CHIME SF is a large scale public musical instrument developed for the Market Street Prototyping Festival (April 9-11, 2015. Market Street, San Francisco, CA)
It is my attempt to address the challenges that public sound art poses and to create an accessible, engaging musical experience.
This instructable will get somewhat specific about my process but I've tried to organize it in a way that is easy to understand. It's not necessarily a step by step guide into the minutia of replicating the project but a discussion of the main points of the system and what it took to get to a finished product. I have also tried to point out the places that could be easily modified and offer a few suggestions (based on hindsight and public feedback) for alternate builds. And of course, you will have your own ideas and needs, so apply them as you see fit. It's a pretty simple system but it is one that requires a fair amount of precision and skill in its construction. I'd put it somewhere between an intermediate and advanced level project. It requires access to plenty of space, some basic tools and an ability to use them well. It's also not rocket science and if I can do it so can you.
The project is entirely scalable and adaptable so have at it.
HERE is some documentation of what it looked like in process and in action.
Step 1: Choose Your Sounds
I used 2" galvanized pipe/electrical conduit for CHIME SF's sound source. I found this size to produce the most pleasing and suitable sounds. Anything that you can hit to make a sound can be used though.
You can make a set of chimes to any scale or set of notes you like. I wasn't looking to match the sounds of the space exactly. I was more interested in engaging in a musical dialogue with the environment. I chose the C major scale to accomplish this. The bells of the Ferry building and the trolley cars seemed to rest in the key of G and worked well with the key of C.
The C major scale is also built of the white keys on the piano keyboard. They are what I play when I sit at a piano. They always sound pretty good even when you mash around on them. I don’t know how to play piano so it works for me. The two modes of that key used for CHIME SF were Ionian and Lydian. I did some modeling in MAX to better understand how the system was going to work sonically. I've uploaded the patch I built if you're inclined to dig in to it. Each side was arranged so that it opposed the other side in intervals of fourths, this allowed a consistently resolving pattern to emerge and dissolve.
You can find online calculators for the lengths of pipe you wish to tune. Some rather kind people have already done a lot of work and collected the information you need to tune your own chimes. I prefer the bar length calculator at Experimental Musical Instruments. It works for pipe, tubing, and bar stock of any dimension. They are also a great resource for other experiments in tuning and musical instrument making.
I will leave the sounds to you because everyone’s ears and intentions in making music are different and based on personal and community preferences. Spend some time exploring the space you are considering putting a musical instrument like this before you commit to any one thing. I spent a lot of time on the street taking field recordings and getting to know Market Street.
It can be literally any set of notes you like. Don’t feel limited to a specific scale.
Step 2: Tuning Chimes
If you have decided on using metal pipe chimes this is when to tune them. I took care of tuning first because the chime lengths would inform the dimensions of the structure. When you have decided on your notes, cut the pipe a little longer than recommended. Longer pipes give lower notes and shorter pipes give you higher notes. Get yourself close and you can fine tune from there by grinding or filing material away to raise the pitch. You can always make things shorter and don’t believe anyone who tells you to get the pipe stretcher!
The tools you will most likely need are: Hack saw, abrasive wheel cut off saw or tubing cutter.
These are all good options for sizing your chimes. Clearly some require more effort than others.
The hack saw is the cheapest option and will require a lot of work to cut the tubing and to keep your cuts straight.
The cut off saw will be fast but noisy, more dangerous and expensive to buy if you don't already own or have access to one.
The tubing cutter is a manual tool but can be very precise and gives you clean cuts with minimal cleanup and waste but a lot of effort (I prefer it over the hack saw and for late night quiet work that you can actually do in your living room).
For fine tuning, I used a bench grinder, files and tubing reamer in conjunction with an electronic tuner. There are plenty of apps out there. I've found that strobe-soft by Peterson is very good.
The bench grinder can make quick work of removing external material but with tubing you will need to be careful to keep things even at the ends. It is easy to remove too much length with the bench grinder so take it in little steps.
The file will be a much slower (but more affordable) version of the grinder. Steady repetitive strokes across the opening will help you keep an even flat edge on your chimes. You will also be able to remove a lot of flashing (thin flaps of metal left from the cutting process) from the inside of the chime.
The reamer is easier to use when you have smaller sharp or jagged edges to smooth down. It will be slow going but your edges will remain more even. The thin, curly strips of metal you can produce with this tool are very nice too.
