What determines wheel zippiness?

[Chriull]

1 hour ago, Mono said:

Very nice animation! I struggle to understand (the physical model of) what happens in the beginning.

Its just a very simple model solely based on the motor torque countering perfectky the riders "weight and inertia force" so the pedal stays straight.

1 hour ago, Mono said:

The behavior of the green ball falling forward suggests that the contact point was moved backwards,

 

1 hour ago, Mono said:

but I don't see that this happened, and I also do not see the wheel moving backwards as a result of this. In other words, how is the first acceleration of the system initiated?

The contact point plus the green ball is moved forward (should represent the rider leaning his cog a bit forward), so the motor has to counter this torque on the pedal to keep it straight and by this the wheel moved forward.

The leaning of the rider is always assumed to perfectly counter the mass inertia, so there is no torque affecting the rider.

[Mono]

1 hour ago, Chriull said:

Its just a very simple model solely based on the motor torque countering perfectky the riders "weight and inertia force" so the pedal stays straight.

I see, makes sense as it looks much more difficult to solve the equations otherwise. I guess it is worth to keep in mind then that the animation does not reflect how the rider can change the state of driving.

[Mono]

On 6/26/2019 at 7:32 PM, Chriull said:

A short description

Shouldn't the accelerating force from the tire on the road point in the opposite direction?

Edited July 5, 2019 by Mono

[Mono]

2 hours ago, Mono said:

A short description

Do you agree that the direction of the motor torque force vector is relevant only for how the torque is computed, but its effect on acceleration is independent of its direction? That is, the discrepancy in amount of motor torque and acceleration is only due to the torque vector to be closer to the center? It seems that the vector lengths are not proportional to their distance to the center though.

Edited July 5, 2019 by Mono

[Chriull]

2 hours ago, Mono said:

I see, makes sense as it looks much more difficult to solve the equations otherwise. I guess it is worth to keep in mind then that the animation does not reflect how the rider can change the state of driving.

Yes and no, if i understand you correctly. But by now my simple model has a fault (thanks for your statement)

The "contact" point is the representation of were the rider applies the force on the pedal. In reality (mostly) the full foot applies pressure on the pedal. Depending on the lean angle/position of the cog the pressure distribution changes. So this pressure distribution can be summed up to one "contact" point where the whole force is applied. This works out for this kind of physical modelling.

But i treated in the model the position of the "contact point" and the lean angle as two independent values, which they are not...

I set the "contact point" ("riders force attack point") as fixed specification (rider input to control the acceleration). Then calculated the necassary motor torque to counter the riders force on the pedal, which also acts on the road accelerating the wheel. From this acceleration results the riders lean angle (gravitation and inertia) so no additional torque is introduced by the rider

But this lean angle changes the "contact point", which i did not reflect in the calculations.

So my next iteration for this model will be to start with the lean angle/cog position as input and calculate the "contact point" from this.

2 hours ago, Mono said:

Shouldn't the accelerating force from the tire on the road point in the opposite direction?

As the motor applies an clockwise torque on the pedal to counter the rider "pushing" downwards, the torque on the wheel diameter has to be counterclockwise. So the force from this is pushing the road backwards. As the road does not move it pushes the wheel forward...

Maybe i have just choosen the wrong/an ambigous name for this force?

1 hour ago, Mono said:

Do you agree that the direction of the motor torque force vector is relevant only for how the torque is computed, but its effect on acceleration is independent of its direction? That is, the discrepancy in amount of motor torque and acceleration is only due to the torque vector to be closer to the center? It seems that the vector lengths are not proportional to their distance to the center though.

The motor torque (force) vector is orthogonal to the line through the tire axle/center. The value of this force is the projection of the (negative) riders force at this point. The acceleration is proportional to this motor torque.

So the acceleration is linked with the direction of the motor force vector, but not in a simple proportional way.

