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.
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.
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.
Finally! It has been months – even years – since rumors of an electrically-assisted Ute cargo bike first surfaced on the web. Kona recently posted its 2011 catalog online, and there it was: the Electric Ute in all its beauty. At $2599, Kona has allowed the Yuba elMundo to keep its low-price crown ($2297 including tax and shipping). However, the Ute and the elMundo are such different bikes, price should be among the last factors to consider if you’re choosing between them. There have also been changes in the elMundo since I last wrote about it, so there are good reasons to take another look at both these bikes.
Kona Electric Ute
Despite its workman-like name, the Ute gets my nomination for most beautiful cargo bike. Kona has paid attention to the details, and the electronics are nicely integrated. The Ute approaches my ideal of a bike and motor that were designed together. Unfortunately, Kona’s marketing is a little coy about what their design target really is. For example, the website introduces the Ute with this sentence: “The Electric Ute is a battery-assisted version of our very popular Ute, a long wheel base bicycle designed to carry loads of up to 100kg-perfect for transporting goods in the urban environment.” [their emphasis]
This might be an accurate statement in a superficial sense, but it deserves some careful disection. If you live in an urban environment that is relatively flat, and if you can fit your load into the comparatively small Ute side bag, the Ute will be perfect for you. On the other hand, if you manage to load 100kg (over 200 pounds) of cargo on the bike (that might require some creativity), you’ll find the motor is not powerful enough to help much on even moderate inclines. During my test drive (see my in-depth review here), the motor shut down while climbing a short, steep hill of about 15% grade – no load, medium assistance level. At first, I thought the failure was a battery issue, but now I’m pretty sure the controller was temporarily disabling the motor to prevent overheating. If you live in Seattle or San Francisco, you may have to pedal up the steep hills without assistance from the motor, just when you want it the most. I also have concerns about the ability of the front rim brake and rear disc brake to safely stop a heavy load in an emergency.
Kona’s description of the Ute ends with this: “Serious power for carrying heavier loads. Ditch the truck, people.”
I’m not a marketer (and thankful for that), but is it really necessary to hype the bike past the point of reasonable expectations? I mean, the Ute is a great bike for commuters who have some extra stuff to carry. It feels more like a normal bike than its bigger and heavier competitors. Maybe those facts aren’t sexy enough for the marketing department, but this is a bike that could satisfy many customers. The big question is how it will compare to Trek’s bike which will be released late this fall. I’ll talk about that shortly.
The elMundo has quietly undergone some changes since I corresponded with a company representative in late spring (here). The only clue that the bike has had another transformation is the addition of “v3.0” to the bike’s name. Photos on the website have not been updated.
Yuba has ditched its 750W motor from Aoetema and now uses a 500W motor from eZee instead. The fact that Yuba mentions the brand of the motor on its website is progress, but I still have a question. The only motor I know of from eZee is rated for 400 watts nominally, and about 800 watts peak. Is the 500W figure quoted by Yuba fudging a little? Not that I’m focused exclusively on the wattage of the motor: even at 400W, the geared eZee motor might deliver more power when it’s needed than the Aoetema motor. But the effort to be scrupulously accurate on these specs would be a welcome development in the cargo bike market.
I would love to know what inspired the motor change, but I have a couple of guesses. First, the eZee motor uses internal planetary gears, which should help deliver higher torque at low speeds for climbing hills. The elMundo is a big, heavy bike (due to its high-tension steel frame), and it really needs a high-torque motor. Yuba is also calling attention to the disc brake mount on the motor. Although the standard elMundo comes with a rim brake on the front wheel and a disc brake on the rear, I would encourage anyone who intends to descend hills with a loaded elMundo to invest in a front disc brake.
Interestingly, Yuba has removed any mention of cargo weight capacity from its descriptions of both the Mundo and elMundo. The company previously claimed an absurd figure of 400 pounds, plus rider. Although the frame may be able to handle that, it was hard for me to imagine the brakes (and perhaps the tires) would be capable of stopping that load in a reasonable distance. If my complaints helped motivate this change, I am pleased.
As before, I must add a huge caveat to my descriptions of the elMundo. Although I’ve read blogs and emails from people who are very happy with their Mundo bikes, I’ve never ridden one or even seen the bike in person. The scarcity of Yuba dealers in my area makes that challenging.
