Long stroke

[camerart]

Hi all,

I'm just about to experiment with a long stroke diesel 2 stroke engine. I've never done engine making before.

Does anyone know anything about making an engine with a very small bore and a very long stroke, say, 5mm bore X 100mm bore?

I want to see what the power and the piston acceleration is like.

[GlennW]

Welcome to the group!

There are desktop dynamometer programs available that will calculate that for you. Not too sure they are available for diesels, but they probably are.

[camerart]

Hi Glenn,

Thanks for the welcome.

I'll look out for Dynamometer programs.

Thanks.

[ronm]

Did you mean 5mm bore by 100mm stroke?
A Diesel is really hard to make run once you get under about a 2" bore-the relative surface area to the combustion chamber volume makes it hard to get enough compression heat to ignite the fuel...this was discussed at some length in the old Strictly IC magazine, along with the difficulty of miniaturizing the fuel injection parts. Unless you're talking about the "diesel" model airplane-type engines, which are a whole different animal, compression-ignition, but not a true Diesel, since the fuel isn't injected into the cylinder. Kinda seems like that long a relative stroke would lead to breathing problems, but you're welcome to experiment...go for it!

[JackF]

camerart,

Try this site.....
http://www.rcuniverse.com/forum/m_10411 ... ntable.htm
It may lead you to some info.

Jack.

[camerart]

Jack,

I had a look at the site, and it is interesting. I also have engines to copy, but this is an experiment and I think unusual. Thanks.

[camerart]

Did you mean 5mm bore by 100mm stroke?
A Diesel is really hard to make run once you get under about a 2" bore-the relative surface area to the combustion chamber volume makes it hard to get enough compression heat to ignite the fuel...this was discussed at some length in the old Strictly IC magazine, along with the difficulty of miniaturizing the fuel injection parts. Unless you're talking about the "diesel" model airplane-type engines, which are a whole different animal, compression-ignition, but not a true Diesel, since the fuel isn't injected into the cylinder. Kinda seems like that long a relative stroke would lead to breathing problems, but you're welcome to experiment...go for it!

Ronm,

Yes 5mm X 100mm. Or similar, I'm not sure what to expect regarding piston acceleration and power, but this is supposed to be a 1st more gentle engine, as first experiment.

It will be similar to 'diesel' model engines.

Do you think the breathing problems will be into or out of the cylinder? or both? With the design I have in mind the fresh charge can be easily pressurized into the cylinder.

[dly31]

It certainly is an interesting concept. I would try to research why such a ratio has not been used. It seems to me like the need for a two piece rod might be a big factor. It also seems that the combustion pressure would be effectively dissipated long before the end of the power stroke.

[camerart]

It certainly is an interesting concept. I would try to research why such a ratio has not been used. It seems to me like the need for a two piece rod might be a big factor. It also seems that the combustion pressure would be effectively dissipated long before the end of the power stroke.

Don,

I've been around engines for about 50 years, and am only now finding out about stroke ratio. This is going to be a LINEAR ENGINE, so the rod would be straight from one piston to the other. Which would give a variable compression ratio. I also wonder about what might be happening to the combustion between ignition and reversal of the piston, with no TDC.

You have the feeling that the power would have gone long before the end of the stroke. Do you also have a feel of 'say' a line on a graph of the dissipation? If it's true that all of the power has gone, then I will make the 1st ratio shorter.

[Russ Hanscom]

One problem is that with that much surface area compared to volume, there is going to be excessive cooling and heat loss, and loss of heat translates to loss of power.

[camerart]

Ok Russ,

What ratio is the longest you would recommend, bearing in mind the excess heat.

[Russ Hanscom]

The bore and stroke is up to you, feel free to experiment. Modern trends have been towards larger bore and shorter stroke but nothing says you have to go that way.