[Mono]

42 minutes ago, Chriull said:

Yes and no, if i understand you correctly. But by now my simple model has a fault (thanks for your statement)

The "contact" point is the representation of were the rider applies the force on the pedal. In reality (mostly) the full foot applies pressure on the pedal. Depending on the lean angle/position of the cog the pressure distribution changes. So this pressure distribution can be summed up to one "contact" point where the whole force is applied. This works out for this kind of physical modelling.

agreed.

42 minutes ago, Chriull said:

But i treated in the model the position of the "contact point" and the lean angle as two independent values, which they are not...

I think they are independent in reality (up to some dependent boundaries).

42 minutes ago, Chriull said:

I set the "contact point" ("riders force attack point") as fixed specification (rider input to control the acceleration). Then calculated the necassary motor torque to counter the riders force on the pedal, which also acts on the road accelerating the wheel. From this acceleration results the riders lean angle (gravitation and inertia) so no additional torque is introduced by the rider

This seems to contract the paragraph before: here you seem to say that you don't treat the lean angle as independent from the contact point, but derive it from the contact point to get a stationary system. That seems about right to me.

42 minutes ago, Chriull said:

But this lean angle changes the "contact point", which i did not reflect in the calculations.

So my next iteration for this model will be to start with the lean angle/cog position as input and calculate the "contact point" from this.

I don't see that this is necessary as long as you don't consider the system to be dynamic. In a stationary system it seems to me that you don't have the degree of freedoms to decouple lean angle and contact point, but I could be wrong 

42 minutes ago, Chriull said:

As the motor applies an clockwise torque on the pedal to counter the rider "pushing" downwards, the torque on the wheel diameter has to be counterclockwise. So the force from this is pushing the road backwards. As the road does not move it pushes the wheel forward...

Maybe i have just choosen the wrong/an ambigous name for this force?

Right, but to consider the horizontal force on the road seems not really relevant to me, better consider the force on the wheel, no?

42 minutes ago, Chriull said:

The motor torque (force) vector is orthogonal to the line through the tire axle/center. The value of this force is the projection of the (negative) riders force at this point. The acceleration is proportional to this motor torque.

So the acceleration is linked with the direction of the motor force vector, but not in a simple proportional way.

Still, given we have computed the torque vector based on the riders weight force, computing the resulting horizontal (torque) force should be straight forward, namely proportional to the distance to the center, am I missing something? It doesn't look like it in the animation.

[Chriull]

12 minutes ago, Mono said:

Still, given we have computed the torque vector based on the riders weight force, computing the resulting horizontal (torque) force should be straight forward, namely proportional to the distance to the center, am I missing something? It doesn't look like it in the animation.

Ups - did get your question wrong before. Yes, the direction does not matter - the forces are invers proportional by the distance to the tire center. Maybe it looks not right in because of the white casing beeing off this center.

[Mike Sacristan]

I see now why you guys commented my FW 1.07 thread as if an EUC was entirely rigid and as if a rider was a stick without ankles. The animation say's it all. 

Perhaps we can discuss further here then as you guys invested in doing quite a few calculations. Maybe tag @Aneta as well.

The last thing being discussed in my FW 1.07 firmware thread was if pedal decline would make hill climbing harder or easier.
And the thing before that was if 12mm forward foot placement would allow a 55kg rider to exert as much force as a 85kg rider.

When riding a EUC what we want to do is use force to rotate the wheel.
If a huge tractor tyre was lying down on the ground how would you rotate it 10 degrees clockwise?
Would you turn it by the middle? Or would you turn it by the edges?
If you could place a huge handle on it and twist the handle to twist the wheel.. where would you place the handle?
Closer to the center of the tyre or further from the center?

Regarding pedal tilt and climbing (or even acceleration for that matter):

While climbing very steep inclines we already end up on our toes because we run out of ankle mobility (dorsiflexion).
So basically we run out of lean.
Using backward tilted pedals would put us on our toes sooner.
Using forward tilted pedals would put us on our toes later.

