Are euc's exceptionally vulnerable or dangerous?

[enaon]

1 hour ago, Robse said:

However:  Our wheels has no real brake.  We cannot brake more than the motor will be able
to provide electrical resistance to, and unfortunately it is also the case that
wheels with powerfull engines are usually much heavier.

it it not a matter of motor alone, if we could utilize all the motor power for braking, the batteries will be destroyed, we need better cells.  

[mrelwood]

What's been mostly missing in this discussion is the method of braking on an EUC. Grip and the EUCs' electrical braking power is meaningless unless you actually apply the brakes. This is done by leaning back. To achieve a braking force in the motorcycle range, the angle between the CoG of the rider and wheel to the contract patch must be around the same that it is on a motorcycle. To achieve that, an EUC rider would have to be in a very deep seated position. Possibly deeper than I've ever seen.

I'll try to find images to showcase this better.

[mrelwood]

Here we go.

Already the motorcyclist's own Center of Mass is at a 46° angle to the front tire's contact patch's vertical. Since the motorcycle most probably weighs more than the rider, the actual CoM is even much lower.

This is just one random example of a deep braking position on an EUC, but already a good bit deeper I have personally ever done. The rider's CoM is only at a mere 29° angle.

 

Conclusion: It would take unseen mad skillz from an EUC rider to get anywhere near a motorcycle's braking potential.

 

Image sources:

https://www.semanticscholar.org/paper/Optimization-of-the-centre-of-mass-position-of-a-in-Cossalter-Lot/fdea0edf92c2aa12490413ac94fd67f6c9eebabf

https://youtu.be/KskwXUkKCsM?t=585

[Planemo]

3 hours ago, mrelwood said:

Conclusion: It would take unseen mad skillz from an EUC rider to get anywhere near a motorcycle's braking potential.

And thats assuming the EUC itself is capable of applying enough braking force to reach the point of lock-up (like an MC) which I doubt an EUC can.

And an MC rider has two almost locked arms on a very solid handlebar to brace their mass against. An EUC rider has the friction of two footplates and....thats about it.

[pico]

1 hour ago, Planemo said:

two footplates and....thats about it.

Is "Asscheek braking" a thing? 

 

 

[Funky]

11 minutes ago, pico said:

Is "Asscheek braking" a thing? 

 

 

In "O-Shit" moment. My ass would be on ground and my feet still on pedals.  So yeah it's a thing.

When hard braking, you are more or less in sit down position, way back - at some point your ass will touch the ground.  

[Tawpie]

Just now, Funky said:

In "O-Shit" moment. My ass would be on ground and my feet still on pedals.  So yeah it's a thing.

When hard braking, you are more or less in sit down position, way back - at some point your ass will touch the ground.  

S*itting position

[Funky]

5 minutes ago, Tawpie said:

S*itting position

[Planemo]

1 hour ago, pico said:

Is "Asscheek braking" a thing? 

Well I guess some well-toned buns would help grip, but the style works against you when you still need to get your mass rearwards of the wheel to get the best braking!

I now envision some crazy rider making up a McGuyver handle that comes rearwards from the front of the EUC, allowing the rider to hold it whilst maintaining a crazy angle rear lean (thinking along the lines of a water skier) 

[Robse]

it's not a problem for me to lean so much backwards (while braking) that the wheel drops me of  - some kind of backwards cutout. Done that twice while practicing hard braking on KingSong 16X , so in terms of braking, my wheel has not the electrical potential to brake as hard as i am able to demand (reverse acceleration) to keep me from falling backwards. I assume the braking power can never be any better than the acceleration the wheel is capable of performing. 

Edited October 6, 2022 by Robse

[Spaghetteh]

I'd be curious to know what effect a wheel's battery charge/voltage has on braking distance. My layman's intuition tells me that as your wheel's battery drains, the risk of overpowering it while braking increases as it does with accelerating. Also, whether it's a result of the rider's precautions or the wheel's available power, I would imagine the braking distance might also increase as voltage depletes.

[Planemo]

9 minutes ago, Spaghetteh said:

My layman's intuition tells me that as your wheel's battery drains, the risk of overpowering it while braking increases

How the braking on an EUC really works has, surprisingly, not been very well documented on this forum to my knowledge. I too am curious at what point regen is used.

Re your quote, you could argue that the more the battery is drained, the more braking you could achieve as you can use more regen. All I know is that at some point there is usually a crossing point between the wheel using battery power to apply braking Vs regen to apply braking. Maybe it even flip-flips between the two.

