LP pneumatics - ram exhaust hole size

I'm working through the thought process of how a LP pneumatic flipper could work if the return was based upon a bungee cord (i.e. like a FP system). The bit im stuck on is the position and size of the hole that would need to be drilled into the bottom of the ram. As its low pressure, I'm thinking 0.5mm on the opposite side to the port so the gas has further to travel before exiting the ram. Obviously, I only have one shot at drilling this hole so any advice would be great. FYI, the ram is 50mm stroke and 80mm bore.

Cheers

Dan

If you want pure speed, the exhaust hole should as big as possible.

If you want adjustable speed, the exhaust hole should be adjustable in surface/diameter.

Maybe start at 0.5mm on opposite side to the port then enlarge if required? I need to make sure that get all the power out of the ram due to the short stroke.

I think there is some confusion going on here, I think Mario is talking about the exhaust hole on the non-powered side (ie the side where you don't put in the compressed gas). Dan is talking about a vent hole in the pressurised side.
For an LP system you don't need a vent hole as LP 3/2 valves are so common and cheap that you can just use one of those to vent the gas.

But flow is awful through common 3/2 valves (I'm planning to use a larger 2/2 NC valve) and I'm trying to keep the whole thing as simple/ compact as possible. It would literally be a FP set-up using LP components @ 10 bar.

http://www.teamonslaught.fsnet.co.uk/pneumatics.htm

Assuming your competent with pnuematics then I wouldn't bother with low pressure. Keep it simple and go high.

Do yourself a favour, if Flow is yours, build her a new chassis and bodywork, she's tired :)

This would be my first venture into pneumatics and going FP would require me to outsource manufacture of the system which isn't something I'm keen on as I want to learn more about how to put these things together.

Ermmmm........ I dont own flow lol.

So pop up a list of parts you have, then we can go through them before you drill any holes

And flow isn't awful through 3/2 valves when she works, she works well. Jarvis just needs to learn a bit more about pnematics

In regards to Flow, I wouldn't know enough about it to comment and a little confused as to why it was mentioned in the first place?! lol

Anyway, the only part I have at the moment is a SMC CDQ2B80-40D double acting cylinder (80mm bore, 40mm stoke). Bought it from ebay a couple of years ago for £20. Could have sworn it was 50mm stroke but its nice, compact and should give a decent kick.

The valve would be a simple 12v valve along these lines (http://www.aliexpress.com/item/Free-...986222776.html). Cheap and heavy but should do the job with a decent straight-through flow.

Two 12oz paintball tanks with one as the buffer and a paintball regulator. Assembly would involve attaching the valve directly to the cylinder using a simple "T" shape plumbing arrangement to attach the tanks. Then a small ball valve as a dump and PRV. Return would be via a bungee and the aforementioned drilled hole.

This is purely theoretical at the moment but my aim is a for cheap, simple, compact and reliable flipper that has plenty of shots.

Quote:

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Originally Posted by Danjr1

But flow is awful through common 3/2 valves

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Time to sort out the confusion. Gabe, I believe he was referring to the flowrate of the gas rather than Flow the robot :p

Haha! Now I've got you!

"But flow is awful through common 3/2 valves (I'm planning to use a larger 2/2 NC valve) "

he forgot the word 'the" .....But the flow

Dan, what is the size of the port on your ram?

From awful memory its between 3-4 mm diameter and the thread is a 3/8 variant. That could be enlarged though.

I got these from Chris. I have used this system in Legion, now to be fair when it flips its ok. Legion had senile electronics and i neglected to turn on the gas in one fight other than that you get an explosive kick. Flow also uses a low pressure system on these lines and that gives an almighty kick. the secret is QEV quick exhaust valves. Your design might well work but it is a design that is used for high pressure systems.

and go bigger than 3/8"

http://www.technobotsonline.com/polo...d-version.html

heres a good switch for the system, don't use a battle switch

Cheers for link and images, is defo food for thought. Will have to commit to a new bot first!

I looked the ram up.
http://www.smcpneumatics.com/replace...-CQ2-E.pdf.pdf

I know those from work.
Those ain't easy to customize. If you drill out the port, you'll get the hole past the seal of the piston, ripping it with the first action.
The end caps themselfs are very thin and are not strong enough to survive extra holes.

The body isn't adaptable for more inlet holes, as only 1 side is thick enough to have thread in it.

The short stroke makes it even more difficult. With a longer stroke you could fit spacers inside, to avoid the hole-seal interference.

Cheers Mario. The only mod i was planning for the ram was to drill a 0.5mm - 1mm hole in the bottom ala FP rams so the issue would be how big and where to drill (the bottom cap can't be removed from the ram I have). However if the bottom end cap is too thin, a hole in the opposite site to the port may work just as well?

There is no advantage whatsoever in drilling a tiny hole in the side or endcap. Not for a LP setup.

I agree with Mario, on a low pressure set up, you can't have a hole. The diagram I posted works for Lp. I will be selling off my LP bits soon as I'm going HP.