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Alternate exhaust valve lifting mechanisms

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  • #31
    The possibilities are endless, unfortunately so is the "funk factor"

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    • #32
      To be truthful, I am somewhat intrigued by the ball point pen retraction mechanism. I will give it more thought.--Brian
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

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      • #33
        The c.1885 Daimler four stroke is an interesting design - no cam shaft, exhaust valve is worked by a face cam, i.e. a groove in the face of the flywheel. It takes two revolutions to complete the track i.e. the cam follower has to change tracks after one revolution!


        Nb. this engine had an atmospheric inlet valve and another valve in the piston. The valve in the piston helped to scavenge the cylinder of burnt gases. As the piston went down the cylinder, crankcase pressure increased, at BDC the valve in the piston hit a stop which caused it to open, thus pressured scavenge air entered the cylinder and helped expel the burnt gases through the exhaust valve.

        Yeah, it sounds unnecessary to me too, but apparently it allowed Daimler to avoid infringing the Otto patents.

        These images are from Internal Fire by Lyle Cummins.







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        • #34
          PeterS--That is very interesting, and I haven't seen that before. Unfortunately, I only have a manual lathe and mill, so have no way of putting in a cam track like that.--Brian
          Brian Rupnow
          Design engineer
          Barrie, Ontario, Canada

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          • #35
            Originally posted by brian Rupnow View Post
            PeterS--That is very interesting, and I haven't seen that before. Unfortunately, I only have a manual lathe and mill, so have no way of putting in a cam track like that.--Brian
            You could do it in "reverse" instead of a groove use a thin brass plate, mould it to the correct configuration and solder it to the flywheel. At the "X" crossing just leave it open like the railway crossing.
            Helder Ferreira
            Setubal, Portugal

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            • #36
              Electronic valve openers. Uses a coil & return spring to open/close valve.
              Krutch


              Mentally confused and prone to wandering!

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              • #37
                Krutch--Please---go back and read the last line of the very first post in this thread.---Brian
                Brian Rupnow
                Design engineer
                Barrie, Ontario, Canada

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                • #38
                  Originally posted by brian Rupnow View Post
                  PeterS--That is very interesting, and I haven't seen that before. Unfortunately, I only have a manual lathe and mill, so have no way of putting in a cam track like that.--Brian
                  I wonder how it was done back in 1885, no CNC back then and probably the same machine tools you have access to. It would be interesting to know.

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                  • #39
                    Originally posted by Peter S View Post
                    The c.1885 Daimler four stroke is an interesting design - no cam shaft, exhaust valve is worked by a face cam, i.e. a groove in the face of the flywheel. It takes two revolutions to complete the track i.e. the cam follower has to change tracks after one revolution!


                    Nb. this engine had an atmospheric inlet valve and another valve in the piston. The valve in the piston helped to scavenge the cylinder of burnt gases. As the piston went down the cylinder, crankcase pressure increased, at BDC the valve in the piston hit a stop which caused it to open, thus pressured scavenge air entered the cylinder and helped expel the burnt gases through the exhaust valve.

                    Yeah, it sounds unnecessary to me too, but apparently it allowed Daimler to avoid infringing the Otto patents.

                    These images are from Internal Fire by Lyle Cummins.









                    Yesterday while I was driving I designed a system for Brian while thinking about this, it kinda resembles a little of what you just showed in this post --- but I think it's allot simpler actually,,,

                    hear's how it goes, there are no ramps on the crank like in the above pic - there are only "spirals" if you will, you know the kind you used to use to pump up that toy top deal when you were a kid? anyways - even though the groves intercross you can make them go fore or aft in whatever way you want,,, just takes a drive piece about double the length of the slot themselves - now you have full control of the exhaust valve - either do the same with the intake or make the intake poppet...


                    what's not to luv? oh right the machining I guess...
                    Last edited by A.K. Boomer; 07-21-2014, 03:53 PM.

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                    • #40
                      It requires a couple of gears (one internal) but no cams, pushrods or valves - Wankel rotary engine? It's technically a four-stroke, but sounds like a 2-stroke! It would be an interesting project, needing a pair of trochoid curves machined, the hard part will be the rotor tip seals... Ask NSU!
                      Rules are for the obedience of fools, and the guidance of wise men.

