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high tech air cannon in progress

A place to ask general spud cannon related questions.
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Unread postAuthor: Technician1002 » Fri Nov 13, 2009 11:29 pm

The piston on the QDV can either be pulled open with a rope, rod, or blasted open by air pressure from the barrel. The video is this one. The piston rides on a rod, but is not directly connected to it.

http://www.youtube.com/watch?v=No3nI07mlQo
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Unread postAuthor: MrDEB » Sat Nov 14, 2009 9:37 am

QUESTION?
which valve is desired for power and which one for accuracy (consistent firings)
The QDV vers the barrel sealing valve
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Unread postAuthor: inonickname » Sat Nov 14, 2009 9:49 am

The QDV if constructed well in general will have more flow and a faster opening time. Depending on the piloting method used, both can allow very consistent shots.
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Unread postAuthor: MrDEB » Sun Nov 15, 2009 7:17 am

planning on building with a seperate air chamber as I posted drawing(see above) using a QDV actuacted by a spk valve triggered piston (back to back air cannons)
using this method will hopfully add to consienty and less operator error (jarring the barrell while pulling rod or rope) as well as opening the QDV at same speed.
Using two separate air chambers will prevent loss of projectiles propellant air being used for triggering.
received the transducer yesterday, planning on testing the transducer next week. Parts for chronograph and wind sensors have been ordered as well as the LCD modules. cannon project going on hold until I get my Christmas lights up. All 15,000 lights.
All computer operated to music.
Twisted Sister, Crazy Frog etc.
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Unread postAuthor: spudtyrrant » Sun Nov 15, 2009 8:55 am

MrDEB wrote:planning on building with a seperate air chamber as I posted drawing(see above) using a QDV actuacted by a spk valve triggered piston (back to back air cannons)
using this method will hopfully add to consienty and less operator error (jarring the barrell while pulling rod or rope) as well as opening the QDV at same speed.
your better off to just build a good solid stand with an adjustable elevation level, considering your requirements aren't very demanding, i am able to easily land round within 5-10 feet of each other @ 100+ yards, and that's with a hand-held cannon
I'm sure one with adjustable elevation and a secure stand would be even more effective
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Unread postAuthor: Technician1002 » Sun Nov 15, 2009 10:19 am

spudtyrrant wrote:your better off to just build a good solid stand with an adjustable elevation level, considering your requirements aren't very demanding, i am able to easily land round within 5-10 feet of each other @ 100+ yards, and that's with a hand-held cannon
I'm sure one with adjustable elevation and a secure stand would be even more effective


You are a much better shot than I am. But then again I shoot from the hip. At 100 yards, I'm lucky to get them within 10 yards. :( A stand is highly recommended for accuracy.
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Unread postAuthor: MrDEB » Sun Nov 15, 2009 1:38 pm

yes a stand with elevation and mounted on an adjustable and lockable truant.
aim at target, adjust for wind, adjust air pressure using digital readout, then corrlating for muzzle velocity and BAM! hit on the target every time.
Or at least hope to.
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Unread postAuthor: MrDEB » Sun Nov 15, 2009 2:03 pm

my latest additions
plan to use a small propane canister (used from camping) for trigger air tank. thinking why take away air from the main chambers for triggering. may not be consistent.
have an isolation ball valve so I can fill both chambers up but at say 10psi, close ball valve and continue filling main chambers.
transducer mounted to monitor main air chambers but with ball valve open I would be able to read pressure in both tanks. close ball vale upon reaching desired pressure for trigger.
going tomorrow to scrounge up some old propane tanks (5gal or 10gal) for main air chambers. cheaper that pvc pipe.
weld some 2 inch nipples then attach to QDV.
trigger tank to be hard plumbed as well. Have a needle valve to make minute adjustments to pressure as well as a safety valve to limit air chamber pressure to 100psi max.
QUESTION, should the propane tanks be full before welding on nipples --LOLImage[/img]
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Unread postAuthor: MrDEB » Sun Nov 15, 2009 4:48 pm

latest electronics schematic
need to tweek and write code.
test each segment seperatly -air pressure, wind speed, wind direction then muzzle velocity.
THEN combine the codes into one.Image
and yes if anyone is wanting to assist or when I get it done and you want to build same for code and/or printed circuit board and programed PIC chip.
but that may be several months down the road.[/img]
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Unread postAuthor: POLAND_SPUD » Sun Nov 15, 2009 8:29 pm

sorry for mentioning it again but IMO you could build this gun from off the shelf parts

you could use 1/2" QEV (but 3/4" would be better) as the main valve

to get good consistency you could buy a solenoid spool/poppet valve off ebay for under 20$... but probably even a sprinkler valve would work just fine

ohh and I suppose that ~50 - 100 cm X 3/4" iron pipe would be enough


once you have all the parts and a couple of most common fittings you can build the gun in under 0.5 hour


I know you might think this is taking the easier rout... but hey is there anything wrong about it ?? if you can build it faster, easier and cheaper using off the shelf parts there is no point to complicate the design more than it's needed...

