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DIY Two-Stroke Engine Construction Methods



 
 
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  #1  
Old March 10th 10, 07:45 AM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
durabol[_2_]
external usenet poster
 
Posts: 13
Default DIY Two-Stroke Engine Construction Methods

The two main methods for homebuilt construction would be casting vs.
machining or some combination of both (probably the best option).
Forging probably isn't appropriate for home construction (either the
piston or connecting rod).

One method I have thought of is to produce a wax model of the engine
with molds (to a fairly high tolerance to minimize machining) which is
then cast using lost wax casting techniques. I planned to have an
integral cylinder head/cylinder/half the crank case (this is for an
opposed style engine). The only bolts would be to bolt the two halves
together.

A completely machined engine would need a large block of aluminium to
start with which I'm not sure how practical that would be. Perhaps
lost foam casting could be used as a general model of the engine was
made in foam and then cast and the resulting casting could be
machined.

Brock
  #2  
Old March 10th 10, 01:17 PM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
Jim Wilkins
external usenet poster
 
Posts: 57
Default DIY Two-Stroke Engine Construction Methods

On Mar 10, 1:45*am, durabol wrote:
...
One method I have thought of is to produce a wax model of the engine
with molds (to a fairly high tolerance to minimize machining) ...
Brock


What machine tools do you have?

Some WW1 engine cylinders were machined from SOLID steel forgings.
Casting can easily have internal voids unless well designed, because
the metal shrinks as it solidifies inwards. Aluminum is easy enough to
melt that you could cast a simple shape and then test it for strength
or cut it apart.

Or you could make a lawnmower engine and see how durable it is.

jsw
  #3  
Old March 10th 10, 02:24 PM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
basilisk
external usenet poster
 
Posts: 2
Default DIY Two-Stroke Engine Construction Methods


"durabol" wrote in message
...
The two main methods for homebuilt construction would be casting vs.
machining or some combination of both (probably the best option).
Forging probably isn't appropriate for home construction (either the
piston or connecting rod).

One method I have thought of is to produce a wax model of the engine
with molds (to a fairly high tolerance to minimize machining) which is
then cast using lost wax casting techniques. I planned to have an
integral cylinder head/cylinder/half the crank case (this is for an
opposed style engine). The only bolts would be to bolt the two halves
together.


Most two strokes are single cylinder that rely on crankcase pumping
action to move the fuel/air mixture, if you go to a multiple opposed
cylinders, you will have to provide a slave cylinder or roots type blower
to move the air.

basilisk


  #4  
Old March 10th 10, 02:31 PM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
Lloyd E. Sponenburgh
external usenet poster
 
Posts: 2
Default DIY Two-Stroke Engine Construction Methods

"basilisk" fired this volley in news:J4Nln.198564
:

you will have to provide a slave cylinder or roots type blower
to move the air.



Some variants use a cylinder skirt with reed valving.

LLoyd
  #5  
Old March 10th 10, 02:42 PM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
Lloyd E. Sponenburgh
external usenet poster
 
Posts: 2
Default DIY Two-Stroke Engine Construction Methods

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

"basilisk" fired this volley in

news:J4Nln.198564
:

you will have to provide a slave cylinder or roots type blower
to move the air.



Some variants use a cylinder skirt with reed valving.

LLoyd


That didn't come out right... They use a "divider" or partition of sorts
at the journal between con-rods, and reed valving for intake on each side
of the divider. The "skirt" just extends across the whole crankcase.

LLoyd

  #6  
Old March 10th 10, 02:58 PM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
basilisk
external usenet poster
 
Posts: 2
Default DIY Two-Stroke Engine Construction Methods


"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"basilisk" fired this volley in news:J4Nln.198564
:

you will have to provide a slave cylinder or roots type blower
to move the air.



Some variants use a cylinder skirt with reed valving.

LLoyd


You're right, I didn't really consider that before posting.

I supposed it could be worked out but that looks hard to
do in a completely bottom assembled engine, just my 2 cents worth,
I'm not an engine specialist.

basilisk


  #7  
Old March 10th 10, 04:41 PM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
[email protected]
external usenet poster
 
Posts: 5
Default DIY Two-Stroke Engine Construction Methods

In article , "basilisk" wrote:

"durabol" wrote in message
...
The two main methods for homebuilt construction would be casting vs.
machining or some combination of both (probably the best option).
Forging probably isn't appropriate for home construction (either the
piston or connecting rod).

One method I have thought of is to produce a wax model of the engine
with molds (to a fairly high tolerance to minimize machining) which is
then cast using lost wax casting techniques. I planned to have an
integral cylinder head/cylinder/half the crank case (this is for an
opposed style engine). The only bolts would be to bolt the two halves
together.


