250 watt is it a myth?

[Andy88]

Yes good comparison probably apple iOS to android might be even closer with the control apple exerts on its products and customers

I use an Android phone [emoji6]

 

[Benjahmin]

For me a large part of cycling is simplicity of maintenance/repair. This is why I opted for a kit with a geared hub motor and deraileur gears. A while ago, when my motor started to make a noise, it was just a matter of dropping out the front hub, and stripping the casing to find a shot bearing race, quickly supplied by the original supplier. No returning the bike to the manufacturer, at what expense, and waiting for...........well who knows? With these manufacturer only servicable motors, they could tell you what they like and you have to swallow it down.

I also had hub gears as a lad, I guess they've moved on some but the internals are a mystery to me. A Deraileur is in you face obvious in operation and adjustment and, if anything does go wrong (a rarity I find) that's also obvious. Deraileur changers have also moved on from the old friction change. The index changers on my Carrera are slick and accurate (front and back) requiring only the occasional tweak.

I live out in the sticks, having a bike I can understand, maintain and repair saves me 1 1/2 hour round trips to my LBS, if they would touch my bike. I also believe that lesser complexity means less fault liability, surely cycling was meant to be a reliable simple pleasure? (With a salute to all those who commute - I don't have to).

Anyway, to the OP question. A myth, maybe. Misunderstood, certainly. Meaningless, as an absolute, definately.
In a similar way, as far as I know, car headlamps are legally limited to 36W. Now made a nonsense of by LED lamps. Try putting a 36W LED with a focused beam in there and youll burn a hole in someones retina. OK a slight exageration but it demonstrates that wattage is a crude measure of ability.

I try to adhere to KISS ?? Keep It Simple Stupid !

 

[Andy88]

For me a large part of cycling is simplicity of maintenance/repair. This is why I opted for a kit with a geared hub motor and deraileur gears. A while ago, when my motor started to make a noise, it was just a matter of dropping out the front hub, and stripping the casing to find a shot bearing race, quickly supplied by the original supplier. No returning the bike to the manufacturer, at what expense, and waiting for...........well who knows? With these manufacturer only servicable motors, they could tell you what they like and you have to swallow it down.

I also had hub gears as a lad, I guess they've moved on some but the internals are a mystery to me. A Deraileur is in you face obvious in operation and adjustment and, if anything does go wrong (a rarity I find) that's also obvious. Deraileur changers have also moved on from the old friction change. The index changers on my Carrera are slick and accurate (front and back) requiring only the occasional tweak.

I live out in the sticks, having a bike I can understand, maintain and repair saves me 1 1/2 hour round trips to my LBS, if they would touch my bike. I also believe that lesser complexity means less fault liability, surely cycling was meant to be a reliable simple pleasure? (With a salute to all those who commute - I don't have to).

Anyway, to the OP question. A myth, maybe. Misunderstood, certainly. Meaningless, as an absolute, definately.
In a similar way, as far as I know, car headlamps are legally limited to 36W. Now made a nonsense of by LED lamps. Try putting a 36W LED with a focused beam in there and youll burn a hole in someones retina. OK a slight exageration but it demonstrates that wattage is a crude measure of ability.

I try to adhere to KISS ?? Keep It Simple Stupid !

I agree with you 100% especially on maintenance and repair @ £30 an hour the more we can do ourselves the better.

I originally leaned towards a front wheel drive hub so if it fails worse case throw the wheel away and buy a new one.

I may have to reconsider derailleur but am a little scared of them having always had a hub as a kid.

My final decision will be swayed on hub, crank, derailleur, IGH depending on where I decide to live in the UK at present im overseas pondering a few areas in the North of England or Scotland and dealer availability.

I also agree on the wattage comment.

What brand is your hub?

 

[Deleted member 4366]

According to a technical data sheet, on another website the Bosch active line unit specified at 250 w has a max rotational speed of 100 rpm and a max torque of 50 nm this would in theory give it a power of 523w .

That's not right. Maximum torque is at zero RPM. The slower you pedal the more torque you get. At 100 rpm, the motor has maxed out so torque (and power) at that speed is zero. Peak power will come at about 75 rpm but we don't know what the torque is there; however, you may still be sort of right. I reckon that the 50 NM is just a made up number. It's probably worked backwards from the power.

 

[Artstu]

At 100 rpm, the motor has maxed out so torque (and power) at that speed is zero. Peak power will come at about 75 rpm

Correct, mine gives more assistance at lower cadences, when I'm really going for it I have to change to a higher gear for more assistance with a cadence that is below what is ideal for me.

 

[Andy88]

Correct, mine gives more assistance at lower cadences, when I'm really going for it I have to change to a higher gear for more assistance with a cadence that is below what is ideal for me.

So for an old bugger like me where going for it would result in a possible heart attack I need to steer clear of these torque models?

 

[Artstu]

So for an old bugger like me where going for it would result in a possible heart attack I need to steer clear of these torque models?

I honestly don't know, only you will really know, and that preference you initially make could change over time.

My bike also goes very nicely with a low input from me when my illness stops me walking anywhere.

 

[Danidl]

That's not right. Maximum torque is at zero RPM. The slower you pedal the more torque you get. At 100 rpm, the motor has maxed out so torque (and power) at that speed is zero. Peak power will come at about 75 rpm but we don't know what the torque is there; however, you may still be sort of right. I reckon that the 50 NM is just a made up number. It's probably worked backwards from the power.