Step 3: Prepare Chimes for Hanging
Eventually, you will hang your chimes in the structure to make everything come alive. This means you will want to drill some holes in them to feed cable or cord through.
Drill press or drill/driver and drill bits.
I used a ¼” drill bit to make all the holes in the chimes. The smaller these holes are, the less material you will remove and the less you will alter the pitch when you drill the hole. You put these holes at a point 22.5% of the length of each individual chime. This is where the primary or fundamental node of the chime is located. It is the place where the material flexes at. When the chime is struck it has to vibrate. It wants to do so from the nodes. There are different nodes but for the clearest tone it is best to use the fundamental.
WARNING! After you have carefully tuned your chimes, you will drill this hole and the tuning will change. It is terribly unfair. You will have to go through all of them again and retune ever so slightly. Each chime will react a little differently but fairly regularly. Leave everything a little flat, drill just a little less than 22.5% and file away to get back to your desired pitches. When you drill this hole there are a couple of things you can do to make the process a little easier: make a V groove holder for the pipe. This keeps it from rolling around under the drill bit.
Use a center punch to mark your drill point.
It’s not a guarantee to prevent “walking”, but it does give your drill bit a place to land and begin the hole that’s not a curved surface. Don’t try to drill all the way through the tube from one side and surfac. Make each hole individually.
You will also want to file these holes down so that they don’t cut away at the hanging system. BeachsideHank has a good intractable on how to drill holes in round stock.
From here you should have a workable set of chimes tuned to your liking and ready for hanging!
Step 4: Building the Frame
I started with one frame. I recommend you do to.
Make sure the thing works before replicating a broken system. If you are replicating exactly, and are confident that this instructable is a sufficient enough guide, by all means be a factory and cut all your pieces at once. I’m a big fan of production lines. However, you probably have some tweaks and different/better ideas for your version. Test them out with the first section.
This frame had to be stable, modular and adaptable to different potential sites and surface grades. I wanted it to be explorable but understood quickly, for anyone to be able to use it and be able to pushed to an extreme without breaking. A basic “A” frame (truncated triangle or trapezoid frame) is your best bet. It is what I settled on after several iterations. It allows for stability at the base. It gives you a wide span for the hammer to swing in. It looks more interesting than a rectangle and it is easy to construct.
The frames for each section of the structure were built with 1" x 3" pine. I cut everything I needed for one section out of 6, 1" x 12" boards, 4 of which were common grade lumber and 2 were select grade for the lever panels . You will also need a big box of 1 1/4" screws, large eye bolts to hang the chimes and extra nuts and washers to fasten them to the frame.
This frame was constructed with two matching walls. Each wall of the frame is 36” at the base, 78” tall, 24” wide at the top. These walls are separated by 12” cross bars. Each frame is built so that it can be bolted to the next one.
I had to work within very tight quarters, in time, space and budget. Quadruple check every cut and lay the frame out as many times as necessary before assembly.
Deciding on the angle of the trapezoidal frame drove me crazy. Eventually I just had to pick an angle and run with it. It is a five degree cut again and again and again. At the scale of CHIME SF it was steep enough to make it interesting and gentle enough to make it inviting.
All of the joints for the frame of CHIME SF are just one piece of wood screwed flat to the other. This allowed me to work quickly and make changes on the fly if necessary.
If things were to get more permanent there would be some pretty fancy mortising going on not to mention those tenons and dowel pins!
I started with the longest upright pieces laid out on the floor then screwed on the top and bottom supports. Attaching the top one first sets the angle of the frame. There’s possibly a little slop in your alignment but the bottom bar will pull/push it in place. I kept the bottom bars up from the floor by a couple inches to account for uneven pavement, bricks, cables, grass, etc…
Use 2 screws per joint. Put them on a diagonal for a little extra stability.
The cross bar for the axle needs to be measured to the center and drill a hole for the pipe or rod you decide on. Repeat for the next side.
Attach the facing bars at top and bottom of one side then match to the opposite side.
I waited to get the first frame put together to see where the eye bolt chime hangers would go. Now is the time to install them. Measure your placement, drill the right sized holes for the bolts that you want to use and put everything in place.
You now have a free standing frame and it’s time to put all the fun stuff on.
Step 5: Swinging Things #1
The axles that I used were 5/8” steel tubes. I found a big box of them in a second hand store. They worked for the 3 days of the festival but they began to bend under the weight and force of the pendulum’s swinging. I would recommend a thicker walled tube or a steel rod of the same dimension. For serious robustness you should also consider using pillow blocks or at least some bronze bushings instead of just using the wooden frame with a hole in it for support.
