MCM5 sudden acceleration/cut out at 23 or 24 mph

[nickysneids]

Hi all!

I've been getting cozy with my MCM5 over the past 6 months and have about 700 miles on it so I'll share my thoughts on this.

First of all, thank you for the full speed no load tilt test! Great to finally see someone push the wheel all the way.

Second of all, I weigh around 180lbs and ride my wheel to max ~26mph  before I hear my third alarm, so this seems to coincide with the majority of information on this thread.

1 hour ago, maltocs said:

However if tiltback wasn't turned on, I would probably accelerate as I intended?

With no tilt back on you should be able to slowly accelerate until the wheel can't keep up, which is where your weight, terrain, and battery come into play. I know a lot of people are convinced that his had nothing to do with tilt back but as someone who weighs 200+ and has little experience on the MCM5 at high speeds, it's conceivable that you could have over leaned through your tilt back AND suffered from the tilt back speed acceleration causing you to jump into a cut out. Depending on how far you were leaning forward, you could have push the wheel to it's limit before the acceleration tilt back method (ie. the carpet slipping out from under you) had time to do its magic.

I personally think you'd be fine to ride up to your third beep with tilt back turned off. If you ease up at the beginning of your third beep (1-3 beeps), and you don't hit any considerable bumps at this speed, you can still enjoy the potential of the wheel without worrying about a cut out.

Super happy your okay and and even happier how much I was able to learn about the nature of Gotway tilt back and the MCM5 from this thread. Thanks for the testing and shout out to everyone who has taken the time to weigh in.

[Chriull]

2 hours ago, maltocs said:

I'm accelerating and leaning forward when tiltback begins, i don't notice the tiltback and just push forward. (is this called riding the tiltback?) And in this case, the wheel WOULD accelerate even more than I intended (surprise!) because I'm still pushing forward. However if tiltback wasn't turned on, I would probably accelerate as I intended?

Another try, from a different point of view:

The wheel is self balancing - meaning it adopts acceleration/deceleration according to the pressure one puts on which part of the pedals/cog relative to the wheels position/rider lean so it keeps one stable (not falling) in this self choosen position.

If one does not change the position (forward lean, pressure ob pedal front) and the wheel increases acceleration (on the rider) one would fall backwards!

(Compare this to @Mono's carpet example)

As you describe that "the wheel increased acceleration on you" and you did not "lean/fall/turn" backwards the only explanation is that you increased your forward lean!

As you wrote that this was not your intention, this had to be an unintentional reaction by beeing "surprised/puzzled" by the tiltback setting in.

So you, by your not intended reaction indeed "rode the tiltback" forcing the wheel to accelerate even more to keep you balanced.

If one reacts in the "normal" way on a tiltback the wheel just zips a bit forward relative to ones position and this reduces the forward lean/shifts the cog relative to the wheel backwards/reduces the pressure on the front of the pedals and by this the wheel reduces acceleration to keep you balanced again in this new position.

So the tiltback "forced" you to unintently "ride the tiltback" which forced the wheel to increase acceleration.

Edited October 9, 2019 by Chriull

[maltocs]

15 minutes ago, Chriull said:

Another try, from a different point of view:

The wheel is self balancing - meaning it adopts acceleration/deceleration according to the pressure one puts on which part of the pedals/cog relative to the wheels position/rider lean so it keeps one stable (not falling) in this self choosen position.

If one does not change the position (forward lean, pressure ob pedal front) and the wheel increases acceleration (on the rider) one would fall backwards!

(Compare this to @Mono's carpet example)

As you describe that "the wheel increased acceleration on you" and you did not "lean/fall/turn" backwards the only explanation is that you increased your forward lean!

As you wrote that this was not your intention, this had to be an unintentional reaction by beeing "surprised/puzzled" by the tiltback setting in.

So you, by your not intended reaction indeed "rode the tiltback" forcing the wheel to accelerate even more to keep you balanced.

If one reacts in the "normal" way on a tiltback the wheel just zips a bit forward relative to ones position and this reduces the forward lean/shifts the cog relative to the wheel backwards/reduces the pressure on the front of the pedals and by this the wheel reduces acceleration to keep you balanced again in this new position.

So the tiltback "forced" you to unintently "ride the tiltback" which forced the wheel to increase acceleration.

Thanks for your differing explanation. I'm definitely getting the gist of what happened. To me, it's like the Hangover movie. I'm slowly piecing what happened after the fact to figure it out. Although I'm learning a lot, my most important lesson is that I never want to push any wheel to it's limits, no where close. I just want to ride EASY without thinking about what might happen if I push the limits. Solution, don't push it!  

