Introduction: A Simple Steel Recorder for Kids to Make.
I've been using this project with my grade 7 kids for a few years now. Its great because it is simple, fun and has a ton of learning packed in. I'll set this Instructable up as a Lesson Plan for teachers so here's the start...
It was pointed out to me that this project is actually a tin whistle or a penny whistle.. not a recorder! Well there you go! learn something new everyday i say. Thanks for the correction... I don't think i can change the title because it is in the teachers contest BUT when you present this to your classes be sure to update. Thanks!
-The student shall be able to demonstrate the safe use of basic metal working tools including the hacksaw, files and Drill Press.
-The student shall be able to use the metric scale to accurately layout a design on steel.
What I will do is an overview of what I do each class with the students. Along the way you'll find notes on basic tips that I've found work well with kids. Try this project with your class (or kid) and in a short while the air will be filled with melodious tunes and screeches as the kids proudly show off their new instrument.
-Steel pipe. 1/2" ID 1/16" wall. 35cm per student
-Steel pipe. 5/8" ID 1/16" wall. 3cm per student. You can also find the same size conduit... usually free at supply houses...better to use because it has a nice thin wall.
-Wood dowel 1/2" diameter. You can also use solid cold rolled 1/2" steel.
-Hacksaw with 24T blade.
-Flat smooth file and medium size smooth round file.
-5, 6, 7 and 8mm drill bits.
-Buffer (not required...)
Submitted by HD Stafford Middle School for the Instructables Sponsorship Program
Step 1: The Basic Idea of Sound and Measurement.
I introduce the idea of a sound wave to the students by drawing 2 waves on the board with different distances between the peaks of each wave. I explain that the waves that are further apart are lower frequencies. What really drives this idea home is if you explain (and humm... which they love to hear if its bad at all :-) ) what a car horn sounds like as it comes towards you (increasing pitch) and as it moves away from you. (the pitch lowers)
Link the idea of a wavelength to the tube of the recorder... longer tubes make lower sounds. Be sure to reinforce that the tube length has to be perfect or it will be out of tune. Covering or uncovering holes in the side of the tube effectively change the size and therefore the pitch of the sound. Holes in the wrong spots means that the recorder will be out of tune. This is all good stuff because it motivates the students to measure carefully.
Now is a good time to talk about using millimeters and centimeters. I'm sure you have stuff on that... if not, the web has tons of resources. Read ahead because I have a few tips on measuring with kids...
Step 2: Cutting the Tube.
Pull out your basic steel tube. I use the cheap stuff with a 1/2" I.D. and a 1/16" wall. Clamp it in the vice. I show the kids how important it is to clamp the spot you'll do the cutting at close to the vice so it doesn't screech and howl. Demonstrate how this sounds. They like horrible noises.
Now measure a spot 35cm from one end. Really, all you need is 30cm but I leave extra for mistakes and, well, really... it forces the kids to measure 35cm with a 30cm ruler. Grab the teachable moment even if it is a bit pre-arranged.. :-)
Pull out the hacksaw. Students tend to stuff the saw into the steel. Tell them to lift it up a bit and take it easy. Some kids even cram it so hard that when it breaks through they inadvertently punch the vice.
Demonstrate using the flat smooth file to remove all the burrs. Use a smooth rat-tail file to smooth the insides.
Step 3: Cutting the Windway.
Use the chalk board to draw the windway. I worked with a guy once who used chalk and drew all over the steel work tables. Very cool. First demonstrate drawing a centerline all the way down the length of the tube. Explain off-setting a line and draw 2 parallel lines 4mm offset from the centerline. Connect the lines together 25mm down from the end.
Cut the short line that joins the 2 longer lines. DON'T cut all the way through. Just cut until you've joined the 2 long lines with the saw line. It's okay to go through them a bit.
Now demonstrate cutting the long lines from the end of the pipe to the line you just cut. It's okay to cut into the other side of the tube. (Later the kids will cut a 45 deg angle on the end.) Kids find this step tough. Make sure that if they are right handed they are holding the handle with their right hand and standing to the left of the tube. Get them to spend a long time just pulling back until the cut gets going.
Once the kids manage to cut to the short 8mm line you can talk about work hardening steel. A good example is how the kids can break a coat hanger by bending it back and forth. Now tap the small tab you've cut out back and forth until it breaks off. Use a file to smooth the break line until it is about 45 deg. File inside and out to remove burrs.
Step 4: Cutting the Plug and Sleeve
Once the kids have removed the tab and filed a nice clean angle on the tube you can get them to cut out a plug.
Push a 1/2" dowel into the hole until the space between the edge you just cut and the end of the dowel is about 6mm. Gently sand the edges of the dowel. Make sure that the kids don't sand off so much that the fit is sloppy. Also... when you're buying dowel bring a piece of the tube with you and test it. The dowel should be tight and some dowels are way less than 1/2" despite being labelled as 1/2". I also use 1/2" steel solid hot rolled... Use what you have!