There are 4 axles per section. the first connects each of the lever panels to the through arms on each side. The second connects the through arms to the hammer top in the middle. The third is the pivot for the hammer. The 3 that work as links are 8 ½” long. The pivot axle is 10 ½” long.
Revisit the guide on drilling round stock by BeachsideHank. The holes you drill in these tubes are for hitch pins to hold them in place. The placement of the holes can vary according to what you want. I found it best to get them close enough to the nearest wooden wall to keep them in place and allow for a little wobble.
Hitch pins were the easiest and most cost effective way to lock everything into place.
Step 6: Swinging Things #2
The hammer is built of 1” conduit and a 4” x 4” x 8” block of wood. A pine block was the most satisfying thing I found to hit the chimes with. Not too harsh, not too weak and heavy enough to make the pendulum swing with a good amount of force. Check in with the previously mentioned hole drilling instructable for this.
I cut the conduit at 50” and drilled a few holes at the top and bottom of each. I gave myself a few options as far as the swing of the hammer and the lever action that would produce the most rewarding energy investment and impact.
For the mallet, cut the 4" x 4" to 8" long. Mark the center line all around. Droll a 1 1/4" hole at the top with a spade or forstner bit for the pipe to run through. Drill a 5/16" hole through the side for the bolt to run through.
Assembly should be pretty straight forward.
Step 7: Lever Panels
While the curved panels are extremely appealing, they are an aesthetic choice. You can make any kind of panel you want. For instance: a flat board that can be upholstered or reinforced cardboard.
Here’s how I made the panels for CHIME SF though…and I'm sure there is a better way to do this.
6ft, 1”x12” pine boards (the good ones- they’re straighter and have a decent finish with little surface prep needed.)
2, ¾” dado slots 2” from either side.
Kerf cut perpendicular to the length at every half inch along slotted side. This allows it to bend just enough for the curve I wanted. To increase your efficiency, see the instructable about the table saw sled I built for this.
I also had to make a guide for the curved supports of these panels. This guide served as the master template for the curve of the façade of CHIME SF. My only advice is to eye ball it. I tried getting hyper precise and just made a bunch of shapes that didn’t look right. I was doing everything by hand anyways so why not draw the shape and sand it to where I wanted it? I used 1”x 4” boards for these supports. Cut all the curves as close to exact as I could with the jig saw then clamped pairs together to sand them as a matching set.
Take these along with the panel you just kerfed the heck out of and get ready for some work.
Sand down all the tear out and frayed edge stuff then dust everything off.
Have all the clamps in the world ready. The ¾” pipe clamps are your best bet. Plenty of torque and the bars are strong enough to take the pressure.
I made a bench specifically for this process.
You will also need a bunch of 2x4’s to spread the pressure across the surface of the panels as you clamp them down.
Lay the panel cut side up and apply glue to each lengthwise slot. Spread it out quickly then place the curved rails in each slot. They’re going to slip around and flop everywhere. Hold it together though because you have to flip the thing over as a whole onto the table top or bench. Continuing to work quickly, clamp the center/highest point and work your way to out alternating sides.
Each panel takes 24 hours to dry. Have something else lined up to do in the mean time.
When these things are done trim up the ends on a chop saw.
Once you have them clean and sized the same you can dress them up how you like. I chose to put a couple of curves in the sides for looks (for how it looks and for how it allows a user to look through it when it’s assembled.)
That’s all work for a jig saw and orbital sander.
Attach the hinges to the bottom of the panels then attach those to the frame.
Fold up the panel and insert the pivot axle along with the through arms. You have to start on one side then the other.
Step 8: Through Arms
Each section will require 2 arms to connect the lever panel to the hammer in the center of it all. For stability and looks I stayed with 1” stock and built a ladder type frame, 2”x 2” wide and 30” long. They needed to be very durable at the connecting points so I also made some custom hardware to attach them to the tubing axles. These plates were made from ¼” aluminum plate. I had the plate left over from another project and they look pretty great with the pine. You could certainly get away with something thinner, cheaper and easier to fabricate.
The plates are 2” x 4” with a ½” hole for the axle to run smoothly in. They also have holes to screw them on to the wooden part of the arms.