The elMundo is also likely to have a competitor in the upcoming Trek bike, so I’ll move on to that.
The entry of bicycle behemoth Trek into the electric cargo bike market is huge news. Trek’s annual sales are at least 100 times those of Kona, and I couldn’t even find sales figures for Yuba. If Trek decides to put any weight into the marketing and support of their bike, other cargo bike manufacturers are likely to become asterisks in the margins, at least in the U.S. for the next couple of years. Besides my bike, I’ve never seen an electric cargo bike being ridden in my city. At this point, I’ll bet the first one I see will be a Trek.
With an MSRP of $2679, the Transport+ has the Ute squarely in its sights. Like the Ute, the Transport+ includes a bunch of accessories at the base price: folding rear load racks, front rack, Bontrager Transport cargo bag, fender, wide-stance kickstand, front and rear lights. With the front rack, rear side racks, and bigger cargo bag, the Transport+ appears to be more serious about hauling cargo than the Ute.
These features alone could justify the extra $80 for the Transport+, but Trek’s choice of motor is an even more compelling reason. It comes with a beefier 350W motor which is essentially the same direct drive BionX motor I have on my bike. This motor offers superior load-carrying and hill-climbing capabilities compared to the Ute. It is quieter, the pedal activation system works a little more smoothly (in my opinion), and it offers regenerative braking which takes some of the load off your brakes. The advantage of direct drive (as opposed to planetary gears) is that the BionX motor is very, very quiet. The downside, as I’ve mentioned in earlier posts, is that motor assistance starts to fade at speeds below 6 mph, and this can be a challenge when hauling a heavy load up a steep hill.
BionX has incorporated additional features since I bought mine a year ago. When you turn the console light on, the lights in the front and rear of the bike turn on too, powered by the same battery. On my bike, I have to flip at least 4 switches to turn lights on and off, and I have to keep all those separate batteries refreshed. This is a welcome advance!
Trek explains their “Ride+” motor technology in a series of videos available here. One of the videos mentions a 250W motor, but that’s a less powerful version than the one Trek is using for the Transport+.
Another feature I like about the BionX system is the integrated battery/controller. If you compare the photos of the Ute and the Transport+, you’ll see the latter doesn’t need the extra black box mounted near the cranks on the Ute. The console for the BionX also gives better feedback about the level of assistance requested and received from the motor.
It’s always easy to get excited about a bike when it’s merely a photo and a set of specs, so I’m trying to temper my enthusiasm for the Transport+ until I can actually ride one. There are still opportunities for Trek to misstep. But with an attractive bike, good technology, a large dealer network, and marketing muscle, it seems like this is Trek’s game to lose. But we’ll all be winners if this bike helps bring cargo biking into the mainstream.
Big year for cargo bikes
A year ago I was shopping for an electric-assisted cargo bike. None were available pre-built from a manufacturer. The state of the art was an XtraCycle like the Surly Big Dummy driven by a Stoke Monkey, but it wasn’t easy finding a bike shop that wanted to build one for me.
Today we have ready-made electric bikes from two manufacturers, and the biggest U.S. bicycle company is about to enter the market. I’ve been riding my bike almost daily for 11 months. There have been few problems and virtually no close encounters with cars. My blog receives over 1,000 unique visitors per month from all parts of the world (but mostly U.S. and Canada), indicating an encouraging level of interest in this transportation alternative.
Sometimes the pace of change seems slow, but looking back, a lot has happened this year. I wonder where we’ll be next year about this time?
I recently received the following email from a reader:
I was researching cargo bikes and just kept seeing your blog pop up. I am very interested in doing a similar set up as yours. I also was interested in elMundo initially. A sidenote on the weight of the elMundo: they are now selling it with the electric components already attached and the shipping weight of the bike and box was 100 lbs. which seemed like a lot.
My question is pretty simple. I haven’t tested a Rans Hammer Truck in person since this is just the planning phase. I read the height of the bike had a 31- 38 inseam. I am 5’5″. I wondered about the comfort of the frame. And if your wife was shorter than you and found the Hammer Truck comfortable… ? Also just to pick your brain (and thank you very much in advance) how did you like the Hammer Truck handling without the electric assist? You mentioned you test rode it for a day…
My plans are just like yours, I want to use it to take my 2 kids to school and errands and fun – reduce car use in general. The kids are 6 and 4 and the bike trailer is just not cutting it these days.
