4 mower engines.

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Cabover

Well-Known Member
Joined
Oct 17, 2010
Messages
46
Location
Minnesota
I have been following the Beetle Master forum and been a minor contributor. I would like to launch a little offshoot. I know that some of what I offer will be a bit like walking thru a refinery with a lit match looking for my lost keys but hay, call me a pyromaniac!

Here is a little twist on a couple of ideas that get kicked around a lot. There are frequent discussions of simple airplanes, the Evans VW powered, the Bounsall(sp) Prospector a tube and rag VW powered single place and the list of single engine one and two place goes on. Lots of great ideas all trying to solve the need for an inexpensive way to get a pilot and maybe a passenger airborne and still be practical at some specialty like cross country or rugged bush flying (my kind and I'm and unashamed Piper fan!)

One thing that runs in most of the discussions eventually is money. If it costs too much to build you either ain’t going to build it or will never complete it, so either way, you ain’t flying it!

For my purposes I will assume that it will be a single place but feel free to add a passenger and keep your wife from thinking that you did not build it to run off to see your girlfriend! As a single place it falls under the exemption that all you need is a private to fly it. Someone was kind enough to point that out for me here once.

So, here is the premise. Over the years I have been offered many lawnmowers and small engines. Some get scrapped, some get rebuilt, some get re purposed and others collect dust. But with free or cheap, you can’t beat the price! Looking on Craig’s List I can pick up lots of riding mowers for a song especially in the autumn after the leaves are raked and just before the snow flies!

Some time ago I saw an interesting airplane. A sort of minimalist low wing that was built mostly to punch holes in the sky as I don’t think it carried enough fuel. It was powered by a Briggs and Stratton (I think) twin cylinder, worked over lawn mower engine. It had some nose art which read: “Mower power to the people”, if I recall.

So, spend some time carving your own props, it was done in the early days. Just take your time. I figure about 36 cans of beer per prop and let mama scream about the sawdust!

Now work over 4 of a kind or 2 pairs of modern twin cylinder lawnmower engines. These run anywhere from about 18 to 36 HP each. They tend to be a little heavy. Stripped of generators, shrouds, governors and maybe a trip to a vertical mill to shed some unused bolt bosses and a general cleanup. Add a nice straight pipe they might get a little lighter and gain a bit of power.

So let’s figure on circa 25hp each. Just round figures for a SWAG. To be a reasonable power for my purposes I’ll need 3 of them and preferably 4. So, 75 or 100 HP.

After following the discussion on the Beetle Master some things became obvious. A twin can get ugly to be in with an engine out depending on design and loading. A single would be safer, I guess it makes a pilot pick a spot instead of trying to work the long glide. So to my premise, as the number of engines goes up the chances of frailer also go up. Here is the question: Do the consequences of a single engine out go up with the number of engines?

Here is the logic that tells me no, the consequences of a single engine frailer go down. The remaining power is either 66% or 75%! (We’ll ignore drag/stopped prop and such for now) Those are cruise power settings!

So what would a quad grass eater look like? A B-17? Classic and it works. Engines 1 and 4 have a long moment arm so a BIG rudder! A Ford Tri-Motor layout and the moment arm is shorter but 66% rather than 75% power after an engine out. I like that Beetle Master, but, let’s give it a twist. One in front one behind and one on each wing. No long arms for asymmetric thrust. Only 25% of total power worst case lost, assuming there is no double engine frailer planned for. Assume that the clime will be negative with 2 engines out. I plan on a single place so that should simplify the W&B and seating interaction part of the design.

So, here is the first spitball! Tube and rag push pull plus, single boom, 4 grass eaters per above. Tail drager and keep the gear legs out of the prop blast as much as possible. Some bigger and softer tires, maybe from a golf cart ( I like the price ) and reasonable tank sizes to get you somewhere. Seems to me it would have performance numbers about like a PA-11 with perhaps a bit higher speed (+/- given some design choices) and longer range.

So, could this be every-man’s entry level single place home built on a shoe string? Add folding wings for the garage storage guys. Does it make sense or should I stop going on those long field trips to where the funny green weeds grow?

Cabover
 

JamesG

Well-Known Member
Joined
Feb 10, 2011
Messages
2,408
Location
Columbus, GA and Albuquerque, NM
You pay a weight penalty for all the extra structure for the various engine mounts, control/fuel lines, etc. Not to mention the sheer complication of multi-engines. A single engine is more efficient than lots of little ones. You'll come out ahead by digging a appropriate car motor out of a junk yard and doing a conversion of that instead.

