I live in the USA and if I want to get rid of my car I would need to be able to cover 70 miles round trip with moderate exercise in a reasonable amount of time. I think if I could cruise at 35MPH (56 KMH) that would be enough to make the switch.
It may be stupid, but I’d like to try to avoid an electric motorcycle - those need insurance, registration fees, real parking spaces, and a special license. Also, I enjoy getting some activity while riding. FWIW I’m not worried about legality, but I do plan to stay off bike paths/sidewalks to avoid endangering pedestrians and other cyclists.
My idea so far is to start with a gravel bike frame for aerodynamics, efficiency, and sturdiness in case of a pothole or rogue curb. From there I’m thinking about a 1500w hub motor, dual batteries, higher gears, bigger brakes, and permanent lights for visibility. Also a good helmet of course, crashing at that speed can be pretty bad.
Has anyone done something like this and had it go well/poorly? Anything I’m clearly missing in my plan? Also feel free to tell me if I’m an idiot, but I already know that bit.
I’ll start with the public policy spiel: the fastest class 3 electric bikes max out at 45 kph (28 mph), meant to be just below where mopeds max out at 30 mph, then after that, other, faster two wheeled machines that require licensure and insurance. Proceed with care with the advice you receive. At the very least, please don’t tailgate cyclists or pass them aggressively or too closely, and don’t ride on bike paths. OHV tracks will probably be more fun anyway.
Ok, with that out of the way, there are some technical challenges you’ll face. For reference, a dual battery Bikonit MD750 ebike with the speed governor raised to its maximum 60 kph will run at full speed to empty in approximately 32-35 kilometers (20-22 miles). Allegedly.
That particular electric bike has a 750 W motor and a pair of 700 Wh battery packs, each weighing 4 kg, give or take. So that’s 1.4 kWh for 35 kilometers, if we’re being optimistic.
Your build seeks to attain 56 kilometers one way, but let’s round up to 70 km for reserve capacity. If you’re able to charge at work, then that puts your energy requirement at some 3 kWh, which is a lot of battery. This will also be 16 kg (35 lbs) on its own, which has implications on your bike’s frame and suspension.
Now, if you ran slower than max speed, the requirements drop substantially. The same MD750 above is good for 80-100 km when run at only 30-40 kph. But it sounds like you’re looking for a one hour commute each way.
In that case, I would suggest you reexamine the electric motorbike, as they have the advantage of being prebuilt, already have the necessary capacity, take standard motorbike accessories, and have a much taller max speed, if you so choose. Some even have removable batteries, to bring it into your workplace and charge indoors.
Price of an electric motorbike, of course, may be higher than building your own electric bicycle. But the amount of battery cells in question is substantial and much care in design would be needed. The finished product would likely also be somewhat conspicuous, versus a stock electric motorbike. But this may be a function of whether your workplace has secure indoor parking.
I love seeing what people will build and ride on two wheels, and many will necessarily push the envelope on what’s appropriate around their area. Proceed with care.
Really appreciate your thorough answer! I’ll definitely think about an electric motorcycle. IMO if I’m going to go through licensing, I might as well get something that goes full car speed.
I think you’re right that battery capacity would be the biggest issue building out an ebike. That said, a big frame triangle can fit a lot of cells. Something like 3000Wh could probably get the job done. If I could get the bike aerodynamic enough to cruise on a 750w motor, then max range would be 3000/750=4 hours or 140 miles. Obviously won’t hit that in real world conditions, but 70 would be possible.
I terms of legality and ethics, I totally agree about treating cyclists and pedestrians with respect - on my current ebike I keep it under 18MPH on bike paths and slow to pass others at a safe speed. My vision for this bike is more rural back roads near my house which are mostly empty but have an occasional car passing by. I’m not a big fan of laws generally. On that front I’ll probably run a cracked controller with a toggle so if I get pulled over I can put it back in legal mode with a keypad sequence. Slap some aliexpress “250 watt” and “class 2” stickers on it and trust that the local cops are few and otherwise occupied. Where I live folks rip illegal dirt bikes and ATVs on public roads with impunity so I can’t imagine this being a big problem.
If people are ripping around on dirt bikes already a Surron or similar night be a good bet. The only issue is then you lose it on the ability to pedal. There are similar bikes that also have vin numbers if you actually wanted to go legal at some point but dirt bikes aren’t street legal without extras anyway and it sounds like enforcement is lax.
The electric unicycle idea is also pretty cool. They look to me like skiing but on the street. So you’d actually get exercise even if it’s working different muscles than a bicycle. But if you go that route you’ll need to go the extra mile on safety gear.
As someone else stated, 35mph the whole way is a lot on an ebike, even bringing that down to 30 extends the range a lot. There may be some road or gravel bike that has the range you’re looking for if your flexible on the speed. Those seem more fun imo, but the YouTube channel TailhappyTV has shown off ebikes that go 100 miles on a charge. I haven’t seen the speeds at which they go but in my opinion a long ride means more time to listen to audio books.
Either way good luck!
I’m wondering whether you would want to consider a mid-drive motor instead, if pursuing an ebike build. 750 W delivered at the hub, without the benefit of gearing, may only be marginal to attain your envisioned speed. But in a mid-drive configuration, 750 W should hold 50-60 kph without an issue. The reason for going higher power beyond that would be to improve the acceleration at those higher speeds, but if you’re planning for mostly back roads, then you won’t have the stop-and-go or slow-then-go scenarios that might warrant more power.
To reduce the power consumed, also make sure to consider the tires. Certainly, aerodynamic drag starts taking effect after 20 kph, but the rolling resistance of some of the fatbike or dirt bike style tires mounted on some ebikes can be serious sources of drag as well, when running at higher speeds.
In my case, my street-running ebike has too wide of tires, being 26x4.0, and I don’t have the option to go narrower because of the rim width. In future, I plan to build custom wheels that has a 220mm wide hub but a 45mm rim. This will look ridiculous, but it’ll let me take narrower tires that run higher pressures and have lower weight penalty from the anti-puncture layers. If you’re going to take an existing frame, pick one with narrower hub widths, tailored to the surface types you intend to ride on.
My “test” for rolling resistance is the speed I can attain with motor off, pedaling only at a leisurely pace. With my acoustic bike, 20 kph is easy with no heavy breathing or anything like that. With my ebike, it’s more like 10-12 kph. That doesn’t sound like a lot, but it has huge consequences at speed. Anything to get that pedal-only speed up will pay dividends at the top speed.