Cylinder Sleeve Design

[Fidlstyks]

The head holding the sleeve in would be the best. Nothing would be more secure than a small ridge at the top to keep in place.
The head would not let it go up and the ridge prevent it from spitting out.

The relief prevents or insures there would be no crush effect.

Relief as a groove in a steel sleeve would be fine.
As Jason pointed out, the entire cylinder made of steel is a good idea.
Pinning a 2 cycle sleeve would be important.
One must consider materials when fitting parts with different expansion rates too.

 

[Kosiba]

Pins are also used on a ported liner to stop it rotating, if it did then the ports could become blocked or at least reduced in area . It also saves people putting the liner back in the wrong way round!

Steel is quite common for the liner or even the complete cylinder on model aero engines, you can turn it thin and it will be less prone to damage than a cast iron one where a thin fin could easily be broken. It also means you don't have similar metals runing against each other. As the engines get bigger you may find cast iron liners are more common as they can be cast hollow so less waste and quicker to machine.

To some extent materials will also depend on what the intended use of the engine is going to be. If it will just get the occasional run for display with no load then you may design differently to an out and out competition engine where speed and power are your main targets and you don't mind replacing liners and piston safter one or two runs which could see them worn enough to mak eth eengine loose performance.

I am familiar with the pin to stop the liner from rotating, and have seen it on nearly all my nitro engines! And now making the sleeve out of steel makes a lot of sense.

 

[Kosiba]

The head holding the sleeve in would be the best. Nothing would be more secure than a small ridge at the top to keep in place.
The head would not let it go up and the ridge prevent it from spitting out.

The relief prevents or insures there would be no crush effect.

Relief as a groove in a steel sleeve would be fine.
As Jason pointed out, the entire cylinder made of steel is a good idea.
Pinning a 2 cycle sleeve would be important.
One must consider materials when fitting parts with different expansion rates too.

Now that relief makes a lot more sense, and I do agree that pinning a 2 stroke sleeve would make the most sense, and I also agree that using the head on a 2 stroke engine would be the simplest way of holding the sleeve in the block, but for a 4 stroke I think just having a tight enough fit would also work, but you would have to be more careful with the material composition of both the sleeve and block.

 

[SmithDoor]

I Just started watching this youtube series of a guy making a motorcycle engine from castings, and when he started machining the cylinder sleeves he had cut a small relief into the sleeve, and then I went to look on one of my 2 stroke nitro sleeves and saw that there was one there too, and now I'm left wondering what they're for and how would you go about actually designing different cylinder sleeves? Like how could/should you position the holes on a 2 stroke sleeve, or what does that relief actually do?

View attachment 165318
The relief would be right below the lip at the top, this one doesn't have it

View attachment 165319
And this on does have it


All help understanding this would be greatly appreciated!

I may what to look at some big Caro ships using 2 cycle instead of steam and saves on fuel.

FYI This was a big surprised for me. I alway was thinking 2 cycles on small engines. Now on the biggest engines too.

Dave

 

[Bentwings]

So you are interested in building a model size, high performance, glow ignition two stroke? That's what that article is the history of. Friction outweighs nearly everything else as engines get smaller. A very long time ago I had a conversation with Glen Dye who said the most important factor in a racing engine was the piston to sleeve fit. The other articles in the series explain the procedures needed to build these very high performance engines and some modern examples.

