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    Hello From Florida

    Very interested in adding mid drive motor to our tandem. Reading as much as I can but nothing is clicking on my "that makes sense" radar. From what I see of the mid drive motor, I would mount it to my front position just like a single bike, just do not install the gear to the right side and mount our normal left timing crank and right crank arm to the motors BB. I understand that I would lose some, or all of the eccentric adjustment but I already have plans on fabricating something to keep tension on the chain. I don't get what the talk is of safety and making the stoker have a freewheel capability. Pedaling together is what tandem riders do and what we have done for 15 years now. Is this doable? What are the brake levers for in the kit? Can't i use my current setup as is using my own brake levers? The biggest question is this, how long will a charge last on a typical rpad ride? How many miles can we ride with this thing? Can we do centuries or long solo rides? If these things are only good for 20-30 miles then this kind of money just doesn't add up for pedal assist? Thanks for any input others may have experienced. I am not willing to give up any hearing in the rear and do not see why this isn't just a plug and play for the front of a tandem. What am I missing here?
    Last edited by Jsshort2302; 1 week ago.

    #2
    Hi - there are a number of tandem build threads, here's but one of them: https://electricbike.com/forum/forum...dem-conversion

    From the threads I've seen with standard configuration tandems, the (narrower BBS02) mid drive motor is installed in the stoker position (if the frame can accommodate it). You wrote, "I am not willing to give up any hearing in the rear" - are you thinking motor noise? You probably shouldn't, as they're usually very quiet.

    If the motor is on the captain's BB and the motor powers up, the stoker might get a rude, unexpected pedal spin surprise - at 3 times their leg strength.

    The e-bike brake levers have a motor cutoff safety switch - there are other ways to accomplish this with standard levers.

    For the range question, the tangled, not straight-forward questions for you are:
    • How much battery are you willing to buy/tolerate the weight of?
    • How much motor assist are you going to need?
    Don't know the answers to the above just yet? Join the club. Range is difficult question to answer. Factors like terrain, average speed desired, weight, relative drive train drag, and wind resistance come in to play. I can sail along at 20-23MPH 100% motor assist, on slightly rolling terrain for about 25 miles, on a 13AH 52 volt battery pack (approx 350lbs bike/rider) - people's results are all over the place. I carry a spare on longer rides. Here, with mid motors, most are using 48-52 volt batteries ranging anywhere from 5-30AH.

    Last edited by ncrkd; 1 week ago.
    Intro: http://electricbike.com/forum/forum/...ntro#post17033
    First build, Priority Eight / BBSHD / Nexus IGH
    Second build, 2018 Crust Scapegoat, BBS02 or BBSHD, Rohloff IGH
    Third build, 2018 Crust Evasion step-thru, BBS02 or BBSHD, Shimano Alfine 8 IGH

    Comment


      #3
      HiJsshort. A tandem project first up is ambitious. I’m not overly familiar with tandem chain lines but I can certainly see that as the primary build issue to overcome. I’m sure there is somebody on the forum that has already done it though and should be able to point you in the right direction.
      Re the endurance issue. It’s really a case of how longs a piece of string. A large capacity battery on a low power assist level will last considerably longer than a small battery on a high power setting. My wife and I have just ridden 100klm trail with a 14AH 52 volt batteries. We were on low power assist levels though but made the distance easy. I commute 50 klm daily on medium power setting, again no issue. No, the chain line is the issue to overcome. All the best with the project.

      Comment


        #4

        "You wrote, "I am not willing to give up any hearing in the rear" - are you thinking motor noise? You probably shouldn't, as they're usually very quiet."

        I meant gearing, not hearing. Pretty sure I am smart enough to realize electric power is pretty quiet. My concern about gearing is the fact that the motor install requires the use of just one chain ring. I wish to keep all three due to us touring with a load and terrain, hills to mountains.

        "If the motor is on the captain's BB and the motor powers up, the stoker might get a rude, unexpected pedal spin surprise - at 3 times their leg strength."

        This is not an issue as the stoker will not get anything they already don't get when we both start pedaling, the essence of riding a tandem.

        "The e-bike brake levers have a motor cutoff safety switch - there are other ways to accomplish this with standard levers."

        This is very good to know.

        "For the range question, the tangled, not straight-forward questions for you are:[LIST][*]How much battery are you willing to buy/tolerate the weight of?"

        The biggest stock battery available to purchase.

        "]How much motor assist are you going to need?"

        Just enough to help us along when the going gets slow. As we have aged and my wives ability has decreased, I would like the assistance to be enough to move us down the road in the upper teens. I am a strong and fit cyclist.

        "Range is difficult question to answer. Factors like terrain, average speed desired, weight, relative drive train drag, and wind resistance come in to play."