Oh yeah! one more question. I read your post worrying about brakes. Currently with the bike trailer I often hop off and just walk up the hills. My question is, is a cargo bike easy to walk with when it’s carrying about 50- 60 lbs.? Or very tippy?
Thanks for the blog. I am surprised the Yuba people haven’t offered to let you test drive their bike. Surfing I ran across another cargo biker’s blog who actually bumped into the founder/owner while on a bike tour in Europe and had a very good impression of him and a good talk with him.
Thanks again. Happy biking! I am so happy I stumbled across your blog.
Thank you, Jessamin. Your email reminded me that there are still a few things I can say about the Hammer Truck. For many months, I have felt a bit uncomfortable about my bike’s relatively high cost, and I have been researching less expensive bikes that might appeal to a broader market. That has been an interesting project, and I intend to continue doing it for a while. But I don’t own these bikes or ride them on a daily basis. My real expertise is my particular bike, and answering your questions gives me an opportunity to return to familiar territory.
To answer your question about bike height, my wife rides the Hammer Truck very comfortably. At 5’4″, she is a little shorter than you. As you can see in this photo, the seat stem for the Hammer Truck is angled at approximately 45 degrees. When you lower the seat an inch, you also get an inch closer to the handle bars. This seems to scale well for most body types.
While you’re looking at the seat, I will also mention that the inclination of the seat is adjustable. When I first started riding the Hammer Truck, I had the seat almost parallel to the ground, like a normal bike. However, the Rans web site shows their seats tipped forward, so I tried it. It feels a bit like standing and leaning against a wall. Tipping the seat puts a little more weight on your feet, and that’s what you want when you’re riding. The slight curve of the seat back allows you to dig in for a little extra leverage when you need it. These are all helpful when you really need to crank!
The Hammer Truck worked fine without the motor. If we still lived in Denmark where it’s notoriously flat, I wouldn’t have needed the electric assistance. I’ve spent so much time on this blog bemoaning the hills in our neighborhood, I decided I really needed to show you what I mean. Yesterday afternoon, I put my 9-year old son behind the camera, and he took a video of me pushing my daughter up the hill, riding without assistance, and riding with the motor providing maximum assistance.
As you will see, this hill is a monster. When I write about heating issues with my motor and brakes, you need to understand that I’m pushing both to a limit that most people won’t encounter. Despite my occasional complaints, it’s pretty amazing that this bike can handle this kind of challenge. (Note: the scraping noises heard in the video aren’t the bike — my son was balancing the camera on a mailbox to keep it level, and scraping as he pivoted the camera.)
You can also see from the video, pushing the bike uphill is possible, but not fun. The side bars that carry loads so well are approximately where you want to put your feet, so you have to lean over a little. It might be hard to see in the video because I’m already leaning against the hill so much. It’s not as tippy as I thought as long as both hands are on the handlebar. It would be almost impossible to do one-handed.
You might notice my slightly hunched posture when I’m riding in this video. With the Hammer Truck, you generate power by pulling back on the handlebars, engaging the same muscles you would for rowing. In my case, I can produce more cranking force this way than I would standing on my pedals on a traditional bike. It’s more of a full-body workout, especially when I turn the motor off. However, this might not be a good idea for people with fragile knees.
Speaking of cargo bikes on hills, this is probably a good place to mention one of my favorite web pages: Cargo Weight Calculator. The calculator which gives you a rough idea about how much weight you can expect to haul up hills of varying steepness. Another page on the same site shows you how to measure the grade of a hill. Every time I turn off my motor and I’m reminded how hard it is to climb a hill with a load, I return to this web site, punch in the numbers, and I’m assured that there are real, mathematical reasons why it’s difficult. It’s not because my motor is making me lazy. 🙂
Sometimes I get distracted by all the details of this project: the specifications, the prices, the compromises. My blog is kind of heavy on that sort of thing. I occasionally need to remember that there is an emotional and even inspirational side to cargo biking, and my favorite blend of practicality and inspiration comes from the Couch Potato to Full-Time Cyclist blog. If you haven’t seen it, check it out — it’s really a great counterpoint to what you read here.
