[Adaware]

I'm currently making some drawings of an engine but it's a tight squeeze between the bores because of the cylinder setup.

So i'm wondering if it is possible to use maybe chrome moly tube as cylinder liner?
The piston will be alu silica but the piston rings is an X-factor here.

I would like to avoid the use of cast rings so i need an alternativ material in combination with steel liner.

The bore is about 40mm.

[stevehuckss396]

In my models I use 12L14 steel liners with 7075 aluminum pistons and cast iron rings. My bores are alot smaller than 40mm so I dont know if it will hold up in an engine the size of yours.

[RICHARD ZASTROW]

With compatible ring material steel liners should work.

A lot of 2-stroke engines use chrome plated or Nikasil on aluminum. Those generally use caste iron rings.

Dick Z

[Adaware]

Nikasil coating is not a option because it's so expensive.

The liner must have I.D of 40mm and a O.D of 43-44mm som i seem to have made myself a problem here and i would preferrably not change the drawing since it is very intricate.
The block itself is aluminium and the liner will be supported by metal on the backside all around so it won't flex and bend away because of heat. What i mean by this is that it's not a "wet liner".


Cast iron rings is okay with me if it means i can use such a thin cylinder liner

[dynosor]

So i'm wondering if it is possible to use maybe chrome moly tube as cylinder liner?

Yes. Rotec use 4140 for their cylinders:

From Rotec Radial Engine Specs:

"Fully machined aluminium crankcase and heads. Steel 4140 billet crankshaft, nitride hardened and ground, running on two large anti-friction roller bearings, propeller support and end thrust controlled by single deep groove ball bearing (all standard practice). Steel 4140 master and link rods deeply I beam sectioned and plain bushed, all lubricated by mains oil pressure. Steel 4140 cylinders precision honed to a perfect finish and exact tolerance."


The OS and Magnum single cylinder model engines have steel rather than cast iron liners too:

From: TowerHobbies.com | 42503100 O.S. Cylinder Liner FS155A-P

FEATURES: Steel construction

SPECS: Length: 45.5mm (1.79")
Outer Diameter: 36mm (1.42")
Inner Diameter: 33mm (1.3")

Rings are most likely cast iron...

[Adaware]

Thanx guys :-)

Always help to get on this forum. Now i can continue with the modelling without changing the basic structure of the engine.

[handlewanker]

Hi adaware, I recently rebuilt a Ryobi whipper snipper, capacity about 28cc, 2 stroke (grass trimmer, whatever), for my son.

The problem was it had no compression, so it got pulled apart.

The single ring on the alluminium piston was totally coked into the ring groove with burnt oil residue, it was impossible to move it to clean it out, and it broke in the attempt.

Long story short, the cylinder appeared to be hard chromed on a cast alluminium base material, with an alluminium piston and the ring being cast iron.

If'n I was designing an engine with bores so close together I'd have the block bores hard chromed directly to the block, might need grinding and normal honing to desired finish as required.

I also pulled a Briggs and Stratton 3.5hp 4 stroke lawn mower engine apart to refubish it, and it appeared to have the cast iron rings (2) running directly in the alluminium bore.

Bore size is about 60-70mm diam.

As this engine you have designed is probably not a production model, you could make the liners from Mehanite cast iron, but make the bores 2mm smaller, then press the liners into the block (.001" per inch of diam for press fit is all that is required, warming block first), and bore them out to size in situ after.

The liners will have a step on top with a counterbore in the block and this will locate the liner between the block and head, so no problem with jumping up and down...LoL.

I wouldn't bother with the problem of wet liners, that is only required if'n the heat transfer to the block is so poor and you just have to get the max heat transfer to the block.

For the amateur with home shop facilities, 4140 is a cow of a material to work with, it goes walk about if'n you subject it to heat after finish sizing it, and heat treatment is a field no angel likes to tread.

Meehanite on the other hand is very forgiving, as long as you don't "attack" it with blunt tools, and requires no heat treatment at all.
Ian.