Engine Desing

Experimental builders have no reason to complain about Lycoming
prices, because no law makes them use them.

wrote:
The Harley Davidson engine is a copy of the 1898 or so De
Dion-Bouton.
HD didn't originate it, and there is no way in hell they can keep
anyone else from building a v-twin engine. They lost their essential
point.

As I recall, the Japanese were not imitating the engine, only the
sound. The plan was to mimic the sound electronically.

--

FF

Rob Turk wrote:
"Matt Whiting" wrote in message
...
Sport Pilot wrote:
Most flat fours are not a boxer, and many twins are not. A boxer
engine will weigh and cost more. It's not really needed on a flat four
anyway, as on a non boxer the pistons on the front and rear pair will
be going opposite directions


True, but this doesn introduce a "rocking couple" vibration mode. There's
no free lunch WRT to engine design. :-)

Although some configurations come close (I-6, V-8, etc.)


Matt

A very interesting design is the Diesel Air engine (www.dair.co.uk). They
have two pistons per cylinder, moving in opposite directions. The ignition
happens in the center of the cylinder, which is also the center of the
engine. All forces that can cause vibration are supposed to cancel eachother
out, so there's a minimum of vibration. The engine has two cranks which are
mechanically coupled on the outside to bundle the power to the prop.
Pictures are on their site.

Rob

Two pistons per cylinder, one piston and two cylinders, etc. It has
been done before.

Bob, Last time I took apart a VW, and Corvair, they shared the same con
rod. Not sure about aircraft engines, but pretty sure the one in the C
150 and the C 172's are not boxers. So I think you have the definition
right, just misinformed about the commanality of boxer engines. They
are uncommon enough that the manufacture makes a deal about the engine
if it is a boxer, such as Ferarri, and BMW(?).

Sport Pilot wrote:
Bob, Last time I took apart a VW, and Corvair, they shared the same con
rod. Not sure about aircraft engines, but pretty sure the one in the C
150 and the C 172's are not boxers. So I think you have the definition
right, just misinformed about the commanality of boxer engines. They
are uncommon enough that the manufacture makes a deal about the engine
if it is a boxer, such as Ferarri, and BMW(?).

My bad, the VW is a boxer, not sure about the Corvair.

On 27 May 2005 08:47:23 -0700, "Sport Pilot"
wrote:

Bob, Last time I took apart a VW, and Corvair, they shared the same con
rod. Not sure about aircraft engines, but pretty sure the one in the C
150 and the C 172's are not boxers. So I think you have the definition
right, just misinformed about the commanality of boxer engines. They
are uncommon enough that the manufacture makes a deal about the engine
if it is a boxer, such as Ferarri, and BMW(?).

I've never given this much thought before. Which design is called a
boxer engine? Let's keep it simple and talk about a twin cylinder
engine. Is the design in which the connecting rods share the same
journal the boxer, or is it the design in which the two connecting
rods have their own throw and own journals. This second type seems
like it would require greater cylinder offset in order to accomodate
the crankshaft throws, and would probably vibrate more.

So which is considered the boxer design? Is the other design simply
called "horizontally opposed"?

Thanks, Corky Scott

Sport Pilot wrote:
Bob, Last time I took apart a VW, and Corvair, they shared the same con
rod. Not sure about aircraft engines, but pretty sure the one in the C
150 and the C 172's are not boxers. So I think you have the definition
right, just misinformed about the commanality of boxer engines. They
are uncommon enough that the manufacture makes a deal about the engine
if it is a boxer, such as Ferarri, and BMW(?).


Sharing the same con rod is quite a feat of design. How did they do
that and still get the crank to spin. Oh, you meant shared the same
crank journal... :-)


Matt

Corky Scott wrote:

On 27 May 2005 08:47:23 -0700, "Sport Pilot"
wrote:


Bob, Last time I took apart a VW, and Corvair, they shared the same con
rod. Not sure about aircraft engines, but pretty sure the one in the C
150 and the C 172's are not boxers. So I think you have the definition
right, just misinformed about the commanality of boxer engines. They
are uncommon enough that the manufacture makes a deal about the engine
if it is a boxer, such as Ferarri, and BMW(?).


I've never given this much thought before. Which design is called a
boxer engine? Let's keep it simple and talk about a twin cylinder
engine. Is the design in which the connecting rods share the same
journal the boxer, or is it the design in which the two connecting
rods have their own throw and own journals. This second type seems
like it would require greater cylinder offset in order to accomodate
the crankshaft throws, and would probably vibrate more.

So which is considered the boxer design? Is the other design simply
called "horizontally opposed"?

Horizontally opposed is the configuration of the cylinders. Boxer means
that the pistons go towards the crank and away from the crank in unison.


Matt

Earlier, Sport Pilot wrote:

My bad, the VW is a boxer, not sure about the Corvair.

Here's a picture of the Corvair crankshaft from William Wynne's Fly
Corvair site:

http://www.flycorvair.com/crank.jpg

I count ten journals on that crank (not counting the stuff forward of
the cam drive gear or aft of the distrubutor drive gear). Since it's a
six cylinder car, I have to assume that four of those (the first,
fourth, seventh, and tenth) are mains that ride in bearing shells in
the crankshaft. That leaves six journals for the connecting rods; to my
way of thinking that means that the con rods are not sharing journals.

As to whether it's a true "boxer," it looks to me like it is. I think
that the photo shows that the rod journals in each opposing cylinder
pair are separated by 180 degrees. That shows most clearly in the rod
journal pair near the bottom of the photo. Since its a 6-cylinder
engine the different pairs are separated from each other by 120
degrees, so the other pairs are at odd angles to the photo perspective.

As for the Lycoming, this drawing from the Sacramento Sky Ranch
(thanks, Mr. Schwaner!) shows seven journals, of which three (including
the long one behind the prop flange) are mains and four are rod
journals:

http://www.sacskyranch.com/lyc_crank_gear.jpg

And again, the rod journals of each opposing cylinder pair are
separated by 180 degrees.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24