# Simple mechanism to convert linear motion into 180 degrees rotation

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?

• Rack and pinion - easily controllable but you don’t want a gear… Jan 3 at 15:38

Without any furter information, the Scotch Yoke is probably what you are after

• 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. Jan 3 at 23:36
• @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.
– NMech
Jan 4 at 13:49
• 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...) Jan 4 at 16:32
• The other option is the slider crank linkage mechanism ( it still suffers from the same problem and its got more moving components).
– NMech
Jan 4 at 18:11
• @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.
– NMech
Jan 4 at 18:14

You need two slots in 90 degrees angle on each other for the wheel