Ultra Tuning: Decoding the Voltage Section of Torque Tab

[ProphetZarquon]

First, thanks for the detailed reply!

As a quick Wikipedia check will show, the kilogram (kg) is the SI unit of mass, the Newton (N) = kg m/s² the SI unit of force, the Pascal (Pa) = N/m² the SI unit of pressure, and the Newton-meter (N m) the SI unit of torque.

Mass and force are 2 very different things. A typical digital scale measures weight W (a force) in N but reports mass M in kg using M = W / g, where g is some reference acceleration of gravity in m/s² baked into the scale firmware. Often this g is "standard gravity", with a value of 9.80665 m/s².

Likewise, to get a convenient index B of pedal force F, with B expressed in kg, you'd use something like B = F / g. The index would work as long as you used the same g every time.

Pedal pressure and pedal force are also 2 very different quantities. To get a pressure P from a force F, you use P = F /A, where A is the area over which F is applied in m².


Agree, an exponential progression of the max mechanical power or torque associated with each PAS level would feel more natural. The teeth on the cogs of a cassette grow roughly exponentially in the same way, and for the same reason.

(Not so) fun fact: The Kilogram is no longer based on a fixed mass (such as by measuring the prior samples in Moles, as was suggested), but instead is now measured via the force exerted within a specific known gravitational field; in the process, we've not only made Kilogram calibration now require a (proprietary) device adjusted for each region of the Earth (or space), but also if read very carefully the definition now contains circular logic.

We really should have gone with Moles, despite the drift involved.

 

[ProphetZarquon]

Sorry for being pedantic, but they don't really "stack," as in being additive. They're multiplicative, with the PAS providing an upper limit of power and the Torque/Voltage providing a percentage of that.


I've seen no differences in either between Eco and Sport. All those seem to do is choose which of the 10 levels is available to be selected. If you have all 10 enabled, then there's zero difference.


Bafang has moved on from this model of motor, has changed how their newer motors are programmed. It's unlikely we'll see any changes for the Ultra motors.

Eco & Sport have dramatically different run-on times; they're definitely not operating on the same scales.

 

[ProphetZarquon]

even if you can push to the full 60 kg limit

I weigh ~108Kg at a bit less than 'ideal' weight for my height; so, just standing on the front pedal maxes out the response on every torque sensing ebike I've tried. Generally I don't want to push anywhere near that hard, but when I am, it would be nice if the power assist could continue to scale with my efforts... It doesn't; not even on the new "high torque" motors.

I'm on the lookout for a higher range torque sensor module, to mod a new spline shaft sensor with; higher torque sensors exist, but aren't available integrated into the part I need, so some fabrication will be required.

Most stuff, especially including bicycles & ebikes, is still designed for regular sized people, with those who're excessively tall, or just overweight, left to cope with stuff that simply isn't designed to safely handle us. There was even a lawsuit, but the (very slightly above average height & presumably thought they knew about being 'tall') judge ruled that being far outside normal design specifications by height, does not count as a handicap the way being overweight etc does...

Anyway, yeah, I'm huge, so 60Kg feels like a relatively mild effort for me, but I've yet to find any workaround (other than shorter cranks to limit my force output! ).

 

[smorgasbord]

(Not so) fun fact: The Kilogram is no longer based on a fixed mass (such as by measuring the prior samples in Moles, as was suggested), but instead is now measured via the force exerted within a specific known gravitational field; in the process, we've not only made Kilogram calibration now require a (proprietary) device adjusted for each region of the Earth (or space), but also if read very carefully the definition now contains circular logic.

We really should have gone with Moles, despite the drift involved.

Here's NIST's take, with a ton of history:

Kilogram: Introduction

For more than a century, the kilogram (kg) — the fundamental unit of mass in the

www.nist.gov

 

[smorgasbord]

Eco & Sport have dramatically different run-on times; they're definitely not operating on the same scales.

Is this a set-able parameter, and if so, where?
Can you give us a situation or ideally an isolation test in which we can feel the differences?
And does it matter how many PAS levels one has set? For instance, I use all 10 levels (0-9), so Eco/Sport doesn't change those for me.

 

[ProphetZarquon]

Is this a set-able parameter, and if so, where?
Can you give us a situation or ideally an isolation test in which we can feel the differences?
And does it matter how many PAS levels one has set? For instance, I use all 10 levels (0-9), so Eco/Sport doesn't change those for me.

Excellent questions: The DPC-18 that came with our m620, is configured as PAS levels 0-5, with Eco & Sport apparently using each alternating PAS setting slot 0-9...
I see no settings to adjust what Eco VS Sport do, nor are the differences at all limited to the percentiles in those alternating slots: With them set identically between alternate slots, there's still a huge difference in assist level & a noticeable delay in cutoff, when switching to Sport.
In fact, I never use Sport at all, except as a 5+ mode when I just want to go as fast as possible down a straight road for a moment... because it isn't tuned right! (If I tune Sport to fade smoothly, Eco becomes limpy!)
Which display is used, ironically seems to have pretty significant effect on how motor-controller tuning settings are applied: Different displays, apparently offer different PAS setups?!? I would have expected that to be more a motor controller firmware thing, but of the firmware updates released, I haven't seen different firmwares per-display? Anyone had a display firmware change & if so did any PAS functionality change?

 

[ProphetZarquon]

Here's NIST's take, with a ton of history:

Kilogram: Introduction

For more than a century, the kilogram (kg) — the fundamental unit of mass in the

www.nist.gov

I read that back when it was happening, but their take, does nothing to change what I said: The Kg is now calibrated against itself & dependent on local gravitation, using proprietary machines to boot... For those reasons, I don't care who supports it, it's a bad definition.

 

[smorgasbord]

Different displays, apparently offer different PAS setups?!?

There was a post here a couple months ago where the poster said his Eco/Sport PAS levels were not alternating. I asked a follow-up question, but didn't get a reply.

The [definition of a] Kg is ... dependent on local gravitation

It's actually not. Maybe this video will help you feel better about it (especially the section starting at 7:30 where they use a gravimeter to measure gravity in that room, which apparently accurate enough to see variations based on the sun, moon, even the level of the water table underneath the basement:

As a practical matter, there will now be plenty of places creating Kg mass objects against which other things can be compared on a regular style balance. Apparently, the standards themselves had been losing weight over time when they compared them to each other. Micro-grams, of course, but such things matter for some things.