Introduction: Wave Pendulum

The holiday season is much anticipated by people of all ages, it is a time for good food, family, vacation, and fun!  But also a time to figure out what to give people... which can prove to be a difficult task.  For me, it's one of those things that I have great ideas for all year round but when the time comes I can't think of anything to give people, especially my Dad.

His christmas list this year consisted of dress socks, ties, and books... boring, boring, boring.  So I was thinking back and remembering the days when my Dad would be delighted to receive a picture I drew or some art project I created for him (this was in the good ol' days when I was 5 or so) and was wishing it could be that easy (and cheap) now! 

That got me thinking... what if I made him something?  He has a large desk at his office, and I wanted to make him something he could display. I thought of a newton's cradle but that was too simple, I was looking for the wow factor. 

After searching on the web I came across this youtube video, pretty neat right?!  Kudos to this website for giving me some information on the apparatus so I could build it!

So that was that, I was going to make him a wave pendulum.  It is unique, a perfect conversation starter, and would look great on his desk... it's also a way cooler gift than a pair of socks :-)  Besides this one looked so neat after it was done that I am in the process of making a mini one for my friend's desk!

Step 1: Materials


- Titanium Epoxy (or any type of glue that bonds two metals together)
- Thread (Needs to be thick so the weight of the ball bearings doesn't break it. We used fishing thread for this, and it worked well)
- 15 Ball Bearings (Or any other type of semi heavy ball would work... I think marbles would work as well)
- 15 Gold Brads
- 15 Nuts (as small as you can get them, so when they are attached to the balls they don't take away from the sophisticated finished  
- Hot Glue
- Wood Glue
- Drill
- Straight edge
- MDF Wood for the base (this is a type of compressed wood, but you can use whatever you would like for the base)
- Bass wood for the legs and top of the structure (4 1/2"x1/2" pieces and 2 1/2"x1/4" pieces)
- Saw to cut the wood (preferably one with fine teeth so you get a more even cut)
- Black acrylic paint for the base (or you can choose to stain it, or paint it a different color, whatever your artistic heart desires!)
- Wood stain for the rest of the structure

Step 2: Preparing the Base

Cut a piece of MDF (compressed) wood, or any type of wood you choose, to the dimensions of 9.5 inches by 22.5 inches, for the base.   This gives you a broad enough structure so you have a good-sized "viewing window" for admiring the wave pendulum effect when you are finished.  

Once you have the proper size base you need to drill the holes for the four legs of the structure.  To ensure that the legs are evenly spaced, measure 1/4"  from the edge of the board on each side and place a mark with a pencil.  Using a straight edge connect all of your marks so you essentially have a 1/4" border around the entire base.  Where the lines cross at the corners (see second photo below for clarification) pencil in a large dot.  This is where you will drill a hole for the legs of the structure.

Before drilling the holes place a scrap piece of wood beneath the base, in the event that you accidentally drill through the wood base entirely you don't want to hit cement thereby dulling your drill bit.   Now keep in mind that the legs of the structure are 1/2" by 1/2" so you don't want a hole so big that the leg will be swimming in it.  I made that mistake and it caused some assembly headaches, so go for a snug fit!  Don't drill all the way through the wood, 1-2 cm deep will be sufficient.  But make sure you are consistent for each hole: measure after you drill and make the holes as close to the same depth as possible so your structure is even!

Step 3: Preparing the Legs and Top

The Legs:
-Using a fine tooth saw, cut the 1/2" by 1/2" bass wood dowels to 18.5" long for the legs of the structure.

The Top:
-The top consists of three pieces, and they are created using the 1/2" by 1/4" bass wood.  Cut two 8" long pieces of this bass wood to connect the two side legs together.  
-Cut one piece of this wood 21" long, to connect the two sets of legs together lengthwise.
-The longer piece of bass wood is what the balls hang from, and so you need to drill 15 evenly spaced holes in the top.  Choose a drill bit size that is slightly smaller than your brad size so you ensure a snug fit.  My holes were approximately 1.5" apart.
-Once again when drilling the holes, put a scrap wood board beneath your top piece.  This time you are drilling all the way through the wood, and you don't want to dull your drill bit!


