Author Topic: Chain reaction  (Read 9128 times)

Matt2matt2002

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Re: Chain reaction
« Reply #30 on: February 27, 2014, 07:37:53 pm »
EBB holding up well after x3 rides.
No chain slackness detected.

Just wondered what kind of strain is on the EBB to turn / change position, due to hard peddling?

Any thoughts?

Matt
Never drink and drive. You may hit a bump  and spill your drink

JimK

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Re: Chain reaction
« Reply #31 on: February 28, 2014, 01:42:04 am »
I think the strain on the EBB is not so small. Actually it must depend on where the EBB is positioned. I would think the worst spots are at extremes of its positioning, i.e. at 3 o'clock and 6 o'clock. In those positions, the entire force of your pedal downstroke becomes a torque twisting the EBB, because spindle is not centered over the bolts. Even at 12 o'clock, the intermediate position... your downstroke doesn't create torque directly, but the chain tension does. Seems like there ought to be a spot where the spindle is a bit toward the front, where the twisting from the crank just balances the twisting from the chain, and the EBB is just balanced on those screws. So probably there is a spot behind 12 o'clock where the twists add and those screws are really being tested.

Of course the spindle is only maybe 5 mm off center, so the torque is not so huge even when the forces are big. Still, I think the torque is big enough that e.g. tightening those screws to spec is worth the bother. I use a torque wrench there because it seems like a critical balance - I don't want to like push too hard and actually damage the EBB, but I want a nice dent that will hold.