Drive Through Gears on E-bikes

[ElephantsGerald]

I've just notices this article on the main pedelecs web site: Technical Article: Drive Through Gears on E-bikes which was written by the illustrious flecc in August 2007.

The article draws the following conclusions:

So will a gearless hub motor e-bike do your job? In nearly all cases yes, but for the very steepest hills of around 1 in 5 (20%) or steeper.

Alternatively they could choose one of the very few drive through gear bikes on the market which will climb almost anything, but only with good rider input and rather slowly.

My (very brief) summary of the article is as follows:
Hub motor - good. Drive through gears - not so good (especially if you're not very fit).

At the moment there seems to be loads of excitement on the forum about the Kalkhoff bikes with their drive through gears.

So my question is, have I misunderstood the article, or has something radically changed in the world of drive through gears since last summer?

P.S. Please point me in the direction of the relevant posts if this question has already been answered. Thanks.

 

[HarryB]

One quick point. It was all written before the Agattu was released and was based on the Lafree, which had just been discontinued. The Lafree only had a 1:1 power system and you had to put in a similar amount of work to match the motor, thus slow and quite hard work for the unfit. The latest drive through the gear pedelecs have a high power mode, some providing as much as 150% assistance. Flecc will be able to elaborate more as it was his article.

PS I think we could have an updated version the comparison between hub and crank drive systems as it would help those choosing their first ebike. For me one of the most important factors is that a crank drive ebike is more like a normal bicycle to ride. With a hub motor you always feel you are pedalling against the drag of the hub.

 

[john]

For me one of the most important factors is that a crank drive ebike is more like a normal bicycle to ride. With a hub motor you always feel you are pedalling against the drag of the hub.

Isn't that more to do with the existence and efficency of a freewheel mechanism than to do with the location of the motor?

 

[HarryB]

Most hub motors have a 'freewheel' but it disconnects at the point between the motor and the gears. So the gears still turn and cause drag. Even with the nano motor, which has the lowest drag of any hub motor, it feels like you are pedalling against 'porridge'. I have ridden three different types of hub motored bicycles and they all felt horrible to ride unassisted. Today I am expecting the arrival of my Agattu so I will find out first had if the theory holds true.

 

[flecc]

The Agattu made no difference since the Panasonic system has been around for a long time. The principles described remain, that drive through the gears is fundamentally less efficient for the reasons described.

Panasonic's unit is uniquely free running through being made with a precision not normally appearing in bikes, overcoming to a fair extent the objection. Bikes with it are far better bikes to cycle without power and then the more efficient, but that was not the subject of the article which was about electric driving efficiency where drive through chain and gears loses out.

The other factor relevant to the Panasonic unit is the clever management of the rider as well as the motor, getting the rider to their proportion of the work. The fact that hub motors currently don't do that leads to them contributing far higher work proportions than necessary, so a hub motor system with an equal management system would show the intrinsic efficiency much better.

The point of the article was to offset the mistaken and widely held view that drive through gears was intrinsically more efficient, where in fact as shown, the losses are greater in practical use on e-bikes. The fact that the quality of the Panasonic system makes those bikes so pleasant to use doesn't change that.

For a long time I owned bikes with both systems in parallel, and at normal cruising speeds the greater efficiency of the hub-motor bikes is obvious, but the Panasonic motored Twist was the far nicer bicycle overall, even though I did more work on a journey riding that.
.

 

[johnl]

Bionx Supplies Power Proportional to User Input

The other factor relevant to the Panasonic unit is the clever management of the rider as well as the motor, getting the rider to their proportion of the work. The fact that hub motors currently don't do that leads to them contributing far higher work proportions than necessary, so a hub motor system with an equal management system would show the intrinsic efficiency much better.

The Bionx system also senses the rider effort and contributes power proportionally. The less rider effort, the less current is sent to the hub motor. I can set my controller to four different assist levels. At the lowest level, the power assist is like having a tailwind. I can get a pretty good workout when going up hills with the unit set at its lowest level.

 

[john]

The Bionx system also senses the rider effort and contributes power proportionally. The less rider effort, the less current is sent to the hub motor. I can set my controller to four different assist levels. At the lowest level, the power assist is like having a tailwind. I can get a pretty good workout when going up hills with the unit set at its lowest level.

That sounds like a more sensible way around to do it. Actually, if the Panasonic system worked that way it should be more efficient as the motor would be providing more power when it is able to work more efficiently i.e. at higher rpm.

 

[flecc]

That sounds like a more sensible way around to do it. Actually, if the Panasonic system worked that way it should be more efficient as the motor would be providing more power when it is able to work more efficiently i.e. at higher rpm.

In terms of choice of power levels, the Panasonic does have choices in the same way, three of them but without the BionX regenerative function.

The other point is a misunderstanding of how the Panasonic unit works. It's motor is designed to provide pulsed power and constant revolutions don't come into the picture. On each pedal stroke the motor surges in power that's matched to the rider input throughout the arc of the crank, always proportional according to the prescribed ratios.

That's why it's more of a bicycle than any other design, since that is exactly what it is, the only difference being that the riders muscles are bionically assisted. Nothing about it says "motor vehicle" in the way that all other designs do, including the BionX.

It's designed to emulate utility bike use, but no doubt one could be designed to emulate sports bike characteristics, though Japanese legal restrictions are too restrictive for Panasonic to be interested in doing that.
.

