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Rail Gun

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  • Rail Gun

    This is a fun little project I am improvising out of whatever I can find. For the rails I have 2 440 steel sword blades I will have to make straight. For the power I will use a small package of electrolytic capacitors I got at Radio Shack for around 5 bucks. It is only 1.5 amps, and 250ish volts, but I do not want to be electrocuted, burn my house down, weld my projectiles to the rails, etc..., just have a proof of concept. I can upgrade later.

    For the body, I have some 2X4's laying around that I can use and not miss. Not ideal material, but cheap, nonconductive, and easily replaced. Worse case scenario, I am out 3 bucks.

    First I have to true up my rails, I will do this on my improvised milling machine. (A Central Machinery drill press with a milling vice, and a set of carbide tipped router bits.) Wish me luck.

  • #2
    One, it will not do anything, not even close. Two, dont even THINK about using your drill press as a milling machine EVER. The chuck WILL come loose. You will hurt yourself.

    There have been many threads about this.


    • #3
      Well, you are a little late on using the drill press as a milling machine. I have been doing that for a couple months now. I have had the head come off 2 times, so I will easily acknowledge the danger factor, but I easily blocked the head before it could get to me. 15 years of martial art pays off sometimes. LOL.

      I will heed your advise to some extent though, and I will use my 5lb short sledge, and anvil to straighten the blade spine. As far as it doing nothing, the laws of physics beg to differ. It will not do a lot, I expect cheap BB gun velocities, but this is just a proof of concept, but my math says about 30 meters per second give or take. I am not a mathematician, but from what I read, that is a fair ball park. It would be faster, but I am using copperhead BBs for the ammo. The copper is a good conductor, and the steel core will be easier to remove if it welds. (It shouldn't as I am only using 1.5 amps/sec @250 volts dc).

      The laws of physics state that when I drop the BB in contact with the 2 rails, and apply current, a Lorentz force will propel the BB in the direction of the current. If I use a lot, it will go fast. Or weld. One or the other. In this case, I am using a little and so it will just go.


      • #4

        check your spindle nose.. on my improvised mill ( same thing your doing ) we dismantled the quill and was able to indicate/turn the Jacobs taper down and thread it 1/2 X 20tpi. < it's good to have a bud with a fairly complete shop! > then I could use a chuck threaded on, to eliminate that pesky fly away situation :{D or using my lil Craftsman 109.. I turned and threaded a couple of endmill holders( 1/2" and 3/8ths ID ) and just bought endmills to fit. These two sizes afforded the best compromise and allowed cutters going from 1/8" up to about 5/8ths.. and I made a small flycutter as well...

        if you haven't already?? add the quill supports/bearings, to help take some of the side force/strain off of the spindle!!!!

        this worked fine, with patience and an understanding of it's limitations,,for an improvised shop? I used it for a couple of years, until I was able to add a Seig X2 mini mill, to the shop...

        FWIW.. The family comes first!!! WAY before any of my hobby aspirations..

        Respect Always

        ps, in case you're wondering.. My bud's shop is in another town and not always available for working on MY stuff!!


        • #5
          I am straightening the rails today, I will get a pic or two of that. I will do it on my anvil, and if necessary I will take a touch more off with my press/mill. I will be careful, and I will only take a .001 or so at a pass. (That is what I do for aluminum.)

          I appreciate the tip on threading the spindle, I never thought of that. It will wait untill I have my foundry set up, as I cannot afford to have it done, it no longer flies off (I used a monkey wrench to arbor the thing last time) and one of my first projects with the metal casting will be lathe components. I was going to buy one outright... but 400+ was a little out of my price range. I have a dozen or so scrap yards within 5 miles of here, and I can find all sorts of metal cheap. I just need the patience to cast them, and a hell of an air conditioning system for when I come back inside! (It is hotter than hell in the summer here, and there is ALWAYS humidity.)

          Right now my wife is asleep, and I am watching my daughter. That is why this project was not done a few days ago, I have to work around people, and I typically get all my work done around 10:00pm-4:00am. Lots of fun when you get up at 8:00am. If I am too tired to work safely, I don't. I worked with heavy equipment and explosives before, and it put a healthy respect for safety into me. Makes my projects take forever, but I do complete them, and I always have all my fingers, toes, and eyes intact when I am done.


          • #6
            Bad news, good news.

            Bad news. The 440 carbon steel blades are really really hard. I scarred up my 5lb short sledge, and ruined the edge of my sword (Don't really care about the edge.) In the end, it was bent only a little less than it was before. So, unless I want to machine hardened steel with a drill press...Nope not on the top of my **** to do list, then I have to find another way.

