DIY Two-Stroke Engine

Nigel Eaton wrote:
In article
,
bizguy writes
You could look at outboard motors as a starting point. In the past I
read of someone using a Mercury to get 100 hp in an aircraft.

That seems unlikely, to be honest. I've never met an outboard that
wasn't cooled by pumped water.



I had a really nice 5 HP Briggs and Stratton outboard on my previous
sailboat. It was air cooled. But it was the exception that proved
the rule...

http://www.duckworksmagazine.com/03/...p/06/index.htm
--

Richard Lamb
http://www.home.earthlink.net/~cavelamb/

cavelamb wrote:
Nigel Eaton wrote:
In article
,
bizguy writes
You could look at outboard motors as a starting point. In the past I
read of someone using a Mercury to get 100 hp in an aircraft.

That seems unlikely, to be honest. I've never met an outboard that
wasn't cooled by pumped water.



I had a really nice 5 HP Briggs and Stratton outboard on my previous
sailboat. It was air cooled. But it was the exception that proved
the rule...

http://www.duckworksmagazine.com/03/...p/06/index.htm

Without knowing anything much about ultralights (beyond they look fun
but dangerous) wouldn't the obvious source of lightweight engines in
that power range be motorcycle engines?

-- Peter Fairbrother

"Peter Fairbrother" wrote

Without knowing anything much about ultralights (beyond they look fun but
dangerous) wouldn't the obvious source of lightweight engines in that
power range be motorcycle engines?

You would think, but how they are designed is a major problem.

Most have the gearbox made as one with the lower crankcase. You can't get
the weight off of the engine, and the gears in the bike tranny are not tough
enough to run a prop, so you have to live with the weight and figure out a
way to get the power out of the case without using the gearbox. Big
problem.
--
Jim in NC

On Sat, 6 Mar 2010 21:36:28 -0800 (PST), bizguy
wrote:

You could look at outboard motors as a starting point. In the past I
read of someone using a Mercury to get 100 hp in an aircraft.
Harold
Had a 100HP Evinrude V4 I was thinking of putting in a plane - untill
I remembered all the problems I'd had with 2 strokes in boats, lawn
mowers, mototcycles, weed-eaters, and chain saws over the years.

"durabol" wrote in message
...
For the last few years I have toyed with the idea of building a
homemade two-stroke engine for UL use. What keyed my interest was
reading about homemade model aircraft engines and reading and watching
a re-enactment of the Wright brother's first flight with a replica
engine (not a two-stroke engine).

Has anyone made a 2-stroke engine from scratch? One may need to cast
aluminium, may need a lathe and milling machine with boring head and
hone or perhaps the boring and honing of the cylinder and bearing
journals could be farmed out. A commercial carburetor and piston could
be used. Two-stroke engines seem simple enough that home construction
may be possible, if not practical.

A direct drive engine will be that much heavier when you take into
account the weight of the drive reduction system. I have calculated
the weight of an 80x80mm bore and stroke 2 cylinder opposed engine and
it was a bit under 40lbs which should give about 1hp/lbs. I used 10mm
cylinder and crankcase wall thickness and a 1.25" dia crank.

I have got some idea of port-time-area from the freeware computer
program called "BiMotion". I'm not sure how good the data is for
lowish speed engines but I guess it is a start. I have also worked up
a spreadsheet for similar information.

I don't think a reed valve system is needed for this engine since it
is only going to operate at a fairly narrow rpm range and the port
timing isn't critical. Piston ported valves offer similar performance
to other induction types but only over a narrow rpm range which is
what I have planned for the engine. I plan to build an engine with a
restrictive exhaust to ensure no fuel escapes. I have heard that
piston ported engines can spit some fuel out of the carb at idle but
this doesn't seem like a major problem. Rotary valves via crank shaft
induction (disk or drum valves as well) is an interesting idea but I
don't think I need the critical timing they provide.

I was planning on using the largest two-stroke piston (not a diesel
piston) I could find and using the largest stoke that was reasonable,
something like 90x105mm

Brock

How about a 2 stroke radial developed by Pontiac for their X-4 1,500lb
car in 1969.
http://www.popsci.com/archive-viewer...lt+airpl anes

Popular Science has just released ALL of their archives for free
http://www.popsci.com/archives and found it while searching for
homebuilt airplanes.

--
A man is known by the company he keeps- Unknown

Anyolmouse

On 8 Mar, 22:28, "Anyolmouse" wrote:
"durabol" wrote in message

...



For the last few years I have toyed with the idea of building a
homemade two-stroke engine for UL use. What keyed my interest was
reading about homemade model aircraft engines and reading and watching
a re-enactment of the Wright brother's first flight with a replica
engine (not a two-stroke engine).

Has anyone made a 2-stroke engine from scratch? One may need to cast
aluminium, may need a lathe and milling machine with boring head and
hone or perhaps the boring and honing of the cylinder and bearing
journals could be farmed out. A commercial carburetor and piston could
be used. Two-stroke engines seem simple enough that home construction
may be possible, if not practical.

A direct drive engine will be that much heavier when you take into
account the weight of the drive reduction system. I have calculated
the weight of an 80x80mm bore and stroke 2 cylinder opposed engine and
it was a bit under 40lbs which should give about 1hp/lbs. I used 10mm
cylinder and crankcase wall thickness and a 1.25" dia crank.

I have got some idea of port-time-area from the freeware computer
program called "BiMotion". I'm not sure how good the data is for
lowish speed engines but I guess it is a start. I have also worked up
a spreadsheet for similar information.

