I'm one of several forum members with both Rohloff and electric hubs on the same bike.
If you're a profoundly devoted Rohloffie, avert your eyes fearfully lest your faith be shaken...NOW!
Whether you need any gearbox, never mind a Rohloff, when you have an electric motor probably depends on how much torque the motor produces. My experience has led me to conclude that you can have a legal electric motor installation without the additional expense of a Rohloff gearbox. I stress that all my experience is on a lightweight touring bike with both a Rohloff and a motor specifically chosen for having the highest torque of any available. A heavy clunker or a cheaper, smaller, lighter but limper motor would both change the relationships. Also, while I use my bike as a utility bike, the fact is that I mainly ride on the lanes and small roads of a very hilly countryside; your situation may be different.
It's worth following the logic of selection and usage, because your intentions may be different.
I'm by training an economist and a psychologist, by profession a hidden persuader, by avocation a wordsmith, and many of my hobbies involve light but dangerous engineering, such as very high voltage tube amps. I justify everything rationally. I justified a Rohloff gearbox in a bike the price of a very nice preloved BMW as enabling me to live up a hill where my wife wanted to live, even though my heart wasn't up to cycling up the hill on my old bike with the 8 speed Shimano Nexus hub. When my health got worse, I added an electric motor to the Rohloff for the same reason. I've now had the motor for three years or so, and have discovered a few things.
Having studied what was available carefully, and calculated many times, I bought the
highest torque motor that could be passed off as falling within the pedelec regulations. We don't have any specific law about it where I live, as far as I know, but if you say you follow German or European regulations and point to a CE mark, that's generally the end of the matter. That said, I have never been questioned by the police about my bike, except to admire it and to ask if they could afford one for themselves. I haven't fitted the pedelec sensor; I intended to but then had two heart surgeries after which I was in no condition to bend over the bike, so I just use the throttle.
The motor I settled on is sold in Britain as 8-FUN. I don't know whose bright idea the name was. (I'm the advertising man who notoriously fell off his chair laughing when the Toyo company of Japan wanted to introduce their good-quality small car to the American market and told us earnestly that they though they might call it the Toyolet. We didn't get the account.) The best electric motor factory in China is called Bafang and the factory model number of the type I fitted is SWXK, and you want to get the version with the Q at the beginning, QSWXK, because it is specially finished for finicky European customers like me who're likely to reject the model sold to Chinese, Americans and suchlike as too crude. Now, what this actually is, as revealed by a close study of the specification (itself rather hard to come by), is a BPM motor very lightly breathed on to make it almost legal. The BPM is a famous off road motor that you can boost to 750 or a 1000W by simply letting it suck on a heftier battery -- more volts; it's totally illegal, of course. However that may be, the QSWXK is engraved 250W on the side, and delivers more torque than any other motor with that fig leaf of laser engraving, which made it legal under the old regulations. I haven't looked into it yet, but my understanding, from the forum here, is that the new regulations permit higher-powered motors than 250W. I'm not planning to fit anything higher-powered because on a wet road a front wheel motor like the QSWXK is probably as powerful as you want to go. More power should, in my not so humble opinion, be reserved for a bottom bracket motor to balance the bike better on the power. (And, of course — do I even have to say it? — the only place for the battery is on the central diamond, either the down tube or the seat tube; the rack mounted battery is a dangerous abomination, like adding a monstrous barbell to your bike's handling.)
When I was pretty weak after heart surgery I rode the same hills as before, just using more of the motor.
The controls are a bit confusing when you start. There is a dashboard with lights which go out to indicate the rate at which you suck power from the battery; the more lights out, the faster you're using up the battery, and the closer you are to the battery being unable to meet the demand. Still, my particular setup has never yet refused me; I never push the bike, but then I didn't push before the electrification either. (If the owner of a Rohloff-equipped bike has to push, ever, he's specified his transmission ratios badly, or monstrously overloaded his bike.) On the bottle battery itself, fitted on the "down tube" on my cross frame Utopia Kranich where it is in my sightline if I just drop my eyes, is a set of lights that indicate the amount of charge left in the battery. Actually, you have to press a button to see the battery lights -- I just forgot about it until now, because I never press the button because I've never used more than a quarter of the battery's juice, even on long rides including 20km of steep hills on half to three-quarter throttle.
