At this point I would give the coil a bit of a test to see if you are happy with itís performance. If you are not sure how to connect the coil to the circuit please refer to the CoilOsapien circuit further down the page, make sure you remove the enamel coating on the ends of your coil or it wont conduct. The performance will also depend heavily on the starting position of the projectile, I am using 5mm ball bearings with this coil and have positioned them roughly 3-5mm from the back of the coil (sorry for being vague but I didnít think to measure this before I glued it all together). I used the back stop of the pen to hold the BBs in place and slowly shortened the end of the pen until the best starting position was found. Once you are happy with how your coil is firing it is time to start thinking about adding in the auto reload, laser sight and housing.
For the reload I used two small plastic lids, a small servo, another pen and a cog from a track and wheel set I had spare. I took the cog and glued it to the round servo attachment and then ground a notch out of them big enough to accommodate one BB. I then used the two lids to create a small housing for the disc I created with one hole drilled in the top and one in the bottom (on opposite sides) the same size as the BB and one on the top centre of the housing to allow the servo to drive the disc. The hole on the top had the pen glued over it to create a ammo clip and the hole on the underside was lined up over a hole drilled in the chamber infront of the coil to allow the collected BB to drop into the firing chamber and roll to the back. I used the screw in pen top and the small spring from the pen to make the clip spring loaded (a bigger spring would better).
Check out a larger version of the reload diagram for a visual depiction of the reload. NOTE: The diagram is not to scale. Make sure that the housing is only high enough to fit one BB otherwise it will collect two and/or will jam.
Hole in underside of housing
Housing with servo and clip attached
Now you will need to add in a couple of contacts for the BB to bridge to turn of the auto reload servo. The picture to the right shows the small pieces of copper I salvaged from the disposable camera put to use. Drilling out the end cap I then put the two contacts through to the other side and hot glued them in position. When the BB makes contact with these terminals it turns off the servo and activates the loaded indicator LED. (Refer to CoilOsapien circuit diagram for wiring details). Patience is needed here to ensure that the contacts are in the correct position, otherwise the servo will keep pumping ammo into an already loaded chamber.
Coil, chamber, clip, servo and housing
Once the contacts are sorted pop the end cap into the back of the chamber and glue a small magnet to the back of the end cap to keep the ball bearing in place before firing. Make sure the magnet is strong enough to hold it there but not too strong to affect the firing of the coilgun. I used a magnet from the foot of a ďtech deckĒ toy I had lying around it is small and strong enough for the job. (Note: you may need to lengthen or shorten the end cap to make sure the magnet is in a good position).
Wire up your servo LED and 5v regulator, then glue them to the servo (I placed these on the coilgun but they could have been placed elsewhere).
Using two old film canisters I made a little housing for the coilgun parts. Drill the center of one of the canisters lids to fit the back of the chamber through and the bottom of a canister to poke out the muzzle and laser sight. Cut the bottom out off the other canister and use this as the back section (to take the lid). Cut enough away from the canisters to allow all the parts to poke out of the top and glue both front and back sections canisters together to make the housing. Glue this down to the hand of the V2 in the desired position. I then used some ribbed tubing to hide the wires running from the body to the hand.
Making sure everything is wired up correctly give it a test and see how she fires, if it works it is time to calibrate that annoying laser! I glued the laser onto the bottom of the barrel and lined it up as best I could, needless to say itís aim needed some work. Keep firing and making small adjustments to the placement of the laser until the BBs hit your desired target. this might take a while but it is worth it! The gun I have been told will produce about half a Joule of Kinetic energy. Thanks to Berni for working out the math for me on that one.
When the servo is activated it turns the disc inside the housing, with each spin it will pick up one BB and drop it into the firing chamber. The coilgun will need to be on a slight angle whilst reloading to allow the BB to roll to the back of the chamber. The reload would function better if it could be setup behind the coil to drop the BB directly into position, this would also allow loading in any position. Due to the fact there was not enough room to mount it back there I went the easier less functional alternative.
- All 9v sources were taken from the main motor batteries of the V2.
- SW1 & SW2 are part of my remote relay board.
- RLY1 was used to prevent damage to the relay on the board due to the high voltage it would be switching. If you were to use manual switching RLY1 could be omitted.
- Resistor values will depend on the laser and LED used.
Thatís All... Begin the MAYHEM!!!
Now take your V2 and randomly fire at various objects around your home...
Preferably nothing glass, antique or alive!!!