Bike Safety


7
Apr 2014
by larry

Cargo Bikes’ Hidden Danger

(April 1st, 2014) As this video demonstrates, a longtail cargo bike has a hidden danger: poor backup visibility. Because a cargo bike is longer than a regular bike, there exists a “danger zone” behind the rear wheel where the rider’s view is blocked. This video shows my attempts to develop a “backup camera” to alleviate this problem, with limited success. My camera is similar to cameras recently mandated by the National Highway Traffic Safety Administration for all light vehicles.


18
Nov 2013
by larry

Winter Tips for Utility Bikers

IMG_2545

If you are like many utility bikers, especially if you replaced your car with an electric cargo bike, not biking in the winter is not an option. No matter what the weather conditions, you still need to bike to take your kids to school, commute to work, and pick up groceries. Is that even possible in the winter? The answer is emphatically yes. You’ll find a bike can get you where you need to go in any weather, in some ways more comfortably, more quickly and more safely than other forms of transportation. Sometimes it takes a bit of a sense of adventure to get going, but once you do you’ll find dread of winter biking is misplaced. Here’s some tips to help you along. Continue reading →


8
Oct 2013
by larry

A Simple Solution to Bicyclist vs. Motorist Conflict

Ebikes aren't just for weaklings. Ebikes carry passenger.

Ebikes aren’t just for weaklings. Ebikes carry passengers.

There is a simple solution to bicyclist/motorist conflict that needs to be more widely recognized: electric bikes. To a great extent conflicts are caused by the difference in relative speed between cars and bikes. Electric bikes can help more cyclists close that speed gap. Motorists easily become annoyed and even enraged when they see Continue reading →


22
Apr 2012
by don

Shawn’s Electric Yuba Mundo

 

The author giving his touring bike a break

Today’s article comes from a guest contributor, Shawn McCarty of Venice, Florida. Shawn is an avid cyclist who has completed bike tours through various parts of the United States and Europe. His blog (aworldspinning.com) has some nice photos of his European adventure. And his custom electric cargo bike is amazing!

If you have biking facts, photos, or a story you think our readers would enjoy, let us know. We’re interested in presenting a variety of topics and points of view as we build our biking community.

Continue reading →


27
Feb 2012
by larry

Should Humans Be Allowed to Drive?

Robotic Drivers Will Make Streets Safer for Bicyclists and Pedestrians

NPR had an interesting article this morning about robot-driven cars.  Apparently Google has had several of these vehicles on the road for years. Up until now they have taken a “don’t ask permission and apologize afterwards” approach. But recently Google hired a lobbyist who is promoting the idea that these vehicles should be allowed to have driver’s licenses. The idea is that while the robot is in training it will have a bright red license plate so that people know it is a “student driver”. And after it proves itself it will have a bright green license plate.

Many people may balk at the idea of robots on the road. My perspective as a bicyclist is this: the sooner the better. Nothing could be worse than human drivers. Here are a few reasons we should welcome the robots:

Continue reading →


21
Sep 2011
by larry

Friends Bike Clinic

“There is a spirit which I feel that delights to do no evil, nor to revenge any wrong, but delights to endure all things, in hope to enjoy its own in the end.”
-James Naylor’s deathbed testimony

I’ve been a bicyclist since I was a kid. As a middle-schooler I delivered newspapers from my bike. As a teenager I worked as a bike courier in Washington D.C. As a college student I biked from Portland to San Francisco on a three-week journey with my future wife. For me, bicycling is simply the most enjoyable way to travel.

Bicycling is also a way for me to care for the earth and to improve my community. In the last couple of years I’ve experimented with what the mainstream media calls a “car lite” lifestyle. I drive a large electrically-motorized bicycle that can easily carry a passenger and four bags of groceries up the steepest hills in Ithaca. In a typical month I put more miles on this bicycle than I do in the family car. I bike in all weather and in all seasons, and I make trips that are sometimes hundreds of miles long. I’ve found ways to almost completely (and comfortably!) replace our car with a bicycle.

I have a sense that others would like to bike more but don’t know how to get started. I’d like to share my experiences and learn about theirs. I’m setting up a project with Ithaca Monthly Meeting’s Earthcare Committee that I call the “Friends Free Bike Clinic”. Basically I will bring my tools to the meetinghouse deck and invite anyone to come by. We can work on our bikes together and share our knowledge about biking. Repairs could be as simple as a quick tune-up: cleaning a chain, pumping up tires, and adjusting brakes. Or they could be more involved: ordering and installing parts or even ordering whole bikes. In particular I encourage people to add electric motors to their bikes. I feel that an electric motor is a necessity for utility biking in Ithaca.

