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Drozd type of bb gun

Built a BB Machine Gun? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: dewey-1 » Sat Jan 05, 2008 11:39 am

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Last edited by dewey-1 on Sun Apr 20, 2008 12:59 pm, edited 1 time in total.
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Unread postAuthor: Antonio » Sat Jan 05, 2008 1:17 pm

SPG wrote:
The perk to a solenoid operated valve like this for us I've always thought is that we could put the solenoid inside the pressure vessel too. One of the things I think we have a lot of difficulty replicating is the tight tolerances need for effective sealing. Put the solenoid inside the chamber and you only have to seal the two wires coming out, which is a lot easier.

Now can anyone build a circuit board to replicate the drozd's?


Nice comment there> putting the valve in the pressurevessel. I have tried to replicate the seals and stuff but it doesnt work that well; seals of with too much friction or too little sealing and perfect friction''.
About the circuit boarding> I dont have a clue but I dont think it would be that difficult. First we will try a simple semiauto solenoid, operated by the finger and no complex electronics.
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Unread postAuthor: Antonio » Sat Jan 05, 2008 1:36 pm

dewey-1 wrote:
I could do the PCB layout if some has a functioning board assembly they could let me borrow for awhile.
Just need to know how many would be interested in this PCB?



Sounds very cool man! Its just that I dont have a very well working valve now. It needs way too much force to open it bc the orings are too tight. This also gives the valve a very ineffecient dwell time.
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Unread postAuthor: SPG » Sat Jan 05, 2008 2:26 pm

I can see how you could do burst fire without needing a circuit board easily enough, just by having a long pull trigger switch which operated three contacts one after the other.

Now how about a very simple repeater circuit? Just On-Off-On-Off with a set delay between them?
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Unread postAuthor: Isomer » Sun Jan 06, 2008 12:51 am

wow, i know im a bit late on this but i actually have one lol
it's in my closet with the rest of the arsenal
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 06, 2008 1:39 am

SPG wrote:Now how about a very simple repeater circuit? Just On-Off-On-Off with a set delay between them?


In my early spudding days I had come up with this design that wouldn't really need any fancy circuitry, you could even link up another cam on the same rotor to a rod that would slide a breech sleeve backwards and forwards out of phase with valve opening in order to reload ammunition
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Unread postAuthor: Antonio » Sun Jan 06, 2008 9:30 am

jackssmirkingrevenge wrote:
In my early spudding days I had come up with this design that wouldn't really need any fancy circuitry, you could even link up another cam on the same rotor to a rod that would slide a breech sleeve backwards and forwards out of phase with valve opening in order to reload ammunition


Yeah very sweet. The problem is that when u stop the motor right whent the cam is next to the stem then it may not have enough momentum/power to make it open. If it does open if will open less and give u very unconsistent fire.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 06, 2008 9:39 am

ant wrote:
jackssmirkingrevenge wrote:The problem is that when u stop the motor right whent the cam is next to the stem then it may not have enough momentum/power to make it open. If it does open if will open less and give u very unconsistent fire.


True but if you're firing full auto this will only affect the first shot so not really a problem ;)
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Unread postAuthor: SPG » Sun Jan 06, 2008 11:10 am

Hmm, just realised I could do semi/fully auto switching unit but fully auto would be more

Fire........................ Fire........................ Fire........................ Fire........................ Fire........................ Fire........................

than

Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire... Fire...

How? An old intermittent windscreen wiper switch.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 06, 2008 1:04 pm

SPG wrote:How? An old intermittent windscreen wiper switch.


That's what galfisk had suggested for a similar mechanism back on spudtech here
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Unread postAuthor: SPG » Sun Jan 06, 2008 1:09 pm

Ahh, there's nothing new under the sun is there.... if only your memory was as bad as mine, I could look quite intelligent.

Although he's actually referring to something slightly different which is the switched cam you'll find in a wipermotor gearbox. I was referring to the control which is either in the stalk on your steering column, or somewhere in between. You know the one which turns your wipers on once a second or so.

Hmm, now I think that's variable on my car from 3 times a second to once every 3 seconds.

*Alex goes and pillages his dashboard*
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Unread postAuthor: Skywalker » Sun Jan 06, 2008 1:54 pm

Come on, no need to ruin your car! What about flashing lights of some kind, like a strobe light or Christmas tree lights? There are bound to be some existing circuits that produce low frequency square waves. And while I'm not particularly tallented, circuit design shouldn't be that difficult if you wanted to wire it up yourself!
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Unread postAuthor: bluerussetboy » Sun Jan 06, 2008 2:46 pm

how about using a 555 timer chip? burnt latke used one for a fan controller and was even nice enough to link to a page with a timing calculator.

http://home.cogeco.ca/~rpaisley4/LM555.html#1
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Unread postAuthor: SPG » Mon Jan 07, 2008 7:26 am

Well I wasn't actually going to ruin the car, I was going to ruin an old car in a scrap yard.

Then I remembered the direction indicator circuit on my old 2CV which actually included a small 12v solenoid inside the switch housing itself to make a tic-tic noise.

Excellent.
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Unread postAuthor: Panzerfaust » Sat Jan 12, 2008 11:16 pm

Drozd's rule, heres mine
(picture left over from what i got for christmass)
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