Hi. My name is Don, and I write a blog about electrically-assisted cargo bikes. Although I’m pleased with the performance of my Rans Hammer Truck and BionX motor, many of my readers are interested in less expensive alternatives. The Yuba elMundo and Kona Electric Ute are two possibilities I’ve mentioned in my blog. Unfortunately, there isn’t a lot of information available on the web to help prospective buyers make an informed purchasing decision. To help fill the void, I was able to arrange a test ride of the Ute, and I posted a fairly detailed review here: http://mycargobike.net/2010/06/15/first-look-at-the-kona-electric-ute/
Sadly, I haven’t been able to find a Yuba dealer in my area to test the elMundo. I don’t know anyone who owns an elMundo with whom I can correspond. Lacking first- or second-hand experience, I’m hoping you can answer some of my questions to help me and my readers understand where the elMundo fits in the assisted cargo bike marketplace. With your permission, I would like to post this letter and your responses on my blog within the next couple of weeks.
Your website provides a brief description of the elMundo, several photos, and a tantalizing price for a bike in this category. I’m especially excited to see a lithium ion battery and a 750W hub motor. However, there are few details for those of us who obsess over such things. For example, who makes the motor? How did you decide it was a good match for your bike? Does it have internal gearing to help deliver good torque at low speeds?
Besides the low price, there is a significant advantage of having a motor integrated by the bike manufacturer (as opposed to an after-market build like my bike). Customers will assume that the manufacturer has carefully matched the capabilities of the bike and motor. The manufacturer will analyze loads and stresses to enhance the reliability of the product. The bike will be tested under strenuous conditions, and a single warranty will cover both the bike and the motor. Can you assure us that this analysis and testing has been done on the elMundo, and can you provide details regarding your warranty?
The Yuba Mundo is rated to carry loads of up to 400 pounds, excluding the rider. Since there is nothing to the contrary on the web page for the elMundo, I assume that the weight limit is the same. With the help of that powerful motor, it will now be possible for people to carry some pretty heavy loads up an incline. Of course, what goes up must come down. That’s why I was surprised to see only rim brakes in your photos of the elMundo. From my perspective, that seems a little risky. I know disc brakes are now an option on the Mundo. Are they also available for the elMundo, or does the hub motor preclude the possibility of a front disc rotor?
It also seems possible that your motor is likely to produce new stresses on the front fork that didn’t exist on the non-electric bike. Have you made any modifications to strengthen the fork?
Finally, I’m curious how much the elMundo weighs. Is the battery removable for remote charging, and can you also charge it on the bike? How long does it take to fully recharge? Do you have any estimates regarding the lifetime of the battery and motor?
If you have any customers who would be willing to share their thoughts and experiences on this bike, I would love to talk to them.
I look forward to hearing from you.
July 7, 2010
Great to hear from you. I have visited your blog many times before and I did find the content extremely interesting, your analysis and opinions are well documented. Also this is the first email we are getting from you asking questions about the elMundo.
If you were interested we could put you in touch with a few users of the elMundo Cargo Bike, these users are mostly in the Bay Area. Also one our dealer Cycle9 specializes in electric bikes and cargo bikes and has supplied electric Mundos to a numerous customers. One of them Mark Strosberg has been commenting on your blog, he purchased his Mundo from Cycle9.
Currently the elMundo is a Mundo Cargo Bike frame with an after market electric kit installed on the bike. So a lot of the questions your are asking can’t really be answered since it seems that many customers are riding electric Mundos with different motors or battery packs. The model supplied by us integrates a battery placed between the rack and the seat stays, it is removable but doesn’t need to be removed to be charged.
The motor is made by Aoetema, we have tested various combinations of motors and like this specific 750W version for many reasons one of them being the torque it gets for hill climbing.
The 36V LiPO4 battery offers about 20 miles of charge on flat terrain. Motor, battery, controller are under warranty for a year.
We do ship the elMundo with disc brakes installed on the rear (although it doesn’t show on the pictures!).
We have no doubts that the Mundo bike is the best platform for an electric Cargo Bike in the market place due to the strength and solidity of the Hi-ten steel frame. So the elMundo can take the rider, the loads, the passengers and the electric assist.
The battery can be removed and the current combinations gives a range of about 15-25 miles depending on the conditions and terrain.
Let me know if you have further questions or comments.
After this email exchange, I asked Yuba further questions about the weight of the bike and clarifications regarding the warranty, but I haven’t received a reply. If or when I do, I will post their answers.
