It’s Saturday, and I’m taking a break from digging holes, plumbing pressure tanks, wiring well pumps, and literally pounding sand (building a base for steps) to talk about yet another electric bike I had a chance to ride!
Mid-drive (BBS02), internally geared rear hub, and enough power to climb anything. And it scoots right along on the flat!
As always, read on for details!
This is a fatbike, built for the specific purpose of climbing mountains in the middle of nowhere and “fixing” Guardian Portals. If you’re not familiar with that, it’s an obscure part of Ingress that often involves remote areas, cell boosters, HAM radio links, or satellite internet. And if you’re not familiar with that, well, it’s just a fatbike for climbing crappy trails.
It’s running rather large tires - the whole “fatbike” thing does require fat tires. These are fairly inefficient to pedal, but go wonderfully with a motor!
A large battery (about 500Wh) mounted in the triangle frame bag keeps the bike well balanced, and provides plenty of power for ripping up hillsides and mountains.
The main motive power comes from a rebranded BBS02 750W mid-drive unit. This mounts to the bottom bracket (as is clearly seen here), and runs power through the chain.
An advantage of this setup is that it uses the bike’s gearing - so the motor is geared for a “normal pedal cadence” and the bike’s gearing takes care of the rest. For something designed to climb mountains, this is perfect - you can use low gears on the steep trails, and use higher gears if you’re running briskly along flat fire roads.
A neat feature of the BBS02 is that it can turn the front chain without the pedals turning - so if you’re being lazy on the throttle, you don’t have to pedal. You can, of course, and the pedals work without the motor turning.
In the rear end, there’s a big hub in the rear wheel. This isn’t a geared motor like the Rad Rover has - it’s a SRAM G8 8 speed internally geared hub! This has a single input chain ring, and 8 speeds one can select sequentially.
Shifting is done via a twist grip on the right handlebar. It’s pretty straightforward to use.
On the left bar, there’s a thumb throttle for using throttle power, a controller for changing the pedal assist levels, and a quite nice little light.
The combination of a mid-drive motor and internally geared rear hub makes for a potent drivetrain. In the low gears, it’ll outclimb a goat, and in the high gears, it will cruise along very happily, well in excess of 20mph.
One goes with a mid-drive motor because one wants to apply it’s full rated power (750W in this case) at all possible speeds - crawling slowly (though not terribly slowly) up steep hills, or to just haul ass.
The handling is somewhat twitchy. The aggressive geometry shows. It likes to corner! This is exactly as intended by the owner, but I prefer something with a bit more stability for a daily driver.
One downside of the lack of a chain guard or similar is that the chain tension is very critical, and this frame doesn’t allow for an offset chain ring. If you’re not smooth on the throttle, it will eagerly toss it’s chain off the front chainring.
But, ridden smoothly, it will do literally anything you want. It’s got enough power for anything at all.
This DIY build comes in at roughly the same price as the Rad Rover. It’s the same power, but the internally geared hub makes it a good bit more capable, both in terms of hill climbing, and in terms of quick running on rough roads. It’s a bike built for a purpose, and it’s damned good at that purpose.
Should you build one like this? Probably, if you need to do the exact same things. It’s great fun, and really will go through just about anything. But it’s completely overkill for anything involving the streets. As much fun as fatbikes are to ride, I just don’t see them as being the most useful way to get around paved or near-paved surfaces.