I plan to hold the bike clinic on fourth Sundays from 1pm to 3pm beginning September 25th (which also happens to be Porchfest, a neighborhood music festival). I invite complete novices as well as mechanically-minded people to join me.

-Larry Clarkberg


19
Sep 2010
by larry

How to Bike Long Distances on Your Electric Cargo Bike

I am on a bike trip to Washington DC.–I am hoping to do more and more of my long-distance travel by electric cargo bike. I’m getting pretty good at it. Many of you are probably wondering “How can I too make such journeys?”

The hardest part is justifying taking the time. Expect a bike trip to take four times as long as driving. Use whatever rationale works for you: you’re saving the environment, you like to experience nature firsthand, you want to get in shape, whatever. I’m driven to bike out of a sense that it’s the way things should be, a way to make our transportation system humane (see a previous post about my vision).

The next hardest part is responding to the objections and warnings of your family and friends. They will say things like “Why don’t you just drive like a normal person?” They will imagine that biking on a lonely bike trail at 15 mph is somehow more dangerous than driving in dense traffic at highway speeds. Furthermore, there is an insidious bias in our culture that bikes are for recreation and cars are for utilitarian purposes. Therefore, the thinking goes, if you are on a long bike trip you must be on vacation. And you shouldn’t be on vacation if you have to do the serious business of getting to somewhere. This thinking makes it impossible to consider the bike as a valid long-distance transportation tool.

I went on several long bike tours in my college days. Those trips were basically fun ordeals. Long-distance bike trips don’t have to be ordeals any more. What has changed? The two big innovations are smart phones and electric assist for bikes.

When I bike I have my smart phone in one hand to tell me where I am and a printout from Google maps in my other hand to tell me where to go. I would be lost (literally) without them. Here’s how it works. Before I go on my trip I visit Google Maps and enter my starting and ending points. I then click Google Maps’ “bike button” to choose a bike-friendly route. I then print out selected portions of the route. The print outs are good insurance that I can find my way even if I can’t get a mobile phone signal. When I’m actually on my trip I stop periodically and use my phone to make sure that my current location corresponds to a spot on my printout. The phone has another use: finding hotels and campgrounds. I don’t reserve hotels in advance since it’s hard to know where I’ll end up. So when I get near my destination I simply search on hotels or campgrounds within a five mile radius, pick one, and dial. I wish I had had that feature in 1988!

The last step to going on a bike trip is the easiest: physically moving the pedals around. Plan on going 80 to 100 miles a day. I know that sounds like a lot to those of you who are experienced bike tourists. But electric assist changes the bike touring game: you can go a little bit faster and farther, carry a bit more, and work less hard. I remember that when I went bike touring 20 years ago I could expect to go 50 miles a day at 10 miles an hour. I carried about 50 pounds of stuff. Hills just about killed me. Now I plan to go 80 to 100 miles a day at 15 miles an hour. I can carry 100 pounds. And with electric assist, hills don’t require much more effort than flats.

The main drawback to traveling on an electric cargo bike is that you have to find an outlet to plug into at the end of every day. For that reason I mostly stay in motels. Motels are cheaper than hotels with the added advantage that since the rooms are at ground level you can wheel your bike into your room. I also carry camping equipment so I can camp out if necessary.

I am hoping that by next year I will be able to recharge my batteries completely with solar power on long trips. On a previous trip I was able to gather about one eighth to one fourth of my power from the sun using bike-mounted solar panels.

What does the future hold? More bike paths? Better batteries and motors? Really smart smart phones? And a kinder gentler transportation system? Let’s not just wait and see, let’s make it happen.


28
Aug 2010
by don

Cargo bike brakes with kids on board

To avoid developing brake monomania, I’m promising myself that this will be my last post (at least for awhile) on the topic of cargo bike brakes.

But I noticed something interesting during my emergency braking tests yesterday: my bike had approximately the same stopping distance when carrying 180 pounds of cargo as it did with no cargo.  How could I explain the physics of that?

