Bottle Rocket Lamp

The bottle rocket lamp is a quite simple project you can finish in one day.

Materials:

• Plywood about 620 x 400 x 15mm (I've used beech plywood)
• Bottle made of frosted glass (clear glass will not distribute the light evenly)
• LED spot (don't use incandescent bulbs - they generate too much heat, burn your wood and may burst the bottle)
• 4 dowel pins
• Some wire to connect the LED spot
• Sanding paper
• Some walnut oil ( or clear varnish) for finishing

Machinery:

• CNC router (however you can also do this with manual tools - it is not too difficult)
• Manual router with edge rounding bit

The main difficulty is to get a reasonably accurate CAD drawing of the bottle:

• Take a picture of the bottle:
  • Make sure your camera is not just looking but also positioned at the center of the bottle. If the camera is out of center your picture will be distorted.
  • Take the picture from as far away as reasonably possible - this will also minimize distortions.
• Vectorize the image:
  
  • Import the image e.g. with LibreCAD: File -> Import -> Insert image
  • Lock the image layer
  • Add a new layer for the drawing
  • Draw the bottle shape using lines and arcs
  • Finally resize the drawing to the correct dimensions

• You can do the same with the LED lamp - however as it is quite small and relatively simple I've just measured it with a caliper.

• Once you have the bottle and LED lamp you can draw your rocket around it.
  • Be careful: you need to take 0.5x material thickness away from the side fin or you'll end up with a much too large bottle hole.
  • You should also make the side fins a little shorter than the main body - the tip will not look nice if they are equally long.
• Add 2 slots for the wire so it won't hinder assembly.
• Add 4 holes for dowel pins to keep everything together.

I've used my CAM software Estlcam to create the CNC Program for the machine:

• After the parts have been milled we need to drill some holes for the dowel pins.
  • You can mark the hole positions with dowel centers - this is more precise and reliable than measuring and marking with a pencil.
• Don't drill too deep at the top!

The parts are a bit slim to use the router correctly and I unfortunately don't have a router table.

So I just improvised a bit and clamped the router upside down to my machine to use it as router table.

Sand the parts and apply some walnut oil or clear varnish.

I prefer walnut oil as it makes the wood a little darker and highlights the grain...

Solder wires to the LED spot, put it into the rocket and press the wires into the slots.

• Fill the bottle with water
  • Add something to make it a little bit cloudy - I've used grapefruit lemonade. This will help to distribute the light evenly. Clear water will concentrate the light at the top of the bottle, too dark water will concentrate it at the bottom. You'll need to experiment a bit until you're satisfied with the result.

• Insert dowel pins and add the fins.

• Do not glue the parts together - the dowel pins should be enough to hold everything in place. If you glue you can't change the light or bottle anymore.