Updup Posted November 8, 2010 Posted November 8, 2010 The energy dissipated between 2 media surfaces could actually be quite high as the area of contact between these would be very small resulting in the possibility of very high pressure being imparted on the powder; this coupled with the large number of impacts "could" have created favourable conditions for ignition in G Smiths mill. I think Gary was also using ceramic media but I might be wrong. Pounding BP seems to be less dangerous when you consider how many years this procedure has been carried out and the number of rockets etc. made but there are still accidents that occur - pinching comp on a rocket spindle is probably the biggest problem. Ahh, Doh! I didn't think about that one, thanks. I've heard ceramic creates sparks, but only light emiting sparks, so no heat is invloved, how right is that?
dagabu Posted November 8, 2010 Posted November 8, 2010 Well buddy that is what I think.The motor on mine is located below the drum as a lot of them are.We knowmotors have brushes that produce sparks. Fly AC motors dont have brushes, bearings and windings can cause enough heat to cook off the BP. Ahh, Doh! I didn't think about that one, thanks. I've heard ceramic creates sparks, but only light emiting sparks, so no heat is invloved, how right is that? Yes, SOME ceramics create triboluminescent "sparks" that are not heat producing. The same type of effect can be seen with some lifesaver candy with crystals. Triboluminescence is light produced while striking or rubbing two pieces of a special material together. It is basically light from friction, as the term comes from the Greek tribein, meaning "to rub," and the Latin prefix lumin, meaning "light". In general, luminescence occurs when energy is input into atoms from heat, friction, electricity, or other sources. The electrons in the atom absorb this energy. When the electrons return to their usual state, the energy is released in the form of light.
Fly Posted November 8, 2010 Author Posted November 8, 2010 I did not know a AC motor had no brushes?My AC highspeed hand grinder does, & my AC drills do.I don't know muchabout electronics but now I'm really confused???????????????? Fly
Updup Posted November 8, 2010 Posted November 8, 2010 I did not know a AC motor had no brushes?My AC highspeed hand grinder does, & my AC drills do.I don't know muchabout electronics but now I'm really confused???????????????? Fly IIRC, AC are brushless, DC have brushes, however you can simply put a brige rectifier in to change AC to DC. I
dagabu Posted November 8, 2010 Posted November 8, 2010 IIRC, AC are brushless, DC have brushes, however you can simply put a brige rectifier in to change AC to DC. I Sorry, a non-rectified AC motor has no brushes
Col Posted November 9, 2010 Posted November 9, 2010 I use a TEFC motor (F class insulation) mounted outside the box so it runs cool. Mounting it under the drum would save some space but to my mind its just added risk if the jars ever fail.
Bonny Posted November 9, 2010 Posted November 9, 2010 TomorrowI'm going to pick up some thin wall stainless steel tubing & cut it into one inch peaces & fill them withlead to stop the wear thing on the media. Fly Going to a harder media won't stop the wearing issue. SS will wear less than brass or lead, but will still wear. Remember, the media is still rubbing and bumping into each other for hours at a time... Any material will wear in time.
cds333 Posted November 17, 2010 Posted November 17, 2010 That's why I use a plain piece of 4" PVC with two of those black rubber endcaps instead of the standard PVC pipe/PVC endcap/reduction-coupling jar design- they just slide on and are tight enough to keep any powder from leaking out even without the hose clamps, and should the meal spontaneously ignite they are loose enough that they will blow off before the pressure in the jar reaches a dangerous level...Yeah it would still make a big mess but no dangerous pressure issues or PVC shrapnel
Anarchy08 Posted January 3, 2011 Posted January 3, 2011 hi all,just thought this seemed a reasonable place to post this, I'm an Aussie pyro , so rare unfortunatly, anyways here ya go just thought i would show off my newly refurbished ball mill, optimised to 75%CP rotating the mill jar at 84 rpm.the base and midplate are made from old jarrah worth round 60 bucks that i had lying around the place. the motor is a 1/4 horsepower that has been mounted upside down with washers as spacers to tighten the belt. using 4 skateboard bearings(12mm ID 28mm OD) used a hole saw to cut out the right diameter into the mounts. the pink on the outside to the 12mm plain steel is heat shrink (i know, not the most complementary colour http://forum.truebluepyro.com/Smileys/default/tongue.gif) was the easiest option for providing grip from the roller to the mill, the black rubber was purchased from clark rubber and works surprisingly well, recommend using a heap of epoxy to keep it on though. the whole frame cleaned up with putty, sanded back nd whacked with 2 coats of varnish. 1: http://s1211.photobucket.com/albums/cc429/mang_the_pyro/?action=view¤t=mill1.jpg2: http://s1211.photobucket.com/albums/cc429/mang_the_pyro/?action=view¤t=mill2.jpg3: http://s1211.photobucket.com/albums/cc429/mang_the_pyro/?action=view¤t=mill3.jpg hope this does inspire others to build there own it is not difficult and you can create a mill that is not only functional but pretty to look at.
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