Bikes and music are both amazing ways to experience community. Combining them takes the whole thing to a new level.
I've been creating bicycle sound systems since 2002. My friends and I use them for impromptu Halloween parades, Critical Mass rides, and smaller Cruiser Rides that I organize on RocktheBike.com
After building four different "Soul Cycle" party bikes, as I call them, I decided to go off the deep end and build my ultimate bike, to my highest, most exacting standards for visual details, sound quality, ease of use, features, and overall cosmic qualities. The Soul Cycle Chopper is now almost complete after 2-3 years of hard work. I'll be taking you through the overall process of making this bike at a fairly high level, and diving deeper into a few techniques that I think are cool or useful.
Step 1: Concept Phase.
Fill up your notebook, identifying which are the key features, thinking of the overall visual look. One of the key features I was going for with the Choprical Fish was a laid-back cruiser / chopper look that was still capable of carrying a powerful sound system and climbing hills.
Step 2: Design or Acquire Your Base Bike.
The Soul Cycle Chopper wasn't my first Soul Cycle, so I was able to compare the geometry to my previous one, the Soul Cycle ClassicSoul Cycle Classic.
I took a profile shot of my Xtracycle, and overlaid my drawing for the new chopper frame in Illustrator.
The major new feature of the Chopper frame is the dual seating position. It allows the rider to climb hills in a power position with full leg extension and then cruise in a chopper position, by employing a parallelogram seatpost system. The parallelogram keeps the seat flat when you 'drop and chop'.
I've seen many people use bicycle trailers as the way of carrying bike sound systems. It can be an easy way to get started, but there are some disadvantages to bike-trailer-based systems that I discuss on this blog entry.
I recommend a long-wheelbase load-carrying bike such as the XtracycleXtracycle or MundoMundo. They're designed to carry loads with ease, and they'll leave you room to carry a passenger.
Step 3: Prepare Full-scale Drawing of Frame for Welding.
If you don't have direct experience with designing bikes, I recommend copying the geometry on a bike you like riding, and making, perhaps minor changes to crucial elements like the head tube angle.
Step 4: Weld the Bicycle Frame.
Some people would say that this isn't a DIY project because I didn't do the welding. They may be right. My friends Ross and Adam have been talking about DIT projects -- "Do It Together." DIT is more fun than DIY because you have people to keep you positive and focused.
In any case, I can't offer too much wisdom about the welding phase except to say that it will take longer than you expect to do good work on a new bicycle design.
Step 5: Create Custom Seatpost System.
The Rock the Bike workshop is in a shared workshop community in Berkeley called the Tinker's Workshop. I raided my neighbors clamps for a few days to get the most thorough clamping job possible.
Step 6: Prototype the Sound System With Some Household Kool Herc Speakers.
I call these Kool Herc speakers, because they remind me of the ones that DJ Kool Herc used to roll around Brooklyn withroll around Brooklyn with back in the day when he was breaking hip hop.
Step 7: Design a Resonating Chamber.
On the Classic Soul Cycle, I had used a bazooka bass tube for bass. But on the Choprical Fish, I wanted all the lines to flow, so I needed to build the subwoofers into my cabinet. I used SketchUp to create an accurate scale model of my bike and design the speaker cabinet.
At this point in the process I didn't know how I was going to build the cabinet. So I thought it was important to do the design work in a 3D CAD program in case I would use CNC tools to fabricate it.
Had I known more about custom fiberglass fabrication, I wouldn't have spent so much time in this phase. I would have done more drawing and less CAD work, knowing that I was going to sculpt the form by hand anyway.
Step 8: Create a Positive Form for Fiberglass Layup
I made a sandwich of three large pieces of this foam. I cut the wheel profile out of the middle layer before gluing up the sandwich with polyurethane glue. The seams were difficult to work with during the sandind and shaping process. I would probably use 30:1 expanding foam next time. Doing so requires building a large box to contain the foam as it expands and hardens. Still, I think this might have been slightly better than using the household insulation foam.
I used a variety of wood shaping and sanding tools to reduce the crude shape to one I began to like more and more. I snapped lots of pictures so that I could compare it to my drawing.
Step 9: Create a Speaker Port in the Positive Form
At this point in my process, I didn't know the exact volume of my cabinet. I measured it later by filling it with styrofoam peanuts.
So I created a port that was longer than I needed it to be. Later I would cut it down. I created a foam plug (again, longer than I needed). I made sure the port and the plug matched perfectly.
Step 10: Create Translucent Side Panels and Mate Them With the Foam Shape.
