BBSHD PAS cadence at 48V?

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kachou   1 mW

1 mW
Posts: 18
Joined: May 11 2016 10:02am

BBSHD PAS cadence at 48V?

Post by kachou » Oct 25 2016 5:38am

Dear fellow ebikers,

I am enjoying an awesome BBSHD / 48V setup that I built with your help (see here: https://endless-sphere.com/forums/viewt ... 28&t=80352 )

I am now trying to perfect the beast, with the same objective: that my wife can climb Alpine passes at low speeds (around 9km/h) with me (on a non electrical bike), while pedaling a bit (and therefore being at the same cadence as the BBSHD).

With the mighty mini Luna chainring, the chainline was terrible, and I wasn't able to use all the rear cogs. I removed 2 of them and used spacers, but it was still not satisfactory.

So... I bought a second-hand Rohloff IGH 14speed that I found, and I am now calculating the best gear ratios.
However, I was not able to find the default cadence speed of the BBSHD, for each PAS level. <<< this is my question

I understand the motor needs to run fast for best efficiency, but my wife cannot pedal at the craziest speeds.
If anyone is able to help me on this question, it will allow me to choose the gear ratio for my Rohloff:
either 30 front chainring and 13 rear cog or 46 front chainring and 17 rear cog.

My calculations for each gearing:

30/13
Speed at 60RPM for each Rohloff gear (km/h)
1 5,22
2 5,91
3 6,73
4 7,65
5 8,67
6 9,87
7 11,22
8 12,75
9 14,47
10 16,47
11 18,69
12 21,22
13 24,15
14 27,42

46/17
Speed at 60RPM for each Rohloff gear (km/h)
1 6,12
2 6,93
3 7,89
4 8,96
5 10,17
6 11,57
7 13,15
8 14,95
9 16,96
10 19,31
11 21,92
12 24,88
13 28,32
14 32,15

Thanks for your help! :D

dustNbone   10 kW

10 kW
Posts: 948
Joined: Mar 13 2016 9:59pm
Location: Vancouver, BC

Re: BBSHD PAS cadence at 48V?

Post by dustNbone » Oct 27 2016 11:00pm

It's tricky because the motor isn't going to be super happy at 60RPM, for a long hill climb you'd be better off taking a rest and letting the motor pull you up at 100RPM or so. If you're climbing mountain passes with it, you're going to get more range that way vs. having the motor lugging at 60RPM. This is going to be the case regardless of the range of gear ratios you're using.

All other things being equal, I'd go with the larger rings just for the sake of making life easier on your chain.

kachou   1 mW

1 mW
Posts: 18
Joined: May 11 2016 10:02am

Re: BBSHD PAS cadence at 48V?

Post by kachou » Apr 30 2017 6:47am

it took me a while to get back, but thanks for your answer dustNbone!
Still working on this.

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waynebergman   10 kW

10 kW
Posts: 956
Joined: May 07 2011 4:20pm
Location: Pender Harbour British Columbia Canada

Re: BBSHD PAS cadence at 48V?

Post by waynebergman » May 02 2017 11:47pm

Its great you have the 14 speed R hub. I would love to have one of those.

Just so you know, that with the gearing coming out of the Bafang motor not being geared down ENOUGH (in my opinion) you will never be able to add any kind of meaningful pedal input for efficiency with this drive system.For the life of the motors sake when climbing spin the motor up and just clown pedal or forget pedalling all together. When the motor is in its happy zone you would have to be pedaling like a mad man to add any meaningful input and there is no way around this issue because of Bafangs choice of gear reduction on the HD100. This being said its a good drive for the money I feel but it is too bad it is not geared down much much more, like 30% more. If you are doing long climbs just gear way down and spin up the motor and realize during this period on the climbs you are saving the motor by having it in its happy zone and don't worry about using the pedals to help the drive train. Its OK to lug the motor on the flats in a high gear so you can get some exercise and feel like you are giving some pedal assist but forget about it for long or hard climbs. Lug your motor on the flats and down hills only if you feel you want to have the feeling of giving some pedal assist.

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