SpudFiles

psycix wrote:Sell that damn jeep and buy a lathe. Will save you thousands of euro's usually spent on epoxy every year!

I should, had a bit of an argument with a brick wall last weekend that's going to cost me at least 750 euros to repair, think of all the epoxy I would buy with that.

Rag makes a good point about economy however, I don't spend more than 50 euros a year on epoxy - my projects tend to be on the smaller end of the scale so actual use per project is very low.

Besides, I have my lathe - it's called a drill clamped in a vice

Brian wrote:I like the fact he does things differently.Not so long ago Jack and I were the only ones doing stuff the " wrong" way.He's gotten this forum further than anybody...

In complete agreement with you there mate, when I first joined spudtech I was shocked that everyone was so happy to be constrained by the use of standard parts. There were always good theories floating around but when it came to fleshing them out, there was a lack of adaptable construction techniques. Long live two part adhesives!

That's where you are wrong.
Mine shot out only one each time.
Out of a cloud-modded elbow thingy

Interesting, my experience of BBMGs is that even a slight burst of pressure is enough to let loose several rounds. Maybe combining a pulsing valve with a ball detent is the solution.

I'll re-make the pop-off valve and move from there.

jackssmirkingrevenge wrote:You guys make valid points but somehow I'm not convinced this is worth pursuing. I've been thinking of going back to the pop-off valve, maybe combined with a blowback bolt, something like this:

Jack why bother with a seperate blow back bolt, you can just go for a combined system, which I dub the "pop off bolt"

Voila.

SPG wrote:Jack why bother with a seperate blow back bolt, you can just go for a combined system, which I dub the "pop off bolt"

That does does have a problem, in that the breech is barely starting to seal when the valve pops open.

Trying to fix that issue may then cause "the farting problem".

EDIT: Spelling stupidity.

It's no different than a BFB by itself.
It won;t work

The largest enemy of the spudder besides unrated pipe: farting problem.

You need a stepped piston with different diameters and o-rings.

psycix wrote:You need a stepped piston with different diameters and o-rings.

SPG's design is a stepped piston, in that the area of the ports is much smaller than the area of the piston.

The idea is similar to what I had done here



If the porting out of the chamber is much bigger than that going into the chamber, there shouldn't be any flatulence problems.

After all, no farting here

It was just a quick rough sketch to show how it could be linked to the breach.

I'm never certain why Jack goes down the seperate breach route it looks to me like trying to balance two seperate air/spring systems could be a nightmare, one is bad enough. But equally well he could use his design but link the piston to the breach mechanism instead of going for blow back.

We could use a rotating bolt and use the rotating bolt head as the valve. Still, flow issues, but seems OK none the less.

Ahh there's so many ways to fail aren't there?

I still like the original thing though I reckon it's got a lot of merit, just needs a way to slow it down a bit. And I was wondering, if not increased weight how about increased friction? I'm trying to think of a way to get it so that the hammer's travel towards the valve is low fristion, but the travel out is higher, I'm sure there must be ways, just can't think of any.

SPG wrote:it looks to me like trying to balance two seperate air/spring systems could be a nightmare, one is bad enough.

Personally, I'd say it's more likely to be a nightmare doing it with just one. Either way, there are two systems to balance, the valve and the loader. Trying to solve them with just one spring system will mean any changes to one will automatically affect the other.

SEAKING9006 wrote:We could use a rotating bolt and use the rotating bolt head as the valve. Still, flow issues, but seems OK none the less.

Been thinking lately of a compact rotating bolt (inside sealed chamber) that feeds by (from) a cloud chamber, then rotates inline with the barrel, And a led light (with only a pin-hole) lines up with a photocell, triggering the eletric solenoid to pilot a piston valve...
Hmmm...(?).

BTW, On my spring question earlier, I had really just wondered about it...
Now (Duh) I suppose a gauge spring could be used and the plunger measured with calipers or micrometer, then the surface area could be scaled down(/4, /8...) for higher pressure (same travel). Still a seperate aparatus would probably be needed for testing though. 8)

More on topic,@JSR I like Your bolt design a few replies back,
But for that small scale (or larger), maybe a "+" shape with a "-" prutruding from the middle could be installed (inside bolt chamber),
then the bolt loader tube could strike the valve itself.
The front of the "-" would be pointed and block flow until loading.
And the loader tube would have slots to fit around the "+" to strike the valve behind it.
And washers to make up the piston part bolted on the loading tube. (That's generally my own modification to your BFB design)
DANG I need to learn paint or get time to post drawing pic.... 8)

Double, but I forgot to mention that for something as small as a shrader, an alarm bell curcuit (The kind in school walls with a hammer that strikes a bell (Or two) would most certainly work well.
And you'd need a lot less dead space in the tube.

I had an old hobby book with a schematic, It's an electro-magnet (or two) in front of a flat piece of spring steel, with a hammer on the end.
For DC it has a cut-off pin. For AC it doesn't need one.

Should work fine for a shrader, But it's electronic.

BTW, with the revolving loader I mentioned, It should be as small diameter as possible (for slower surface speed).
I figure, if it holds ten and revolves 100 RPM, that would be 1000rpms,
And a 6/10th sec in line plenty time...I just DK about the LED or photocell accepting PSis though

I love the way you let your imagination run away with you but there are far simpler ways of doing this, I think pop-offs are the way of the future and I'm definitely on the right track

Thanks again JSR.
Geez I'm away for like two days at a time and looks like you've made about 50 breakthroughs!!!
Awesome!!!

BTW, I was also thinking of one way gearing to slow down the cycle.
And also a block bolt moving horizontaly by a magnet, and fired by electronic solenoid pilot.
Course now there's plenty of (better) mechanical stuff to study!
Thanks. 8)

Oh, I plan to build a simple Blow forward bolt example from standard threaded parts soon to post hopefully. 8)

Double (but new info/ques.):
I really like this design,:

But I think it could be simplified (Greatly)
For one the entire barrel or internal barrel sleeve could move backward to strike the valve.
That way the spring could be mounted (externally from bolt) at the end of the barrel (perhaps inside a flash suppressor looking shroud or somewhere along the barrel).

Also the trigger (sten gun lever type) could be fitted any position along the barrel (or sleeve)

For simplicity also, The back of the barrel would be blocked off and the gas would flow through holes in the sides of barrel rather than breech.
(Same as diagram shows)
The blocked off back off barrel would strike the valve,
RATHER than a blocker pin, a pipe the same length as blocker pin would be fit externally over barrel and vent holes (rather than internally).

I was stuck on ammo feeding with this design but it could feed at the same position into a slot as a solid blocker pin and seperate loader tube!!!
Course rate of fire/bounce will probably be so high it will need a strong mag. spring or even pressure loaded mag (a cloud for magazine).
I was thinking maybe one of
THESE and a small tank 88gram size, homemade valve with plasic, spring and ballbearing, and few brass fittings: Simple nipple pipe,coupling.
Light machining for trigger fitting(upgrade sear later for semi...) and of course a spring. 8)

EDIT: DANG, I had about 2 min.s on-line(then sec.s) when I typed that so...
Anyway it's basically the same thing as diagram with a few changes is all.
(tempted to take time off other JSR type BFB project...but probably won't) 8)
OH, also the barrel I linked to was just how I thought of that, (a straight airgun barrel might work a little better .002 diameter difference).