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Kitfox Lite and 4ao84 engine

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jkoper

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I have a Kitfox Lite with the original 2si engine. I have been thinking that the 4ao84 and the kitfox could be a fairly good match. Does anyone have any familiarity with the kitfox lite? Would the airframe be able to deal with the extra weight? I know that the 503 was an option on these, but the 4ao84 is about 30# heavier than that. I am a tool and die maker and have a full machine shop at home, I've been wondering if some creative machine work could give the 4ao84 enough of a diet to bring the weight down closer to the half VW range. I've had been waiting for the pegasus o-100 to come to fruition, but it seems stalled. Whats everyone's thoughts?




Jim
 

BBerson

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How would you cut off weight?
I have been looking at cutting the weight on a VW. Was considering replacing the cylinder heads with light simple flat heads.
And operating at reduced power of say 30hp at around 2500rpm . If 100 pounds, might work for an ultralight.
 

don january

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I don'y see trimming 30# of that engine. Might get 13 if lucky, And I think you'd still want 15 more HP
 

JIC

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A 4A084 will weigh about 125lb stripped for aircraft use and with prop.
I don't know how you would shave 30# of a 4A084. You can turn down the pull rope
pulley and save some.

jic
 

johnnyd

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A little "birdie" said not to give up on the O-100 just yet. Things are coming down to the wire for an Oshkosh/Airventure kickoff debut this year.
It's so close that I'm driving 1400 miles to be there.;)

John
 

Dana

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125# for 30-40HP, better to go with an 85# half VW if you don't want a 2-stroke.

Dana
 

BBerson

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125# for 30-40HP, better to go with an 85# half VW if you don't want a 2-stroke.

Dana
It does appear that two cylinders is lighter than four.
A one cylinder engine would be even lighter. The one cylinder 500cc on my mower has a counterweight and runs smooth at 3600rpm. A 1500cc one cylinder would be very light.
 

Dana

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Large displacement single cylinders tend to vibrate a lot, unless they're built heavy.

Dana
 

BBerson

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Large displacement single cylinders tend to vibrate a lot, unless they're built heavy.

Dana
Well, like I mentioned, the Briggs anti-vibration sliding and reciprocating cast iron weight actually works very well.
So why would a similar anti-vibration reciprocating system three times larger not work?

Yes, the power pulses remain. For that, high rpm seems to smooth it out. If that isn't enough then perhaps mounting the engine on bearings on the crankshaft axis would eliminate torque transfer to the aircraft.
Almost like a recoiless cannon. Some snubbers would restrain the rotation. Something like the lead/lag dampers on helicopter.
 

Dana

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Well, like I mentioned, the Briggs anti-vibration sliding and reciprocating cast iron weight actually works very well.
So why would a similar anti-vibration reciprocating system three times larger not work?

Yes, the power pulses remain. For that, high rpm seems to smooth it out. If that isn't enough then perhaps mounting the engine on bearings on the crankshaft axis would eliminate torque transfer to the aircraft.
Almost like a recoiless cannon. Some snubbers would restrain the rotation. Something like the lead/lag dampers on helicopter.
Sliding reciprocating cast iron weights sound heavy, compared to a two (or more) cylinder engine of the same displacement.

High rpm helps... I had a converted 100cc Kawasaki engine on a paramotor and it ran smooth as silk at anything above idle. Even on a two cylinder, power pulses are a problem (at least on 4-strokes without redrives), which is why half VW engines are limited to fixed pitch wood prop.

Mount the engine on a shaft with dampers, yes it'd smooth out the power pulses, but if the engine moves around too much I can imaging it playing all kinds of havoc with the accessories (carburetor, ignition, etc.). A good damper on the crankshaft output would work, too, but again at the expense of weight.

Dana
 

BBerson

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Sliding reciprocating cast iron weights sound heavy, compared to a two (or more) cylinder engine of the same displacement.

High rpm helps... I had a converted 100cc Kawasaki engine on a paramotor and it ran smooth as silk at anything above idle. Even on a two cylinder, power pulses are a problem (at least on 4-strokes without redrives), which is why half VW engines are limited to fixed pitch wood prop.

Mount the engine on a shaft with dampers, yes it'd smooth out the power pulses, but if the engine moves around too much I can imaging it playing all kinds of havoc with the accessories (carburetor, ignition, etc.). A good damper on the crankshaft output would work, too, but again at the expense of weight.

Dana
The 500cc Briggs single with counterweight*is one pound lighter than the Briggs 479cc V-twin
http://www.northerntool.com/shop/tools/product_200621577_200621577
http://www.northerntool.com/shop/tools/product_200161524_200161524

The more important fact might be the cost. The single is larger but half the cost.
That's because a twin is almost two engines siamesed together, so twice the cost.

* counterweight is 6 pounds
 
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Peterson

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Kawasaki and Suzuki both tried large single cylinder motorcycles. 650cc was as big as they could go without unacceptable levels of vibration. Maybe lower prop RPMs would let you go a little larger, but at that point you'd have to build your own since that's about as large a single as I know of on the COTS market.
 

BBerson

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Kawasaki and Suzuki both tried large single cylinder motorcycles. 650cc was as big as they could go without unacceptable levels of vibration. Maybe lower prop RPMs would let you go a little larger, but at that point you'd have to build your own since that's about as large a single as I know of on the COTS market.
But did they try a reciprocating counterweight?
The Briggs single is just as smooth as the twin, as far as I can tell.

The record single motorcycle is around 1500cc. http://www.topspeed.com/motorcycles/motorcycle-news/biggest-single-cylinder-in-the-world-ar58248.html

Hard to kick start. But hand propping an airplane single is no problem. A single normally needs a big flywheel which smooths the pulses but adds weight.
But a prop replaces the flywheel for direct drive, so no flywheel weight.
Airplanes need low rpm which favors large displacement. Motorcycles always have a reduction gear system and are high rpm. Not the same.


Sure, the four cylinder 4ao84 is nice, but apparently too heavy.
 
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DangerZone

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I have a Kitfox Lite with the original 2si engine. I have been thinking that the 4ao84 and the kitfox could be a fairly good match. Does anyone have any familiarity with the kitfox lite? Would the airframe be able to deal with the extra weight? I know that the 503 was an option on these, but the 4ao84 is about 30# heavier than that. I am a tool and die maker and have a full machine shop at home, I've been wondering if some creative machine work could give the 4ao84 enough of a diet to bring the weight down closer to the half VW range. I've had been waiting for the pegasus o-100 to come to fruition, but it seems stalled. Whats everyone's thoughts?




Jim
Did you consider the option of installing a Simonini engine with more power but less weight..?

Simonini RACING - Motori per paramotori, Paramotor engine, Costruttori motori paramotori, Paramotor engine constructors, Motori aereonautici per aerei ultraleggeri, Engine for ultralight aircraft, Motori per trike, Engine for ultralight trike

I've seen a Kitfox IV with a twin cylinder Simonini, it climbed even better than with the 4 stroke Rotax (probably due to having much more power). So maybe a smaller engine might be adequate for your Kitfox Lite, like a Mini 3 engine. It is around 25kg with everything, at 36HP has a static thrust of around 100kgf, at moderate throttle it consumes about 4 to 5 liters an hour.

The 4ao84 engine seems a bit heavy for the Kitfox Lite, and it won't get any better even if you put it on a hard diet.
 
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