But in reality, I have no more idea than that!

[atdlzpae]

6 hours ago, pico said:

Is "Asscheek braking" a thing?

Definitely not on my MSX. Off-center trolley handles suck!

A similar device for bikes.

 

I completely agree that EUC's require like 2 times the space a bicycle needs to stop from the same speed. And thus, I consider everyone who rides these things 50mph a suicidal maniac.

And yet, at slow speeds IMO EUC safety is pretty much the same as bikes, except for occasional faceplant for technical reasons.

Behavior is king when it comes to safety.

Edited October 6, 2022 by atdlzpae

[Robse]

26 minutes ago, Planemo said:

How the braking on an EUC really works has, surprisingly, not been very well documented on this forum to my knowledge. I too am curious at what point regen is used.

Re your quote, you could argue that the more the battery is drained, the more braking you could achieve as you can use more regen. All I know is that at some point there is usually a crossing point between the wheel using battery power to apply braking Vs regen to apply braking. Maybe it even flip-flips between the two.

But in reality, I have no more idea than that!

Our wheel motors functions as both a motor and a dynamo.  However, a motor capable of generating 2000W of power, thus consuming this, is not necessarily capable of generating the same amount of output power as electrical energy in case of getting rotated by braking force / downhill travel.  And at some point the demand for braking torque gets bigger than the "dynamo effect" then it will be necessary to consume current (from battery) to create enough torque in opposite rotation direction.  I  assume that the motor can not act as a motor and a dynamo at the same time (? - that would be the prototype of an perpetual motion machine.... )  It should probably be possible to read out the current progression at braking via wheel-log. What i have seen on the 16X is unfortunately only that the negative current (charging) increases until there is a cutout (zero) that is where i have fallen backwards.  So i have not been able to document that the wheel used power to brake.  Maybe it can be seen on RS19?

[enaon]

6 minutes ago, Robse said:

I too am curious at what point regen is used.

All braking action is using regen alone.
The energy has to go to the batteries, but the batteries are like DSL, lots if download/little upload. 

So, we cannot brake a hard as we accelerate, or we end up destroying the batteries, fires etc. 

Edited October 6, 2022 by enaon

[0000]

30 minutes ago, enaon said:

All braking action is using regen alone.
The energy has to go to the batteries, but the batteries are like DSL, lots if download/little upload. 

So, we cannot brake a hard as we accelerate, or we end up destroying the batteries, fires etc. 

Which really highlights how important it is to have batteries that are not just tolerant of higher current peaks while accelerating, but also while decelerating inducing potentially large regen currents under hard braking. As a rule (now), I would think high performance/low resistance cells should always be preferable for not just reasons of performance (limited voltage sag), but also limiting heating most likely improving long term durability (and capacity fade) over higher energy/higher resistance cells.

It makes you wonder, just how much of a factor the repeated braking/regen from normal use going into the original LG M50 cells on the fire-prone Begode 900wh packs was to their tendency to combust. Perhaps these cells were particularly poorly suited for constant and random discharge/charge cycles from relatively normal accel/deccel EUC operations and it wasn't just peak accel currents that did them in over time.

Edited October 6, 2022 by Vanturion

[mrelwood]

28 minutes ago, enaon said:

All braking action is using regen alone.

You seem to be alone with your understanding of the matter. Care to share a bit further why and how others are wrong?

28 minutes ago, enaon said:

The energy has to go to the batteries

Not quite. A large portion of it also goes out as heat. It takes a lot of energy to heat up the motor, a large and heavy chunk of metal.

The MOSFETs also take some power for the switching function and, again, heat losses. So it really can't go all back in, can it?

[enaon]

4 minutes ago, mrelwood said:

You seem to be alone with your understanding of the matter. Care to share a bit further why and how others are wrong?

I thought is was obvious from monitoring voltage and amps on braking action, have you ever noticed something different? 

Ofcource there is loss on heat, but you cannot really expect the heatsink to help as it stands for now, our heatsinks are a joke. 

Edited October 6, 2022 by enaon

[Spaghetteh]

8 minutes ago, mrelwood said:

A large portion of it also goes out as heat. It takes a lot of energy to heat up the motor, a large and heavy chunk of metal.

