Failed on my first big hill

[trex]

there are cases where I would recommend a CD rather than a big hub. Gooner on the other thread has a heart condition. A CD will let him limp home whereas a hub may be too weak.

 

[flecc]

ask Bosch , Yamaha, Impulse...they developed their CD units for a reason. To give motors a massive range of ratios and rider a massive choice.

The worst thing posssible is to use a massive range of gears to cover a 10mph speed range with an electric motor. Two is the maximum needed.
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[Artstu]

there are cases where I would recommend a CD rather than a big hub. Gooner on the other thread has a heart condition. A CD will let him limp home whereas a hub may be too weak.

I have to say that's the first time I've seen a CD recommended over a hub motor for someone who is either ill or weak. Up until now it has always been said the hub motor is superior.

 

[(NoLongerRegistered#15675)]

The worst thing posssible is to use a massive range of gears to cover a 10mph speed range with an electric motor. Two is the maximum needed.
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Where,s your evidence for that Flecc??

On the torque of motors issue. My system claims 80nm at crank...the rider then decides what he,s doing with it...
Even if figure is 20% exaggerated its a lot of torque..

 

[Geebee]

The BPM motor for example stores twice as much power as the motor in the Bosch but if the Bosch rotates twice as fast, both produce the same output.

Its actually worse than that if you are talking Bafang CD is 15.1 to 1 and a Bpm2 is 5 to 1 assuming the data I found was correct.

 

[trex]

I have to say that's the first time I've seen a CD recommended over a hub motor for someone who is either ill or weak. Up until now it has always been said the hub motor is superior.

yes, I have seen a few cases when the person was a regular cyclist, so not seeking to avoid gear change.
somebody who is ill or weak could use a throttle. But besides a throttle, CD lets you trade speed for torque when needed whereas you don't have that choice with hubs. Ask Hatti to let you do a review of the Krieger andd see if it would suit someone with a heart op.

 

[Geebee]

I have to say that's the first time I've seen a CD recommended over a hub motor for someone who is either ill or weak. Up until now it has always been said the hub motor is superior.

If you have hills and can't provide human assist a CD with correct gearing is better than a hub, gearing is critical though.
I unfortunately found my self in that exact position and have a hill that averages 12.5% grade with 20% ramps to get home after each ride plus plenty of similar ones around.
I tend to just spin the pedals on zero effort once off the line and shift as needed, it helps you feel like you are riding a bike still and gives a very light work out.
I tried an Ezee hub on a similar but shorter hill and it could not get up it without assistance.

 

[Artstu]

Ask Hatti to let you do a review of the Krieger and see if it would suit someone with a heart op.

but I've not had a heart op. I do have an autoimmune disease though which limits my available muscle power, even though my actual on bike fitness is higher than an average healthy person.

 

[(NoLongerRegistered#15675)]

I,ve had a knee replaced in right leg. Struggle pressing hard enough for ordinary cycling, its not an issue on CD...I,m ok with higher cadence but surgeon insists..
no standing on pedals.
no great pressure on pedals
Keep cadence between 40 and 80 on lightish loads..
Yam CD absolutely perfect.

 

[trex]

but I've not had a heart op. I do have an autoimmune disease though which limits my available muscle power, even though my actual on bike fitness is higher than an average healthy person.

sorry, I meant to say a CD would suit Gooner, who just had a heart op.

 

[Geebee]

The worst thing posssible is to use a massive range of gears to cover a 10mph speed range with an electric motor. Two is the maximum needed.
.

Only thing is with a CD you sacrifice efficiency, the trick is the moment the cadence/motor rpm drop shift down to keep it spinning fast, there is a measurable increase in efficiency by doing so.

 

[flecc]

Where,s your evidence for that Flecc??

The power and torque graphs for the hub motors I'm speaking of. They have optimums easily flat enough to cover the 5 to 15 mph range with two gears. Swapping a single gear change within that range for more changes just loses drive time. No changes at all keeps the power engaged.

