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Modding a Pump

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Modding a Pump

Unread postAuthor: MrCrowley » Fri Mar 07, 2008 7:37 pm

Hey,

I bought a pump from Mitre10 a few weeks ago for about $15. It wasn't in a box and had no info. So I thought i'd see how high I could take it.

Got home, tried it out, hose snapped. Tapped a new hole, made my own hose, the whole thing leaks from the joints.

Today, I took it apart, all the joints came off easy with a hammer and screw driver, they weren't even bonded together in anyway. :shock:

On closer inspection I realised it had no check valve, so all the air would just leak out the handle part. So I was thinking if I installed a check valve where I tapped a new hole, JB welded it in as well as threaded. (The metal isn't very thick) And then I would clean the whole thing, JB Weld the joints back together, put on a homemade hose for it and a schrader adapter and use it as a high pressure pump.

Think it would be safe up to around 250psi? I'm sure the metal wouldn't fail under 1000psi, but I doubt the pump and piston is sturdy enough to go much higher.

Now for pictures...
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Attachments
IMG_2822.JPG
Dismantled.
IMG_2822.JPG (30.74 KiB) Viewed 920 times
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Base
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Main Body - Birds Eye
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Piston - Side On
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Piston - Front On
IMG_2825.JPG (30.79 KiB) Viewed 920 times
IMG_2827.JPG
Partially Assembled
IMG_2827.JPG (27.74 KiB) Viewed 920 times
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Unread postAuthor: ghostman01 » Fri Mar 07, 2008 7:57 pm

hey yeah ive got the same kind of pump but ive had to pull it apart and mine looks a lot older lol and it is. Hey btw what part of SA, suburb do you live in
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Unread postAuthor: MrCrowley » Fri Mar 07, 2008 8:09 pm

I live in <A HREF="http://www.nzherald.co.nz/section/1/story.cfm?c_id=1&objectid=10494046">Kiwi</a> :wink:
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Unread postAuthor: ghostman01 » Fri Mar 07, 2008 8:15 pm

ah thats right i remember now sorry i forgot since last time lol hey what do you think of my new spring pistol design http://www.spudfiles.com/forums/files/springpistol_156.gif
just whipped it up this morning
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Unread postAuthor: Hawkeye » Fri Mar 07, 2008 9:46 pm

You're wasting your time. The effort it would take would be better spent on the right stuff.
It does have a check valve. The cup style piston works the same. It flares out as you push down.
The bore of the pump is too large for high pressure and the pump rod will almost surely bend.
Those things are made for pumping up balls and low pressure bike tires.
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Unread postAuthor: MrCrowley » Fri Mar 07, 2008 10:02 pm

Hawkeye wrote: The bore of the pump is too large for high pressure and the pump rod will almost surely bend.

That occured to me just before, but I forgot to edit it in. Copper is just really expensive here, i'll see what I can do to improvise.
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Unread postAuthor: psycix » Sat Mar 08, 2008 7:31 am

Its not one of the best pumps around you got yourself there.
And as it was almost falling apart instantly when you dissasembled it, it could also be named "sucky"
Maybe you are better of building your own pump from fresh new materials.
May look alot cleaner then a broken pump with JB weld all over it....
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Unread postAuthor: bluerussetboy » Sat Mar 08, 2008 10:47 am

That piston would definitely have to be replaced. They have a tendency to fold over or actually rip in high pressure. If you were able to make a new piston out of epoxy that would probably work better. Your shaft is probably strong enough for 250 psi, but the plastic handle is definitely not. Those things break real easy.
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Unread postAuthor: jrrdw » Sat Mar 08, 2008 11:19 am

Incorparate a bigger rod/shaft into the assembly.
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Unread postAuthor: Eddbot » Sat Mar 08, 2008 11:48 am

yeah, get a wrought iron shaft, that definitely won't bend under the pressure, it'll be heavy as hell, but it won't bend
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Unread postAuthor: MrCrowley » Sat Mar 08, 2008 2:26 pm

Last night I looked over some pump desings and realised if I bought a few feet of 1/2" copper, that's pretty much all i'd need for a new pump.

I'm still not sure wheather to go 1/2" for high pressure low volume, or 3/4" for low pressure, high volume.
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Unread postAuthor: DYI » Sat Mar 08, 2008 2:53 pm

@MrC: Just how high do you plan on going :shock: BtB got a 3/4" pump up to 1100 psi, that should be plenty for most apps just as long as the check valve doesn't fail.
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Unread postAuthor: SpudBlaster15 » Sat Mar 08, 2008 3:04 pm

I've used my 0.787" bore copper pump to pressurize my coaxial BB gun to 400PSIG - and it was virtually effortless. 1/2" nominal diameter copper pipe is far too small in my opinion.
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Unread postAuthor: MrCrowley » Sat Mar 08, 2008 3:21 pm

Oh wow, I just got the impression from something I glanced over a few weeks back, that 3/4" was too high a diameter. Maybe I mistook it for 1" or something :?

Thanks for the good news :)

Edit: Got any idea with what I should do with the pump? I was thinking the 'chamber' could be used as a sawn-off shotgun style barrel :)
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Unread postAuthor: Gippeto » Sat Mar 08, 2008 3:39 pm

It's starting to sound as though there will be another pump project around here? :lol:

3/4" should be a good choice.

I don't know how BTB got 1100 psi (I'll have to look), that works out to ~535 pounds of force with .787" dia. Must be a BIG guy.

I get 400psi if I "jump on it" a bit. I'm 190 pounds.(I used type M which is .811" id.)
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