Failed on my first big hill

[Deleted member 4366]

Looks like you're starting to get it, Flud, but there's one more point you need to understand. Most hub-motors in ebikes that you'll see on our roads have internal gearing. Different motors have different internal gearing, which affects the wheel-speed at which the motor can produce high torque and efficiency. Some motors have 5:1, some 8:1, and now we're starting to see higher ratios.

Also, the motor can be wound for different speeds. For a bike with a limited speed of 15 mph, it's typical for the motor to be wound for a maximum speed of around 20 to 22mph so that it makes high power at maximum efficiency in the area of 15 mph. If you want a good hill-climber, you could wind it for a maximum speed of 15 mph, which shifts the whole power and efficiency curves down the rpm axis in direct proportion. Take a typical Bafang 250w SWX motor that's commonly found in ebikes. You can get it in 180, 201, 230, 250, 270, 320 rpm versions, so 180 rpm if you need hill-climbing, 320 rpm if you want speed. The advantage of the crank-drive is that it can do both with the same motor, not that it's better than a hub-motor at either end of the scale.

While I'm on the subject, I opened up one of the recent small Bafang front motors yesterday to find that it now has two-stage gearing inside like the Q100, so it looks like they've increased the reduction ratio from 5:1 to about 8:1. It has helical gears on the motor output shaft and straight-cut ones to the hub.

 

[(NoLongerRegistered#15675)]

Yep ,I see all that..
Not taking Michael , I will get/beg/borrow/ steal a good hub drive mtb and give it a go.
Take care.
Would be good to see other folk post about rides..not Starva, but with a view to battery usage/ range/ height gained/ time out.

And yes we are getting there..."CD can do both with motor"...think that's what I was trying to say...but perhaps "both in same application but I,d guess with a reduction in efficiency over one dedicated to one end of spectrum..(or middle of spectrum as in ordinary road bikes)"

Take care.

 

[danielrlee]

Also, the motor can be wound for different speeds. For a bike with a limited speed of 15 mph, it's typical for the motor to be wound for a maximum speed of around 20 to 22mph so that it makes high power at maximum efficiency in the area of 15 mph. If you want a good hill-climber, you could wind it for a maximum speed of 15 mph, which shifts the whole power and efficiency curves down the rpm axis in direct proportion. Take a typical Bafang 250w SWX motor that's commonly found in ebikes. You can get it in 180, 201, 230, 250, 270, 320 rpm versions, so 180 rpm if you need hill-climbing, 320 rpm if you want speed.

Having already jumped to your defence in this thread, I'm now going to go the other way.

I thought that old myth about motor windings and turn counts being better for one purpose or another had been dispelled. Assuming the same copper fill, a lower turn count motor running on a lower voltage and higher amperage gives no less torque than a higher turn count motor running on a higher voltage at lower amperage.

 

[danielrlee]

Also, I'd like to publicly apologise to you Flud. Although I'd still chose to 'stand my ground' as so to speak and call you on the BS, the name calling was uncalled for and a dick move on my part.

Sorry Flud.

 

[(NoLongerRegistered#15675)]

There,s a lot of confusion over winding choice in dc brushless. Yes it follows same rules as "delta" " wye" as in other none brushless but to a far lesser extent.
DC brushless can be manipulated by controller to alter torque characteristics, result is a big overlap.
Brushless operate sort of amalgam between induction and old fashioned dc...with characteristics of both and neither !!

Both winding type give max torque low revs in brushless !! In old dc motors characteristics were "poles" apart. ( ie starter motor versus model train..if you get those wrong train would do 80 mph and blow up..starter motor would do nowt)
( ie series wound would rev to infinity non load..might be other way round..long time since uni)

 

[(NoLongerRegistered#15675)]

Also, I'd like to publicly apologise to you Flud. Although I'd still chose to 'stand my ground' as so to speak and call you on the BS, the name calling was uncalled for and a dick move on my part.

Sorry Flud.

That's really good of you. Thanks. You didn't have to, I do tend to annoy folk, wife calls me far worse and never apologises.
Besides, reading my post....it was deserved.
So my apologies too.


