How do I slow down the extension of a piston?

VEX V5 General Discussion Technical Discussion
#1

Hi, so I have two double acting pistons that I’m using for tilting up a goal post. I want them to retract at full force and speed but extend slowly.

I don’t have flow control valve so wanted to ask how I can do this without entirely losing my ability to extend or sacrificing any retraction force.

Some ideas I had were to:

  • slightly block off the exhaust valve on the solenoid
  • putting a pressure regulator on the ports on the back side of the piston
  • putting rubber bands on the piston to resist extension

I would really appreciate some help on what I should do as I haven’t used pneumatics before and don’t want to break anything by experimenting. Thank you.

#2

I just put a cut piece of rubber band over the exhaust valve and ziptied it down super tight for my tilter.

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#3

Which exhaust valve is it over? The solenoid exhaust valve, the rod side air port on the piston, or the back side air port?

#4

use this part called a flow meter

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you can adjust how fast a piston moves by tuning the position of the nut

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#5

but wouldn’t that slow my retraction as well since the air going into the piston is slowed down just as much as the exhaust

#6

No, you can plug it into only one port. The other port will function as normal.

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#7

so if I plug in a flow meter into the extension port on a piston (the back side one), then that slows the extension by slowing the air going into the piston, but it doesn’t slow the retraction by slowing the air coming out of the piston from that port right

#8

no.

source: me, i use it on my tilter. It works just as a I described

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#9

ok got it i’ll try to find one of those and attach them to the back side of the piston. Also, if I can’t find one, do you have any ideas for a DIY one?

#10

The easiest way is probably to do passive actuation / retraction so that one side is not powered by air, then simply use rubber band to adjust how strong you want the mechanism to be pulled back. Passive retraction can be done by using a single acting solenoid, and only connecting it to one of the double acting ports.

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#11

in my case I need to do passive extension so can I use a pressure reg to just supply very little pressure to the extension ports

#12

I use single acting pneumatics so Its just on the one exhaust valve of the solenoid.