That being said, if you really want to do it, it should be interesting. You ought to track down and pick the brain of the guy who built a third scale B-17.
 

kent Ashton

Well-Known Member
Joined
Aug 15, 2008
Messages
800
Location
Concord, NC
Over the years I have been offered many lawnmowers and small engines. Some get scrapped, some get rebuilt, some get re purposed and others collect dust. But with free or cheap, you can’t beat the price! Looking on Craig’s List I can pick up lots of riding mowers for a song especially in the autumn after the leaves are raked and just before the snow flies!
Yeah it sounds like a fun thing to try but it'd be a nightmare to execute. Sort of a "Moller Skycar" idea with folding wings and run-out engines. :)
TechFuture: Hold On! Paul Moller's Skycar Is Coming | Bill_Robinson

"Everman's airplanes": A Hummel or Teny-two with a half-VW
 

cheapracer

Well-Known Member
Log Member
Joined
Sep 8, 2013
Messages
6,421
Location
Australian
Run the 4 engines to a single shaft (that the prop is on) each through a sprag clutch or ratchet drive or centrifugal clutch, etc. - any engine fails, it's drive disconnects safely and the others keep driving the shaft.

Or turn the TV on and watch Survivor.
 

Highplains

Well-Known Member
Joined
Jun 2, 2014
Messages
385
Location
Over the Rainbow in Kansas, USA
I have no multi engine experience in full scale, but have flown a number of RC models with twins, quads, and one 8 engine monster. Twins are tricky, lose an engine and you got a problem. But the lost of an engine on a quad was a non-issue, so much so that I would fly it low and slow without concern.

So bottom line, I think it would work, though it might have a slight weight penalty.
 

Aviatorzaki77

Member
Joined
Nov 24, 2014
Messages
15
Location
Hyderabad Telangana / India
pecifications:
  • Type: 2 Stroke
  • Bore: 55mm
  • Stroke: 42mm
  • Displacement: 200CC
  • Power: 23HP/8000rpm
  • Compression Ratio: 10:1
  • Reduction Ratio: 1:2.7
  • Transmission Type: Belt
  • Starting Type: Electrical Start
  • Net Weight (without muffler): 10.3 Kg
  • Premium Muffler Weight: 2.2 Kg
  • Spark Plug: DLE-8A
  • Petrol: 93#, 97#
  • Alternator Output: 14V 1A
  • Premium Alternator Output: 14V 4A
  • Propeller: 1220mm
  • Applicable Pilot Weight: 120Kg

Aliexpress.com : Buy New Arrival DLE200 DLE 200CC Gasoline Engine for Paramotor ( Standard Muffler Version) from Reliable engine mercury suppliers on CBAHobby Co., Ltd | Alibaba Group
 

Cabover

Well-Known Member
Joined
Oct 17, 2010
Messages
46
Location
Minnesota
Yeah it sounds like a fun thing to try but it'd be a nightmare to execute. Sort of a "Moller Skycar" idea with folding wings and run-out engines. :)
TechFuture: Hold On! Paul Moller's Skycar Is Coming*|*Bill_Robinson

"Everman's airplanes": A Hummel or Teny-two with a half-VW
Parts to overhaul a B&S and about any other engine I have worked on are not expensive in comparison to LicCon parts electroplated with unobtainium. When well maintained they fail infrequently, perhaps with less failure rate than a LiCon fire breather.

Cabover
 
Last edited:

Cabover

Well-Known Member
Joined
Oct 17, 2010
Messages
46
Location
Minnesota
Run the 4 engines to a single shaft (that the prop is on) each through a sprag clutch or ratchet drive or centrifugal clutch, etc. - any engine fails, it's drive disconnects safely and the others keep driving the shaft.

Or turn the TV on and watch Survivor.
Sounds interesting. What layout would get a balance? Would it look about like a PA-11? Might be a bit nose heavy. Could always set the wings a bit more forward... Yea! Might work!
 

BBerson

Light Plane Philosopher
Joined
Dec 16, 2007
Messages
15,542
Location
Port Townsend WA
No doubt it could be done. But four singles vibrate much worse than one four cylinder engine.
The odd sounds and vibration is annoying. I built a twin engine motorglider with a pair of single cylinder mower engines

Much of the weight is starters and flywheels.
 

Cabover

Well-Known Member
Joined
Oct 17, 2010
Messages
46
Location
Minnesota
No doubt it could be done. But four singles vibrate much worse than one four cylinder engine.
The odd sounds and vibration is annoying. I built a twin engine motorglider with a pair of single cylinder mower engines

Much of the weight is starters and flywheels.
Sounds interesting. So the weight of starters and flywheels on a per cylinder basis goes down with an increase in the number of cylinders? If so that, would seem to imply designing an engine block or case that accommodated some reasonably priced Briggs upper end parts. Might increase the initial cost but the overhauls should be reasonable. Making it a production item would have a couple of problems. Briggs would not like the liability and the firs time they change the design the support and future production would be a problem, yet VW bug engines are still around.

Worth a long thought!
 

bmcj

Well-Known Member
Joined
Apr 10, 2007
Messages
14,013
Location
Fresno, California
Top