I don't care how lift works, I just want the plane to fly is how I used to think. I really enjoy riding wheels, but up to this point, I seen crash videos and critiques on why they happened but with my modest riding style, I never thought it would happen to me. But since i AM piloting my own wheel, I do need to understand the mechanics of the wheel even though I never plan to push any wheel near it's limits ever again. Thanks @Chriull and @Mono for spending so much time with this analysis. 

Okay, now I'm curious, can someone please explain to me how LIFT works? 

 

55 minutes ago, nickysneids said:

Super happy your okay and and even happier how much I was able to learn about the nature of Gotway tilt back and the MCM5 from this thread. Thanks for the testing and shout out to everyone who has taken the time to weigh in.

I'm glad that my If my fall and this thread somehow helped someone else understand what happens at the "pushing the limits" spectrum of this wheel

 

 

 

[mrelwood]

2 hours ago, maltocs said:

Okay, got it. Can't argue with you there. Lets talk terminology, what would it be called when one does the following:

I'm accelerating and leaning forward when tiltback begins, i don't notice the tiltback and just push forward. (is this called riding the tiltback?) And in this case, the wheel WOULD accelerate even more than I intended (surprise!) because I'm still pushing forward. However if tiltback wasn't turned on, I would probably accelerate as I intended?

Riding the tilt-back is intentional, since it requires a good amount of focus to keep the rider’s balance at the edge of a tilt-back.

Not noticing the tilt-back, I would call a non-tiltback. Just like the carpet analogy demonstrates, when we stand with parallel feet, our balance is extremely volatile. Think about how slowly the carpet would have to be drawn out from under our feet in order for us to be able to keep our balance. Let’s call that speed a window of balance.

If the tilt-back acceleration is any faster than the window of balance allows, the wheel is able to succesfully accelerate from under us, and make the tilt-back happen as intended, causing us to lean backward and brake.

For the tilt-back to be able to accelerate both the rider and the wheel, the tilt-back would have to be slower than the window of balance.

The tilt-back on the MSX actually is quite slow, but it is still easily faster than my window of balance allows, so it is fast enough to function as intended.

The only situation I can think of where the tilt-back could do what you suspect it did, is if you were already at the verge of an overlean. When trying to accelerate, the capabilities of the wheel were exceeded and the tilt-back was only able to function with a fraction of the power that it intended. But in that case the tilt-back acceleration would be so slow, that it wouldn’t have much effect in your actual speed.

Again, the window of balance. How slow would the carpet have to be dragged from under you for you not to notice that the carpet is moving? That is the amount of additional acceleration that could’ve taken place, not more.

 

You mentioned being familiar with the tilt-back especially on your other self-balancing vehicles. My guess is that no tilt-back has gone unnoticed, and no tilt-back has failed to actually tilt the pedals back before. As you said, you haven’t even felt the Ninebot accelerating, just tilting. That’s how easy it is for these vehicles to overcome our window of balance.

If I were you, I might set the MCM5 tilt-back somewhere around 10mph, and experiment. There are good power reserves at those speeds, so you could safely test wether you can get the wheel to speed yourself up.

 

I didn’t mention it before, but I am also glad that you didn’t suffer any more damage to yourself! Amazing luck!

[Mono]

1 hour ago, mrelwood said:

Again, the window of balance. How slow would the carpet have to be dragged from under you for you not to notice that the carpet is moving? That is the amount of additional acceleration that could’ve taken place, not more.

Good point!

1 hour ago, mrelwood said:

If I were you, I might set the MCM5 tilt-back somewhere around 10mph, and experiment. There are good power reserves at those speeds, so you could safely test wether you can get the wheel to speed yourself up.

+1

[maltocs]

1 hour ago, mrelwood said:

Riding the tilt-back is intentional, since it requires a good amount of focus to keep the rider’s balance at the edge of a tilt-back.

Not noticing the tilt-back, I would call a non-tiltback. Just like the carpet analogy demonstrates, when we stand with parallel feet, our balance is extremely volatile. Think about how slowly the carpet would have to be drawn out from under our feet in order for us to be able to keep our balance. Let’s call that speed a window of balance.

If the tilt-back acceleration is any faster than the window of balance allows, the wheel is able to succesfully accelerate from under us, and make the tilt-back happen as intended, causing us to lean backward and brake.

