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My apologies if this design has been posted many times, I sure someone else has thought of it before. And I agree with the experts here, use a real cylinder if building an elaborate and expensive prop. My props are for a hayride, I can manually operate and reset the props.
This is a single action cylinder ie: you have to push it back down. It is made with 1/2" PVC pipe and 3/8" threaded rod.
For the piston, I use 3/8" threaded rod with a 3/8" ID 5/8" OD grommet (Hillman, purchased at Lowes). The nuts had to be rounded down on a grinder to fit inside the pipe. I used a lock nut on one end, the other nut will need threadlock or hot glue to hold in place. You can squeeze the grommet by tightening the nuts, this will make a tighter seal.
Note: since the grommet has a 1/16" groove, I also added a 014 Buna-N O-Ring inside the groove.
I beveled the inside of the pipe using a router bit attached to my drill.
For my next prototype, I want to make a dual action cylinder which will require that I seal the top using a 3/8" ID ~3/4" OD grommet. I will use a PVC slip joint instead of a cap.
This get more complicated as I cannot use thread rod. This will require a rod with threaded ends. I may just buy a die and thread regular rod myself.
For next year's hay ride, I want 8 hands rise out of the ground one by one. Below is a mock-up on how I plan to do this, the second cylinder is connected to the top of the first cylinder. I hope you get the idea here... The cylinder on the right ws my first attempt, it has way too many parts.
This is a single action cylinder ie: you have to push it back down. It is made with 1/2" PVC pipe and 3/8" threaded rod.

For the piston, I use 3/8" threaded rod with a 3/8" ID 5/8" OD grommet (Hillman, purchased at Lowes). The nuts had to be rounded down on a grinder to fit inside the pipe. I used a lock nut on one end, the other nut will need threadlock or hot glue to hold in place. You can squeeze the grommet by tightening the nuts, this will make a tighter seal.
Note: since the grommet has a 1/16" groove, I also added a 014 Buna-N O-Ring inside the groove.

I beveled the inside of the pipe using a router bit attached to my drill.

For my next prototype, I want to make a dual action cylinder which will require that I seal the top using a 3/8" ID ~3/4" OD grommet. I will use a PVC slip joint instead of a cap.
This get more complicated as I cannot use thread rod. This will require a rod with threaded ends. I may just buy a die and thread regular rod myself.

For next year's hay ride, I want 8 hands rise out of the ground one by one. Below is a mock-up on how I plan to do this, the second cylinder is connected to the top of the first cylinder. I hope you get the idea here... The cylinder on the right ws my first attempt, it has way too many parts.

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