Intro: Centrif(r)ugal Casting
I get it. These days, life can feel a little topsy-turvy. When you don't feel like things are spiraling out of control you just get the sense that you're walking in circles. Maybe you thought you'd join a spin class or run on an elliptical but gym's are just too expensive. Well hey, I hear you. I say it's time to get frugal. Centrifrugal. Call me a spin doctor cause I'm about to prescribe something that will revolutionize your orbit. Yeah that's right, you're going to learn how to:
1. Build your very own backyard centrifuge
2. Cast pewter in it
3. Turn your life around!
All for around $100 (or even less depending on how much junk you have lying around the house). With these new life skills you can make cylinders, rings, funnels or other crazy radial shapes out of pewter. I mean hey, give it a whirl. What have you got to lose?
Step 1: Assemble Your Supplies
1. Plywood Sheet
2. Pewter Ingots or Coil of Plumbing Solder (Be sure to specify Lead-Free for either )
3. Shoelace or string at least 3' long
4. 5" dia. rubber wheel with ball bearings
5. 5" dia. plywood cap with hole drilled in the center. (Hole to match dia. of bottom of funnel)
6.Gas camp stove
7. Air dry clay
8. Aluminum funnel
9. 5" dia. x ±3" tall aluminum cooking tray
10. Aluminum Pie Tray ±8" dia.
11. Stainless steel cooking pot that you never intend to use again.
12. (1) 3/8" dia. x 2" lg. lag screw.
13. (3)Small rubber or wood shims.
14. (4) 3/8" dia. x 1"lg. lag screws.
15. Velcro tape strips.
Items Not Pictured:
17. Welding gloves
18. Face mask
19. Long sleeve non-synthetic shirt/pants
20. Leather work boots
21. 2-part steel reinforced epoxy
22. Duct Tape
Step 2: Building Your Centrifuge
+ Begin by gluing 3 evenly placed spacers onto the perimeter of the cart wheel with the steel reinforced epoxy. Make sure that the top of the spacers clear the top of the wheel bearing.
+Once these have set (typically 6-8 hours but be sure to check the setting time called out on the package) glue the larger aluminum pie dish to the top of the spacers. It is very important that this piece is centered precisely on the bearing so that there is no eccentricity when the contraption spins.
+Drive a lag-bolt with a diameter slightly less than that of the wheel bearing hole through a sheet of plywood so that at least an inch or so protrudes from the wood. Add additional lag bolts at the four corners to form leveling feet.
+ Sit the wheel contraption on the lag bolt so that the bolt acts as an axle.
Step 3: Build Your Mold
+Fill the 5” dia. aluminum dish with air-dry clay and carve out the shape you would like your mold to be. Make sure that the shape you carve is both completely centered in the vessel and has an approximation of radial symmetry.
+Once you have carved out the shape to your satisfaction, let the mold dry overnight. Some cracks may form during this process so be sure to patch these with wet clay before proceeding.
+After patching your mold, make a small ring of wet clay around the border of your carving and cap the entire 5” dia. aluminum dish with a 5” plywood disk that has a hole in the center. Ensure that this hole is sized appropriately to receive the narrow end of the funnel. The ring of wet clay should seal your mold and minimize the amount of metal that escapes beyond the confines of your indent. Then use duct tape to secure the plywood cap to the top of the aluminum dish. Make sure it is sealed tight to the clay ring beneath it.
+Cover the bottom of the aluminum dish with hook-side velcro tape.
Step 4: Attach the Mold to the Centrifuge
+Cover the surface of the larger aluminum dish with the loop side of the velcro tape.
+Place the mold in its aluminum dish on top of the velcro and ensure that it is centered on the center of rotation for the wheel mechanism below. Any eccentricities will result in an uneven distribution of cast metal.
+Wind the shoestring around the wood or plastic spacers for about 3 turns. Make sure that the loose end is long enough to pull on.
Step 5: Prepping for Casting
+Be sure to don all of your appropriate casting gear. This includes leather gloves, boots, jacket and chaps. Do not wear anything made of synthetic materials as these items can melt and stick to your skin. Also wear a welding mask or other protective face gear.
+Set up the centrifuge and campstove somewhere outdoors and away from anything flammable. Be aware that campstoves should not be used in enclosed areas as they can emit carbon monoxide which can be fatal.
+Make sure the centrifuge is level with the leveling feet. Place the funnel through the hole in the plywood cap.
+Cut up lengths of the lead free plumbing solder and place this inside of an old pot that you no longer wish to eat from or use again. (if you are using ingots, simply place these inside of the pot).
+Place the pot on top of your camp stove and light it. Keep an eye on it until it melts.
+Once the metal has melted, allow it to heat up for another few minutes and then carefully remove the pot from the stove.
Step 6: Pouring the Metal
+Quickly pour some metal into the funnel making sure that you do not completely fill the mold. The more metal you pour, the thicker your piece will be. You may need to calibrate the volume of metal with the size of your mold and the desired thickness of your piece. Trial and error. That's the way to do it.
+Once you have poured the metal into the funnel and it has flowed into the mold, quickly remove the funnel with tongs or thick gloves and place it somewhere out of the way.
Step 7: Spinning Your Centrifuge
+Pull the shoestring smoothly and forcefully to get the centrifuge to spin as fast as possible.
+Once the spinning has stopped, let the piece cool for 10-15 minutes and remove the plywood cap to see what magic has transpired within.
+ Once the piece has cooled down, you can remove it from the clay mold by adding a little water and prying it loose.
+Congratulations! You've built your own centrifuge! Wheely good work!
Step 8: Troubleshooting
+If you find that your piece has come out somewhat lopsided it is likely because there is some eccentricity to your centrifuge. You may just have to reassemble it, making sure that everything is aligned and centered properly.
+If your piece has just formed a puddle of metal at the bottom of your mold a few different things could be at play. Likely problems are:
a. You did not spin your centrifuge fast enough or long enough.
b. The metal was too hot and the spinning was done before the metal began to solidify
c. The metal was too cool and solidified before you could begin spinning it.
+If the metal solidified within your funnel before reaching your mold you may need to heat the metal up even further or wait for warmer weather to cast your piece.