Max speed setting for V8F with 190 lb rider

[rcgldr]

I currently have the V8F max speed set to 25 kph (15 mph). At 190 lbs, I'm thinking max speed of 35 kph could risk cutout, so considering 30 kph, but if that is also risky, I'll just leave it at 25 kph. 

[level9]

About 230 lbs here with gear. Have the speed limit set @ 20 mph. Due to the progressive tilt back I usually only hit around 19 mph with that setting. Never any cutout issues and I ride it pretty hard. Overpowering the wheel in acceleration or braking gives a quick little pedal dip as a warning and is easily recoverable so long as you are paying attention.

[Chriull]

19 hours ago, rcgldr said:

I currently have the V8F max speed set to 25 kph (15 mph). At 190 lbs, I'm thinking max speed of 35 kph could risk cutout, so considering 30 kph, but if that is also risky, I'll just leave it at 25 kph. 

Speed is only one factor determining cutout risk - the second is the burden (acceleration, incline, etc...)

 

 

 

[Rodo]

Mine is set to the 20 miles/hour (or the max., can't really remember...lol) I haven't had a cut out yet. At that speed I can't really hear the beep beep you're going too fast because of wind noise but I can feel the tilt back. No big deal ... I slow down a bit. All good. Oh I'm 150 lb.

Edited September 13, 2021 by Rodo

[rcgldr]

6 hours ago, Chriull said:

Speed is only one factor determining cutout risk - the second is the burden (acceleration, incline, etc...)

I was aware of that, I meant on level pavement. I did a little over 2 mile ride on a paved bike path with some mild slopes, averaging about 8 mph, peak speed 12.4 mph, and peak power was 624 watts. The V8F has a 1000 watt motor, and if that is the limit, there wouldn't be much more margin for speed on that bike path. I tested again on a 100 foot long 6 degree slope at around 7 mph, and peak power was 710 watts. The V8F specs mention a 2000 watt peak, but I don't know if that means a few seconds (like braking) or a fraction of a second (like a bump). I can test on a 2000+ foot long and wide straight pathway that is nearly level, (between 1 and 2 degrees), and look at peak positive and negative power versus speed. I've tested tilt back on the slight incline there at 8, 12, and 15 mph without issue, I'll test again to see what the peak power is.

Edited September 14, 2021 by rcgldr

[rcgldr]

I went out again to the venue with the 2000+ foot long and wide pathway (Great Park in Irvine CA) which is slightly sloped. I was wearing helmet, wrist guards, and a light jacket for a total of 198 lbs. With max speed set to 25 kph (15.5343 mph). I slowly increased speed until I got alarm beeps and tilt back, with a resulting max speed showing about 16 mph. In the incline direction, max power was +965, -324. I turned the V8F off and on to test again in the decline direction, max power was +604, -909. I have tire pressure set to about 35 psi (inflated to 36 psi a few days ago), but if tire pressure was low, it should have helped with the decline. The +965 and -909 are close to the V8F's rated power of 1000 watts, so I'm not sure about increasing the speed more.

Although I slowly accelerated until I got tilt back, during tilt back, the V8F accelerates forwards to get the contact patch ahead of the center of mass, and also tilt back, which moves the pedals forwards to lean the rider backwards. This somewhat of a burst of acceleration would explain the +965 watt peak on the incline. The decline peak of -909 is related to the braking force times speed. After the initial tilt back on the decline, I tried to decelerate to a stop gradually to take a look at the power peaks, but my input may have contributed to the decline peak.

The V8F specs state a peak power of 2000 watts, but it's not clear to me if it can sustain 2000 watts for the total time it takes to do a tilt back.

Edited September 14, 2021 by rcgldr

[Chriull]

4 hours ago, rcgldr said:

The V8F has a 1000 watt motor, and if that is the limit,

No. Power limit for some specific over speed is no constant value

Edit: For a specific speed (at a certain battery voltage) power limit is constant, beside temperature, etc influences as @Eucnermentioned.

Taking the reported power values as a limit for overlean is very counterproductive. Don't know if the V8 has already the firmware reported PWM %, or this is only reported for V10 and newer?

 

Edited September 14, 2021 by Chriull

[Eucner]

The electric motor power is temperature limited. It varies with usage, ambient conditions and time. Manufacturers don't give information how constant and peak power ratings are obtained. There is a lot of marketing involved.

[mrelwood]

While familiarizing yourself with the reported peak power values is definitely useful, the numbers can’t be approached very scientifically.

The 1000W nominal, 2000W peak values are not for the actual motor alone. Usually the battery is the limiting factor in EUCs, and it is unknown how the peak power capabilities of the battery are taken in account in the above values. We only know that they are.

 My take on your values (~900W peak) is that there’s a large amount of safety margin left. Even the 2000W isn’t a hard limit, and EUCs can generally provide much more for a short peak (< 1s).

 When you reach the actual limit of the wheel’s power, that’s when the pedals will start to ”go soft”. If you momentarily ask for 100W more than the wheel can provide (at the current battery level, speed, temperature, etc), you will feel that the wheel was no longer capable of keeping the pedals fully horizontal. But it was still able to provide ~95% of the required power, so it’s not like you’re going to explode right away.

Once your power requirement goes back below the wheel’s capabilities, the wheel will behave normal again. Only if you set yourself so that your excessive power requirement lasts longer than it takes for the wheel to dip 40-45 degrees forward, then you’re in trouble.

 But this is of course a very slippery slope, as it’s extremely hard to anticipate the peak power capabilities at any given situation, as they vary a lot.

Quote

the V8F accelerates forwards to get the contact patch ahead of the center of mass, and also tilt back, which moves the pedals forwards to lean the rider backwards.