For alignment purposes, one side of the arms has plates mounted on the outside, and the other side has them mounted on the inside.
Step 9: Hang the Chimes
I’m real bad at knots. But my good friend Scott Watkins, who helped me design CHIME SF, came through with the right technique. Instructables is full of knot tying tricks if you need a hand and don't have access to Scott
I used nylon paracord to tie everything up with. It’s cheap and easily replaceable. If you file down the flashing on the holes to run the rope through it will last longer.
I used a thin piece of wire to act as a needle getting the cord threaded.
When hanging the chimes make sure they are aligned with the hammer. And make sure they will be hit in the best place. I have found that striking them at about 1/3 of the length worked very well. Play around with it though. You’ll hear what works for you.
In order to keep the chimes from swinging wildly and clanging against the structure, I added a loose loop tied from the frame around the bottom of the chime. This kept it in the right place while allowing it to swing and resonate without deadening its sound.
Step 10: Bolt Together
Does everything work?
No? time for some trouble shooting. Most of my problems came from misaligned components and slightly off angle glue ups, which I corrected in subsequent sections. Be precise in your initial fabrication processes and you take care of 95% of any problems down the line.
Yes? Great! Make 6 more and bolt them together.
For this I made spacers to prevent the lever panels from clipping each other as they moved back and forth. They are simple 3” squares cut from the 1” pine I was using for everything else. 24 pieces in all. 4 for each corner of each wall to wall connection. Drill a ½” hole in the center of each one and drill a corresponding hole in the walls of each section where you want to connect it.
I used 24, 3" x 5/16 bolts to make the connections for the entire structure.
Step 11: Roofing
I decided to build a roof for the structure due to the unpredictability of the weather in San Francisco and because it just needed it. The top, like most other choices you could make with a thing like CHIME SF, could be absolutely anything.
Corrugated tin was my material of choice. It's clean, regular, repetitive curves are very pleasing to look at. The metal matched the chimes and the other pieces of hardware in the structure and it is easy to work with. I used the 5 degree cut from the body of CHIME SF again in the roof. Keeping consistent details like this really do a lot to tie a well composed form together.
Describing it with words is engineering prowess that I don't possess so I'll hope to convey the process with photographs instead. Basically 4 triangular trusses. Again, using 1" x 3" pine for the stock, build the frame and back it with all of the support you can give it. I assembled the roof off of the form and then lifted it on. Space the trusses evenly so they meet up with good points on the frame and attach runners along the length at the top, middle and base of the roof. Then you can measure out your tin, cut it and attach. The best way to do that is to use self-drilling roofing screws. Make sure you have accounted for overlapping the tin sheets for best fit and to avoid gaps in your roof..
I used the mounting flanges to connect the roof to the frame. They are very handy! Make sure you get both the right and the left versions. Four of these will suffice, as long as it's not windy and you really cinch them down.
Step 12: Enjoy the Music
CHIME SF is built to respond to touch and provide feedback through sound and by its residual swinging motion. A simple push on one large wooden panel sets into motion a series of sounds, explorations of connectivity and smiles. The crowd responses were overwhelmingly positive. By being present with the instrument for the duration of the festival we saw first-hand the effects of the system. A surprising, albeit slightly expected, result of the street experience with CHIME SF was the clustering of participants. More people were more likely to stop and take part if there was one person already there. Crowds amassed in flocks and arrived and dispersed in steady streams. The motion of the festival’s crowds around the exhibition was very fluid. It became a temporary gathering space for people to connect, not only to the physical place but also to the idea that the place could be more engaging and that communities can form and strengthen around art and music.
I really look forward to seeing where the CHIME system goes next. It is such an adaptable instrument that is truly accessible across abilities.
Thanks to everyone who helped out with this project. I couldn't have done it without a ton of support.
Most importantly, Scott Watkins, who pushed me to take part in the festival process in the first place and made sure I had everything I needed for the project.
Everyone else on the CHIME SF team: Clare Hart-Slattery, Sally van Etten, Marvin Miller, Amanda Wysinger and Larry Woodland. Y'all are super for showing up for any and all of this.
Daniel Schmidt, and Laetitia Sonami for all their excellent questions and critical feedback.
John Bischoff, who gave me the tools to make the electronic version of CHIME.
Steve Parris and Julie Herndon for being real musicians and being patient with me while I asked stupid questions.
And Tristan Randall for being really hands off about the whole "Our design looks nothing like what we originally proposed" thing.