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    Mid Drive vs. Hub Drive Shootout

    One of the threads brought up the question "Which is more efficient, a hub or mid drive?". I did not know the answer to this, but I know my DD hub drive may be about 70-85% efficient depending on the RPM. After this question was posed, I hoped that somebody who knew the answer would post the solution. I have still not seen the solution.

    A local forum member Gr8fun offered to to a side by side comparison with his mid drive and my hub drive. We both live in Sonoma County. We will be filming the Sunday (date TBD) challenge and uploading it to YouTube. It is okay with me if anybody else wants to join in on the challenge.

    When I was selecting parts for my ebikes, the mid drive craze had not yet arrived. I chose what some may consider to be earlier generation technology in a DD hub motor and trapezoidal wave controller. As I was building my bikes, this forum started and I saw the public's high regard for mid drive motors. I was too deeply invested in my hub drive and Lyen controller inventory to join in on the mid drive fun. I do see, however, the huge advantage in the gearing of a mid drive. I have taken my hub drive mountain biking on steep, narrow trails a few times and it was clear that the 58T chainring and 14T smallest rear cog was not the best setup for climbing. I am building a 20T chainring and 23T rear freewheel DD hub bike as a Hillclimber, but it won't be done until September.

    So what do you guys think we should do in the challenge? Measure power consumption? Acceleration on flat and steep terrain? Measure motor temp? Gr8fun mentioned "side by side comparison on efficiency, acceleration, trail and road. Comfort and driveability."

    Let's get some more people to join in. The more, the merrier.

    Does anybody have any predictions about the results?
    Last edited by commuter ebikes; 06-21-2017, 10:47 AM.

    #2
    This is going to be great fun! We need to know what both of you are bringing to the shootout before we can predict of course.

    Comment


      #3
      Trek 26" singletrack frame hardtail.

      Other than that components from 12 bikes. And new.

      Sturmey igh hybrid hub. 3 soeed internal 1/3 overdrive 1/3 underdrive and straight through. Modified 7 speed cassette only using 5 cogs. 11 to 32. Front rings52 and 38. 30 speeds.

      front mechanical disk rear rim brakes.

      1.9 inch town and country tires thorn resist tubes

      Front suntour suspension

      750 watt bafang mid drive

      20 ah pf cell triangle pack.

      front fairing.

      Weight 130 lbs.

      Bike weight on weigh in. As well as rocks in the panniers to equal competition.


      8 mile road course flat equal speed for economy. One run at 20 mph. Way back 25 mph.
      run again switching riders.

      Other competitions as agreed upon.

      Comment


        #4
        Lets let this play out for suggestions from others.
        this sunday not good.

        But sounds good to me.

        Comment


          #5
          Originally posted by OptimusPrime View Post
          This is going to be great fun! We need to know what both of you are bringing to the shootout before we can predict of course.
          This is my bike: http://www.commuterebikes.com/

          Excerpt:

          -Design Logic fat tire cargo frame (190mm dropouts, 44mm head tube)
          -Zelena Vozila Cromotor with custom wide axles (268mm axle length, 190mm dropouts)
          -Vee Tire Snowshoe 2XL tires (31.5" X 5.05")
          -Surly Clownshoe rim in front, Rolling Darryl in rear
          -Lyen Mark 2 10kW 4110 controller set to maximum phase and battery current, optimized for 72V, maximum regenerative braking and 3 speed switch set to 33/66/99
          -Electric Rider 20Ah 72V LiMn battery with 100A BMS
          -Surly Ice Cream Truck fork with 150mm through axle
          -Tektro Dorado HD-E710 hydraulic disc brakes with 203mm rotors front and rear
          -Topeak Drybag panniers and trunk bag
          -Grin Tech Cycle Analyst V3 with motor temperature sensor
          -Surly Mr. Whirly crankset with 58T chainring and 14-28 5-speed freewheel
          -Extreme tire liners
          Last edited by commuter ebikes; 06-22-2017, 07:54 AM.