Oh and I really owe d8 a bigger apology...my response to you was in response to Dan,s comment...sort of totally messing it all up. Mistaken identity..
So double apologies.Bad response to wrong person !!

 

[danielrlee]

That's really good of you. Thanks. You didn't have to, I do tend to annoy folk, wife calls me far worse and never apologises.
Besides, reading my post....it was deserved.
So my apologies too.

*shakes hands*

You never know, maybe we'll all get to ride together one day in a big pedelec love-fest tour. Of course, I imagine I'll be spending most of my time waiting for you at the top of each hill while I watch you climb it at a snails pace.

Sorry, couldn't resist it

 

[(NoLongerRegistered#15675)]

*shakes hands*

You never know, maybe we'll all get to ride together one day in a big pedelec love-fest tour. Of course, I imagine I'll be spending most of my time waiting for you at the top of each hill while I watch you climb it at a snails pace.

Sorry, couldn't resist it

Nope you wont.,ll bring my CRF 250 .. I,ll cross out cc and scribble watts..
Will look odd with pedals !!

But ofcourse to shaking hands...

 

[Deleted member 4366]

Having already jumped to your defence in this thread, I'm now going to go the other way.

I thought that old myth about motor windings and turn counts being better for one purpose or another had been dispelled. Assuming the same copper fill, a lower turn count motor running on a lower voltage and higher amperage gives no less torque than a higher turn count motor running on a higher voltage at lower amperage.

It's true that the torque is the same, but the efficiency can be massively different. The best climbing motors have high speed motors with big internal reduction ratios. Some different speed motors have different reduction ratios, like the Q100 and Q100H, where the Q100H is basically a 328 rpm Q100 with the gearing changed to 260 rpm, so it has a lot more torque than the 260rpm Q100. The discussions on torque vs winding speed were mainly referring to DD motors. It all goes out the wndow as far as geared motors are concerned.

 

[(NoLongerRegistered#15675)]

On motor efficiency ...my response was missing point a bit..

Fewer windings/ higher current as almost got to be overall less efficient.
Induced internal voltage will be very similar but heat generated / losses will always be worse with equal power ...heat waste is proportional to current squared...all situations which reduce current help overall efficiency..( ie higher voltage, more windings...for a given output..)

Other problem with dc brushless is induced voltage/ current within motor wundings can be higher than actually supplied by battery.( doesn,t add to power output, but motor readings can be well over both current used...which is unique to dc brushless. ( I think) and does lead to over estimates of power consumed..( has bearing on efficiency and power out) You must measure power in , power produced to get actual efficiency.

 

[danielrlee]

It's true that the torque is the same, but the efficiency can be massively different. The best climbing motors have high speed motors with big internal reduction ratios. Some different speed motors have different reduction ratios, like the Q100 and Q100H, where the Q100H is basically a 328 rpm Q100 with the gearing changed to 260 rpm, so it has a lot more torque than the 260rpm Q100. The discussions on torque vs winding speed were mainly referring to DD motors. It all goes out the wndow as far as geared motors are concerned.

That's a fair point I missed.

I'm far too abusive on geared hubs for them to last long and gave up on them a while ago for all but the most lightweight of my bikes. As you can see, I never really consider them in my thought process.

 

[(NoLongerRegistered#15675)]

That's a fair point I missed.

I'm far too abusive on geared hubs for them to last long and gave up on them a while ago for all but the most lightweight of my bikes. As you can see, I never really consider them in my thought process.

What's your bike if not geared hub then Daniel ??
Assuming direct drive ??

 

[danielrlee]

Yeah, my 'everyday' bike is a hardtail DD running 3kW hot off the charger. As you can imagine, my battery packs are somewhat larger than yours.

I love the simplicity and reliability of a DD hub and when I'm cruising with only the noise of the tyres and the wind in my face, wouldn't consider anything less refined.

 

[danielrlee]

I think what this thread reinforces, is that there's no such thing as the perfect bike, just one that's right for a particular purpose. The advice to try as many as possible before buying is the best post made throughout.

 

[danielrlee]

On motor efficiency ...my response was missing point a bit..

