Veteran Cutout Question

[Benjaminjhobbs]

I know, I know. We have all heard it asked a million times. Why does a wheel cut off, can it be prevented, what are some safety precautions I should take, etc. But this question is just one of slight clarification. I might be a new rider and the Sherman might be my first wheel but I have read every forum on this site about cutoff and watch about half a dozen YouTube videos on it and I still am a little confused. 

This post which has lots of great info about this topic. One thing indicated by @Andy Huang was a chart indicating the visual discrepancy between how many bars are shown on the Sherman LCD and the actual percentage left. Because of this, it seems much wiser to go off of the voltage rather than the battery percentage on DarknessBot or even bars left on the Sherman. That being said, it makes sense that ALL cutoffs would occur when the wheel doesn’t have enough umph (power, volts, amps, what have you) to keep itself balanced, I.e. it is unable to keep up enough momentum to stay with your shifted center of gravity. This makes perfect sense and thus it is impossible to completely prevent a cutout in every situation. I have also understood that because of this, on the Sherman around 75 volts the wheel will cutout. This too makes sense, but question, does that mean EVERY time the wheel hits this voltage it will cut out and that EVERY cutout occurs under that voltage? 

Of course, keeping an eye on darknessbot while I ride, the voltage fluctuates and, of course, when you demand more of the wheel in acceleration you see it drop down which is why people, in a hard enough lean, can get a wheel to cutout even if it is fully charged. If they can demand so much of the wheel to get the volts to drop below 75volts (roughly) it will cutout. That said, today I went on a short ride with what darkness bot said was 40% battery. Now I know the percentage on Darkness from what I have heard is off so I have been going off of the voltage. Sitting still, I was at 85volts. I thought, fine, good, I have another 10 volts before cutout. I showed three bars on the Sherman which also aligns (mostly) with the chart that Andy Huang had posted. I went for a ride staring at my phone and did some pretty mild accelerations (granted I am a new rider and only have 60 miles under my belt, it wasn’t a hard acceleration by any stretch). The volts dropped all the way to 76 for a split second and back up again. Does that literally mean I was just a volt away from cutout? 

With DarknessBot, as we all know, I can set custom alarms for speed, amperage, power, or temperature. If this is the case with cutout’s and volts, why not have one for volts!? If every single cutout on the Sherman occurs when it drops below 75volts (or there about) why not just set an alarm for 80. If this is truly the case with cutouts, I would want everything to scream at me whenever I even get within 5 volts. 

Thank you all for putting up with yet ANOTHER question about cutout but I think it is always in the back of our minds as an EUC rider. It’s stinking creepy. 

[Benjaminjhobbs]

Okay another though after watching this. Does the Sherman have a progressive tilt back attempting to prevent cutout or just a beep? 

[Chriull]

3 hours ago, Benjaminjhobbs said:

That being said, it makes sense that ALL cutoffs would occur when the wheel doesn’t have enough umph (power, volts, amps, what have you) to keep itself balanced, I.e. it is unable to keep up enough momentum to stay with your shifted center of gravity. This makes perfect sense and thus it is impossible to completely prevent a cutout in every situation. I have also understood that because of this, on the Sherman around 75 volts the wheel will cutout. This too makes sense, but question, does that mean EVERY time the wheel hits this voltage it will cut out and that EVERY cutout occurs under that voltage? 

These are no cutouts - nothing is cutting anything off - it's just a "normal" overlean!

The bldc motors have a maxum torque over speed limit. This is a straight line bezween stall torque (absolute max torque) at zero speed to zero torque at no load speed (about lift cut off speed).

If one needs at some speed more torque as this maximum torque by some burden (acceleration, incline, etc) one falls forward. The higher the difference between needed torque and maximum torque the faster one falls forward.

Already without pads by just strongly leaning forward an overlean felt like the wheel cuts out...

For more details see 

 

[Daley1]

Tips to prevent an overlean-ride it fully charged, dont accelerate hard ,dont accelerate hard when battery at 50% (my safety margin)or lower.Just cos a wheel can go 50mph doesnt mean u have to ride it at 50 mph.U can ride a wheel down to o% battery but u have to adjust ur riding very carefully and get ready to step off !

[Ben Hatfield]

I've read this distinction a bunch lately: Cut out vs over lean.  If both cases are overpowering the wheel, why is the distinction so specific? 

I think a lot of people think of the term 'cut out' as simply loss of enough power to cover a given EUC circumstance.  So over leaning, causing a power spike, cutting out the wheel - sounds logical.

Why does the term 'cut out' only apply to overpowering a wheel via speed?  Or what situations (plural) does 'cut out' apply to?

Just curious

[Chriull]

24 minutes ago, Ben Hatfield said:

I think a lot of people think of the term 'cut out' as simply loss of enough power to cover a given EUC circumstance.

Exactly. Needed torque to keep the rider upright is higher than the torque the motor can deliver.

26 minutes ago, Ben Hatfield said:

So over leaning, causing a power spike, cutting out the wheel - sounds logical.

Cutting out is wrong term imo - nothing turns off! The wheel still delivers as much as possible - but that's just not enough.

[null]

54 minutes ago, Ben Hatfield said:

Cut out vs over lean

Wouldn't a cut-out be an accidental failure (electronics etc) where as an over-lean would be demanding more power than the EUC can provide?