          Comment


            #6
            Gr8fun and I have a 110 pound weight difference between us, but he was gracious enough to allow my heavy self to ride his bike. We are going to do several runs, side by side, on each other's bikes and compare the Wh/mi values. I consume 65 Wh/mi on my daily commute.

            This issue of what is better, a hub motor or mid drive motor, may depend on the application. Obviously, if one is going MTB on steep trails, one would choose a mid drive. I designed my bike for flat city streets. It is perfect, except when I get a flat in the rear it takes two hours to remove and replace the tube and tire slime. Personally, I could never use a mid drive because I am so paranoid about problems with LE that I need to hide all of my electronics (except the display).

            I have actually had LE slow down and look at my rig. I slowed down and continued pedaling. So far, the officers have all gone on their way after looking at the bike. Using a helmet, helmet cam, reflective vest, headlights and tail lights as well as obeying all of the traffic rules all the time definitely helps. I would like to think that the LE moved on because they didn't see a motor, but I can't know what they were thinking.

            Clearly mid drives win on the issue of weight distribution and ease of changing a flat tire.

            I have heard about chain breakage, but I don't know how much of a problem this actually is. Using a quality chain and carrying a spare chain and tool seems like easy insurance against this problem, assuming this problem actually exists.

            Tearing apart and reassembling a hub motor is very straightforward if you have a hydraulic press (can be purchased for under $100), large and small bearing pullers (as low as $75 for both) and snap ring pliers. Looking at the component pieces of a DD hub motor, it sure seems to be a straightforward, even elegant, design. I have never taken apart and reassembled a mid drive. Is it straightforward?

            I have heard about the nylon gear in the BBS, but I have no experience with it. I imagine that it is composed of nylon so that it fails before some other (more difficult/expensive to replace) part? I imagine that one can keep a few spare nylon gears on hand and just remove and replace if needed?

            Having the controller right next to the motor, which will get hot, makes for a more simple, compact design but it may come at the expense of higher controller temperatures. I like an external controller because it will be installed away from the motor heat. I only need an 18 FET controller, but I use a 24 FET controller in order to better manage controller heat. I also use a heat sink for the controller. I don't know how many FETs are in the mid drives.

            For those who want to go fast, it would seem that both mid drives and hub motors have both high voltage and high current options.

            As far as motor cooling goes, a hub motor can have holes drilled in the side covers or Statorade (ferrofluid) installed. When I had a motor temp problem, I just went to a wider magnet. What are the best ways to cool a mid drive motor, or is this a nonissue?

            Mid drives score a huge win in the gear option. Gr8fun has a 3-speed IGH, 7-speed cassette and two chainrings. You're not getting those with a rear hub motor! I only have a 5-speed freewheel.

            If mid drives were ever to be shown superior to hub drives, I think it would come down to gearing options! I suppose a hardcore hub motor fanboy could argue for a front hub motor, but I wouldn't do that because I would require front panniers in order to hide the front hub motor. I would not even want to think about where the controller and battery go in this case not to mention the handling with all of that weight in the front. I wouldn't want to build or ride that bike.

            Hub motors have a slightly easier process for removing and replacing a faulty controller.

            Mid drive motors have a much easier process for removing and replacing a faulty motor in that a hub motor has to be laced and trued.

            Maybe mid drive vs. hub motor is like coffee vs. tea or Coke vs. Pepsi. Both are good and it is just a matter of personal taste. Many people like both!
            Last edited by commuter ebikes; 06-22-2017, 08:55 AM.

            Comment


              #7
              Here is my vote: unless you need to hide your motor, choose the largest mid drive motor available running at 72V, limit the current so as to keep the motor and controller temps down, use a CA V3, highest quality chain and cells, and a 100A BMS. Carry a spare chain, chain tool, tube and pump, and exploit the wide spectrum of gearing.

