Thoughts about Torque sensors

[Kudoscycles]

Having spoken to many at Presteigne I have tried to understand the logic of Torque Sensors-correct me if I am wrong but with a torque sensor crank- the sensor detects the amount of torque that the rider is exerting onto the pedals, if that pressure is high the controller decides the rider needs assistance so the motor also provides maximum power to assist the rider. However,if the rider effort is low then the motor will provide less power assuming the rider requires less assistance.
For a fully fit rider I can see that this system will work fine but for an unfit rider,especially a rider who cannot exert a lot of torque into the pedals surely this is the opposite of what he needs. If the unfit rider is struggling up a hill and cannot exert much pedal pressure then the motor decides he needs minimal assistance,just at the time when he needs maximum assistance.
It is my reasoning that ideally it should be up to the choice of the rider by some form of manual overide (throttle or boost button etc) as to how much power assistance is required to assist the hill climb not by the control of a torque sensor.
Dave Elderfield
Kudos Cycles

 

[morphix]

Hi Dave, I absolutely agree with your observations sounds quite logical to me. Most kits seem to offer the other kind of magnetic sensor I've noticed, that works on speed rather than torque. This makes a lot more sense and works perfectly for unfit people. My own kit has 7 levels of power assist linked to the sensor, once you get up to 15mph it cuts out the motor, or as soon as you stop pedalling. If I put it in the highest setting just a half rotation on the pedal and wooosh I'm away!

 

[flecc]

There's long been an argument about the philosophy on e-bike torque sensors, but the position is not always as simple as it may seem since it depends on the system's sophistication.

Yes, a strong rider can produce a correspondingly stronger motor assistance on such as the Panasonic system. However, since that combination will often be more than is necessary for the conditions, the cadence rises with the resulting rising speed which in turn reduces the motor output due to the power phase down slope. So the system self-compensates to prevent excessive battery energy wastage, whilst making full use of the extra rider ability.

That's brilliant design.

The cleverness of the system also has the advantage of remarkably consistent ranges for all abilities of rider, something conventional e-bike designs can't emulate.

The problem arises when a crude torque sensor is simply added to a conventional system, and then I agree they work in a rather irrational way and also produce large variations in owner's experiences, in both range and performance.

Panasonic power delivery explanation

 

[Kudoscycles]

The reason for my posting was I tried one of the more expensive bikes at Presteigne up the test hill,the bike had a torque sensor,the bike was beautifully engineered,a work of art in fact. But if I decided to have a rest half way up the hill the power reduced to the point where I was commited to pedal harder to get the power back. I must be honest and say that to achieve steep hill starts I found the bikes with speed sensors and throttle overide to be the easiest to pull away-push the bike forward to gain momentum,use the throttle to maintain momentum at same time turning pedals and then ease back on the throttle to achieve optimum balance between the throttle and rider input.
I am currently specifying a hub drive bike especially to climb steep hills,hence my interest.

 

[Deleted member 4366]

I think it's all unnecessary expence and sophistication. I've found that my favourite system is the one with a pedal motion sensor that feeds in maximum power as soon as you start pedalling with a motor that's wound for a max speed of 15mph. Then it works much more logically, feeding in more power as you slow down and gradually tailing off to zero as you reach 15mph. Then you get good range when pedalling on the flat and maximum assist up the hills

 

[Kudoscycles]

d8veh...I totally agree with you,exactly my thinking...there seems to be a movement for complex and sophisticated systems that sounded hi-tech on paper,to justify hi-tech prices but in reality they didn't seem to go up hills any better than the simple systems.
Dave Elderfield

 

[flecc]

I'm often caused to wonder what people think are steep hills. I do know that I can get a Panasonic powered bike up any of the very steepest North Downs hills, something I cannot do with the most powerful hub motor bikes from eZee for example.

Clearly the sophisticated crank drive system climbs really steep hills better for a given rider's limitations.

Of course on more moderate hills the powerful hub motor bike can outclass the Panasonic one for speed up them, but so it should with it's much larger battery for a given range.

 

[NRG]

I think it's all unnecessary expence and sophistication. I've found that my favourite system is the one with a pedal motion sensor that feeds in maximum power as soon as you start pedalling with a motor that's wound for a max speed of 15mph. Then it works much more logically, feeding in more power as you slow down and gradually tailing off to zero as you reach 15mph. Then you get good range when pedalling on the flat and maximum assist up the hills

d8veh, that's how the standard Panasonic system works! You get maximum power as you start to pedal with power up to 15.5mph tailing off gradually in stages as you approach top speed. You get maximum assist up hills just when you need it as you tire and your cadence slows, if you need more then you can dial in more power (note power not speed) by selecting a higher assist level...

 

[Kudoscycles]

flecc and NRG....to my mind in both those postings you have explained the pros and cons of hub drive v crank drive. I suppose it's all about the steepness of the hills. From the limited experience I have had it appears to me that anything steeper than 10% is crank drive,below 10% and the hub drive gets progressively better,below 5% hub drive. If I am correct then Holland should all be hub drive,yet Kalkhoff sells well there-which would suggest that marketing and perception overcomes science!!!!!

 

[flecc]

Kalkhoff does do reasonably well in Holland, as does Flyer, but the hub motor bikes from Sparta, Koga and Batavus et al outsell them so the Dutch commonsense still fortunately rules.

As you say, the crank/hub thing should be a hill steepness choice, and 10% is a good split point to cope with all levels of rider ability. Personally I like both systems on a horses-for-courses basis and have owned both.

Currently it's a powerful hub motor which does place just a few limitations on where I ride, and I'd probably be better suited with one of today's more powerful crank motor types now. My last crank drive bike was the Lafree, older less powerful Panasonic system with no high power mode. Today's Panasonic system I've found far better from trying three of the bikes with it.

 

[NRG]

I think Flecc has always said if you will only ever come across moderate hills go hub drive and I would agree. Can't explain why Kalkhoff's are such a big seller in The Netherlands but they are well made and have another plus point IMHO with the Panasonic system in that you can tootle around at any speed under 15.5mph, in any gear and in a controlled easy way with assistance. You cant do that with a typical hub motor and pedal sensor as the majority (not all I admit) try to catapult you up to the max assist speed limit as soon as the motor kicks in...