Value of EUC Suspension?

[Eucner]

8 hours ago, Chriull said:

So the perpendicular part of the force truly stays the same, but with increasing speed the horicontal part grows.

The resulting impact vector get bigger by this, but the impact angle more shallow.

The horizontal part of the impact force vector is friction force. It is only function of friction coefficient and vertical force. Surprisingly speed doesn't have any effect into it. 

[Chriull]

11 hours ago, Eucner said:

The horizontal part of the impact force vector is friction force. It is only function of friction coefficient and vertical force. Surprisingly speed doesn't have any effect into it. 

The effect of higher speed is the timespan the friction force is applied until one stops.

The speed (kinetic energy) of the body also impact the torque acting on body parts stopped a bit by friction force but still fixed to other not braked parts?

So this consideration reminds me again, why

21 hours ago, The Brahan Seer said:

Sorry to hear about your crash but the force you felt hitting the ground will not increase the faster you go, the force you felt would be from gravity.  

is (in most cases) wrong!

Normally one touches the ground with some parts of the leg first. Friction decelerates this part and by this a torque acts on the "undecelerated" upper torso -> the impact force of the face against the ground is higher than with just falling forward.

[The Brahan Seer]

If you literally fell 90 degrees flat on your face it would be the same force but in reality no one falls like this as you have stated, we have reflex actions (putting hands out/arms) to help minimise the impact.  On a side note I found this interesting on helmets: 

The typical road or trail bike crash involves a drop to pavement. The important energy in that crash is supplied by gravity, not by forward speed. Although forward speed can contribute some additional energy, the main force is the attraction of gravity, and the impact severity is determined by the height of your head above the pavement when the fall begins. It is gravity that determines how fast your helmet closes with the pavement. Some of the crash energy is often "scrubbed off" by hitting first with other body parts. The typical bicycle crash impact occurs at a force level equating to about 1 meter (3 feet) of drop, or a falling speed of 10 MPH. The rider's forward speed before the crash may be considerably higher than that, but the speed of the head closing with the ground, plus a component of the forward speed, less any energy "scrubbed off" in other ways, normally average out at about 10 MPH.

So bike helmets are tested with a 2 meter (6.56 feet) drop. Motorcycle helmets are tested at 3 meters, about 17 mph. A really good bicycle helmet can handle that.

Link: https://www.helmets.org/limits.htm

So I imagine it would be worse for an EUC crash.

 

 

 

[Eucner]

1 hour ago, Chriull said:

The speed (kinetic energy) of the body also impact the torque acting on body parts stopped a bit by friction force but still fixed to other not braked parts?

Normally one touches the ground with some parts of the leg first. Friction decelerates this part and by this a torque acts on the "undecelerated" upper torso -> the impact force of the face against the ground is higher than with just falling forward.

This off-topic, but some might find it interesting. Falling forward has greater inertia than falling down, so it takes a longer time. Released potential energy is same in both cases. Friction moment overcomes this inertia, but doesn't change potential energy. To change a horizontal force into a vertical force one would need a fixed point, which a falling person doesn't have. Falling down from zero speed is about same thing as driving 14-17 km/h (9-11 mph) into a wall. It is a good reason to always gear up. Falling down from speed adds impact forces only 17% when the friction coefficient of belly landing is 0.6. Combined vector force is in 31 degrees angle from the normal to the road (still quite vertical). The most dangerous aspect of speed is hitting objects before or during sliding.

Edited August 7, 2021 by Eucner

[Chriull]

6 minutes ago, Eucner said:

To change a horizontal force into a vertical force one would need a fixed point, which a falling person doesn't have.

Yes, a free falling person does not have such a fixed point. An EUC driver "doing" a face plant has as mentioned above "about almost a fixed point" - the feet/knees touching the ground first and by this turning some of the horizontal speed vector of the head to a vertical one.

[Eucner]

34 minutes ago, Chriull said:

Yes, a free falling person does not have such a fixed point. An EUC driver "doing" a face plant has as mentioned above "about almost a fixed point" - the feet/knees touching the ground first and by this turning some of the horizontal speed vector of the head to a vertical one.

No, there is neither an almost fixed point. The friction moment will create rotational speed around the center of mass, which just somewhat compensates the additional inertia. It won't change the vertical energy of the center of mass. If you don't believe me, look for crash videos. Hitting knees into the ground don't put people into a wild forward spinning motion. They sometimes just lose their balance and sometimes not.