I think it’s because stopping performance depends on the friction generated between the tires and the pavement.  On an unloaded bike, the front tire does extra duty as the weight of the rider bears down on it – just like the front of a car dips down during hard braking.  In this scenario, the unloaded back tire can’t produce as much friction, and it’s easier to lock into a skid.

With 180 extra pounds over the rear wheel, the back tire carries more weight, and the job of slowing down the bike will be more equitably distributed between the two wheels.  The greater momentum of the extra weight just about matches the extra friction exerted by the back tire, and stopping distances remain about the same.

That was comforting to me until I realized that the bike’s center of gravity is also an important consideration.  I carried my heavy containers of water relatively low.  If I were carrying a passenger on the cargo deck, the center of gravity would be higher, and once again a lot of that weight would be loaded onto the front wheel during hard braking.  Stopping distance would probably lengthen.

Trying to stop on a downward slope would also increase the load on the front wheel.  For some combination of slope, speed, weight, center of gravity, brake type and condition, and road slickness, there will be safety issues.

Skidding

As my experience shows, things get dicey if your tires begin to skid.  A skidding rear tire isn’t too bad, except that it might indicate less-than-optimal weight distribution and diminished stopping power.  There’s also a slight loss of maneuverability; it’s easier to steer the bike if both wheels are rotating.

A skidding front tire is another story.  It’s nearly impossible to steer when your front tire is skidding.  If you try, the tire is likely to catch the pavement, at which point your handlebars will be wrenched from your hands or you will be removed from your seat.  The outcome of that situation is up to God’s mercy.

Moral of the story

The main thing that motivated me to write about this topic again is the realization that emergency stops with human cargo may be riskier than heavy loads with a lower center of gravity.  Especially if you’re carrying kids, you should practice a series of quick stops at progressively higher speeds until you find your comfort limit, and then you should stay below it.  Holding on during quick braking is good practice for your kids as well.

In addition, you should be extra, extra careful on hills or wet streets.

With kids on board, I am planning to reduce my speed and rethink my transport strategy in wet weather.


27
Aug 2010
by don

Cargo bike stopping distance

Regular readers of my blog know that I have been worried about cargo bike brakes for the past several months.  Yesterday my wife and kids left for a multi-day camping trip, and I decided this would be the perfect time to do some braking experiments with a loaded cargo bike.

In my mind, there are two kinds of braking I’m asking my bike to do: long, steady descents where I just need to keep my speed in check, and quick emergency stops.  I have a lot of experience with the former category – practically every weekday I pick up my kids from the school at the top of our hill and carry them down the steep slope.

On the other hand, I’ve only made a couple of emergency stops during the past year, so I haven’t been as confident in the ability of my brakes to stop a heavy load.  This morning before dawn, I loaded our mini-van with the bike and containers of water weighing a total of 180 pounds.  My destination was the parking lot behind the Seattle Museum of Flight.  I was looking for a long stretch of flat pavement that would allow me space to accelerate and skid to a stop.

And now I’ll cut to the chase.  When it comes to the Hammer Truck’s emergency stopping power, the big news is that there is no big news.  The bike stopped a combined weight of 420 pounds (180 pounds of water, 160 pounds of me, and 80 pounds of bike) travelling at 20 miles per hour, and it brought me to a complete halt in about the width of a parking space (less than 10 feet).  That wasn’t significantly longer than the stopping distance for the unloaded bike.  For that matter, it was on par with the stopping performance of our mini-van, and that’s comforting given the frequency I have to ride in mixed traffic.  However, I caught the unmistakable whiff of hot brakes and skidding rubber with the increased load.  The brakes were definitely working harder, even though they still felt solidly in control.

With considerable relief and bolstered confidence, I decided to repeat the experiment on a patch of wet pavement that had been moistened by the museum’s sprinklers.  That turned out to be a mistake.  The tires locked and I went into an uncontrolled skid, followed by an awkward low-speed crash.  I ended up on the ground, chain torn off the crank, and front wheel turned backwards.  Fortunately, neither bike nor rider was injured (but I was grateful there were no spectators at that hour of the morning).

This won’t come as a surprise to experienced cyclists.  Braking on wet pavement is a completely different story, and adding a heavy and somewhat badly-balanced load makes things even worse.  Perhaps I haven’t given slick pavement the caution it deserves during our damp Seattle winter – now I will.

