Alfine planetary gearbox and rotation lag from standstill

Some gears in my Alfine hub have a definite rotation lag when starting
from standstill. The cranks move and for about half a second you can
feel the roller clutch engaging before the wheel starts turning which
means you don't have that rapid acceleration that you sometimes need
when crossing busy intersections.

Is this a trait of all planetary gear boxes, even those that use
ratchets instead of roller clutches?


Mike

On Jun 1, 9:22*pm, jk wrote:
Some gears in my Alfine hub have a definite rotation lag when starting
from standstill. The cranks move and for about half a second you can
feel the roller clutch engaging before the wheel starts turning which
means you don't have that rapid acceleration that you sometimes need
when crossing busy intersections.

Can you say which Alfine hub? There are several models.

Does the clutch engage gradually or abruptly after
that half second or so?

Is this a trait of all planetary gear boxes, even those that use
ratchets instead of roller clutches?

No.

There's a Rohloff Speedhub quirk that isn't in the same league
as what you describe, but as long as we're on the subject--

If I rock my Rohloff-equipped bike backward and forward
while trackstanding, keeping weight on a pedal (and thus
keeping the chain tensioned), I feel something move in
the hub as I transition from going forward to backward.
I don't know if it's properly called backlash because
even though the direction of motion is being reversed,
the direction of force on the gear train is not.
It's a momentary change of effort required, that feels just
like there were a small ledge on the road that you're
alternately rolling the tire up onto and then back off of.
If you don't trackstand you would never notice it.

Tom Ace

On Jun 2, 11:02*pm, Tom Ace wrote:
On Jun 1, 9:22*pm, jk wrote:

Some gears in my Alfine hub have a definite rotation lag when starting
from standstill. The cranks move and for about half a second you can
feel the roller clutch engaging before the wheel starts turning which
means you don't have that rapid acceleration that you sometimes need
when crossing busy intersections.

Can you say which Alfine hub? *There are several models.

SG-S501 black 8 speed.


Does the clutch engage gradually or abruptly after
that half second or so?

Gradually. It's a strange elastic type feel without rebound. A bit
like pushing against a hydraulic damper.

Mike.

On Jun 2, 8:40*am, jk wrote:
On Jun 2, 11:02*pm, Tom Ace wrote:

On Jun 1, 9:22*pm, jk wrote:

Some gears in my Alfine hub have a definite rotation lag when starting
from standstill. The cranks move and for about half a second you can
feel the roller clutch engaging before the wheel starts turning which
means you don't have that rapid acceleration that you sometimes need
when crossing busy intersections.

Can you say which Alfine hub? *There are several models.

SG-S501 black 8 speed.



Does the clutch engage gradually or abruptly after
that half second or so?

Gradually. It's a strange elastic type feel without rebound. A bit
like pushing against a hydraulic damper.

This is normal for the shimano 8 speed hubs. Break in & switching from
grease to oil lubrication both reduce the effect.


--
-Frank White

Tom Ace wrote:

If I rock my Rohloff-equipped bike backward and forward
while trackstanding, keeping weight on a pedal (and thus
keeping the chain tensioned), I feel something move in
the hub as I transition from going forward to backward.
I don't know if it's properly called backlash because
even though the direction of motion is being reversed,
the direction of force on the gear train is not.
It's a momentary change of effort required, that feels just
like there were a small ledge on the road that you're
alternately rolling the tire up onto and then back off of.
If you don't trackstand you would never notice it.

Some other gearhubs have an even more pronounced version of the same
effect. I have assumed it was either pawls or gears expanding their
respective constraints a bit-- winding up.

Recently I was able to ride a NuVinci hub hard enough to notice a
similar windup-and-release feeling with every hard pedal stroke in the
lower ratios. In that case I think what I'm feeling is the helical
cam that tightens up the roller mechanism under heavy torque load.

Chalo