Yuba’s first response was a bit of a mixed bag, from my perspective. I’m happy to hear the elMundo now comes with a rear disc brake. This seems to be a fairly recent development, and it’s a welcome step in the right direction. However, it doesn’t alleviate my concerns about stopping this bike when it’s carrying a load. Stopping distances for cargo bikes in general is a topic I hope to investigate in the future.
The Hi-ten steel frame of the Yuba is an interesting feature compared to the aluminum frames of the Ute and the Hammer Truck. It is heavier, of course, but steel will bend under stress rather than break. If you’re contemplating moving heavy loads on a cargo bike, that might be important to consider. But in that case, remember to test those brakes and upgrade them if you need to.
Although I have no experience with the Aoetema motor, the reviews I’ve found on the web have been mostly favorable. It appears to be a reasonable choice for this bike. However, it sounds like Yuba views the motor as an after-market product, so I’m guessing they would refer you to Aoetema if you had any warranty issues. This negates one of the advantages I was hoping would come from an integrated product. When you buy a car, you get a single warranty that covers the whole car. You don’t have to go to different companies to deal with motor issues, frame problems, etc.
The one year motor/battery/controller warranty is okay, but only half the duration of the BionX warranty.
Although the elMundo remains an interesting option in the electric cargo bike market, I’m hesitant to recommend it without trying it. Ben didn’t give me hope that I would get a chance to do that any time soon. If I could find a Yuba dealer in Seattle, I’m betting they wouldn’t have an elMundo ready to ride. Like Kona, Yuba seems reluctant to vigorously pursue this market. I would love to know whether that is due to technical issues, or if these companies are skeptical about the size of the market. In either case, the cargo bike revolution is off to a very leisurely start in America.
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.
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.
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!
[NOTE: I originally posted this article on June 15, 2010. In mid-August, Kona officially added the Electric Ute to its 2011 catalog (here). I’ve re-edited the article to incorporate new information and correct a few mistaken assumptions on my part. I compare the Ute to the latest version of the Yuba elMundo and the upcoming Trek Transport+ here.]
One of our local bike shops (Alki Bike and Board) received its first Kona Electric Ute on Saturday. The owner knew that I was keenly interested in taking this bike for a test drive, and he immediately notified me of its arrival. I got to the shop while they were putting the final touches on the bike assembly.
The Kona Electric Ute will have a chapter in the history of cargo biking, because it is one of the first cargo bikes from a well-known manufacturer that includes an electric motor as an integrated option. Most of the electric-assisted cargo bikes currently on the road are after-market builds, which makes them more complicated and expensive for the average consumer. With a retail price of $2599, the Ute is considerably less expensive than my Rans Hammer Truck / BionX motor combination. The question is, did Kona skimp on anything to hit that price target? Does it still feel like a quality ride? Could I use this bike to do the same chores I do on my bike?
The Ute is a good-looking bike, with golden paint (but not too flashy) and a nice, thick wooden cargo deck mounted on top of the long, thin battery. It’s not an Xtracycle, and it hardly looks like a long-tail bike. It’s not just nicely-proportioned; the weight is well distributed between the front and rear (by contrast, my bike is quite tail-heavy if you try to pick it up). The Ute is also quite light for an electric cargo bike. Unfortunately, I didn’t have a scale to get an accurate measurement, but I estimate it weighs about 45 pounds.
Despite the Ute’s pleasing proportions, the cargo deck is quite long. It provided ample room to seat both my children during our test ride. However, it’s several inches narrower than mine, and the kids complained that it wasn’t as comfortable to ride on.
The owner of the shop was surprised that the Ute came with a triple chain ring on the cranking end, including a large top gear that should take you up to 30 mph if you feel the need for speed. A handsome seat, dual kickstand, front and rear fenders, and a handlebar-mounted warning bell are other nice touches that enhance a general impression of a bike that hasn’t been nickled-and-dimed to hit a price target. The bike comes with one pannier bag (not shown here). A second will cost $80. Of course, you’ll still need to buy lights, but it’s possible you could hit the road with this bike for under $3000. That’s a few hundred more than the Yuba elMundo, but that’s a very different bike.
On the question of quality, my first concern was the brakes: a rim brake on the front and disc brake on the back. It appears the front rim brake is necessary to make room for the hub motor. It’s not obvious how you could install a disc brake without changing the motor as well.
