Pneumatic Cylinders on ebay - any good?

http://www.ebay.co.uk/itm/25mm-Bore-...item43aa4aa7a7

Are these any good? I`m thinking of running two together.

http://www.uxcell.com/i/11c/ux_a11072200ux0169_ux_c.jpg

There ok, I used one yeaaaars ago. Looks like it's the kind with screw in endcaps.... Best thing to do as an upgrade is remove the endcaps.. Then inside the port for the fitting there will be a hole around 2mm dia... Drill that out as large as possible as it's a major flow restriction.

You won't get the best flipper around with them, but it will work.

they will work but from what i know about flipper, you ideally want something around 40mm bore

Not really if using two.

Basic equation for working out cylinder force; (pie x radius squared) x the pressure your running in bar.... So you'll be looking at around 30kg of force per cylinder... So overall 60kg before losses due to mechanical advantage. ...so pivot the cylinder on the flipper arm close to the tip... Further away from the arm pivot the better.

yeah davindras right, you want the rams pivot more towards the very front of your flippers arm but at the same time you want to try get a 3:1 ratio with the 1 part at the pivot side of the flipper arm for the most effective weapon.

my flippers got a more 2:1 ratio so its good but it could have been better

Thanks for your help and advice etc. I have now bought a 100 stroke x 40 bore Festo, it weighs over 1kg but looks fairly substantial.

A usable size. Don't expect world shattering achievements tough.

no but if the weight is ok (and the system actually works!) I`ll probably add another.
Its all new tech to me.

you'll have something that turns robots over at least so it'll be alright, nothing more confusing then usin pneumatics for the first time lol are you using a buffer aswell?

yes I`ve got a buffer tank, at the minute its a 1kg powder extinguisher unless something else come along before I`ve built it. What size cylinder is 'average' would you say?

i wouldn't say theres an average size, depends on the size of the robot and whether you'd use 2 etc

personally i'd just use the one thou because another rams just adding extra weight, ive got a 50mm bore ram in mine

do your pneumatics so that your buffer tanks piped as close to your valve as possible aswell

ok thanks.
I`ll soon have all the main bits so I can start building.

Looking at 5/2 valves, are the 1/4 ok? I was planning on 1/2 for best flow rate but they seem a fair bit bigger than ones I`ve seen people using. I thought 1/4 would be too restrictive?

i use 1/4 valves cause i can't get any bigger off the techno bots website lol but yeah they are ok

Thanks Calumco, now bought.

use 12mm pipe aswell from your buffer to the valve and from the valve to the cylinder if you can. you'll be surprised at the massive difference in power.

took a pic for you of some pneumatic stuff I've been playing about with for something i wana make - i know i haven't got a relief valve connected to the pipework but shhh lol

[attachment=0:2q2qzil4]BILD0002 (2).JPG[/attachment:2q2qzil4]

from the bottle its 8mm pipe then going up to 12mm for the buffer and the rest. its only 8mm pipe from the valve to the cylinder for now because i didn't have the right fittings lol

just from adding a buffer and using the larger dia pipe its changed the cylinder from acting like a lifter to jumping off the floor when i fire the valve

post another pic once you have the prv in calum? ill save it as its good reference for a LP diagram thing :lol:

just tee off a section of the 8mm pipe before the pressure gauge and have it in there

normally when testing ill have all the pneumatics in the robot but swap the prv for a gauge so i can get the pressure set right then once it is, ill just swap the gauge back to the prv

Where do you get that bottle you are using for your main tank Calum?

the 2 smaller 600g black bottles that aren't connected to anything are from johnno

and the bottle i'm using in the pic is a 2kg bottle i bought off kenny ages ago

or did you mean the buffer? that's off grant cooper

Thanks. I can appreciate the large diameter pipe making the difference but doesn't the 1/4 of the valve restrict it back again?

Yes.

8mm o.d. pipe should be fine.

Your aware that 1/4 ... when applied to pipe fittings ... has got nothing to do with the actual thread measurement... it is taken from the nominal bore of the pipe.

ok, I`d read something about pipe threads (I think it might have been on your site!) but didn`t associate it with the valve sizes. Should be ok what I`ve bought then. Thanks

Google your valve part number ... you should be able to find it's flow in l/min or Flow coefficient... Cv Kv.

EDIT...The 1/8 1/4 1/2 etc when applied to your valve is the BSP thread size in the port...it could also be American..NPT