For the tilt-back to be able to accelerate both the rider and the wheel, the tilt-back would have to be slower than the window of balance.

The tilt-back on the MSX actually is quite slow, but it is still easily faster than my window of balance allows, so it is fast enough to function as intended.

The only situation I can think of where the tilt-back could do what you suspect it did, is if you were already at the verge of an overlean. When trying to accelerate, the capabilities of the wheel were exceeded and the tilt-back was only able to function with a fraction of the power that it intended. But in that case the tilt-back acceleration would be so slow, that it wouldn’t have much effect in your actual speed.

Again, the window of balance. How slow would the carpet have to be dragged from under you for you not to notice that the carpet is moving? That is the amount of additional acceleration that could’ve taken place, not more.

 

7 minutes ago, Mono said:

Good point!

While thinking of the physics and the capability of these wheels please keep in mind that I am 195lbs, and on that day, I was 210lb with the cargo I was carrying. I think the carpet example is a great example, but we also have to keep in mind my carpet was accelerating rapidly from zero to over 20 so a high speed tiltback would be less noticeable than a stationary carpet starting to move. Especially with this magic window. 

So if my 210lb self leaning forward to accelerate was countered by a fairly WEAK tiltback due to the power available to accelerate this wheel even more beginning at 23mph, and I am in this window, I think the chances of me NOT noticing the tiltback are much higher. 

1 hour ago, mrelwood said:

If I were you, I might set the MCM5 tilt-back somewhere around 10mph, and experiment. There are good power reserves at those speeds, so you could safely test wether you can get the wheel to speed yourself up.

I will definitely try this out to see how much of a difference this wheel's tiltback is. I'll try it at 10mph, but please don't ask me test it at 23mph!

[Mono]

1 hour ago, maltocs said:

but we also have to keep in mind my carpet was accelerating rapidly from zero to over 20 so a high speed tiltback would be less noticeable than a stationary carpet starting to move.

Consider the carpet is laying in an accelerating train (with constant acceleration). It doesn't make a difference (other than that you will feel a little heavier and stand not exactly upright to begin with, like on a slight incline). You will be affected by small changes in acceleration (carpet pulls) as easily as at standstill. The magic window should even be slightly smaller, because the CoG is not right above the feet under acceleration, hence the effective length of the feet is a few percent smaller due to the projection (like when standing on a slight incline).

Edited October 9, 2019 by Mono

[alcatraz]

I'd just send an email/pm to gotwayand ask what settings/firmware you need to make the wheel a bit safer.

It wouldn't feel good to know that if you make a mistake the safety features don't help.

This way you don't have to test the tiltback at max speed.

[maltocs]

On 10/9/2019 at 12:27 PM, mrelwood said:

If I were you, I might set the MCM5 tilt-back somewhere around 10mph, and experiment. There are good power reserves at those speeds, so you could safely test wether you can get the wheel to speed yourself up.

 

On 10/9/2019 at 1:47 PM, Mono said:

+1

I finally took the MCM5 out again and tested tiltback behavior. I have to admit, i was a bit more cautious than I've been. I didn't feel ONE with the wheel so to speak, maybe two or three  . I put the tilt back at 15km I did notice tiltback is very subtle on this wheel. It is definitely more noticeable when creeping up slowly to the tiltback speed vs accelerating hard to it. When I try to "ride" the tiltback once it begins, it's actually  pretty hard to do after a few seconds. I keep the gotway app open, watch it hit 15km and feel the pedals begin to tilt back. I continue to press forward until I get to 21km. I could be imagining it, but it feels like the harder I push forward past 15km, the more the pedals are tilting back. It is harder to get past 21km for me without feeling off balance.

When I do a hard acceleration, I hardly feel the pedals tilting back because it happens so slowly. Initially it just feels like it is losing power so I push harder to get that power back. That's when I notice the pedals actually tilting. 

I'll be honest, I can't actually feel the wheel accelerate to get in front of me. I just feel the pedal tilt. But then again i'm not accelerating that hard and it is set at only 15km.

I did the same test at 21km and tiltback seems even more subtle. 

This probably why during the crash, I didn't feel the tiltback as  it was set at max 36km. Remember, I didn't even know it was on.

Then I turned it off completely and I was able to ride like I normally do, free as a bird without the feeling of the wheel nagging me to slow down. (keep in mind I'm still going under 30km in all these tests today.)

I'm not drawing any conclusions or making any opinions, i'm just stating the facts to what I felt during my test.