My group has been working on developing a small scale electromagnetic-accelerator, or mass driver. We have built several different setups for our mass driver, in attempt to shoot a piece of metal out of our rig.
Early on in the class we didn't have any knowledge about mass drivers or electricity and ended up blowing a capacitor, which was kind of scary. After blowing up a capacitor we decided that the best course of action would be to start learning about what a mass driver really was, and what really powered it. After investigating capacitors we realized that the capacitor exploded, because we had connect the positive terminal of the capacitor to the negative terminal of the DC power supply. Upon further research we discovered how to safely charge capacitors based on the voltage rating, power supply (AC or DC), and how to connect multiple capacitors together in order to increase the voltage rating or the total capacity depending on whether they are connected in series or in parallel. When connected in parallel the total capacity of the capacitor bank is the sum of all them, but the voltage stays the same. when connected in series lose capacity but gain a higher voltage rating. We are realizing now that one of the important things we are lacking in order to charge the capacitors with a high voltage is a transformer.
Rail gun Setups: Right after we had enough information about how to not blow up on capacitors we started to build very small scale rigs. Our first rig was very basic just aluminum foil on two wood blocks with the capacitor leads hooked up to either side of it, but we unsuccessful in make the projectile accelerate. The next one we built was only slightly better than the first, instead of using aluminum foil we glued two metal strips from the tv we took apart earlier. This turned out better than the first but the problem was the BBs we were using kept getting welded to the rails, which is the opposite of what we wanted. At this point we figured that it was our rails that were the problem, and thought that the projectile wasn’t making contact with the rails the entire time the capacitor was discharging. In order to try and correct this three more rigs were made one out of nails, one out of bobby pins, and the most recent one out of a model train set which contained brass rails. When none of those worked either Mr. Byars, our teacher, mentioned that it might because of the fact that our projectile was magnetic, which was a problem since we had read earlier that the projectile must be conductive, but not magnetic, metals such as copper and aluminum have these properties. Mr. Byars also mentioned that we could create our own projectiles by creating a mold of the BBs we already have, then pouring molten aluminum into the mold to make a pure aluminum BB that would wouldn’t get stuck to the rails whenever we tried to run tests.
Step 1: Aluminum Foundry
1) Get supplies
- Plaster of Paris
- Warm water
- One large steel bucket
- One smaller plastic that can fit inside the big steel bucket bucket
- U-bolt (optional)
- 1 foot steel pipe
- Blow Dryer
- fire extinguisher
2) Mix Plaster
Mix Plaster of paris, sand and water at a 7:7:5 ratioand stir together until all the chunks are gone. Pour plaster mixture into steel bucket, and then put the small plastic bucket in the middle and push it down. If you want you can make a lid by using another bucket and filling it only partially with plaster and placing u-bolts in it for grip. Let the plaster dry for about an hour.
3) Drill hole
After the plaster dries use a 1-inch drill bit and power drill to drill a hole in the bucket at a 30 degree angle. and insert the 1 foot steel pipe.
3) Make crucible
Cut a small fire extinguisher with a hacksaw to fit the size of your foundry.
4) Lite it
Place charcoal around the bottom of the steel bucket and light it, then insert your crucible and place charcoal around it, if you have a lid place it on top, turn the blow dryer on and place it at the other end of the steel pipe and turn it on. Now you aluminum foundry is done, after about 10 minutes you foundry should be hot enough to melt aluminum.