Introduction: Wave Pendulum

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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)

Picture of 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!

Picture of 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

Picture of 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!  


Garrier (author)2017-05-12

I second Joshua, I'd like to know the last two measurements as well.Thanks.

aidbar (author)2017-04-12

Hi, I'm making this for my creators project and I was wondering how you attached the balls to the brands and the wood.

JoshuaN68 (author)2017-02-24

You have 15 balls and only 13 measurements. What are the last 2 measurements? Also how did you attach and adjust the strings to the wood?


ronn2set (author)2015-11-29

Hi, awsome project. After going over the process described, how far apart are the individual balls

sciencedude (author)2015-11-15

Hi, how long are the strings, that's critical, in fact that's the whole ball game

JonathanB51 (author)2015-11-02

How big are the ball bearings?

stonerguy97 (author)2015-06-06

Where did you buy ball bearings?

dovefeeder (author)2013-04-10

You drilled round holes for the sqaure legs, how do you fit a suare leg into a round hole

lpeerlings (author)dovefeeder2014-02-11

You can make the round holes as large as possible, so you can fit the legs in it. Later on, you can fill the rest of the 'holes' with wood filler.

lpeerlings (author)2014-02-11

Hey! I really love what you did! I still have a question though.. Do you know what the diameter of these ball bearings are? I'm doing a project at school about this construction so I really need your help (or maybe the help of someone else). And sorry if my English isn't the best, I'm from Holland.

Zachattack2002 (author)2013-12-23

Can you make a YouTube video about this

Wallyman (author)2013-11-24

Hi, where did you get the ball bearings?

phideon (author)2013-03-31

What did you use to fasten the brads down and keep the string taught?

hugskisses13 (author)2013-02-28


tclemmo (author)2012-12-09

That is really awesome! Definitely going to be my Christmas holiday project.

cgreige (author)2012-11-11

do you remember where you bought the gold brads from?

SargentPepper (author)cgreige2012-12-09

Hobby Lobby, but I am sure most Craft Store's sell them in the scrap book section.

Coxster (author)2012-05-17

Very nice instructable. I also made one of these for my dad recently for his birthday.

My method was slightly different, as the wave was designed to be viewed from above rather than the side. Essentially, I had the constraint that for all pendulums, L*sin(θ) = constant. This is an extra complication for many, I am sure. I will be sure to link to your instructable when I post mine for those who want to take a more straight-forward, side-viewable approach.

Good job! :)

shazni (author)2012-01-19

Is each string twisted around a brad and then another string twisted around it and sent down the same hole?

SargentPepper (author)shazni2012-03-18

Sorry for taking so long to reply, the strings are actually pulled through the hole from the bottom and then the brad is put in to plug the string in place. So, at the top you should see both ends of the string poking through. Hope this helps!

shazni (author)SargentPepper2012-03-21

Thanks for replying...yes it did you take a video of your pendulum wave...would love to see how it goes :-)

shazni (author)2012-01-19

please may i have close ups of how the strings are fixed? i'm looks like a 'V' how is it done...could you take close ups of the under side and run me through with an from A point to b point to c point .... please pretty please?
is it one long string? how does it go?...down the pole...through the nut..then back through the first hole or 2nd hole? do you knot it or send it down a 3rd hole?
as you can read i'm pretty confused! please help ..i'm trying to make one with marbles .

SargentPepper (author)shazni2012-03-18

Here is the photo:

SargentPepper (author)shazni2012-03-18

I tried to answer this above, here is a closer picture, I hope the picture makes a bit more clear.

raiderdk (author)2012-01-18

Do you think puting something like a guitar tuning key to adjust string legth will be useful?

SargentPepper (author)raiderdk2012-01-19

I never thought of that but that would be a really good idea! That way if it gets "out of tune" so to speak you could quickly adjust it. I glued the strings in place to ensure that they wouldn't move around, but this is a good alternative as well!

fire_drakon117 (author)2012-01-17

we actually saw a video of this type in my chemistry class. i am forwarding this to him after this comment is posted. awesome job


Kiteman (author)2012-01-17

The world demands a video!

SargentPepper (author)Kiteman2012-01-17

Coming soon!

rjnerd (author)2012-01-17

I love these. Two points to emphasize for people building their own: Using the double strings (the V) is essential. Use single strings, and they will tangle after about 3 swings. Second, the more rigid the frame they hang from, the longer they will swing.  Yours looks good.  (I built one as a trophy, and used single strings, and a somewhat wobbly frame.  Set it going, and it tangled after the aforementioned 3 swings, and until I stiffened the frame, would damp out after a half dozen swings)

If you want to see one (not this one)  in action, go to to see a demo of one built by someone at Harvard.

SargentPepper (author)rjnerd2012-01-17

Great Points! Thanks!

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