Hi all :)

I’ve just bought a Vitesse Force ebike. It was second hand, but brand new as the previous owner bid on two separate auctions and won both (he’s someone I trust, so I believe him). Other than a few tweaks, the bike is great, but I want to make it even better if possible.

The main thing I want to change is the walk assist speed. As I understand it, in the UK we can’t have powered ebikes, they can only move very slowly when you’re not pedalling. I tested the speed yesterday, and on a slope it’s barely fast enough to stay upright.

The main reason that I bought an ebike is because I’m disabled and overweight, and live in the middle of a load of hills. I’m hoping to get the walk assist speed up just high enough to get me up a hill to the nearest flat cycle path so that I can ride, or home again afterwards if I’ve overdone it. For now I can’t pedal continuously for long enough to get to the top, and the pedal assist stops when I stop.

The other thing I’m curious about changing is the number of gears. The bike is a seven speed, but I’ve never used an ebike before, so I don’t know if that’s enough for when I want to turn the pedal assist off.

The bike is here for anyone interested:

https://www.gooutdoors.co.uk/16183641/vitesse-force-mtb-wm-electric-bike-16183641

I’d be grateful for any advice :)

  • @j4k3
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    8 months ago

    I know how to hack any of them externally to alter the top speed, but I think you’ll need a more advanced hack to pull off what you want to do here. I likely could still do it externally without altering the OEM controller circuit, but I would need some more advanced electronics to pull it off.

    Both the speed and pedal cadence sensors are likely just a magnet passing in front of a hall sensor. It is possible to add anything that will trick this sensor into thinking there is a magnet passing in front of it.

    You could make or 3d print an attachment to the crank arm (or wherever the pedal cadence sensor is located) - that has an additional magnet or few. This would cause the computer to think each pedal stroke is n × magnet strokes thereby reducing the ratio of effort to output all the time.

    If you only want the effect to alter idle operations, it would need to be a microcontroller that detects the conditions and pulses something like an wire coiled inductor on a powder core ferrite bobbin placed near the hall effect sensor. You would need a sensor to detect the same pulse from the magnet on the crank arm and another on the wheel to detect rotation.

    The code is not that complicated really, but debugging and eliminating potential noise sources would be pretty dangerous to prototype.

    This is all overkill hypothesis and rambling to hopefully help you see how the system works in general on a fundamental level. For most people, a mechanical hack like additional magnets is pushing their maker skills pretty hard.

    It is unlikely you are the first to have this issue and there is probably a much easier way. I’m interested in what others may say, so I commented to remember to watch this.

    • TipponOP
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      8 months ago

      Thanks for replying :)

      Yeah, everything seems to be aimed at increasing the top speed, which is fair enough, it’s what I’d normally want to do. Most people either don’t use walk assist, or only use it right at the beginning and end of their ride, and the speed doesn’t matter.

      I can change the size of the tyres in the settings, which should let me increase the bike’s speed, but I was hoping for a different solution first, rather than changing everything and throwing some of the data out. I might try that this weekend if the weather stays dry though.

      I definitely won’t be building advanced electronics though, that’s a bit beyond me these days :p