Only thing is with a CD you sacrifice efficiency, the trick is the moment the cadence/motor rpm drop shift down to keep it spinning fast, there is a measurable increase in efficiency by doing so.

I really don't see the point of sacrificing pleasure for a gnats of efficiency. I ride for pleasure and changed from both types to only powerful hub motors simply because they are more pleasant and convenient in use. I can choose how to ride without the typical CD torque sensor dictating what I must deliver to get the power needed and don't care whether I'm using a couple of Watt/hours per mile more when I want to.

There comes a point in economy where fanaticism takes over from commonsense, and that point can easily be reached in e-biking.

As for the odd very steep hill, I'm happy to put in a bit more energy to help a powerful hub motor on the climb. I'm paid back in two ways, a much faster climb and being able to put in far less effort at all other times if I want to, without a torque sensor insisting on a minimum. Indeed on my current legal Ezee e-bike, I don't even need to pedal at all on any run including up to 14% hills.

Total flexibility = maximum pleasure.
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[(NoLongerRegistered#15675)]

Only thing is with a CD you sacrifice efficiency, the trick is the moment the cadence/motor rpm drop shift down to keep it spinning fast, there is a measurable increase in efficiency by doing so.

Yep I think it relates to keeping motor spinning around 2000rpm...right in its peak efficiency...
Other thing is when going very slowly in lower gears pedal pressure is low which corresponds to low current supplied, but with low gearing of motor its enough to help...

 

[Geebee]

There comes a point in economy where fanaticism takes over from commonsense, and that point can easily be reached in e-biking.

20% increase in range and probably motor life as it never gets hot is worth a gear change as you would on a normal bike IMO.

As for the odd very steep hill, I'm happy to put in a bit more energy to help a powerful hub motor on the climb.

Not always an option.

 

[Geebee]

Yep I think it relates to keeping motor spinning around 2000rpm...right in its peak efficiency...
Other thing is when going very slowly in lower gears pedal pressure is low which corresponds to low current supplied, but with low gearing of motor its enough to help...

My CD is not a torque sensor plus my gearing is what most would consider insanely low so high rpm are still available on very steep hills, the motor never gets hot even though its doing 99% of the work.

 

[flecc]

20% increase in range and probably motor life as it never gets hot is worth a gear change as you would on a normal bike IMO.

First the range increase is of no importance since I can and sometimes do have a second battery with me. I've even ridden for hours over very long distances with three batteries, one in each pannier.

And I've never had an issue with motor overheating. During it's life in 2008 I carried out a long term six month battery test for a manufacturer, treating it brutally by avoiding pedalling as much as possible and slogging it up very steep hills at low speeds with very low efficiency. Link to story.

I've also posted long ago about a two stage 8 mile climb I did without pedalling, again slogging without pedalling at very low efficiency. At the start with motor already warmed up from the run from home I took a thermocouple reading of the hub shell temperature. The moment I'd completed that slogging 8mph climb I checked the temperature again. It was almost identical, reading fractionally lower.

My present hub motor is running fine at almost exactly 10 years old while during this ten year to date life, I've seen very many CD units fail in various ways.

All this proves nothing other than motor overheating affecting reliability is nothing but theory, in practice it's not an issue with decent motors.
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[shemozzle999]

All of the above on 20" wheels

 

[flecc]

All of the above on 20" wheels

No, only the long term battery test, since that bike was most suited to avoiding pedalling. I wanted to make sure the motor did almost everything to really punish the battery.

The temperature check long climb was on my 700c wheel bike, using the identical motor/controller/battery combination. Both were Ezee bikes.
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[Deleted member 4366]

Everybody should stop focusing on the differences between crank-drive and hub-motor. Ultimately it doesn't matter one iota. Instead, it's the bike you should look at. Can it do what you want? When somebody requests guidance on which bike to get, you should focus on what the bike can do considering rider input and bike output, not which type of motor it has.

 

[trex]

what do you mean by what the bike can do? are frame shape, suspension, brakes, gears, throttle, wheel size, weight, accessories more important than the motor and battery?