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Why I believe coaxials are opposite of what is best fps etc.

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Ragnarok » Sun Apr 11, 2010 12:15 pm

Technician1002 wrote:Projectile position every foot of travel was captured on a graph.

Well, that must have been an interesting graph:

After 1 ft of travel, its position is 1 ft from where it started.
After 2 ft of travel, its position is 2 ft from where it started.
After 3 ft of travel, its position is 3 ft from where it started.
After 4 ft of travel, its position is 4 ft from where it started.
After 5 ft of travel, its position is 5 ft from where it started.


Hmm, I think this might be a linear relationship. :roll:
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Unread postAuthor: Technician1002 » Sun Apr 11, 2010 12:34 pm

Ragnarok wrote:
Technician1002 wrote:Projectile position every foot of travel was captured on a graph.

Well, that must have been an interesting graph:

Hmm, I think this might be a linear relationship. :roll:


:lol: It is more interesting with the time of each foot recoded. The time to travel the last foot didn't take long at all.

We measured projectile position vs time on launch.
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Unread postAuthor: POLAND_SPUD » Sun Apr 11, 2010 12:57 pm

Not all coaxial designs have the valve at the breech of the cannon chamber
yeah I know, QDV cannons might work great for you but they are not as simple to build as QEV cannons... also not everyone likes the way QDV guns look
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Unread postAuthor: boyntonstu » Sun Apr 11, 2010 1:30 pm

c11man wrote:how to make a light coax piston? simple, make a piston shaped like a cup. it can be made quite short like half the diameter of the piston long. attach the sealing face to the inside of the cup and this also reduces pilot volume to very minumal.

a piston weighing 198gr seems quite light seing at it is 13 grams witch to me means 13 paperclips and that is quite unbelievable.

also can you put your weights in a grams or oz as it is easyier for most people to visualize.


All my weighing is done in grains as most bullets are measured.

A typical .38 weighs 158 grains, etc.

My piston is a 3/4" diameter Oak (not the lightest wood I could have used) dowel that is drilled out from the rear to lighten it into a long thin cup shape. 2 O rings. a rubber washer, a short 6-32 screw and a nut.

I had no idea that it was light in comparison to other pistons.


BTW In speaking about coax vs piston, we may find it useful to divide the discussion to metal vs plastic.

Or 1" and under and 1" and over.
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Unread postAuthor: c11man » Sun Apr 11, 2010 1:36 pm

coax vs piston? most coax are piston valves so i dont understand.

All my weighing is done in grains as most bullets are measured.

and thes is a piston not a bullet so why weigh it in a unit that very few use?
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Unread postAuthor: boyntonstu » Sun Apr 11, 2010 1:43 pm

c11man wrote:coax vs piston? most coax are piston valves so i dont understand.

All my weighing is done in grains as most bullets are measured.

and thes is a piston not a bullet so why weigh it in a unit that very few use?


This will solve your weight problem.

http://www.onlineconversion.com/weight_common.htm

Use grains and you too will be among the chosen few.


:roll:
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Unread postAuthor: c11man » Sun Apr 11, 2010 1:49 pm

why would i even want to use grains?
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Unread postAuthor: boyntonstu » Sun Apr 11, 2010 1:55 pm

c11man wrote:why would i even want to use grains?


Why would I choose to use lowercase i for I.

Would you call that an i for an I?
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Unread postAuthor: c11man » Sun Apr 11, 2010 2:04 pm

this thread has gone from a useless topic posted by a stuborn old idiot to a complete waste of time...

and i use i instead of I because i amd a lazy teenageer
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Last edited by c11man on Sun Apr 11, 2010 7:01 pm, edited 1 time in total.
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Unread postAuthor: POLAND_SPUD » Sun Apr 11, 2010 3:04 pm

grains are useless... they are not 'better' than grams in any way... so what's the point ?

some people were born in countries that still use imperial units and they are at a disadvantage... so what's the point of introducing grains here if almost everyone has already learned how to use grams?
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Unread postAuthor: Ragnarok » Sun Apr 11, 2010 5:26 pm

POLAND_SPUD wrote:some people were born in countries that still use imperial units and they are at a disadvantage... so what's the point of introducing grains here

I'd point out that grains are an Imperial unit. 7000 grains to the pound.

~~~~~

But seriously, Stu. This is what is called "unacceptable transfer of effort".
If you do the conversion and post it, it means that it's only done once, not by every person who isn't fluent with the unit.

I do all of my pressure calculations in Pascals. But I convert the numbers back, because most people here would either have to stop and think about 3500000 Pa actually means, or look it up on a table. (35 bar, 507.5 psi if you're interested.)
A lot the time, I post basic conversions for any units I've posted.

Coincidentally, I'm building a launcher which will produce 740,750,670 hp ns and 0.000000000000000000000000000000000000000000000000000000000410762107966307 pc t<sub>p</sub><sup>-1</sup> when fired with a projectile massing 4.5 μhhg of Hg.

... What, you're not familiar with horsepower-nanoseconds, parsecs per planck time and micro-Hogsheads of mercury (Proper Imperial hogsheads of course, no American customary units here)? Well, you'd better find a conversion table then.
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Unread postAuthor: POLAND_SPUD » Sun Apr 11, 2010 5:59 pm

I'd point out that grains are an Imperial unit. 7000 grains to the pound
yeah I know... that's the point... you must have misunderstood my post...

I didn't have to switch to metrics as I was born in a country that uses them...
but I guess that getting used to them can be a real PITA for those who were born in countries that still use imperial units

so what's the point in introducing grains if most ppl already know how much 1 gram is ?
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Unread postAuthor: boyntonstu » Sun Apr 11, 2010 7:29 pm

POLAND_SPUD wrote:
I'd point out that grains are an Imperial unit. 7000 grains to the pound
yeah I know... that's the point... you must have misunderstood my post...

I didn't have to switch to metrics as I was born in a country that uses them...
but I guess that getting used to them can be a real PITA for those who were born in countries that still use imperial units

so what's the point in introducing grains if most ppl already know how much 1 gram is ?


I have seen projectiles in ounces, grains, and grams.

What is the weight of a .22 bullet?


About 29 grains

Exactly 0.066 285 714 286 ounce

How does that suit you?


Have you ever seen it this way?


How about 1.879 168 39 gram?


IMHO When things less than a pound move, the best comparative weight system is grains. because it is always a whole number with no decimals.
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Unread postAuthor: c11man » Sun Apr 11, 2010 7:35 pm

IMHO When things move, the best comparative weight system is grains.

i move so should you weigh me in grains? IMHO i think your the only one who feels this way.

and with all those decimal points your just being childish. one or two would do just fine for any sane person
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Unread postAuthor: boyntonstu » Sun Apr 11, 2010 7:38 pm

c11man wrote:
IMHO When things move, the best comparative weight system is grains.

i move so should you weigh me in grains? IMHO i think your the only one who feels this way.

and with all those decimal points your just being childish. one or two would do just fine for any sane person


Are you a thing ?

Perhaps so with an i for an I.
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