SpudFiles

This is a gun I made a few days ago, together with a friend. A second one is being constructed in a while. (you can see the basic system lying in the background)

It uses a piston valve mad out of an aluminium tube, with a bicycle inner tyre epoxied on. The rubber doesn´t get cut.

The pilot volume is about 1.5 - 2 ccm, and it is filled and piloted by a presta valve.

The chamber is a 25 cm long 12 mm OD 10 mm ID copper pipe.

The barrel is 8 mm OD 6 mm ID aluminium tubing.

I use the gun up to 11 bar (160 psi) right now. Power isn't great, but when I get a shock pump things will be better

Again, nice!

Labtecpower wrote:I use the gun up to 11 bar (160 psi) right now. Power isn't great, but when I get a shock pump things will be better

I'm in EXACTLY the same situation right now. The parts for my super-simple track pump come in sometime tomorrow. Just a tip, I found that a lot of bike shocks come with a pump for maintenance, but people turn around and sell those on eBay because they've got a (admittedly) better pump. Might be something to look into...

Very nice for just a plinker. It looks like loads of fun, while being perfectly ergonomic.

Kudos

looks great, I'm sure the power will match when you bump up the pressure.

I'm curious to see how similar the next one is to the original, for me at least, my designs are hardly "mass-produceable" due to improvisations to make the design function correctly, and of course human error.

The second gun will be pretty similar, but the sizes will be somewhat different. The whole gun is made in a way, that it fits like a glove, and for every person, the dimensions differ.

Before I start with it, some multiply is needed. It may take a while to build it.

Maybe i'm going to make my own pump, shock pumps take a long time to pressurize a chamber, from what I heard.

Looks good but I think you missed an opportunity to make it much more compact, but judging by the size of your photos I see compactness is not one of your primary concerns

Labtecpower wrote:Maybe i'm going to make my own pump, shock pumps take a long time to pressurize a chamber, from what I heard.

With the small chamber on this gun (only 19.6 mL), a shock pump shouldn't be too hard to use. However, if you plan on increasing the size of your air chambers down the road, a track pump configuration is much better. Have you seen Gippeto's pump tutorial?

I just saw it. If I have the time, i'll machine one out of aluminium or something..

Hey, nice gun!
I'm planning a similar one. Does the valve do its job as pilot? I couldn't decide between a blowgun and the valve like you did?! I think the solution with the valve has an advantage because theres only one hole to fill and exhaust, and less place for leaks.

Nice regards from Germany!

Hello neigbour!

The valve works perfect as a pilot. One very important thing is that your piston fits very well. Mine has a 0,01 mm gap. (for size comparison: that's about 1/5th of one of your hairs)

Also make sure that you have a very small pilot volume.

This design is very easy to get leak-free. With my copper gun I had very much problems with a leaking blowgun and piston. (now it is completely leak free tough, I machined myself a nice nylon piston)

This is a pretty weak design at low pressures. I think things get interesting past 300 psi.

Labtecpower wrote: One very important thing is that your piston fits very well. Mine has a 0,01 mm gap. (for size comparison: that's about 1/5th of one of your hairs)

.01mm = .00039"....That kind of tight tolerance requires pretty good machines and skills. Just curious but with that capability, why are you not making your builds using mostly machined parts?

velocity3x wrote:.01mm = .00039"....That kind of tight tolerance requires pretty good machines and skills. Just curious but with that capability, why are you not making your builds using mostly machined parts?

Perhaps it is a cast piston

Gun Freak wrote:Perhaps it is a cast piston

... or perhaps since

Labtecpower wrote:It uses a piston valve mad out of an aluminium tube, with a bicycle inner tyre epoxied on.

...then he's using telescopic tubing

it's a piece of high-precision tubing.

bragging

I'm able to machine in tolerances that tight... for my copper gun I machined a nylon piston with a gap just as little as this one.

For my qdv, I made a piston wich was EXACTLY 42.00 mm. The imperfections were in the 1/1000th of a mm range.

/bragging

The only reason I don't machine my guns entirely, is that it costs too much time. It's all done on a hand lathe, but in a few years I will be able to make things on a CNC lathe & mill.

I hope you're not planning on buying a CNC shop just for hobbies.

Pistons don't need to be very tight, actually. You can easily make up the difference with a couple of o-rings. If you're just relying on a close fit to take care of your equalization, the tolerances required are nowhere near 0.01mm... more like 0.1mm