Crank drive versus hub drive

rog_london

Esteemed Pedelecer
Jan 3, 2009
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Harrow, Middlesex
I don't have any definitive ideas as to what's 'ideal' in terms of crank drive (such as Panasonic) as compared to hub drive (such as Wisper). However, I'd formed the opinion that Flecc was generally more in favour of the Panasonic system and its offshoots.

That was until ten minutes ago when I read Flecc's write up from 2007, when I was quite surprised to see he came down heavily in favour of hub motor drive.

I had suspected that the hub motor would be inherently more reliable, since with a crank drive you generally give a chain and derailleur a hard time due to the fact that it's liable to be transmitting much more power at least some of the time, because you could have a fit rider assisted by a couple of hundred watts (or so) of motor power.

Anyway, Flecc, respected and prolific contributor that you are, and as you read almost everything and get involved in nearly all of it, have you modified your opinion over the past few years? I'd be interested in anyone else's opinions too, of course, which is why I decided not to just PM you!

Rog.
 

flecc

Member
Oct 25, 2006
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That long article wasn't a change of opinion Rog, more to balance some of the views on hub motors at that time. As you've read there, the loss of power as speed reduces has balancing factors such as in terms of power needed at low climb speeds, something often not taken into account, especially at that time when many were bewailing the absence of any crank drives on the market.

The second part redresses any apparent imbalance though, since there I make clear that crank drive is preferable in the steepest hill/highest load circumstances.

That summarises my personal preference, the motor type according to circumstances. In a very flat area with few and moderate hills I'd prefer a good direct drive hub motor like a BionX for it's smooth and silent running. In a mixed area that didn't have the very steepest of hills, an internally geared hub motor, but in an area with some very steep climbs, a sophisticated crank drive like the Panasonic one.

However, it's not all about territory, circumstances are also important. In heavy traffic and congested conditions I like throttle control which mostly comes with hub motors, but for leisure riding in the country, I prefer a good pedelec which needs no attention from me other than just pedalling.

Living where I do, that means at least two bikes are best.
.
 
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Geebee

Esteemed Pedelecer
Mar 26, 2010
1,256
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Australia
Nicely balanced reply Flecc, pretty much agrees with my experience using the same hub for both crank and in wheel use.

The only area I would disagree and it is personal taste is that I would not use a direct drive hub due to not having a free wheel, as I like pedaling un-assisted quite a bit.
Some geared hubs are silent or close enough to it.
 
D

Deleted member 4366

Guest
A 200w hub motor is not a lot of fun when you come to any sort of hill, but a 200w crank drive will get you up without pedalling if you have low enough gearing. A 350w rated geared hub-motor with the right controller will get also get you up any hill without pedalling, and it puts no strain on the gears. As you go higher still in power, the strain on normal bike gears would be too much for a crank drive. Instead a direct drive hub motor, which has very little to break or wear out, would be a logical choice. Both systems could use either a torque sensor, a pedal motion sensor or a throttle, so that isn't an issue. So, which one has the advantage depends on how much power assist you have. Power is gradually increasing - even within the current legal limit - so the difference between them has become less and the simplicity and lower cost of a hub-drive gives added advantage. If the proposed increase in power goes ahead, I think that crank drives will start to fade out.
 

flecc

Member
Oct 25, 2006
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Power is gradually increasing - even within the current legal limit - so the difference between them has become less and the simplicity and lower cost of a hub-drive gives added advantage. If the proposed increase in power goes ahead, I think that crank drives will start to fade out.
I think there's a lot of truth in that, bike transmissions won't stand much more power without substantial upgrading, but that would bring unacceptable weight gains. However, I would like to see a cassette-like arrangement for derailleur sprocket clusters with the larger spindle rear hub motors, rather than be stuck with freewheels. I wouldn't like the hub motor future to be predominantly front wheel, especially with higher powers.
 

Eaglerider

Esteemed Pedelecer
Oct 25, 2011
369
47
East Sussex
As mentioned, I would have a Bosch crank drive on a proper mountain bike, and use it to climb the steep chalk hills on the Downs, then plummet down, and repeat.

For everything else, I prefer a hub drive. In an ideal world, perhaps some sort of hub drive gearbox could be installed, so to allow higher motor speeds to climb those pesky steep hills. A Da-Vinci set up maybe. I'm waiting for Flecc to invent a variomatic system, all inside the hub motor. Perhaps you could pop out to the shed and build one?
 

mike killay

Esteemed Pedelecer
Feb 17, 2011
3,010
1,627
I wonder if it would be possible to put to separate sets of windings in one motor casing. A Slow, high torque set for hills and a fast, low torque set for the flat. A micro processor could then decide which one to use at the appropriate moment
 

Eaglerider

Esteemed Pedelecer
Oct 25, 2011
369
47
East Sussex
Yes, that might do the trick.

I was thinking, that as the hub drives have a planetary gear set up, an interchangeable idler gear or something that would allow the motor to spin at maximum torque whilst driving the bike at about 6 mph. That should be able to climb a tree. Once over the steep bit, select the normal gearing. Only two ratios would be required to meet all needs up to 15.5 mph.
 

