Boxy: Our kid-hauling cargo bike

By Christian

We're a 2-cargo-bike family (and now, also a tandem). We love them all. This quick post is about our electrified in-town kid-hauler (our Haul-a-Day remains fully "manual", like all our other bikes). Last year we put on a nice aftermarket motor system using parts from Grin, on our Madsen (aka "Boxy") and noticed (just before the start of the school year) that we put over 4,500km on it during its first year! Combined with the ~1000km Line spends bike-commuting and ~5800km I spend bike-commuting (used to be  ~9000km, but my work recently moved closer) this put us solidly into the "more km by bike than by car" category this year (not even including all the trips to the beach and bike-touring vacations). We anticipate more km this year, as the kid-drop-off-run is longer. Although we always biked a lot this upgrade let it entirely replace using an automobile (or the bus) for in-town trips in our family. The kids are protected from the elements, depending on traffic it's usually faster, you never have to worry about parking, and if you're super-tired you can always just use a bit more juice. Oh yeah, and of course it doesn't burn gas or even much electricity - the thing uses less power than we spend on cooking.

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Several years ago Line got a great deal on a very well used Madsen cargo bike that had, at some point, been retrofit with a tiny electric motor in the front wheel. The serial number indicated that it was one of the first they'd ever produced, and it took a lot of fixing up. We used it a lot, but as the kids got bigger it became less and less practical to pedal around town with 3 kids in the back and places to be. We decided to put a "real" electric system on it - the highest capacity battery Grin carried, a driver capable of putting out 40 A, and a large motor with "standard" (lower speed) windings - in our 20-inch rear wheel this means tons of torque, but the motor isn't really capable of pushing the bike much faster than 30km at our nominal battery voltage (52 V). This is fine for us - the rules say you shouldn't go faster anyway (and we don't want to), and we can take all 3 kids up the steepest of hills without issue.

Although Madsen does offer a kit we decided going with a system from Grin was better value because:

• We really wanted a hub drive (rather than mid-drive):
  • Regenerative braking gives better range, overall, even though there is some drag (and even if you start with a dead battery you get more from regen than you loose from drag).
  • Regenerative braking means using up less brake pads.
  • Way less wear-and-tear on the chain/cranks/cogs/freehub to have the power applied directly at the wheel.
  • Redundancy - you can still get around even with a drivetrain failure (ie - broken chain).
• I'm good at fixing stuff and integrating things, so didn't feel I needed a pre-fab kit.
• We could get a higher capacity battery.
• Nothing is proprietary - I can replace any of the components and mix-and-match as necessary in the future.
• The Grin charger is way better - I can program it to only charge the battery to 80% most of the time (more than enough for our day-to-day), thereby drastically extending its life, but charge it to 100% every once and a while for longer excursions like hiking trips on the North Shore.

Some other modifications include:

• Beefing up the kickstand, which was cracked when we got it, by welding on some web at the joints and extra "feet" so that it doesn't sink into soft terrain.
• Welding on a mounting rack for the battery.
• Front basket: a double-wide milk crate that I found adrift in the ocean and scraped all the barnacles off of.
• Making a large "convertible" rain cover for the cargo area and front basket. First attempt used outdoor table-cloth fabric and run-of-the-mill clear vinyl (best I could find locally), but the fabric wasn't UV resistant and the vinyl started to crack especially in the cold. After a few years I eventually replaced it with Marine-grade stuff ordered from JTS Outdoor fabrics. It's been 2 years since and it hasn't faded or cracked at all (they don't carry that particular fabric, but the clear vinyl was 20 gauge by Hercules and has been great so far).
• Lights, front and rear.

Anyway, we couldn't be happier with it. It's almost as much fun to ride with 3 kids in the back as my single-speed commuter.