How critical is a front disc brake? That depends on your situation. If you intend to carry big loads down steep hills, the rim brake will be an issue. The rim on the Ute looks pretty durable, but it’s hard to know how it would wear under heavy use. In my opinion, Kona wasn’t trying to build the ultimate hill-hauling machine with the Ute. If that’s what you’re looking for, there are other bikes to consider.
The Ute’s 250-watt front hub motor looked tiny compared to the 350-watt BionX motor I use. Could a motor this small really help with big loads and big hills? I took it on a ride around the neighborhood to find out.
On flat terrain, the motor behaves much like mine. With these motors assisting your legs, it’s not always clear what gear you should use. Many times you can shift into a higher gear than normal, and the motor makes up the difference in effort. You don’t even have to down-shift when coming to a stop, because the motor will help you start again.
But there were some differences too. Unlike the unusually quiet BionX, the Kona motor always lets you know it’s there. It emits a sound that I can best describe as a moistened finger rubbing across glass — sort of a cat-like mewling. It’s not an unpleasant electric whine, but it’s a noise you probably wouldn’t miss if you turned the motor off and pedaled along without it.
Like my bike, the Kona motor is activated by pedaling, not by a handlebar throttle. There’s always some debate about whether a throttle or pedal activation is better. Since I’m used to pedal activation, I’ll admit being partial to it. Kona says they use a “Dutch design TMM torque sensor” to determine how hard you’re pedaling and how much additional assistance to kick in with the motor. During my ride it worked pretty smoothly, but wasn’t quite as responsive as the BionX system. In some cases, the motor continued to pull for several seconds after I had stopped pedaling. When you apply the brakes, the motor stops immediately, but I’m not sure how it knows to do that.
Another difference is motor vibration. With the motor directly under the handlebars, I felt small vibrations from this motor more distinctly than I do from mine. Is this a showstopper? Not at all. But does it diminish the illusion of bionic legs propelling me smoothly and quietly down the road? Well, yeah.
To test the bike’s hill-climbing abilities, I found a pretty steep section of road — several hundred yards at maybe 15% grade. My first attempt was successful, and the motor provided welcome help on the steep incline. I had to pedal a little harder than my bike, but in hindsight I realize I had the motor set on the middle assistance level. Changing to the highest assistance level might have provided more help. However, a fist-sized hub motor isn’t going to perform miracles. I decided to repeat the experiment so my wife could take some video of it. On my second ascent, the motor suddenly shut off about half-way up the hill. This was disconcerting — I’ve never experienced anything like that with the BionX motor. Thinking I had done something wrong, I made another attempt in a lower gear, but this time the motor was comatose during the entire effort.
Now I was worried that I had damaged something. Fortunately, the motor came back to life on the flat roads back to the bike shop. I am now pretty sure that the controller was purposely shutting down the motor to prevent damage from overheating. Unfortunately, there is no indicator on the Ute’s display that the motor is in an overheated state. Because of that, you’ll worry if it ever happens to you (which it may not). After a little cooling break, everything should return to normal.
Battery / controller
I’m pretty excited about the Ute’s battery. It is nicely integrated in the bike, and it’s big enough to provide ample range. The battery can be removed and taken to your office for charging, or it can be charged on the bike.
Although I didn’t have time to test it, the combination of a big battery and a small-ish motor should theoretically give the Ute good range on a single battery charge. The rider can adjust the assistance level by quick taps of the power switch behind the handlebar display. Obviously, range will increase with a lighter level of assistance.
The system uses a separate controller box mounted on the main stem above the crank, but it’s smaller and more refined than the Stoke Monkey controller. The handlebar display shows battery status, speed, mileage, and assistance level.
Due to the battery cut-out issue, I didn’t have the opportunity to haul a load up a hill. For my purposes, that would have been the most interesting (and most strenuous) part of my test drive. In lieu of that, I put both kids on the cargo deck (about 140 pounds total) and rode some laps around the parking lot. The bike handled this test well — no squeaks, no noticeable flexing, and no balance issues with the heavy load and high center of gravity.
Of course, cruising on this bike is the easy part. Starting and stopping was a slight challenge for me, because I’m accustomed to the low step-down of my Hammer Truck. With the Ute, I have to jump off the seat, tip the bike slightly (not a good idea with kids on the deck), or reach a tip-toe down. Despite a few wobbly moments, I felt pretty stable with the kids on the back.