[Paul A]

Not sure if moto gp is comparable to EUCs, but here is a video of a rider tumbling forward, even when on the gravel trap.

 

[Chriull]

1 hour ago, Eucner said:

No, there is neither an almost fixed point. The friction moment will create rotational speed around the center of mass, which just somewhat compensates the additional inertia.

On one end (knee) acts the friction force. On the other end (upper torso) the "mass inertia" moving forward.

This a perfectly classic example of a torque spinning the rider "for/downwards".

Of course this momentum depends on the friction force - sliding with some hard plastic knee protector on asphalt gives about no friction and forward torque. This can be easily avoided by leaning a bit backwards - as you named it balancing.

Digging with the knees into gravel, having soft rubber on asphalt, etc gives high friction forces creating high torques like in @Paul A's example. With no chance of counterbalancing these forces.

Although this tumbling most likely was initiated by some small "level differences/bumps", as in reality flat ground is not something one can count on...

[Eucner]

1 hour ago, Paul A said:

Not sure if moto gp is comparable to EUCs, but here is a video of a rider tumbling forward, even when on the gravel trap.

The driver hit ground sideways. It is very difficult to keep balance in that position.

[Chriull]

11 minutes ago, Eucner said:

The driver hit ground sideways. It is very difficult to keep balance in that position.

The need to balance to stay upgright or starting to tumble/spin if one cannot balance is a very strong sign of a torque acting on ones body...

[Eucner]

26 minutes ago, Chriull said:

This a perfectly classic example of a torque spinning the rider "for/downwards".

Rider is measured by his center of gravity. Spinning itself doesn't change downward speed, because it is introduced by a horizontal force. If upper body is moving downwards, will lower body move upwards. Only body parts taking vertical impact will slow down vertical speed.

29 minutes ago, Chriull said:

Although this tumbling most likely was initiated by some small "level differences/bumps", as in reality flat ground is not something one can count on...

When rider hit objects, forces are at different level and tumbling will be likely. Friction is much more rider friendly.

2 minutes ago, Chriull said:

The need to balance to stay upgright or starting to tumble/spin if one cannot balance is a very strong sign of a torque acting on ones body...

The differences in inertia at different spinning axles are huge. The one on the video is the easiest to spin.

[Chriull]

22 minutes ago, Eucner said:

Rider is measured by his center of gravity.

No. Center of gravity is a simplification which is valid and usefull way to solve some problems. But this is not true for each problem as in this case.

[Eucner]

18 minutes ago, Chriull said:

But this is not true for each problem as in this case.

Could you elaborate on this. What makes it not applicable and what concept would be better?

[RockyTop]

 

3 hours ago, Eucner said:

Hitting knees into the ground don't put people into a wild forward spinning motion

Actually it does happen. It is called cartwheeling. It is one of the worst things that can happen to a person on o motorcycle. We do not see it much on EUCs yet but we are getting there with the faster wheels. This is why we want slippery plastic body armor. 

[mrelwood]

1 hour ago, Eucner said:

Could you elaborate on this. What makes it not applicable and what concept would be better?

I don’t know if there is any single concept that should be used. But even if the CoG slows down gently and doesn’t cause much of an impact, the rider could die from a brain trauma if one’s head hits the ground hard due to rotating around the CoG. In that case measuring or calculating the forces that apply to the CoG are pretty meaningless.

[Eucner]

37 minutes ago, mrelwood said:

I don’t know if there is any single concept that should be used. But even if the CoG slows down gently and doesn’t cause much of an impact, the rider could die from a brain trauma if one’s head hits the ground hard due to rotating around the CoG. In that case measuring or calculating the forces that apply to the CoG are pretty meaningless.

Gravity is not very gentle as we know. You would need something like this for your scenario.

[mrelwood]

I was talking about a situation where one’s flailing limbs slows down the fall. And especially the knees, which are the most common part to touch ground first in an EUC crash, and which could also easily start the cartwheeling that was mentioned earlier.

[Eucner]

12 hours ago, mrelwood said:

I was talking about a situation where one’s flailing limbs slows down the fall. And especially the knees, which are the most common part to touch ground first in an EUC crash, and which could also easily start the cartwheeling that was mentioned earlier.

Knees hitting the ground is not a gentle touch however you do it. In the forward fall, impact force and friction in knees will create a 20 - 40 degrees forward lean of the body during impact. This can be enough to throw rider off balance. Tall and heavy riders have here easier time.

