3/2 pneumatic valve help

**geeza** · 23rd April 2013, 21:44

I use a 3/8" valve in the heavyweight I'm sure it will be ok for a feather. But check the manufacturer website for flow rates.

**Danjr1** · 23rd April 2013, 22:04

ive got a feeling that without a buffer, the system i had in mind wouldn't really fire quick enough to be effective. I never considered what Liftoff said regarding the size of the holes in the on/off valve, paintball reg, 3/2 valve and the cylinder itself and what that can do to the flow so id rather not commit to buying all the other parts without really knowing how effective the system would be.

Edit* just used a flow rate of 1500 litres per minute for the valve and guesstimated 600 litres per minute for the reg. Can someone just clarify if im in the right ballpark for both figures?

Cheers

Dan

**Liftoff** · 24th April 2013, 14:35

Dont know if those figures are correct, but what I'm sure of is that the regulator flow rate is really low, it takes about 2seconds to fill the buffer tank up to 8bar, that's too long. The regulator will be your weakest link as all will depend on it, its useless having a ram and valves with large ports and high flow rates if air is just trickling through the regulator. If I were in you I'd go for a 5/2 valve with buffer and QEV set up. It's not so complicated as it sounds, and parts should not cost too much. I'm currently replacing a similar set up to a more compact one on my robot, have a look at my build diary, there are all the parts used (mostly off ebay). If you need any help on how to build it or anything else I can guide you. I will be rigging the new set up for a test fire soonish....results might be helpful for you.

**Danjr1** · 24th April 2013, 19:50

Cheers mate, ill keep a watch on your build thread. I've had another go at the design and its now got a 9oz main tank, 9oz buffer still with the 3/2 valve. I wanted to use a full steel monocoque chassis but ill change for 8-15mm HDPE for that.

**Liftoff** · 25th April 2013, 14:11

That's the way to go, just a small note regarding the buffer, I think the 9oz bottle is small for the ram you mentioned earlier. A 12oz bottle will be better suited.

**Danjr1** · 25th April 2013, 16:30

the 9oz should do according to the spreadsheet. its just under twice the capacity of the ram. Any bigger than that and the robot will end up massive and complicated to plumb.

**Liftoff** · 25th April 2013, 19:46

hmmm, twice the size of the ram is on the lower side... I'd be more confident with a 3:1 ratio, otherwise you will have a large pressure drop. Maybe someone else can confirm this. Btw, the difference between a 12 and a 9 oz bottle is not that much, the 9 oz bottle measures 26cm by 5.5cm dia. the 12 oz is 26cm by 8cm dia. Regarding plumbing, if you select your components wisely you can fit the whole system in a very tight space and keep weight to a minimum.
Just as an example in my first version of my robot I used 1/2" fittings and valves throughout, need less to say the system was heavy and quite large. The new redesigned system uses mainly 1/8" fittings and valves and only where necessary did I use 1/2" parts. This way I'm to loose about 1.3kg off the pneumatic system!

**Bacon Wizard** · 25th April 2013, 19:53

Originally Posted by Liftoff

The new redesigned system uses mainly 1/8" fittings and valves and only where necessary did I use 1/2" parts. This way I'm to loose about 1.3kg off the pneumatic system!

This didn't adversely affect flow-rates?

**Liftoff** · 25th April 2013, 20:14

Not necessarily, you only need good flow (large fittings) from the buffer tank to the ram, all the rest does not have any effect on flow. So the main plumbing and valve can be made as small as possible. The only downside I can think of is slower buffer recharge time, which I can live with.