But I probably wouldn’t make a habit of transporting more than one child on this bike. I carry both kids down our hill on my Hammer Truck, but I keep it slow — around 10 mph. Even with regenerative braking engaged, the brakes can get pretty hot. Attempting that trip with the Ute’s brakes would cause too much anxiety.
Although it has been helpful for me to structure this review using comparisons to my own bike, it’s not entirely fair given the Ute’s significantly lower price. I am personally excited by the Ute’s value and the potential to expand the cargo biking market.
If you want to see some clips of the bike in action, check out the video version of my review:
Today I took my bike for its first checkup after 7 months and over 500 miles of hill-chewing. As you may recall, I have done no maintenance on this bike other than one application of chain lubricant. Since I rely on it to provide safe transportation for my family, I wanted to ensure that no latent problems were developing.
For the diagnosis, I went to one of Seattle’s pricier bike shops. I deliberately chose a different shop than the one that built my bike, because I wanted a second opinion — especially on those mission-critical brakes. The owner of this shop is a big fan of the Big Dummy/Stoke Monkey bike, and I thought it would be enlightening to talk with someone who is somewhat skeptical of my bike. He has a reputation for pulling no punches, so I prepared myself for some rough sledding.
But actually, things went quite well. The owner found several occasions to point out advantages of the Stoke Monkey, but these were arguments that I’ve written about previously. He complained that the BionX hub motor makes it harder to adjust the rear disc brake calipers, because the hub blocks easy access to the dial that positions the brake pads. He charged me an extra $10 for the additional effort required.
The total bill was $75 for labor. He adjusted and lubed my derailleur to recover my lost gears, cleaned and tuned the brakes, and lubricated various cables. I paid another $25 to upgrade the front brake cable for better responsiveness, but that wasn’t critical. Using the $75 figure for essential maintenance, I calculate a cost of about 15 cents per mile. On the one hand, this figure is probably high due to the difficult geography this bike has to tackle. On the other hand, it’s probably too low on an annualized basis, because I didn’t have to replace any parts this time. In another 6 months, I may have to replace at least one of the disc brake rotors and possibly the pads, but that shouldn’t cost more than $50. As I suspected, the regenerative braking of the BionX motor seems to be extending the life of my brake components. What isn’t clear is how often other components will need to be replaced, and how much that will cost. Although it will be pretty cheap compared to repairs/maintenance of a car, the number of bike miles will also be less, so it remains to be seen which is cheaper on a per-mile basis.
Just to be complete, the electricity to help propel me during this time period averaged about 1/2 cent per mile. Hardly worth mentioning compared to the maintenance.
One sweet moment occurred while I was paying my bill: a customer was admiring my bike and asking questions about it. He was initially attracted by those huge Xtracycle-incompatible pannier bags. He was really intrigued when I told him the bike was assisted by a quiet (and virtually invisible) electric motor. He was standing less than a yard away from the owner’s Big Dummy at the time, but it was my bike that caught his eye. I have no doubt that the owner had him converted to a Big Dummy shortly after I left the shop, but my bike and I had our moment.
I plan to return to the same shop after another 7 months and 500 miles. The owner did a good job and seemed to know what he was doing.
I went to the “Sustainable West Seattle Festival” with my family on a rare sunny Saturday afternoon, hoping to see a Kona Electric Ute that a local bike shop was scheduled to show there. It was fun to see many like-minded people showing various sustainable choices — bee keepers selling local honey, farmers selling organic chicken feed for your home-raised chickens, Zip cars, small wind turbines, and various kinds of electric bicycles. Unfortunately, the Ute was not one of them. Apparently, the Kona rep had not gotten a Ute to the bike shop in time for the festival, so this elusive bike foiled my best efforts once again. I know a bike shop in our area that definitely has one, but it’s a bit of a drive and a ferry ride to get there, so I’m hoping to combine that trip with another outing sometime.
If my efforts to see a Ute have been challenging, getting a demo of the Yuba elMundo seems nearly impossible at the moment. There is only one bike shop within 100 miles listed as a Yuba dealer. When I contacted them about the possibility of seeing the elMundo, what I got instead was a strong recommendation to steer clear of this bike as well as the Ute and any other inexpensive cargo bike. The bike dealer recommended the Surly Big Dummy with a Stoke Monkey motor as a superior way to handle our hilly geography. This came as a surprise to me, because the Big Dummy was the bike I first intended to buy, but I was disuaded by several factors. I’ve listed these elsewhere, but the main problems were the size of the bike (my wife wants a bike that is easy to ride) and maintenance of the Stoke Monkey (frequent alignment is necessary to avoid problems with the second chain).
