Aviation Forum / General / Homebuilt / April 2010

Suzuki built but never raced a 3 cylinder 50cc engine that was rated at
the highest output per liter on record for use with pump gas.  However
to get to one liter it would have 60 cylinders...

Tony

<SNIP>

Worth noting:

there is a radial project out there with quite a few builders that
uses VW jugs and a custom crankcase and heads. Around 100hp if I
remember correctly.

There are also a couple of half VW engine projects with plans
available.

If you take a stroll around the national air and space museum you will
get a feel for the art that went into many of the early engines. The
old designers and machinists were a different breed, and their work
inspires awe in any mechanically inclined mind. It is worth noting
that many of the older radial and fan engine configurations used a pie-
wedge style crankcase, where the cylinder and the case were a single
piece, and the crankcase bolted together in pieces arranged in
circumference to the crankshaft.

With modern alloys and machining techniques, I've wondered if
returning to this style might be tolerable for a small engine today.
Lawn mowers are done similarly, and so I'd imagine an engine designed
in this fashion would scale up quickly from a production standpoint.

While building a new engine solely for art is a lofty goal, I can't
really see it for any other reason.  What performance specs could you
be looking for that aren't currently available in a production engine,
or are not otherwise achievable by making minor modifications to a
production engine?

The engine of interest to me lately is the new subaru TDI boxer
motor.  Wow that thing is fancy, and I'm hoping it makes its way to
the states some time soon.  With modern boosting techniques I'd also
like to see the packard aero diesel configuration revisited, perhaps
integrating some of the features in the elsbett engines. .

If I was heading off in the scratch built direction, I would outsource
the casting process. There are many shops domestic and overseas that
can do short runs of castings based on a provided dxf file. It is
unlikely that a backyard foundry will ever get close to the level of
detail these shops can create. I would probably search far and wide
before starting to CAD the thing up.

Of course, thinking down the road, if ever I should build my own bird,
I'm thinking Rotec, or PZL Franklin. I'd like to go heavy kung fu into
engine design, but it is just way to much work, for way to little
optimization.

Thanks!

I think all engine-driven aircraft have a window
of vulnerability on takeoff.  Most general aviation
planes can't return to the runway straight ahead
and successfully land if they are higher than 200'
and can't turn around to return to the field unless
they are higher than 500'.  Consider that the headwind
that you took off into is now a tailwind and you
can see how badly your day gets.

That's why takeoffs are *always* full throttle and
best rate of climb.  You spend the least amount
of time getting through that zone.

Don't know.  I was told that by someone whose knowledge
and experience were much greater than mine.

Don't know for sure.  I think the combination of
light weight and high drag bleeds off the airspeed
so quickly that you loose elevator authority
before you can put it to use.

...

There are: Powered parachutes.[1]

Almost certainly other types of ultralights don't exhibit that issue
either, too. (Discounting even ultralight airships.) I suspect Jim
Stewart's source was generalizing a wee bit too much.

[1] http://www.quakerstatepoweredparachutes.com/engine_failure.htm

That's a heavier aircraft than an ultralight...not sure what they do
with ultralights, or light sport...anybody know about certs for those
two Categories/Classes?

Government stupidity came first.  Al G. just wanted to bring it to the
general public .................
===============
Leon

No, this is mis-information.

The statement that anything that flies has to be certified by FAA is
categorically incorrect - as several have pointed out here.

Homebuilts are not certified at all.
Not approved, either.

a certificate of airworthiness is is not the same thing as a certified
design.  Actually, the correct term is certificated, not certified.

The statements that started all this (top) i believe are from the model
community(?).  They are certainly not from someone why knows anything
about experimental amateur built aircraft.

and I must remember to read what is written after the first coffee of the
day 'DOH
your correct, the EAA will have a lot of information on homebuilt and
experimental A/C, they will also want you to get regular inspections during
the construction, even on experimental I think, and at various benchmarks
during the build.
personally I wouldn't fly with any home made engine, and by home made I'm
talking about things like casting your own cylinders etc, why re-invent the
wheel when there is a plethora of R&D'd engines that can more easily and
cheaply be converted.

Don't most newer Briggs engines use AL
or pot metal block/cylinders?

There's an interesting Wikipedia article on the origins of the Chevy
Vega.  Apparently it was designed by GM corporate engineering, and
shoved down Chevy's throat.  Chevy wasn't allowed to make _any_
engineering changes, they were very grudging about building the thing,
and that was a huge part of the problem.

Apparently the wear point on the Vega engine wasn't the cylinder walls
at all -- it was the valve guides*.  But the oil leakage** got blamed on
the cylinder walls because who could believe in an aluminum cylinder
bore?  For it's size it's certainly a damn strong engine.

* Which were as new and innovative as the rest of the engine, just
wrong.  If you're going to make something that's new and innovative,
identify the parts that _need_ to be new and innovative, and do the
_rest_ of the thing with old reliable technology.  Then when that works,
go back and innovatize the rest of the thing, one system element at a time.

** "Fill er up and check the gas while you're at it!"