H

Without knowing the construction of the motor we are both speculating,. Certainly a series wound motor would have max torque at zero rpm, a three phase induction motor will have max torque at about 5% below synchronous speed.
On the other hand I would expect that the max torque measurement would have come from dynamometer readings .
My speculation is that the computer within the motor controller will modulate the current following a lookup table to ensure that the motor remains within its design envelope. The Bosch. motor costs so much that they can easily afford the extra costs of computer monitoring.

 

[anotherkiwi]

Answering the OP's question, no it is not a myth, from EN15194:

4.2.7
Maximum power measurement
4.2.7.1
Measurement at the engine shaft
The maximum continuous rated power shall be measured according to EN 60034-1 when the motor reaches its thermal equilibrium as specified by the manufacturer.
NOTE
Thermal equilibrium: temperatures of motor parts do not vary more than 2K per hour. In circumstance where the power is measured directly at the shaft of the electronic motor, the result of the measurement shall be decreased by 1,10 to consider the measurement uncertainty and then by 1,05 to include for example the transmission losses, unless the real values of these losses are determined.
4.2.7.2
Alternative method
When the power is measured at the wheel, the result of the measurement is the reading value.

There is nothing in EN15194 which says that such a motor cannot provide much higher power for shorter periods of time, that would be peak power and not maximum rated continuous power. My GSM peak power is 630.38 W at the shaft, previous hub motor about 570 W.

 

[oldtom]

My bike also goes very nicely with a low input from me when my illness stops me walking anywhere.

Ditto that. I need to pedal but not in an exhausting way. Very little effort allows me to just pootle along if I have been working hard and just want to take it easy for a bit. That's thanks to the Xion motor and its excellent controller.

Tom

 

[Andy88]

Ditto that. I need to pedal but not in an exhausting way. Very little effort allows me to just pootle along if I have been working hard and just want to take it easy for a bit. That's thanks to the Xion motor and its excellent controller.

Tom

Refreshing, input from throttle or pedals? Bike and motor model and brands?

 

[Andy88]

Answering the OP's question, no it is not a myth, from EN15194:

4.2.7
Maximum power measurement
4.2.7.1
Measurement at the engine shaft
The maximum continuous rated power shall be measured according to EN 60034-1 when the motor reaches its thermal equilibrium as specified by the manufacturer.
NOTE
Thermal equilibrium: temperatures of motor parts do not vary more than 2K per hour. In circumstance where the power is measured directly at the shaft of the electronic motor, the result of the measurement shall be decreased by 1,10 to consider the measurement uncertainty and then by 1,05 to include for example the transmission losses, unless the real values of these losses are determined.
4.2.7.2
Alternative method
When the power is measured at the wheel, the result of the measurement is the reading value.

There is nothing in EN15194 which says that such a motor cannot provide much higher power for shorter periods of time, that would be peak power and not maximum rated continuous power. My GSM peak power is 630.38 W at the shaft, previous hub motor about 570 W.

My heading is tongue in cheek apparently there are other variables than just the wattage that attribute to quality of the ride.

 

[Nealh]

TS or BBS drive bikes require good rider input to get the best from them esp on gradients. A cadence/pas hub drive often only need gentle pedal rotation to achieve good speed. For a lazy town ride my Big Bear kit fitted to my Norco hybrid only requires minimal pedal movement to et up to 15.5 mph, more effort has me up to 21 mph and hills are quite a doddle.

 

[Andy88]

TS or BBS drive bikes require good rider input to get the best from them esp on gradients. A cadence/pas hub drive often only need gentle pedal rotation to achieve good speed. For a lazy town ride my Big Bear kit fitted to my Norco hybrid only requires minimal pedal movement to et up to 15.5 mph, more effort has me up to 21 mph and hills are quite a doddle.

Thanks for that. Not sure what TS and BBS is please?

 

[Nealh]

Torque sensor & Bafang BBS01. Not ridden a 02 but output is more powerful and faster.
Though when you are back in the UK there will ne no substitute for actually test riding some ebikes. Once you know where are settled an ask on here may get you a test ride even on a kit home build bike.

 

[Andy88]

Torque sensor & Bafang BBS01. Not ridden a 02 but output is more powerful and faster.
Though when you are back in the UK there will ne no substitute for actually test riding some ebikes. Once you know where are settled an ask on here may get you a test ride even on a kit home build bike.

Thanks Neal

 

[Andy88]

Thanks Neal

Can I ask where you bought your big bear kit?

 

[Rohloffboy]

Hi Andy88.
That Bafang Max Drive bike image you posted from Brighton Ebikes, I could not find it on there website, although I may have gone to the wrong website.

I do like the fact that it is a step-through and has a IGH, do you know the brand of the bike, the only similiar model I can find is the Volton, using a derailleur gear, and that was on a U.S.A. website.

 

[Andy88]

Hi Andy88.
That Bafang Max Drive bike image you posted from Brighton Ebikes, I could not find it on there website, although I may have gone to the wrong website.

I do like the fact that it is a step-through and has a IGH, do you know the brand of the bike, the only similiar model I can find is the Volton, using a derailleur gear, and that was on a U.S.A. website.

They sent it to me separately I'll enquire and post here.

 

[Andy88]

They sent it to me separately I'll enquire and post here.

Ive emailed await reply