Torque topic

[mrelwood]

 

5 hours ago, Slartibartfast said:

So at the end of all this we have converged on the understanding that the apparent "zippyness" of different sized wheels is not related to torque as such but is related to the RPM range at which the motor most happily operates. Is that right?

You’d have to define what you mean by zippyness for the question to be perfectly clear. But in the discussions I’ve taken part in, zippyness has been used to describe the effortlessness of acceleration (Zip = Acc/Lean). In which case, no, it’s not related to the RPM range.

 No matter how inefficient an EUC is at any given RPM, it will always use the amount of power that is required to keep us upright. The RPM, gearing, efficiency, etc has zero effect in whether that happens or not (during reasonable accelerations and brakings). If the motor requires 50x the amps at 0mph to keep us upright, the controller will provide said amps.

 That’s why all this talk about gearing and theoretical RPM torque calculations, while interesting, has no practical effect in whether we stay upright or not, or how fast the wheel accelerates at any given situation.

 That’s what my earlier quiz questions were meant to bring up. I must be a lousy teacher since no-one returned the quiz!  Gearing, RPM, motor efficiency, max power, motor’s power rating, etc have no effect in zippyness (effortlessness of acceleration).

Edited November 3, 2022 by mrelwood

[Paul A]

Two EUCs.

Same Power.

Same Mass.

Same Torque.

__________________________________

 

Equation 1.

Force = Mass x Acceleration.     F = m x a

 

To achieve greater Acceleration, have greater Force.

___________________________________

 

Equation 2.

Work Done = Force x Displacement.    WD = F x d

Transpose formula to

F =  WD/d

 

The EUC with the smaller wheel. 

Will have smaller displacement.  (d)

Smaller Displacement (d) in the equation will mean greater Force (F)

 

Greater Force, is greater Acceleration, refer to equation 1.

[Slartibartfast]

On 11/1/2022 at 7:39 AM, mrelwood said:

 

 

5 hours ago, mrelwood said:

You’d have to define what you mean by zippyness for the question to be perfectly clear.

Was is not you who introduced the term "Zipyness" yourself back on the first page? I assumed you basically meant "amount of acceleration".

5 hours ago, mrelwood said:

That’s what my earlier quiz questions were meant to bring up. I must be a lousy teacher since no-one returned the quiz!

Sorry, I must have missed your quiz.

 

I know you asked:

On 11/1/2022 at 7:39 AM, mrelwood said:

A: They accelerated faster.

B: They were easier to accelerate fast.

But I would say they are pretty much the same. What exactly is the difference?

[mrelwood]

1 hour ago, Paul A said:

Greater Force, is greater Acceleration, refer to equation 1.

Although, in case of a self balancing vehicle "all else being equal" doesn't really apply as it's a constantly changing set of values. By calculating like that you only get the results for a single frozen moment in time. As acceleration requires the concept of time, you can’t disregard everything else that will unavoidably happen during that time.

38 minutes ago, Slartibartfast said:

Was is not you who introduced the term "Zipyness" yourself back on the first page? I assumed you basically meant "amount of acceleration".

It was, but that’s not what it refers to. But “effortlessness of acceleration”, which requires a value for system input as well, in this case the amount of lean.

 We all know that EUCs’ acceleration is controlled by the rider’s forward lean. Making calculations about acceleration while disregarding the number one factor that controls it sounds a bit futile.

38 minutes ago, Slartibartfast said:

Sorry, I must have missed your quiz.

I know you asked:

But I would say they are pretty much the same. What exactly is the difference?

So would you say that both of them apply, or neither of them apply?

Edited November 3, 2022 by mrelwood

[Chriull]

2 hours ago, mrelwood said:

We all know that EUCs’ acceleration is controlled by the rider’s forward lean. Making calculations about acceleration while disregarding the number one factor that controls it sounds a bit futile.

By now pads to increase lean possibilities are normal - as some years ago https://forum.electricunicycle.org/topic/14032-what-determines-wheel-zippiness/#comment-239217 it was normally limited by the pedal geometry.

But still the mechanics are unchanged - the rider by it's lean creates a torque. The EUC has to counter this torque, so the rider stays balanced. This countertorque acts as force on the road and by this accelerates the wheel.

Afair a real measure/differentiation for zippiness was not found in these times? But the mechanics are well understood.

 

[RagingGrandpa]

9 hours ago, mrelwood said:

zippyness has been used to describe the effortlessness of acceleration
Zip = Acc/Lean

That's perfect. "G per degree."

Impractical to measure, but useful as a concept.

Maybe we can define the Lean angle as an angle at the rider's ankle, i.e.: angle between the pedal and the person's lower leg.
0° Lean means a right angle (90) between pedal surface and lower leg.
20° Lean means 70 between pedal and leg.
(This assumes an upright body position with knees, waist, and arms straight. And a balanced foot placement with 0° lean giving no acceleration. And we're ignoring drag forces, so this should only be used as a 0-10mph concept.) 

Because this angle is relative to the pedal, not relative to the ground, the impact of firmware / soft mode on Zip becomes clear too.

Zip is a ratio, and is not concerned with the maximum lean angle or maximum acceleration value. To talk about maximums, use measurable things like pull force, freespin speed, battery current, and component temperatures instead.

