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Searching for model 2 stroke plan recomendation

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  • Searching for model 2 stroke plan recomendation

    After building 10 four stroke i.c. engines, I would kind of like to try my hand at a two stroke. I have seen the Jan Ridder plans, and I know that people have problems getting these engines to run. In fact, the people who did get them to run had to modify them to do so. I have also seen the Rudy Kahoupt "Pioneer" two stroke with valves. The tiny engines similar to the Val are not what I want either. I have not been successful in my search for a conventional two stroke that can be built from bar stock with no castings. something with a 7/8" or 1" bore, preferably. Does anyone have a recommendation for a two stroke that can be built with conventional mill and lathe?----Brian [email protected]
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

  • #2
    Anything of interest here?:
    http://www.john-tom.com/html/ICEngines.html
    Location: Long Island, N.Y.

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    • #3
      Remember this (Popular Science 1946)? - I think it's two-stroke:



      Part 1, June 1946 (scroll down 2 pages):
      https://books.google.com/books?id=7S...page&q&f=false

      Part 2, July 1946:
      https://books.google.com/books?id=TC...page&q&f=false

      Part 3:, Aug 1946:
      https://books.google.com/books?id=Li...page&q&f=false
      Last edited by tlfamm; 02-05-2016, 12:18 PM. Reason: Fix links

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      • #4
        Originally posted by tlfamm View Post
        Remember this (Popular Science 1946)? - I think it's two-stroke:



        Part 1, June 1946 (scroll down 2 pages):
        https://books.google.com/books?id=7S...page&q&f=false

        Part 2, July 1946:
        https://books.google.com/books?id=TC...page&q&f=false

        Part 3:, Aug 1946:
        https://books.google.com/books?id=Li...page&q&f=false
        Tifamm--Your links don't work.---Brian
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

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        • #5
          Sorry, I foolishly saw no need to check the links in the text I pasted - duh. Guaranteed to work now ...

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          • #6
            You might copy a Ohlsson & Rice 1HP with a bore & stroke 1.250" x 1.096" = 1.34CID 1hp @ 6300rpm. I have one on a Tiny Tiger genset like this
            http://www.gasenginemagazine.com/gas...px?SlideShow=4

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            • #7
              This one is nice. Hemingway sells the rough castings individually. You can get by with the crankcase only and make the rest from barstock. However, the front end would be a real PIA to duplicate. http://www.hemingwaykits.com/acatalo...lin_Jones.html

              RWO

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              • #8
                My working knowledge of two strokes?--Well, they have piston, rings, connecting rod and crankshaft similar to 4 cycle engines. They do not have a camshaft nor valves. The crankcase is closed and will hold pressure. They combine the strokes--When the piston is moving up on compression, it creates a vacuum in the sealed crankcase. The carburetor feeds into the crankcase thru a one way valve, most commonly a piece of very thin spring steel called a reed valve. The lubricating oil is mixed with the fuel, so as the fuel enters the crankcase it lubricates the crankshaft bearings and both ends of the connecting rod, and the cylinder wall. The engine is fired by a sparkplug at or slightly in advance of top dead center and the piston begins to move down in the cylinder on the power stroke. As the piston moves down in the cylinder, this raises the pressure in the crankcase, and the reed valve under the carburetor snaps shut so the pressure in the crankcase can not escape. At some point in it's downward travel, after most of the burning fuel charge has expended it's energy but the piston is still moving down, the piston uncovers a port in the side of the cylinder which is connected to the pressurized crankcase. The fact that the fuel charge in the crankcase is pressurized makes it flow from the crankcase, thru the port in the side of the cylinder, and into the cylinder itself. At this point, the piston bottoms out and begins it's upward travel on the compression stroke. The side of the piston first closes off the port in the side in the side of the cylinder so that the charge of fuel which is now in the cylinder can not escape back into the crankcase. The piston then continues towards top dead center compressing the fuel charge and once again creating a vacuum in the crankcase to draw in more air/fuel mixture. Then the cycle repeats itself. The two cycle engine fires every time the piston reaches top dead center. From what I remember, the top of the piston is not flat, but has a "shape" to it which has something to do with keeping the burning fuel charge from blowing back thru the port into the crankcase---(I could be wrong on that reason.) ----So much for the theory behind two cycle engines.---Like everything else in life, the devil is in the details. If the piston has rings on it, how does it pass a port in the side of the cylinder without breaking the rings? How far down the stroke of the cylinder is the port so that it optimizes the power from the expanding fuel charge and still allows some time for the pressurized charge to flow upward from the crankcase into the cylinder. Would a model engine require seals on the crankshaft where it exits the crankcase, similar to 2 cycle snowmobile engines. (I once had a Yamaha snowmobile that had bad crankscase seals--it would go like stink at high speed but stall every time you slowed to an idle.) I know that there are many variations to what I have described. I know that the Jan Ridders design pressurizes the fuel charge in a separate compartment. I also know that two cycle chainsaws and weedeaters have flat top pistons, and I'm not sure how they get away with that. So you see, I know a great deal about 2 cycle engines. that is the good news. However, there is a great deal more that I don't know about 2 cycle engines, and that is what keeps me from boldly jumping into the design and fabrication of an engine which is doomed to failure because of the things I don't know. If I do this at all, I would much rather follow in someone else's footsteps.---Brian
                Brian Rupnow
                Design engineer
                Barrie, Ontario, Canada

