I recently added a Bafang mid-drive motor to a Babboe Big Cargo trike. Some challenges, but it’s certainly doable.
My wife has an illness that causes her to have poor balance, and she can’t walk long distances. That seriously reduces our outdoor activities and opportunities.
A few years ago, by chance we rented a Bakfiets E-cargo-trike at Jonker Fietsverhuur in Terschelling, NL. It was a great success! That Bakfiets trike had an integrated Shimano motor, and hub gears. It gave me the idea to find or make something similar we could use to get out and about here in Ottawa.
I decided that a hub gear was essential. It’s not easy to get a fully-laden cargo trike rolling, especially uphill, and so it’s helpful to be in a low gear. Hub gears allow changing gear when stopped. I discovered that many “less expensive” E-cargo-trikes have rear-hub motors with derailleur gears. Mid-motor E-cargo-trikes with hub gears are expensive, and difficult to find.
Eventually I found a Babboe Big in Montreal, no motor. It had a Shimano Nexus-7 hub gear - whereas the E-version would have had a rear hub motor with a derailleur, which I didn’t want. The Babboe Big can carry 100 kg in the box, with a 100 kg rider. More than adequate.
The Bafang motor won’t fit directly to the Babboe. That’s because the motor has to “wrap around” the bottom bracket, and it has to snug-up to a position that’s only about 10 to 12 mm from the outer face of the bottom bracket shell. The Babboe has an 80 mm deep horizontal main tube, and the bottom bracket is vertically centred in the main tube - thus the main tube overlaps the motor’s “space” by about 15 mm to 20 mm.
Someone on the web has installed a Bafang by cutting-out the bottom of the Babboe’s main tube, and welding-in a bent reinforcement plate at the required clearance line. It’s doable, but I think it would weaken the main tube, and it would cause the motor the motor to hang down about 100 mm below the main tube, leaving only about 100 mm clearance to the road.
I sketched-out several options, mostly based on relocating the bottom bracket. They all placed the motor too low. Eventually I hit on the idea of adding another bottom bracket shell above the main tube, just in front of the seat tube. No need to cut and repair the main tube, the motor would be well-protected, and no reduction in road clearance. The new bottom bracket would be about 60 mm higher than the original - so I’d just raise the saddle. On a trike you don’t need to touch the ground when you stop! The original BB height on the Babboe was about 240 mm, so although the final BB height of 300 mm is a bit higher than most bikes, it’s easily manageable.
I’m not a welder. Jakob Flansberry (https://www.facebook.com/flansberrium) was recommended to me. He notched-out the seat tube so the new bottom bracket would be properly supported and fully welded, and he added a post in front of the motor to protect the cables. He did an excellent job all round.
A couple more mods were required. My wife isn’t gonna clamber in over the sides of the box (which kids do, using built-in steps behind the front wheels). To help her get in, I removed the front panel. Unfortunately, entering and exiting at the front will tip the trike up (personally tested, and proven to be scary). To prevent this, I added a support frame that swings down under the front edge of the box. It also holds the trike stationary when she steps in or out. In its retracted position, the frame functions as a front rail and “handlebar” for her when we’re rolling. The frame has clips which hold it in both its working positions. And I added “Styrofoam” panels to the seat to give her a snug fit. Although I’ve proven the concepts, these mods are still a work in progress.
The original gearing on the Babboe was 32T x 22T (23 to 55 gear-inches). That was about right for a laden un-motorized cargo trike. The default 44T Bafang chainring gave gearing that was too high (31 to 76 gear-inches). I was rarely above 4th gear. I replaced it with a 36T chainring from PreciAlps, which brings the gearing to a range that matches typical speeds we might travel at (25 to 62 gear-inches, about 12 to 30 km/h at 100 rpm). I also considered the 40T chainring from PreciAlps - which is neat because it is offset to match the offset of regular Bafang chainrings. The 36T is too small to be offset - it is "flat", so it moves the chainline out by about 6 mm relative to the original Bafang chainring (which was very closely aligned with the rear sprocket of the hub gear).
Because the BB was lifted up, there was a risk that that the "returning" chain might contact the underside of the chainstay. With the 36T chainring it would make contact, if it were tight - but it isn't tight, because it's not under tension. The natural "sag" of the returning chain is just enough to provide clearance under the chainstay. I did relocate the gear cable to increase the clearance for when the chain bounces.
I got the 36T chainring here (€6.25 shipping to Canada, 1 week delivery): https://precialps.com/uk/24-bafang-bbs01-bbs02
I’m still familiarizing myself with day-to-day operation:
*You have to consciously steer _all the time_. Otherwise you’ll drift with the camber, usually towards the edge of the road. And you have to be careful when removing one hand from the bars.
* You have to slow down for every bump, especially those ****** diagonal depressed curbs that are so common here at path/road/path crossings. Similarly tree roots on paths! If taken too fast, any single or diagonal bumps will cause you (and your passenger) to suffer a series of nasty sideways lurches as each front wheel separately rises and falls. It’s also quite easy to lose steering control if you hit a bump too fast.
* You have to find 3 tracks through potholes, bumps, etc. Sometimes it’s easiest to let the rear wheel take the bump/pothole (AKA taking one for the team).
* You can’t / don’t want to go all that fast – unlike a bicycle which “tracks” in a straight line, and which becomes more stable when riding faster; a tricycle doesn’t track, and it becomes less stable if ridden too fast.
The conversion has been a success. We've already visited several places we could never have gone to. It's sturdy enough, with adequate tires, that we'll be able to ride light gravel rail-trails. I'm fairly confident that we'll manage smaller hills, but that's still to be tested!
