Author Topic: How many gears do you need on an electric bike? Is a Rohloff necessary?  (Read 15882 times)

Andre Jute

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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.

***

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.

***

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?

***

I hope the other owners of electrified bikes will chime in with their experience and conclusions.
« Last Edit: May 26, 2015, 06:49:21 PM by Andre Jute »

ians

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #1 on: November 26, 2013, 04:55:32 PM »
A very good (and for me, timely) post Andre.  I think that, sadly, you are right.  I say sadly because my Rohloff has become somewhat redundant since I went electric.  

I have the Sparticle kit fitted to my Raven Thorn.  Like yours, it has the 250Watt motor.  I have a twist throttle which I engage when I can't manage on my own; perhaps a headwind, hill or simple fatigue.  I use it as a last resort - most of the time I'm simply dragging extra weight around.  But when it kicks in, it really kicks in and it flies with little help from me.  Which is fun.

I bought the kit about 18 months ago as a temporary thing; I assumed it would help me recover from surgery and when I had regained my fitness I would sell it.  But it hasn't worked out that way and it's now the only way that I can manage a decent ride (over 10 miles).  A bit of background; 3 years ago I had a bowel cancer secondary in my left lung.  Surgery removed half the lung and radiotherapy fried the remainder, resulting in pulmonary fibrosis.   Surgery also mangled the nerves around my heart, leaving me with heart problems.  In the run up to surgery I was doing 20 miles each day before breakfast on my road bike to get in as good a shape as possible for the operation.  One of the nurses said afterwards that mine was the healthiest lung they'd ever had to throw away .... (I was in a ward full of smokers).

Electric assist is now a permanent feature of my bike riding and I am now beginning to think the unthinkable - do I sell my beloved RT and buy a pedelec?  I'll say up front I don't like them; the look that is.  And most are derailleur..... .  Nuff said.

But I do like the idea of the weight low down around the BB.  And perhaps my riding experience might become smoother, as I integrate muscles and motor in a way that I cannot with the kit motor; it's a bit all or nothing at the moment.  As for the Rohloff? I probably use 4-5 gears at the moment; so for me your analysis is spot on, Andre.

Much to think about - thanks for the post.



 
« Last Edit: November 26, 2013, 04:57:33 PM by ians »

Andre Jute

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #2 on: November 26, 2013, 06:57:25 PM »
Thanks for broadening the scope of the experience/remarks in my article, Ian. That was exactly why I was so keen for everyone else with an electric motor to chip in.

The pedelecs I've tried were without exception dull shopping bikes for the undiscriminating, including the highly regarded Giant one. (I get offers from their owners for my bike all the time, and the ones I've permitted to try my bike -- the more mature ones who can be counted on not to hurt themselves or the bike by pressing too hard on the throttle -- are especially insistent.) I'm not so sure you will like a dedicated pedelec after the Raven, even a Raven a little unbalanced by all that power and weight in the front wheel.

You know, you already have a connection to people with expertise in converting a bike to electric operation. You could ask the people who did your conversion if they want to fit a Bosch motor to your Raven. I imagine you'd have no problem selling the previous installation on as a wheel and control set.

Danneaux

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #3 on: November 27, 2013, 01:53:33 AM »
Quote
I am now beginning to think the unthinkable - do I sell my beloved RT and buy a pedelec?
Hi Ian!

I understand your situation and also how hard it would be to part with your beloved Raven Tour. Even if the Rohloff proved more than you need with electric assist (pedelec), the rest of the bike works and if you only use 50% of the available ratios, it seems no harm done.

I did a little digging and found there are retrofit kits for bottom bracket-mount motors. This is not my realm, so I have no idea as to the quality or applicability or even if they could be made to fit an eccentric bottom bracket as on your RT. If they worked, then this might be a possible solution that would allow keeping your bike. some examples among many:
SunStar iBike:
http://www.sunstaribike.com/en/why-ibike-2/why-retrofit/
Installation video: http://www.youtube.com/watch?feature=player_embedded&v=u5Mo56_D50g
Vivax/GruberAssist (which, sadly, doesn't look as if it would work with an EBB; the motor fits *inside* the seat tube)
http://www.vivax-assist.com/en/produkte/vivax-assist.html
video: http://www.youtube.com/watch?feature=player_embedded&v=wGYqKBUEelw
http://www.bikeradar.com/us/gear/category/bikes/electric/product/review-gruber-assist-conversion-kit-42720/
Older review from UK supplier: http://electricmountainbikes.blogspot.com/2008/11/gruber-assist.html
Another from the same source: http://electricmountainbikes.blogspot.com/2010/04/forest-glider.html
And, for Le Tour aspirations, the possibility of "mechanical doping" (not): http://cozybeehive.blogspot.com/2010/05/did-cancellara-use-illegal-motor-power.html
Others:
An article surveying various mid-drive kits: http://www.electricbike.com/mid-drive-kits/
A (largely outdated) article surveying the mid-drive field of complete bikes: http://www.electricbike.com/mid-drive/
Cyclone-USA: http://www.cyclone-usa.com/installation.php
Eclipse eBikes kit: http://eclipsebikes.com/chainwheel-bottom-bracket-watt-ebike-p-1070.html
GnG Electric Kit: http://www.gngebike.com/middrivekit.htmWooshBikes kit: http://wooshbikes.co.uk/?cdkit

Hopefully helpful...