The bike dealer pointed out that the Stoke Monkey is better for climbing hills, because it works through your bike’s gears. In contrast, a hub motor like the BionX applies torque after the gears. When you climb hills, a hub motor is running at low speed where it is inefficient. I can verify that: on the steepest part of my hill where you want the most help, the motor does not feel like it is working as hard as you would like. The bike dealer says his Big Dummy climbs 20% grades (steeper than mine) with less effort than my bike.
So, if you’re serious about replacing your car and hauling big loads up steep hills, the Big Dummy and Stoke Monkey are probably the best choice for you. But unfortunately, it requires a custom build, and it’s a pretty crude system compared to my bike. This video shows what I mean:
Everything demonstrated here seems like it’s a generation behind my bike. The controller and burrito bag seem pretty crude: my controller must be built into the BionX battery case, which is beatifully mounted under my cargo deck. Putting that big battery in the XtraCycle bag seemed primitive in comparison. I could go on, but you can watch the videos and form your own opinions. (If you haven’t seen my bike video, it’s here.)
I hesitate to criticize the Big Dummy and Stoke Monkey, because it’s a great bike and people have done a lot of amazing things with it. For example, the BikeForth.org blog is one of my favorites — the author is pushing the boundaries of car replacement with weather coverings and solar power for his Big Dummy. It’s really great stuff, but I sometimes feel like he’s quite a bit ahead of his time. My practical side is struggling to find ways to get more people on bikes, even if only for some of their trips. I would love to jump directly into a future where bikes are as prevalent in my country as they are in Denmark, but to enable that future we have to find a way to make our bikes more mainstream. I feel like my bike is closer to that practical ideal than the Big Dummy/Stoke Monkey, but the price is still a barrier unless you’re completely replacing a car. Even as a cargo biking advocate, I still drive our mini-van, frequently. With our current infrastructure and suburban location, it’s not possible for me to transport my busy family without the car at this time. So the cost of the bike comes on top of the cost for the car, and that is a challenge for many family budgets.
On the other hand, I don’t want to recommend the Ute or the elMundo if their inexpensive price comes at the cost of reliability, functionality, or safety. Until I see them first-hand, or a good bike magazine does a thorough review and comparison of them, I can’t say if these are good candidates for advancing the worthy cause of cargo biking.
Just for fun, here are a few numbers I measured this morning, in an effort to make my blog a little more precise:
70 pounds — the unloaded weight of my Hammer Truck, battery, motor, bags, lights, etc. That’s actually somewhat heavier than I expected. And that doesn’t include the canvas shopping bags, rain cover, bike lock, water bottle, bungee cords, and other things I keep in the side bags for easy access. No wonder I feel a little weak when I turn off the motor (only occasionally) and try pedaling up our hill.
30 pounds — the weight of my non-powered bicycle for comparison. But I almost never ride it if the cargo bike is available.
10% grade — the incline of the road in front of our house.
18% grade — the incline on the steepest section of road on our way to school every morning. It lasts for about 100 yards. When I’m hauling a 70-pound kid and 20 pounds of books and instruments up that part of the hill, the motor and the human are both close to their limits. This is when you begin to appreciate the miracle of cars. Just press that accelerator a bit more towards the floor, and 10 times the mass of my load leaps up the hill at 5 times the speed. But that challenge only lasts for 100 yards, and most people don’t have 18% inclines in their daily routes. The 10% grade feels more reasonable, as you can see in the first part of my Electric Cargo Bike video (http://mycargobike.net/2010/05/06/cargo-bike-video), where I haul my son and his stuff around the corner and up the hill.
7 months — the length of time I’ve been riding my bike down that hill, often with two kids as passengers, without any brake replacements or adjustments. I think that is the best aspect of the BionX regenerative braking system. I’m just beginning to think that an adjustment might be necessary in the next month or two. My wife wore the brake pads on her traditional bike down to the metal in that same span of time.
Good news: I’ve found an owner as well as two local bike shops who have the Kona Electric Ute. I hope to take it for a test drive this weekend at a local sustainability faire!