Lower budget engine options for a low budget UL

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proppastie

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The PPG engines from Italy are a mature technology.....3K not 1K but if you are going to sell completed aircraft to the public I would think you want something proven.
 

Dana

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I wonder what kind of muscle a 3 cylinder radial Chotia 460 Squarehead with modern fuel injection and computer controlled electronic ignition and spark timing would put out, without tuned exhaust, just short pipes.
2-stroke radials are problematic, since you can't use the shared crankcase to pump fuel and air into the cylinder. It would be theoretically possible to use a supercharger, but then getting it started would be an issue. I'm not sure how the few radial 2-strokes that have been sold are set up, there are a number of ways to do it but all are mechanically more complicated than the usual master rod on one cylinder with slave rods for the rest.

Though some pseudo radial engines have been built with a crankshaft for each cylinder, effectively independent engines all geared to a single gear on the crankshaft... you can get any gear reduction ratio you want that way.
 

Dillpickle

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lately since the design is public domain and I have a local source for the tubing and a sail manufacturer ready to support the venture with almost at cost sails im considering building a few weedhopper clones with a few little improvements for easy of building and airframe rigidity / durability. I have a price point in my head that I need the planes to sell for (roughly 1/3rd the cost or less of anything else on the market. im not considering this as a money making venture but a venture out of my love for ultralight flying and my desire to get more people involved and more planes in the air.
This is a question and contains ZERO judgement...but why a two axis plane when an option like Baslee's Dream Classic exists in three axis? also at a VERY low entry point. also they have that dream two place for instructing small people....
 

TiPi

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2-stroke radials are problematic, since you can't use the shared crankcase to pump fuel and air into the cylinder. It would be theoretically possible to use a supercharger, but then getting it started would be an issue. I'm not sure how the few radial 2-strokes that have been sold are set up, there are a number of ways to do it but all are mechanically more complicated than the usual master rod on one cylinder with slave rods for the rest.

Though some pseudo radial engines have been built with a crankshaft for each cylinder, effectively independent engines all geared to a single gear on the crankshaft... you can get any gear reduction ratio you want that way.
Koenig made 3 cylinder (430cc, 20-24hp) and 4 cylinder (570cc, 24-28hp) direct-drive 2-stroke radials. Apparently, Compact Radial Engines owns that design now (looks like they were sold to China)
Edit: the engine also has a rotary valve to control the intake into the crankcase.
 
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TFF

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Radial two strokes use a supercharger to keep the intake cycle normal. The crank case pressure only needs to be as high as a single cylinder, but it has more crankcase volume to fill with the other cylinders. Unlike a single cylinder, the supercharger keeps the crankcase pressurized all the time.
 

n3puppy

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Radial two strokes use a supercharger to keep the intake cycle normal. The crank case pressure only needs to be as high as a single cylinder, but it has more crankcase volume to fill with the other cylinders. Unlike a single cylinder, the supercharger keeps the crankcase pressurized all the time.
Does the Koenig/Compact Radial use a supercharger? Or does it use the multiple geared crankshafts like Dana described ? Hard to tell in the few pictures I can find.
 

TiPi

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Radial two strokes use a supercharger to keep the intake cycle normal. The crank case pressure only needs to be as high as a single cylinder, but it has more crankcase volume to fill with the other cylinders. Unlike a single cylinder, the supercharger keeps the crankcase pressurized all the time.
The Koenig engines don’t have or use a supercharger. They have a floating disc under each cylinder that seals the space between the piston and crankcase (like a reed valve) and allows for normal 2-stroke cylinder scavenging
 

cpd

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BBerson, how much thrust are you getting out of your direct drive setup, what prop and where did you source the hub?
 

BBerson

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I designed and made the custom prop. The prop is bolted to the flywheel. As I mentioned, getting 115 pounds static but could get 130, I think. Have not flown it.
 

henryk

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I am getting 115 pounds static thrust with my stock Honda 670cc, 58" narrow chord prop. Might get 130 pounds with a better prop.
-auer HONDA GX 390 is simple tuned to circa 20 HP...

-the same power G25B 2.5 gear and 1.3 m wooden propeller generates 50 kG thrust
and........many noise !
 

akwrencher

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That sounds interesting, how on Earth do they deal with the rods going through them?


The Koenig engines don’t have or use a supercharger. They have a floating disc under each cylinder that seals the space between the piston and crankcase (like a reed valve) and allows for normal 2-stroke cylinder scavenging
 

TiPi

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I can't find a parts list but if I remember correctly, the conrods were round (tube) and had a guide/follower that kept the passage through the disc below the piston sealed, like a flat-plate valve.
 
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