What to do in a crash

[ken-ny]

In Judo, they teach something called "ukemi" to protect yourself when thrown.  Not sure if this translates to EUC accidents, but these Judo techniques do actually become an instinctual response to falling or being thrown.  If the initial blunt force from hitting the ground is a concern, Judo may be one way to mitigate damage. 

Judo Falling Techniques -- Ukemi | Judo Info

[dycus]

10 hours ago, level9 said:

Time for a typical person/height/weight/etc. to hit the ground going 0 mph (assuming no air resistance): 0.599ms.
Time to hit the ground if you are moving forward at, say, 20 mph: 0.789s. (the more forward momentum, the more time you have!).

Did you mix up your units here? 0.0006 seconds vs 0.79 seconds?

This is wrong anyway. An object dropped from a height of, say, 6 inches (let's call it EUC pedal height) with no forward momentum will reach the ground at the exact time as an object dropped from 6 inches going forward at 100mph. In either case, vertical speed starts at zero and increases at the same rate because acceleration due to gravity is the same.

Here's the Mythbusters showing that a bullet going the speed of sound hits the ground at the same time as a bullet simply dropped (with some small margin of measurement/practical test rig error)

 

Edited June 29, 2023 by dycus

[Eucner]

2 hours ago, level9 said:

And standing up on an EUC pedal raises it.

Ok, so you were not compering apples to apples. The speed does not change the time to fall down like your were indicating.

10 hours ago, level9 said:

Time for a typical person/height/weight/etc. to hit the ground going 0 mph (assuming no air resistance): 0.599ms.

You mean s not ms. 0.599 s equals to free fall of 1,76 m (10 ft 9 in). I'm tall, but my center of gravity height is much less.

10 hours ago, level9 said:

Time to hit the ground if you are moving forward at, say, 20 mph: 0.789s. (the more forward momentum, the more time you have!).

0.789 s equals to free fall of 3,05 m (10 ft). Looks too much for me. When using correct values the time to react and do something is significantly shorter.

I've survived my falls without any bigger damages with learned reflexes. Martial arts techniques works as is only in low speed. For higher speed crashes I have successfully adjusted my hand positions more forward. When most part of the technique comes automatically, there is just enough time to do slight intentional adjustments.

[level9]

5 minutes ago, dycus said:

Did you mix up your units here? 0.0006 seconds vs 0.79 seconds?

 

I actually misnomered the first one but I understand what you are saying.
The force of gravity being a constant, the times would be the same regardless of forward momentum. 

The height of the object for my calculation purposes was roughly head-height @ 1.7 meters.
So, 599 milliseconds for your head to hit the ground.
Your foot at 6" off the ground? 176 milliseconds.

This is calculated in a vacuum. So, these numbers are even too low if we add in air resistance.

My originally point remains. There is still time to react but not for conscious thought.

[Eucner]

3 minutes ago, level9 said:

The height of the object for my calculation purposes was roughly head-height @ 1.7 meters.
So, 599 milliseconds for your head to hit the ground.

To calculate the time to fall you need use the difference between heights of center of gravity before and after fall. Feet and head just fall at different speed.

3 minutes ago, level9 said:

Your foot at 6" off the ground? 176 milliseconds.

Times don't add up like that, because of constant acceleration.

[level9]

9 minutes ago, Eucner said:

To calculate the time to fall you need use the difference between heights of center of gravity before and after fall. Feet and head just fall at different speed.

20 minutes ago, level9 said:

The center of gravity isn't relevant. Everything falls at the same speed (in a vacuum) which was @dycus point.

 

10 minutes ago, Eucner said:

Times don't add up like that, because of constant acceleration.

 

I used the equations of motion from Newtonian physics. Double checked, still get the same numbers.

The force of gravity, g = 9.8 m/s2 ...
Time to splat: sqrt ( 2 * height / 9.8 ) ...

Edited June 29, 2023 by level9
incomplete post

[chanman]

I think there's some weirdness where your feet hit the ground first, I'm not sure if your head is free falling then or if you're being pulled to the ground by your feet getting dragged behind you.

[The Brahan Seer]

I think if you have the training to fall/roll then it is possible to reduce the impact forces and you would do it instinctively. But I think that requires lots of practice and doing so regularly. 

Maybe another option is to try and disperse the energy through as much surface area as possible. Trying to land on your whole body rather than say only one side. Which happened to me judging by my injuries.

This helps explaining the physics too..

 

[Rich Sam]

Old school skater here, I pad for the slide, knees and hands slide.  My preferred method is to slide on hands and knees as far as I can, if I must go prone on the ground I will roll.