Go squat on an incline and let me know how that goes. 
Please film it!
Then maybe we can reinvent weight lifting shoes with a reverse heel.

Btw... wearing high heels also makes hill climbing and accelerating easier.

Here is another funny thing actually related to the 16X FW1.05 hard mode.
It is more "springy" than the FW1.07 medium mode. So it had more play back and forth. If I braked or accelerated heavily in FW1.05 hard mode I could make the trolley handle vibrate quite loudly.
I can make the trolley handle vibrate with 1.07 medium mode but not as much as it did in 1.05 hard.
 

 

[Mono]

Summarizing what I gathered from the parallel thread: the induced torque is simply proportional to the riders weight and to the horizontal displacement of the riders CoG to the wheel axle (distance of the point of attack to the axle times sinus of the angle between this point and the weight force vector). That's nice and simple! That means, tilting the pedals in itself doesn't have any immediate effect – besides moving the sole and hence moving the point where the sole supports the CoG  Tilting the wheel back moves the pedal projection to the front which in effect elongates the pedal to the front for more potential leverage (which may not be feasible, because the ankle cannot tilt as much as the pedal).

[Chriull]

1 hour ago, Mono said:

Summarizing what I gathered from the parallel thread: the induced torque is simply proportional to the riders weight and to the horizontal displacement of the riders CoG to the wheel axle (distance of the point of attack to the axle times sinus of the angle between this point and the weight force vector). That's nice and simple! That means, tilting the pedals in itself doesn't have any immediate effect – besides moving the sole and hence moving the point where the sole supports the CoG 

The torque the rider weight "produces" is the vector product of the weight force times the vector from the axle to the "force attack point on the pedal"

So by tilting the pedal the angle between this two vectors and the vector from the axle to the attack point changes. If one keeps staying "on the pedal tip" while tilt back the by the riders weight induced torque increases (a bit).

The force by the riders inertia while the wheel accelerates him (a "horicontal" force) which the rider "applies" against the pedal so he does not fall backwards from the wheel increases the torque, too. (The axle -attack point vector times this force is normaly not zero)

Beside this "static" considerations the rider can de/increase the vertical force by crouching/standing up (fast enough to have a noticable effect).

Same for going over bumps/"holes".

If while leaning forward while an acceleration one crouches/bends his knees so one does not stem ones inertia against the wheels acceleration while keepibg the weight force on the pedal (if such a move is in reality possible?!) this could be (a part of) your proposal for trying to overcome an overlean. (Letting the wheel getting under one again by releasing sone force, but keep it acceleration)

 

[Aneta]

So, today I tested my theory on slopes ranging from 15 to 25%. And... it totally works!!! Surprise? Nope, fully expected, as it's nothing but simple physics. When calibrated at a perfect angle with pedals tilted up, going up a steep slope just feels like you're standing on an escalator in subway - your feet are perfectly horizontal and there's absolutely no effort, no Herculean push on the toes needed. Likewise, going down a steep slope with pedals calibrated tilted down does not require Herculean push on the hills.

When going up/down 15-20% slopes (8-11 degrees), I found the tilt of 6-8 degrees the most comfortable. If the tilt was equal to the slope angle, it was too much. I guess, we can try to derive the "perfect angle" as a formula, but it's easy to empirically find it.

I'm definitely adding this trick to my "bag". It doesn't make sense to do it on short slopes (50-100 meters), but long and steep one, like that ski slope in Mike's video, it makes sense, especially if it doesn't require an app to calibrate and takes the whole of 10-15 seconds, like on my GT16. This premium feeling of climbing in total comfort and with no effort whatsoever makes you feel like a Padishah being carried by the slaves who maintain the perfect level of their master no matter the terrain.

[mrelwood]

3 minutes ago, Aneta said:

So, today I tested my theory on slopes ranging from 15 to 25%. And... it totally works!!!

