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Lower budget engine options for a low budget UL

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cpd

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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
 

n3puppy

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20-30hp - but at what max weight for engine and reduction (if not direct) ?
 

jedi

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I accept the 20 to 30 hp but I would like more specifics.

20 hp with fixed pitch prop is likely 18 hp or less for takeoff. Cruise power required would be even less.

I am researching IC/electric power. More specific with 100 pound power package what power/ thrust is required for climb and also for low speed cruise.
 

cpd

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n3puppy, I would say no more than 60 to 80lbs ready to fly.
 

Vigilant1

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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!
We need to remain properly calibrated. If the price for the Chotia was $750 in 1980, the inflation-adjusted price in 2019 would be $2,341.
If, as you say, a Weedhopper has a value of about $3,500, then it may make more sense to buy one at that price than to try to build one for less--unless you just want to build one.
4 stroke industrial engines in the HP you want can be bought for $750-$1000 new in the box and are fuel efficient and very reliable in their intended use. Prop hubs are available for these. But their weight is likely more than you want for this application.
 
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Topaz

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We've had extensive discussions about converting some of the industrial V-twins available now for relatively low prices. Assuming your design is capable of flying safely on ~22 hp, a Predator 670cc V-twin seems to be able to be given a very basic "airplane" conversion for as small a total expenditure as $1,000, although a more-practical conversion that also replaces the carburetor would probably end up closer to $1,200. This presumes you're not trying to increase the power supplied by the engine, but rather make it suitable for airplane use with the original rated power.

The challenge is weight. This type of "basic" conversion probably comes in about 90-95 lbs, plus prop. That's a lot of weight for an ultralight.
 

cpd

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ToddK lol...… mine weighs 227lbs and ill put it on scales in front of anyone day or night, rain or shine....just as long as the wind is calm or she might blow away.

Vigilant1, the challenge is 1k but a reliable powerplant ready to fly for 2k would still hand over fist beat out the current "aircraft specific" market offerings.

im not much for calculation torque etc......but the Chotia 460 turned a 44x19 prop at 3500rpm generating up to 120lbs of thrust on a cold dense air day. whatever is used needs to match or exceed those numbers.

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.
 

mullacharjak

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My friends flew single seat trikes with converted homebuilt engines from a suzuki carry van. The engine was called an LJ50.It was in line three cylinder 2 stroke of 539cc.It turned a similiar prop 44x19 at 3900RPM and gave 135 lbs thrustIt was run open exhaust and weighed 34 kg without prop and radiator.It was a very good engine.The engine is a very old design but still available.
 

addicted2climbing

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HONDA GX390, thauts ...?
That engine and others have been discussed to death in other posts. Search posts by Armlite and prepare to read up.
However while its discussed in length nobody took the leap to build one out and fly it. There are a few videos online of some on trikes though. Also there is a 23hp single that looks promising but with the tarrifs they may not be supported for long. I plan to buy one in new year to play with it.
 

Dana

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Cuyuna 35HP, still readily available used/rebuilt cheaper than Rotax, 85# installed. May or may not come with redrive, if not you gotta figure something out. Kawasaki 340 and 440, I know less about them but similar. Half VW,30-40HP direct drive, also 85# installed. 1/3 Corvair similar but much rarer. Paramotor engines 20-30HP at 20-30#, yeah, they're into the $3K range.

I converted a Kawasaki KX100 dirt bike engine for a paramotor, 25HP, 30#, bought a low time engine from a crashed bike and bartered some machine shop time to convert the bike's original gearbox into a redrive.
 

pictsidhe

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I am intermittently working on a Briggs with redrive. I'd be very pleased if they could be churned out for $2k. Running them direct drive is an option that I am not personally exploring. That would preferably ditch the flywheel, which needs a new ignition and starting system. Could be under 60lb, but power wouldn't be great unless you did some engine mods.
 

mullacharjak

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The Chotia 460 was a very good concept.A large spark ignition model aircraft engine.It still is.Best engine for a weedhopper.I dare saythat the chinese dont know about it or would certainly make a very cheap copy. A twin version of this engine would fly any ultralight.
 

Niels

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Just for my own phantasies.
Will 20 horsepower to a 44 inch prop turning 3600 rpm be usefull and fly one person?
 

mullacharjak

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Just for my own phantasies.
Will 20 horsepower to a 44 inch prop turning 3600 rpm be usefull and fly one person?
Suzuki LJ50 539cc 3 inline 2 stroke direct drive 44inch prop 3900rpm 135lbs thrust has flown a single seat trike.
 
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pictsidhe

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Just for my own phantasies.
Will 20 horsepower to a 44 inch prop turning 3600 rpm be usefull and fly one person?
Depends on the plane. The Quickie flew on 18hp 3600rpm direct drive.
For an ultralight, you'll need more span than the currently popular types such as Minimax.
 

Bille Floyd

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...

I converted a Kawasaki KX100 dirt bike engine for a paramotor, 25HP, 30#, bought a low time engine from a crashed bike and bartered some machine shop time to convert the bike's original gearbox into a redrive.
How much did the engine & drive weigh ? 25-Hp is good for
what i'm looking for.

The two benchmark engines i'm looking at now,for my build , are the
Hirth F-33, and the Vittorazi Moster 185 ; both put out near 28-Hp
and weigh under 35 to 40-Lb, (with the belt reduction / clutch) and they can
make over 160Lb thrust. Both are in the $ 3K range.

I need 25Hp, to get off the ground at the airport i intend to
fly at in Moore Idaho, (5,500 ASL). I will not be using an engine
with reduction , that weighs more than 40-Lb.


Bille
 
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