[Bizra6ot]

Two pages of theories? All you have to do is place a camera on a tripod and overlean your wheel at 40mph in front of it to check whether you can perform a judo roll

[Cerbera]

14 minutes ago, Bizra6ot said:

Two pages of theories?

Oh FAR more than that - there are so many threads here running round the same old circular arguments for whether we can choose what we do when we fall, that it long since stopped being worth the debate as far as I am concerned. Everything that could possibly be said about both sides of the argument has already been said, and many many times before over the years. And so, whilst of course trying to not have any in the first place, when they do happen I take each fall as it happens, and make careful notes afterwards of my thoughts about it to see if there was anything I could have done better, could learn from, or where stuff went wrong. None of that involves any maths, equations or references other than the facts of each incident.

Edited June 29, 2023 by Cerbera

[The Brahan Seer]

9 minutes ago, Cerbera said:

Oh FAR more than that - there are so many threads here running round the same old circular arguments for whether we can choose what we do when we fall, that it long since stopped being worth the debate as far as I am concerned.

Of course! Thats because you have been following the forum for a long time. We all see the same idea's and questions come up from the newer generation when we've been here a while but it doesn't stop them being very valid and important points to discuss.

[Cerbera]

21 minutes ago, The Brahan Seer said:

doesn't stop them being very valid and important points to discuss.

True, true... but no 'side' can ever 'win'. It's like the bloody football - when will it come to some sort of conclusion ?!!  

Edited June 29, 2023 by Cerbera

[Eucner]

57 minutes ago, level9 said:

The center of gravity isn't relevant.

Wrong. Center of mass is a point where all mass can be thought to be concentrated in. It dictates the time to fall. Feet and head have also rotational speed, which is not relevant to it. A 1,75 m tall male standing knees bended on pedal height of 0,15 m will fall down in about 0,44 s.

57 minutes ago, level9 said:

Everything falls at the same speed (in a vacuum) which was @dycus point.

Right for the vertical speed of center of gravity. Parts of rotating object will also have different local speeds.

57 minutes ago, level9 said:

I used the equations of motion from Newtonian physics. Double checked, still get the same numbers.

The force of gravity, g = 9.8 m/s2 ...
Time to splat: sqrt ( 2 * height / 9.8 ) ...

Lets do it once again (2 * (1,7 + 0,15) / 9,81)^0,5 = 0,614 s. It is only 15 ms additional time. Far less than 176 ms.

[level9]

6 minutes ago, Eucner said:

Wrong. Center of mass is a point where all mass can be thought to be concentrated in. It dictates the time to fall. Feet and head have also rotational speed, which is not relevant to it. A 1,75 m tall male standing knees bended on pedal height of 0,15 m will fall down in about 0,44 s.

1 hour ago, level9 said:

We'll have to agree to disagree. In any case, even considering 440 milliseconds, that's still enough time. My original point remains 

[bpong]

i have a very loud bicycle bell plus a strong small flashlight (imalent DM21C) mounted on a small piece of wood that is about the size of a pistol grip.  i ride with this gizmo all the time on the euc.  it allows me to signal quickly for passing and alerting nearby pedestrians that im travelling along the street or bike lane.  now,  the stance i use is to hold this thing in front of me usually with my outstretched left hand and the right hand is beside it just for symmetry.  this positioning saved me twice when i fell forwards - my hands and arms contacted the surface first, and they were in front of me.  i dont stretch my arms out like im striking someone - its a rather relaxed arm position with arms bent at the elbow.  i dont know if i am fast enough to react to a sudden loss of stability,  to bring my arms and hands in front of me to help break my forward fall...

it does get abit tiring but i keep reminding myself of the previous falls and thats enuf to motivate myself to ride in this stance...

[The Brahan Seer]

I guess the other issue is even if we execute the perfect roll or slide the forces at play could and probably will still cause major injuries. The odds of being able to get it either totally right or get away with it go down the faster we go. The road surfaces are very rough these days and not smooth or uniform like in the past or in a skate park.

 

[mrelwood]

52 minutes ago, level9 said:

even considering 440 milliseconds, that's still enough time.

For reflexes to react, sure. For executing a forward roll, not so much.

 What you seem to be forgetting is that you can’t initiate a forward roll when your CoG is 10cm from the ground. Or 20cm. Or even 50cm.

 Tie a rope from your belt on your back and attach it to something sturdy. Take a position where you lean forward against the tightened rope, with a relaxed stance, hands down. Then ask someone to cut the rope anywhere in the next 3 minutes.

 Would you be successful with your forward roll?

Ps. I’m still waiting for the EUC cut-out roll videos.

