Intro: How to Make a Single Octave Xylophone
Made for a class project, this Instructable will tell you step by step the process we used to make this xylophone. It spans one octave and hits all the notes in a scale. Including the tuning, building, sanding, painting process, it took about 7 hours to make.
Step 1: Setting Up the Keys
This is just what we used and this isn't exactly what it ended up being, but each key was 2 inches wide, and one inch thick, with varying lengths...
General Lengths for Keys:
C (low): 14 inches
D: 13.5 inches
E: 13 inches
F: 12.5 inches
G: 12 inches
A: 11.5 inches
B: 11 inches
C (high): 10.5 inches
This is what we started out with, in hopes that it would already be tuned. However, this was not the case, so we had to go on to tune each and every key to an appropriate scale.
The types of wood were a bit tricky to sort out, but we found a balance of good sound and well priced wood was to use Pine. The amount of wood we bought (and we had extra) was about $14. You could go for some more expensive Rosewood, but this works just fine for us.
Step 2: Tuning
Steps for Tuning the Keys:
1. Set up a tuner nearby, and set up a towel to lay the keys on (in order to let them resonate).
2. Strike each key with the mallet you will be using in order to find out exactly what note the key is now. (if the key is supposed to be a C, but rings a D, you now know the key needs to be lower in tone)
Notes are defined by the frequency of each key. The frequency that each key has when stricken defines these notes.
3. Measure 2/9ths in from each end of a key (for example, this will be 3.111 inches in from either side of the 14 inch key) to find approximately where the nodes are.
Nodes are the areas of the keys where when the standing wave vibrates the key, there is no motion.
4. To alter the frequency of the notes of the keys, you need to finally start tuning it. To make the note a lower pitch, you need to carve a curved gouge from on the underside of the note. (i used a large rasp). To raise the pitch, simply file or saw off bits of the ends of the keys.
By the way, this gets a little messy, so i would recommend that you put some newspaper down below to catch the shavings.
MONITOR NOTES CONSTANTLY
The photo is of me using the rasp to file out a curved center in between the nodes.
The other is what an ideal tuned key would look like from the side.
Step 3: Nodes of the Keys
When finally done tuning, you must re-find the nodes. To do this, evenly spread salt onto a key, place the key on a shock absorbent surface (the towel will do again) and hit with mallet repeatedly. When doing this, the vibrations caused by the mallet will cause the key to vibrate, and the anti-nodes of the standing waves to move the salt over to the nodes of the key. There should be 2 nodes here, and they should generally coincide with the 2/9ths sections you found earlier.
An Anti-node is the part of a standing wave, where the wave moves up and down the most. This is where the key should vibrate the most.
Mark where the salt accumulates with a pen on each node (this might not be in the very center of the key, or in a straight line, just mark it as close to the center, but still on the node, as you can).
These two places will be where you will drill the holes for the nails (or screws) that will hold the key to the frame. When drilling, make sure to make a hole big enough so the nail/screw DOES NOT TOUCH THE KEY ITSELF. It may rest upon the side, but this should by no means firmly hold the key in place.
The reason why this is, is because for the xylophone key to make a note, it needs to be able to resonate and make sound waves by vibrating. If you had simply drilled or nailed the key to the frame, it would not make the note you want it to.
See the comic i made to explain why the nodes are where they are.
Step 4: Attaching It All
Once the over-sized holes are drilled, you will need to create a frame.
Things to keep in mind:
1. Each key should be about 1/4 of an inch apart from each other, the whole xylophone will be about 17.75 inches long (if using previous measurements).
2. You need padding in order to ensure the keys can vibrate and resonate well.
3. There should be an opening in the middle to allow the keys to create a louder sound.
To make it:
1. Lay out the keys in the order they will be in on the xylophone (ie, lowest on the left all the way to the highest note on the right), and try to line the nodes up in as close to a straight line as possible.
2.. Find some scrap wood that will be long enough to reach the whole length, as well as wide enough to fit all of the nodes onto the surface.
3. Wrap the two pieces of scrap wood in a shock absorbing surface. I used to wash clothes wrapped around multiple times to ensure that the notes will be pure.
4. Place the keys onto the 2 pieces of scrap wood, and drill starter holes into the wood, to mark where each node will be.
5. Drill each drill through the holes on the nodes, to where it is firmly into the scrap wood, but does not touch the sides or top of the key. The heads of the screws or nails should be bigger than the holes already drilled to prevent the keys from slipping off the xylophone
Take 2 more pieces of scrap wood and attach them to the ends of each part of the frame, to hold it all together and keep it from wiggling from side to side. Two screws firmly screwed in on each corner will do the trick.
Step 5: Decorating It
Now that you've (hopefully) made a working, well tuned xylophone, the last step is to make it yours!
First thing is to sand everything down, make sure that all the edges are smoothed
Then we used a dark red house paint to color the keys, but it really doesn't matter what kind of paint you use. We did 2 coats on paint to make sure that all the wood was covered.
Let it dry through each coat, but to make sure we waited a day for each new coat. This process took about an hour for 2 or 3 even coats.
You could also explore with wood finishes to go for a more processional look.