It may just be that I have the right outlook, wanting real exercise. Other people, with Giant electric bikes, not my pedal pals, complain every time they stop me to ask if they can buy my bike instead that their electric bikes run out of juice too soon. I have only 8.8Ah in my battery, and ride much further and on tougher terrain than they do, so I suspect they keep the throttle open when they should be pedaling.
That sets the background. Mine is a reasonably common installation; there are members of this forum with the same motor on their Thorns as aftermarket fitments. There are some expensive whole bikes sold with the same motor and battery, and merely different, sometimes inferior, control panels, to distinguish them. A few overpriced boutique kits use this motor. Some off road bikes use this motor with a cutout for the 25kph controller. (I worked out how to do the same on my controller box but didn't build the switch: I'm more interested in traveling fast under pedal power than by motor.)
The most economical way to fit the QSWXK is to buy from 8-FUN on Ebay. 26":
http://www.ebay.co.uk/itm/8Fun-26-Ebike-Electric-Bike-Conversion-Kit-36V-250W-8F26F36B-/321028650823?pt=UK_Bikes_GL&hash=item4abecc7747 700C:
http://www.ebay.co.uk/itm/8Fun-28-700C-Ebike-Electric-Bike-Conversion-Kit-36V-250W-8F28F36B-/190694075181?pt=UK_Bikes_GL&hash=item2c6640ab2d Maybe you could do it cheaper buying direct from a Chinese dealer or maybe customs duties and courier charges in the end add up to more. I liked the service of 8-FUN; very agreeable people, and their kit is utterly complete; be sure to ask them to e-mail you the illustrated color instructions they wrote themselves, so that you can give the factory Chinglish a miss.
Okay, so I'm talking about a high torque motor in a touring bike, on the face of it legal (you may have to fit the pedelec sensor where you live to be legal but you don't need to use it, okay? -- the dashboard in the kit I recommend conveniently lets you switch at any time between pedelec and throttle), with a rider who at various times was weak and used quite a bit of motor, but mostly intends to pedal and use the motor only to keep his heart rate down to the permitted upper limit. We are talking about cyclists here, not Johnny-come-latelies who want to use an electric bike like a motorbike, who don't know what the pedals are for.
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So, how many gears do you need?
On the flat, for a shopping bike,
If you're a young, fit fixie rider,
You need only ONE SPEED if you have a high torque motor.
For a utility bike to ride up moderate hills,
And if you're young and fit, even steep hills.
You need THREE SPEEDS.
On a daily exercise bike in mixed terrain,
For recreational rides,
For a bike kept for guests who aren't regular cyclists,
You need FIVE gears.
For fast riding, meaning over the 25kph limit of most pedelec controllers out there right now, in mixed terrain including steep or long hills,
You need EIGHT gears.
In all these cases I have hub gears in mind, with the presently available ranges. The motor fills in the rest of the range between the hub gears and a notional derailleur setup.
That's it. That's everything that is
necessary.
At the moment I'm relatively fit. I ride everywhere I rode before, with judicious use of the motor. But I rarely use the lowest 7 gears of the Rohloff, only for climbing short sections of hills on tiny country lanes that are almost straight up.
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So, who would be able to justify an Alfine 11-speed or even Rohloff gearbox, getting on now towards five or six times the price of an 8 speed Nexus installation?
Well, if you're really very weak or sick, with no prospect of recovering, the Alfine or even the Rohloff may be well worth the cost for keeping your rides open, as I did when I was weak after heart surgery. On the other hand, if you know you will recover, you may reckon that the cost of using the bike to recover a bit sooner is too high. I didn't, I thought my Rohloff gearbox, in conjunction with the motor, in permitting me to ride up the steepest hill in West Cork probably three months earlier than I would otherwise have recovered to so strenuous a feat, earned its total cost right there, on top of the pleasure of permitting my wife to live up a hill in a house she liked. You live only so long, and you can't take it with you. What better to spend it on than good, honest German engineering you can ride up hills?
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I hope the other owners of electrified bikes will chime in with their experience and conclusions.
