engines

[ozzie]

saw this whilst in italy. a small go kart engine water cooled, small belt drives water pump, reduction drive. fitted to a paraglider back pack this one is around 100 cc but also has a bigger brother. has about 500hrs runs hard but starting to sound tired. don't know if the redrive could handle the load from a tractor setup. 45lbs thrust.[SIZE=1]

[Chappy]

Steve,

As a comparison (just for fun), the 99cc Pioneer P61s turning around 8000rpm, with my homemade pine props and V-belt re-drives, and straight pipes can produce a peak static thrust of 65 pounds each. With dual Briggs and Stratton lawn mower mufflers (my current setup), they make ten pounds less each. On the down side, though, 200 hours is about all they can make before being all used up!

I guess that net they have to use for protection from the prop really hurts the thrust, and the penalty must get even worse as their airspeed increases.

Oz, great picture, but how about using a camera next time instead of a microscope!

HeHeHe

Chappy

[daffy1029]

hi, y'all
Are we still talking 2-stroke here? A water-cooled 2-stroke should last much longer and usually they put out more power. For example a stock air-cooled engine in a snowmobile and a stock water-cooled engine of the same size, it seems the water cooled sleds out perform the air-cooled in drags and lasting ability. The air-cooled sleds can sometimes perform better in deep snow because of their lighter weight (if they don't overheat). You can push a water-cooled engine a littler harder as well because it is reluctant to overheat . Just my two cents worth.

Chappy, how are parts to get for your Pioneer engines? What does it cost to rebuild a Pioneer completely? I would think they would be economical to rebuild.
By the way, I just finished testing one of my old JPX engine and the thrust I got was 80 lbs. direct drive at 4200 rpm(2500ft above sea level), using 34 x 20 pitch prop. These are rated 20 HP. So your 5.5 HP Pioneers are really impressive at 65 lbs thrust. Well done!
Daffy

[Chappy]

Daffy,

There don't seem to be a whole lot of rebuild parts still available for the little Pioneers. They may be out there somewhere, as some places seem to have a cylinder, another place pistons and rings. I don't think I've come across a crank in a long time.

Anyway, I've never rebuilt one, just cleaned them up now and then, and maybe a seal and/or bearing. Mostly it's just carb rebuilds and plugs.

Because so many early Lazair owners upgraded to the 185 Rotaxes, for a time there were lots of low time Pioneers floating around, and I was given several pairs way back then (Dale and Peter Corley gave me at least two sets). I still have one good, unmodified set for my next replacement. The biggest mod I have to make to the engines before I can use them is to machine the second side of the crankcase flat and drill through the crankcase at each of the clamp screws. Long AN3 bolt then clamp the crankcase together between the two re-drive plates. The starter assemble is removed and mounted back on the original side on a homemade bracket. A homemade sheave is mounted on the power takeoff end of the crank.

If you just hold the engine in your hand and look at the small physical size of its components, you begin to realize why the engines don't last very long. The engine itself only weighs around six pounds. As a chainsaw, you wouldn't hold 6500-8500rpm for very long periods - mostly fairly short blasts of full power. 200 hours at these continuous high rpm/power levels would probably equal cutting up a whole bunch of trees, I would think.

I've found that if I run them fairly rich, I lose a little performance, but the engines run so much cooler that they hold up quite a bit longer. With the mixture leaned for maximum power, the cylinder head temps can run way up there at 450+ degrees F (yet I've never had a piston or ring failure). The most severe failure I've experienced was on a high time engine when the PTO end crank bearing shell started spinning inside the crankcase. The bearing overheated and the ball separator melted, permitting the balls to try to bunch up, causing the engine to abruptly lock up. Boy, did the belts let out a screech.

A slow turning, long prop is much more efficient (and quieter) than a smaller, directly driven prop. I put a lot of work into designing and building very efficient props, and they are very lightly loaded. Along with the 2.75:1 reduction and running the engines at maximum power, they do surprisingly well (for a while, anyway). BTW, the Pioneer only produces around 4.5 horse power or so when running direct drive props! Find a power output to rpm chart for your engines, find your rpm with your direct driven props, read their actual power output, and weep.

Chappy

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[daffy1029]

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[Chappy]

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