Does anyone make diesels?

[eskimobob]

I can't recall seeing any diesel powered model engines. I would have thought they would be more popular than petrol engines because of not having to have the spark electronics but presumably the complexity of injectors and pumps outweigh this?

Having said that, I've seen model aero engines that are called diesels (although they probably run on something other than actual diesel) and they seem to have only rudimentary carburettors...

 

[Jadecy]

You are correct about the model aero diesel. That was the first type of engine I built. The fuel is a mixture of ether and oil and if you buy the fuel from a vendor it may have some other volatile component. The model aero diesel is nothing more than a piston port two stroke engine run on a fuel that will explode under compression.

I've been to several shows now and have not seen a true diesel yet either. I don't know enough about the full sized diesel operation to even make an educated guess as to why there aren't models of these.

 

[vlmarshall]

The model aero diesel is nothing more than a piston port two stroke engine run on a fuel that will explode under compression.

That's all a Detroit Diesel 71-series engine is, too.

 

[bentprop]

I think you've answered your own question,Bob.
The injector would be the biggest problem imo.The fuel nozzle would have to be incrediby tiny.Also,I doubt whether it's possible to get the huge pressure required that's found in full size diesel injection systems,but who knows,maybe some clever fellow will find a way to do this in the future.
The model diesel are really just compression ignition engines,and as such not true "diesels".
It was the model airplane fraternity called those engines that,presumably because the principle is similar to some degree.And "compression ignition engine"is rather a mouthful.

 

[NOI53Y]

Hello,

My wife is the manager of a diesel fuel injection specialist workshop (long story short she is a mechanic ;D ) and what bentprop said is correct. It would be an extremely difficult task in making both the injector and the the fuel pump.

The injectors alone are an amazing bit of gear to see pulled apart. The nozzle on a full size injector is tiny as is so I could imagine how hard it would be to make a miniature version.

The other problem would be getting the fuel to a high enough pressure in the fuel system to be atomized properly.

Having said that it would be awesome if someone could pull it off and make it work. I lay down the challenge for someone to make it work ;D

 

[Stan]

Detroit 2 strokers are not like a carburetted engine of any type. They have a blower which maintains pressure in the wind box so that when the intake ports are exposed the pressurized air purges the cylinder out through the exhaust valves and has the cylinder full of air under pressure when the piston starts it up stroke.

One of the main purposes of the small holes in the injector tip is to atmonize the fuel. I don't think you could reduce the size very much and still force fuel through it with any reasonable pressure. You could eliminate the high pressure fuel pump by using unit injectors, pioneered by Detroit, and now used on the computer controlled engines, With a unit injector, a piston is the high pressure pump and by changing the stroke lengh, you control the amount of fuel. It is still a lot of precision work requiring a 20 to 1 compression ratio.

 

[vlmarshall]

A lot of work, but it'd sure be nice when completed. I don't miss the work, but I do miss the sound, of a good Diesel.

 

[Orrin]

A friend of mine has built some. Rather than repeat all the information, here, I'll post a link to the topic in another forum. I don't think it is mentioned there, so I'll add that Done had to drill some 0.005" holes while building his four cylinder.

http://www.smokstak.com/forum/showthread.php?t=50410

You'll find a picture of the four cylinder in the above thread.

Orrin

 

[mu38&Bg#]

The smallest practical and efficient diesel injection system is currently 4-5HP per cylinder. Smaller will work as can be seen, but it will waste a lot of fuel as evidenced by the smoke.

Has anyone attempted to build "The Dux" fromt he SIC plans? It's a 50 or 100cc four stroke injected diesel. There was someone at NAMES 2007 that had one in progress.

 

[Jasonb]

Very Nice model of Rudulf Diesels experimental engine of 1897. 150bar pump pressure, thats 2175psi :

http://www.model-engineer.co.uk/albums/member_photo.asp?a=6778&p=123122

Scroll back & forth for some more pics, soon to be featured in Model Engineer Mag

Jason

 

[Florian]

There has been an article in the german "Maschinen im Modellbau" magazine from a german guy called "Erich Beyer".
He did build a diesel engine with 7 ccm which seems to work quite good (after 20 years trying, forgetting it, finding it again and trying again to get it working...)
I'll see if i can find something in the web...
By the way: he started this project altough he was told several times it would work under no circumstances...

Florian