NRG

Esteemed Pedelecer
Oct 6, 2009
2,592
10
A 200w hub motor is not a lot of fun when you come to any sort of hill, but a 200w crank drive will get you up without pedalling if you have low enough gearing. A 350w rated geared hub-motor with the right controller will get also get you up any hill without pedalling, and it puts no strain on the gears. As you go higher still in power, the strain on normal bike gears would be too much for a crank drive. Instead a direct drive hub motor, which has very little to break or wear out, would be a logical choice. Both systems could use either a torque sensor, a pedal motion sensor or a throttle, so that isn't an issue. So, which one has the advantage depends on how much power assist you have. Power is gradually increasing - even within the current legal limit - so the difference between them has become less and the simplicity and lower cost of a hub-drive gives added advantage. If the proposed increase in power goes ahead, I think that crank drives will start to fade out.
I think there's a lot of truth in that, bike transmissions won't stand much more power without substantial upgrading, but that would bring unacceptable weight gains. However, I would like to see a cassette-like arrangement for derailleur sprocket clusters with the larger spindle rear hub motors, rather than be stuck with freewheels. I wouldn't like the hub motor future to be predominantly front wheel, especially with higher powers.
Yes, good points, however, direct drive motors are generally heavier for the same power output and are unforgiving if used unpowered, the new high power changes also carry a rather low weight limit as well at 25Kg which may restrict choice. One further advantage of hub drive is the use of a normal bike frame, whilst there are crank drive conversion available for standard frames they are scrap-heap-challenge looking so we don't see that many and the commercial integrated units require a bespoke frame to accommodate them increasing cost. Hub would seem the way forward....
 

jhruk

Esteemed Pedelecer
May 13, 2009
318
68
Yes, that might do the trick.

I was thinking, that as the hub drives have a planetary gear set up, an interchangeable idler gear or something that would allow the motor to spin at maximum torque whilst driving the bike at about 6 mph. That should be able to climb a tree. Once over the steep bit, select the normal gearing. Only two ratios would be required to meet all needs up to 15.5 mph.
It would appear that they have been working on a two speed hub drive over in Canada. Intriguingly it switches between direct drive and geared drive by changing the direction of rotation. I don’t know whether this is old news, or if anybody here knows more about it, but I saw it on this seminar video on hub motors. The video is rather long at 1:26 and it features around 1:15 - they seem to have got as far as building a large scale working prototype. Looks like water ingress may be a bigger problem over there than reported here as well.
 

flecc

Member
Oct 25, 2006
50,676
28,509
In an ideal world, perhaps some sort of hub drive gearbox could be installed, so to allow higher motor speeds to climb those pesky steep hills. A Da-Vinci set up maybe. I'm waiting for Flecc to invent a variomatic system, all inside the hub motor. Perhaps you could pop out to the shed and build one?
SRAM have announced their automatic shifting two-speed hub-motor which we await with interest LINK

I wonder if it would be possible to put to separate sets of windings in one motor casing. A Slow, high torque set for hills and a fast, low torque set for the flat. A micro processor could then decide which one to use at the appropriate moment
Some of these have already existed in tapped windings form, Team Hybrid were selling a direct drive one like this not long ago. They can be rather current greedy though.
 

hech

Esteemed Pedelecer
Oct 29, 2011
350
27
argyll
The hill outside my cave is very steep indeed but my crank driven iron horse can do it practically unassisted (by me) running at 36v and a nominally, continuous etc 250 watts (but actually around 500 watts or more.) I wonder if anyone else has a hub driven bike running at the same 250 watt street legal rating which could do the same - I suspect not though. However on the flat plains of the wild west this crank drive (er) wont trundle at more than 14 or 15mph throttle only while hub motors cruise on well past that. I presume therefore that the hubbies are a fair bit more efficient at speed than cranks. Up the legal limit to even 500 watts and I dont doubt that hubs will come into their own.
 

Wisper Bikes

Trade Member
Apr 11, 2007
5,991
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Sevenoaks Kent
I think there's a lot of truth in that, bike transmissions won't stand much more power without substantial upgrading, but that would bring unacceptable weight gains. However, I would like to see a cassette-like arrangement for derailleur sprocket clusters with the larger spindle rear hub motors, rather than be stuck with freewheels. I wouldn't like the hub motor future to be predominantly front wheel, especially with higher powers.
I agree Flecc, we have been working with Dapu on precisely what you describe, there was a second reason, which is to enable us to use a decent 11 tooth sprocket for our highest gear aposed to the 13 tooth we currently use.

Modern 250W rated electric bike motors can reach well over 600W for short bursts when hill climbing and the best place for such power is in my opinion as well is in the rear wheel.

Best regards

David
 

Wisper Bikes

Trade Member
Apr 11, 2007
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Sevenoaks Kent
I wonder if it would be possible to put to separate sets of windings in one motor casing. A Slow, high torque set for hills and a fast, low torque set for the flat. A micro processor could then decide which one to use at the appropriate moment
Hi Mike, the same can be achieved by switching from star to delta and back on hub motors in the way some electric machinery has a start up and high speed mode. Again this is something we are exploring for the future.

Regards

David