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front and rear wheel hub motor questions?

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    front and rear wheel hub motor questions?

    Can someone explain something to me, If you have a 500 watt hub motor in the front wheel and another 500 watt hub motor in the back wheel how does that equal 1000 watts. My belief is that if each motor is pulling 500 watts than you still only have 500 watts of power pulling you. I can understand more traction but can't understand more power.
    I realize that a 500 watt motor is capable of pulling allot more watts but what I can't figure out is that folks tell me that two same size motors double your power and my thoughts are weather you have one 500 watt motor or 5 motors you still only have 500 watts.

    Another question I have is when I ride thru the woods going to my treestand hunting I'm usually only going 5 mph or less at times, at that speed it's hard for me to keep the front wheel straight so I constantly steering from side to side. If I had a front and rear hub motor pulling at the same time wouldn't that front wheel be pulling me sideways when my steering isn't perfectly straight?

    Just a couple thoughts I have about the new duel hub motors being offered by several bike companies today and both questions I cannot logically answer to myself. Thanks in advance.,

    #2
    When climbing a hill, the front wheel with a hub motor will get very little traction (off road, on trails).
    The two 500w hub motors will provide as much power as a single 1000w motor theoretically.
    The disadvantage is two throttles, two battery sets, two controllers, etc.
    -I suppose you could operate one motor by throttle and the other motor by PAS only.
    "I need another SimuLatte"

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      #3
      Originally posted by bohunter View Post
      Can someone explain something to me, If you have a 500 watt hub motor in the front wheel and another 500 watt hub motor in the back wheel how does that equal 1000 watts. My belief is that if each motor is pulling 500 watts than you still only have 500 watts of power pulling you. I can understand more traction but can't understand more power.
      I realize that a 500 watt motor is capable of pulling allot more watts but what I can't figure out is that folks tell me that two same size motors double your power and my thoughts are weather you have one 500 watt motor or 5 motors you still only have 500 watts.

      Another question I have is when I ride thru the woods going to my treestand hunting I'm usually only going 5 mph or less at times, at that speed it's hard for me to keep the front wheel straight so I constantly steering from side to side. If I had a front and rear hub motor pulling at the same time wouldn't that front wheel be pulling me sideways when my steering isn't perfectly straight?

      Just a couple thoughts I have about the new duel hub motors being offered by several bike companies today and both questions I cannot logically answer to myself. Thanks in advance.,
      When both motor are drawing 500watts, the total draw IS 1000watts. But not necessarily from the same battery/controller etc (which would be ideal).
      The power is cumulative.

      Think of a Jumbo Jet with 4 engines. The total thrust is the combined thrust of all 4 engines.
      Similarly, rockets also work that way with each rocket engine producing it's own thrust but the total thrust on the body of the rocket equal to the combined thrust of all of them.
      The Saturn V rocket produced a total of 5 million pounds of thrust, but no single engine produced that much alone.

      Hope that helps.

      Comment


        #4
        The few dual motor ebikes I have briefly ridden don't pull or feel different. Admittedly they don't have 1,000+ watts on the front.

        You may want to watch Micah's discussion on dual motors here. No dual throttle needed -

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          #5
          Yeah, two controllers for sure but no reason both or either one cadence sensor and throttle can't connect to both

          I'm not so sure why if the front wheel is delivering PF(G) watts to the ground and the other PR(G) watts to the ground it wouldn't be applying a total PTOT(G) = PF(G) + PR(G) watts to the ground (frankly certain that it does)

          However how efficient it is would be another story so the amount of power coming from the battery is a different discussion - you didn't mention what kind of motors (e.g. geared or DD) so won't dive into efficiency too much but clearly it will require more power from the battery than gets delivered to the ground (PTOT(G) = η × PBATT)

          Handling and stability is a different animal... the side to side comment sounds as though it's not stable at low speeds and there are many factors that could affect that including the proportion of power supplied to the front wheel. I'd try setting the controllers with different proportions of power going to the front and rear wheel to see how it affects the handling and stability since that's an easy variable to isolate

          Another easy variable to isolate is tire pressure and that also has a big effect on stability - my experience is that lower pressures (larger contact patch) tend to be more stable but there's no hard and fast rule

          The weight from the very heavy hub motor on the front wheel is likely a big factor that almost can only hurt handling, very hard to how it see how it would ever help but as long as it is present nothing much can be done

          Rake (fork angle) and trail (distance the center of the wheel contact path is behind the steering axis projected to the ground) have huge effects too - only way to readily change those is different fork unless you have a rear suspension and those play strongly with those factors

          Fork and frame flex also contribute


          Personally I think the benefits of two motors on a lightweight electric bike are outweighed by the penalties in nearly all use cases - frankly I think front hub motors only have very limited appropriate applications but that's a different discussion I suppose and I have a bias to mid-drives on light weight bikes regardless
          Last edited by AZguy; 12-30-2021, 07:58 AM. Reason: fixed the first sentence (can → can't)

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            #6
            Someone explained it in simple terms to me and it made allot of sense, If you had one horse pulling a cart you'd have one horse power but if you had two horses pulling the same cart you'd have 2 horse power.

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              #7
              Recently added a front wheel hub motor and it is a pleasure to have.
              Just one battery.
              Each has it's own controller,
              Original rear hub has PAS,
              New front motor is throttle only using a separate throttle..
              I use the front motor as a boost, had a hill climbing contest with daughter on her 750 watt new Radrover on a moderate hill no pedaling,
              both of us at full throttle doing perhaps 10kph, my two 250watt motors pulled equally to hers, not sure what would happen at steeper or faster but will have lots of time this summer to find out.

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