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Mono

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Mono last won the day on November 19

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About Mono

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    Western Europe
  • EUC
    InMotion V8, retired: Gotway MCM2s, IPS 132

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  1. Does the motor really push on the tire to drive the wheel?
  2. yes, good catch, if the lean angle is zero (no acceleration, negligible airstream), the pedal height has zero(!) effect on the thrust. Not necessarily what I would have expected...
  3. yes, it should, I was too quick to adopt the terminology which turned out to be wrong
  4. ooups, I found a (much) simpler expression for the forward thrust under a stationary lean as thrust [kg] = weight x (horizontal displacement + tan(lean) x vertical displacement) = weight x (horizontal distance between axle and force vector) where the displacements refer to the forward and down position of the point of attack away from the axle, relative to the wheel radius. Whhaaat? wow Checked it twice... still only 75% convinced.
  5. Quite cool device, this speedboard, but the noise I find a little bit annoying.
  6. Excellent decision, IMHO...
  7. Next up: the influence of pedal height under acceleration (or breaking). The disclaimer first: I consider low pedals as a significant safety risk. Getting caught with the pedal or foot is a reasonably common and wicked reason for crashes. I personally require at the very least 13 cm ground clearance to be on a reasonably safe side. When the force vector is vertical (green cases), the pedal height has zero effect on the torque (the white bar is unaffected by vertical shift). That was easy What happens under acceleration, that is, when the force vector is tilted (red cases)? We have thrust [kg] = weight / cos(tilt angle) x effective leverage / outer wheel radius and the leverage increases with increase tilt angle if the pedals are below the axle and increases even more the lower the pedals are. This looks like a significant effect, which should be further quantified. For example, without any forward displacement, the thrust is sin(tilt angle) x (distance to axle / radius) x weight / cos(tilt angle) = tan(tilt angle) x (distance to axle / radius) x weight where distance to axle is the (vertical) distance between axle and the point of attack and is negative if the axle were below the attack point. Without forward displacement, lowering the pedals by 10% of the wheel radius (2cm on a 16" wheel) at a lean angle of 10º adds for an 80kg rider 1.4kg thrust. As a reference, a 2cm forward displacement of the CoG at a lean angle of 0º and otherwise same setting adds 8kg thrust. I am not sure yet how much a forward displacement exactly influences the effect of pedal lowering, though it looks like it reduces it to perceivably smaller values.
  8. needs to read: 6) if the pedals do not tilt back... I also was mistaken that tiltback in general improves pedal support under braking. This is only true with extreme lean angles and high pedals, otherwise the effect is reversed
  9. I just checked the terminology. Moment arm and lever arm are crucially not the same The force is by definition perpendicular only to the moment arm.
  10. Agreed, that would be a firmware effect. I still don't know whether this effect is of perceivable size though. Pedal softness in itself of course is.
  11. I don't understand what "ease of leaning" would mean, and/or what it physically relates to other than what @mrelwood suggested, that is, to my understanding, "automatically" falling forward due to lack of pedal support. The effect size of this "automatic" falling should be easily quantifiable as a function of starting lean angle and time without support?
  12. Yes, that's what I would like to understand better. Interesting point. Pretty weird that a delayed reaction of the wheel shall increase its zippiness. I do see the mechanism of the idea though. That's not happening by the wheel controller, I am pretty certain. Of course a rider can do this actively, but that doesn't differentiate different wheels. I guess we should check how large this effect can actually be and which parameters are involved. That doesn't look too difficult. For example, how long does it take to increase 1cm displacement to 1.5cm assuming no pedal support? (My first estimate suggests that 10mm become 10.1mm after 0.1s, but I might have messed up something in the calculation). yes I still wonder whether there are other candidate explanations for how a softer mode improves the perception of zippiness.
  13. If the force vector is tilted, this COP shift can be zero or even negative, while we still produce positive torque. That's why it does not look like a suitable measure to me.
  14. The software is bound by keeping the pedals level. That is almost all there is to it. It cannot decide to accelerate slower, because then the rider would immediately fall off the wheel. It does influence the riders decision by using tiltback, but quite rarely during acceleration. I have two more: 6) if the pedals do not (EDITED) tilt back one may be in danger to slide off the pedal, because the force is by no means close to 90º to the pedal surface anymore. Also this needs to be checked depending on the geometry: tilt back could lead to slightly more pedal support by extending in effect the pedals away from the axle (maybe not likely though). 7) High pedals have less added leverage from deceleration during a strong backwards leaning than low pedals. (That may also go as another aspect of zippiness). As above, there is not much choice for the software: it has to keep the pedals level, or maybe better slightly tilted. That's all it can do.
  15. Inspired by this comment and by this video I updated the original figure adding a 15º inclination line. I started to figure that a major part of zippiness may be that small (forward-backward) weight displacements lead to large effects. I guess I am not the first one Effect size per displacement is independent of the wheel power(!) but decreases with increasing wheel size. Let's look at some numbers. The weight displacement to get a certain desired thrust is proportional to the wheel size (and the rider weight). It is as simple as this: if I weight 80kg and want 8kg forward thrust, which is 10% of my weight, I need to displace my weight by 10% of the wheel radius forward. Stupidly simple. The same displacement on a 14"x2.125" wheel produces only 76% of the thrust on a 18"x2.5" wheel. In other words, on the bigger wheel we need a 32% (≈ 1 / 0.76 - 1) further weight displacement for the same thrust. 10kg added wheel weight reduces the effect of the thrust additionally by the factor 92 / 102 (assuming 12kg + 80kg to begin with). Combined, we need a 46% (≈ 1 / (0.76 x 0.9) - 1) further displacement on the bigger wheel, for example 4.4cm instead of 3cm to induce the same acceleration. All this does not depend at all on motor power or battery size or firmware tweaks or anything inside the wheel. Nice and simple and probably one relevant aspect of zippiness.
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