# Lower budget engine options for a low budget UL

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#### BBerson

##### Well-Known Member
HBA Supporter
My GX 670 is direct drive, four stroke. Was $1100, I think. Weighs 82 pounds with the flywheel still installed, no starter. Could be around 70 pounds with no flywheel. The Briggs 810 is lighter and around$900.

#### n3puppy

##### Well-Known Member
Can you guys help me out here - Not a prop, pitch,thrust kinda guy.
The original poster - CPD - has a known aircraft design - Weedhopper.
Looking for a current replacement for the standard original engine that was sufficient for flight
Chotia 460
18Hp
3500rpm
44x19 direct drive prop
120lbs static thrust
Replacement max weight. - 80lbs
Target ready to fly price $1000 Other than the recently discussed potential price increase and single source supply- Why wouldn't the$900 Vegas carts 23hp engine swinging the same 44x19 prop at 3600rpm be an off the shelf solution ?

Hp, RPM, weight, price seem to fall in line with what he is asking - Plus he gets electric start vs the original hand prop only Chotia 460

Just not sure if that same 44x19 prop when used on a 23hp 4 stroke has comparable performance to the 18hp two stroke it was used on originally.

#### Vigilant1

Other than the recently discussed potential price increase and single source supply- Why wouldn't the $900 Vegas carts 23hp engine swinging the same 44x19 prop at 3600rpm be an off the shelf solution ? A 625cc 4-stroke can be expected to be running some high CHTs if it is really producing 23HP. And the single cylinder driving that prop will be a lot more vibration and greater stresses on the crank than a 2 cylinder. Some folks probably think it will work. #### n3puppy ##### Well-Known Member A 625cc 4-stroke can be expected to be running some high CHTs if it is really producing 23HP. And the single cylinder driving that prop will be a lot more vibration and greater stresses on the crank than a 2 cylinder. Some folks probably think it will work. So the single cylinder 4 stroke will be significantly more stress/vibration than the 460cc Single Chiota? Definitely can see where the CHT will be higher #### Vigilant1 ##### Well-Known Member Lifetime Supporter As a 2 stroke, the engine will have a power stroke every revolution of the crank. A four stoke will have a power pulse every 2 revolutions. So, if they are making the same HP at approx the same RPM, the pulses from the 4-stroke have more magnitude and are less frequent. (ETA: Fixed to reflect proper ratio of revs to power strokes. Thanks, poormansairforce!) Last edited: #### n3puppy ##### Well-Known Member As a 2 stroke, the engine will have a power stroke every other revolution of the crank. A four stoke will have a power pulse every forth revolution. So, if they are making the same HP at approx the same RPM, the pulses from the 4-stroke have a lot more magnitude and are a lot less frequent. Got it - makes sense. #### pictsidhe ##### Well-Known Member A small block Briggs v twin is likely about the same weight as the vegas carts engine and isn't being run past it's design power for 23hp. Lose the flywheel and starter and you may be under 50lb with a prop hub on the Briggs. Carts don't run sustained high power. Many industrial engines are hooked up to water pumps at a high proportion of max power and run for thousands of hours. Go past design power and use it, life is likely going to be short. #### Topaz ##### Super Moderator Staff member Log Member 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 airframe. Weight and span. Can it be done? Yes. Can it be done reasonably? Very likely. #### poormansairforce ##### Well-Known Member As a 2 stroke, the engine will have a power stroke every other revolution of the crank. A four stoke will have a power pulse every forth revolution. We all know what you meant but you may want to edit this. #### Vigilant1 ##### Well-Known Member Lifetime Supporter We all know what you meant but you may want to edit this. Yes, thanks. I fixed it. #### addicted2climbing ##### Well-Known Member Log Member 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
Bille,

If your considering the Moster 185 than in stock form it can only be used as a pusher. I asked Vitorazzi if it could be used as a tractor with the redrive and they said no way and did not anticipate thrust loads as a tractor in the design. I have a Moster 185 on the Zigolo and it is indeed very light.

#### mullacharjak

##### Well-Known Member
Can you guys help me out here - Not a prop, pitch,thrust kinda guy.
The original poster - CPD - has a known aircraft design - Weedhopper.
Looking for a current replacement for the standard original engine that was sufficient for flight
Chotia 460
18Hp
3500rpm
44x19 direct drive prop
120lbs static thrust
Replacement max weight. - 80lbs
Target ready to fly price $1000 Other than the recently discussed potential price increase and single source supply- Why wouldn't the$900 Vegas carts 23hp engine swinging the same 44x19 prop at 3600rpm be an off the shelf solution ?

Hp, RPM, weight, price seem to fall in line with what he is asking - Plus he gets electric start vs the original hand prop only Chotia 460

Just not sure if that same 44x19 prop when used on a 23hp 4 stroke has comparable performance to the 18hp two stroke it was used on originally.
No weedhopper is using the cart engine that you mention so looks like it is not even close to the Chotia 460 engine.

#### Bille Floyd

##### Well-Known Member
Bille,

If your considering the Moster 185 than in stock form it can only be used as a pusher. I asked Vitorazzi if it could be used as a tractor with the redrive and they said no way and did not anticipate thrust loads as a tractor in the design. I have a Moster 185 on the Zigolo and it is indeed very light.
Thanks for that advise ; and a pusher is Fine !
I wonder if the same is true ,for the redrive, on the Hirth F-33 ; my "Other"
possible choice ? I'm going Pusher anyway ; was just curious .

What size prop did you use, with the moster 185 ; the pitch would
be different than what they use with a PG , i think ?

Bille

Last edited:

#### pictsidhe

##### Well-Known Member
Polini Thor engines are OK for tractor use. Not cheap, though.

#### pictsidhe

##### Well-Known 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.
It would need a supercharger. 3x a single for power. With a supercharger, you could drop the RPM a bit and still have 60hp. A flat twin would be good. Much less vibration than a single and won't need the supercharger that a radial does.

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