4360 double Volks?

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Peterson

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I don't know too much about weight, but it seems that VW 2180cc engines are good choices for lots of light sports needing 60-70hp. It seems like the people getting more than that do so by turning small props at higher RPMs.

Could 2 2180cc engines be coupled at the crank and have their carbs and timing synced up to raise their output at lower RPM? If this were to be done, would total weight be competitive for horsepower at 2400-2700 RPMs? Would it be better to couple the cranks at 90 or 180 degrees? (I would think 90 would run smoother, but don't see any obvious detraction to use 180 for simplicity)

Still love the power to weight of the Mazda Remedies, but prop reduction units are a turn off to someone without easy access to a respectable machine shop. Wanting to examine direct drive options for a while.

Thanks.
 

Peterson

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Coming in at approx 248 cu. In., I would expect it to be a closer competitor to an O-235. I don't really know what the weight of one VW is, but using a rubber damped coupling like large air compressors should be straight forward enough to work. Looking for simplicity also.

Peripheral intake, side exhaust Renesis is still my favorite, but without a reputable COTS PRSU for that application, I would like a simple, lightweight, affordable installation. Preferring conversion engine due to lower overhaul cost. Even if I find a great deal on a O-200/235/290/320 the maintenance and labor charges from an A&P would become fairly daunting.
 

ScaleBirdsScott

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A VW weighs in around 175 lbs give or take. So 2 would put you at close to 350, or approx 100 lbs more than an O-320.

And in no way I can see is it simpler... if they work as one engine then you just have one engine with more parts. If it can run as an in-line twin... maybe there's a point there? Except certain failures still hose the whole power plant and still one prop so a traditional twin would at least be more redundancy.

And if the Continental is made uncertified by running on an E-AB isn't it so that you can do your own maint?
 

Daleandee

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Could 2 2180cc engines be coupled at the crank and have their carbs and timing synced up to raise their output at lower RPM? If this were to be done, would total weight be competitive for horsepower at 2400-2700 RPMs? Would it be better to couple the cranks at 90 or 180 degrees? (I would think 90 would run smoother, but don't see any obvious detraction to use 180 for simplicity)
Not sure how far away from your original intent you would care to go but it seems to me that if you're looking for 120-140 HP, good cooling, smoothness, and easy assembly along with reasonable initial cost and replacement parts you might take a look at this:

[video=youtube;3oWDfYWKx7k]https://www.youtube.com/watch?v=3oWDfYWKx7k[/video]

I don't believe you'll get full power at 2700 RPM but that's true with the 2180's also. I have owned and flown both a 2180 VW conversion and now a 3.0 Corvair conversion. I would never go back ...

FWIW,

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
114.9 hours / Status - Flying
 
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TFF

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Those rubber couplings would be spit out in no time. Two engines would be doing their own thing vibration wise and meeting in the middle. one would have a prop hanging off it while the other was free. It would need to be a solid connection and make two engines one.
 

Pops

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A VW weighs in around 175 lbs give or take. So 2 would put you at close to 350, or approx 100 lbs more than an O-320.

And in no way I can see is it simpler... if they work as one engine then you just have one engine with more parts. If it can run as an in-line twin... maybe there's a point there? Except certain failures still hose the whole power plant and still one prop so a traditional twin would at least be more redundancy.

And if the Continental is made uncertified by running on an E-AB isn't it so that you can do your own maint?
With no electrical system, my 1835 cc, 60 hp, VW engine weighs 141 lbs firewall forward. That is prop, engine mount, exhaust, oil cooler, oil lines, etc. A VW long block, that is engine less intake, carb, exhaust, mag and mag drive weighs 116 lbs. A 2180 with the stroker crank in 2 pounds more.

GP list the 2180 cc, 75 hp, flywheel drive VW engine with electrical at 158 lbs.

I believe a double VW engine with electrical could be built at 300 lbs or less.

Flywheel Drive from Great Plains Aircraft!
 
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Peterson

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Corvair is a viable option, although a bit harder to find. Trying to find engines I can rebuild myself for hundreds as opposed to paying sn A&P thousands, so that is probably the biggest factor in this decision. Airframe recommends 125-200 Hp at 350lbs Max engine with prop not to exceed 400lbs. firewall forward, so plenty of options.

Double VW, Corvair, Renesis all could work, just don't want a redrive unless proven design is available. I'm not willing to be a human guinea pig testing the quality of Hank and Bubbas machine shop and microbrewery!
 

TFF

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Going in a homebuilt you can do as much or as little to your certified engine because it is not certified any more.
 

Turd Ferguson

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Could 2 2180cc engines be coupled at the crank and have their carbs and timing synced up to raise their output at lower RPM? If this were to be done, would total weight be competitive for horsepower at 2400-2700 RPMs? Would it be better to couple the cranks at 90 or 180 degrees? (I would think 90 would run smoother, but don't see any obvious detraction to use 180 for simplicity)
I know a homebuilt where 2 VW's were coupled together. It's a helicopter. Since the engines were coupled butt-to-butt, one engine had to have it's direction of rotation reversed. Not sure of the HP output but I do know they turn faster than 2700 RPM, quite a bit faster.

Hummingbird(2).jpg
 

Peterson

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I know a homebuilt where 2 VW's were coupled together. It's a helicopter. Since the engines were coupled butt-to-butt, one engine had to have it's direction of rotation reversed. Not sure of the HP output but I do know they turn faster than 2700 RPM, quite a bit faster.

View attachment 46707
Appears to have intermeshing rotors like a Kaman.

Very interesting and proof of concept, just wish Hp and weight were known
 

Topaz

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Any particular reason for doing coupled engines, as opposed to a twin? If engine-out is a worry, then some kind of centerline twin? Seems like you'd get all the benefit, and little of the complication. YMMV, of course.
 

Peterson

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Any particular reason for doing coupled engines, as opposed to a twin? If engine-out is a worry, then some kind of centerline twin? Seems like you'd get all the benefit, and little of the complication. YMMV, of course.
Wanting to go plans built on someone else's already proven design. Weight and balance already worked for single, although the most notable version of this plane flew with added winglets and a Mazda rotary. These changes are now supported as optional suplimental plans by the designer. If I knew enough about aircraft design to modify it to a twin (VW, Corvair), I would look into it, but I'm still just a freshman at Embry taking core classes so that's too advanced for my level.
 

Turd Ferguson

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Appears to have intermeshing rotors like a Kaman.

Very interesting and proof of concept, just wish Hp and weight were known
It's a deep intermesh twin rotor helicopter. The engines are 1835cc, total power output is 110-115 hp @3500 RPM. If you are an EAA member, there is a feature about the machine in the March 1985 issue of Sport Aviation that may have more details.

https://www.youtube.com/watch?v=Q6mDK9XhklE
 

Peterson

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Just to cover the "why not a twin of you need 2engines to get the power you're needing" question, I emailed the designer as to the possibility of that. No answer yet, but I don't hate the idea (just don't know enough to modify the original design myself)
 
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