Currently in the Clarkberg Bike Stable

Posted: December 9th, 2011 | Author: admin | Filed under: accessories, DIY, electric bikes, my life, shop talk, Xtracycles | No Comments »

Here’s a little photo essay about my family’s bicycles. I’m proud to say that we use our bikes a lot. Each bike is tailored to its user: I drive a cargo bike capable of carrying passengers and cargo long distances; my wife drives a slower and lighter but more stylish bike; my 11-year-old daughter Thea and her friend JJ drive bikes tailored to their 2-mile drive to school. (My son Jasper, aged 15, resists having a bike. He pretty much walks wherever he needs to go.) Ithaca is hilly, so it’s important for a utility bike to have an electric motor. I’ve spent a lot of time over the last couple of years experimenting with electric bike motors and other accessories. Maybe you can benefit from my discoveries.

: From left to right my bike, my wife’s bike, Thea’s bike, and JJ’s bike in front of our bike stable.

: My bike is a Surly Big Dummy Xtracycle with Stokemonkey motor, described in detail elsewhere. I named it “The Spirit of Ithaca”. I’ve changed so many parts it’s hard to give it a value, but you could probably get a comparable electric cargo bike for $3,000. Bicyclists may notice that my bike has an unusually large chainring. Last year I doubled the voltage of the motor from 36 to 72v, making my bike much more powerful—it can carry two adults up the steepest hills in Ithaca. Since by design the Stokemonkey motor moves the pedals, the increased power increased the speed of the pedals and it became necessary to increase the size of the chainrings to slow down the pedals.

: My bike is powered by two 36v10ah LiFePo4 batteries in series. They give my bike an enormous range of about 70 miles at 12mph or 35 miles at 20mph. However, each battery weighs 15 pounds and they are expensive at $600 each.

: My bike sports a DIY headlight I made out of about $50 in parts available at SparkFun.com. The headlight is powered by Grin Technology’s 12v voltage regulator which can take any ebike battery input from 24 to 72v and output the 12v required by the headlight. I’ve also used the 12v output to recharge my phone on long trips. The advantage of this centralized electrical system over a “regular” bike’s discrete lights is that I just have one switch to turn on all my lights and accessories, and I only have one battery and that battery is rechargeable.

: My DIY headlight has a homemade look that you just can’t buy at stores :-). I keep it on both night and day. It’s bright enough that I keep it pointed down and I run it at half power to avoid annoying people.

: Turns out my DIY headlight’s big heat sink is not necessary with the lower-power LED driver I’m using. I’m planning an updated version that uses the handlebars as a heat sink.

: My wife’s bike is a Sanyo Eneloop we purchased used for $1,500. She named it “Zippy”. The previous owner purchased it for over $2,000 from NYCE Wheels. (At 350 miles away, NYCE Wheels is the closest ebike store that I know of.) Zippy is a highly reliable bike compared to my bikes, which are constantly breaking down and in flux as I experiment with them. Besides the reliability, the most important feature for her is the chain guard which is necessary because she bikes to work in her nice work clothes.

: She has a rear rack but rarely uses it in favor of the faux-wicker front basket. The hub motor is in the front wheel and the rear human-powered hub has three speeds.

: Sanyo is a battery manufacturer and built the bike around their NiMH battery. The bike is surprisingly powerful and has a range of five to 10 miles. It’s not fast but it is so stately that you don’t feel like going fast when you are riding it.

: In practice bicycling can be a hassle because of all the little business you have to do when you get on and off your bike: put on your reflective bike jacket, put on your helmet, tuck in your pants cuffs, turn on the lights, unlock the bike, put up the kickstand, etc. That’s a lot to remember and it creates an unconscious impediment to biking, especially when you know that driving a car just requires opening the door, turning the key, and going. I got my wife this nice AXA wheel lock from Clever Cycles to reduce some of the hassle. Basically you press a lever and take out the key to lock the bike, and insert the key to go. No more fumbling with a cable or u-lock.

: Thea (left) and our neighbor JJ (right) used to walk a few blocks to elementary school but this fall they started at a middle school about 2 miles away. They were discouraged to find that the school bus takes 45 hot and stuffy minutes to get to school. The city bus only takes 15 minutes but costs $.75 and requires a 10-minute walk downtown. Biking, on the other hand, only takes 10 minutes! Thea already had an electric bike, and we equipped JJ’s bike with a motor too so she could keep up. I escorted them for the first few months and helped them work out a safe route.

: Thea has a nice lightweight mountain bike equipped for utility with a rack, kickstand, fenders, lights, and a front hub motor. It’s a kids bike with 24″ wheels, but I often ride it myself—it’s kinda sporty! The motor is powerful enough that I don’t need to pedal. In retrospect I should have installed a rear hub motor instead of a front hub motor. The front wheel spins out on hills. In general I’ve concluded that front hub motors are not suitable for Ithaca.

