Raising lift with pistons

We are using pistons to raise our lift, however, I do not know how to mount the pneumatics to it properly. The piston does not stay in a lock collar if I try to use them, however, I have seen other teams use them. Any advice is appreciated.

Many of the new pistons come with threads installed that fit with current vex lock collars. Many of the old pistons do not have the threads drilled of the right size, and each of them comes with two small nuts of the right size to be compatible. So, you would need to track down where those went in order to attach stuff to them. There are two other options that I would use in your position:

Option 1

These are called star drive clamping shaft collars, found under shaft collars on the official vex website. These can be used to clamp onto the piston, and you can put a beam behind it or in between two to attach it to the piston.

Another way is to clamp one side to the piston and the other half to a coupler, or a screw with an empty normal bearing flat for mounting.

Pros:

  • Better for the piston and less damaging than option 2
  • Screws in the clamping collar can also be used to fix it to other parts

Cons

  • Very bulky
  • Not as strong as option 2
Option 2 (use at your own risk)

This option is fairly straightforward. By using a standard shaft collar, you can attach a beem between two of them and then tighten them, which provides a very strong clamping and holding effect on the piston. I personally use this on our hang because it has to manipulate huge amounts of force, and thus needs more clamping power to maintain its hold. However, that is a side effect of my robot being very heavy.
Another integration method is to sandwich a screwless shaft collar between two screwed in shaft collars, and then screw whatever you want to attach your piston to into the screwless collar.

Pros:

  • Very Strong
  • Much smaller than option 1

CONS:

  • RISKS DAMAGING PISTON. If you screw on the shaft collars you could permanently flatten the threads on the piston, forcing you to only use shaft collars on it rather than the nuts if you find them.
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Like Entropy said the lock collars don’t fit because you have the old pneumatics which have slightly smaller ends then normal screws. However, the pneumatics should have came with special nuts which do screw onto them and this piece, which can be used in place of a lock collar:
The piece described above

They can be used in combination like this to do what you want:
The piece on a pneumatic cylinder

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The old air cylinders have #6-40 threads on the piston rods (not “special” per se, but still a “normal” size that can be purchased from industrial suppliers), here is one option: https://www.amazon.com/Hex-Machine-Screw-Quantity-Fastenere/dp/B07PVL1MFY/

The new air cylinders have piston rods that are threaded 8-32, the same as the typical VEX size.

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