DIY CONCRETE:: Clock
This Instructable will show you how to cast a fiber-reinforced concrete clock in a melamine box, using a foam knockout to recess the clock hands and mechanism.
About Fiber Reinforced Concrete: CHENG D-FRC is a fiber reinforced concrete mix that is ideal for large or small projects where strength and thinness are desired. Fiber reinforced concrete doesn't contain rock aggregate, instead it contains a range of fibers that act as the aggregate and help bind it together. The 1/4" thickness at the face of this clock is less of a concern with D-FRC because it's designed to be cast thin. The aggregate in regular sacked concrete can be up to 5/8" in size, and getting small forms to fill without large voids can be tricky (a 5/8" rock won't fit in a 1/4" gap). Concrete without aggregate (cement by itself) is brittle, but with that said, try this project even if you're not using fiber reinforced concrete, just take out the larger aggregate, don't mix it too dry, and vibrate the form to remove as much air as possible.
It takes some time to shape the foam knockouts and then they can only be used once, but the foam is relatively easy to shape with hand tools, and the total cost of forming materials is pretty cheap.
Because I didn't have so many pictures of this project, I modeled it in sketchup to help explain the process, hope it helps!
Materials + Supplies:
- Clock Kit + AA Battery
- 3/4" Melamine coated particle board (or equivalent)
- 1-1/4" Drywall Scews
- Blue Insulating Foam / Styrofoam 1" thick
- 7/16" Dowel Rod (2" long)
- Spray Adhesive
- Clear Packing Tape
- CHENG NeoMix D-FRC Casting Blend - Light Base
- CHENG NeoMix D-FRC Activator
- Hand Saw / Table Saw
- Screw Gun + Pre-drill bit
- Drill + 7/16" Drill Bit
- Caulking Gun + 100% Silicone
- Sanding Block + Sandpaper (60,100,220)
- File / Rasp
- Acrylic Shaping Rods for tooling silicone beads
- Bucket / Paddle Mixer
- Particle Mask
- Rubber Gloves