 

3 minutes ago, Aneta said:

your feet are perfectly horizontal

Isn’t this sentence contradictory to your theory in the first place? That the added leverage and torque would be introduced by the pedals being located further forward from the axle when calibrated to a backwards tilt. If the pedals stay flat, you haven’t really tested the theory you proposed, have you?

If the theory was just that ”it would be easier for Aneta to...”, then cool, but the explanation still doesn’t hold water. There could be many other reasons for that. Like the calibration just compensating for a softer riding mode, or you naturally standing more forward when the pedals are angled back (I do too), etc.

[Aneta]

2 hours ago, mrelwood said:

Isn’t this sentence contradictory to your theory in the first place? That the added leverage and torque would be introduced by the pedals being located further forward from the axle when calibrated to a backwards tilt. If the pedals stay flat, you haven’t really tested the theory you proposed, have you?

No, I don't understand. If I calibrated the pedals be 7 degrees up and they feel flat when going up the slope, that means they rotated back 7 degrees from their "zero throttle" position and are providing throttle amount sufficient to go up 20% slope. I'm confused by the existence of this very confusion, I'm trying to explain very simple thing and fail. I'm terrible at explaining stuff.

PS. No, I'm placing my feet exactly as on level surface. At the bottom of slope, on level surface, it does feel weird to stand on tilted pedals, once I hit the slope, the feeling is just like you stand on an escalator. Effortless.

Edited December 12, 2019 by Aneta

[Chriull]

42 minutes ago, Aneta said:

No, I don't understand. If I calibrated the pedals be 7 degrees up and they feel flat when going up the slope, that means they rotated back 7 degrees from their "zero throttle" position and are providing throttle amount sufficient to go up 20% slope

Then the wheel has quite some soft mode. 7° pedal tilt is quite much. Maybe some "special" firmware mode for (long) lasting heavy burdens?

As going up a steep incline mostly comes with low speeds and high motor currents this "softness" maybe comes from some power/current limiting?

On a straight road while accelerating a 7° forward tilt of the pedals would be very special/unacceptable!

 

[Aneta]

43 minutes ago, Chriull said:

Then the wheel has quite some soft mode. 7° pedal tilt is quite much. Maybe some "special" firmware mode for (long) lasting heavy burdens?

As going up a steep incline mostly comes with low speeds and high motor currents this "softness" maybe comes from some power/current limiting?

On a straight road while accelerating a 7° forward tilt of the pedals would be very special/unacceptable!

 

I believe mine is in "Play Mode" in Rockwheel app, which I think is the hardest mode, I'll double check tomorrow.

But I don't understand this Berlin Wall between my results and @Mike Sacristan's which he described here:

On my GT16, "it just worked", on his wheel "it just didn't work". Why such a difference?

I don't think the hardness of the pedal "throttle" is of any principal importance, because it's just the scaling, a multiplier between pedal angle and PWM level, perhaps nonlinear, but that's inconsequential.

Edited December 12, 2019 by Aneta

[mrelwood]

1 hour ago, Aneta said:

No, I don't understand. If I calibrated the pedals be 7 degrees up and they feel flat when going up the slope, that means they rotated back 7 degrees from their "zero throttle" position and are providing throttle amount sufficient to go up 20% slope.

I do have a language barrier to cope with, but to me what you have explained sounds clear. Did I understand wrong:

1: Flat calibration, not moving.

2: Tilt calibration, not moving.

3a: Tilt calibration during an incline.

3b: Tilt calibration during acceleration on flat ground.

If this is the case, I suggest you try the same with a hard riding mode. The result should be quite different.

[mrelwood]

2 minutes ago, Aneta said:

On my GT16, "it just worked", on his wheel "it just didn't work". Why such the difference?

Two persons of random skillsets on the opposite side of the globe explaining with a few phrases how they physically feel while executing a complicated physics phenomena... What could go wrong! 

Either the other (or both) has misunderstood something in the preparation of the test, or one of you just experiences the riding situation differently. Quite simple really.