More photos:
https://www.dropbox.com/sh/ubmgs6ed2...2VJQOtX1a?dl=0
My wife has an illness that causes her to have poor balance, and she can’t walk long distances. That seriously reduces our outdoor activities and opportunities.
A few years ago, by chance we rented a Bakfiets E-cargo-trike at Jonker Fietsverhuur in Terschelling, NL. It was a great success! That Bakfiets trike had an integrated Shimano motor, and hub gears. It gave me the idea to find or make something similar we could use to get out and about here in Ottawa.
I decided that a hub gear was essential. It’s not easy to get a fully-laden cargo trike rolling, especially uphill, and so it’s helpful to be in a low gear. Hub gears allow changing gear when stopped. I discovered that many “less expensive” E-cargo-trikes have rear-hub motors with derailleur gears. Mid-motor E-cargo-trikes with hub gears are expensive, and difficult to find.
Eventually I found a Babboe Big in Montreal, no motor. It had a Shimano Nexus-7 hub gear - whereas the E-version would have had a rear hub motor with a derailleur, which I didn’t want. The Babboe Big can carry 100 kg in the box, with a 100 kg rider. More than adequate.
The Bafang motor won’t fit directly to the Babboe. That’s because the motor has to “wrap around” the bottom bracket, and it has to snug-up to a position that’s only about 10 to 12 mm from the outer face of the bottom bracket shell. The Babboe has an 80 mm deep horizontal main tube, and the bottom bracket is vertically centred in the main tube - thus the main tube overlaps the motor’s “space” by about 15 mm to 20 mm.
Someone on the web has installed a Bafang by cutting-out the bottom of the Babboe’s main tube, and welding-in a bent reinforcement plate at the required clearance line. It’s doable, but I think it would weaken the main tube, and it would cause the motor the motor to hang down about 100 mm below the main tube, leaving only about 100 mm clearance to the road.
I sketched-out several options, mostly based on relocating the bottom bracket. They all placed the motor too low. Eventually I hit on the idea of adding another bottom bracket shell above the main tube, just in front of the seat tube. No need to cut and repair the main tube, the motor would be well-protected, and no reduction in road clearance. The new bottom bracket would be about 60 mm higher than the original - so I’d just raise the saddle. On a trike you don’t need to touch the ground when you stop! The original BB height on the Babboe was about 240 mm, so although the final BB height of 300 mm is a bit higher than most bikes, it’s easily manageable.
I’m not a welder. Jakob Flansberry (https://www.facebook.com/flansberrium) was recommended to me. He notched-out the seat tube so the new bottom bracket would be properly supported and fully welded, and he added a post in front of the motor to protect the cables. He did an excellent job all round.
A couple more mods were required. My wife isn’t gonna clamber in over the sides of the box (which kids do, using built-in steps behind the front wheels). To help her get in, I removed the front panel. Unfortunately, entering and exiting at the front will tip the trike up (personally tested, and proven to be scary). To prevent this, I added a support frame that swings down under the front edge of the box. It also holds the trike stationary when she steps in or out. In its retracted position, the frame functions as a front rail and “handlebar” for her when we’re rolling. The frame has clips which hold it in both its working positions. And I added “Styrofoam” panels to the seat to give her a snug fit. Although I’ve proven the concepts, these mods are still a work in progress.
The original gearing on the Babboe was 32T x 22T (23 to 55 gear-inches). That was about right for a laden un-motorized cargo trike. The default 44T Bafang chainring gave gearing that was too high (31 to 76 gear-inches). I was rarely above 4th gear. I replaced it with a 36T chainring from PreciAlps, which brings the gearing to a range that matches typical speeds we might travel at (25 to 62 gear-inches, about 12 to 30 km/h at 100 rpm). I also considered the 40T chainring from PreciAlps - which is neat because it is offset to match the offset of regular Bafang chainrings. The 36T is too small to be offset - it is "flat", so it moves the chainline out by about 6 mm relative to the original Bafang chainring (which was very closely aligned with the rear sprocket of the hub gear).
Because the BB was lifted up, there was a risk that that the "returning" chain might contact the underside of the chainstay. With the 36T chainring it would make contact, if it were tight - but it isn't tight, because it's not under tension. The natural "sag" of the returning chain is just enough to provide clearance under the chainstay. I did relocate the gear cable to increase the clearance for when the chain bounces.
I got the 36T chainring here (€6.25 shipping to Canada, 1 week delivery): https://precialps.com/uk/24-bafang-bbs01-bbs02
I’m still familiarizing myself with day-to-day operation:
*You have to consciously steer _all the time_. Otherwise you’ll drift with the camber, usually towards the edge of the road. And you have to be careful when removing one hand from the bars.
* You have to slow down for every bump, especially those ****** diagonal depressed curbs that are so common here at path/road/path crossings. Similarly tree roots on paths! If taken too fast, any single or diagonal bumps will cause you (and your passenger) to suffer a series of nasty sideways lurches as each front wheel separately rises and falls. It’s also quite easy to lose steering control if you hit a bump too fast.
* You have to find 3 tracks through potholes, bumps, etc. Sometimes it’s easiest to let the rear wheel take the bump/pothole (AKA taking one for the team).
* You can’t / don’t want to go all that fast – unlike a bicycle which “tracks” in a straight line, and which becomes more stable when riding faster; a tricycle doesn’t track, and it becomes less stable if ridden too fast.
The conversion has been a success. We've already visited several places we could never have gone to. It's sturdy enough, with adequate tires, that we'll be able to ride light gravel rail-trails. I'm fairly confident that we'll manage smaller hills, but that's still to be tested!
More photos:
https://www.dropbox.com/sh/ubmgs6ed2...2VJQOtX1a?dl=0
Comment