[level9]

1 minute ago, mrelwood said:

For reflexes to react, sure. For executing a forward roll, not so much.

 What you seem to be forgetting is that you can’t initiate a forward roll when your CoG is 10cm from the ground. Or 20cm. Or even 50cm.

 Tie a rope from your belt on your back and attach it to something sturdy. Take a position where you lean forward against the tightened rope, with a relaxed stance, hands down. Then ask someone to cut the rope anywhere in the next 3 minutes.

 Would you be successful with your forward roll?

Ps. I’m still waiting for the EUC cut-out roll videos.

You're trying to explain to me why I can't do something I've already done - and numerous times. 

Look. You (or anyone else) can believe me - or not. It really makes no difference to me. I'm not the one that's going to be paying everyone else's medical bills 

[Planemo]

I love EUC ninjas. But the laws of physics always win.

[sbb]

36 minutes ago, Planemo said:

I love EUC ninjas. But the laws of physics always win.

Obligatory:

[mrelwood]

9 hours ago, level9 said:

You're trying to explain to me why I can't do something I've already done - and numerous times. 

You’ve done the tie rope test?? I guess you didn’t mean that.

I’m sure you have rolled out crashes, I don’t doubt that. Just that the circumstances have probably been crucially different than what we’re talking about here.

Again, would be nice to see it in a video, but it seems that while there are countless EUC crash, cut-out and overlean videos, NONE of them show how to roll it out. I find that strange.

 

9 hours ago, level9 said:

I'm not the one that's going to be paying everyone else's medical bills 

Not even for the damages when practicing the roll? 

[The Brahan Seer]

This roll out crash is probably one of the betters ways to do it.. 

14 hours ago, mrelwood said:

For executing a forward roll, not so much.

 What you seem to be forgetting is that you can’t initiate a forward roll when your CoG is 10cm from the ground. Or 20cm. Or even 50cm.

The roll isn't a forward roll in the classic school yard sense anyway. Its more of a roll from one shoulder to the opposite hip, so you are not rolling over the spinal cord.

The guys you see learning it start very low and work there way to standing and higher.

I get that its likely very hard to do above a certain speed and all the forces but the idea to scrub of as much forward momentum as smoothly as possible still holds.

 

[mrelwood]

23 hours ago, The Brahan Seer said:

The roll isn't a forward roll in the classic school yard sense anyway. Its more of a roll from one shoulder to the opposite hip, so you are not rolling over the spinal cord.

Good reminder, though I was thinking about an ukemi-style roll that isn’t completely straight. Nearly though. I’m sure there are different angles of roll. But their ability to absorb impact force varies as well.

In the video you linked to, the vast majority of his impact was directed to his knees, so without the roll he would’ve practically only fallen to his hands from his knees. That’s not much of a drop, and I can’t imagine it doing any of the shoulder damage we’ve seen at this forum. Hands forward enough and he could’ve slid on the sliding parts of his wrist guard, and absorbed the small fall by bending his elbows.

 I’m definitely not saying that he should’ve done that though, not at all. His approach was probably better so he’d slide less since he didn’t seem to have much gear to prevent sliding damage to his torso. Just linking this to the discussion of a roll minimizing damage. To me it didn’t seem that this specific roll would’ve lessened the damage that the impact part of his crash might’ve caused.

I carry stuff on my backpack that I definitely wouldn’t want to land on due to possible back pains or even damage. I know, it’s a bad idea without a specific backpack that can distribute the force more evenly. But since I do, if I were in this specific situation and if I had enough time to think about it, I think I would’ve chosen to just slide on my motorcycle jacket and pants.

[woke rider]

On 6/30/2023 at 6:53 AM, The Brahan Seer said:

This roll out crash is probably one of the betters ways to do it.. 

The roll isn't a forward roll in the classic school yard sense anyway. Its more of a roll from one shoulder to the opposite hip, so you are not rolling over the spinal cord.

The guys you see learning it start very low and work there way to standing and higher.

I get that its likely very hard to do above a certain speed and all the forces but the idea to scrub of as much forward momentum as smoothly as possible still holds.

 

This crash is terrifying to watch. But, my  only comfort is that, while I have sympathy for the rider, the crash could have easily been prevented by practicing safety first instead of power tripping and racing his peers. I am persuaded that all of that gear gave him over-confidence to take uneccessary risk. So in answer to @onewheelkoregro op, prevention prevention prevention.

I was bewildered about why the riders tilt back didn't engage. I am guessing that he had over leaned past the point of where his King Song tilt-back was  capable of engaging. So, lesson learned. Tilt back fails in an over lean.

Edited July 1, 2023 by earthtwin
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