layout when I have some more time.

Lohring Miller

 

the lohman bicycle engine ran on 87 octane petrol.
the water pump runs using kerosene

 

I was disappointed to find out the Practica pump engine never worked well and they gave up on it. I followed that project when they were developing it and wrote to them about status quite a few years ago now. Compression ignition with variable load works OK in model sizes, but I've found as size increases beyond 10cc it becomes critical or settings and temperatures. It's also the reason why we still don't have HCCI powered cars. The Lohman also ran kerosene, not gasoline. I like sleeve valves as well, and have a design I'll be building soon.

Clearly there is some Dekker Barr & Stroud in there. Your port layout is unique. I'll be following along.

 

Well spotted I was inspired by the Barr and Stroud sleeve valve engines!

well there is more to come soon!

 

Model engines run on an ether, kerosene, and oil mix at close to equal parts of each. If you run a cast iron piston on a steel liner, caster oil should be the oil. Synthetic oils could probably be used with rings, but castor oil gives extra protection. The oil is used as much to improve the seal as to provide lubrication. Even on ringed 26 cc two stroke engines, we found that double the manufacturer's recommended oil mix improved power. An ignition improver like octyl-nitrate (Amsoil's ACB) can also be added. This thread discussed the subject. Again, I've never heard of a successful compression ignition engine this large. However, conversion to ignition should be easy. Model four strokes run on an oil/fuel mix like two strokes. In your engine I believe that would still be the simple way to ensure good lubrication everywhere.

Four stroke power is limited by breathing. I noticed that the company that was building the 28 cc sleeve valve engine is now using a 28 cc two stroke in their UAV. The two stroke probably has close to twice the power at much less weight. Your porting is quite conservative and will limit power and rpm. The three intake, two exhaust configuration with one shared port gives a good compromise. It groups functions together giving simpler manifolds. That's the layout I shared. The best breathing comes from sharing all ports. That gives alternating intake and exhaust ports with interesting manifold configurations. Look carefully at the port layout. It gives a very large amount of timing and lay out information as a starting point for your sleeve valve engine. The last edition of Strictly IC has a build of the Barr and Stroud sleeve valve engine. See the last entry on the article page.

Lohring Miller

 

Hi
I own and have run a number of 2 cycle model diesel engines.
I wish you luck building a sleeve valve diesel.
I don't think you will get the compression needed in a sleeve valve engine
Here is a short vid showing a glow engine I own,
It is stuck with castor oil and I did not want to take it apart to show the features,

 

thanks Lohring,
A year or so ago I decided if I could run my mills .75 diesel on a mixture of 40% castor oil, and 90 octane petrol, and I was amazed that it started relatively easy!
So the key is to have a good seal, and I was thinking of using 40w 70w oil in the crankcase to help in achieving that and having drip oil feeders drip thin oil on the sleeve to lubricate it.

I have felt that my port layout and timing wasn't the best. just i don't know really what the max rpms are going to be like, my estimate was about 8000. looking back now the port timing looks pretty awful! and i don't know how I came up with them!

I have studied the barr and Stroud engines and I have a pdf of a booklet that shows many cross-section views and diagrams.
and I am going to have another crack at the layout and timing.

Thank you dkwflight
for taking the time to make a video and showing me your rather interesting Hp motor, But I am afraid to say that your engine is actually a rotary valve motor. I just did a quick internet search to verify my suspicions. here is the link
http://www.mecoa.com/hp/vt/21.htm
but I really appreciate the time that you have taken to explain your opinion.

 

Hi, don't wish to put a damper on things either, but I have made a sleeve valve glow engine which won't start, not surprising really as there's damn all compression, and that's with me doubling the number of piston rings from the plans and making them bigger. I'm still working on it when I have the time and inclination, between doing other stuff, and the lack of compression is baffling me.

So I have to join the others when I say that I very much doubt a compression ignition sleeve valve will work being built in a home workshop. Sorry if that sounds negative but I'm just trying to be a realist. However, I'm watching this thread and will follow with interest your build and wish you all the best of luck.

Chris

 

This topic in a German forum describes a successful sleeve valve build. It's smaller than your engine and spark ignition. The builder is an excellent craftsman and the posts are very detailed. He has a good description of the design details as well. Google translate will get a workout if you don't speak German.

Lohring Miller

 

Hi Lohring, yes I have seen this article before too - well worth looking at Greg and if your German is as good as mine worth all the hassle of using Google Translate to read the text! It is an excellent build, very high standard of workmanship, and a very well engineered design. A beautiful engine.

Chris

 

He has made a few posts here https://www.homemodelenginemachinist.com/threads/hallo-from-germany.8961/
The build thread was on madmodder. https://madmodder.net/index.php?topic=2456.0

 

The madmodder thread was really interesting - thanks dieselpilot!

 

Thank you, everybody, for expressing your concerns, for I have taken everything said into consideration and I am going to 'shelf' this idea.
I am currently contemplating building a compression ignition engine that has proven to work,
a modifyed ETW Kiwi that is on Ron's website: http://www.modelenginenews.org/gallery/p8.html
along with the plans for the modified cylinder head: http://modelenginenews.altervista.org/mecd/3287.img.html#888
R.I.P may your legacy live on.

well it certainly has in me (being 15 years of age)
I try to drag all of my friends into this hobby, for instance, I have helped them on my lathe at last year's summer holidays to make a steel spinning top and they really enjoyed it.

anyway as always just let me think of this new idea.

oh By the way, water cooled, or air cooled?
the crankcase reminds me of my British Seagull outboard motors! (I have 2 a 1952 102 and a 1978 silver century plus)

Thanks for your time and comments everybody!
Greg

 

thank you, Chris.
To be honest, I am a bit of a realist myself.
Just have a look at my signature!

Also, I would like to suggest try starting running it with some oil in the fuel (I use 10:1 and I have used 5:1 ) and it get it running in, I had similar problems with my Webster.
or if that fails, take the spark plug out and turn it over with a drill for half an hour (with some oil dripping in) and then give it a light hone and try to start it again.