Pneumatic questions, sorry!

I am just starting to think about my next robot and like the idea of a featherweight pneumatic flipper. I have read through a lot of the old threads but am still left with some questions. I still don't understand what the stroke and the bore mean? Also I remember seeing a link to a great website on pneumatics in combat robotics but I can't find the link, does anyone know what it was? I was also wondering if you realy need a buffer tank because due to my design i can only fit in either 1 main tank and 1 buffertank or 2 main tanks which i think i will need to get plenty of flips(i am thinking of
Using p16oz paint ball gun bottles) I am sure that more questions will follow soon but thanks for now.

Stroke = how much the ram goes up and down
Bore = what the diametre of the inside of the cylinder is.
website = http://www.teamonslaught.fsnet.co.uk/co2_info.htm
go to an event ask around about pneumatics, thats how I learnt :proud:

I think stroke - is the travel distance of the piston
I think the Bore is the diameter of the cylinder - this is important for working the power of your flipper etc.
I would say a buffer tank is needed as it will feed your 5/2 valve quickly and allow your piston to stroke.

LINK http://www.teamdavinci.com/understanding_pneumatics.htm

edit - someone can type faster than me :lol:

Thanks for the super quick responses guys! Both of those websites look great i will have a look at them tonight. Another couple of questions, what's the difference between an fp and a hp system. Also if you are using fb am I right in thinking that you don't need a regulator?

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Originally Posted by Max

Another couple of questions, what's the difference between an fp and a hp system.]

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Nothing they are both the same.

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Originally Posted by Max

Also if you are using fb am I right in thinking that you don't need a regulator?

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Yes you are right.

Also you may want to bear this in mind, these pressure levels (fp) are very high which are very dangerous.
Its best to start off with low pressure (LP) and then work your way up.

Sorry even more questions, if I was using a fp system then would I need a buffer tank as all the pressure is released instantly (no regulator)?

Yes.

I'm not the best to answer questions about pneumatics, but don't think you would NEED one, but it would help.

Ideally the volume of your buffer should be atleast 3 times the volume of your pneumatic cylinder

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Originally Posted by Max

I am just starting to think about my next robot and like the idea of a featherweight pneumatic flipper.

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Great, Join the Club.

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I have read through a lot of the old threads but am still left with some questions.

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Who doesn't?

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I still don't understand what the stroke and the bore mean?

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Like in combustion engines, bore and stroke are what make up the volume in a cylinder.
Stroke is the distance the piston can travel. Bore is the diameter of the piston (and that is the same as the bore -minus a few 100th of a mm- of the cylinder it travels in). Diameter dictates the surface area. In case of a normal cylinder that is Radius (half diameter) * Radius * Pi (3.14 to be fast).
Surface of piston in cm² * pressure in bar = force in kg.

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Also I remember seeing a link to a great website on pneumatics in combat robotics but I can't find the link, does anyone know what it was?

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Several websites qualify in that respect.
But for Robot Wars, I have posted these in the past
http://www.dutchrobotgames.nl/index.php ... &Itemid=70
http://www.teamonslaught.fsnet.co.uk/pneumatics.htm

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I was also wondering if you really need a buffer tank because due to my design i can only fit in either 1 main tank and 1 buffertank or 2 main tanks which i think i will need to get plenty of flips(i am thinking of
Using p16oz paint ball gun bottles)

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Hannibalito III uses a Full Pressure setup, Cutlet/Gravity style with 12 oz main bottle and a buffertank, still we achive 15 flips or better. Amount of flips depends on stored CO2 and volume of cylinder.
I doubt that there is any feather using 32oz CO2.
An option is to use a 16 or 20 oz main bottle and a reasonable buffertank. I aim for 3 times cylindervolume in the buffertank.

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I am sure that more questions will follow soon but thanks for now.

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Please do.

