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DIY Two-Stroke Engine
On Mar 5, 6:56*pm, durabol wrote:
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 There's any amount of engineering info out there on two-strokes, books have been written. They were a staple project in The Model Engineer magazine for years, should you want to look that up. What's UL use? You'd be basically recreating a commodity item. Resurrect one from a defunct snowblower, weed-whacker or Lawnboy and spend more time on figuring out the project you want to drive. The engineering's done, you aren't likely to improve on what's already been built. Want overhead valves? Been done. Rotary valves, ditto. Fuel injection, same. Separate lube system, been done. Opposed twins, flat fours, square fours, Vs, Xs, Ws, all been done. Separate forced air pumping, too. They basically suck thermodynamically except the one feature they've got going is power-to-weight ratio, the small ones pump out a lot of horsepower, usually at high RPM, for their size. For that you can go with an existing engine and spend more time on the rest of the project. Stan |
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DIY Two-Stroke Engine
On Mar 6, 8:45*pm, wrote:
On Mar 5, 6:56*pm, durabol wrote: For the last few years I have toyed with the idea of building a homemade two-stroke engine for UL use. Brock ...What's UL use? Stan I think UL here means UltraLight, a minimally regulated, tiny but MANNED aircraft. http://www.eaa.org/Ultralights/ I looked into it, flew a hang glider a few times, then gave it up for the safer hobby of racing dirt bikes. jsw |
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DIY Two-Stroke Engine
Jim Wilkins schreef:
On Mar 6, 8:45 pm, wrote: ...What's UL use? I think UL here means UltraLight, a minimally regulated, tiny but MANNED aircraft. http://www.eaa.org/Ultralights/ I thought the same, but should like to add that in several countries the "ultralight" definition allows bigger planes, closer to the newer US light sport aircraft definition. |
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DIY Two-Stroke Engine
jan olieslagers schreef:
Jim Wilkins schreef: On Mar 6, 8:45 pm, wrote: ...What's UL use? I think UL here means UltraLight, a minimally regulated, tiny but MANNED aircraft. http://www.eaa.org/Ultralights/ I thought the same, but should like to add that in several countries the "ultralight" definition allows bigger planes, closer to the newer US light sport aircraft definition. Come to think of it, several countries even allow them to FEMALES ! |
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DIY Two-Stroke Engine
On Sun, 07 Mar 2010 13:51:46 +0000, jan olieslagers
wrote: Jim Wilkins schreef: On Mar 6, 8:45 pm, wrote: ...What's UL use? I think UL here means UltraLight, a minimally regulated, tiny but MANNED aircraft. http://www.eaa.org/Ultralights/ I thought the same, but should like to add that in several countries the "ultralight" definition allows bigger planes, closer to the newer US light sport aircraft definition. Like up here in Canada - 1238 lbs? as long as it stalls under 45 MPH. It can have a Lycoming IO-235 in it if you want. |
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DIY Two-Stroke Engine
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DIY Two-Stroke Engine
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 |
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DIY Two-Stroke Engine
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. -- Nigel When the only tools you have are an X3 mill, a Colchester and assorted other stuff, every problem looks like a steam engine. |
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DIY Two-Stroke Engine
"Nigel Eaton" wrote in message ... 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. -- Nigel There have been other uses of outboards that involved using a car-type cooling system, with a radiator. A Bobsy SR2 sports-racing car of the 1960s was very successful in the H-modified class using a Mercury outboard. I think that was a 750 cc class. -- Ed Huntress |
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DIY Two-Stroke Engine
On Sun, 7 Mar 2010 23:04:37 +0000, 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. Can be cooled very well with a radiator - the interface to connect a rad instead of the raw water cooling was possible, but not simple. There were "saltie" conversions that used a sealed cooling system and a heat exhanger availble for some of the outboards of the period, but they were not common. Very common with stern-drives (4 stroke) Actually, there WAS a commercially available helicopter kit that DID use the V4 Evinrude power head - and I believe I've seen refference to the 6 cyl Merc "black max" in experimental aircraft use too. |
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