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How to make an off-road scraper bike with a badass sound system

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I’d been dreaming about creating a badass sound system for a mountain bike ever since I learned about the scraper bikes that prowl the streets of Oakland, California, adorned with custom, high-wattage stereos. Setting my sights for an annual, underground mountain bike event, I dove into my dank basement workshop, armed with a pile of “leftover” stereo components and a conceptual plan.

After some trial and error – and a trip to the hardware store – I reemerged with a badass scraper bike that was worthy of the “Super Karl” persona that I planned to adopt for the event. I’m proud to say that the “Super Karl Sound System” bike not only survived the muddy, rugged ordeal, but also brought smiles to many faces. Afterwards, I decided to photograph and document the construction details, which I share below.

Something more compact would have been optimal, but the big-ass, 200-watt car amp shown below is what I had “kicking around.” The car amp mounted to a base board, which would then be mounted to the bike’s rack.

The amp’s considerable heft called for sturdy mounting brackets. I found some old seat belt brackets that I attached to bike rack. When you don’t have access to genuine Saskatchewan seal-skin bindings, you have to improvise.

The photo below shows how the amp/board assembly connected to the rack via the brackets.

Front view of the amp/board assembly attached to the rack brackets:

This BluBridge (Bluetooth audio receiver) connected to amp’s “audio-in” jack. The BluBridge wirelessly synced to my iPhone’s audio-out.

With the iPhone tucked into a handlebar-mounted Topeak DryBag, I could control music remotely while riding!

I scavenged mounting clips from a set of panniers and attached them to the backside of a pair of vintage Realistic speakers. Oh yeah!

The speakers clipped right onto the rear rack. I used quick-connect plugs on the speaker wires, for easy on/off.

Power was supplied by standard 12-volt water bottle battery that was designed for lighting systems. I soldered a compatible plug onto the amp’s “power-in” wires.

The cover that protected the amp from the elements was fabricated from a clothes dryer vent tube that I purchased at the home store. Since the Super Karl Sound System was as much a rolling art installation as it was a music source, I decorated it to match my “Super Karl” costume.

Here’s a detail shot of the underside of the cover, fabricated from a dryer vent tube, aluminum cap and hose clamp.

I bolted the snazzy cover on top of the amp for protection, figuring that it looked enough like a rocket-powered bike to fit my theme for the day.

The next steps: go riding, play music, have fun. Mission accomplished!

Click the video below to see and hear the Super Karl Sound System making it’s grand entrance on the big day of the event. A real crowd pleaser.

Finally, a tip of the helmet to my muse, Super Dave Osborne: