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Author Topic: "Bursting" the rear Michelin on a 600km young 1200GS LC - final chapter.  (Read 23191 times)

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Offline big t

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #180 on: April 14, 2015, 11:58:46 am »
:(
it look to me like the tyre shredding like that  caused the electronis under the saddle to be totally destroyed.
unusual for a michelin anakee :)Donford will sort it no problem but i think Michelin will have some liability considering the bike only ha 600 km on the clock
 

Offline GRIM

Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #181 on: April 14, 2015, 12:18:26 pm »
Just for shits and giggles, and very approximately:

a 100g chunk of tyre, rotating 40cm from the axle, travelling at a linear speed of 180km/h (i.e. the bike is travelling at 180km/h) will have a force equivalent of 63kg.

Rotating systems store a lot of energy, and are generally not pretty when they go wrong.
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Offline GRIM

Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #182 on: April 14, 2015, 12:23:17 pm »
And if I pick up a new bike, and it destroys itself on the way home, I would expect a huge amount of goodwill from the dealer. A new bike would definitely be on my list of expectations.
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Offline THROTTLE JOCKEY

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #183 on: April 14, 2015, 12:26:54 pm »
My Physics lecturer would have a fit with all these simplifications...
 :deal:

That is why he is a physics lecturer and not a biker.   :ricky:

Now, the last time I passed physics was back in St. 7 and even then it was by a whisker.

Isn't rotational speed the thing here?  For the bike to move forward at 180km/h, the rear wheel must rotate at a certain speed and that speed is determined by the gear ratios.  Say the wheel turns at 6000 rpm and that piece comes loose, what force is in play?  That is apart from ä moerofa force".

Dont confuse 3 very different things that all play a part in moving the scoot forward

1. Force
2. RPM
3. speed (rotational and directional)

To answer your question it will depend on the size of the piece of rubber that comes loose

Force = mass x acceleration

plus you would have to assume that there are no external forces playing on the mass and that the acceleration is constant ( and I dont think it is).

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Offline TheBear

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #184 on: April 14, 2015, 12:44:10 pm »

Dont confuse 3 very different things that all play a part in moving the scoot forward

1. Force
2. RPM
3. speed (rotational and directional)

To answer your question it will depend on the size of the piece of rubber that comes loose

Force = mass x acceleration

plus you would have to assume that there are no external forces playing on the mass and that the acceleration is constant ( and I dont think it is).



I can't confuse anything.  I last passed physics in St 7, remember?  I don't know enough to confuse these forces.

What I do know is when I cast a lead weight and a sardine fillet into the sea, it goes a heck of a lot further, the faster the tip of the rods travels, or if cast by a longer rod at the same speed. 
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Offline Bundu

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #185 on: April 14, 2015, 12:45:39 pm »
I think the problem is actually the kinetic energy that the piece of rubber possesses and that energy is turned into 'work' when it hits something

Ek=0.5 x m x (v)^2

so speed plays a big role
 

Offline Coala

Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #186 on: April 14, 2015, 01:41:19 pm »
Here is the only equation that really matters:

1/2 cup of OMO to 1 pair of dirty underwear.
« Last Edit: April 14, 2015, 01:45:50 pm by Coala »
 

Offline alanB

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #187 on: April 14, 2015, 03:59:01 pm »
Another way of looking at this is:

Relative to the biker who is travelling on the bike, the wheel is not rotating around its contact point on the road,  but its axle, as one would intuitively expect.  Therefore while the top of the tyre is doing twice the speed of the vehicle relative to someone standing stationary on the side of the road, the top of the tyre is only doing the same speed as the vehicle with respect to the biker or the bike.

As far as force and stress goes:

Lets say a 2kg lump of rubber is doing 180km/h

And it hit something and stops completely in say 100ms (complete guess) then you can work out the deceleration  needed to do that from

V2 = V1 + a T

From that you can work out the force exerted by the rubber on what ever it hits which is simple F= m a

So that would give you

a = 180 /(3.6 *0.1) = 500 m/s2

thus force = 500 * 2 = 1000N  which equivalent to roughly 100kg

If the rubber happens to hit edge-on then that force is absorbed by a small area lets  guess and say 2 cm x 1 cm  = .0002 m2

So the stress exerted would be 1000/0.0002 = 5 MPa which should not cause steel to fail  :thumleft:

Just a quick thumbsuck   :P

Of course it all depends on lots of different things (eg the calc's above assume a loose piece of rubber flying through the air that stops when it hits something, not a flap of rubber hanging off the wheel, that is being driven by the bike's engine which obviously means you need to include the bike's torque and momentum into the calc)

Which ever way you look at it, this could get very nasty for anyone nearby those flying bits of rubber.
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Offline Snafu

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #188 on: April 14, 2015, 11:09:50 pm »
So, anyone know the cause yet, i heard the tyre picked up something from the road?
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Offline lecap

Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #189 on: April 16, 2015, 08:43:11 am »
Good grief did they teach you not to leave your common sense in your lunch box when tackling physics?

Do you know what happens to a bike when you try to rotate it at 6.000rpm ???

Do you realise that you should always use a value of m/s as "v"  in your formulas? Same as for mass always use values in g then you will indeed have results in N ::)
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Offline Moondog

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #190 on: April 16, 2015, 10:26:34 am »
Good grief did they teach you not to leave your common sense in your lunch box when tackling physics?

Do you know what happens to a bike when you try to rotate it at 6.000rpm ???

Do you realise that you should always use a value of m/s as "v"  in your formulas? Same as for mass always use values in g then you will indeed have results in N ::)

Yep - 'Speed' does not equal 'Velocity' as Velocity has a direction component.
« Last Edit: April 16, 2015, 10:27:18 am by Moondog »
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Offline Jughead

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #191 on: April 16, 2015, 10:53:46 am »
the top of the tyre is only doing the same speed as the vehicle with respect to the biker or the bike.


 ???

How on earth can the top of the tyre be doing the same speed as the bike?  Please explain.
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Offline 2StrokeDan

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #192 on: April 16, 2015, 11:26:52 am »
the top of the tyre is only doing the same speed as the vehicle with respect to the biker or the bike.


 ???

How on earth can the top of the tyre be doing the same speed as the bike?  Please explain.

The centre of the wheel, the axle, is doing the same speed as the bike.
 

Offline Bundu

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #193 on: April 16, 2015, 11:36:38 am »
the top of the tyre is only doing the same speed as the vehicle with respect to the biker or the bike.


 ???

How on earth can the top of the tyre be doing the same speed as the bike?  Please explain.

No, I think he's saying if the bike is doing 100, the top of the wheel is doing 100 relative to the bike, or 200 relative to the road
 

Offline Grrrr....

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #194 on: April 16, 2015, 11:57:02 am »
I blame Jan.

Offline Jughead

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #195 on: April 16, 2015, 12:07:55 pm »
the top of the tyre is only doing the same speed as the vehicle with respect to the biker or the bike.


 ???

How on earth can the top of the tyre be doing the same speed as the bike?  Please explain.

No, I think he's saying if the bike is doing 100, the top of the wheel is doing 100 relative to the bike, or 200 relative to the road

It can't!  The axle is doing the same speed relative to the bike.  The outside of the wheel is rotating around the axle so can impossibly be travelling at the same speed.
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Offline alanB

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #196 on: April 16, 2015, 12:39:50 pm »
the top of the tyre is only doing the same speed as the vehicle with respect to the biker or the bike.


 ???

How on earth can the top of the tyre be doing the same speed as the bike?  Please explain.

OK

Remember I'm talking about the speed of the tyre REALTIVE to the rider/bike.  The axle is connected to the bike, and moves along with the bike, so relative to bike/rider its velocity is zero (ignoring suspension movements )- so in that case the wheel is rotating around that point (remember to work out what is the point of rotation in complex situations you need to remember that the only point on a rotating body which has zero velocity is the axis of rotation, everything else is moving).

So relative to the bike/rider, the top of the tyre is moving forward at the same speed as the bike.

You can verify this easily:  While riding you can grab the axle bolt (if you have long double jointed arms) and it wont be moving relative to you.  But try grab the top of the tyre while moving - you will notice that it is moving relative to you at quite a high velocity, which will be the same speed as the bike - that's what I am referring to.

The distinction is important because the delaminating tyre whacked the bike, not a passer by who was standing stationary on the side of the road, hence the need to discern between relative velocities.
« Last Edit: April 16, 2015, 12:42:13 pm by alanB »
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Offline silvrav

Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #197 on: April 16, 2015, 12:57:11 pm »
So, has anyone been able to make contact with the gentleman to hear his side of the story.....  :patch:
 

Offline alanB

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Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #198 on: April 16, 2015, 12:58:38 pm »
Good grief did they teach you not to leave your common sense in your lunch box when tackling physics?

Do you know what happens to a bike when you try to rotate it at 6.000rpm ???

Do you realise that you should always use a value of m/s as "v"  in your formulas? Same as for mass always use values in g then you will indeed have results in N ::)

Um ja whatever
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Online Tom van Brits

Re: "Bursting" the rear Michelin on a 600km young 1200GS LC ...
« Reply #199 on: April 16, 2015, 01:02:20 pm »
So, has anyone been able to make contact with the gentleman to hear his side of the story.....  :patch:

I would also love to hear the outcome, but I am sure his insurance will cover the damages
It would be rather interesting to hear what that set his insurance back, I think more than a R100K!

Pity the rest of the thread and so many other threads as I noticed get stirred upside down by the 'Senior 2Stroke drol'