I found a great way to bike in all weather: a $200 Walmart “Beast” fat bike equipped with a Stokemonkey mid-drive electric motor. This electric Beast easily traverses roads covered with two to eight inches of fresh snow or slush-covered streets.
If you use your bike mainly for transportation (as opposed to recreation), you are painfully aware that you can’t choose the weather conditions you ride in. If you’ve sold your car to be car-free, and you’ve got to get somewhere, often you have no other choice than to get there with your bike. Most of the time this is more of a pleasure than a problem. But there are some conditions that stop even the most determined bicyclists. Snow is one of them.
I like to ride in the winter. Every November I put studded snow tires, such as Schwalbe Marathon Winters, on my bike. However, these tires are not intended for biking on snow; they are really only for biking on icy roads. They prevent bike tires from slipping on patches of ice, and they do this very well. But if the road has even a few inches of snow on it, these tires don’t work well. They don’t prevent your drive wheel from slipping, and they don’t prevent ridges of snow pushing your front wheel back and forth. In snow it’s hard to ride faster than jogging speed (6mph).
A few years ago I started hearing about so-call “fat” bikes with huge 4-inch tires that could roll over snow and sand. Could this be what I was looking for? I wanted to find out but I was deterred by fat bikes’ steep price: $2,000 seemed to be the minimum and $6,000 fat bikes are not unusual. However, a few months ago I discovered The Beast, a $200 fat bike sold by Walmart. It is inexpensive because it is a simple heavy steel one-speed bike with only a rear coaster brake. This bike is so laughably crude and inexpensive compared to other fat bikes that it has inspired a kind of cult following. It’s so cheap a gearhead such as myself would not hesitate to hack it, crash it, and trash it. Just what I needed to experiment with!
So a few weeks ago I purchased a Beast. As I expected, it performed very well going on flat terrain and downhill, but was almost impossible to pedal uphill. Not a very practical bike for my hilly home town. My plan, of course, was to add an electric motor to my Beast. As far as I can tell, only a few people have electrified a Beast. I’m guessing it will become a popular mod. There are more and more electric fat bikes available but they tend to cost thousands of dollars. The Beast is in many ways the perfect bike to electrify. When electrified, many of its faults become features. For starters, it has a one-speed drive chain. As anyone who uses an electric bike regularly knows, most electric bikes don’t need more than one speed. Even if you’ve paid for multiple speeds, you’ll find that you always accelerate up to speed with the motor and then pedal in the highest gear anyway. I seek out one-speed bikes to electrify. So one speed was not a problem, it was actually an advantage. The simplicity of the Beast’s drive train removed many points of failure. Secondly, the Beast is heavy, about 50 pounds. Recreational fat bikers will see this as a drawback, but for me it means that if I need to hack the bike, such as welding brake mounts to the frame, it will be easy because of the thick tubing.
One issue is where to put the electric motor: front wheel, rear wheel, or mid-drive? The rear wheel is out of the question because it has the bike’s only brake in its hub. Putting the motor in the front wheel would also be a bad idea. In general putting a hub motor in a front wheel is less desirable than a rear wheel because most of the weight of a bike in on the rear wheel. And a hub motor in a front wheel can spin out, which is especially dangerous if you accelerate when turning. This is a minor nuisance on flat pavement, but a very real danger when going uphill on a dirt road, which you’d expect to be doing on a fat bike.
And in general putting the motor in a wheel on a fat bike presents all kinds of problems because of the fat bike’s unusual hub widths. That leaves a mid-drive motor. Mid-drives drive the crank of a bicycle; they have incredible torque so they are especially well-suited to fat bikes where torque is more important than speed. I originally intended to put a Bafang BBS02 mid-drive on my Beast but found that the Bafang won’t fit in the Beast’s extra wide bottom bracket without some serious modifications. Then I remembered my old friend the Stokeymonkey.
The Stokemonkey was the first electric bike motor I purchased back in 2009, back in the day when I rode a Surly Big Dummy longtail cargo bike. The Stokemonkey is basically a large hub motor specially modified to sit in a bracket bolted to a bike frame. It has a chain that turns a bike’s crank on the left side (with the unfortunate side effect that you have to pedal with the motor; you get used to it). Unlike motors mounted in the hub of a wheel, the Stokemonkey drives the rear wheel through bike’s drive train which increases the motor’s torque. If you have a low-geared bike that can be an incredible amount of torque. I remember once using my Stoked Big Dummy to carry over 500 pounds up a 20% grade.
Like the Beast, the Stokemonkey has a kind of cult following among cargo bikers who find that it is a no-nonsense extremely torquey powerhouse for their bikes. When inventor Todd Fahrner decided to discontinue the product a couple of years ago, the ebike heroes at Grin Technologies not only revived it, but made many improvements. At $995 it is expensive for an ebike kit but it will probably outlast you; it is a timeless non-proprietary design that you can move from bike-to-bike. It would be possible, for example, for me to use it on my Beast during winter and move it to my Big Dummy during the rest of the year.
The Stokemonkey is perfect for the Beast because the Stokemonkey doesn’t require modifying the Beast’s wheels or bottom bracket. And the Stokemonkey’s adjustable frame bracket allows the motor to sit off-center to accommodate the Beast’s wide frame. The original Stokemonkey came with a strap-on controller bag. I found I can strap it to the Beast’s head tube and that it has enough room for a five-mile-range lipo battery. It was a simple installation.
Another issue was how to improve the Beast’s braking power. I didn’t think the coaster brake would have enough stopping power, so I spent some time thinking about how to add additional brakes. In the end, however, I discovered it was a non-issue. When riding the Beast on uphill or level snow the rolling resistance is so high that I get sufficient braking power just by stopping pedaling. And when going downhill on snow the brakes don’t do much anyway; it is better to brake by positioning the bike sideways like a skier or snowboarder would. Come to think of it, skis and snowboards don’t have brakes.
The one situation where I’d like better brakes is riding downhill on a road. At least with a coaster brake I can stand on the brake with my full weight. And a coaster brake is the ultimate low-maintenance brake. Water and salt can’t get in the brake, and you never need to adjust or replace brake pads.
So after a couple of hours installing the Stokemonkey, I took the Beast for a spin. It worked great. On the trail by my house I was able to go 15mph with almost no shaking; on my regular bike I cold barely do 6mph and it was difficult to stay upright. The Beast was able to go up a 10% snow-covered hill with no problems, and I had full control going down a 20% grade. However, going back up the 20% grade proved too much and I had to walk the bike back up that hill.
I am new to fat biking but I’m getting the hang of it. I learned that tire pressure is important: 8psi for snow, 15psi for trails, and 25psi for roads. And I’ve learned that I can’t make sharp turns at hight speed. I wish my Beast had fenders–curiously I’ve rarely seen a fat bike with fenders. I might also add lights. And upgrade it to a higher-voltage controller. And it might be fun to hack my Beast into a longtail electric fat bike. Or modify it to carry farming implements. I see a lot of possibilities here. As the proprietor of Boxy Bikes custom electric bikes in Ithaca New York, hacking bikes is my job. And I love my job.
If you thought that was interesting, you might also enjoy these related posts: