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81mm Mortar Halftrack project

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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81mm Mortar Halftrack project

Unread postAuthor: Tranham » Sat Apr 20, 2013 10:05 am

Wanted to post progress on my halftrack mortar. Got it shooting yesterday with a ASCO valve. Baseballs fir perfect, plus I have a 1 1/2 sub-caliber barrel and will be making a 2" one soon. Sorry, no shots of the actual plumbing yet. The air is run through the ball of the mortar cup. The main reason is to hide all the pneumatic stuff. Its being used for reenacting mostly.

This is what my halftrack will hopefully look like someday

http://olive-drab.com/idphoto/id_photos ... ftrack.php

Short video of test fire


Would be good to get a look at the valve and things, seems like the valve isn't working optimally although it might just be because you're using low pressure or something else.

Cannon looks great though



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Last edited by jrrdw on Sun Oct 20, 2013 7:27 am, edited 1 time in total.
Reason: Fixed video.

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Unread postAuthor: POLAND_SPUD » Sat Apr 20, 2013 1:28 pm

awesome work

ohh and BTW... the video link is messed up
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Unread postAuthor: MrCrowley » Sat Apr 20, 2013 5:05 pm

[youtube]http://www.youtube.com/watch?v=vG9Lz0-HI88[/youtube]

Would be good to get a look at the valve and things, seems like the valve isn't working optimally although it might just be because you're using low pressure or something else.

Cannon looks great though, especially on that halftrack :D
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Unread postAuthor: Tranham » Sat Apr 20, 2013 7:45 pm

Thanks for posting that. The test fire was at 50psi with a baseball then a tennis ball. I've noticed the discharge to be inconsistent. Too little trigger pull and it won't release enough air. Too much and it dumps the air twice. Just right and it drops the pressure in half and refills quicker. Any ideas on how to get a perfect trigger pull every time except just practice?

Right now it runs off my compresser at home or a 3ft tall nitrogen bottle under the floor (pics coming soon). Could not use CO2 because the placement of the cylinder is horizontal. I am looking into adding a 12v compressor to use for backup. Don't like the noise of the compressor but it should be covered by the engine when it's running.

Today I played with tennis balls all day. Impressive even though they are a loose fit. Lost a bunch of them and my only baseball. Need more ASAP! I want to work out a range card based on angle and psi. Also played with shooting tshirts. When I go to air shows and parades I can give them out in style.

Robert
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Unread postAuthor: MrCrowley » Sat Apr 20, 2013 7:52 pm

Too little trigger pull and it won't release enough air. Too much and it dumps the air twice. Just right and it drops the pressure in half and refills quicker. Any ideas on how to get a perfect trigger pull every time except just practice?
I can't say much until I know what valve you're working with, maybe someone else around here has a better idea based on your description. I can't really think of why it would dump the air twice, that's not a symptom I've come across before but I can think of a few ways that it might be possible given the right circumstances. So yeah if you have the model number of the valve handy and can describe how it is filled and triggered (ball valve, blow gun, 3-way valve, solenoid, etc) we might be able to get to the bottom of the problem otherwise we'll just wait for the photos.

though they are a loose fit

I'd recommend looking around for some plastic cups or something that you could use as a sabot. Performance should be better and more reliable and the cups might be reusable after each shot. If you can't find any cups or similar items, thin pieces of cloth or large plastic bags could do the trick.
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Unread postAuthor: Tranham » Sat Apr 20, 2013 10:27 pm

Ok, specs:

+/- 8 feet of two inch metal pipe for air chamber.

Barrel is 46" in different diameters depending on which subcaliber using or none. There is an additional 1 1/2 Ft rubber hose from ASCO valve that is part of the barrel. The flow of air is choked at 1 1/4" at the mortar cup ball.

Controls are hidden in tool box, lid not attached yet.

Valve is a ASCO 8353H38

May be hard to make out the plumbing because its hugging the floor from the bottom.

Robert
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 21, 2013 1:29 am

Colour me impressed, nice to see some heavy metal :D
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Unread postAuthor: Crna Legija » Sun Apr 21, 2013 4:13 am

you might be piloting it slowly with the long hose try with a shorter and thinner hose. If you pilot it slow diaphragm valves tend to honk or open close rapidly
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Unread postAuthor: biged » Fri Apr 26, 2013 6:38 pm

Tranham wrote:Today I played with tennis balls all day. Impressive even though they are a loose fit. Lost a bunch of them and my only baseball. Need more ASAP! I want to work out a range card based on angle and psi.


Robert, Check you local tennis courts, and YMCA. The trash cans are filled with old tennis balls. Also contact a tennis club, they will have access to a lot of balls.

More tricks with tennis balls at reenactments:

Dunk them in water just before firing. Increases weight and you can squeeze out another 20+ feet.
Load/drop several into the barrel to bombard targets.
For night events: Cut open a bunch of glow sticks in a bucket. Dunk the tennis balls in it for night effects. (Wear eye protection from the mist/spray - it is non toxic.)
(You can also just launch glow sticks, like 10-40 at a time. Trust me, it is wild to watch. It's like having reusable fireworks.)
Tennis ball Bounty: Make an announcement, whoever brings back the most amount of tennis balls gets $10 or $20. I went through 3-4 trash bags in a year before...

I have taken an 1.5 ASCO valve to 225 psi before. ;)

My 81mm cart mortar.
http://i70.photobucket.com/albums/i110/ ... Vu-L-1.jpg
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