Cylinder Sleeve Design

[Kosiba]

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?

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

And this on does have it


All help understanding this would be greatly appreciated!

 

[GreenTwin]

Jeff Henise casts his own racing motorcycle cylinders.
I can only guess that the relieve allows for a complete sliding fit of the sleeve into the cylinder, with no possibility of it seating slightly high.
I think Jeff heats the cylinder, adn then presses in the sleeve.

https://www.homemodelenginemachinis...se-casting-motorcycle-racing-cylinders.35502/
.

 

[Kosiba]

Jeff Henise casts his own racing motorcycle cylinders.
I can only guess that the relieve allows for a complete sliding fit of the sleeve into the cylinder, with no possibility of it seating slightly high.
I think Jeff heats the cylinder, adn then presses in the sleeve.

https://www.homemodelenginemachinis...se-casting-motorcycle-racing-cylinders.35502/
.

Thanks, any idea on how to design a 2 stroke cylinder sleeve?

 

[GreenTwin]

I seem to recall seeing a book that discussed ports and such for a 2-stroke.
I am not up on that design technology though.

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[Kosiba]

I seem to recall seeing a book that discussed ports and such for a 2-stroke.
I am not up on that design technology though.

.

Can you remember the name of the book?

 

[GreenTwin]

The name of the book was "Tuning for Speed", by P.E. Irving, Temple Press Books, London, 1960.
First Ed. 1948.

The two stroke information is a bit dated, and mentions a rotary valve.
The modern two-stroke motorcycle engines use valves in a cage just downstream of the carburetor.
There is some port information, so it may be useful.
Better than nothing for sure.

The 4-stroke information in this book is very good.

.

 

[Kosiba]

The name of the book was "Tuning for Speed", by P.E. Irving, Temple Press Books, London, 1960.
First Ed. 1948.

The two stroke information is a bit dated, and mentions a rotary valve.
The modern two-stroke motorcycle engines use valves in a cage just downstream of the carburetor.
There is some port information, so it may be useful.
Better than nothing for sure.

The 4-stroke information in this book is very good.

.

Thank you very much! I'll try to get my hands on it asap!

 

[GreenTwin]

Here is one currently on ebay.
Some on Amazon too, paperback I think, and probably a reprint.

 

[Jasonb]

I've not looked at the video but if he is using insert tooling that all has a radius to the tip of the tool to some extent. If you were to drop that liner into a cylinder that had a square external corner then it would not seat down correctly. The groove give sclearance though the external corner of teh block should also be at least deburred or slightly chamfered.

As drawn your one has completely square internal corners which can become stree risers, if teh parting tool used to cut teh relief has rounded corners then you will get a stronger liner, the common GTN type parting inserts have these rounded corners.

Myself I use an insert with small 0.2mm tip radius and ease the cylinder block so no need for an undercut on engines that I build.

You will also see the relief groove being used for threaded components with a shoulder as you can't easily thread right upto the shoulder.

 

[lohring.miller]

There's a lot to two stroke design. I've written several series of articles on high performance ones. It would help to know exactly what type of engine you want to build. Below is a history of model, high performance two strokes.

Lohring Miller

 

[Kosiba]

Here is one currently on ebay.
Some on Amazon too, paperback I think, and probably a reprint.



View attachment 165327

Thanks I'll check if I can go to a library and check it there too.

 

[Kosiba]

There's a lot to two stroke design. I've written several series of articles on high performance ones. It would help to know exactly what type of engine you want to build. Below is a history of model, high performance two strokes.

Lohring Miller

Read it through and I don't quite understand most of the terms used when referring to the bypasses, but it definitely made me quite a bit more interested, and I now have questions about why most modern or relatively modern 2 stroke engines don't use any sort of piston ring?

 

[Kosiba]

I've not looked at the video but if he is using insert tooling that all has a radius to the tip of the tool to some extent. If you were to drop that liner into a cylinder that had a square external corner then it would not seat down correctly. The groove give sclearance though the external corner of teh block should also be at least deburred or slightly chamfered.

