AndyW

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I did a quick run of the .25 to test the head and the results are posted at

http://www.youtube.com/my_videos?page=1

The prop is a Graupner 11 X 6. Don't know how that compares to any other .25. As mentioned, this throttle has a fixed airbleed and this will be made adjustable for further testing. As in the .15 and the .40, it was found that the compression has to be a bit higher for starting. That's likely due to the higher mass of the larger engines. A bit of a let down, but you can't argue with physics. Still, the entire Norvel line responds well to diesel operation. Along with Norvel's inherent good fuel mileage, as diesels, they excel in this area.

Now to build some aircraft for these things and really put them to the test. [8D]

AndyW

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The addition of an adjustable airbleed really brought the .25 around. Their throttle for this engine is a simple one but has a unique and darn near brilliant method of allowing the needle to be angled back. There's no spray bar, the fuel is delivered through a hole in the barrel. You get a sort of reservoir of fuel ahead of the barrel and according to the Perry carb principle, this can help with acceleration. Interesting is that the stem for the throttle for the .25 is the same diameter as the stem for the .15 so this throttle can be tried on the .15 to see if the problem is with the carb.

A quick look and it appears that the bore in the barrel is the same. No I ain't gonna bore out the .25 for more power. It's going to stay a diesel and the bore is going to stay where it is.

Anyway, the latest run can be seen here.

http://www.youtube.com/watch?v=2-tdOap3K0M

qwertypemdas

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I have a Norvel 25 big mig engine. Runs great. I want to convert it to diesel, I have a drill press dremmel etc. but no lathe or cnc equipment. Are there any instructions on how to make a deisel mod for the norvels? If you can, plz post pix of your converted norvel and some instruction. I am very experienced with engines (glow, gas, co2, steam) but I don't own any deisel engines. I am comfortable risking possibly destroying my engine ($27 on ebay).

Motorboy

There are not instruction to make a cylinderhead with contrapiston...

Lathe are neccesary to make a cylinderhead and contrapiston. CNC not important.. The bolt holes in the cylinderhead are drilled after same measure from original cylinder head. Also mount the new and old cylinderhead togheter with a thinn bolt though the holes of glowplug and compression screw hole, then drill in same way from old cylinder head screw hole to a new cylinder head in right radius and angle.

The cylinderhead has a bore inside where the contrapiston are moving inside the bore from 0 mm to 3-5 mm with a compression screw. The contrapiston has a O-ring too keep tight against leakage and fittet tight in the bore. Both cylinderhead and contrapiston are made of aluminium. Sometime the contrapiston are made of steel or brass to prevent loss of heat (improved idling).

The height of cylinderhead can be same as height of original cylinderhead or some millimetre higher than original cylinder head.

Before you are making the cylinder head, first make a plan of the cylinder head with contrapiston + O-ring and compression screw if you are a new beginner!!!

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Here are instructions for making a variable compression head for a Drone diesel. Could be modified for the .25 engine. Jack

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Files did not go thru first try. Jack

AndyW

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That's good information and advice. But first, try this. Make up a simple disk out of 1/16th aluminum to replace the glow button. Add six copper gaskets to the one that's already there and try starting your fixed compression diesel. If it doesn't start, take out one gasket and try again. At one point, you'll get the correct compression setting and you could possibly get away with having a Norvel diesel without too much effort.

The key is to have lots of ether in your fuel mix, 40% with 40% kerosene and 20% oil. Ass 2% cetane booster and your engine should run. Be very careful NOT to over prime it. With a "dry" engine, just apply four DROPS of fuel to the INTAKE only,,, NEVER into the exhaust. You'll be using an electric starter and most of the prime will be blown out but not all. The rod in all the Norvels is made like a dogbone and the round stem is too easily bent when you run it as diesel.

I can make a head for you but that would cost double what you paid for, for the engine. They're handmade on simple tools, and take much time to make.

Keep in mind that the reason the compression ratio is made adjustable on MODEL diesels is that the correct compression can vary according to differing fuel mixes, temperature, humidity and even the age of your fuel. Stale fuel simply means that some of the very volatile ether has evaporated and the compression setting required will change.

But try it and let us know how you made out.

For the fuel, if you can't buy it ready to go, here's how to mix your own.

Kerosene from the hardware store.
39%

Ether from spray, Quickstart, (for starting diesel trucks in the cold) the best is John Deere brand
39%

Castor oil, from the drug store, (not the best but OK just to try) From Castrol or Klotz, bike shops have them. BIKE that is, motorcycle, not bicycle.
20%

Cetane booster, best is from Amsoil, available mail order from here, http://www.amsoil.com/a/Fuel-Additiv...mance-Improver 8 dollars plus shipping gets you a lifetime supply.
OR just get the liquid catalyst for fiberglass resin, MEKP,, (not MEK) BE EXTREMELY careful, this stuff will burn out your eye in seconds, use goggles. When mixed in fuel, though it's pretty safe.
2% NO MORE, more is not better.

This mix will allow easier starts especially with a fixed compression engine.

Good luck.