SpudFiles

Hmmmm makes sense but I still that a bit of extra travel would be beneficial....

Why?

or rather, por que?

Beyond the magical caliber/4 figure, you are getting absolutely no extra advantage in flow - simply increasing pilot volume, and also expanding the size of the air reservoir which in turn lowers the pressure.

'Cos it saves the gas going right around and then in,
Chances are you can't get exactly d/4 and so it's best to err on the side of performance.

Only talking about an extra 5-10mm not lots....

Michael

Gepard wrote:'Cos it saves the gas going right around and then in

Sorry for being such an efficiency nazi but I can't stand waste. In practical terms, a few mm won't make *that* much of a difference, but since air is a limited power source compared to solid propellants, it makes sense (for me at least) to want to extract every available ft/lb from a specific launcher.

No matter how much the piston moves back the air in a coaxial is still going to have to change direction to exit through the barrel, I don't see how it will improve performance to have the piston move back further.

We talking about a co-axial? I thought we were talking about piston valves in general......

Michael

Gepard wrote:We talking about a co-axial? I thought we were talking about piston valves in general......

Michael

Does it matter? The air still has to turn around 180°.

I don't see the need to carry on this thread....

Where does it go round 180 degrees in a 'normal' piston?

Michael

Gepard wrote:I don't see the need to carry on this thread....

Where does it go round 180 degrees in a 'normal' piston?

Michael

If you have an over under set up like the majority of the barrel sealing piston valves that have been made, the air goes through two 90° bends. It's not an immediate 180° turn. But some of the air, such as in the pilot area outside of the barrel, does have to make a 180.

Edit: I just noticed Jack's avatar being animated, maybe I'm just retarded though...

Ah - true, but I was refering to the flow of the gas from the chamber to the barrel through the piston.

Michael

Hi jack.....

for 1/4 of the caliber of travel, you get an available area of 2*pi*r*h, in this case 2*3.142*0.5*0.25, which equals 0.7855 in 2

You have a hangover all right.

What's pi doing in the formula for the area of a rectangle? Your valve passage is really pi times smaller than the barrel cross section.

Gepard:

Where does the 90 come into it?

I must ask you that? You were the one who started with a 90 somewhere

I guess it is our valve seat diameter.

Regards
Soren

No - he's right, he's talking about a co-axial where gap the piston leave is a cylinder.

You mentioned 90 in your post. I even quoted you!

Michael

Ok, coaxial. Maybe I should read what they write

Hey, that is sure in favor of the coaxial in efficiency.

Soren

dongfang wrote:You have a hangover all right.

What's pi doing in the formula for the area of a rectangle? Your valve passage is really pi times smaller than the barrel cross section.

I'm the one who should be asking how the hell did you get a rectangle of flow into an area that is a cylinder ;p didn't drink *that* much y'know

ARRGGHHH. I hate maths.and i'm only 14. joo makes me miserable..so simple conclusion:

1.the smaller the pilot volume the better
2.light pistons are good
3.equilisation holes are for airtight pistons and should be <5mm

last one not complete... 1/4 or 3/4?

flamerz14 wrote:1.the smaller the pilot volume the better
2.light pistons are good
3.equilisation holes are for airtight pistons and should be <5mm

Equalization holes should actually be just small enough as to have a smaller flow rate than that of your filling valve. (i.e. Schrader)

The 1/4 caliber = ideal piston travel distance is correct, as Jack both stated and proved. (Albeit with his nasty hang-over.)

(Albeit with his nasty hang-over.)

Feeling a lot better now, cheers good to be back home and on my own PC, instead of having to share an internet cafe with drooling perverts browsing porn and death-mutes having animated webcam conversations that look like their trying to defend themselves from a particularly visciois swarm of wasps.

and flamerz, yeah, what Modder said