20 bps Blowback? [And lack of real world testing]

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  • mykroft
    Registered User
    • Jan 2001
    • 2010
    #16
    I'd go with at least an 1800mAH 9.6V RC pack. It ain't gonna be cheap, figure on $50+ for the pack, and $100+ for a good charger(Most RC packs are 8.4 volts, 9.6V packs are usually cheap Tyco AA packs).

    That will give you lots of juice to power the solenoid, and you can just strap it to your tank, oh, and it'll run your Rev too, and a warp if you've got one.
    2k2 VF Cocker, STO/Eclipse Blade, Old-Style 14" Boomstick,
    68AutoMag Classic Feed CF11023, Ring trigger.

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      • nerobro
        Registered User
        • Oct 2001
        • 923
        #17
        Methinks the sub-c cell packs are overkill. Serious overkill. even the 1200mah sub-c nicads can dump over 100 amps. Even the 500-700mah cells in the tyco 9.6v packs will be able to supply the 500ma that the frame seems to want to draw.

        when we were discussing battery packs for the electrococker we were looking at 120-270mah batterys, because they could easily supply the 500ma that our frame would draw during f/a fire.

        During our next test the plan is to use a "tyco" style 9.6v pack, strapped to the n2 tank. The real hope is to get enough of a power pack INSIDE the frame. :-)

        I wonder what the frames behavior would be like without the cap in it... maybe then we'd see it's true amp draw like AGD was pointing out. Course.... even at 20bps the solinoid only has a 12% duty cycle, so charging a cap isn't a bad idea. This compares to the emag.. which pulls for 20ms instead of the 6ms that the frame pulls... Er, I just looked at my notes and it says 40ms...

        40ms * 20 = 800ms.... eeep. 80% duty cycle at 20bps..
        To be an AGD supporter, one cannot be an AGD bigot. -Nero

        Truth is a complex thing. One must govern by simplicity. -M. Mercier, special counsel to his Majesty for domestic matters. The Brotherhood of the Wolf

        "You can't outrun Death forever, but you can make the bastard work for it."

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          • 314159
            Registered User
            • Nov 2001
            • 555
            #18
            on the dragun frame, the pull duration on the solenoid as measured on my storage o scope is 6ms. at 20 balls/sec, the solenoid is operating at a 12% duty cycle.

            the resistance of the coil is 1 ohm. this makes for easy math and almost seems like a beginers electronics because amps = volts/ohms. in this case ohms = 1, so volts = amps, so at 9volts, the solenoid is using 9 amps.

            here is where it starts to differ from the simple text book problem. lets introduce the internal resistance of the battery in the picture. on one of the slightly used batteries, the internal resistance was measured at 9 ohms. the open circuit voltage of the battery was measured at 8.02v. this gives you enough information to draw up an equilivant circuit for the battery. so if you hooked just the solenoid up to this battry, the current would be about .8A (8.02v / 10ohms).

            on the fresh battery, the internal resistance is 6 ohms. 8.35v so if you hooked the solenoid to it, the current would be about 1.2A (8.35v / 7ohms)

            if we were to add the capacitor into the picture. the capacitor is rated at 6800uF. on electrolytic capacitors this is a minimum rating, the actual value of the capacitor is guaranteed over this number and the tollerance is usually +100% for this type of capacitor. so the capacatince should be between 6800uF and 13600 uF. as far as getting an actual number i do not have any equiepment to measure the value of the capacitor directly, i can measure it indirictly by charging it to a known voltage, and measureing the time it takes to disipate it's charge through a known resistance. but i would need to unsolder the cap from the board to do this. this is where i am going to stop because there are many other factors that influence, and no matter how accurate of an aproximation you make, it is still an aproximation.

            if we make a guess saying that the current/voltage of the 9volt supply is inadiquate. you can rephrase the key question to be, how much voltage/amprage do i need to cycle the gun at 20bps. this is a lot easier to answer. i can just hook the dragun to my benchtop power supply, turn the current limiting knob to not limit current, and adjust the voltage to 9 volts. then i gas up the gun, and dial down the current till the marker does not cycle at 20 balls/second and add a little current to this number for a safety margin to spec out a battery. if the marker will not cycle at 20 balls/second at unlimited current at 9 volts, then the question is flawed and has to be rethinked.
            As society and the problems that face it become more and more complex and machines become more and more intelligent, people will let machines make more of their decisions for them, simply because machine-made decisions will bring better results than man-made ones. Eventually a stage may be reached at which the decisions necessary to keep the system running will be so complex that human beings will be incapable of making them intelligently. At that stage the machines will be in effective control. People won't be able to just turn the machines off, because they will be so dependent on them that turning them off would amount to suicide

            sometimes I just freaking hate people. which means the next day I will love them for the sake of balance, but right now I will just concentrate on the hating. Hate hate hate. Blaaaarg! ;)

            turborev - with ai like this, if it controlled any more than a paddle, it would kill you and everyone you care about. ;)

              Comment

              • 314159
                Registered User
                • Nov 2001
                • 555
                #19
                finally got some air last night, and threw the gun on the bench supply, and got it to cycle gassed up at 20bps.

                thoes 9 volts can only kick out so much power
                As society and the problems that face it become more and more complex and machines become more and more intelligent, people will let machines make more of their decisions for them, simply because machine-made decisions will bring better results than man-made ones. Eventually a stage may be reached at which the decisions necessary to keep the system running will be so complex that human beings will be incapable of making them intelligently. At that stage the machines will be in effective control. People won't be able to just turn the machines off, because they will be so dependent on them that turning them off would amount to suicide

                sometimes I just freaking hate people. which means the next day I will love them for the sake of balance, but right now I will just concentrate on the hating. Hate hate hate. Blaaaarg! ;)

                turborev - with ai like this, if it controlled any more than a paddle, it would kill you and everyone you care about. ;)

                  Comment

                  • CTG
                    Registered User
                    • Sep 2001
                    • 37
                    #20
                    6 pack of AAs, biggest 9volt bang for the buck.

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