Lower budget engine options for a low budget UL

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proppastie

Well-Known Member
Log Member
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

Super Moderator
Staff member
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

Well-Known Member
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....

jedi

Well-Known Member
...,...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....
Because it does not fold and store like a Weedhopper.

TiPi

Well-Known Member
Log Member
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

Well-Known Member
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

Well-Known Member
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

Well-Known Member
Log Member
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

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

BBerson

Light Plane Philosopher
HBA Supporter
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

Well-Known Member
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

Well-Known Member
HBA Supporter
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

Well-Known Member
Log Member
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.

Armilite

Well-Known Member
so here go's...…..

I believe simple low budget ultralights like my weedhopper still have a viable place in the market (even more so today with so many prospective pilots being budget limited). A weedhopper can be scratch built for 1k or less in tubing and another $900 for a set of solid color sails, the problem is engine costs in the 25 to 30hp range are 3k plus so now you have invested 5k in a simple easy to construct and fly airplane that has a resale value of around 3.5k. To many budget constrained people this makes no sense whatsoever. John Chotia realized this and created the Chotia 460, 18hp at a price point of$750 and it fit the bill for the weedhopper perfectly, I know as I have 300+ hours sitting behind one! with my 180lb but in the seat, climb was only about 400fpm but it was reliable, sipped gas, and got the job done!

so the question (or challenge) is, what off the shelf engine can be purchased and converted for 1k or less (minus the prop) either direct drive or belt reduction is acceptable as long as the cost of the redrive is factored into the 1k overall cost. all mod work needs to be doable with basic tools (drilling ok but no machining). the end product should be capable of producing 20 to 30 hp. both 2 and 4 stroke options are acceptable.

Chris
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The Specifications (Weedhopper Model 40). Many Engines were used on these, the Rotax 277UL, 377UL, 447UL, 503UL, Kawasaki 340 & 440, etc!
General characteristics
• Crew: one
• Length: 18 ft 6 in (5.64 m)
• Wingspan: 28 ft 0 in (8.53 m)
• Height: 6 ft 97 in (4.29 m)
• Wing area: 168 sq ft (15.6 m2)
• Gross Weight: 550 lb (249 kg)
• Empty weight: 250 lb (113 kg) <== Use a Lighter Engine like a rotax 277F/277UL.
• Useful Load: 300 lbs - 30 lbs GAS = 270 lbs for Pilot.
• Fuel capacity: 5 US gallons (19 litres)
• Powerplant: 1 × Rotax 447 twin-cylinder, two-stroke aircraft engine, 40 hp (30 kW)
550 lbs = 249.4758 kg / 10 kg = 24.94758 kw needed = 33.45526 hp needed. Will it Fly with a Rotax 277UL(26hp@6250rpm), Yes. There was a 277UL also rated 28hp@6400rpm that used a different Exhaust Muffler. IF, you add a 38mm Carb and just find a better Muffler and turn it 6500rpm you can make 30-32hp and with a Tuned Pipe Designed for 6500rpm you can make 38hp. A 277UL Fanner with a Gear drive and Exhaust is 65lbs, the 277UL Free Air is like 60-61lbs. A 277UL with a Belt Drive is usually even Lighter 3 -5 lbs. You can Buy 277F off of Skidoo Snowmobiles for $100-$250. The Sled version can only use a Belt Drive, it doesn't have the O-ring Groove. Could you Weld & machine one, Yes. If you watch eBay, you can pick up a used one with a Gear Drive $250 -$650. Rebuild kits on eBay \$140+. Sled 277 PTO Case vs 277UL PTO version. 277UL's off Scat Hover Craft have CDI.

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Jay Kempf

Curmudgeon in Training (CIT)
Leon Davis...."Mower Power to the People" on the side of the DA-11?
Direct drive 18HP Briggs and Stratton.

Armilite

Well-Known Member
Says it Weighs only 177 pounds empty! With a useful load of 198 pounds - 36 lbs for 6 Gal of Gas = 162 lbs for Pilot & Bags, it has a gross weight of 375 pounds = 170.0971 / 10 kg = 17.00971 kw needed = 22.8104 (23hp) would be a more ideal Power to Weight Ratio. It just says he used an 18 h.p. Briggs & Stratton 4-cycle. I don't see if a Single or Small V Twin. A Stock Duromax 440 Single is (18hp) and can easily make 37hp with upgrades. He is using the Briggs in Direct Drive, a Honda/Clone 460 Single at 3600rpm with upgrades still made 30.68hp, a 440(18hp) Big Block with upgrades would be around 28hp@3600rpm. The Smaller and Lighter and Cheaper Honda GX270 Type (Small Block) with a Redrive might be a better Engine if upgraded to make 18hp-23hp. Preditor also made a 301 Single, a Hybrid GX270 also.

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WonderousMountain

Well-Known Member
Small block V-twin direct drive, and not even with aftermarket
Performance mods. You can see where the cowl goes over the
Orthagonal V. It's that small, that light and that fast. Believe it.

Victor Bravo

Well-Known Member
The obvious answer to the OP's question at this moment would be the Harbor Freight V-twin engine, with a few "aircraft" modifications and tuning. For a 4 stroke engine, it is inexpensive enough that it will win in any contest where you are solving the equation for cost.

pictsidhe

Well-Known Member
Small block V-twin direct drive, and not even with aftermarket
Performance mods. You can see where the cowl goes over the
Orthagonal V. It's that small, that light and that fast. Believe it.
I get 0.3sqft of drag area...

Armilite

Well-Known Member
The obvious answer to the OP's question at this moment would be the Harbor Freight V-twin engine, with a few "aircraft" modifications and tuning. For a 4 stroke engine, it is inexpensive enough that it will win in any contest where you are solving the equation for cost.
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There are Small Block V Twins as Small as 470cc - 627cc and Big Block V Twins. I'm not sure where the HF 670 (22hp) Falls, but I would guess in the Big Block Category at (106 lbs) Dry Weight. The 627cc (23hp) is (77 lbs) Dry Weight. Once you do the Upgrades it is much Lighter, probably comparable to the Rotax 277UL.