Edited August 8, 2021 by Eucner
grammar

[mrelwood]

11 minutes ago, Eucner said:

Knees hitting the ground is not a gentle touch however you do it. In the forward fall …

You are thinking about a crash very theoretically. An EUC crash is almost never a direct forward fall.

 The last time I crashed, my knee hit first, and as it slide away from under me, my CoG slowed down relatively gently.

11 minutes ago, Eucner said:

… impact force and friction in knees will create a 20 - 40 degrees forward lean of the body during impact.

I’m sure it depends a lot on the angle of the knees and thighs, as well as the position of the CoG in relation to the point of impact.

Am I wrong in guessing that you are lucky enough not to have crashed with your EUC at speed? Watching a few crash videos would give some context to the various ways one can crash.

[Chriull]

18 hours ago, Eucner said:

Rider is measured by his center of gravity. Spinning itself doesn't change downward speed, because it is introduced by a horizontal force. If upper body is moving downwards, will lower body move upwards. Only body parts taking vertical impact will slow down vertical speed.

....

 

17 hours ago, Eucner said:

Could you elaborate on this. What makes it not applicable and what concept would be better?

The best concept would be to stick with the well known and understood principles of basic mechanics. Eidely elaborated in countless books, school classes, courses,...

As feets/knees touching the ground are decelerated by friction a torque is introduced on the body turning it down. Nothing more, nothing less.

No spinning or turning around the CoG. If one does not hit some barrier at high speed and flies off. In this case one could spin around ones CoG, but this is some very different scenario.

[Eucner]

1 hour ago, Chriull said:

The best concept would be to stick with the well known and understood principles of basic mechanics. Eidely elaborated in countless books, school classes, courses,...

The CoG is mentioned there all the time. What was the better concept?

1 hour ago, Chriull said:

As feets/knees touching the ground are decelerated by friction a torque is introduced on the body turning it down. Nothing more, nothing less.

Where would be the pivot point of this torque?

[Tryptych]

On 8/4/2021 at 12:25 PM, mike_bike_kite said:

All suspension wheels are more difficult to maintain judging by all the disassembly videos

Fact is that V11 is not very complex - there are just a lot more screws. The design is brilliant and once you open it up you realize the suspension is incredibly simple.  After 3000km it's never needed any maintenance and has been nothing but a good thing. 

There is no reason to not have suspension - same as your car, or truck, or train, etc etc... It's just better...

 

 

[Eucner]

20 hours ago, mrelwood said:

An EUC crash is almost never a direct forward fall.

I know. I think we can't cover all possible ways to crash in an off topic conversation. It would be a worth of own thread.

[Nostris]

On 8/2/2021 at 9:15 PM, AtlasP said:

The V12 was not (at least originally) a pure 'successor' to the V11. Rather the V11 (IM's first suspension wheel) and the V12 (IM's first 100v wheel) were being developed in tandem/independent of one another, without IM knowing if either would become product viable. Ultimately it turned out the development of both were successful and both are coming to market.

Basically the V11 and V12 were two possible alternate futures from IM (either they focus on suspension sticking with 84v speeds, or they focus on 100v speeds irrelevant of suspension), and we just happen to be getting both futures on top of one another (albeit in different models). In which case it could be the V-number-bigger-than-12 that might unite and provide both suspension and 100v speeds.

I always got the idea that the V11 was Inmotions first attempt at a suspension wheel, and it seems a pretty good first attempt. The V12 is surely the successor to the V10, which I guess will be retired before long as it is not hugely better than the V8f…. There no longer seems to be a reason for the V10. 

[yoos]

26 minutes ago, Nostris said:

The V12 is surely the successor to the V10, which I guess will be retired before long as it is not hugely better than the V8f…. There no longer seems to be a reason for the V10. 

I don't think the V10F should or would be retired any time soon. Like car or motorcycle manufacturers, it makes sense for EUC companies to have a lineup that covers all use cases. The V10F is already polished enough, so the only cost is to keep producing it while there is demand. The V12 is roughly 50% more expensive and 50% more heavy. At the same time the V10F is a reasonable step up from V8F which is just a bit too slow and short-ranged for some users (however the V8S creeps close). There is definitely demand for ~20kg commuter wheels with decent specs but without the weight or price of performance wheels, especially in crowded cities where EUCs ride on the pavement/bicycle lanes (and thus do not need speed and prefer nimble and light wheels) and have to be carried upstairs.