This is probably what you meant, but just on case others read the quote wrong the same way I first did:

An EUC can do one thing, and one thing only: Spin the tire, forward and back. That’s all. It can’t directly move or tilt the pedals, and it can’t even accelerate the rider unwillingly like all non-self-balancing vehicles can. All it does is accelerate or decelerate based on how the interprets the wheel’s tilt angle. It just does it so many hundred times every second that the wheel can feel horizontally as solid as a bicycle.

 You have correctly figured out that the tilt-back uses additional power, since the wheel has to accelerate. Do remember though, that for the rider to be able to brake, he’d first have to accelerate just the same to get the wheel in front of him. If the tilt-back is as slow on the V8F as it is on the V11, it even uses a good bit less power than I usually do when I start to brake.

[rcgldr]

6 hours ago, mrelwood said:

power requirement lasts longer than it takes for the wheel to dip 40-45 degrees forward, then you’re in trouble.

An EUC can do one thing, and one thing only: Spin the tire, forward and back. That’s all. It can’t directly move or tilt the pedals, and it can’t even accelerate the rider unwillingly like all non-self-balancing vehicles can. All it does is accelerate or decelerate based on how the interprets the wheel’s tilt angle. It just does it so many hundred times every second that the wheel can feel horizontally as solid as a bicycle.

What is wheel "dip", and being somewhat new (78 miles on the V8F), how would I notice it? I accelerate and decelerate conservatively, but would need to brake harder if there was an emergency. I'm not sure of a safe way to determine how much braking input I can safely use, since this would be speed dependent (an over-voltage or motor limitation issue). I could sit back instead of leaning back while standing up for more margin for error.

EUC acceleration or deceleration coexists with a tilt torque, a forwards torque on the tire coexists with a backwards torque on the frame, and vice versa. For balance, the rider has to be leaned forwards ahead of contact patch or backwards behind contact path to counter the torque on the frame.  For tilt back, the EUC is smart enough to accelerate at a rate that moves the contact patch ahead of the rider while at the same time tilting back (which moves the pedals forwards) in a controlled manner.

Inmotion V8F maintains speed as well as balance on transitions to inclines or declines. On a transition to incline, the EUC leans the rider forwards enough to counter the backwards torque on the frame that coexists with the forwards torque on the tire, with no rider input. On a transition to decline, the EUC leans the rider backwards enough to counter the forwards torque on the frame that coexists with the backwards torque on the tire, with no rider input. Since the V8F handles these transitions with no perceptible rider input, I slow down before a transition to an incline or decline to a speed I think the V8F can handle. It seems that Inmotion and other EUCs do this "auto-correction" for incline | decline transitions. Someone posted that their Sherman doesn't do this, and requires a lot of rider input to maintain speed on such transitions.

Edited September 14, 2021 by rcgldr

[mrelwood]

56 minutes ago, rcgldr said:

What is wheel "dip", and being somewhat new (78 miles on the V8F), how would I notice it?

Pedal dip refers to the wheel deviating  from staying horizontal. The V8F behavior when transitioning to a steeper incline/decline is something you already noticed, and if the pedals would dip because of insufficient power, you would definitely feel the wheel struggling to keep the balance. A pedal dip like that is short in duration, as the wheel tries to retain balance again as soon as possible.

Here’s a video of the KS 16X being “flicked” close to its max speed. The wheel doesn’t have enough power available to respond to the aggressive power requirement at high speeds:

 

56 minutes ago, rcgldr said:

I accelerate and decelerate conservatively, but would need to brake harder if there was an emergency.

Practicing emergency braking is definitely worth it! Simply braking harder in an emergency situation doesn’t necessarily work very well if the braking strength is a completely new one for the rider. Balance issues and especially wobbles are something you might have to practice how to get in control. I know I sure did.

When practicing emergency braking, I say to myself that if I’m supposed to retain control when braking hard in an emergency situation, I damn sure better be able to do the same without the stress and the newness of an actual emergency. Same goes to “stressing” the wheel: If I overdo it while practicing, I’ll then know the very important limits.

56 minutes ago, rcgldr said:

I'm not sure of a safe way to determine how much braking input I can safely use, since this would be speed dependent (an over-voltage or motor limitation issue).

Watching the amount of power being used, or especially the PWM utilization that is available in EUC World (Android) or DarknessBot (iOS), gives you good feedback on how much more power you can use for the braking. Check the app after a practice run, and if there is a lot of power margin left, just brake a bit harder on the next one.

[rcgldr]

1 hour ago, mrelwood said:

Watching the amount of power being used, or especially the PWM utilization that is available in EUC World (Android) or DarknessBot (iOS)

It seems the V8F doesn't report PWM, as I don't see it listed when using EUC World, just max power (along with the other reported values).

[rcgldr]

Did a bit over 3 miles today on the bike trail with some slopes. Max power was 1100 watts, and I don't recall a beep or tilt back, but it was windy enough that I may have missed the beep. Didn't seem to be an issue. Somehow volume was set to 80%, so I set it back to 100%.

Edited September 16, 2021 by rcgldr

[mrelwood]

I don’t think the volume adjustment applies to crucial warning beeps. At least in the V11 they always play at the full volume.

When I ride my V11 (2200W nominal), the max power is around 3000 - 3500W. I’ve never gotten a warning beep or a tilt-back during acceleration or even on the steepest of inclines.

I have overpowered it a few times though when I failed to clear an obstacle and I had all my weight on the wheel that was stationary behind a large rock or a root. That’s when the wheel tilted forwards until it turned off the motor as the wheel reached a tilt of about 45 degrees forward. Too bad I didn’t check the max power then!

 Anyway, you are well within the safe operating parameters of your wheel.