Step 4: Assembling the Wood Structure

First you will put the legs of the structure into their predrilled holes.  Fill each of the four holes with wood glue and then set the legs into the holes.  To help stabilize these legs while the wood glue dries you can use a dab of hot glue (comes off readily) on a piece of wood and glue it to both the base and each leg (see picture two).  You will take this piece of wood off once the wood glue dries.

Next, (this can be done before the wood glue dries as well), glue the two smaller top pieces into place.  This will also help ensure that the wood legs dry straight and the proper distance apart.

Once the wood glue has dried for the most part (not necessarily completely, but has stabilized enough) glue the long top piece into place.

Once that is completed wait for 24 hours until the wood glue dries completely.

Be sure you keep an eye on this structure, if you notice a leg tilting use more wood or a string to stabilize it! Don't underestimate the importance of the structure's stability.

Step 5: Assembling the Ball Bearings

While you patiently... or not so patiently.... wait for the wooden structure to dry you can begin creating the ball pieces of this pendulum.

First mix a small bit of your epoxy. You don't need much epoxy as the nuts are super tiny and that stuff is pretty strong.  Speaking of which... you need to be careful when using this!  Do not get it on your hands, and don't lean in too close thus breathing in the fumes.  It's completely safe to use, but only as long as you use some common sense.

Once you mix the epoxy you have about 5 minutes to assemble the ball bearings before the epoxy doesn't work any more.  I would recommend making about 5 balls at a time and then mixing up some new epoxy.  Using a pair of tweezers pick up a small nut and dip it into the epoxy, then set the nut onto a ball bearing.  Be sure to place the nut on the ball bearing so that the nut is vertical and not at some odd angle.

A helpful way to ensure that the balls don't go rolling all over the place, thereby frustrating you, is to use some styrofoam!  By indenting a piece of styrofoam you have a place to set the balls down so the epoxy can adequately dry.  Once the epoxy dries pick up each of the balls by the nut and ensure that the bond is strong, if the nut falls off, try again with a little more epoxy.

Then let these set overnight as well. 

Step 6: Finishing the Structure (Assembly)

The next step is to fill in the holes where the legs are inserted into the base.  Using wood filler, fill in each of the four leg holes.  Let this set up, and then sand it down to become as smooth and level with the rest of the base as possible.  This will make the finished painted product much cleaner.

As you can see in the pictures, I put the strings and the balls on the structure before I painted it.  I would NOT recommend this, it is far easier to paint without the strings and balls on the structure...

So after you fill in the leg holes you are ready to paint and stain!

Step 7: Painting/Staining!

Now, it is best to stain the piece before painting the base.  (Painting over stain  looks better than attempting to stain over your paint... that doesn't turn out too well :) )

To stain the base you need two cloths.  One cloth to apply the stain, and one cloth to wipe the excess stain off.  This method will give you a much more even stain coating, and ultimately a nicer finish.

Once you have stained the piece, and allowed the stain to dry for 24 hours you can paint the base.  I used acrylic paint, but I think spray paint would work as well.  If you use spray paint make sure that you tape the legs and top of the structure really well!  

Step 8: Timing/Final Product

Now attach the strings and balls to the structure with the gold brads! You are nearly done! Below are the necessary lengths of string to achieve a 1 minute period for the entire wave effect.  Essentially it is timed so that each ball has one oscillation more than its' neighbor.  For example, the longest string achieves 51 oscillations in one minute, the next longest string achieves 52 oscillations in one minute, the next one achieves 53 oscillations in one minute and so on.  The shortest string achieves 65 oscillations in one minute.  I imagine that as long as you ensure each string has one oscillation more than its' neighbor you are fine (the number 51 will ensure that your end result is a one minute long wave effect period, but if you started at 50 oscillations in one minute, you only end up changing the length of the wave effect, but it still works just the same).

Here are the approximate lengths from the longest string to the shortest one:
* Now keep in mind that these are rough estimates and may take further tinkering to perfect.  I found out that this process is very tedious as the smallest adjustments can make a huge difference...and can take hours. So be patient!  Your patience will be rewarded.

 I filmed the wave pendulum before painting it... got a little impatient and wanted to see how it turned out before I painted it. (I will post a video really soon showing the wave effect my pendulum produced!)


My dad loved it! It works great on his desk, and I must say I find it to be oddly calming and transfixing to watch the wave effect.  I am really excited to see how my mini one turns out.

If you have any questions about how I made this I will respond to comments as quickly as I can!  
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