Now cut a piece of the 5/8" ID tubing. I've been using conduit as well... super cheap (usually free) and a nice thin wall. It should be about the same length as the dowel. Gently file the edges. Notice the seam on the inside of the tube... turn the tubing until that edge is facing down and the tube should be tight. Sometimes i have to cut a strip of paper to act as a shim... It's okay to use a hammer as a way of putting the piece on but make sure the kids tap gently all around... they tend to line it up and hammer the heck out of it... straight or not. :-0
Step 5: Getting a Sound
I use a Long piece of 7/16 OD steel or something else thats small enough to fit into the recorder without binding to move the dowel. You'll also need to open a vice just enough for the inside tube to fit through but not the outside tube. The idea is that you should blow through gently and get a nice breezy low tone. If you blow harder it should jump up to the next octave. This is actually WAY easier than it seems... just tap the dowel and the sleeve back and forth until you get a soft low note. Keep the edge of the dowel and the edge of the outside larger tube parallel so they maintain the same distance from the inside edge of the channel (windway).
I've found that a 6mm gap works well with a 8mm wide channel cut out.
Most kids will blow way too hard and end up screeching and wailing at a really high octave. Get them to almost just breathe into the end than gradually increase the pressure until they get a sound.
If you can't get a low note the culprit is probably the edge of the windway where the air hits the bevel. Get the student to take it apart and file more of a smooth angle... it should almost look like a thumbnail with a curved edge...
Step 6: Laying Out the Holes
I always draw this on the board. What i do is draw the profile of the tube with the outside tube at the left with the windway channel showing clearly.
First draw the length from the edge of the windway to the cut point on the tube which is 268mm. All the measurements are made from the windway beveled edge. Doing this should get you a "D". File material off a bit at a time until it resembles a D. We're not talking about a $400 instrument here folks. Close is good.
Here's a link to a really simple tuning fork. Gotta love the internet.
Make sure the centerline is still easy to see. Get the kids to re-draw if necessary. Measure from the windway to the 6 spots and mark with a sharpie.
What I've noticed with kids is that they have a tough time with decimals. I explain "whole numbers" and ask if a number after a decimal is a whole number. I explain that it isn't because the number after a decimal is a PART of a whole number. Tie this idea to each number 1,2,3,4... etc on a ruler. The number BEFORE the decimal is a whole number...say.... 11. The numbers AFTER the decimal is a PART of a centimeter which means that they can use this number to count how many PARTS of a centimeter there are. For example, 11.5 would mean the kids would count to 11 along the ruler in centimeters than count 5 lines between the 11 and the 12 in millimeters.
Cradle the pipe in a vice and centerpunch all the holes. I get the kids to punch in way more than I would normally... round tubing can be tricky.
Step 7: Drilling the Holes
I've built a simple jig for holding the tubes when drilling. All you do is find a piece of hardwood thats 6" by 12" and about 1" thick. Use the tablesaw with the blade set at about a 40deg to cut a groove. Flip the piece and cut the other side of the groove.
Use a C clamp set up on the drillpress to drill the holes. I have most luck with kids drilling round tube if I draw a circle on the board with a drill pointing to it... If the drill is off-center the kids can see how it would deflect and break the bit.
Don't buy cheap drillbits... I've had them break and shatter. I also would not suggest using drill bits smaller than 1/8" with kids and steel tubing... They break them in huge amounts...
The best thing to do is not to just go ahead and drill all the hole sizes at once. Pre-drill with a 1/8" drill bit for all the holes first. Set up as many drill presses as you can to minimize line-ups.
Step 8: Drilling Holes Pt 2
During the last step the students probably tried the recorder with the small holes and thought it sounded terrible. Probably did, too. :-) The holes all need to be drilled to the correct size now. You will need a 5,6,7 and 8mm drill bit. I set up 2 bit sizes on drill presses than make a BIG sign over it so the kids don't get confused.
I've tried just telling them but that never works...
The drill bit that gives the most grief is the 8mm... get the kids to spend a bit more extra time in set-up making sure that the hole is well lined up.
Now file inside and out!
Step 9: Finishing
Get the students to go over the tube with a piece of 120grit than move up in stages to 320.
if you have a buffer go for it. I give a big demo to the kids explaining how the buffer can be really dangerous... especially when it is underestimated... "it's so SOFT" is what kids say. I tell them to NEVER point up with the workpiece... always down. Also, kids don't realize how hot the metal gets so make sure they understand how friction creates ALOT of heat. Don't wear gloves because the buffer can grab the gloves and pull a kid into the machine.
When i mark the project i have the kids bring in a marking sheet (which is below) and play through the scales. They should be able to play 2 octaves for an A... I use this kind of marking sheet because its as objective as possible which is tricky in the shops... This marking sheet is great because the kids know what to do to get an A... if they don't, i always give them time to go back, fix or improve than re-submit. I always give kids the chance to get a good grade.
Recorder Marking Sheet
Tubes not cut straight, rough edges, missing parts
Windway wrong size, not filed
Tubes filed clean, windway close to spec… filed but not perfect. Ends all flush within 2mm
Perfect windway. No rough edges, square lines. Ends all filed flush exactly to 8mm wide
Missing holes or more than 3 wrong. Not filed, not on centerline
All holes drilled to spec within 3mm in position. All holes to correct diameter. On center line. Fairly smooth edges
Exact sizes and postions, exactly on centerline. Filed perfectly
Completely out. Not able to get a low note
Low tone possible but scale is rough
Perfect scale 2 octaves.