Author Topic: "Bursting" the rear Michelin on a 600km young 1200GS LC - final chapter. (Read 22480 times)

2wdrift · « **Reply #160 on:** April 14, 2015, 12:13:36 am »

Quote from: Geriatrix on April 13, 2015, 05:20:59 pm

Quote from: 2wdrift on April 12, 2015, 10:01:12 pm
If the bike was moving at 180km/h the tyre would be moving at the same speed at its normal radius. If that radius increased by a third (due to delamination) you could be looking at a piece of rubber being flung around at a fair bit over 200km/h. I would hazard a guess that even a 4-5mm stainless steel plate would be wrecked by that?

The bit of tyre that is in contact with the road moves at 0km / hour ( it is in contact with the road ).

The hub travels at the speed of the bike.

The bit of tyre at the top is traveling at twice the speed of the bike.

If there is a bit of rubber attached to the tyre by a length of cord it is going faster.

I am sure that a bit of rubber would go through a lot of steel under those conditions.

An under inflated tyre would fragment rapidly at that speed.

I have tried explaining that to a few friends but have not been overly successful. So basically if a tyre were to delaminate at 100km/h and it extended a third further away from the hub/fulcrum it would be hitting the mudguard at a good 130km/h?

Geriatrix · « **Reply #161 on:** April 14, 2015, 04:36:34 am »

The tyre in contact with the road moves at 0km per hour.
The hub at 100km per hour.
The top of the tyre 200 km per hour
The extra bit is 1,3 times further from the hub so it will be moving at 260km per hour, provided that it hits nothing as it goes around, and can accelerate freely. I do not know how the actual path and speed can be measured.

TheBear · « **Reply #162 on:** April 14, 2015, 08:14:50 am »

I am no scientist or mathematician. I do know one thing. If that ever happens to my bike I would appreciate lots and lots of stuff between my posterior, inclusive of other soft bits, and that piece of tire!

Manic · « **Reply #163 on:** April 14, 2015, 08:42:07 am »

Quote from: Geriatrix on April 14, 2015, 04:36:34 am

The tyre in contact with the road moves at 0km per hour.
The hub at 100km per hour.
The top of the tyre 200 km per hour
The extra bit is 1,3 times further from the hub so it will be moving at 260km per hour, provided that it hits nothing as it goes around, and can accelerate freely. I do not know how the actual path and speed can be measured.

So if the actual bike is moving at say 250kph, how fast will the tyre turn THEN?

Jakkals · « **Reply #164 on:** April 14, 2015, 08:50:13 am »

So if the actual bike is moving at say 250kph, how fast will the tyre turn THEN?
[/quote]

Baie viniger as wat jy kan dink.

Geriatrix · « **Reply #165 on:** April 14, 2015, 08:53:02 am »

The top of a normal tyre would be moving at 500km per hour compared to the road ( actually a little faster since the bottom of the tyre is usually slightly indented by the road, and the top is slightly pushed out by inertia and centripetal force, so the top is further from the hub than the bottom ).

2StrokeDan · « **Reply #166 on:** April 14, 2015, 08:55:58 am »

Can a GS1200WC actually do 180??

This is the question.

silvrav · « **Reply #167 on:** April 14, 2015, 08:56:32 am »

Quote from: Geriatrix on April 14, 2015, 04:36:34 am

The tyre in contact with the road moves at 0km per hour.
The hub at 100km per hour.
The top of the tyre 200 km per hour
The extra bit is 1,3 times further from the hub so it will be moving at 260km per hour, provided that it hits nothing as it goes around, and can accelerate freely. I do not know how the actual path and speed can be measured.

my wife slaps at about 20km/h (rough estimate) so anything faster then that I really would want it to touch me

Geriatrix · « **Reply #168 on:** April 14, 2015, 08:58:46 am »

Quote from: 2StrokeDan on April 14, 2015, 08:55:58 am

Can a GS1200WC actually do 180??

This is the question.

Yes, it has good brakes so with enough warning it can slow down to 180km / hour.

2StrokeDan · « **Reply #169 on:** April 14, 2015, 08:59:42 am »

Quote from: Geriatrix on April 14, 2015, 08:58:46 am

Quote from: 2StrokeDan on April 14, 2015, 08:55:58 am
Can a GS1200WC actually do 180??

This is the question.

Yes, it has good brakes so with enough warning it can slow down to 180km / hour.

THROTTLE JOCKEY · « **Reply #170 on:** April 14, 2015, 09:02:14 am »

One for you cleva boys

does the bike hang or push down on its spokes assuming it is a spoked rim.

ETS · « **Reply #171 on:** April 14, 2015, 09:03:15 am »

Quote from: THROTTLE JOCKEY on April 14, 2015, 09:02:14 am

One for you cleva boys

does the bike hang or push down on its spokes assuming it is a spoked rim.

Hang. Duh

Mr Zog · « **Reply #172 on:** April 14, 2015, 09:03:21 am »

Quote from: THROTTLE JOCKEY on April 14, 2015, 09:02:14 am

One for you cleva boys

does the bike hang or push down on its spokes assuming it is a spoked rim.

It hangs...

Geriatrix · « **Reply #173 on:** April 14, 2015, 09:21:51 am »

Quote from: THROTTLE JOCKEY on April 14, 2015, 09:02:14 am

One for you cleva boys

does the bike hang or push down on its spokes assuming it is a spoked rim.

Cut the top spokes and see what happens.
Cut the bottom spokes and then see what happens.

Tell us, and we shall all know.

THROTTLE JOCKEY · « **Reply #174 on:** April 14, 2015, 09:42:22 am »

You already have two correct answers

GRIM · « **Reply #175 on:** April 14, 2015, 10:46:17 am »

My Physics lecturer would have a fit with all these simplifications...

Geriatrix · « **Reply #176 on:** April 14, 2015, 10:54:27 am »

Quote from: GRIM on April 14, 2015, 10:46:17 am

My Physics lecturer would have a fit with all these simplifications...

I am sure that you are correct, but a decent explanation would take at least twenty pages, and offer little precision.

2wdrift · « **Reply #177 on:** April 14, 2015, 11:14:11 am »

Quote from: Geriatrix on April 14, 2015, 04:36:34 am

The tyre in contact with the road moves at 0km per hour.
The hub at 100km per hour.
The top of the tyre 200 km per hour
The extra bit is 1,3 times further from the hub so it will be moving at 260km per hour, provided that it hits nothing as it goes around, and can accelerate freely. I do not know how the actual path and speed can be measured.

Yes I was referring to the impact of a loose piece of rubber. As the hub an bike are moving at the same speed the maximum speed at which the tyre could hit the mudguard would be around 130km/h.

Once you start thinking about exactly how this stuff works high speed becomes very much less inviting all of a sudden.

Geriatrix · « **Reply #178 on:** April 14, 2015, 11:42:41 am »

Do you mean the relative speed between the bike and bit of loose rubber?
To calculate that would depend upon so many factors and change so quickly during the revolution that the physics is way out of my league. It would be enough to hurt if it hits you.

TheBear · « **Reply #179 on:** April 14, 2015, 11:52:01 am »

Quote from: GRIM on April 14, 2015, 10:46:17 am

My Physics lecturer would have a fit with all these simplifications...

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

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".