SpudFiles

as hotwired said... with standarised parts you should be able to simplify the design

Have you considered getting rid of that copper part from the back of the cartridge ?? Not sure if there exist screw with such a large head but there must be something that can replace it

that's one less part for machining

POLAND_SPUD wrote:that's one less part for machining

When (not if) you get your lathe you will realise this is no trouble at all. I could happily churn out 25 of these cartridges in a single evening.

This was my first though for simplifying it, making the rear plug fixed and using the projectile as a valve:

Another variation, this time with a fixed rear plug and single o-ring sealing both forward plug and projectile. I reckon I could make this 7mm ID/9mm OD and 45-50mm long for a 0.177" projectile, giving a "realistic" cartridge size and reasonable power at high mixes.

Work in progress according to the above design, rear end plug is now epoxied in and curing, just need to drill holes for the pins.

Sorry I only post now, actually a little after jack posted "mini hybrid win" I got the I idea of combine valve less with it. Got a try, accident happened(epoxy of ne end exploded, almost killed me) so I stoped. But after make a better plan I decided to give another go. So my only concern is will the 1mm wall brass tube hold a 30x mix?
diagram, I´m also worried about the ignition, I will use a tazer, but will the spark pass a 30x mix?

Its lookin pretty good. Keep at it!

Moonbogg wrote:Its lookin pretty good. Keep at it!

Hmmm...

[youtube][/youtube]

It holds pressure well enough but couldn't get it to ignite at 10x. Eventually got it to ignite at 20x but as you can see, I missed one of the pins falling out.

Needs some work.

So my only concern is will the 1mm wall brass tube hold a 30x mix?

If the epoxy is good enough it should hold, though it might develop a leak used repeatedly at such high pressure.

I´m also worried about the ignition, I will use a tazer, but will the spark pass a 30x mix?

Make sure the spark gap is below 1mm and you should be fine.

Some further testing, took it right up to 28x and no joy. Video at 210 frames per second, if you look at the rear part of the cartridge it glows indicating combustion half way through the clip:

[youtube][/youtube]

The detent however is simply too good it doesn't help that the o-ring is compressed further by the hot gasses, increasing its grip on the BB.

According to HGDT, internal pressure exceeds 3000 psi.

The Delrin seems to be holding up well to the high temperatures.

i tried, what looks to be a similar sized oring, with a .177 BB in a penu, I was unable to get it to pop at 1000 psi... and stopped there.

I am very surprised that it did not pop at 3000 psi though!

I loled @ devilish glow

Theoretically speaking you could go past 28X and see what happens
Though I guess it would be easier and safer to use a different o-ring

ya I was also amazed about the detent power of a o-ring, even it looks and feels so easy for a bb to pass, it still needed more than 300 psi to work in my case, so now I make my detentes out of a rubber cube and worked great

jhalek90 wrote:I am very surprised that it did not pop at 3000 psi though!

Internal diameter is 3mm - 1/8", I tried using a 3mm bearing with the cartridge but it's too loose.

Theoretically speaking you could go past 28X and see what happens

I'm sticking to atmospheric pressure fuel metering for now, besides the design compresses the o-ring the higher the pressure so I don't think upping the mix is a solution.

Though I guess it would be easier and safer to use a different o-ring

The next o-ring size is 4mm ID/8mm OD so it could be done.

so if it works... how much do you charge for one cartridge ?

.117 is wimpy but a 6mm or 9mm lead BB cartridge could be pretty impressive... esspecially considering the miniscule chamber volume... I sense a possible suppresed hybrid

Damn I wish I had a lathe (envy)

POLAND_SPUD wrote:so if it works... how much do you charge for one cartridge ?

If I perfect it I suppose I could offer a limited run of say fill rig and 5 carts for under 50 euros...

.117 is wimpy but a 6mm or 9mm lead BB cartridge could be pretty impressive... esspecially considering the miniscule chamber volume... I sense a possible suppresed hybrid

That's the long term goal, really I want it to use 0.22" pellets but wanted to try something smaller because a hybrid "pocket pistol" is also on my list

Damn I wish I had a lathe (envy)

Surely you can get a good second hand deal?

Surely you can get a good second hand deal?

well yeah but that would consume my monthly income

for under 50 euros...

seems like a reasonable price

I want it to use 0.22" pellets but wanted to try something smaller because a hybrid "pocket pistol" is also on my list

who said you can't build a pistol in 0.22" calibre ? [/img]