I don't recommend working with the honeycomb because it's a very expensive material. Frosted acryllic panels would also be very beautiful when backlit properly. Or you could just use the fiberglass itself, which stays pretty translucent, and can be dyed with translucent color dyes. The advantage of using the fiberglass is that there is no mating process between side panels and the main form. The disadvantage, is that you would then have limited access to the inside of your cabinet unless you create a parting line. You'll have to reach through the woofer holes. Not a big problem if all the objects you're planning on putting inside your cabinet (amplifiers, lighting, etc.) are smaller than this hole.
Step 11: Create Subwoofer Retrorockets and Midrange 'eyes'.
Similarly the midrange 'eyes' increase the volume of the overall cabinet slightly and angle the sound forward. I like the eyes, because they play into the tropical fish theme of this cabinet. It's not a literal reference, but the end version of the cabinet looks a bit like a tropical fish. It fits with my mission of getting more people on bikes --> less global warming --> more coral reefs and tropical fish mission.
The process for creating the retrorockets was similar to the process of making the main form. I sculpted foam until I liked my shape and then glassed it. In this case I had some assistance from Wen, who was quite skillful wetting out the fiberglass.
Step 12: Mate Subwoofer Retrorockets With Side Panels.
Next I positioned it properly in the plane of the side panel, then tacked it in place with some 5 minute epoxy. Once it was tacked I created a very strong epoxy fillet on both sides of the side panel.
In order to create epoxy fillets you have to have an understanding of epoxy thickeners. If you don't use thickeners, the epoxy will run down your form like maple syrup. I used two thickeners on this project: cabosil and microspheres. Both are very lightweight powders. Cabosil is the better of the two for thickening epoxy to the consistency of vaseline or smooth peanut butter, while microspheres are better if you want more of a lightweight paste. They can also be used in combination, but I am still an intermediate/beginner at this and can't offer any rules of thumb.
In any case, I wanted a nice, glossy fillet was translucent, so I used cabosil to thicken the resin. I applied packing tape to my side panels beyond the glue line, to avoid smears.
Step 13: Create Midrange Enclosures.
Because of this, I needed to create cups for the midrange. Pretty much any size would do. But they do need to be rigid, just like the subwoofer enclosures.
I had never tried vacuum-bagging before, so I decided to try it for the midrange enclosures. The process is pretty basic. You lay up the fiberglass in the usual way. Then, while the glass is still wet, you wrap the form in saran wrap, followed by a layer of 'breather cloth', and finally and outer plastic bag that you then tape to your vacuum tube. I used a regular vacuum cleaner and used the port to reduce the strength of the vacuum.
The outer bag did indeed suck the curing fiberglass to the inner form, making a nice, strong midrange cup.
Step 14: Glass Main Cabinet and Install Speaker Port.
Step 15: Stiffen Flat Fiberglass Panels With Ribs
Step 16: Create 'flight Deck' Control Panel.
I decided to continue working with fiberglass for my 'flight deck.' I used the actual pair of handlebars to create a curved form that will clamp to the bars. Then I pecked, shaved, and whittled it away until I liked the shape. Then I glassed it.
Step 17: Integrate a Rechargeable Battery As a Power Source.
For previous Soul Cycles I've used Sealed Lead Acid batteries and NiMH batteries. For the Soul Cycle Chopper, I decided to go with the best battery available, Lithium.
The closest voltage to the devices I used was a 4-cell lithium pack producing 14.4 volts. Some of the devices I planned to run off the battery were really designed for 12 volts. So this means that in wiring up the system I needed to include a couple 7812 voltage regulator chips.
Choosing how large of a battery to use is a judgment call. Unfortunately, you really can't just use a formula, like multiplying your amplifier power by the number of hours you want to perform / ride. This would work for some devices, like lighting, that have a steady current draw. But for a music amplifier, the current draw fluctuates according to the music. So you have to go with estimates. I chose to use 7 x 4 cell packs. I run them all in parallel.
As you can see, I wanted the battery pack to fit in the empty space between the rear rack tubes. The music cabinet fits over the battery enclosure. So, you can separate these, to be able to service the battery.
Step 18: Wiring!
The big fat connectors are 8-way connectors from Neutrik. This means that with a single twist lock motion I am connecting 8 different wires to each other, and allowing 8 different circuits to function.
Why would you want to use connectors in the first place, let alone 8-way connectors? Because, presumably, you're going to want to remove your Soul Cycle from your bike at some point (perhaps each night after you've used it). Having a quick-disconnect capability that separates the controls from the main cabinet means you won't have to be walking with one big rats nest of wires. you can undo the connectors, coil the wires and lift the cabinet off the bike for storage or service.
Same with the batteries. It's nice to be able to charge them with a quick-connect charger.
The more complicated the system you're trying to build, the more crucial it is that you start on paper. I drew several drafts of the wiring system in my notebook before moving to full sized paper.