        I understand this, was just wondering if there was an "average" duration for use at a 20-30 % pedal assist. I am not using this as a means to commute, but to keep an active female that cancer has degraded her balance and riding strength and allow her/us to ride in a fashion that was normal before cancer.

        All of that being said, I think the biggest deal to overcome is if there is enough clearance on the left side to add the left drive crank as apposed to just the crank arm in a normal install on a single bike?
        [/QUOTE]

        Comment


          #5
          Originally posted by Jsshort2302 View Post
          The biggest stock battery available to purchase.
          I'd consider the EM3EV 52 volt 30AH triangle battery
          Originally posted by Jsshort2302 View Post
          I think the biggest deal to overcome is if there is enough clearance on the left side to add the left drive crank as apposed to just the crank arm in a normal install on a single bike?
          The armature case sticks out a lot further on the BBSHD motor (versus the BBS02):

          BBSHD:
          Click image for larger version  Name:	fetch?id=73831&d=1537221030.jpg Views:	1 Size:	509.4 KB ID:	79252





          BBS02:
          Click image for larger version  Name:	fetch?id=76644&d=1540218288.jpg Views:	1 Size:	1.08 MB ID:	79253





          For range guesstimates, there are some range calculators out there - I have used this one.
          Last edited by ncrkd; 1 week ago.
          Intro: http://electricbike.com/forum/forum/...ntro#post17033
          First build, Priority Eight / BBSHD / Nexus IGH
          Second build, 2018 Crust Scapegoat, BBS02 or BBSHD, Rohloff IGH
          Third build, 2018 Crust Evasion step-thru, BBS02 or BBSHD, Shimano Alfine 8 IGH

          Comment


          • Jsshort2302
            Jsshort2302 commented
            Editing a comment
            Thanks NCRKD, those pictures tell a good story. Could I ask, for the HD motor, with it fully installed flush on the right side bottom bracket shell, how much motor is exposed past the left side bottom bracket shell and how much spindle? It looks like the HD will fit in my build but some measurements would answer my problem. If the HD will not fit, I have no problem with the 02 as our goal is to get assistance, not pure drive. I just want the power to last for a 5-7 hour period, like a long touring day or a difficult metric century. Thanks.

          • ncrkd
            ncrkd commented
            Editing a comment
            Hi - when I get back home I'll take the measurements - I have both a BBSHD and BBS02 motor on my bench.

            I saw your reply over on one of the tandem build posts, where you wrote, "I want to install the motor up front, no chain ring on the right side of the motor, but instead, install the normal left side drive crank to the sq taper BB".

            Sounds like you've got a normal tandem drive setup with a right-side wheel chain, and a left side stoker to captain timing chain.

            You want to install the motor up front on the captain's BB, normal rotation with the ring gear case on the right but not mount/use a chain ring. If so, bad news, you'll get no motor assist because the spindle is not driven by the motor. There's a sprag clutch between the spindle and the chain ring, so the rider can coast while the motor spins the drivetrain.

            Now I'm contemplating, what would happen if you locked the sprag clutch. If I remember correctly people have gotten injured when the sprag failed and locked up.

            Apologies if I've got your setup wrong.
            Last edited by ncrkd; 1 week ago.

          #6
          Nope, you got my setup correct and that did answer my question, its the gear driven, not the bottom bracket. I was mistaken. I will just have to use the rear setup and pick a chain ring that will give me the range I want, probably start with the 44 tooth and make adjustments. Running an 11/34 cassette now but could always go 11/36 or even 11/40. Thanks for your postings! Now just waiting till after holidays to buy the HD kit.

          Comment


            #7
            Or maybe a geared or 2-speed hub motor? Best of success with your build, and pictures will help the next builder.

            I used to be able to ride the MS150 metric century events, hope to again some day, My leg strength isn't there yet, but at least my arse (saddle) is broken in again!
            Last edited by ncrkd; 4 days ago.
            Intro: http://electricbike.com/forum/forum/...ntro#post17033
            First build, Priority Eight / BBSHD / Nexus IGH
            Second build, 2018 Crust Scapegoat, BBS02 or BBSHD, Rohloff IGH
            Third build, 2018 Crust Evasion step-thru, BBS02 or BBSHD, Shimano Alfine 8 IGH

            Comment


              #8
              Here's the BBS02 motor dimensions:

              Click image for larger version

Name:	BBS02_dimensions.jpg
Views:	1
Size:	102.0 KB
ID:	79409

              Intro: http://electricbike.com/forum/forum/...ntro#post17033
              First build, Priority Eight / BBSHD / Nexus IGH
              Second build, 2018 Crust Scapegoat, BBS02 or BBSHD, Rohloff IGH
              Third build, 2018 Crust Evasion step-thru, BBS02 or BBSHD, Shimano Alfine 8 IGH

              Comment

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