: I added Marathon Winter studded snows tires to Thea’s bike so that we can ride together safely this winter. I unequivocally insist than anyone who rides in the winter should use these tires.

: Thea’s motor is a Nine Continents direct drive hub kit from E-BikeKit.com for about $500. There are a lot of ebike kits out there but E-BikeKit is especially dedicated to excellent service. You’ll notice that I had to file off the “lawyer lips” around the dropouts in order to get the hub motor axle nuts to seat properly. Grin Cyclery’s excellent troubleshooting page tell s how omitting this step may lead to front fork failure.

: Originally I built a 15-pound lead-acid battery (described in a previous post) for Thea’s bike. This fall I began experimenting with lithium polymer (“lipo”) batteries, the same type of battery used by Radio Control enthusiasts. Not only are lipo batteries lightweight and inexpensive compared to my LiFePo4 and lead-acid batteries, they have a much higher discharge rate. This makes it possible to have a very small battery that can output enough amps to propel an ebike. So on Thea’s bike I replaced the three heavy 12v 10ah lead-acid batteries in series (a 36v battery) with two lightweight 18.5v 3ah lipos in series (for a 37v battery). Here’s the score: the lead-acid battery is 15 pounds, $100, 360wh, with a 36 mile range. The lipo battery is 2 pounds, $50, 108wh, with a 10 mile range. Which is better? It depends. My bike needs more range and weight is not a problem, so lipos are not a good option for me. But for Thea’s bike the lipo’s low weight is very appealing and their short range is not a problem.

: Thea’s controller and battery fit nicely in her trunk with room to spare for lunch.

: Thea and JJ’s bikes both use two 18.5v lipo batteries connected in series for a 37v battery pack. The RC charger, however, needs to charge them in parallel at 18.5v. I made special connectors to switch the batteries between serial and parallel, similar to the lead-acid battery connectors described in a previous post. In this photo the parallel connector is on the top connected to the battery and the serial is on the bottom in my hand. In addition to the power output connectors, lipo batteries have “balance” connectors to enable the charger to manage each cell individually. This photo shows a parallel balance connector I made so that I can charge a 37v battery from one charging port.

: Lipo batteries can be dangerous. I came across a post on one RC forum listing everyone on the forum who had had a house fire of some kind caused by lipo batteries. There were dozens of people on the list. That said, I haven’t had any problems with them myself. I try to be careful. I always balance charge my lipos. I make sure not to drain them below their limit. I charge them in a fire-proof bag as shown. That’s the charger on the left, capable of charging four batteries at a time.

: JJ has a small bmx bike with 20″ wheels and ornamental shock absorbers. I installed a $500 geared front hub motor from Ebike-kit.com.

: On a couple of occasions I’ve had the pleasure of driving JJ’s bike a few miles even though the seat barely comes up to my kneecaps. As with Thea’s bike, it’s a perfectly plausible form of transportation for an adult since I don’t have to actually pedal. The small wheels and the hub’s internal gearing give it incredible torque. And the small frame makes it fine for riding unobtrusively on the sidewalk, nobody minds. I once rode it a mile up State St. in Ithaca and it was sort of like going up the hill in an electric wheelchair.

: JJ’s battery and controller fit into a tiny seat pack. Can you believe it?

: I bought this high-end mountain bike (code-named “Black Beauty”) used for $400 with the intention of building it up as a replacement for my Big Dummy. So far I’ve added a hub motor and perhaps I’ll add an Xtracycle longtail extension in the spring.

: Black Beauty has very nice components, including hydraulic disc brakes and fully adjustable shock absorbers. I wasn’t looking for these but both of these features turned about to be important as described next.

: A couple of weeks ago I bought a $600 Crystalyte HS 3540 conversion kit from Grin Tech. I paired this state-of-the-art hub motor with a controller capable of handling almost 3kw (72 volts at 40 amps). (For comparison my Big Dummy typically runs at 1kw.) After a few technical difficulties I was able to put Black Beauty to the test. I found a quiet level stretch of road, pulled back the throttle, and let her unwind. She accelerated quickly to 40mph. At first it was frightening. Then it was exhilarating. But in the final analysis it’s embarrassing how fast this bike can go, since elsewhere I’ve blogged about the evils of speed. My main interest in building a high-powered bike is to make it capable of carrying adult passengers. Being able to go fast is an annoying side effect.

: Black Beauty sports a Cycle Analyst and an LED headlight, both from Grin Tech.

: For now I have Black Beauty’s battery and controller stuffed in a pannier. As you can see I’ve also outfitted Black Beauty for carrying vegetables.