 

[ElephantsGerald]

Sly as a fox

The other point is a misunderstanding of how the Panasonic unit works. It's motor is designed to provide pulsed power and constant revolutions don't come into the picture. On each pedal stroke the motor surges in power that's matched to the rider input throughout the arc of the crank, always proportional according to the prescribed ratios.
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This all sounds fiendishly cunning! And remarkable that the Panasonic unit seems to have such a good record of reliability; surprising not to see more bikes using this system.

I'd almost be tempted if these bikes featured a way to drive themselves when you'd been defeated by a hill and had to resort to walking.

Or perhaps the panasonic system is so cunning that you never will be defeated by a hill

 

[flecc]

This all sounds fiendishly cunning! And remarkable that the Panasonic unit seems to have such a good record of reliability; surprising not to see more bikes using this system.

I'd almost be tempted if these bikes featured a way to drive themselves when you'd been defeated by a hill and had to resort to walking.

Or perhaps the panasonic system is so cunning that you never will be defeated by a hill

Although they can climb almost anything, BikeTech do one of their Panasonic powered bikes that has the walk-alongside throttle arrangement for up to 4 mph.

All you need now is a generous bank manager,

and the UK agent:

VitaElectric

The top three illustrated are BikeTech models.
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[ElephantsGerald]

Although they can climb almost anything, BikeTech do one of their Panasonic powered bikes that has the walk-alongside throttle arrangement for up to 4 mph.

All you need now is a generous bank manager,

and the UK agent:

VitaElectric

The top three illustrated are BikeTech models.
.

Interesting! Although hard to make much sense of the VitaElectric web site as it currently stands...

I would ask how it is that you know all these things flecc, but I'm sure that would take too long. I'm very glad you do though .

It'd be nice is someone (presumably with loads of time on their hands!!) could compile (and keep up to date!!) a document comparing popular bikes feature for feature on a comprehensive basis. Probably wishful thinking though.

I know A to B Magazine have done something along these lines, but their buyers guide only compares a very few features (and seems a bit out of date).

 

[flecc]

Interesting! Although hard to make much sense of the VitaElectric web site as it currently stands...

It's been like that for years, a bit like most British construction sites.

He's obviously internet averse like David at A to B magazine, and it's best to deal with Vita by phone.

I would ask how it is that you know all these things flecc, but I'm sure that would take too long. I'm very glad you do though .

I started in the cycle and motor cycle trade at 14 years old, 58 years ago, and although I moved on through many other branches of engineering my interest has remained. That's coupled with a memory that retains all this sort of detail, backed by a database containing many hundreds of information entries.

It'd be nice is someone (presumably with loads of time on their hands!!) could compile (and keep up to date!!) a document comparing popular bikes feature for feature on a comprehensive basis. Probably wishful thinking though.

I know A to B Magazine have done something along these lines, but their buyers guide only compares a very features (and seems a bit out of date).

I have thought of it and could do it. Being retired though, I'm reluctant to take on all the work of constant never ending updating, just maintaining my two e-bike websites being quite enough when coupled with the posting in here and answering a myriad of PMs and e-mails.
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[Larkspur]

By my calculation, with Hi powered mode switched on, the rider of a bike with a Panasonic motor only needs to put in 217 watts of effort to obtain a total input to the drive of 500w, the maximum assisted power. This is elite athlete territory: Lance Armstrong was reckoned to be capable of keeping up this level of effort for 20 minutes at a time, a feat which no other Tour rider was capable of matching.

In other words, if you and your Panasonic powered bike weigh the same as Lance Armstrong and his Trek Madone (admittedly unlikely) you will be able to keep pace with him up mountains, by expending a moderate effort that most normally fit people could keep up for considerably longer than 20 minutes. A fit person could do the same in normal mode.

I realise that the above example is kind of ludicrous, and does oversimplify the whole thing a bit , i.e. you'd have to increase your effort if you and Lance were travelling faster than 9.4 mph (the point at which the power assist begins to phase down) - but I think it makes the basic point about the meaning of the 1:1, or 1:1.3 help you get from the Panasonic motor and the difference it can make in practical terms, to an average, not particularly fit cyclist.

 

[flecc]

Yes Chris, the calculation is correct, and only the gearing and bike weight stops it being possible. The limit on these calculations is that of the motor's net power. The same motor in the old unit was specified as 390 watts peak for the US market when on 24 volts nominal, so on the 26 volts nominal that's about 420 watts.

However, those are probably gross ratings judging by the tiny motor, so the limits are either 350 watts from the motor or the corresponding 270 watts from the rider. A fully fit rider of about 25 to 45 years should be able to input that for 10 minutes continuous, but I fear most of us have to set our sights a bit lower.

We can mostly do a lot more briefly though, and last year, after practice to get the right gear choice, I managed to climb a quite short 1 in 7 at 13 mph on the Agattu. That needed almost 800 watts continuous, beyond the Panasonic motor's limit, hence my having to provide the rest, which was between 360 and 450 watts, depending on what the net power of the motor is. OK for a few seconds even at my age, but I couldn't keep that level up for even a minute. In similar circumstances Lance Armstrong was apparently capable of bursts of over 1000 watts, and I've no doubt the top sprinters can exceed that by even more.
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