How applicable are my results to cargo bikes in general?  My concerns about emergency braking have been mostly mitigated by these experiments, but with disc brakes on both wheels and the BionX motor assisting with regenerative braking, my bike is probably near the top of the class.  It’s possible that less favorable results would occur if you tried to stop a heavier load travelling faster with less capable brakes. Don’t let my unscientific results make you over-confident in your brakes.  I recommend doing your own experiments to give your equipment the opportunity to earn your trust.


10
Jul 2010
by don

Cargo bike brakes and safety

Yesterday I took my bike back to the bike shop to replace a brake rotor that was warped and making loud screeching sounds all the time.  For awhile, I tried to convince myself this was a great safety feature: everyone could hear me coming for at least a city block.  But the joy of riding in near-silence was missing, and dogs were more likely to bark as my bike squeaked by.

Disc rotors are prone to warp when they get too hot.  In most cases, my brakes stay relatively cool, because the BionX motor bears the brunt of braking.  There is a little magnetic sensor on my rear brake lever that engages the motor’s highest level of regeneration when I pull slightly on the lever.   Usually, the drag of regeneration is enough to keep my speed in check.  When the hill gets a little steeper (or the load is heavier), I apply my brakes in addition to the regenerating motor, but most of the time I use the brakes lightly and for short duration.

However, there is a problem.  If I sprint up our hill at maximum speed, there is some limitation in the battery or the motor which shuts off regeneration on the way down unless I wait for 10-15 minutes before I descend.  Perhaps something is getting too hot, although I haven’t noticed excessive heat in either the battery or the motor.  I called the motor manufacturer to ask if they were familiar with this situation, but the technical assistant who answered said regeneration shouldn’t turn off unless the battery is fully charged.  I am quite sure my battery is only partially charged when I lose regeneration.

Riding down our hill and carrying two kids (about 150 pounds total) without regeneration, my front and rear disc rotors get very hot.  Hot enough to leave scorch marks on the rotor, actually.

To be fair, this is a steep hill (12-18% grade for about 1/3 mile), and the total weight of the bike, rider, and cargo is around 350-400 pounds.  But the duration of braking is less than two minutes.  It’s hard to imagine a situation where I would worry about hot brakes after two minutes of braking with a car or motorcycle.  Are cargo bike brakes really up to the tasks we’re asking of them?

According to the owner of the bike shop, they are not.  Most cargo bikes come with disc brakes that were designed for single-rider bikes.  A beefy cargo bike carrying a heavy load could easily double the weight the brakes have to stop.  Add a motor and a battery, and you’ve not only increased the weight, but you’ve also increased the capacity to carry big loads up a hill.  What goes up must come down, and the brakes better be ready for it.  I haven’t done rigorous research on this topic, but it seems fairly obvious that the brakes need to be upgraded to handle bigger loads and higher speeds.

Unfortunately, this isn’t a problem that the biking industry has squarely addressed.  To absorb more heat, the mass of the disc rotor must increase.  My rotor is 6 inches in diameter and 2 millimeters thick.  Apparently, there is a company that makes a thicker rotor (3 mm), and that would help.  Instead, I decided to lay out $100 to buy an 8-inch rotor laser-cut from stainless steel (http://dirtydogmtb.com/designandsafety.htm).

The first problem we encountered was that my brake cable wasn’t long enough to move the brake caliper mechanism the extra inch or two to accommodate the bigger rotor.  In the process of replacing the cable, I upgraded to “compressionless housing.”  The idea is that very stiff housing transmits more of your braking force to the brake rather than deforming the conduit through which the brake cable moves.  I had already done this for the front brake on a previous visit to the bike shop, and I can tell a difference in braking responsiveness.  The new cable and housing cost $38 for parts.

Bar precludes repositioning of brake calipers

With the brake cable replaced and the rotor bolted on, all that remained was mounting the wheel.  That’s when we discovered that the Hammer Truck panniers are supported by a bar in the exact position where the brake calipers need to be for that 8-inch rotor.  The shop owner said we could crimp the bar to make room for the calipers, but I was concerned about compromising the integrity of the bike.  Also, the caliper adjustment wheel (red in this photo) would be inaccessible if it were nestled into the dent he was proposing to put in the bar.  (Click on photos to see them full-size.)