Fewer windings/ higher current as almost got to be overall less efficient.
Induced internal voltage will be very similar but heat generated / losses will always be worse with equal power ...heat waste is proportional to current squared...all situations which reduce current help overall efficiency..( ie higher voltage, more windings...for a given output..)

Swings and roundabouts really. Sure, higher currents require heavier conductors, but the lower voltages involved give a simplified battery and BMS. This probably isn't much of a concern for legal bikes, but once you start dealing with multi-kW setups and complex battery arrangements, gives food for thought.

A fascinating thread on ES (maybe my favourite of all time) that discusses this can be found below:

https://endless-sphere.com/forums/viewtopic.php?f=2&t=64907

EDIT: Forgot to mention, motor efficiency is the same where different winds produce the same torque (assuming same copper fill). Don't forget, phase resistance changes with the winding count and the end result is the same heat generated. The only other losses are system-wide losses that can be overcome with heavier conductors as mentioned above.

 

[(NoLongerRegistered#15675)]

Swings and roundabouts really. Sure, higher currents require heavier conductors, but the lower voltages involved give a simplified battery and BMS. This probably isn't much of a concern for legal bikes, but once you start dealing with multi-kW setups and complex battery arrangements, gives food for thought.

A fascinating thread on ES (maybe my favourite of all time) that discusses this can be found below:

https://endless-sphere.com/forums/viewtopic.php?f=2&t=64907

EDIT: Forgot to mention, motor efficiency is the same where different winds produce the same torque (assuming same copper fill). Don't forget, phase resistance changes with the winding count and the end result is the same heat generated. The only other losses are system-wide losses that can be overcome with heavier conductors as mentioned above.

Read all that...conclusion seemed to be there wasn't one ???

When I worked in industry it was taken as a truth that for higher efficiency...higher voltage..lower current...but more dangerous...but things move on..we didn't have time to debate as in link...needed to get it working yesterday...
Hybrid cars are now at point where fire service deal with electric side as industrial, with instructions hhhow to shut down etc before commencing work on them...yes its not just higher voltage...but its related..
Was once considering building an electric powered 7 style car.( built quite a few bike engined ones and a couple of car engined)Bloke from Siemens put me off , once he mentioned folk had been killed messing with system I was considering.( and not run over)

Used an R1 instead... Went like feck but awful on road...

 

[danielrlee]

Read all that...conclusion seemed to be there wasn't one ???

Seemed pretty conclusive to me. The only reason the thread is so long is that the DD torque/speed wind myth is so widely propagated and so many people arent aware of the truth.

 

[(NoLongerRegistered#15675)]

Seemed pretty conclusive to me. The only reason the thread is so long is that the DD torque/speed wind myth is so widely propagated and so many people arent aware of the truth.

Only conclusive if you discount a few opinions early on in thread...
Later ones made more sense...but interpreting thread is like original argument...open to interpretation depending on what you want to believe...and probably thought in first place...its that momentum thing again...

 

[(NoLongerRegistered#15675)]

Only conclusive if you discount a few opinions early on in thread...
Later ones made more sense...but interpreting thread is like original argument...open to interpretation depending on what you want to believe...and probably thought in first place...its that momentum thing again...

But only on here could we argue about an argument ???


A good bike...

Somewhere I there was a claim about an ebike ( based on push bike presumably) that could do standing quarter in 11 something seconds...now that takes some believing...
My Westfield with 2.0 Zetec could just about manage 13 !!! Like to give him a race at. Elvington...

 

[danielrlee]

But only on here could we argue about an argument ??? View attachment 13667


A good bike...

Somewhere I there was a claim about an ebike ( based on push bike presumably) that could do standing quarter in 11 something seconds...now that takes some believing...
My Westfield with 2.0 Zetec could just about manage 13 !!! Like to give him a race at. Elvington...

It's funny you mention that.......

That'll be the deathbike. I think it's still a record holder. It's made by a user over at Endless Sphere called liveforphysics (LFP). LFP is the very person in the 'Science, Physics, Math and Myth' thread posted above who clears up much of the misconception. I think he now works as a lead engineer at Zero Motorcycles.