As drawn your one has completely square internal corners which can become stree risers, if teh parting tool used to cut teh relief has rounded corners then you will get a stronger liner, the common GTN type parting inserts have these rounded corners.

Myself I use an insert with small 0.2mm tip radius and ease the cylinder block so no need for an undercut on engines that I build.

You will also see the relief groove being used for threaded components with a shoulder as you can't easily thread right upto the shoulder.

So these reliefs are mainly just for clearance for sliding the sleeves into the block?

 

[lohring.miller]

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

 

[Kosiba]

I a

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

I'm currently trying my hand and just designing a bunch of engines, and then posting them and getting feedback, so I asked this question because I'm trying my hand at designing a 2 stroke cross plane inline 4 and was curious as to how to design a basic cylinder sleeve and way they are designed the way they are, so I can design a basic sleeve, that will give basic power results.

 

[Fidlstyks]

I have a small model airplane book that has drawings on making patterns and casting engines

Several formulas are in it

One states something to the effect of too little clearance, or too tight a fit o cast linee o luminum fined cylinder either caused too much heating or ran too cold.
I also note, like a piston is made slightly smaller at the top, because heat expands it.
Maybe the relief keeps mass down, which stores heat and causes expansion? Grove=less heating?
Note when making castings, a line deeply scribed in a pattern, makes a chill line in a casting, and castings break there easier.
To an extent, a line scribed in any cast iron is like cutting glaas, it breaks where the line is.

 

[Kosiba]

I have a small model airplane book that has drawings on making patterns and casting engines

Several formulas are in it

One states something to the effect of too little clearance, or too tight a fit o cast linee o luminum fined cylinder either caused too much heating or ran too cold.
I also note, like a piston is made slightly smaller at the top, because heat expands it.
Maybe the relief keeps mass down, which stores heat and causes expansion? Grove=less heating?
Note when making castings, a line deeply scribed in a pattern, makes a chill line in a casting, and castings break there easier.
To an extent, a line scribed in any cast iron is like cutting glaas, it breaks where the line is.

Is this just on cast metal, because the guy I was watching make the cylinder sleeve, had machined the sleeve from bar stock, does it work the same way? Because it was cast iron but it was machined down and he cut the groove and called it a relief groove.

 

[Fidlstyks]

Is this just on cast metal, because the guy I was watching make the cylinder sleeve, had machined the sleeve from bar stock, does it work the same way? Because it was cast iron but it was machined down and he cut the groove and called it a relief groove.

Most people make sleeves of hydraulic cylinders like this. Steel and aluminum expand the same, but at different temperatures.
If he called it a relief, then that is your answer.
The depiction looks excessive. I usually make a very small groove and usually would rather make an inside radias, and chamfer the block. But I do cast sleeves inside cast or brass blocks and usually pin instead of retained by a head like a model airplane engine .

 

[Kosiba]

Most people make sleeves of hydraulic cylinders like this. Steel and aluminum expand the same, but at different temperatures.
If he called it a relief, then that is your answer.
The depiction looks excessive. I usually make a very small groove and usually would rather make an inside radias, and chamfer the block. But I do cast sleeves inside cast or brass blocks and usually pin instead of retained by a head like a model airplane engine

I understand that it is a relief, but my original question was, why is it there, what does it relief, and while I'm at it how is this part designed in different cases. Making sleeves out of aluminum and steel is interesting, because I thought it'd be something like piston rings where it's made of cast iron. Do you know why people make sleeves out of these metals? Is it because hydraulic cylinders are the easiest option? Or is it because of material properties? And using a pin to retain the sleeve seems like it'd increase the stability over just using the head as the sole thing that holds it in place, but I'm also interested if there are other ways of holding the sleeve in the block. From what I can tell there a couple of ways, 1 like in a model plane which uses a 2 stroke engine, you could use the the head, but I'm not sure it'd work as well in a 4 stroke, 2 using a really tight fit, although from what I've heard so far due to the difference in temperature and rate at which different metals expand an contract might effect the stability of both the block and the sleeve, and 3 using a some sort of pin or screw.

 

[Jasonb]

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.