Can confirm. When I got my first wheel and before I knew any better, I spent a minute or two keeping myself braced against a wall while I did a pendulum motion with the wheel trying to get a feel for braking and accelerating. With all that rapid starting and stopping it didn't take very long for the wheel's temperature to go from ~30C to >60C before it yelled at me for overheating it. So definitely not all of the energy absorbed from braking goes into the batteries - I'd wager the majority of it gets dissipated as heat.

Edited October 6, 2022 by Spaghetteh

[enaon]

17 minutes ago, Spaghetteh said:

I'd wager the majority of it gets dissipated as heat.

the majority goes to the batteries, what you are seeing is the heatsink being bad. 

Edited October 6, 2022 by enaon

[0000]

31 minutes ago, Spaghetteh said:

Can confirm. When I got my first wheel and before I knew any better, I spent a minute or two keeping myself braced against a wall while I did a pendulum motion with the wheel trying to get a feel for braking and accelerating. With all that rapid starting and stopping it didn't take very long for the wheel's internal temperature to go from ~30C to >60C before it yelled at me for overheating it. So definitely not all of the energy absorbed from braking goes into the batteries - I'd wager the majority of it gets dissipated as heat.

Heat losses are going to be described mostly by the total resistance of the motor windings (phase wires), R_motor think total mass of copper windings, and total resistance of the battery assembly, R_batt. I suspect everything else in the circuit is probably negligible or close to including the motor controller/mosfets. Especially given the amount of force being resisted, yeah the controller temp (sensor) might shoot up, but it's a relatively small volume being heated vs the energy involved in stopping. Energy's mostly going to the batteries as @enaonsaid.

Edited October 6, 2022 by Vanturion
added battery resistance

[techyiam]

37 minutes ago, enaon said:

I thought is was obvious from monitoring voltage and amps on braking action, have you ever noticed something different?

Doesn't this depends on how hard a rider brakes?

If a rider doesn't brake hard enough, it should be regen doing the braking.

However, as the rider brakes progressively harder, the reverse current (reverse torque) increases proportionately. But eventually the reverse current from regen will peak. To provide harder braking (higher reverse torque), the controller will have to intervene to increase the reverse current by applying a reverse polarity voltage that is high enough to produce the increase.

[enaon]

58 minutes ago, techyiam said:

Doesn't this depends on how hard a rider brakes?

If a rider doesn't brake hard enough, it should be regen doing the braking.

However, as the rider brakes progressively harder, the reverse current (reverse torque) increases proportionately. But eventually the reverse current from regen will peak. To provide harder braking (higher reverse torque), the controller will have to intervene to increase the reverse current by applying a reverse polarity voltage that is high enough to produce the increase.

I think you need todo some testing, it will be easier than words, there is the language barrier too.  

use eucworld* or any app you like, and monitor voltage and amps. If you ever see voltage going down on braking, then ok, you are extracting battery energy, but you will not. 

this is the only one I can find that short of demonstrates it, I will make one when I get the chance. On left top window I have the amps, when they start from top they are regen-batery input, from bottom they are output. Have a look if you like. 
 

*euc world's live dash is not a great tool for monitoring the wheel real time, it uses buffering to smooth out values on voltage, it really does not help the rider understand the wheel the way I see it. It's graphing system is very nice though, so use that. 

Edited October 6, 2022 by enaon

[blox1130]

Wrong way has demonstrated, and I can certainly feel the same, that braking distance is equivalent. The motor can slow you down just as fast as it can move you forwards, arguably even easier since the motor isn't doing work but having work done on it. I also have experience using only regen braking on my two and three wheeled vehicles and its fundamentally the same.

Watch the video at 6:20

 

Edited October 7, 2022 by blox1130

[blox1130]

Another thing people seem to not notice: we always have ABS enabled. Even better ABS than any other number of wheels. This is counteracted somewhat by the wobbling you get when stopping hard.

Secondly, while we have one tire instead of two, the pressure under that one contact area is nearly twice that under the wheel of a two wheeler.

Cutouts are bad, but other vehicles experience catastrophic and unrecoverable failure: airplanes can lose a wing or control surface, helicopters lose their rotor blades, parachutes can get tangled up, 4, 3, and 2 wheelers can lose their mechanical brakes or the throttle can get stuck on. Motorcycles slide out quite often because the power applied to the wheel can be too much for the traction of the wheel. 4 wheeled vehicles slide when entering turns too fast or the steering input is too strong, or they flip over completely.

Edited October 7, 2022 by blox1130