Most two strokes are single cylinder that rely on crankcase pumping
action to move the fuel/air mixture, if you go to a multiple opposed
cylinders, you will have to provide a slave cylinder or roots type blower
to move the air.

basilisk


my kawai h2 uses reeds and i believe has opposed cylinders. it ain't no
lawnmower.....
  #8  
Old March 10th 10, 04:46 PM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
[email protected]
external usenet poster
 
Posts: 5
Default DIY Two-Stroke Engine Construction Methods

In article , "basilisk" wrote:

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
.3.70...
"basilisk" fired this volley in news:J4Nln.198564
:

you will have to provide a slave cylinder or roots type blower
to move the air.



Some variants use a cylinder skirt with reed valving.

LLoyd


You're right, I didn't really consider that before posting.

I supposed it could be worked out but that looks hard to
do in a completely bottom assembled engine, just my 2 cents worth,
I'm not an engine specialist.

basilisk


it's not so hard, it just costs a bit more. but it adds a lot of grunt.
the 750 i have puts out almost 90hp. dragster h2's running exotic fuels have
been dynoed at over 400hp!. they need to be rebuilt often, but what drag motor
doesn't.
the quest for hp is expensive but doable. honda built a tt racer that got 18hp
out of 50cc! the 8 speed gearbox got it up to 100mph.
read about the mv augusta racers, you wouldn't believe me.
  #9  
Old March 10th 10, 06:37 PM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
Tim Wescott
external usenet poster
 
Posts: 15
Default DIY Two-Stroke Engine Construction Methods

durabol wrote:
The two main methods for homebuilt construction would be casting vs.
machining or some combination of both (probably the best option).
Forging probably isn't appropriate for home construction (either the
piston or connecting rod).

One method I have thought of is to produce a wax model of the engine
with molds (to a fairly high tolerance to minimize machining) which is
then cast using lost wax casting techniques. I planned to have an
integral cylinder head/cylinder/half the crank case (this is for an
opposed style engine). The only bolts would be to bolt the two halves
together.

A completely machined engine would need a large block of aluminium to
start with which I'm not sure how practical that would be. Perhaps
lost foam casting could be used as a general model of the engine was
made in foam and then cast and the resulting casting could be
machined.


Don't sneer at sand castings, particularly for aluminum parts. Rods and
pistons can be made from billet, or can be purchased from racing parts
suppliers -- racers often customize these parts, so if you can find an
engine with e.g. a similar rod you can order one from Carillo or whoever
"yea, I want a Honda XYZ rod, but make it 5" center to center and make
the big end take a bearing from a Kumatsu 30HP diesel".

For an absolutely "I'm only gonna build one ever" engine you could
fabricate the rough parts by welding or brazing, then stress relieve,
then machine. This is, I believe, how railway locomotive and ship
engines are often built, and I believe that there were automotive
engines built this way, too.

You're building an aero engine, right? And it's going to be air cooled,
right? If so, the advantages of separate cylinder assemblies probably
outweighs the disadvantages of trying to build a monoblock engine.
Trash a cylinder on a monoblock engine and you have to do a complete
rebuild. Trash one cylinder on an assembled engine and you just have to
replace one part.

Another of the advantages of separate cylinders is that you can build a
one-cylinder "research engine" to get the myriad of details worked out.
Then when you like the porting and combustion chamber shape and
cooling fin layout and piston design and ring lands and cylinder finish,
and etc., you can build the multi-cylinder engine of your choice.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
  #10  
Old March 10th 10, 07:08 PM posted to rec.aviation.homebuilt,rec.aviation.ultralight,rec.crafts.metalworking,rec.models.scale,uk.rec.models.engineering
Jim Stewart
external usenet poster
 
Posts: 437
Default DIY Two-Stroke Engine Construction Methods

durabol wrote:
The two main methods for homebuilt construction would be casting vs.
machining or some combination of both (probably the best option).
Forging probably isn't appropriate for home construction (either the
piston or connecting rod).

One method I have thought of is to produce a wax model of the engine
with molds (to a fairly high tolerance to minimize machining) which is
then cast using lost wax casting techniques. I planned to have an
integral cylinder head/cylinder/half the crank case (this is for an
opposed style engine). The only bolts would be to bolt the two halves
together.

A completely machined engine would need a large block of aluminium to
start with which I'm not sure how practical that would be. Perhaps
lost foam casting could be used as a general model of the engine was
made in foam and then cast and the resulting casting could be
machined.


I went back and read your first post to try to
get the big picture here. So what I think you
are saying is that you want to build an engine
that will be roughly equivalent to a Rotax 2-stroke
ultralight engine. I think the best advise I
could give you is don't. Despite the fact that
the Rotax engines are meticulously designed and
built, they still fail and have a 300 hour rebuild
interval. They have exotic coatings and metallurgy
to get the reliability that they have. There's no
way you'll even come close to their performance and
reliability in you garage.

Now if you want to build an engine, that's fine. If
you want to talk about building an engine, that's
fine too. I just have to say that you're taking
on a project with very, very small prospects of working
and a real steep downside if it fails in the air.

If you're interested in the design of the Rotax
engines, you can download the manuals he

http://www.rotax-owner.com/index.php...08&I temid=25

The line drawings of the engine, piston and cylinder
might be of interest.


 




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