I don't think a reed valve system is needed for this engine since it
is only going to operate at a fairly narrow rpm range and the port
timing isn't critical. Piston ported valves offer similar performance
to other induction types but only over a narrow rpm range which is
what I have planned for the engine. I plan to build an engine with a
restrictive exhaust to ensure no fuel escapes. I have heard that
piston ported engines can spit some fuel out of the carb at idle but
this doesn't seem like a major problem. Rotary valves via crank shaft
induction (disk or drum valves as well) is an interesting idea but I
don't think I need the critical timing they provide.

I was planning on using the largest two-stroke piston (not a diesel
piston) I could find and using the largest stoke that was reasonable,
something like 90x105mm

www.deltahawk.com

Too big for ultralight I would guess but seems like
a very fine plan for a light aircraft engine.

160 hp and upwards

V4 two stroke diesel.

Has crank driven air pump + turbo.

No electrics *at_all* for engine operation.

Will continue running if air pump OR turbo fails.
Will run at about 50% power (check web site for details)
if all water is lost.

Seems a *very* fine thing to me.

Expected to be accepted as a FAA certified
aero engine this year.

200hp planned.

V8 in the future.

On 9 Mar, 03:47, bod43 wrote:
On 8 Mar, 22:28, "Anyolmouse" wrote:



"durabol" wrote in message

...

For the last few years I have toyed with the idea of building a
homemade two-stroke engine for UL use. What keyed my interest was
reading about homemade model aircraft engines and reading and watching
a re-enactment of the Wright brother's first flight with a replica
engine (not a two-stroke engine).

Has anyone made a 2-stroke engine from scratch? One may need to cast
aluminium, may need a lathe and milling machine with boring head and
hone or perhaps the boring and honing of the cylinder and bearing
journals could be farmed out. A commercial carburetor and piston could
be used. Two-stroke engines seem simple enough that home construction
may be possible, if not practical.

A direct drive engine will be that much heavier when you take into
account the weight of the drive reduction system. I have calculated
the weight of an 80x80mm bore and stroke 2 cylinder opposed engine and
it was a bit under 40lbs which should give about 1hp/lbs. I used 10mm
cylinder and crankcase wall thickness and a 1.25" dia crank.

I have got some idea of port-time-area from the freeware computer
program called "BiMotion". I'm not sure how good the data is for
lowish speed engines but I guess it is a start. I have also worked up
a spreadsheet for similar information.

I don't think a reed valve system is needed for this engine since it
is only going to operate at a fairly narrow rpm range and the port
timing isn't critical. Piston ported valves offer similar performance
to other induction types but only over a narrow rpm range which is
what I have planned for the engine. I plan to build an engine with a
restrictive exhaust to ensure no fuel escapes. I have heard that
piston ported engines can spit some fuel out of the carb at idle but
this doesn't seem like a major problem. Rotary valves via crank shaft
induction (disk or drum valves as well) is an interesting idea but I
don't think I need the critical timing they provide.

I was planning on using the largest two-stroke piston (not a diesel
piston) I could find and using the largest stoke that was reasonable,
something like 90x105mm

www.deltahawk.com

Too big for ultralight I would guess but seems like
a very fine plan for a light aircraft engine.

160 hp and upwards

V4 two stroke diesel.

Has crank driven air pump + turbo.

No electrics *at_all* for engine operation.

Will continue running if air pump OR turbo fails.
Will run at about 50% power (check web site for details)
if all water is lost.

Seems a *very* fine thing to me.

Expected to be accepted as a FAA certified
aero engine this year.

200hp planned.

V8 in the future.

Oh yes - direct drive. No gears needed.

Thanks for the responses. I meant for ultralight or light aircraft
with 20-40hp from 1 or 2 cylinders. I definitely want to copy as much
as I can since I'm not engineer. I planned to have the RPM at about
4000 in order to get enough power out of the engine but I may reduce
the rpm if I can get enough power. Also I may have to weld the crank
together to handle the propeller loads.

Brock

durabol wrote:
Thanks for the responses. I meant for ultralight or light aircraft
with 20-40hp from 1 or 2 cylinders. I definitely want to copy as much
as I can since I'm not engineer. I planned to have the RPM at about
4000 in order to get enough power out of the engine but I may reduce
the rpm if I can get enough power. Also I may have to weld the crank
together to handle the propeller loads.

Brock

That RPM isn't going to give you much prop efficiency.

A more spindly engine with higher displacement may be lighter overall --
and certainly mechanically simpler -- than a little fast engine and a
speed reducer.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On Mar 14, 11:30*pm, durabol wrote:
Thanks for the responses. I meant for ultralight or light aircraft
with 20-40hp from 1 or 2 cylinders. I definitely want to copy as much
as I can since I'm not engineer. I planned to have the RPM at about
4000 in order to get enough power out of the engine but I may reduce
the rpm if I can get enough power. Also I may have to weld the crank
together to handle the propeller loads.

Brock

'Restrictive' exhaust isn't a good way to avoid venting unburnt fuel,
and it will really clobber performance. If you're really trying to
get good performance, especially over a narrow band, then you really
need to consider using tuned pipes (AKA "Expansion Chambers"). Gordon
Jennings "Two Stroke Tuners Handbook" covers most everything you need
to design a two-stroke.
4000 RPM is pretty low for a two-stroke. The tuned length for the
pipe(s) would be around 6 FEET.