fibreglass the PET bottles and they will last up to 150psi, the rams jeff use apparently work at that pressure, but el b had some bungee cord to stop the flipper travelling too much and blowing out the rams.
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For El bravo I use two 1.25 litre PET bottles. They were fine at 100psi but to go higher with confidence I covered them in fiberglass and also the caps were filled with epoxy before being screwed on so they don`t leak and won`t blow off. I plan to give them another layer of glass; three all up and within the safety of the arena, pump them up to 200psi and then have another bot bash them around a bit. Then, if there`s no big bang! I`ll feel safe to put them up to 150 psi regularly.

The rams are the larger size, easily available black bike pumps I found in K Mart. The shafts have a dowel pushed inside them for extra strength, after you cut off the handle. At the base I made an aluminium box section about three inches long and extending one inch past the end, forget the old rubber hose and drill and insert an 8mm OD air hose, use a little plastecence to block any leakage points ( the four corners of the box section then fill that up with more epoxy to make a solid mounting base. Drill a hole through the base for a pivot pin and absolutely! use some strong cord on the flipper to stop the rams from exceding their full stroke and blowing out the ends.

With any rams like that, treat them with the respect you would a gun, NEVER put yourself in front of a loaded barrel!

Philip has the most powerfull featherweight flipper I have ever seen but the CO2, very high pressure, "proper" parts etc. scare me just a little too much!
He has taken a year or more also to develope it. He knows exactly how to do it safely.

Cheers,

Jeff.

r u talking about the hand-held pumps or the ones that stand upright??

hand held ones IIRC, the original ballistic used one of those big upright things, worked okay for a while but i think it damaged it at the engineering festival.

any pump would work i guess. except those foot pumps as the one i have has a spring inside the cylinder and you cant open it up to remove it, not sure about the newer ones.
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Yes, the hand held ones. First I used the standard plastic ones that come in various colours, they worked fine but then the bigger, black ones.

Iv`e checked out the tech pages, calculations and formulas and then usually do a bad Homer Simpson impersonation Then I just use a little logic and common sense to knock up something that works.
Each rebuild, I usually modify a bit and find an increase or decrease in power, so learning all the time.
All fun!

hmm all this talk is getting me interested in them for the wood robot..

how do you think youd go about making a compressor powered lifter mite-e-er style, retract the ram? i can see how making the compressor turn on would extend the ram but not how you could retract it unless the air slowly sort of bled out of the cylinder slowly when the compressor turned off... any suggestions? would it be possible to use one of those solenoid sprinkler valves and tie it in with the compressor so when its off the thing vents and when its on it pumps up the ram?

looking at a bike pump they seem to be just a pvc cylinder or some sort of material like that.. i reckon you could find a piece of ali tube at bunnings or a random piece of steel pipe the right size to replace it with.
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Marshal used a 2/3 Valve in Mite-e-er
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I suppose I would use something like I did already. a servo switches on the compressor. Then, when switched off, the servo depresses a valve to vent the air. Mine did work, only the valve has moved.

The downside to Mite-e-er was the dead givaway; when you hear the compressor start,,, RUN AWAY!

quote:

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The downside to Mite-e-er was the dead givaway; when you hear the compressor start,,, RUN AWAY!

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what about the metal upright one that sits on the ground and u use both hands on the top??? what do u do whith the built in valve that stops air getting into the ram???

put a drill through it
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quote:

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Originally posted by Glen:
looking at a bike pump they seem to be just a pvc cylinder or some sort of material like that.. i reckon you could find a piece of ali tube at bunnings or a random piece of steel pipe the right size to replace it with.

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125mm is a fairly massive ram.. i would have thought PVC would bust apart as the stuff is pretty fragile. apparently not hey.

ill make a run down to repco later and see if they still have those A/C valves, hopefully they do, ballistic seemed to work great with it.
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what about the metal ones. couldnt u just unscrew the bottom and screw on an end cap??

Last edited by wilko on Sun Oct 16, 2005 11:22 am; edited 1 time in total

contact gary (rotwang) and ask him what he did on the first ballistic, it had one of the big upright cylinders.
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