In the end, I decided to buy another 6-inch rotor.  It’s nice and true right now, and my bike is quiet again.  I’ve learned enough that I might be able to avoid warping this rotor.  First, I should allow more time to let the BionX motor cool, or I should climb the hill at a slower pace (and perhaps a lower assistance level).  With a little experimentation, I should be able to reduce motor/battery strain and avoid regeneration drop-out during my return trip.  Although it might take a little more time or effort, this strategy might even extend the life of the motor and battery.

Second, my daughter just graduated from elementary school.  Now I will have only one kid to carry down the hill in the afternoon, and that should reduce the braking load.  My immediate concerns over our safety have been reduced.

But my concern for other cargo bikers is escalating.  The electric cargo bikes that I have mentioned in earlier blog posts, Kona’s Electric Ute and Yuba’s elMundo, have no motor regeneration and only one disc brake in the rear (both bikes have a rim brake on the front wheel).  I’m concerned that this might not be adequate to stop a heavy load after a moderately long and steep descent.  It wouldn’t take more than a few mishaps to cause legal problems that could restrict the electric cargo bike market before it has a chance to develop.

Sometimes I try to convince myself that this is just an issue of setting expectations appropriately.  When we get really excited about the economic and environmental advantages of cargo biking, we talk about our bikes as being “car replacement vehicles.”  But it has been over a century since Ford’s Model T was first sold.  Since then, cars have benefited from continuous technological improvements and fierce competition between many different car companies.  The electric cargo bike has barely reached a comparable level of development to those first Model T’s.  Manufacturers are still treating the motor like an after-market option rather than an integrated design feature.

Arrows show exposed pressure plate

My safety concerns aren’t just limited to the brakes, by the way.  As the shop owner was re-installing my rear wheel after the rotor replacement, we got a good look at how the BionX motor mates with the Hammer Truck frame.  The critical interface is where the motor axle bolts onto the frame — the C-shaped flanges called “drop-outs.”  The owner pointed out that my drop-outs weren’t deep enough: at least one-third of the pressure plate that the drop-out should be holding is left dangling below (noted by arrows in this photo).  If you’ve been reading my blog for awhile, you might recall that I stripped a hub nut during the first month I owned the bike.  The results were catastrophic: the motor wiring was damaged beyond repair and a new motor had to be installed.  When the nut stripped, the rear wheel twisted a little and locked up against the brakes.  The bike went into a skid, but fortunately I wasn’t travelling very fast at the time.  Even though there were cars nearby, I managed to stay out of traffic, and escaped unscathed from the incident.

If I had been travelling a little faster, or if — God forbid! — I had my kids on the bike when that nut failed, it’s not pleasant to imagine what could have happened.  It seems obvious to me that this problem could have been avoided if the Hammer Truck had been designed with deeper drop-outs to accommodate the motor.  This is what I am looking for: a manufacturer that designs the bike, the motor, and the brakes to work together, rather than putting these pieces together and hoping their designs and capabilities mesh well.  So far I have not seen a bike that impresses me in this regard.  It feels like a classic chicken-and-egg problem: manufacturers won’t spend the time and energy to develop that bike until they see a significant market opportunity, but the market won’t grow quickly until there is a serious bike that people can see, test drive, and feel confident about its safety and reliability.

There are still some breakthroughs required in battery and motor technology (and price) that may be required to make electric cargo bikes attractive to the mass market.  However, those same advances will also benefit electric cars.  The market for an electric car is so much broader than electric cargo bikes — I think Americans are going to jump straight from gasoline-powered cars to electric cars, and cargo biking will remain a tiny niche of ultra-environmentalists and fitness freaks.

Of course, that’s only the most likely scenario.  A massive and sustained increase in energy prices would obviously benefit bikes of all kinds.  A generational shift of mindset is also possible and can’t be underestimated.  For example, if teen heart-throb Justin Bieber decided that cargo bikes were the only way to travel, who knows how fast cargo bikes could sell?  But at this point, most of the people reading my blog are more likely to be the parents of the Bieber generation.

I’m in a strange position.  For nearly a year, I’ve been riding my bike and enthusing over this method of cutting carbon emissions, burning some extra calories, and seeing more of your neighbors, nature, etc.  Now suddenly I’m worried about safety.  I’ve always known it’s a little risky competing with heavy metal boxes for a few feet at the edge of the road.  But if you’re not sure your equipment is fundamentally safe and sound, there’s another set of issues to worry about.

Do you think my concerns are overblown?  Does your cargo bike inspire confidence?  Let me know in the comments below!