Originally Posted by
old's'cool
Interesting... While it (i.e. the infrared video) shows the temperature, and you mention a correlation with link angularity, it does not follow that this is a causal correlation. it is highly likely that the chainring, having the highest thermal mass and heat transfer, is quickly dissipating any heat that is generated (and thereby staying close to the ambient temperature). In second place in these properties would be the sprocket (smaller, steel), and bringing up the rear are the jockey wheels (smallest, plastic).
Originally Posted by
nomadmax
Bunkie
I'm not an engineer but I have stayed in a Holiday Inn
I would say the chief reason larger pulleys are touted as "better" is that they reduce the angle/bend of the chain when it goes around the pulleys, thereby reducing friction. I'm sure they have some kind of fancy bearing in them that further reduces friction but I don't know that to be a fact.
Turns out the night at the Holiday Inn worked for me
Right from the horse's mouth:
"Technically, it would. But when you think of how a drivetrain operates — a chain winding its way over chainrings and then around a cassette, and finally, through the serpentine pulley system of a rear derailleur — the more significant cause of friction is actually the angle the chain reaches as it wraps through the rear derailleur.So by opening up those angles and making them less sharp, the chain can articulate less than it would when it passes around smaller pulley wheels. Voila! Less friction."
“The biggest advantage is friction reduction, or increasing the efficiency of the drivetrain,” says Smith. “There’s a couple of ways the OSPW reduces friction. In other words, it’s part of a system. The biggest factor is the larger pulley wheels. The less amount a chain has to articulate as it engages and disengages the pulley wheels, the less friction is produced. The next thing is on the larger pulley wheels, the bearings spin slower so you don’t have as much drag there.”
https://www.velonews.com/gear/tour-d...ys-should-you/