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My wee wibble shock pump

Unread postPosted: Sun Dec 28, 2008 11:13 am
Author: Sticky_Tape
This is a pump I made. To save time and my fingertips I mad a video about it. Tell me what you think. BTW did I get the calculations right? Anybody think this would be good for pen/marker guns?[youtube][/youtube]

Unread postPosted: Sun Dec 28, 2008 11:27 am
its looks all right... but i would have made a largeer bore full size pump as it would still be capable of the higher pressures... it would just get there faster.

Unread postPosted: Sun Dec 28, 2008 11:32 am
Author: Sticky_Tape
I wanted it to be concealable and small not big and bulky. I can easily fit this into my pocket and carry it around. It's just fun to have somthing james bond like. BTW this is for tini guns like pen guns and marker guns not full sized guns. What would be the point of a concealable pump coupled with a unconcealable gun?

Unread postPosted: Sun Dec 28, 2008 11:39 am
ok, its cool then... have you actually tested it out yet?

Unread postPosted: Sun Dec 28, 2008 11:42 am
Author: Sticky_Tape
Not on a gun but I know it works I will get a video of it working in a sec.[youtube][/youtube]
EDIT: My thumb is acting like a check valve you can hear the air.

Unread postPosted: Sun Dec 28, 2008 6:37 pm
Author: Gippeto
A great idea for the pen guns Sticky. :)

Your math is fine, but your dimensions are a bit off.

1/2" type M copper is .569" id.

That works out to a swept volume of ~.7 cu in with a 2.75" stroke.

It'll take ~76 pounds of force to generate 300psi.

Unread postPosted: Sun Dec 28, 2008 6:38 pm
Author: Sticky_Tape
That won't bee too hard by arms will it? I hope not. EDIT: uh oh is type m thicker than type l?

Unread postPosted: Sun Dec 28, 2008 6:44 pm
Author: Gippeto
I don't know. A larger pump handle may be in order.

The wall is thinner on type M

Have high speed?

Big file, but worth it for working with copper IMO.

pg 27 IIRC ... ndbook.pdf

Unread postPosted: Sun Dec 28, 2008 6:49 pm
Author: Sticky_Tape
Doof! It's actually type L oh well I don't think I will be making another video.

Unread postPosted: Sun Dec 28, 2008 8:16 pm
Author: sputnick
What is the shaft made out of? it looks a little flimsy, i would have used an aluminum tube with an OD about 1 or 2 mm off of the ID of the copper pipe, then maybe plug it with hot glue or something.

I like the idea with the floating O-ring, but wouldn't you just be able to make it a tight fit from the start? If you were just to use that with the full metal tube, then it would be a little more sturdy, then you could use your foot for higher pressures.

Unread postPosted: Sun Dec 28, 2008 8:43 pm
Author: skyjive
Type M and L copper have the same OD so you can use the same fittings that fit around them, but L has a thicker wall so a smaller ID

Unread postPosted: Sun Dec 28, 2008 8:51 pm
Author: Sticky_Tape
I knows that all BTW Spudnick did you ever play with bondo fiber glass resin before? Cast some in a 1/2'' copper pipe take it out and try to snap it betcha' can't :wink: I was trying to make it a tight fitting o-ring but I found that it was alot easier to make it a floating oring. It works perfect so why do anything else?

Unread postPosted: Mon Dec 29, 2008 1:38 am
Author: Dgealy
Im not sure this will work. I just made the exact thing today. Maybe yours pumps enough air, but mine was only able to do about one pump to overcome the schrader valve. The pressure inside my pen gun coupled with the spring in the schrader meant that even though i pumped, there was enough dead space for the compressed air to fill up before the schrader. (Almost nothing though). And because i had a floating o-ring, the second i loosened the tension, all that air i had just compressed would just fall backwards.

I made mine out of 6 inches of 5/16 " brass tubing. (Leftover from my pen gun).

I'm remaking my pump, but I'm going to make it much longer so it will pump more air, so the air to deadspace ratio decreases.

Unread postPosted: Mon Dec 29, 2008 12:25 pm
Author: Sticky_Tape
You need to make the deadspace as small as possible so that you are trying to compress the volume of air to the smallest possible volume.
EX: 1 cubic foot (0 psia) compressed to 1/2 cubic foot = 14.7psia
VS. 1 cubic foot (0 psia) compressed to 1/4 cubic foot = 29.4psia
1 cubic foot compressed to 1/4 cubic foot gives more pressure towards opening the check valve because 1/4 cubic foot is smaller than 1/2 cubic foot. 5/16'' Is smaller than 1/2'' I'm sure yours has less dead space than mine but yours probably has less stroke volume. Are you sure you have a floating o-ring can you give pictures?