Motor Drag

[Barnsleyrob]

As a complete newbie I have been using my pedelec at power levels 1-5. I was somewhat disappointed that the first ride out gave me a range of about 8 miles so I checked for binding brakes etc. Rotating the wheel with power off confirmed some drag and with power on and using “walk” it also seemed to indicate binding.

Anyway, today I discovered power level 0 and it’s been a revelation. Out on a flat ride (total climb 385ft) I had plenty of life left and, more importantly, I found level 0 easier to pedal than level 1 or 2.

Is this normal ?

 

[vfr400]

It's an illusion. The illusion is that you think that it's your pedal power that is propelling you when the motor is on. When the motor cuts, it gives the illusion of riding through treacle because, you lose the assistance that was enabling you to maintain your speed.

 

[MontyPAS]

As a complete newbie I have been using my pedelec at power levels 1-5. I was somewhat disappointed that the first ride out gave me a range of about 8 miles so I checked for binding brakes etc. Rotating the wheel with power off confirmed some drag and with power on and using “walk” it also seemed to indicate binding.

Anyway, today I discovered power level 0 and it’s been a revelation. Out on a flat ride (total climb 385ft) I had plenty of life left and, more importantly, I found level 0 easier to pedal than level 1 or 2.

Is this normal ?

On all my kit, be they crank or hub. Level O is zero assistance.....?????????
Looks like you are powering the bike not the motor?

 

[georgehenry]

I did a leisure ride (I usually only use it to ride to work and back) yesterday and was aiming to explore an area about 10 miles from my home and do a big circle with about 3/4 off road. I used my 2015 Haibike and have found it very nice to ride with no assistance on level ground and that of course saves your battery for when you really need it. My 5 and a half year old 400Wh battery started at 100% and was still comfortably over 50% when I got home after about a 35 mile ride, though I had not made a note of my mileage after my last ride so it was hard to be sure.

The ease with which I can cycle the Haibike with Yamaha motor with no assistance is contrasted by my old circa 2011 rear hub driven Oxygen bikes that are much harder to the point where you don't really want to. I am not sure whether the rear hub motor adds drag or just that the higher gearing and heavier weight make the effect of drag seem much worse.

 

[Woosh]

As a complete newbie I have been using my pedelec at power levels 1-5. I was somewhat disappointed that the first ride out gave me a range of about 8 miles so I checked for binding brakes etc. Rotating the wheel with power off confirmed some drag and with power on and using “walk” it also seemed to indicate binding.

Anyway, today I discovered power level 0 and it’s been a revelation. Out on a flat ride (total climb 385ft) I had plenty of life left and, more importantly, I found level 0 easier to pedal than level 1 or 2.

Is this normal ?

drag varies with the kit you have.
On direct drive motors, drag is electrical (magnetic binding), on geared hub motors, mechanical through the internal clutch. On top of that, you have the effect of inertia of the heavy motor when your speed varies.
Simplest way to figure out where it comes from and how much, is to experiment a bit.
Ask a friend to help you lift the motor wheel. Spin the wheel in assist 0 and then assist 1 to see if there is more drag when the controller is switched on.
Then compare the number of revolutions on the motor wheel with the non motor wheel.

 

[Nealh]

Bafang cst offers no drag, my one rides nicely with no power. The extra weight is noticeable issue on inclines.

 

[Danidl]

It's an illusion. The illusion is that you think that it's your pedal power that is propelling you when the motor is on. When the motor cuts, it gives the illusion of riding through treacle because, you lose the assistance that was enabling you to maintain your speed.

I have had this discussion with you previously . I think there is a binding with hub motors missing from the crank drive . Now in fairness when the hub motor is inverted and spinning the wheel manually there is no great drag, but I do notice it on my ancient UM when power is off and manually cycling at low speed.
Are not the three planetary gears rotating all the time in a sludge of grease?.

 

[Woosh]

the OP compares the drag between no assist and assist 1-5.
That suggests the source of the perceived binding is electrical.

 

[vfr400]

The ease with which I can cycle the Haibike with Yamaha motor with no assistance is contrasted by my old circa 2011 rear hub driven Oxygen bikes that are much harder to the point where you don't really want to. I am not sure whether the rear hub motor adds drag or just that the higher gearing and heavier weight make the effect of drag seem much worse.

Drag from a hub-motor is shown in the vid below. See how long your Haibike's wheel spins.

Also, what you don't realise is that the Haibike's drag is in the crank, so you only get it when you pedal, not when you freewheel. You can test it by taking the chain off and spinning the pedals. A hub-motored bike has no drag in the crank.

 

[Nealh]

As vfr say's lift the geared hub wheel off the ground, a hub rear hub motor or a front one will quite happily free wheel many rotations as a normal wheel would. It matters not whether powered or not the hub wheel should freewheel if it doesn't then either brakes or rubbing is hindering rotation or maybe hub bearings or planet gears are not free enough.
My 8fun cst over 7k miles and runs very sweetly.

Some hubs have sparse greasing and less can be worse then more.

 

[Woosh]

you can calculate the drag from the video above if you know the speed reading and the weight of the wheel minus the motor core.
This is just a quick estimate so you get the idea of drag from a Bafang geared hub front motor SWX.
rotating weight: m = 1.5kgs
r = distance between the centre of gravity of the wheel minus the motor core to the centre of the hub: 26"/2 = about 165mm.
RPM when power was turned off: 200 RPM (assumed value)
moment of inertia = m x r ^2 (mr squared) = 0.041 kgm2
angular speed = 200/30 * pi() = 20.9 rad/sec
rotational kinetic energy of the wheel at the moment the power was cut: KR = 0.5 * [Moment of inertia × (Angular velocity) squared = 9 Joules
Time to lose all that energy through drag: about 70 seconds
average drag: 9 J / 70s = 0.13W
speed at mid freewheeling: about 30 rpm
The drag goes up with speed, so it's safe to assume that at your average speed of 15mph, you lose about 0.13W*200RPM/30RPM = 1W due to the motor drag.

 

[Gavin]

you can calculate the drag from the video above if you know the speed reading and the weight of the wheel minus the motor core.
This is just a quick estimate so you get the idea of drag from a Bafang geared hub front motor SWX.
rotating weight: m = 1.5kgs
r = distance between the centre of gravity of the wheel minus the motor core to the centre of the hub: 26"/2 = about 165mm.
RPM when power was turned off: 200 RPM (assumed value)
moment of inertia = m x r ^2 (mr squared) = 0.041 kgm2
angular speed = 200/30 * pi() = 20.9 rad/sec
rotational kinetic energy of the wheel at the moment the power was cut: KR = 0.5 * [Moment of inertia × (Angular velocity) squared = 9 Joules
Time to lose all that energy through drag: about 70 seconds
average drag: 9 J / 70s = 0.13W
speed at mid freewheeling: about 30 rpm
The drag goes up with speed, so it's safe to assume that at your average speed of 15mph, you lose about 0.13W*200RPM/30RPM = 1W due to the motor drag.

Very impressive @Woosh- you've earned a cup of tea for that one!