[Aneta]

3 minutes ago, mrelwood said:

I do have a language barrier to cope with, but to me what you have explained sounds clear. Did I understand wrong:

1: Flat calibration, not moving.

2: Tilt calibration, not moving.

3a: Tilt calibration during an incline.

3b: Tilt calibration during acceleration on flat ground.

If this is the case, I suggest you try the same with a hard riding mode. The result should be quite different.

I don't understand. Tilt calibration during incline or acceleration - is that possible on any wheel? (even if it were, I don't have balls to do calibration while moving)

I did calibrations while not moving, by placing the phone with Clinometer app on the pedal and controlling the angle. Holding the wheel steady with pedals at 7 degrees up, I pressed the power button for something like 8 seconds until the wheel indicated with long beep that calibration is done.

[Chriull]

3 minutes ago, Aneta said:

But I don't understand this Berlin Wall between my results and @Mike Sacristan's which he described here:

You use different wheels (firmwares/available "power") and possibly have a different stance/riding technique/"ankle flexibility". So a bit different results are not puzzling?

And Mike stated that a slight tilt calibration was helpfull and such reports were already posted here often (afair). So "everything" goes in the same direction.

Just you with your wheel prefer a higher tilt angle and your pedal seems to tilt back to horizontal position under load. Such a "small" deviation i would not call a Berlin wall...

[mrelwood]

2 minutes ago, Aneta said:

I don't understand. Tilt calibration during incline or acceleration - is that possible on any wheel?

Not executing the calibration while riding, but riding with the tilted calibration.

 

[Aneta]

Just now, mrelwood said:

Two persons of random skillsets on the opposite side of the globe explaining with a few phrases how they physically feel while executing a complicated physics phenomena... What could go wrong! 

Either the other (or both) has misunderstood something in the preparation of the test, or one of you just experiences the riding situation differently. Quite simple really.

Physics is different in America and Sweden, perhaps? I know it's diametrally opposite in @The Fat Unicyclist's whereabouts, where even gravity is pulling the oposite way!

[mrelwood]

 

1 minute ago, Chriull said:

And Mike stated that a slight tilt calibration was helpfull

Mike preferred a tilt in the opposite direction, forward. Aneta prefers a tilt backwards.

 

[mrelwood]

1 minute ago, Aneta said:

Physics is different in America and Sweden, perhaps?

Understanding, observing and explaining physics are all different and unique skills for everybody.

 

[The Fat Unicyclist]

10 minutes ago, Aneta said:

Physics is different in America and Sweden, perhaps? I know it's diametrally opposite in @The Fat Unicyclist's whereabouts, where even gravity is pulling the oposite way!

Yep.. And when you ride upside-down, stopping the wheel cavity filling up with stones and other flotsam is a daily challenge!   

[Aneta]

18 minutes ago, Chriull said:

You use different wheels (firmwares/available "power") and possibly have a different stance/riding technique/"ankle flexibility". So a bit different results are not puzzling?

And Mike stated that a slight tilt calibration was helpfull and such reports were already posted here often (afair). So "everything" goes in the same direction.

Just you with your wheel prefer a higher tilt angle and your pedal seems to tilt back to horizontal position under load. Such a "small" deviation i would not call a Berlin wall...

My understanding is that the angle of the pedals relative to "neutral" (calibrated) angle is the throttle input. It can be hard or soft - this is only a different multiplier between angle and throttle. What I am saying can be illustrated with this analogy: imagine you're riding an e-scooter up the slope. It takes certain rotation of the throttle lever. Now, you feel discomfort in your finger and decide that you want to go up without any effort. You recalibrate the lever so that at neutral position it sends the same signal to the controller as when you were pulling the lever. This is the same thing I'm doing - I recalibrated the throttle so that when going up, level pedals already provide the required throttle input, while I'm experiencing the same lack of any effort in my feet as if I was riding on a level surface at slow constant speed.

Edited December 12, 2019 by Aneta