Hi again and thanks for the replies. Just wondered what size rams most people use in feathers and how much force they try to get at the tip of the flipper arm(after leverage)? Also how far does the tip of most flipper arms move to get a decent flip?

could i use this ram:
https://www.easupplies.com/SPEEDAIRE-MD ... pn1eg1.htm ?
i would be using it at 10 bar.
i would put in a diagram but dont know how

here is the diagram:
http://fightingrobotpics.webs.com/ap...toid=132027416
or if that doesn't work it's on here:
http://fightingrobotpics.webs.com/apps/ ... =132027416

I'm not expert on pneumatics but I'll tell you that the ram you have there is far too small to be of much use in a featherweight. If you are looking for a low pressure ram (up to 16 bar), I have one kicking around 50mm bore, 100mm stroke for 25 quid plus postage. PM if interested.

Hmm, how to tell this.

Tip force.
FP is a kind of speciality of me.
I'm happy with Hannibalito III. Ram is 51mm bore *85mm stroke, leverage 3.5 to 1.
This means, theoretical, 2.505*2.501*pi*55=1083 kg of force , with a tip power of 310 kg over 300mm.

Hannibalito I was on the low end according to me. 32mm *bore 80mm stroke. Leverage 3 to 1.
150kg tip force, over 240mm

A LP 50*45 ram, with a leverage of 1 to 1 gives you 150 kg over 45mm. (less than a fifth of the smaller FP ram of Hannibalito I)

What if I used 2 of those rams side by side and then used a leverage of 2 to 1. Would that then give me the same amount of force and twice the movement at the tip of the flipper arm? And would this be enough for a decent flip of a featherweight robot?

Such 2 of those rams still have less than half the power I see as a minimum in a featherweight.

buy the one typhoon_driver has for sale. That'll solve everything and be of the relevant size of ram that is required for featherweights.

It's Gary :rofl:

could i use this ram in a fp system (giving me 1000kg of power)with a leverage of 3 or 4 to 1? would the ports be big enough?

No, the ram is max 16 bar. Full Pressure is 60 bar

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Originally Posted by maddox10

Hmm, how to tell this.

Tip force.
FP is a kind of speciality of me.
I'm happy with Hannibalito III. Ram is 51mm bore *85mm stroke, leverage 3.5 to 1.
This means, theoretical, 2.505*2.501*pi*55=1083 kg of force , with a tip power of 310 kg over 300mm.

Hannibalito I was on the low end according to me. 32mm *bore 80mm stroke. Leverage 3 to 1.
150kg tip force, over 240mm

A LP 50*45 ram, with a leverage of 1 to 1 gives you 150 kg over 45mm. (less than a fifth of the smaller FP ram of Hannibalito I)

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Yeah, I don't understand that leverage ratio.
Isn't a upward flipper a class 3/C lever, at a mechanical disadvantage but increased tip speed?

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Originally Posted by psychostorm

No, the ram is max 16 bar. Full Pressure is 60 bar

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For full pressure (1000 psi/70 bar max, but CO2 at 20°C is only 55 bar, and that will drop if it cools down during use) use you have 2 options. An hydraulic ram is strong enough to take the forces involved and is allowed. Or else a custom FP ram, with the right credentials. These custom FP rams don't grow on trees.

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Isn't a upward flipper a class 3/C lever, at a mechanical disadvantage but increased tip speed?

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Correct. Diminish force to gain speed.

sorry, meant to put in link to this ram:
https://www.easupplies.com/MILLER-50-TN ... hy1534.htm
this one is hydraulic so is rated high enough bu same questions again,

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Originally Posted by Max

could i use this ram in a fp system (giving me 1000kg of power)with a leverage of 3 or 4 to 1? would the ports be big enough?

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also, how do you weld hardox and is it the same weight per volume as normal ild steel?

At that price you might aswell get a custom pneumatic cylinder made.

