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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
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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
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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
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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
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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
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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
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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
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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
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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
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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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