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  • Auto reverse mechanism

    I am getting a yen to machine something, but not an engine. I am somewhat intrigued by mechanisms that have an "automatic reverse" function to them. Not just a simple function like reversing gears, but more like something that moves along a short track, stops at the end of travel, then reverses movement and moves back to the original starting point and then repeats. The power source for this would be one of my many small engines. I have googled "reversing mechanisms" and there is a great array of articles posted about this. Of course, I want it to be something with a considerable "WOW" factor to it. I have the capacity to make spur gears here, but not internal gears nor funky gears like you see on a mangle.(Which is super neat.) The biggest problem I see to a mechanism like this is that when it gets to the "turnover" point, if it has to shift a lever to go into reverse it will probably just "hang up". The actual mechanism which moves something along can be a threaded rod with a threaded follower that reverses rotation, or a rack/pinion drive, even possibly a flat belt drive that shifts from a clockwise rotating pulley to a counter-clockwise rotating pulley. The big deal is that it has to do this without human intervention. I don't have the capacity to make a double reverse thread like you see on "level-wind" fishing reels. My tools are strictly limited to a manual lathe and a manual mill and a full set of 24 pitch gear cutters. I will have no problem designing whatever it is that I do, it's more the fact that I have to figure out exactly what I want to do. This is a wide open game, so if you have a good suggestion or a link to this type of mechanism working, by all means go ahead and tell me about it.---Brian
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

  • #2
    Well, this jumped out at me when I image googled "mangle gears" to see what you meant by the use of the term "mangle" and while it does not use exactly standard gears for the elongated rack I could see that being built up of two rack sections and two half gear segments perhaps:

    http://kmoddl.library.cornell.edu/model.php?m=379

    Just a thought. Be an interesting motion visually I think.

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    • #3
      May find something suitable here: http://kmoddl.library.cornell.edu/model.php?m=68

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      • #4
        The simplest mechanism I can think of is a gear mounted on a yoke such that it toggles back and forth between two driven gears when a protruding rod hits a stop at the end of the track. It can be arranged so that one rod goes the full length of the "car" so that the movement of the yoke is positive.

        A nice "wow" would be to use a mechanism that would tumble when the car hits an object, thus using the thrust of the driving mechanism to determine which gears are in mesh. Of course, you can also engage the idlers to engage different flat belts instead of gears.

        Dan
        At the end of the project, there is a profound difference between spare parts and left over parts.

        Location: SF East Bay.

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        • #5
          danlb--I have thought about that one. The problem as I see it, is that right at the moment of "crossover", the forward motion has to stop momentarily, then pick up again in the opposite direction. Without a flywheel in there somewhere, it would kick halfway and then hang up. I do have a design for a spring loaded toggle in my head, that kicks from one position to the other with help of a tension spring. I just haven't sorted through the idea totally.---Brian
          Brian Rupnow
          Design engineer
          Barrie, Ontario, Canada

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          • #6
            Alanganes--I hadn't thought of using two sections of rack and two half gears to make up a mangle. It might require some pretty fussy "fettling" to get the pitches aligned properly, but it is definitely a possibility.
            Brian Rupnow
            Design engineer
            Barrie, Ontario, Canada

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            • #7
              Do a search on YouTube for mechanisms, and you will find many animated videos showing reversing mechanisms..

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              • #8
                Take a look at the mechanical principles video. There is one in that, with a partial gear, as I recall.

                There are also "run around gears" used in wind powered well pumps, so you might look them up.
                2730

                Keep eye on ball.
                Hashim Khan

                Everything not impossible is compulsory

                Birds are NOT real, they are spying on you

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                • #9
                  I did a quick google search for "run around gears-windmill" and didn't find anything.
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

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                  • #10
                    Originally posted by brian Rupnow View Post
                    I did a quick google search for "run around gears-windmill" and didn't find anything.
                    That's really my own description of it, I don;t know if it is used by anyone else......

                    I went looking and can't find anything on line. It's in the old "Ingenious mechanisms" book, for sure.

                    Anyhow, there is a "racetrack shaped" (obround) gear, with teeth on the inside of the obround. The pinion runs up one side, around, and down the other, around, and up again. That makes the linear motion from the rotary motion of the pinion, back and forth, with the size of the obround internal gear setting the stroke. It can give a pretty long stroke.

                    Actually, the pinion rotates on a fixed axis, and the racetrack gear usually moves, with the gear guided by a groove in it. so that it has to follow the path.

                    I have seen this on old wind pumps.
                    2730

                    Keep eye on ball.
                    Hashim Khan

                    Everything not impossible is compulsory

                    Birds are NOT real, they are spying on you

                    Comment


                    • #11
                      Why not take a look at some planers? They have a drive mechanism that does exactly what you describe: they go in one direction at a constant speed until the table hits a stop, then take off in the reverse direction, hit a stop, reverse, rinse, repeat.

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                      • #12
                        What will the stroke length be on this, and is the primary attraction here to reverse linear motion, or rotary motion too?

                        You might find something to spark the creativity here: http://507movements.com/

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                        • #13
                          How about a level wind set up like for a bait casting reel or a hose reel . That is simple and reverses. It does the same thing over and over. Just my two cents.

                          Dave

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                          • #14
                            The metal planer, not shaper, the old moving table planet has a very elegant forward reverse toggle set up, there are some vidios on tube, I won't link as if I do I'll have to watch them all, again, there's only one thing I like more than shapers, you guessed it, planers not the wood kind either (though anything will do machine wise, the wife reckons I'd watch a vidio of a coffee machine)
                            Mark

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                            • #15
                              Look at the geared table traverse transmission on the B&S #13 tool and cutter grinder. It has a center hold toggling table reverse lever, an engagement clutch etc and is intended to work with reversing stops on the table.

                              I have one for some reasonn and it's beautifully designed. Maybe you can find an illustration with enough detail to put you on the track you seek. Like here:

                              http://vintagemachinery.org/pubs/detail.aspx?id=6011

                              If you download anything from VintageMachinery.org, send them a few bucks Worthy outfit

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