Best,

Dan.

ians

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #4 on: November 27, 2013, 10:20:00 AM »
thanks guys - very helpful replies.  Much to think about.

ian

Andre Jute

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #5 on: November 27, 2013, 10:14:05 PM »
Thanks, Dan. I looked up your links.

For now I think I'll keep my money in my pocket. I discovered a good rule about electrified bikes when I made my own installation.

Jute's Rule of NOT WASTING MONEY in Electrified Bikes
First, wait until all the maniacs at Endless Sphere have tested all the motors under consideration to destruction, and as unpaid beta-testers have developed all the necessary components and ancillaries, and then wait until the newer stronger components and ancillaries are packaged by reputable manufacturers into sets that bolt on without problems. You know which is the right motor and ancillaries when all the maniacs at Endless Sphere suddenly have it, as suddenly declare it yesterday's news, and en masse move on to a new, unproven, expensive fave. The new one is the one you don't want. You want the previous one, that they declared yesterday's news, that is now packaged by a reputable manufacturer in complete bolt-in set.

Currently the only competent, complete, attractive bottom bracket electrification kits are very expensive, and of doubtful legality. Even the cheap ones, for which you have to find your own controllers and batteries (another control nightmare if you don't know what you're doing), are still three or four times the cost of the best hub motor installations, and they are likely to give continuous trouble, such as requiring new drive belts every three months, immobilizing the bike until spares arrive from China.

As an additional matter, you just have to look at those lash-up jobs currently on the market to grasp that however well they're made -- and these aren't yet, except for the expensive European ones -- they are intrinsically more complicated than a hub motor, with many more components generating friction against each other and wearing, definitely very high maintenance installations.

***

As a really simple but disabling matter to our sorts of installations, how do you, when the bottom bracket width is fixed, get the Rohloff chain line of 54mm on these Chinese motors? A hundred other questions like that. Someone will have to take the lead and sort all these questions.

***

When I suggested Ian speak to the people who installed the front hub motor into his Raven, I didn't have in mind any of these newer motors, but the OEM Bosch and Panasonic units which are proven and complete, and could perhaps be built into a Raven. In any event people who do it for a living will have considered the Bosch and Panasonic setups and will know whether it is possible.

***
The one I would love to give a go is the Gruber, which fits inside the seat tube, drives the bottom bracket by a bevel gear, and delivers 200W when you press the button. Probably pretty uncontrollable in traffic, and too expensive at nearly 3000 Euro installed to try and trash, but definitely clever and by all accounts well-engineered.

Andre Jute

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Of the ten most expensive electric bikes, according to this article, only four have Rolloff gearboxes. I wonder why the other six designers cheaped out. Interesting article:
https://www.electricbike.com/a-rohloff-on-an-electric-bike/

For newbies and lurkers:Several forum members run electric motors on Rolloff-hubbed bikes. If you're thinking of making the conversion, don't be afraid to ask. My installation is illustrated here: http://coolmainpress.com/BICYCLINGbuildingpedelec1.html

« Last Edit: October 25, 2015, 10:03:29 PM by Andre Jute »

Andre Jute

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #7 on: October 25, 2015, 10:17:22 AM »
Yesterday, into 30kph headwinds, I was very glad indeed to have the Rohloff gearbox fitted, especially heading dead into the wind as it whipped over the top of the sharpest hill on my route, where the motor was sucking all the battery's juice in the gear I normally use there just to keep me from rolling back. I geared down -- by rolling the rotary control with the palm of my hand, brrrrt -- into the low range I normally don't use, got moving immediately between newly possible pedalling effort and the motor multiplying the battery's current via the Rohloff's low range, and made it to the top without actually putting my foot down, which I consider a victory.

It's another consideration: you fit a Rohloff to get you there or get you home in extreme situations or an emergency, or to let you start rides a merely adequate/economic gearbox won't let you undertake. If you fit just enough gearbox, as in my list of adequate gearboxes further up this thread, on extreme days you'd better stay home. A Rohloff is a pretty good confidence-builder. Just don't let it turn you reckless.
« Last Edit: October 25, 2015, 09:58:36 PM by Andre Jute »

mickeg

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #8 on: October 25, 2015, 05:11:56 PM »
I expect to never use an electric bike.  But, if the only way you can get out on a bike is with one and if you actually do pedal up hills and get some physical benefit out of it, great.  I however have a bias, I live near a shop that sells electric bikes, that shop is located on a bike trail. And I am often passed by obese people that are coasting up hill, not pedaling, thinking how great it is now that they can get fit without effort and without sweating.

So much for my rant. 

***

Now the question was - how many gears do you need on an electric bike?