I am not saying you can't add electronics I am referring only to the gun itself... For me engineering is all about getting the best performance with as simple and cheap design you can find

that's just my 0.2$
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Unread postAuthor: Technician1002 » Sun Nov 15, 2009 8:41 pm

QUESTION, should the propane tanks be full before welding on nipples --LOL


They should be full of non combustible material. In my case I run an airline into it so it constantly gets an air purge to prevent the buildup of a combustible mixture. In my QDV's, I cut both ends of the tank for free air flow, preheat the area to be welded to drive off any oils and paint that can make an explosive mixture, then assemble with a copper air purge tube running, and then weld. Safety is no laughing matter, unless it happens to someone else. :D

In regards to your schematic, the weathervane input needs work. Use a couple more darlington pairs. There will need to be a Home flag so the North can be set every time and a second pickup on the optical encoder 90 degrees out of phase will provide up and down counts as the vane turns back and forth in the wind. Look up Sine/Cosine shaft encoders for more information.

To save pincount, a updown counter can be added to the 3 pickups so the count is reset as the home pulse is passed and the counter can then provide up/down counts to the pic from the home position in either direction. Callibration and startup only requires the vane to make one 360 rotation to start sending up/down counts to the PIC. The pic would then track position from the home position. This reduces the pincount to 2.
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Unread postAuthor: MrDEB » Sun Nov 15, 2009 11:50 pm

was concerned about North but thinking about it all I need is a reference position or HOME position to start for the direction setting.
have a 8-10f pole with weather stuff on top. lock the wind vane. then have aiming tube or sight , point at target from behind cannon with barrell pointed at targe as well.. lock the pole in this oreintation. unlock the vane then note which way the vane is pointing in relation to cannon position. the wind direction sensor will count how many degrees the vane has moved from HOME position. Think of a ps2 mouse wheel encoder, the old ball type mouse. only has two optic sensors per wheel..
wind sensor, just count/time rpm (drive car with unit out window. go say 20 mph then note reading. go 30 mph and note reading. then one can caculate rpm=mph of wind speed. sure simple math would work but maybe not as accurate?.
why use an up down counter when you have a PIC that will count up down for you? unless I am missng something.
as for cannon size? a 1 1/2inch QDV (shooting baseballs) with 2inch piping from old propane tanks.
thanks for ideas about airing out the tanks.. Plan was to remove the valve from top of tanks then inject air to purge any flammable gas from tank. Even fill with water to overflow then drain and air out. let dry a week outdoors with valve removed after airing out.
welding of tanks is a major concern but feel that removing the valve and purging as described should remove any gas from tank. I like your air purge idea but only welding one end of tanks with 2 inch nipples.
Has anybody used muffler pipe instead of galvanized pipe?
sounds like technician 1002 knows something about electronics?
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Unread postAuthor: Technician1002 » Mon Nov 16, 2009 12:40 am

MrDEB wrote:why use an up down counter when you have a PIC that will count up down for you? unless I am missng something.


Yes, which way did it turn? You know how far in counts, but which way did it go? If it swings back a forth a few times, you get counts for another 90 degrees or so, but the PIC with a single pickup doesn't know the vane stopped and reversed direction a few times. You will need the second cosine pickup to acquire directional info. The schematic is missing the cosine pickup. 1 will be needed. For reliability in varying lighting conditions, consider using the stripped magnetic pattern on the back of refrigerator magnet business cards and a couple of hall sensors. They are unaffected by ambient light.

A locked start up position will solve the home position issue instead of a flag.


thanks for ideas about airing out the tanks.. Plan was to remove the valve from top of tanks then inject air to purge any flammable gas from tank. Even fill with water to overflow then drain and air out. let dry a week outdoors with valve removed after airing out.
welding of tanks is a major concern but feel that removing the valve and purging as described should remove any gas from tank. I like your air purge idea but only welding one end of tanks with 2 inch nipples.


You are welcome. Propane is heavier than air. Invert the tanks to let the heavy gas spill out. The tanks are unpainted inside so water will start rust. Painting after welding is recommended to reduce rust. The tanks may have oil residues inside. After purging welding may release combustible gass. Plan on purging during any welding to prevent build up of an explosive atmosphere. Another option is to drop in a few pounds of dry ice to purge out any Oxygen during welding.
sounds like technician 1002 knows something about electronics?
ISCET certified journeyman technician. :D Guilty as charged.
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Unread postAuthor: POLAND_SPUD » Mon Nov 16, 2009 9:05 am

sounds like technician 1002 knows something about electronics?

let say that he must have got an orgasm when he saw your electronics schematic :D
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Unread postAuthor: MrDEB » Mon Nov 16, 2009 10:30 am

The schematic I posted does need a second sensor for the wind direction. Thinking about a ps2 mouse method of direction sensing.
I like the dry ice idea.
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