pumps and cups

[boar]

I got a speargun pump this weekend it has no head or check valve i guess it screwed into a check valve on the speargun its 1/2 bore with a rubber c cup for a piston it seals real well and breaks seal on the return stroke so in need for a inlet valve it does have a equalization hole at the top of the stroke
I havnt put the calipers on the bore yet but looks close enough to 1/2 type l  that i think the same cup would work the threads on the head end arnt npt havnt measured them yet but once i find something that fits i should have a handy little pump

also today i had to make some 2" pistons for some rams at work i made leather cups for the seals they also break seal on the return stroke and seam like they are going to work out well ill know more tomarrow got to put everything together and test it

piont of all this is whats been slowing me down on building a pump wasnt the piston it was trying to fit an inlet and exaust check valve in as small a headspace as possable in a small tube with my fingers 1 check valve makes this sooo much easier

Boar

[Pellethuntr]

 We need pics i'm a little confused...

[theairgunman]

Boar, you're a genius! I forgot all about pneumatic spearguns needing to be filled with air!  You can get a speargun pump for about $30.
That isnt what inspired me the greatest, though. Your mentioning pump cups reminded me of my Crosman 1377. The pump tube on that has a .625" ID, the same as the OD of 1/2" copper pipe. That means if I use a copper repair coupling as the pump tube, I can epoxy a 1377 pump cup on a piece type L copper pipe with a T fitting on the other end and a couple of short lengths of pipe for a grip and I've got a pump. At the very end, I'll use another T fitting, with 1/4" NPT fittings on either side, one for a gauge, the other for a check valve and QD. To reduce headspace, the copper pipe that joins the pump tube to the bottom T fitting will be filled with epoxy and a small hole will be drilled to permit the air to pass through! The biggest repair coupling I've found is 12" long, so the pump will be short enough to take in the woods. It will have 2.5x the diameter of the shock pump I normally use and 2" more stroke, giving it almost 8x the volume! This will cut pumping down quite a bit.  400 psi only requires ~123 pounds on the handle, so scrawny little me will do just fine pumping on the high end. Thanks, man you gave the breakthrough I needed! I'll post pics when I get it done.

BTW, those pump cups are available from Crosman by calling them at 1-800-724-7486 and asking for part #760-140. Order about 10 of them and you should have all you'll ever really need.

[Pellethuntr]

 Does anyone know how hight hose pumps r rated for??? I see they use around 300-400psi in there speer guns but i wonder how high those pumps can go...

[theairgunman]

I'm really not sure how high you could get one of those pumps to go. Depending on the diameter of the pump head and the quality of the materials, I imagine you could get considerably higher than what they are rated for. I've got my pump built, minus the check valve. So far it seems to work well, other than the pump cup not forming a perfect seal. I might need a new one, or go with my original design and use a floating o-ring. Here is a pic of it:

[boar]

ph ill try to take some pics tomarow  the 2" leather cups worked wonderful had a probably 95% or higher seal with very little friction to overcome everything was great till they hit the exaust port they blew out the holes deformed on the way back down i could bump it and get it to reseal but need em to work for other people they would a been great for a pump or ram with out exaust so i went back to stacked washer piston
Ag what you built is about what i been thinkin only a bit taller say 30 inches or so wouldnt be much different than carrying a few arrows

Boar

[boar]

hey ag what if you put your check valve on the end of the cylinder b4 the tee that would eleminate some headspace and maybe streamline it abit alxo the gauge would read the pressure in the gun instead of the pump tube

Boar

[theairgunman]

Thanks for the advice, it sounds good. I'm planning on putting the gauge on the airgun in the end so I can keep an eye on leaks or pressure changes due to temperature. The T fitting at the bottom is filled with epoxy, with 3/32" tunnels drilled through it for the plumbing. I'm still debating whether to make a check valve or go with a store bought one. I hate the idea of a homemade valve failing, dumping 400 psi into the pump with me over the handle.    I went ahead and made a floating o-ring head for it, it develops 3x the pressure the pump cup did in one stroke. It also develops 3x the pressure my shock pump builds in one stroke too. I've learned a lot from building this little one, I'll learn from some of my mistakes after I finish this one and build a truly great pump. lol

[boar]

I put a check valve on the speargun pump lastnight tried to keep the headspace to a minium but its still much i can only get to 40 psi its amazing how little space it takes to mess things up so maybe this afternoon ill try something else

boar

[boar]

kinda off topic but exciting my little air project at work was a success everything has been delivered and 10 more have been orderd maybe ill remember the camera this time

Boar

[boar]

well i started building a valve for the speargun pump today didnt do much but i got started

Boar

[Pellethuntr]

You gota get this thing going I am in need of inspiration...

[boar]

yeah i have completly stoped playing with the air gun till i get an air scource going but im having a blast with the sling shots

Boar

[theairgunman]

Have you been able to do anything with that speargun pump?

[boar]

I tried to work on it the other day after work but was too hot and i was wiped out i did manage to get a rubber flap cut and a hole drilled

Boar