Lohring Miller

Interesting. Man, many years ago when I was apprenticing tool making in the big machine shop. We got a full house Sunnen home machine. Piles of different hone stones. The cones doing a lot of carbide can industry tooling these carbide pieces required super finishes. Carbide turns almost black when ultra finished for draw dies. We had one of the first 1000 grit ID grinder wheels . These did not require dressing. Only precise indicating in to 0001” run out. They ran about 20 grand rpm on old rebuilt Brown and Sharp id grinders. The spindle bearings were sir supported. I YHINK the machines were old WW2 that was rebuilt to new standards . The gaging was air tool special
Made plug gage you used after initial diameter was reached the machine basically whistled as it ran. Feed dials were really big each line being 1 tenth of .0001”. Temperature controlled and measured. I also used the standard Sunnen hone machines . There was a contingent of model plane speed racers that worked there too. I often honed cyl liners and external honed pistons forvthe ngno guys. Some cyl had stick fit at The top. These were calculated to open up as they ran so sleeves were tapered in effect. 2 stroke nitro engines . Many used single blade props I didn’t go to their events as I was into full sized top fuel drag racing honing and fitting was much looser . Anyway I’m well familiar with tight honing

 

[josodl1953]

I think the purpose of the recess is best illustrated with a few sketches . Situation A might occur when the radius of the liner flange is bigger than the radius of the housing, causing the liner not to fit properly. This can be avvoided with a very small radius ( or no radius at all) of the flange ( situation B). In general, sharp inner edges in mechanical parts are not a good idea, because it results in strong stress concentrations near the edge. This is where the recess gives a solution ( sketch C). This ascertains a good fit of the liner in the housing and avoids the stress problem.

If you want to design a two-stroke liner I think you should look up information about two-stroke theory. In the past decades lots of research has been done to improve performance of two-stroke racing engines and exhaust resonation systems. A lot of work has been done in the fifties by the East-German engineer Walter Kaaden who worked at the MZ works , producing very competitive motorbikes.

Nowadays the importance of two-strokes is diminishing due to environmental issues .
I include a PDF about the two-stroke I found somewhere at the internet.

Jos

 

[lohring.miller]

That's the first in another series of articles I wrote.

Lohring Miller

 

[josodl1953]

I wondered where I got the article from, thanks for reminding me. The following chapters (2,3 and postscipt) are also very interesting, especially for me, having raced model speedboats for about 40 years. (some of them with CMB engines).

Jos

 

[lohring.miller]

I still race RC boats. These days I run electric powered boats, but in the past I did a lot of work with IC engine boats. I actually won a class at last year's national championships. However, the technical side of RC boat racing and especially two strokes are my strong points, not race driving.

Lohring Miller

 

[TSutrina]

I Just started watching this youtube series of a guy making a motorcycle engine from castings, and when he started machining the cylinder sleeves he had cut a small relief into the sleeve, and then I went to look on one of my 2 stroke nitro sleeves and saw that there was one there too, and now I'm left wondering what they're for and how would you go about actually designing different cylinder sleeves? Like how could/should you position the holes on a 2 stroke sleeve, or what does that relief actually do?

Typically the bore in the casting could have a sharp edge. The sleeve machined or ground will have a radius at this corner. so this is a relief for the sharp corner. There a re typical types of relief that are commonly use. The most difficult is a narrow slot at 45 degrees to both surfaces. This particular one can be done with a grinding narrow wheel.

View attachment 165318
The relief would be right below the lip at the top, this one doesn't have it

View attachment 165319
And this on does have it


All help understanding this would be greatly appreciated!

 

[SmithDoor]

I know this a little off topic but interesting reading for following this on build a 2 cycle.
It on one largest 2 cycle engines today

If do like please contact me and will remove

Thank you Dave

Note: If look at RPM it is the prop speed no need for gear box .
Other articles i read on manire 2 cyle engine is about same fuel efficiency as steam .

Wärtsilä RT-flex96C is a two-stroke turbocharged low-speed diesel engine designed by the Finnish manufacturer Wärtsilä. It is designed for large container ships that run on heavy fuel oil. Its largest 14-cylinder version is 13.5 meters high, 26.59 meters long, weighs over 2,300 tonnes, and produces 80.08 megawatts. The engine is the largest reciprocating engine in the world.

