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Short question topic

A place to ask general spud cannon related questions.
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Re: Short question topic

Unread postAuthor: hectmarr » Sat Sep 07, 2019 2:38 pm

Does anyone know how much pressure I can use in this mapp gas can?
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Re: Short question topic

Unread postAuthor: mrfoo » Sun Sep 08, 2019 5:06 am

IIRC, it's marked on the cans. Not very much, as I recall, somewhere around 22 bar, I was looking at one I have lying about the other day. I'll have a look in a bit.
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Re: Short question topic

Unread postAuthor: hectmarr » Sun Sep 08, 2019 9:09 am

The one they gave me has no label or inscription of any kind. I've searched the web, but the data is elusive. They only talk about the characteristics of gas for welding :roll:
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Re: Short question topic

Unread postAuthor: mrfoo » Sun Sep 08, 2019 11:22 am

OK, just had a look. The cans themselves aren't stamped. Label states 22 bar for the contents, so you're almost certainly safe up to there. That's for the old-style MAPP canisters with methylacetylene-propadeine rather than the less energetic propylene-propane mix they use these days.

Those cans do come with a handy fill valve that you're obviously not supposed to use.
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Re: Short question topic

Unread postAuthor: hectmarr » Sun Sep 08, 2019 12:09 pm

OK understood. I'm just going to inflate to 200 psi, no more, it has to endure well. Thanks for your reply.
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Re: Short question topic

Unread postAuthor: jackssmirkingrevenge » Tue Sep 10, 2019 7:23 am

hectmarr wrote:OK understood. I'm just going to inflate to 200 psi, no more, it has to endure well. Thanks for your reply.


MAPP gas has a vapor pressure of around 200 psi at 30 degrees celcius so you should be more than fine at this pressure.

PDF report of these bottles being abused in the name of health and safety

If I understood correctly, working pressure for the MAPP bottle is listed as 13 bar or 189 psi.
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Re: Short question topic

Unread postAuthor: hectmarr » Tue Sep 10, 2019 9:12 am

Good report Thanks Jack.
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Re: Short question topic

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Re: Short question topic

Unread postAuthor: hectmarr » Fri Sep 27, 2019 10:33 am

Does anyone have information on how to aim with a sight of the reflex type, or red dot? I mean how the firing cannon is aligned towards the target.
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Re: Short question topic

Unread postAuthor: jrrdw » Fri Sep 27, 2019 3:02 pm

hectmarr wrote:Does anyone have information on how to aim with a sight of the reflex type, or red dot? I mean how the firing cannon is aligned towards the target.


Are you asking how to sight it in?
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Re: Short question topic

Unread postAuthor: farcticox1 » Fri Sep 27, 2019 4:38 pm

Like this I guess, I have 2 but haven't used them yet.

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Re: Short question topic

Unread postAuthor: hectmarr » Fri Sep 27, 2019 8:40 pm

jrrdw wrote:
hectmarr wrote:Does anyone have information on how to aim with a sight of the reflex type, or red dot? I mean how the firing cannon is aligned towards the target.


Are you asking how to sight it in?

What I do not understand, is how it is possible to align the firing cannon, with a single point ... To draw a line you need at least two points, as in open sights with a rise and point. :roll: These sights only show one point (red or green or the color they have).
farcticox1 wrote:Like this I guess, I have 2 but haven't used them yet.


They offer me one of medium quality at a low price, and that is why I like to know how the hell you can aim with that. I'm with the video, I hope to understand. Thanks guys
 
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Re: Short question topic

Unread postAuthor: jrrdw » Sat Sep 28, 2019 5:33 am

Name of that video should be "How To Sight Your Gun In" Clear cut method, 1clk:1" @ 100yrds.
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Re: Short question topic

Unread postAuthor: farcticox1 » Sat Sep 28, 2019 6:42 am

I'm thinking the red dot is actually a beam of light, 1st fixed point is where it hits the reflector and the 2nd is where it hits you're eye, like a reverse laser pointer but not strong enough to blind you.

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Re: Short question topic

Unread postAuthor: hectmarr » Sat Sep 28, 2019 8:09 am

farcticox1 wrote:I'm thinking the red dot is actually a beam of light, 1st fixed point is where it hits the reflector and the 2nd is where it hits you're eye, like a reverse laser pointer but not strong enough to blind you.

download.jpg

For this reason the name of the reflex system is clear.
I'm going to buy it, to know exactly what this type of aiming machine is about, and try it. It is for a co2 gun, to aim quickly at short distances up to 10 or 12 meters.
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Re: Short question topic

Unread postAuthor: mrfoo » Sat Sep 28, 2019 9:51 am

If you're playing at 12 meters, 1 arc minute (one click) is equivalent to 3.5mm.

Comes from trigonometry. SOH CAH TOA ,if you remember your schoolin'. For a right angled triangle, the tangent of one of the non-right angles is equal to the length of the side opposite that angle divided by the adjacent side. One arc-minute is equal to 1/60 degree (and an arc-second is equal to 1/60 arc-minute).

tan (1 / 60) = offset / distance to target

thus

offset = distance to target * tan (1/60)

Obviously, you need to choose units to fit the likely offset, which will mean upscaling your distance to target - 12m = 12000mm.
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