Sunday, December 31, 2017

Sand Timer-Flip Over

Here is a different type of sand timer. When it is upright the sand will flow from one side to the other and the weight of the sand will pull the block over. I tested it and it is 2 1/2 minutes on each side.

A 2x4 is will be used for the sand timer, it is a softwood and easy to work with.
The length will be 10 inches. 

I marked the centres of the wood block and  drew 2  channels. Note both ends have to be cut at 10 degrees. This will help the block pull over when the sand fills a channel.   

A  Miter gauge is set to 10 degrees and both ends of the block are cut. These can later be sanded to get the sweet point for tipping over after the sand is added.

To keep the cuts as neat as possible I started with a 1 1/8"  forstner bit for each end then the rest can be cut using a jigsaw. The channels will be cut the same width.  

A jigsaw can make the rest of the cuts but it could turn out a little rough. If it needs a little cleaning a file and some sandpaper will finish the job. Make sure you can see the pencil lines and stay as close as you can to them.


          Watch the step by step Video here and don't forget to  Subscribe to 
          my channel. 

Now is a good time to drill the hole for the sand. I will use a wire for this. 
The wire I used did not fit in the chuck of the drill so I cut a small piece of plastic from an electric wire and put it on the end of my wire drill bit and now it fits tight in the chuck.

Mini wire drill bit.                                               

After the hole was drilled a piece of 3mm Baltic birch was glued onto the back. I always like to cut a piece bigger than I need and then trim it down and fine sand it later.

                     Sand was sifted to make sure it would be consistent in size so no                      large pieces would clog the hole. A large cup of sand was ready to                      use. I tested what I had so far to make sure everything was flowing                  from one side to the other.  

I purchased a piece of plexiglass at a local plastic shop for $2.00. The Plexiglass was put onto the block and a Sharpie was used to mark where it had to be drilled. It was first drilled and then countersunk.  

  The plexiglass was trimmed on the bandsaw and then taken over to the belt sander and cleaned up even more taking off the rough edges and making it look smooth.

The sand timer is an easy build and so far I am using it in my shop for fun. The loud bang is makes a good alarm. It can be calibrated to get the exact time by adding or taking away sand and sanding the round edges.

 Similar to the pomodoro technique I am using to do small chores around the shop like cleaning, sweeping or organizing a drawer. 

See Also:

                 Puzzle box                                        Floating Dowel


Saturday, December 2, 2017

Double Pendulum

A double pendulum is a pendulum with another pendulum attached. The motion of the pendulums is governed by a pair of coupled differential equations and is chaotic.

This will be an easy build using mostly woodworking skills.  Subscribe to my Channel to learn how to make more woodworking projects. 


                                         Double pendulum


The pendulum will be made of wood so it must have a heavy base to keep it from moving around. In order to do this lead weights will be added.

The base (4"x8") is made of three pieces of 1/2"plywood. 
They will all be glued together but first one of the three pieces -the middle one- has to have a section   cut away, this will be for some weights.


A forstner bit is used to drill four holes in the centre piece, this will make it easy for a jigsaw to fit in to remove the marked section. 


Here the piece is cut, it does not have to be a perfect cut since it will be the middle part of the base and will not be seen. Notice the protrusion, that lines up with the post and will add support for the screws for the post.


I found some lead weights in my shop and placed them on the bottom of the base. They can be loose since the middle piece will keep them secure. Any weights will be fine, you can try a hobby store or use some fishing weights.  


 The bottom of the base will have two holes, they are drilled and countersunk, this will be for two 3" screws for the post. 


A 3/8" hole is drilled in the post for a bolt which will hold the bearing. A carriage bolt will work fine for this project. It has a round head and square neck, when the bolt is hammered into post it will be secure. 


So far the base, post and bearing bolt is made. It has a good weight and good height. The post is 14" high and with this information we can move on to the arms. 

For the arms a rough design was marked with pencil and cut with the bandsaw. Then they were  further shaped and cleaned up with belt sander.

A 1" Forstner bit is used for the hole for the bearing. I tested the bearings and my bits and got lucky with a tight fit.

 Two holes in the large arm, one for the bearing and one for the 3/8 bolt to attach the smaller arm. 

 The bearings are ready to be put in the arms. I used my vise and squeezed them in giving them a tight pressure fit. My  vise jaw liners were used so the bearings and the wood would not be marked. 

I gave the pendulum some stain and then bolted it together.  

Small lights can be added to the arms. After the shop lights were dimmed I gave it a spin and played with it for some time. This is a fun toy for any age. I am sure I will be making some more.

See Also

               Levitating Dowel                                  Spring Gun