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Tandem ebike conversions using BBSHD or BBS02

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    Tandem ebike conversions using BBSHD or BBS02

    This thread is an assortment of pics and notes from builders that have done this before. Info may be incomplete, incorrect or model-specific, but generally it is possible to do a tandem install with these motors.

    BBS02 build. The HD won't fit in this tandem - too wide and interferes with stoker's timing chainring.

    An easy & painless process of building an electric bike.

    I installed a BBSHD on our Calfee Carbon Fiber tandem. The tech from Calfee walked me through the process. I installed the motor in the stoker position and went with RH drive for the front to rear chain. A pair of fixie cranks from eBay solved the drive crank issue.

    You may have to get a new front eccentric so that you can use conventional cranks.
    Q&A on the above build
    Q: How exactly are you connecting second chain ring to the spare axle?
    A:The second chain ring is attached to the square drive fixie crankset and attaches directly to the Bafang spindle.

    Q: How are the arms and external ring moving independently from the Eclipse?
    A: The eclipse is bolted to the Bafang motor and the fixie crank attaches to the Bafang shaft. It replaces a single crankarm.

    Q: Did you encounter any difficulties in alignment when swapping this over to belt drive?
    A: I had to get a special long square drive front spindle from Phil Wood. A LBS ordered it for me. The Q factor is wide but it is not an issue.

    This install was performed on a Hokitika Hoka Tandem. I had absolutely no problems with the install, just three hiccups. The first was that I needed a BB spacer to give clearance on the right side chain stay. Due to hiccup number one, I had hiccup number two which was the stabilizer now required a bit MORE spacers and longer bolts to attach to the left side under the BB lockdown nut. (pretty sure those are not correct names for the items, but you probably know what I am talking about. I am posting pictures of this. Hiccup number three came as a complete wake up moment as I did not know, and I have been riding tandems for 10 years, and regular bikes for 30+, and I never knew that crank arms had the square taper mounting holes oriented two different ways! I just do not know the reasoning behind this, but if you were to hold a crank arm where the BB spindle mount is on top, you will see either a square or a diamond hole. The kit comes with diamond holes arms. I had to use the left side crank from the tandem due to the timing chain and it had a square hole, so when installed, it was not clocked right. To correct this temporarily, I just mounted the left side as normal, right side I used the triple crank to keep the clocking correct until the new crank arm comes in. It is ugly, but worked beautifully. My goal in all of this is to be able to quickly revert this back to a non-e-bike. I was even going to leave the front derailleur hooked up but the wide range of the cassette caused noise, so I just removed the derailleur but kept the cable tied up and in place.

    BBSHD used for this conversion. No additional info available

    I'm in the middle of converting a Gary Fisher Gemini tandem bike to a BBS02 mid drive.

    Not easy. The BB axle, eccentric, and shell are not standard. It took some machine work to make spacers so the 100mm BBS02 would fit.


      The Gary Fisher is up and running. It has some unique features such as a 7 speed Nexus internal hub, two slightly different sized ring gears for the stoker and captain, and the "synchro" chain has been moved to the right side. Different rings are a matter of what was on hand, not by design.

      Synchro is in quotes because the riders aren't going to be synchronized b/c of all the freewheel action, front and rear. The different sized rings also contribute, but that's inconsequential.

      I have a friend who has a production electric tandem, and it is set up the same way and essentially works alike except for the internal hub. Interestingly, on my tandem and his production bike, the stoker can be the only power source (w/o assist) if the captain gets lazy and stops pedaling!

      This was a fun project that I took on because the derailleur hanger was damaged in an accident. It took a bunch of hoop-jumping to make this nice vintage cruiser. I couldn't stand to junk this frame, so.....


        I want to convert a Co-Motion Speedster Tandem to an etandem. My concerns are clearance between motor and timing gear as I am running a Gates belt.
        I also have DaVinci square drive cranks with the converted spiders for the Gates belt sprockets.
        Has anybody been down this road?


          We were told by many bike shops and some forum members it could not be done.
          First build, 2014 through 2016:
          SUN beachcomber 7spd tandem, 26x2 wheels. Chosen due to it's "foot-forward" step-through frame. Used solely on rail-trails at low speeds. Needed some oomph to get up hills.

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          Over many trial and error iterations:
          - BBSHD from luna Cycle, mounted under stoker. Battery at rear. In retrospect, not enough weight up front, best to mount BBSHD and battery up by Captain.
          - 8-speed Alfine rear hub; no derailleur
          ​- shifted entire drive train to right side​, lots of playing with chain ring spacers and chain ring adapters.
          - BBSHD crank is freewheeling but stoker and captain still in synch. Found a freewheeling crank from Sick Bike Parts in CA (now defunct?) to unlink the cyclists and make starts and stops easier.
          - brake lever motor cutout sensors and gear change sensor cutout
          - upgraded to Luna 52v shark battery after charging failures two years in.

          Heavy and hard to transport laid flat in back of my pickup truck with tailgate down. Built a bolted tailgate filler for security on longer trips and 2x4 ply rack above bike inside bed for gear transport.

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          Attached Files
          Last edited by Maxtandem; 02-23-2024, 01:44 PM.


            We were told by many bike shops and some forum members it could not be done.
            Second build, 2019 to present day:
            Commissioned custom steel frame with Couplers to my design, from Master craftsman and problem solver Roulez Cycle in Lynn, MA. Thanks Jay!
            He designed the front fork and wire protector tube (slotted) to protect bafang wiring.
            I did the painting and outfitting.

            Six-piece coupled steel frame and custom fork. 2" and 1.5" shop fab steel tubing. Custom brazed fork. S&S stainless couplers, two sets.
            Welded rear stainless modular dropsouts (Paragon Machine Works, Polydrop)
            Bafang BBSDH 750w middrive mounted under Captain for better weight balance. Luna 52v battery likewise. Epoxied alum. slotted plate to underside of battery to capture secure locking strap to frame.
            Rohloff speedhub 500/14, threaded rear axle with Pitlock security. Love it, absolutely problem free.
            48t chainrings front and rear
            Two-bolt 31.8mm seat post clamps from
            26x2" heavy tandem rated wheelsets, 2" A/T tyres.
            Lever pull disc brakes, third drag brake on rear.
            All brake and Rohloff cables have in-line couplers. No issues with adjustments.
            Ursus Jumbo rear kickstand, cheap front kickstand to hold front half of bike during disassembly for transport in two pieces.
            Disabled PAS on motor entirely, only use throttle for hill and wind assist.
            Super heavy 78 lbs with motor and battery- more when loaded.
            We call the bike Shermy Archer (after Sherman the Tank and the brand Sturmey Archer.)
            10 to 40 mile rides on unpaved Rail Trails and even some bedrock, all over the US and Canada. Wonderful.

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            Last edited by Maxtandem; 02-23-2024, 01:57 PM.