RT-flex96C
Overview
Layout
RPM range
Combustion
Output
Dimensions
Manufacturer	Wärtsilä
Production	2006–present
Configuration	Two-stroke straight-14
Cylinder bore	96 cm (38 in)
Piston stroke	2.50 m (98 in)
Max. engine speed	120
Turbocharger	Single
Fuel type	heavy fuel oil
Power output	80,080 kW (107,390 hp)
Length	26.59 m (87.2 ft)
Height	13.5 m (44 ft)
Dry weight	over 2,300 tons

Dave

 

[CaneSelvatico]

I know this a little off topic but interesting reading for following this on build a 2 cycle.
It on one largest 2 cycle engines today

If do like please contact me and will remove

Thank you Dave

Note: If look at RPM it is the prop speed no need for gear box .
Other articles i read on manire 2 cyle engine is about same fuel efficiency as steam .

Wärtsilä RT-flex96C is a two-stroke turbocharged low-speed diesel engine designed by the Finnish manufacturer Wärtsilä. It is designed for large container ships that run on heavy fuel oil. Its largest 14-cylinder version is 13.5 meters high, 26.59 meters long, weighs over 2,300 tonnes, and produces 80.08 megawatts. The engine is the largest reciprocating engine in the world.

RT-flex96C
Overview
Layout
RPM range
Combustion
Output
Dimensions
Manufacturer	Wärtsilä
Production	2006–present
Configuration	Two-stroke straight-14
Cylinder bore	96 cm (38 in)
Piston stroke	2.50 m (98 in)
Max. engine speed	120
Turbocharger	Single
Fuel type	heavy fuel oil
Power output	80,080 kW (107,390 hp)
Length	26.59 m (87.2 ft)
Height	13.5 m (44 ft)
Dry weight	over 2,300 tons

View attachment 165570View attachment 165571View attachment 165572

Dave

On an engine so big the downsides of a two stroke can be completely eliminated. It can have an enclosed oiling sistem, the pistons are oil cooled, the engine run so slow that you can scavenge the cilynder completely and also supercharge owing to the use of uniflow exhaust valves on the head.
So why use a 4 stroke that give one impulse every other turn when you can get double than that with a 2stroke that have the same advantages of a 4 stroke

 

[CaneSelvatico]

I Just started watching this youtube series of a guy making a motorcycle engine from castings, and when he started machining the cylinder sleeves he had cut a small relief into the sleeve, and then I went to look on one of my 2 stroke nitro sleeves and saw that there was one there too, and now I'm left wondering what they're for and how would you go about actually designing different cylinder sleeves? Like how could/should you position the holes on a 2 stroke sleeve, or what does that relief actually do?

View attachment 165318
The relief would be right below the lip at the top, this one doesn't have it

View attachment 165319
And this on does have it


All help understanding this would be greatly appreciated!

That relief on full size cilynder is used as a grinding relief as the sleeve and cilynder are machined to tight tolerances and heat fitted. Once together the sleeve would always be the hotter part and the fine ground surface would ensure an optimal heat transfer to the aluminium cylinder. An indexing pin is usually not used ad it is more trouble to fit and machine and can be a weak point in the thin liner.
You could do without relief if you have a good radius on the sleeve and a correct sized chamfer on the bore of the cilynder.

On porting....it's a whole world on itself as it's the equivalent of cam design on a four stroke. You can have radically different performance depending on size and position of the ports, but also on the bore and stroke size and conrod length. If you want to start from scratch I suggest to use a slightly under square ratio and an average porting timing, and then experiment to your liking

 

[lohring.miller]

Porting for small two strokes has been pretty well worked out. The biggest gains are from the tuned exhaust. As you can see from my first article 10 cc engines went from around 1 hp to over 4 hp, mostly due to the tuned exhaust. Large engines use turbochargers to do the same thing.

Below is another article on how to make a small piston and cylinder.

Lohring Miller

 

[emgee]

Hi Lohring

I see the cylinder head has a double bowl, I first saw this shape in a Super Tigre X40 pylon engine back in the late 1970's, are you a supporter of this shaped bowl ?

Emgee