Biking

toys , biking , health

Biking, is something that make my very happy. I have multiple bikes, here are my notes

My bikes

Folding Bike - The Brompton

A folding bike is great for reasonable distances because it’s easy to fold it up and carry it onto public transit, fold it up to bring it inside, or throw it into the trunk of a car. The most important criteria for me on folding bikes is ease of folding and folded dimensions. In this domain the Brompton is the winner hands down. If you have a Brompton check out my accouterments recommendations.

E-Cargo Bike - The kid carrier - Rad Wagon

Most cargo bikes are mid-drive, and expensive, and not that fun to ride. The Rad Wagon has a direct rear-drive which has the lowest possible torque, but it’s good enough for the flats and small hills and carrying your kid around.

Good parenting note, maximum speed and acceleration probably isn’t the goal when you have your most precious cargo on the back of your bike.

Link to Rad Wagon

E-Every Day Bike - Rad mini step through

The rad mini has a geared rear drive, which has solid acceleration, and decent efficiency and is incredibly fun to ride. Several notes:

  1. Get the step through, it doesn’t look as cool, but it’s always helpful to have your life be easier.
  2. Despite the name, it’s not a mini, it’s huge by bike standards. Just mini compared to Rad Power’s other giant e-bikes.
  3. Despite being a folding bike, it’s not portable or small folded down. At 75lbs you’re going to need a few people to lift it, but at least you can get it into a car with folded down seats which wouldn’t’ be possible with the other giant bikes.
  4. The engine makes a continuous “zipping” sound (due to the internal gearing). This “disturbs” the serenity of biking, and wouldn’t be present on a mid drive or a direct drive rear drive (but again the trade off is torque)

Link to Rad Mini

Bike accouterments

  • Light - I’d recommend a minimum of  600 lumens, and make sure it can charge over USB.   I currently use the urban 800.  I used to use the  Taz 1200, but it was too bulky, and I don’t need that many lumens
  • Locks - I like the Bordo folding locks, and u-locks, more coming.
  • Suspension seat posts - Took me a while to try these, they’re incredible.
  • Panniers - Orltieb - I couldn’t believe I spent 200$ on a set of saddle bags, but true story, I bought the 50$ kind, then the 100$ kind then finally these, and I’ve used them for 8 years without a single problem.
  • Ergo Grips - They’re great.
  • Hydraulic Disc Breaks - I don’t have them yet, but will soon.
  • Phone Holder - I don’t use it often, but so far no problems.

I’ve been through a few types of headphones:

  • AirPod Pro - I love them.
  • Aftershokz Air are bone conduction headphones that let you listen to music without blocking the street noise. Fantastic product, but I prefer the AirPod Pros

E-bike theory

E-bikes require some new concepts, here’s the results of my learning.

Mid vs Rear drive

There are multiple approaches to powering an e-bike: 1) have the motor spin the wheel directly, aka rear drive, or 2) have the motor simulate spinning the pedals aka mid drive. The big difference between rear and mid drive is a mid drive can use gears which solves torque, which we’ll get to in a second.

Even though the mid-drive can use your gears, it turns out gears and chains are designed to powered by humans, and if you stick a big motor into them the chains tend to break. As a result, unless you want to be doing on the road maintenance your mid-drive drive motor tends to be limited to 350 watts, about the power of having you augmented with an Olympic bike cycle racers.

By contrast rear motors don’t use your chain, so they can be more powerful, much more powerful. However, just like it’s really hard for you to get up a hill when pedaling, especially from a dead stop, it’s also really hard for your motor because of torque. The solution for humans is gears, which gives you mechanical advantage, e.g. the ability to require less torque but with the trade off that you don’t move as fast. Rear drives, because they don’t use gears, need to rely on you the human. Not quite as fun. Luckily there is a work around, stick a bigger motor (which is not limited by chain strength) in the back wheel, and give it more torque via internal fixed gears (effectively increasing your RPM, which trades acceleration for cruising speed efficiency).

(For completeness, though don’t do it Front wheel: The easiest setup and maintenance, the motor is in the front wheel. Because there are no cogs on the front wheel you can just pop off your old front wheel, pop on a new front wheel with a motor, and you’re done. The down side is there’s no weight on top of the front wheel so you have less traction and torque.)

Throttles and Pedal Assist

In a pedal assist motor, the motor is triggered by pedaling. With a throttle the motor is triggered with a thumb switch. If you can get it the throttle is super handy and more fun. Throttles are fun because you don’t’ need to pedal, and also very handy when stopped as it can take force to trigger the pedal assist if you’re in the wrong gear.

Why don’t all bike have Throttles? It turns out there are different classes of e-bikes (Class 1 vs Class 2), which are determined by if they have throttles, and their top speeds. The reason this matters is different areas have different rules for what class of e-bike can be on a sidewalk, and manufacturers serving those markets want the lowest (e.g. slowest) class of e-bike they can sell.

Torque vs Power vs Watts

Humans probably want to skip this section, but for my engineering friends here’s the skinny. I barely understand this, here are my deep engineering ramblings which I’d love an engineer to explain to me in simple but accurate terms.

You care about acceleration, which requires force (mass x acceleration). Force isn’t enough, you need to move something, which requires energy (force x distance). Which again isn’t enough, as you need to normalize for time which is power (force x distance)/time. Power is measured in watts. Power isn’t enough, as for a spinning motor, power is a function of rotational speed, e.g. RPM and torque. Power = Torque x RPM.

To make things more complex, Torque is a non-linear function of RPM (a motor property actually), and needs to be viewed on a power curve. At low RPM, e.g. when the wheel is moving slowly e.g. when going from a dead stop, or when due to a big hill, there isn’t enough power to get the wheel spinning quickly, you have low power output.

To make things more complex, there is input electrical power, volts x amps, and then output power, which is effective force + wasted heat force. If you can’t get the wheel to spin, you may have 100% input power, but 0% output effective power.

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