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Gearless Mechanism--4 stroke i.c. engine

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  • Gearless Mechanism--4 stroke i.c. engine

    I have long been fascinated with the old hit and miss engines that were 4 cycle engines, but used no gear to drive the cam shaft at half the speed of the crankshaft. I have studied on this, and they break down into two main types. The kind I can not reproduce on a manual mill is the type which had cam tracks cut into the face or periphery of a disc. Chuck Fellows did a really nice job of reproducing one of those last year. The other type, which I can reproduce on my manual machinery, is the "star wheel" type. I don't want to start another engine build right now. However, I will attempt to create one of the mechanisms, post drawings of how I made it, and build the mechanism and make a video of it operating. I might fall on my face here, but follow along if you are interested. The one I make will be sized to work on a model engine.
    Brian Rupnow

  • #2
    Got to have something to mount the star wheel in----
    Brian Rupnow

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    • #3
      Brian,

      I'm not sure I follow exactly where this is going but I am pretty sure I will before long. As usual, thanks for sharing.

      Brian
      OPEN EYES, OPEN EARS, OPEN MIND

      THINK HARDER

      BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

      MY NAME IS BRIAN AND I AM A TOOLOHOLIC

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      • #4
        Originally posted by brian Rupnow View Post
        I have long been fascinated with the old hit and miss engines that were 4 cycle engines, but used no gear to drive the cam shaft at half the speed of the crankshaft. I have studied on this, and they break down into two main types. The kind I can not reproduce on a manual mill is the type which had cam tracks cut into the face or periphery of a disc. Chuck Fellows did a really nice job of reproducing one of those last year. The other type, which I can reproduce on my manual machinery, is the "star wheel" type.
        Don't want to derail your thread Brian but surely this type with star wheel could be classes as a 'gear' ? Still interested in seeing how you go on with it though.
        .

        Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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        • #5
          John--Perhaps it could be classed as a gear, but it's not. It is part of a ratchet and pawl set-up.
          Brian Rupnow

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          • #6
            Brian

            A bit OT, but have you thought about building a sleeve valve engin,as per what Sir Harry Ricardo was working on back in the late 1940s?

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            • #7
              I am aware of such a thing, but I have no intention of building one.---Brian
              Brian Rupnow

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              • #8
                I will be following your star wheel valve timing mechanism with interest Brian. You always turn out those amazing engines in such short time that I cannot imagine that you could possibly be retired!

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                • #9
                  I want to see just a couple of more pieces. I think I see................
                  Gene

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                  • #10
                    These mechanisms seem to do a lot better with a roller on the end which rides on the cam. I am assuming that this is because #1--it will be moving twice as many times in a complete cycle as a lifter which runs off a camshaft---and #2---it will be moving twice as fast, and #3--it has more mass than a standard "valve pushrod".
                    Brian Rupnow

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                    • #11
                      Here's a concept I came up with several years ago that uses two standard box-end ratchets and a yoke. I'd suggested a playground teeter totter as a drive mechanism. It turns a shaft one direction regardless of the direction of motion of the yoke.

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                      • #12
                        At this point, I have to decide whether the engine cylinder will be horizontal or vertical. The gearless mechanism will work on either, but for illustration purpose, I will use vertical. I also needed to show the exhaust valve that will be acted on (the intake valve is atmospheric)----and what better to use than the valve body/carburetor that I so recently designed for the oscillating i.c. engine.
                        ----Now, to get into the science of how this thing works. Immediately below the stem of the exhaust valve, you will see the 4 lobed brown "star wheel". This star wheel has 4 "lobes" that will contact the bottom of the exhaust valve and lift it, if the entire gearless mechanism is lifted on a cam. It also has 4 "relieved areas" between the "lobes" (as shown) which will NOT contact the valve stem if the star wheel gets rotated 1/8 (22.5 degrees) before it gets lifted again!! So--Stay with me--the cam is attached to the crankshaft. That means that with every single revolution of the crankshaft, that gearless mechanism will lift up on the cam lobe and then return to the "down" position--(There will be a tension spring attached to the gearless mechanism to ensure that it does return to the "down" position and stay in contact with the cam. So---as long as we are able to rotate that star wheel 1/8 of a turn every time the mechanism goes up and down then the valve will only get lifted EVERY OTHER time the gearless mechanism is lifted.--That nifty looking green ratchet wheel with 8 notches on the same shaft as the star wheel is the component which ensures this will happen.
                        Brian Rupnow

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                        • #13
                          What keeps the star and ratchet wheels from turning too far on any given bump from the cam?

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                          • #14
                            Originally posted by Toolguy View Post
                            What keeps the star and ratchet wheels from turning too far on any given bump from the cam?
                            Patience!!---all will be revealed---
                            Brian Rupnow

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                            • #15
                              Toolguy raises a very good point.--What keeps the star wheel and ratchet wheel from drifting out of the proper rotational relationship to the valve stem. I have seen it done two ways, and know of a third. The third way which I know of, is a spring loaded detent ball and eight detents in either the star wheel or the ratchet wheel. This might work fine for something that only sees occasional use and slow moving components, but it wouldn't live with something like this application. I have seen the following method used on a model---A piece of rubber or vinyl tubing is slipped over the axle between the ratchet wheel and the blue "fork" supporting it, and is a bit longer than the actual space provided there. This acts as a friction brake to keep the star wheel from rotational drifting out of alignment. The third way, which is used by Philip Duclos on his gearless engine design, it to have a piece of spring wire laying tight against the flat face pf an 8 sided octagonal wheel which rotates with the star and ratchet wheel. When the star wheel and ratchet wheel and octagonal wheel rotate, the spring wire is bent away from the flat it lays against and after the 22.5 degrees of rotation another flat face is presented and the spring wire snaps into place against the flat to keep it from drifting rotationally until the next cam action turns it again. I like the Philip Duclos method best, and will investigate it farther---The only thing I don't like about it is that it begins to get very "busy" around the star wheel. If anyone out there knows of a better/different way, please step forward and tell me about it.---Brian
                              Brian Rupnow

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