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I want a simple mechanism to rotate something 180 degrees when another thing moves linearly past/through it. The below is what I have, but it can only work with an offset, so the movement is never fully 180 degrees. No gears/belts etc., it must be a simple mechanism. Any ideas? enter image description here

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  • $\begingroup$ Rack and pinion - easily controllable but you don’t want a gear… $\endgroup$
    – Solar Mike
    Jan 3, 2023 at 15:38

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You need two slots in 90 degrees angle on each other for the wheelenter image description here

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  • $\begingroup$ Actually this does give 180 deg motion by doubling the idea i put above - suppose its basically a v simple rack and pinion like @solar Mike said. Bit more detailed diagram would help this be more useful i think. $\endgroup$ Jan 7 at 11:21
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Without any furter information, the Scotch Yoke is probably what you are after

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  • $\begingroup$ That conversts rotary into linear - the opposite of what the OP requires. As show in your image a push from the right will be stuck on top-dead-centre. $\endgroup$
    – Transistor
    Jan 3, 2023 at 23:36
  • $\begingroup$ @Transistor It can be used for both cases. Given the constraints that the OP provided I think it a simple and adequate solution. And although you are right there is a dead point, its and unstable equilibrium so even a small force it will move either way. $\endgroup$
    – NMech
    Jan 4, 2023 at 13:49
  • $\begingroup$ Its definitely an improvement on what I put - but yea it still suffers the same issue of there being a dead point, so one can't reliably get the full 180 degrees (though maybe 179.999...) $\endgroup$ Jan 4, 2023 at 16:32
  • $\begingroup$ The other option is the slider crank linkage mechanism ( it still suffers from the same problem and its got more moving components). $\endgroup$
    – NMech
    Jan 4, 2023 at 18:11
  • $\begingroup$ @OliverWalters If you are worried about the dead point, you can use a slight offset between the rotation axis and the sliding axis. You will be sacrificing some degrees (but if radius is adequately large that can easily be under 1 deg. $\endgroup$
    – NMech
    Jan 4, 2023 at 18:14

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