              Comment


                #8
                Originally posted by Gr8fun View Post
                ...front fairing...
                ...As well as rocks in the panniers to equal competition...
                +1 on the fairing

                I can't bear to put 110 pounds of rocks in your panniers so let's just switch riders.

                Comment


                  #9
                  We met up and went on our ride. After 5.17 miles (each guy riding a bike half of the time), the hub motor consumed 3.382 Ah and the mid drive consumed 3.249 Ah. Our maximum speed was 35.1 mph, and our average speed was 22.3 mph during 13:52 of riding. I am still in the process of editing the video, although Gr8fun may post a link to the complete, unedited footage.

                  I have reason to believe that my speedometer is reporting my speed too high.
                  Last edited by commuter ebikes; 06-22-2017, 11:44 PM.

                  Comment


                    #10
                    Wow! Two completely different bikes yet almost identical rates of consumption. You really busted the myth of mid motor efficiency.

                    Did you do any other comparisons?

                    Comment


                      #11
                      Originally posted by OptimusPrime View Post
                      Wow! Two completely different bikes yet almost identical rates of consumption. You really busted the myth of mid motor efficiency.

                      Did you do any other comparisons?
                      Just for my clarification, the voltage on the hub motor was 72 Volts and the one on the mid-drive was ??? volts? If different, the Ah consumption is interesting, but Watt-hours would be the more relevant comparison if we're discussing efficiency. For example 3.382 Ah at 72V is approximately 245 Watt-hours while 3.249 Ah at 52V (guessing here) is about 170 Watt-hours. Also a test that involved some uphill would be interesting where the mid-drive rider could use the gears to improve efficiency.

                      Comment


                        #12
                        Good point about the voltage difference, Ah and Wh.

                        Him and I are going to go out many more times in order to compare efficiency on different terrain, including hills.

                        Comment


                          #13
                          Originally posted by commuter ebikes View Post
                          Good point about the voltage difference, Ah and Wh.

                          Him and I are going to go out many more times in order to compare efficiency on different terrain, including hills.
                          Please keep posting the results. It is very interesting to see how the 2 compare.

                          Comment


                            #14
                            Yes, I'm very interested to see performance comparisons on hills.

                            Comment


                              #15
                              Here is completely the unedited video of me meeting Gr8fun, talking, riding and talking some more: https://youtu.be/ewfw5FrgRH8

                              I expect that one would skip through much of the video. Sorry that I don't have time to edit it.

                              More data:

                              After 2.66 mi of my 240 pound self riding the hub motor bike with very fat, heavy tires at 19 psi :
                              hub motor consumed 1.62Ah with an average of 47.7 Wh/mi and getting back 6.3% in regen
                              hub motor max current 40.9A, min voltage 70.8V, max current 40.9A but I have the current limited to 34A so 40.9A was a measurement from an interval smaller than 0.2 seconds.
                              hub motor max power 75 X 34A = 2550W.

                              We both had an average speed of 21.7 mph and max speed of 35.1 mph.

                              After 2.66 mi of Gr8fun (weighs 130 pounds) riding a BBS02 mid drive motor on medium tires with thorn proof tubes at 50-60 psi:

                              mid drive consumed 1.32Ah with a minimum voltage of 52V, 13.3A max current, max power 1320
                              ----------------------------------------------------------------------------------------------------------

                              After 5.17 mi where we had each ridden each bike 50% of the time:

                              fat tire/hub motor: consumed 3.382 Ah, ending motor temp 70.4 C, max current 52.5A but remember I have my current limited to 34A so the 52.5A is just a blip, min voltage of 65V, 50.4 Wh/mi, 268.43 Wh consumed.

                              We both had a max speed of 35.1 mph and an average speed of 22.3 mph during 13:52 of riding.

                              mid drive consumed 1.929 Ah with my 240 pound self riding the same distance that it consumed 1.32 Ah with the 130 pound rider for a total of 3.249 Ah consumed.

                              Gr8fun will probably come in and add some of his mid drive data.
                              Last edited by commuter ebikes; 06-23-2017, 10:33 AM.

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