Chain speed

[CharleyFarley]

Occasionally, around 3 a.m. I wake up and start to think. This morning something occurred to me about chain speed. If the top of a chain is moving at 2 mph, then it follows that the bottom of the chain is also moving at 2 mph but in the opposite direction.
Now if the bike is moving forward at 10 mph, then the top of the chain, relative to a fixed point behind the bike, is moving at 12 mph. Bike speed plus top of chain speed.
If this is true, then the bottom of the chain which is moving in the opposite direction toward the back of the bike, and moving relative to the same fixed point behind the bike, is moving forward at 8 mph. Bike speed minus bottom chain speed.
Therefore, the top of the chain is moving at 4 mph faster than the bottom of the chain.
What kept me awake for the rest of the night was trying to figure out if this is true or not.

 

[All uphill]

Yes.

You can go back to sleep now.

 

[ColinJ]

You forgot to factor in the fact that the bottom of the chain is not parallel to the ground; that should keep you awake tonight too!

 

[roubaixtuesday]

true or not.

It's true.

Sleep well.

 

[CharleyFarley]

You forgot to factor in the fact that the bottom of the chain is not parallel to the ground; that should keep you awake tonight too!

Thanks a lot!

 

[Smokin Joe]

And while the top of the chain is under tension the bottom is bouncing up and down, thereby covering a greater distance.

 

[ColinJ]

And while the top of the chain is under tension the bottom is bouncing up and down, thereby covering a greater distance.

And things got REALLY complicated for Cavendish's chain on today's Giro stage!

 

[Ming the Merciless]

You can also have a think about the energy required to move the chain against gravity when going uphill.

 

[presta]

And while the top of the chain is under tension the bottom is bouncing up and down, thereby covering a greater distance.

The front wheel travels a greater distance than the back one, too.