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Building a 1000 watt mid-drive electric full-suspension folding bike

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    Building a 1000 watt mid-drive electric full-suspension folding bike

    Building a 1000 watt mid-drive electric full-suspension folding bike

    Finished build

    I'm pretty happy with the way the bike came out, and I've been using it to commute for a whole week without any issues. Huge hills that used to be painful for me on the way home feel just like flat ground. The bike tops out at about 30 mph, which is much faster than I ever want to go. My commute involves multiple segments: biking to the train, riding the train, biking to work, and then back again. I've been riding a Dahon folder for about two years now, so I wanted to keep the ability to bring it with me wherever I go. The finished bike folds to approximately the same size that it did before electrification, so I'm very happy about this. The only real difference in the folding now is that the seatpost is blocked by the motor, but this really isn't an issue in practice. Note: this is cross-posted on my personal site at: http://mattshirley.com/dahon-jetstre...02-ebike-build

    Unfolded


    Folded


    Folding the bike (video):


    Donor bike

    The donor bike was a 2008 Dahon Jestream that I've been commuting on for ~2 years now. I previously added an Axiom Journey cargo rack and built a new rear wheel incorporating a Shimano Nexus-7 internally geared hub. Even without a motor this was a fun bike to ride... the suspension works great to smooth out potholes and the occasional curb jump.



    Build details

    My biggest concern with this build was the configuration of the bottom bracket on this bike. As you can see, the seat tube actually exits ahead of the bracket, leading to some slight interference with the motor. I decided not to modify the frame in any way, since in reality - with such a big chainring - the motor clearance is fine.



    The chain line is pretty great, and it certainly helps to have the geared hub to play aroung with rear cog tooth number.



    I'm running a Surly Singleator chain tensioner in the "push-up" position to add just enough tension to keep the 1/8" chain from slipping off at full throttle.



    I've run the gear sensor just behind the chainring, in between the shift cable standoffs. It's really quite stable here and doesn't cause any interference.



    The chainstays on this bike are flared out, with a small flat area near the dropouts. This is where I decided to mount the speed sensor, as it allows me to make the most adjustment, and the spoke angular velocity is lower toward the hub so I believe this allows the sensor to function better, and lessens damage to the sensor in the event the magnet collides with the sensor body.



    I really lucked out with the battery mount, since the staff at Cambridge Bicycle pointed me to this awesome Blackburn Outpost rack that mounts like a waterbottle cage. The finished mount allows me to fold/unfold the bike easily, and the weight distribution is ideally better than mounting under the seat or on the rear rack. The battery bag that Luna supplies is really well made - seems very watertight, and mounts just fine as a saddlebag as well using the velcro straps.



    The rear shift and brake lines run under the monotube through eyelets that are nicely sized and spaced to allow the BBS02 wiring harness to run between them.



    Up front there was a bit of wire mess, but after lots of 8mm cable wrap the cables/wires are much easier to deal with.



    I really like the new full color DPC-14 display. It's very easy to read outdoors, and the information display is quite useful. I'm not sure the speed is accurate (compared to GPS measurements), but it's close enough. Voltage and amperage displays are helpful as well. The left-side throttle feels good, and integrates well with my right-hand shift controls.




    Under the rear rack, but above the fender, I've mounted an Ortlieb micro saddle bag.



    The whole bike still folds almost exactly like it did before adding the motor.







    There's also plenty of retroflective tape on the bike for visibility.



    Bill of materials
    Dahon Jetstream $200 Craigslist
    Shimano Nexus-7 hub $160 Amazon
    Sunringlé CR-18 rim $30 Amazon
    Cut spokes $40 LBS
    Schwalbe Marathon Winter studded tires $40 x 2 = $80 Amazon
    Axiom Journey rack $40 Amazon
    Ortlieb Commuter bag $200 Ortlieb
    8mm cable wrap $10 Amazon
    52v Mighty Mini Cube Ebike Battery Pack Panasonic GA 7ah $355 Luna Cycle
    Bafang BBS02 750w Mid Drive kit $544 Luna Cycle
    Total $1659

    #2
    Awesome job and write up!

    How often do you fold-down for your usual commute?

    Comment


    • mdshw5
      mdshw5 commented
      Editing a comment
      Thanks. I commute 5 days a week, and my commute routine is Home -> train (fold) -> (unfold) Work -> train (fold) -> (unfold) Home. Now with the greater speed and range I can actually beat the train routine if I just bike Home -> Work, which is around 11 miles. It's still great to have the folding capability in nasty weather or if I'm just not feeling like riding city streets for 10+ miles.

    #3
    There's something extra special about a folding ebike, combining the easy transport while in a plane/train/car. and then unfolding it and riding off with the enhanced performance of e assist. It's a great combo! Nice job!

    Comment


    • ykick
      ykick commented
      Editing a comment
      Yep, so many positive virtues to folding eBikes. God forbid, if I were ever limited to 1qty eBike and could only have one? Swift folder conversion would be my choice.

    #4
    Hi,

    I am thinking about building a folding bike, My concern is weight limit though. How is yours holding out? It appears its rated for 230lbs? I'm already 220 so... I'm thinking i need a bit more bike.
    My focus is for when we camp at RV parks Already built normal size bikes but the folding thing sounds very attractive for the purpose

    Any comments would be appreciated

    By the way, Yours looks excellent!

    Kevin

    Comment


      #5
      ksgreene sorry I didn't see this notification back in April. I guess I can give a more long-term update now :). The bike frame has held out really well. Here's a list of things that wore out/needed replacement since the original build (keeping in mind the bike was almost 10 years old at this point anyway):

      - rear air shock seals wore, so replaced with a Kindshock A5-RE (http://www.kindshock.com.cn/en/produ...&show_list=1): ~$70
      - replaced Shimano Nexus 7 hub (work out the clutch pawls) with a Nuvinci N360: ~$250 including new spokes cut
      - replaced Sunringle CR18 rim as the rim brakes work through the sidewall making it unsafe: ~$20
      - lots of brake pads (seriously like every 3 weeks or so): $?

      I'm about 180lbs, the bike is maybe 45lbs, and my work back is about 30lbs fully loaded, so I'm riding mostly city streets with 250-260lbs total. I think the weight *distribution* is more important than the total weight, since the rear rack is unsprung weight (it attaches to the rear triangle) along with the N260 hub, and the BBS02 and battery are mounted over the pivot point along with my body, so the moving parts on the bike experience close to what they were designed for in terms of force.

      Comment


        #6
        Nice! For folders with small wheel diameter I feel suspension is very beneficial. I got a 20" fat tire electric folder and it is a bumpy ride compared to a ful-size bike with skinnier tires. By bumpy I mean the bike jumps up and down a lot more than large-wheeled bikes due to the small diameter fat tires if I go fast on uneven roads. And no, keeping the tire pressure low is not a solution (absorbs small rough stuff, but not bumps and undulating terrain, messes with the steering, makes it hard to pedal without power).

        Folding has been surprisingly helpful, toss it un the back of the car, no rack needed. Unwieldy to carry folded though, and at 48lb a bit much for more than a few feet.

        The skinny-tired Dahon here looks a lot more compact than mine. But at 6'4" mine fits me better than the skinny tired version of my bike (larger dimensions all around, not available on the skinny tire mldel). Just something to be aware of - most folders don't accommodate 6'+ tall folks well.

        Mine is a hub model, but if that gives-up the ghost, it will get a mid-drive update ;)
        Last edited by Kocho; 10-23-2017, 01:09 PM.

        Comment

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