Real (Wo)Mans 20" planer, 9.8HP Diesel (w/pics)

[Robatoy]

Oewww... I oughtta....

[B A R R Y]

No, but there have been diesels small enough to power r/c airplanes for at least 15 years. They work really well in scale aircraft, as they handle long exhaust extensions well, swing large props at a slower speed, and have a more realistic sound.

They had great promise, but Thielert, the biggest player, who based theirs on a Mercedes turbo diesel, went BK. According to a podcast I listened to a few weeks back, Thielert left far more orphans than I would have guessed.

Since jet fuel is far more available worldwide than avgas, I thought it was going to be big! I think the main reason for the lack of interest in North America was the easy availability of avgas, and the availability of a relatively easy 87 octane auto gas conversion for many engines. Lots of guys who did the 87 conversion are now having problems finding ethanol-free unleaded...

[J. Clarke]

I suspect that ultimately a multifuel engine would be a more fruitful approach, and small multifuel reciprocating engines do exist--the Army used them on trucks a while back and Evinrude has a multifuel two-cycle outboard. Don't know how the Army does it but Evinrude uses direct injection like a diesel but with relatively low compression (by diesel standards) and a spark plug.

[Morris Dovey]

Hmm - In my ignorance, I have to wonder how well a low compression engine would fare at 8000'/2400m. Would that work?

(I played with diesel model aircraft engines in the 50's, but they ran at fairly high compression.)

[Robatoy]

That would be extra work... dragging that lumber up a mountain like that? What if you didn't have a mountain nearby?

[Morris Dovey]

Then I'd probably need a little help from my friends.

[J. Clarke]

Diesels typically have compression ratios from 14:1 to 24:1. Few gasoline engines go higher than 12:1 and most considerably less. The Continental O-200 has 7:1, the Lycoming O-235 has 8.1:1. Both are very popular aero engines that work fine at 8,000 feet. The Rolls-Royce Merlin that powered the Spitfire had 6:1 but it also had a blower.

All diesels run at high compression--it's the nature of the beast that they have to.

[Morris Dovey]

Thanks, John. The mention of a low compression aircraft engine confused me - I suppose a 14:1 might be a "low compression diesel" then, even though that might be fairly high for a gas engine. IIRC, my old Volvo B20 (gasoline) engine had a compression ratio of 11:1, which I was told was fairly high for a car.

I appreciate the info.

[Morris Dovey]

I checked with the optician who stripped and recoated my polycarbonate glasses a while back and learned that that isn't being done any more because the stripping process can produce ripples on the lens surface.

I asked about using windshield scratch filler/remover products and he thought that /might/ work short-term, but would probably not survive much lens cleaning.