I was trained as a mining engineer in the early 1980s.  At that time, mining haulage trucks up to 85 ton capacity were mechanical drive and used multi-speed transmissions.  But haulage trucks over 85 tons were all electric drive because nobody at that time made a mechanical drive transmission that was big enough.  The electric drive consisted of wheel motors in the rear axle.  There were no changeable gears in the axle, only a gear reduction that allowed a very high rpm motor to spin a low rpm wheel.  Thus, the electric drive was single speed, not multi-speed.  The most common new trucks sold at that time had a capacity of 170 tons and usually had engines with about 1,600 horsepower.

So, my answer is based on my experience with mining haulage truck design, with an electric drive wheel, you do not need any more than an single gear - but there may be reduction gearing.  But, if you are also pedaling, you will need whatever gearing you desire for your pedals, based on your preference for cadence and based on the hills in your area.

If you are powering your crankset with the electric motor instead of an electrically driven wheel, you could get by with a single speed for the same reason.  But you probably would prefer more speeds for when you pedal.

***

Regarding wattage, I think I regularly pedal with an effort of about 120 to 140 watts when I am out exercising, more on hills but probably never over 200 watts.  Touring, probably fewer watts because I don't want to burn out after an hour.  I base these numbers on an exercycle that I use at a health club in winter that indicates my wattage.

I calculated after the fact that based on weight and slope and speed (assuming no rolling friction, no air friction) that I used 135 watts to climb Going to the Sun Road in July 2012 with a full load of camping gear on my Sherpa.  (As an engineer, it is pretty simple calculation.)  So, that provides confirmation of my capabilities.  More on that road here:
http://www.visitmt.com/listings/general/scenic-highway/going-to-the-sun-road.html

If electric bikes are being sold with 250 watt motors, now I know why obese people can coast up hill without pedaling and they can go that much faster than I can pedal up hill.  Thank you for the information about available motors and their wattage.

First two photos are of my Sherpa on Going to the Sun Road.  Third photo near Logan Pass, I took that photo on a different day from inside a shuttle bus while I was sightseeing.



JimK

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #9 on: October 25, 2015, 07:46:34 PM »
  I think I regularly pedal with an effort of about 120 to 140 watts

I have a rowing machine that I use sometimes in the winter. It has a power meter and my experience matches yours. I can put out 120 watts for a long time. 140 is a push. 200 is for maybe 15 seconds and will require some significant recovery. I can't really recover at 120, but at 100 or even 110 my heart rate will come back down.

Andre Jute

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #10 on: October 25, 2015, 10:30:03 PM »
Lovely photos, George. Thanks for the fascinating information about the 170 ton trucks -- landgoing ships!

I however have a bias, I live near a shop that sells electric bikes, that shop is located on a bike trail. And I am often passed by obese people that are coasting up hill, not pedaling, thinking how great it is now that they can get fit without effort and without sweating.

I have the same bias. I get to meet a lot of electric cyclists who see me -- from their cars,  you understand -- and stop me to talk to me about how they would like to ride where I ride, but the bike the idiots in the store sold them isn't strong enough to make the top of the hill or the battery isn't big enough to get "this far out of town". Actually, my battery is smaller than the battery on every single one of their bikes...

All that talk of getting some exercise is probably not dishonest but it is at the very least misleading; most of them weren't cyclists to start with, were never likely to become real cyclists, and wouldn't know how to go about it. They're just electrified versions of people who see a bike, think "I must exercise more", buy the bike on impulse, get all sweaty just once, and park the bike in the garage for good.

What amazed me when I first discovered it is how few of them took the trouble to understand the care and feeding of by far the most expensive part of the system, the lipo battery. Every single one that I meet has complaints about their battery clocking out unnaturally early. On questioning them, you discover all of them -- all, this is not hyperbole -- routinely ran the battery flat, or let it stand until it was flat, before recharging it, exactly the treatment most likely to ruin a lipo battery quickest.

***
Your remark about additional mechanical gears not being required when one has an electrical motor matches my experience. With the Bafang centre-motor I fitted, and recommend, this is even more true, because it has 9 "electronic ranges" or assistance levels which work extremely smoothly. On less demanding hills than mine, and especially if the rider uses the motor merely to fill in pedalling in trying conditions, or to break a loaded bike away from a standstill on a hill, that should be enough; one could easily view the electric motor as a substitute for a gearbox, though how efficient it would be pedalling all that weight around needs to be considered. But I live in the middle of roads that are only hills, and on days like yesterday, described in a post above, I was glad to have both the motor and the deep, deep range of the Rohloff to beat the full-frontal wind.
« Last Edit: October 26, 2015, 01:44:35 AM by Andre Jute »

mickeg

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Re: How many gears do you need on an electric bike? Is a Rohloff necessary?
« Reply #11 on: October 26, 2015, 12:44:06 AM »
...
What amazed me when I first discovered it is how few of them took the trouble to understand the care and feeding of by far the most expensive part of the system, the lipo battery. Every single one that I meet has complaints about their battery clocking out unnaturally early....

Tell them to get a dynohub, then they could use that 3 watt hub to recharge their battery.  <Insert chuckle here>.