                      Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

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                      • #41
                        There sure are some clever ideas coming up. Getting them to the function stage might be a challenge. The 2:1 ratio is so every bit a part of a 4 stroke engine that not using gears to achieve it is going to be interesting. A certain level of friction is inherent in some the actions that will have to be overcome but tiny ball bearings are so cheap these days that what might have been self defeating maybe not so?
                        Last edited by topct; 07-21-2014, 04:35 PM.
                        Gene

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                        • #42
                          Anyone REALLY interested in this subject, check out these websites. Geneva mechanisms seem to rule the day, but there are hundreds of variants.
                          https://www.google.ca/search?q=inter...=1920&bih=1099
                          https://www.google.ca/search?q=index...ml%3B150%3B100
                          Last edited by brian Rupnow; 07-21-2014, 07:27 PM.
                          Brian Rupnow
                          Design engineer
                          Barrie, Ontario, Canada

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                          • #43
                            Years ago, at a very small engine show in Northern DE I saw a McVicker horizontal engine running. From what I remember of its size it was probably about 5HP, and was operating at about 500 RPM. It was atmospheric intake, and thinking about it now I would guess that it was governed by holding the intake open. The exhaust valve was in a pocket aside the cylinder (like any side valve). There was a small diameter rod, run by a simple eccentric on the crank and oscillating uselessly at about a 10% downward angle, enough to miss the exhaust valve stem. The end of this rod sat on top of a vertical peg, sliding back and forth across the peg. The engine would overspeed enough for the governor to hold the intake open and the engine would make a number of revolutions, like any hit or miss engine, but when the speed dropped enough the intake was allowed to seat, a charge was inhaled, and the engine fired. Then, and only then would the vertical peg rise up enough to lift the oscillating rod to a parallel to the base attitude, it would take a stab at the exhaust valve stem, the valve would open and the and the exhaust would blow out. But how did that peg know when to lift the rod? I was there for a long time hunched down watching the thing, and the smile on the fellow attending it's face got larger and larger. Finally, I gave up, and had to ask. There was a passageway connecting a hole in the cylinder wall about three quarters of the way down the stroke to the bottom of the peg, and the residual combustion pressure pushed the peg up. The attendant said that when he went to restore the engine, it was practically unworn, but he could not figure how the horizontal rod was supposed to lift to work the valve. He thought at the time, quite naturally, that the peg was just some thing to support the forward end of the rod, and there must be some pieces missing. Finally, he remembered that there was a round black mark at the bottom side of the cylinder when he lightly honed it- which he though was just a casting flaw-- and started digging carbon out of it. Finally, the penny dropped and the truth was evident. Probably the hole was prone to clogging, and required periodic cleaning, which was less than easy. so the engine was out of service early in it's life.

                            At the time, I thought about making a smaller version, but realized that the much smaller hole would probably carbon up in a matter of minutes. so shelved the idea. Now, however, with the modern non burning synthetic two stroke oils-------

                            Artful Bodgers idea in post 23, in real life!

                            Gronk
                            Last edited by gronk; 08-26-2014, 11:59 AM. Reason: Called the Artful Bodger the Artful Dodger----SORRY!

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                            • #44
                              Brian, if I am reading your posts correctly, you are mainly trying to avoid the extra camshafts, not gears. If that is incorrect, please disregard this.

                              How about turning the good old sun and planet gear system around. One gear is on the crankshaft and a second one, with the same number of teeth, on a push rod would revolve around it once every two rotations of the crankshaft. This will probably only work with one cylinder and one valve, intake or exhaust. Some kind of linkage would be needed for the second valve.

                              Not really ideal, but the crankshaft is better than the sun and planet and, likewise, the camshaft is probably a better option too.


                              Or you could grab one of those little refrigerator elves who turns the light on when you open the door and off when you close it and retrain him to lift the valves instead. He will probably be happy to get out of that cold refrigerator.
                              Paul A.
                              SE Texas

                              And if you look REAL close at an analog signal,
                              You will find that it has discrete steps.

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                              • #45
                                Thank you gentlemen. I have abandoned this concept for the time being, and have decided to build a bar-stock side valve engine instead. It may be seen on my post "A new engine for Fall"-----Brian
                                Brian Rupnow
                                Design engineer
                                Barrie, Ontario, Canada

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