Wanna see my model engines?

That's why they are called Semi Diesels. This isn't the real Diesel process. They are very bad at low revs, so this isn't an option for my models.

Nick

I've made and burned a bit of biodiesel, Ed, and its cetane runs quite a bit higher than 40. Here's a quote from one of the abstracts on the biodiesel.org's site:

"A typical cetane number range for #2 diesel fuel is 40-45 while #1 diesel is 48-52. Biodiesel from vegetable oils have been recorded as having a cetane number range of 46 to 52, and animal fat based biodiesels cetane numbers range from 56 to 60."

Run your model diesel on processed bacon grease.

Dale Scroggins

Pennsylvania

Aha. I hadn't thought about the difference in the way the fuel burns in a carburetted versus an injected compression engine.

Have you considered a solenoid pump for your model? I don't have any reason to believe it would be the answer, but I'm curious.

If you do, please let us know. There probably are some papers on it, buried deep in the archives at MIT's Sloan Automotive Lab, or in Germany, in Rudolph's papers. I've never tried that route because it's just a hobby question. Maybe when I'm retired.

Pennsylvania

OK, but I got those numbers a few months ago from international engineering societies, and I didn't see a single one that said biodiesel meets the

45-cetane standard. In Europe, they've been experimenting with blends to see how much biodiesel you can mix in and still keep a cetane rating of 40.

It's over my head because there's a lot of chemistry involved in the reports, and I'm just going from reports. But be wary of the incentives and enthusiasms behind the sources you read: biodiesel.org wouldn't be my first choice for objective info. It's not a matter of individual facts so much as perspective.

-- Ed Huntress

Well, that's the way it was defined in the patent (which, beside, didn't work and Diesel had to change it. -> Cunning's book!)

Solenoid not, but something like a piezo might be an option. But as soon as you have a plunger, you have trouble. The necessary tolerances are in the 1/1000mm range. I made some tests that looked quite encouraging. The plunger has to have a diameter of about 0,7mm and be in the 5mm lenght range, minimum stroke is about 1mm (all for

100ccm). Fun lapping it.

The person I'm talking about is still alive, and I have seen his cute Diesel model.

The whole thing is more a mechanical problem than a theoretical. You need valves that are tight at 40..80 bar, open/close with only a slight lift, need plungers and cylinders that fit 1/1000mm, ... And even if I get it working, the model I'm planing to build doesn't inject fuel directly, but uses compressed air to blast the fuel in. Now making a compressor (two stage, 1:40) in the size of your thump is yet another challenge ...

I'm not decided how the next engine will be fired.

Nick

Eh, you got my journalist juices going. I sent email about it to MIT's top engine-fuels expert. If he gets back to me I'll let you know.

-- Ed Huntress

Since you're into it this deep, I'd like to suggest something you may want to consider: magnetostrictive metals. I have some (indirect) experience with them. They produce much more force than piezo, and they're good for (IIRC)

20 kHz. They activate very simply, with a solenoid-type coil, but they do have some mechanical hysteresis.

They're used in some mechanical applications now. The technology was developed for sonar transducers. Small bars of the material are reasonably priced.

Have fun. It sounds like you've developed your work into something close to laboratory research.

-- Ed Huntress

~~~~~~~~~~~~~~~~ The name says it all!

Now this sounds (pun intended) _very_ good! Thanks a lot for that hint!

Say, do you know how much they contract at about (%-wise)? Going to have to google for a source (no success until now).

Sometimes I do have the same impression. ;-) Next, I will publish my tube-bender (it took me 50 hours of development and two prototypes to be thrown away). Look at the tubes of the Ellwe to see how good they are.

Thanks again for the magnetostrictive metal Nick

Go to Google and look up Terfenol-D. Also, look up "magnetostrictive transducer." Without the quotes, I got 20,000 hits.

You may run into one of my old articles about it. When I was at Wasino, we, in cooperation with Etrema, who were the material experts, were developing it for elliptical piston-turning.

The properties are well-known. The force is very high compared to any comparable technology. When I Googled, I saw a technical paper about modeling the hysteresis, but I didn't read it.

IIRC, some engine company was considering using it for fuel injection, but I don't trust my memory that far.

Anyway, it's a great project for an experimenter. As for prices, go to:

They'll give you a quote. You may find a similar material cheaper somewhere. The US Navy uses it in sonar, so there must be other sources.

-- Ed Huntress

a 232cc diesel engine, 71lbs and rated at 1.8hp, here's the specs its also available in vertical shaft. Runs up to

3600rpm. Makes me wonder if their injector system would be usable in a scale engine...

Would you have access to a used one of those motors to play around with? --Glenn Lyford

Nice. But still about factor 4 too big.

Downloaded. Thanks for the hint.

Umm, I think not.

Thanks, Nick

That was it. Got enough stuff to read now. And found 2 or 3 articles about EFI with Terfenol.

Is Terfenol machineable (without having an EDM), and how? Couldn't find anything.

Very interesting that material, thanks again!

Nick

[I got quite some stuff to read, so the answer is a little late]

That engine has a CR of 1:22. Interpolating with the bigger Hatz of the same family, a 100cc diesel would need 1:23 or 1:24, a 50cc 1:24 or

1:25. About what I guessed.

Nick

Aha! Well, it's a very logical application. I'm not surprised that someone has been working on it.

I forget. I think I used to know, but I forget that, too. It's been a few years.

Now that you're on the trail, I'm sure you'll be able to get answers. The Etrema people are very knowledgeable and I always found them forthcoming when I talked with them.

You're welcome. It will be fun to experiment with it if you get your hands on some. Making it work is very easy. Making it position a tool to +/- 1 micrometer through its full stroke, on a lathe turning at 4,000 rpm, is not so easy. That's where the hysteresis becomes challenging.

However, I'm guessing that, for injection, all you'll have to do is add a compensating factor to the solenoid current as the rpm increases. That could be a simple circuit.

Maybe. I hope. In its favor, it's much more durable than a stacked piezo array, in addition to producing more force, and it apparently doesn't fatigue in service.

-- Ed Huntress