A new electric bike — the Koben, from Karmic Bikes — promises to fix what ails the electric bicycle industry. We spoke to its designer to find out what those problems are, and how he thinks he’s solved them.
Yesterday afternoon, the Gizmodo team was tossing around a press release about the Koben. “Damon [from Jalopnik] says these guys are legit,” wrote Sean. “Wait a second,” I said to my dog, “I used to get the scoop on every electric motorcycle ever, and this sounds pretty hot.”
So I told the Giz team why hub motors suck and why mass centralization is good and about centers of gravity and all sorts of nerdy stuff like that. And man, I thought to myself, this bicycle ticks all those boxes. Then I realized it’d been designed by Neal Saiki, the former NASA engineer whose designs helped make Santa Cruz Bicycles what it is today, and who founded Zero Motorcycles, the only dedicated electric motorcycle manufacturer left standing after that world boomed with investment, then failed to sell any products.
Well, Neal just called me and filled me in on all the fun details. Let’s take a look:
Batteries You Can’t Replace Or Rebuild
The batteries in any electric vehicle (be it a Tesla Model S or a forklift) are composed of many individual cells, all clumped together to form a pack. Traditionally, if one of those cells fails, you have no option but to replace all of them. And, if new technology improves battery capacity, there’s no way an existing electric vehicle owner can take advantage of it without buying a whole new battery pack or a whole new vehicle. That’s bad.
“The big bugaboo with all these batteries is their packing,” starts Neal. Tesla is a great example. The cells inside the battery pack they sell, those only account for 40 percent of the price of the pack. It’s hard to get it waterproof, it’s hard to get it vibration proof and to do that in a package that doesn’t cost a million dollars.”
Electric vehicle batteries also need to be hugely crash proof, with strengths far, far greater than that required of gas tanks.
“You can’t replace the cells inside those packs,” continues Neal. “With our technology, you just pop off the cover and replace an individual cell. Those are a fraction of the price of an individual cell, so you’re able to replace them if they break and upgrade them as they improve. You can upgrade our batteries forever. You’re going to have a whole bunch of Teslas out there where you have to buy a whole ‘nother battery to replace or upgrade it.”
Motors That Wear Out
“Hub motor bikes are great for the first year; maybe two. They have a really limited lifespan. An electric motor is a bunch of little magnets that are glued on, with little wires connecting everything together. A motor in the wheel just gets beaten to death, it’s too brutal an environment.”
Locating a motor in a wheel hub subjects it to every last iota of movement and every shock the wheels encounter as they roll. Know how sitting in the middle of a plane is far less bumpy than sitting way forward, near the cockpit or way in the back, near the bathrooms? It’s the same thing on a bicycle, just hopefully with less poo-stench and many more impacts and vibrations.
Too Much Unsprung Weight And Not Enough Mass Centralization
Locating a motor in a wheel hub also drastically increases unsprung weight. That’s any weight that’s below about the mid-point of a vehicle’s suspension; the parts that move before the suspension does and the parts that roll. Many bicycles don’t have suspension—that action is handled by the frame and your ass—making reducing unsprung weight even more important.
Particularly in a bicycle wheel, because any additional weight not only exacerbates the momentum of wheel movements up and down, but increases the force it takes to overcome the momentum of the wheel to either accelerate or brake it. The heavier a wheel is, the more force you have to put in to go faster or slow down.
Like that example of sitting at the extreme ends of a airplane mentioned above, there’s also penalties for pushing mass out away from a vehicle’s center. Doing so increases the effort it takes to steer and reduces stability as that mass has a longer lever to affect the vehicle with. Moving a vehicle’s mass as close as possible to its center makes it easier to change direction and more stable.
“We’re well aware that most of our buyers are just looking to get home from work,” acknowledges Neal. “Only people that are really into high performance bikes will notice it, but those people love the difference a bike with centralized mass brings.”
Which is a very long-winded way of saying that Koben’s motor is located on its bottom bracket — where a bicycle’s center of gravity should be located.
High Centers of Gravity
“One of the problems we saw, talking to existing electric bicycle riders, is that the bikes are too top heavy. You have to park these things and move them around in your garage and top heavy bikes just tend to fall over or be hard to hold up.”
Most electric bicycles on market today locate their batteries on a rack, behind the seat. See everything we wrote about mass centralization above to understand why that’s bad on the move and this explanation to understand why that’s bad when you’re stationary. The Koben locates its relatively light battery back on the seat tube, just above the bottom bracket. Again, as close as possible to the ideal center of gravity.
In addition to the de-centralized mass and high unsprung weights, traditional electric bicycles also fail to take into account the additional weight brought by their electric powertrains when it comes to the suspension geometry.
“Electric bikes are still heavy, so the geometry has to be a little different; the steering force has to be a little quicker to compensate for the additional weight. We did a few tricks to the steering to get it nice and light, even though the bike is heavier than a normal bicycle.”
Neal added more rake than is standard (the angle of the fork), while reducing trail (the location of the axle). On any vehicle, that should enhance stability while reducing steering effort.
Not only does the Koben feature a rebuildable, upgradeable battery pack and a motor located away from the “brutal” wheels, but you’ll also see a totally straight chainlink and no derailleurs. The bike comes in two versions: a single-speed and one with a continuously variable transmission housed inside its rear hub. The single speed in particular should be ideal for commutes through cities, where its drive is as robust and simple as is possible for a bicycle. The CVT shouldn’t be far behind.
“If you commute by bicycle, you really don’t want to work with adjusting the gears the whole time and fixing derailleurs and whatnot, so it’s really nice to have the simplicity of a single-speed. Then, with the electric assist, you can add more for uphills and less for downhills and so on. It gives you the hill climbing ability without all the complication.”
Electric bicycles tend to either be too cheap or too expensive. The affordable ones are total pieces of shit that, even before you get to their terrible motors and crappy batteries, are just bad bicycles to start with. The expensive ones are great, but cost way too much money. Once you get to carbon fiber frames and full suspensions and Dura Ace components, you’re already talking a stratospheric price and the electric drive just takes that even further.
“The biggest pain point with eBikes is that the battery wears out after a couple of years,” Neal summarizes. “I’ve got hundreds of emails from riders with other brands complaining that, once the battery goes bad, it’s either hard or impossible to get a replacement. Being able to rebuild the battery is our biggest advancement.”
With direct sales, the Koben is available to Kickstarter backers for starting at $1,300 for the single-speed and $1,600 for the CVT version. That’s a nice, mid-range price for a good commuter bike.
There’ll be two further model distinctions: one with a 300Wh battery that can hit a top speed of 20mph and travel for 25 miles on a charge and an “S” version with nicer components, a 460Wh battery, a top speed of 25mph and a range of 40 miles.
“Range depends on how much you pedal,” finishes Neal. “We give a very realistic number; it’s not the motorcycle industry, where everyone is exaggerating the range.”
IndefinitelyWild is a new publication about adventure travel in the outdoors, the vehicles and gear that get us there and the people we meet along the way. And electric bicycles, because I’m the only person at Giz that really, really cares about unsprung weight. Follow us on Facebook, Twitter, and Instagram.