The wiring step also encompasses coming up with elegant ways to pass the wires into the music cabinet. By this point in my project, I was getting a strong tropical fish vibe from the cabinet shape. So I decided to accentuate it by passing the wires into the cabinet near the 'mouth' of the form to give it a whisker-like appearance.
Step 19: Create Cargo Racks
I also carry percussion instruments, spare microphone and cables, my laptop if I'm DJ'ing somewhere, a little food, something to drink, and a jacket in case it gets cold.
Step 20: Create a Passenger Seat With a Backrest.
I should note that using an Xtracycleas a base bike is the easiest way to add passenger capabilities to your Soul Cycle.
After mounting the bamboo cargo racks to the Soul Cycle, I carved a foam block into the shape of the passenger seat, then glassed it and mounted it to the racks using stainless steel hardware.
Step 21: Customize the Backrest With Your Electronics
The actual backrest surface is slightly curved, for lumbar support. The acryllic reveals the circuit boards behind it for a decorative look. During a performance, I'm able to plug a guitarist into the bike, hand a wired microphone to a backup vocalist, click a track on the iPod, and lay down lyrics over it using the wireless mic . The guitarist, backup singer, and I can all set our levels using the knobs of the mixer.
On my first soul cycle I used a two channel mixer. It allowed me toperform over the iPod perform over the iPod, but I didn't have the ability to bring in other performers.
If you do go through the trouble of purchasing expensive items like wireless microphones, don't stuff them in a bag somewhere. Design your bike so you'll be able to access them while cruising / performing.
Step 22: Design and Prototype a Beefy Dual Kickstand.
Of course, it would be easier if I only wanted the kickstand to function as a kickstand. But of course I wanted it to function as a passenger footrest also. This is especially challenging because it has to have both a locking 'up' position and a 'down' kickstand position.
Here are some of the prototyping stages that led to the current aluminum, water cut design.
Step 23: Build Center Kickstand
Step 24: Integrate Lighting.
I like to use CCFL lamps, similar to the one we use in the Down Low Glow. CCFL lamps provide a very even glow when compared to LED's. They're less energy efficient but not unacceptably so. I glue them into the inside of the music cabinet, and try to create beautiful color fades that are accentuated by the honeycomb side panel material.
Step 25: Sand and Smooth Fiberglass Surfaces Using a Gel Coat.
A gel coat is basically a thicked epoxy coat that includes no fiberglass. You paint or smear it on the fiberglass. Then 24 hours later, you sand it down. In my case I repeated this procedure 3 times. In the photo you can see that in a couple spots, I was sanding all the way through the gel coat to the fiberglass fibers. This is a no-no, since it means you are sacrificing strength. If you aren't happy with the curve yet, and you're sanding down to the fibers, you have to add more gel coat, then repeat the sanding process.
Most fiberglass products handle the gel coat a little different. Take a fiberglass boat, for example. Instead of laying up the fiberglass over a positive form, they would lay the fiberglass inside a negative mold. Before adding fiberglass, they'll paint in a gel coat. This way, once the glass hardens, they can pop it out of the mold. The gel coat, which was touching the inside of the mold is now the exterior surface.
In my case, the complexity of dealing with male - female molds, was greater than I wanted to take on for my one-off Soul Cycle. So I had to deal with sanding and gelcoating repeatedly.
Step 26: Get Your Friends Together and Go Cruising.
Here are some of my all time favorites:
Anything from Marvin Gaye funky years, including Sexual Healing, and Got to Give it Up.
Stevie Wonder, Innervisions album.
Curtis Mayfield, Move On Up.
DJ Sergio's House Mixes.
The entire The Harder They Come soundtrack
Bill Withers, Use Me.
David Bowie, Let's Dance.
Diggable Planets, Dial 7.
CIrque Du Soleil, Delirium Album.
Step 27: Host Human Powered Music Performances in Your Community.
Step 28: Human Power Your Party Bike!
Integrating Human Power wasn't on my radar screen when I started working on the Choprical Fish, my shopmate Nate and friend Gabe's enthusiasm was infectious.
I had my welder weld a pivot point for a motor that swings to hit the tire as it spins. This only happens when the bike is up on the beefy center stand.
A 23 farad ultracapacitor from Maxwell Technologies buffers the charge so that you can stop pedaling for a few seconds and not have the music and lights turn off. As you can see in the video, the battery system and the human power system are independent on this party bike.
When you integrate human power, you have to deal with the fact that the human pedaling the party bike can pedal too hard or too slow. If the pedal too slow, the amp and other devices will sound distorted or turn off. If they pedal too hard, you can risk ruining the ultracapacitor.
At the very least you need some kind of display that shows people what they're currently generating. Better still, you'd create a shunt that dumps excess voltage into a heat sink (fog blaster?)