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                • #9
                  How about a 1:10 scale Lister CS. I often wondered how well real scale diesels operate... The engine might not be too bad but I bet the injectors would be a bugger
                  paul
                  ARS W9PCS

                  Esto Vigilans

                  Remember, just because you can doesn't mean you should...
                  but you may have to

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                  • #10
                    No, I don't want diesel, glow, nor compression ignition engine plans. The old single cylinder Maytag engine would be just about perfect . The right speed and simplicity and a minimum of moving parts.
                    Brian Rupnow
                    Design engineer
                    Barrie, Ontario, Canada

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                    • #11
                      Hi Brian,

                      I know a little about 2-strokes from my model airplane days.

                      Pistons have a vertical dam machined in to direct the intake charge upward and not directly into the exhaust port. Some engines are flat top and they have Schnuerle porting which are typically higher performance engines.

                      https://en.wikipedia.org/wiki/Schnuerle_porting

                      I'd go with a machined damn in the piston because our engines are fairly low performance and I think it would be easier to get right.

                      2-strokes do have valves, in r/c airplane motors they usually use a ported hollow crankcase that communicates to the carb at the right time. Some use a rear crankcase rotary valve driven with the crank pin. Some use a reed valve which is a simple 1-way valve (like a cox .049 engine) These run backwards almost as well as forward.

                      Lot's of r/c engines have rings, they slide right past the ports. Usually a ringed engine will have the port divided into smaller segments to help the ring.

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                      • #12
                        Brian, you seem to have missed the exhaust in your description, on the power stroke as the piston decends the exhaust port is uncovered and allows the highpressure burnt mixture to leave the cylinder before the transfer ports are uncovered, the period between the exhaust opening and the transfers opening is called the blowdown period if it is too short the ezhaust will travel down the transfer ports contaminating the mixture.
                        The timing of the ports is critical to the operation of the engine. If you want maximum power from the engine you will need to design an expansion chamber, which if operatig correctly will destroy your understanding of 2 strokes as you knew them. What you described was a pre ww2 twostroke similar to a villiers lawnmower engine. Which would be an excelent engine to copy and scale as a model.

                        Pistin rings are held in position with a peg in the ring groove to stop them snagging an end in a large port like the exhaust. they can be pinned so the ring gap is constantly in contact with the cylinder wall , but if pinned over a small port they work fine.

                        The best ever 2 stroke engine is the Aprilia RSA125 making around 53 hp from 125cc, this technical marvel was created by Mr Jan Thiel , widley recognised as the worlds greatest 2 stroke tuner, worth looking up

                        Here is a 98cc villiers with an overhung crank (easy to align) http://www.tanygraig.force9.co.uk/John/villjdl.htm
                        Last edited by Yow Ling; 02-05-2016, 04:04 PM.
                        My neighbours diary says I have boundary issues

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                        • #13
                          Originally posted by brian Rupnow View Post
                          ... If the piston has rings on it, how does it pass a port in the side of the cylinder without breaking the rings? How far down the stroke of the cylinder is the port so that it optimizes the power from the expanding fuel charge and still allows some time for the pressurized charge to flow upward from the crankcase into the cylinder.---Brian
                          The rings do expand into the port space when the rings pass over the port. The port top, side and bottom edges are given a slight chamfer on the bore side to allow the ring to survive the experience.

                          The lower edge of the port is exactly at the top of piston at BDC. The top edge of the port is as high as you want to make it; the general theory is the higher the top of the port is (and the motor still runs) the more power produced ... s**t I am going to get fried for saying that. That said, I doubt you are targeting racing outputs per cube so make top edge of port low ... it is easier to raise it than lower it.

                          Cheers,
                          Norman

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                          • #14
                            Another great engine to copy/scale would be the Trojan Mini Motor , which is designed as a clip on bicycle assist motor, I have one on a bike

                            https://cyclemaster.wordpress.com/pa...the-minimotor/

                            The crank case is 2 simple castings, easy to make on a mill, no reed valve as it is a piston ported engine , and with the factory exhaust , oozes with character
                            My neighbours diary says I have boundary issues

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                            • #15
                              Yow Ling--You are right. In my burst of enthusiastic writing, I just plain forgot the exhaust stroke, which coincides with the compression stroke. I like to run Viton rings, and since they are a type of heat resistant rubber o-ring, I don't think they would survive sliding past intake or exhaust ports.
                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

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