            Good news. I got my crucible cup in today, and I will have a forge inside of 2 days. I have already switched the family to cans from 2 liters. That means that I only have to drink a bazillion cans to have one rail.

            Just kidding. Everyone here has a 2-liter a day habit, that translates to 6 cans per person per day, and at 4 people, that is 24 cans a day. I asked them to binge drink. I also have some bar stock I can melt down. Plenty of metal there.

            I want to post pictures, I took them today, but I am not sure how, I will update this later tonight.
            Last edited by xarlock667; 03-25-2010, 09:39 PM.


            • #7
              Capacitors are not rated in amps.

              I took care of three furnaces at work. Never use pop cans for feed stock for a furnace (A forge is used for smithing, not casting). One drop of remaining fluid from a can thrown in a crucible of aluminum and you will have a nice explosion throwing 1250 degree aluminum everywhere. For this reason always preheat your feedstock whether it be scrap or ingots.

              Also due the thin cross section of a can most of the metal ends up turning to oxide and the coating on the can means a lot of slag. Can aluminum is intended for stamping. Wrong alloy for casting. Use cast aluminum scrap for feed stock and watch your temp when melting. Get it too hot and you mess up the aluminum.


              • #8
                Please listen to Mocona, she knows what she is talking about. Gary P. Hansen
                In memory of Marine Engineer Paul Miller who gave his life for his country 7-19-2010 Helmand Province, Afghanistan. Freedom is not free, it is paid for with blood.


                • #9
                  You are right, and wrong. You can get the amperage if you know the formula.
                  There is a symbol on capacitors, F, uF, mF, and pF. All relating to the Farad. Farad was a scientist back in the day that said "Lets measure the charge of a capacitor in Coulombs! It was such a great idea, they named it Farads instead. 1 Farad is equal to 1 Coulomb. 1 Coulomb is 1 amp per second. This is not exact math, but it rates the fastest time it can expend that much amperage. This equation is the best I could find after an hour or three scouring the net. It is therefore prone to being dead wrong, or outright nonsense.

                  In my case, the measure is uF. The combined uF is 1.5. That should be 1.5 amps per second. I am REALLY HOPING that it is 1.5 amps per second, because a competing site said to multiply the F by the V for total A, and that would 370A, and WAY TOO MUCH for me to use safely. That being the case, I will fire it from a distance, and out side on my concrete driveway.

                  If anyone has better math than me on this, PLEASE post it.

                  As for water in my cans, I am aware of that, but thanks for the tip! I have done a bit of casting before, and I know I have to burn off, or skim off, or pour off the slag before I do any casting with any metal, not just cans. Simple exposure to the air at high temperatures will result in oxidization, take the oxy/acetylene torch as an example. I will remove the slag, and I will do as clean a pour as I am able.

                  In any event, here are the pics I promised:

                  <a href="" target="_blank"><img src="" border="0" alt="Photobucket"></a>
                  This is the swords spine to spine.

                  <a href="" target="_blank"><img src="" border="0" alt="Photobucket"></a>
                  Before I pounded it.

                  <a href="" target="_blank"><img src="" border="0" alt="Photobucket"></a>
                  After about 15 minutes of pounding. The spine failed to straighten, and my hammer was newly scarred. For a 15 dollar sword this thing held up great! Damn it.

                  <a href="" target="_blank"><img src="" border="0" alt="Photobucket"></a>
                  The solution to my problem! The ashtray looking thing is a shiny new graphite crucible. It is sitting on my new aluminum. Had the family switch over from 2 liter bottles. We have a 2liter a day habit, so in 2 days that will all be gone, and I will have my rails!


                  • #10
                    My pics did not post well.


                    • #11
                      yes, I know all about capacitors. There are things that are going to limit your current like ESR (Equivalent Series Resistance). Then there are things that you will need to limit current. Sure your capacitor bank will deliver 1.5amps for a second. But that does not mean it will. You short the caps out and it will discharge completely in microseconds. How fast it discharges will be determined by things like ESR, inductance, wiring resistance, etc. Electrolytics tend to have higher ESR. Thats why pulse rated caps are usually a foil design.

                      What you need to look up is pulse forming network designs for flash lamps like what are used in solid state lasers.

                      For casting there are these little blue tablets you can get from a local industrial supply house that are used to degas the aluminum just before you pour. They are pretty cheap. You take a little piece of one and out it in the crucible and push it to the bottom with something. The stuff burns off and helps degas the aluminum. Makes significantly better castings. Make sure you stand upwind.


                      • #12
                        I hope you make a video of the firing sequence. I wouldn't touch it off unless I was behind a brick wall.


                        • #13
                          Here's the best attempt at a homemade railgun I've seen. You can see how much effort it was to get it to shoot.