  

9 hours ago, mrelwood said:

earlier quiz questions

Gearing: (if the tire size is not changed) Does not affect Zip, because Zip doesn't care how the acceleration's force was created. A small motor with a gear reduction, or a large gearless motor, can make equal force and achieve equal Zip.
RPM: Is a result of Gearing, at the same groundspeed with the same tire size. So this also does not affect Zip.
Motor efficiency: Does not affect Zip, because Zip doesn't care how much or how fast electrical energy is being used.
Max power: Does not affect Zip, because Zip is a ratio of Lean/accel, and doesn't care about the maximums of either parameter.
Motor’s power rating: Does not affect Zip, because "rated power" is another "maximum" just like above. (It's a steady-state maximum.)
Battery voltage: Does not affect Zip, because Zip is a low-speed concept, and voltage is a limitation only in high-speed operation.

Firmware: Affects Zip! It sets the pedal angle, which is the reference which Lean is measured against.
Weight: Affects Zip! Physical sciences tell us the acceleration term is a force divided by a mass.

Tire size: I think yes; but the reason requires a force diagram to demonstrate why the same lean angle with a smaller tire size results in more acceleration.

 

Edited November 3, 2022 by RagingGrandpa

[mrelwood]

 

3 minutes ago, RagingGrandpa said:

Maybe we can define the Lean angle as an angle at the rider's ankle, i.e.: angle between the pedal and the lower leg.

An actual input torque at the axle would be more precise, since the angle alone doesn’t count for the rider’s height and weight.

3 minutes ago, RagingGrandpa said:

Because this angle is relative to the pedal, not relative to the ground, the impact of firmware / soft mode on Zip becomes clear too.

It might over emphasize the soft mode though, since the actual force we apply on the pedals is dependent on the vertical gravity.

3 minutes ago, RagingGrandpa said:

Zip is a ratio, and is not concerned with the maximum lean angle or maximum acceleration value.

Exactly, yes!!

3 minutes ago, RagingGrandpa said:

Gearing: (if the tire size is not changed) Does not affect Zip, because Zip doesn't care how the acceleration's force was created. A small motor with a gear reduction, or a large gearless motor, can make equal force and achieve equal Zip.
RPM: Is a result of Gearing, at the same groundspeed with the same tire size. So this also does not affect Zip.
Motor efficiency: Does not affect Zip, because Zip doesn't care how much or how fast electrical energy is being used. Zip doesn't care.
Max power: Does not affect Zip, because Zip is a ratio of Lean/accel, and doesn't care about the maximums of either parameter.
Motor’s power rating: Does not affect Zip, because "rated power" is another "maximum" just like above. (It's a steady-state maximum.)
Battery voltage: Does not affect Zip, because Zip is a low-speed concept, and voltage is a limitation only in high-speed operation.

Firmware: Affects Zip! It sets the pedal angle, which is the reference which Lean is measured against.
Weight: Affects Zip! Physical sciences tell us the acceleration term is a force divided by a mass.

YESS!!! Are you using the same brain I am??

3 minutes ago, RagingGrandpa said:

Tire size: I think yes; but the reason requires a force diagram to demonstrate why the same lean angle with a smaller tire size results in more acceleration.

I’m not sure if a force diagram at a frozen time tells the whole story, and I believe that the actual effects of the acceleration are required as well because of the constantly changing self-balancing nature of the system.

 

4 minutes ago, Chriull said:

By now pads to increase lean possibilities are normal - as some years ago https://forum.electricunicycle.org/topic/14032-what-determines-wheel-zippiness/#comment-239217 it was normally limited by the pedal geometry.

Yes. There would be no point in the modern power EUCs without pads.

3 minutes ago, Chriull said:

Afair a real measure/differentiation for zippiness was not found in these times? But the mechanics are well understood.

I’m not sure if I understand you correctly, but [Zip = Acc/Lean] would be a way to precisely calculate the responsiveness of the acceleration. But it would of course be very difficult to measure.

Then again, we already know that the tire diameter is the major factor here, and firmwares and riding modes are difficult to separate anyway. The tire diameter alone gets us in the right ballpark though, and I think it would be worthwhile to talk about it more so that we can decrease the amount of unhappy customers who thought that the Monster Pro would be very zippy because of all the large numbers.

[Planemo]

On 11/3/2022 at 12:48 PM, mrelwood said:

Making calculations about acceleration while disregarding the number one factor that controls it sounds a bit futile.

We only did that because the original query was around whether big wheels will inherently accelerate slower than small wheels.

We have already said several times that EUC power supply is very different to say an ebike.

But the discussion was led by trying to separate the differences to come to a conclusion simply on wheel size vs acceleration for something other than an EUC. I appreciate that the control system on an EUC very much clouds the area but from a physics perspective, bigger wheels (non EUC) either accelerate faster than smaller ones or they don't.

I've still not seen a conclusion that everyone agrees on!

[mrelwood]

I agree, the discussion makes good sense from a non-EUC perspective. But EUCs have been brought up a few times, and the calculations applied to them in a way that doesn’t fit. That’s why I keep bringing up the point I did.

12 hours ago, Planemo said:

I've still not seen a conclusion that everyone agrees on!

I think all but one agrees that bigger tires accelerate slower, and the one is unsure.