You weld hardox using the same methods for mild steel. Effectively yes it has the same density but type hardox density into google and you will find the exact value (it's late and I'm too tired to bother)

I am hoping to be able to get a similar ram at a reduced price from my dads friend. But are those ports big enough if not what size do others use?
So for hardox can you buy special 'sticks' for use with an ark welder? Also where do people get it from?

http://www.google.co.uk/search?q=hardox ... =firefox-a

Seriously, google is your best friend

You can just use regular mild steel welding electrodes (sticks) to weld it

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Originally Posted by Max

could i use this ram in a fp system (giving me 1000kg of power)with a leverage of 3 or 4 to 1? would the ports be big enough?

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[attachment=1:3sswlq30]calc.jpg[/attachment:3sswlq30]

The cylinder you linked to has a Port Size #4 SAE = 0.172 min dia
http://www.inserta.com/PDF/AI-STR-THD-PORT-DIM.pdf
[attachment=0:3sswlq30]cv.jpg[/attachment:3sswlq30]

All the above is just a rough guide .... real world has many other variables.

EG ..Can you open the supply valve fully in less time than the math value for the ram extension time?

that table is awesome! but what is Cv flow?

Cv is a flow value / rating ... a measure of how well the fluid / gas flows thru the pipes / orifices.

http://www.ranteng.net/?page_id=12

You'll also find the info in my webpages.

http://www.teamonslaught.fsnet.co.uk/co2_info.htm
http://www.teamonslaught.fsnet.co.uk/pneumatics.htm

Can't you get smaller sheets of hardox (smaller than 6m x 2.5m)?

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Originally Posted by Max

Can't you get smaller sheets of hardox (smaller than 6m x 2.5m)?

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Yes, you can, but not in the 3.2mm thin plate we favor (and thinner isn't made by SSAB). Most steel-selling firms can deliver 4 or 5mm plate in 1 by 2 meter sheets. Weight is 7.85kg per dm³, so a 4mm thick 2m² plate is 64 kg , aboutish a £8 per kg, so, you know what to expect.
Also, asking a firm to cut up a standard plate will cost you. In most cases, the difference between buying a half plate or a full plate won't be enough to justify the half plate.

On welding hardox. There some things you need to take in account. Hardox becomes a low alloyed steel when heated over 250°C for a prolonged time. Unless you use the specified rods, you will get less strong welds, and a heat affected zone what is not as strong.

I weld my hardox with TIG, high amp setting for high speed welding, and use AISI 1.4571 rods (316 ti). That will lower the hardness in the weld affected zone, but the tensile strengts keeps up.

you can get 3.2mm offcuts from a company called abba commercials for £50/sq metre minimum order quantity 1 sq m :)

Abba commercial you say?
If you insist:

http://www.youtube.com/watch?v=OMXL62VVr2k

:lol:

here's a link to there website: http://www.abbacommercials.com/home.aspx

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Originally Posted by jonny

you can get 3.2mm offcuts from a company called abba commercials for £50/sq metre minimum order quantity 1 sq m :)

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Handy, and £50 per 24 kg is damn cheap.

Thanks for finding that company, do you just call them/email them and ask for a sheet of Hardox?
And back onto pneumatics, why are rams always much longer than their strokes by at least 50mm? And is there a way to reduce the height without reducing the stroke?

the reason a 50mm stroke ram is longer than 50mm in height is because you have a wall at the bottom of the ram, the port height, piston width then the 50mm between the piston and the top cap ( thats why its called 50mm stroke because the piston can move 50mm in that gap) and then the width of the top cap

Most commercial pneumatic rams have several parts that increase total length of a ram compared to the stroke.

Some types of ram are ment to be as short as possible.
Others can be 100mm longer than their stroke because they got adjustable soft end-brakes , locking brake and so on.

Hydraulic rams are another matter, and these have wide pistons with a lot of sealing surface, and linear guides in the head to cope with the forces exherted on the rod.
Also, to contain 3000psi of pressure ,you need serious end caps and a very solid way to connect everything.

All good reasons why so many people with pneumatic machines use custom, or at least customized rams.

they only sell offcuts they have though should be large enough for feather use. just email them asking what 3.2mm hardox offcuts they have lying around