Billy the Boombox (Custom Music Bike Trailer)

Our fellow bicycle trailer enthusiast, Ryan Cooper, contacted us about a custom music bike trailer that he cooked up. We decided to post up his words and photos about his project. Also, check out another music trailer we reviewed.

The Origin of The Project:

“The local Critical Mass group completed their May ride and pedaled over to a local, bike-friendly watering hole for post-ride refreshments. As we sat on the patio, the discussion of music for the rides was brought up. My background includes work with car stereo systems and I felt that a car stereo modified for use on a bicycle would offer superior performance to the small, battery powered boom boxes we had previously used. After some discussion about how to make it work, I decided to give it a try.”

Custom Music Bike Trailer

Technical Requirements:

“There are a few things to consider when building a car stereo without the car- First, car stereos are terribly inefficient when it comes to power consumption. Cars use alternators to provide a constant source of power. Using only a battery would require some self restraint with wattage and volume levels. Next is the batteries themselves. Car batteries are quite literally filled with lead and they weigh between 25 and 55lbs! Finally, where to put all this stuff? I decided a trailer would be the best solution because it would allow me to keep the weight low and provide space for all the components.”

Let the Building Begin (The Stereo):

“First I had to design the stereo system. I had an old 2 channel car audio amp laying around the garage. I purchased some 6.5″ speakers from Wal-Mart. They are not fancy but I they do the trick. I also got some wires and a switch to use as an amp turn on. A fellow Critical Mass rider contributed a car battery. She also provided use of her iPod. With the stereo designed, it was time to start thinking about trailers.”

Bike Trailer Stereo DiagramBuilding Continued (The Trailer):

“A local rider learned about the project through a bike forum and donated a commercial kiddie-trailer arm for use. This was awesome because the attachment point is the hardest thing to ‘make’ in my garage. The trailer was built with a plywood base with wood and fiberglass reinforcement. The wheels are ball-bearing utility cart wheels mounted with custom steel axles that I welded on. The “body” of the trailer is made of polyester impregnated fleece stretched over MDF and welded steel forms. It is hard like plastic and works really well for this type application.”

Additional Thoughts:

“My total build cost was about $300. If someone wanted to replicate this trailer exactly the cost would likely be much higher because I did not factor in parts and supplies I already had at my home or the specialized skills such as welding and composites fabrication that I used. This trailer, as cool as it is, was really a proof-of-concept for me and in the future I would like to build version 2.0 including a deep cycle battery for improved play times, an integrated FM tuner so the iPod could control the stereo from a handlebar mount, and I’d use a 3 or 4 channel amp and a subwoofer to improve bass response.”

Trailer Stats:

Name: Billy the Boombox
Manufacterer: Ryan Cooper email: Ryan{at}thecooperproject{dawt}com
Build cost: apx. $300
Weight: apx. 50lbs. with the battery installed
Sound System: iPod head unit drives a 75watts x 2ch amp pushing 6.5″ three-way speakers.
Runtime: 3+ hours under normal playing conditions [depends on volume and gain settings]

In Conclusion:

“The trailer was a huge success. It was pulled at the June Critical Mass ride and met with a fantastic reception from participants and onlookers alike. It was used again for a patriotic-themed ride on July 4th where it again exceeded my wildest expectations.”

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0 thoughts on “Billy the Boombox (Custom Music Bike Trailer)”

  1. Trey says:


    How did you wire the stereo?

    I have an old cassette head unit in my garage
    that I’d love to turn into a boombox but I have no idea how to connect to all the weird outlets on the back.


  2. Tim Brennan says:

    Cool build. I just wired my bike up with some crappy computer speakers and I power them off the wheel (proof of concept, gonna add a car stereo soon) but anyway, you should recharge the battery on that sucker of your wheels. All I used is a wheel dynamo like the kind in old school light kits. That gives me like 20+v AC, then I run it through a bridge rectifier to convert it to DC and then a voltage regulator to keep it at 12v so I don’t burn everything out. For now I just have a 9v recharchable on their to keep my lights on when I stop pedaling but am gonna ad a 12v drill battery so I can keep the tunes going when I stop.

    If you wanna try and need any help e-mail me and I can send you a circuit diagram.

    – Tim

  3. Ryan says:

    I’d be glad to help you with the wiring but I’m not sure what kind of tape deck you have (I assume you mean a factory-installed car tape player?) Hit me up at Ryan[at]thecooperproject[dawt]com with specifics about what you’ve got and I should be able to tell you how to wire it up. Most car head units have a built in amp so it should be a pretty easy hook up once I figure out what you are working with.

    I believe I may have seen some of your work at I appreciate the offer of circuit plans but a bike powered dynamo will not be able to provide enough current to make a meaningful difference in the ammount of time the stereo can play. The dynamo can run your computer speakers because they likely run on about 1watt of power. Even low-end car speakers need 5+watts to opperate loud enough to hear them. The speakers used here (with the external amp) are running about 60 watts each. I doubt you will be able to run car speakers from a dynamo at all but if you do they will be very quiet. Your best bet for a dynamo powered system is chopping up one of those battery powered iPod speaker systems and converting it to run off dynamo power. You won’t hear it a block away like this system but you won’t be hauling 40lbs of lead (battery) around when you ride either.

    If you want to discuss what I mean about the current requirements of these stereo systems at greater length feel free to email me at the address I posted above.

    Pedal on,
    -Ryan Cooper

  4. Jim says:

    I’m on an ultimate frisbee team and we need some tunes blastin at tournaments… I want to build something just like what you have but i have some questions.
    Other than the car amp and speakers, what other parts should i start looking at to purchase? Also, the battery lasts about 3 hours? If i reduce the size of the speakers do you think i can save some energy? Also, when the battery is dead do you charge it or pay up for a new one.

    thanks for any help,

  5. tim matlock says:

    im wanting to put a box on a wagon to pull to softball tournament.will this setup work if so can you send me the info on how you wired it up.Thanks Tim

  6. Jonny Orozco says:

    I want to make something very similar to that but a little more small scaled. I have a 240 watt car amplifier and a 12 volt battery to power it but I do not know how to wire everything. The amplifier came with all the power cables and audio cables included but I do not know how to connect the battery to the amp(everything else is solid.) I would assume it would be the same as how you wired your system but with a smaller amp and smaller battery. Can you help me?

  7. Julio says:


    I am involved in planning a ride and I’m in charge of music. I would like to create a system similar to yours. What I have so far is a trailer that someone is going to loan us, a 10′ Sony Xplod Subwofer and an old car battery that my mechanic said has 10 watts left.

    Do you think that I can use the Sub by itself and get some good sound?

    What kind of amp should I get, how many watts?


  8. Polo says:

    Im am in the process of working on the same project. My setup is a little diffrent, I have a 6.5 Boston Acoustics Sub and 4 satelite speakers, 200w amp, and 1 car battery.

    My question to you is, How long did your system run for before you needed to recharge it? I am trying to guess on how long I will have to enjoy music on the go.


  9. […] has information about this monstrous system and other bike Frankenstein like bike music projects at his link page. Share and […]

  10. Francisco Castillo says:

    I can help . modify or build cargo system for bikes.

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