agattu 11 tooth sprocket

[tangent]

Thanks Flecc, I thought this must be the case as I could not see how it would work the way it does otherwise. I have calculated that with a 28" wheel, in gear 7 of the 7 speed Agattu, the wheels are rotating at about 114 rpm at 15 kmh, which means that the motor sprocket must be rotating at about 172 rpm with a 21T/9T combination. Above this 172 rpm then the assist factor starts to be reduced according to your formula

1 - ( [kph - 15] / 9 ) = assist factor

In my case then the cutoff point for the assist level is boosted by 12/9 by the 12T sprocket and 21/18 by my 18T hub sprocket, resulting in a maximum speed of about 23 kmh before the assist level starts to be reduced.

The 12T sprocket allows me to pedal with 33% higher cadence before the assist level starts to drop, which for me is the main benefit.

There is a downside of course - As the unit operates in the way you describe, this means that the assistance must be reduced from 1:1 in normal mode to 1:0.75. In higher mode it must be reduced from 1:1.3 to 1:0.975.

Perhaps I will upgrade to a 2011 Kalkhoff next year with 1:2 assistance!

 

[flecc]

There is a downside of course - As the unit operates in the way you describe, this means that the assistance must be reduced from 1:1 in normal mode to 1:0.75. In higher mode it must be reduced from 1:1.3 to 1:0.975.

Perhaps I will upgrade to a 2011 Kalkhoff next year with 1:2 assistance!

Yes, they are playing a smart game, increasing the power levels year on year, so making each one more desirable than the last! And of course there's also the 300 watt units now, a further gain.

I wouldn't place quite as much emphasis now on the Japanese legal power equation that the first units worked to, and still do in Japan of course. I have the impression that some variation may be creeping in for the overseas market now, though the variation is probably very small as yet since they cannot spoil the unit's efficiency and range which result from that way of working.
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[tangent]

I wouldn't place quite as much emphasis now on the Japanese legal power equation that the first units worked to, and still do in Japan of course. I have the impression that some variation may be creeping in for the overseas market now, though the variation is probably very small as yet since they cannot spoil the unit's efficiency and range which result from that way of working.
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This is interesting. The one improvement I think they could make for western markets is to up the maximum cadence level before the assitance level reduction, perhaps with a steeper reduction slope. Essentially doing what people already do with the motor sprocket upgrade. They could still make the bike road legal of course by appropriate gearing changes. 39rpm really is absurdly low. I even find the 52rpm of my bike is too low for me now, generally I use around 70 I think.

 

[flecc]

This is interesting. The one improvement I think they could make for western markets is to up the maximum cadence level before the assitance level reduction, perhaps with a steeper reduction slope. Essentially doing what people already do with the motor sprocket upgrade. They could still make the bike road legal of course by appropriate gearing changes. 39rpm really is absurdly low. I even find the 52rpm of my bike is too low for me now, generally I use around 70 I think.

Yamaha appear to have adopted a later reduction point and steeper gradient on their copy-cat unit, but some including A to B magazine have been complaining that it operates in a seemingly harsh manner, the changes too abrupt. Obviously Panasonic will have to be wary about going too far down that road.

The big problem with driving the chain faster for a higher cadence range is getting the gearing back down to legality. For EU legality the Panasonic unit already has a smallish chainwheel (41 tooth) and has to use 22 and 23 tooth rear sprockets on the Nexus hub gears, near the largest made which is 24 tooth. We could end up with rear sprockets looking like chainwheels! To make the necessary adjustments internally could mean going back to internal multi-stage gear reduction, something they've just abandoned from the old unit to gain efficiency with single stage reduction.

It's really a case of suffering necessary compromises for simplicity and efficiency or scrapping the excellent basic design and starting again.
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