VIDEO: climbing 30-40% hills with Bafang Front HUB

[Kraeuterbutter]

Hi...
i made this videos for German forum two weeks ago, but maybe they are interesting for you too...

when I first came here to the forum, I thought i need a bike, were the motor can use the gears..

Point 1:

everywhere you heard, that Hubmotors do not run efficient at hills, and are not at all suitable for going up hills

well.. part of that is right,
but as someone in other forum wrote in an article:

we are not driving E-Bikes, we are driving "Hyprids"...
there is the motor, and there is the human
and the human can still use the gears !

i have an Bafang 24V 180Watt Motor in my bike,
powering it from 36Volt-Batteries with an 14A controller
tires are 26"x2,35" BigApple

this little beast is a fast motor as this video may show:

Video YouTube - Bafang Speedtest 50km/h

on this video, a "booster"-pack was used (2s Lipos with 7,4Volt)
the voltage on load was about 41Volt

so: its a little fast motor, not realy a torque-monster with that setup

i tested the torque: hills with 8-9% without pedaling are NOT possible
(20kg bike, 78kg driver -> so ~100kg)

nevertheless:
here are some videos of doing hills from 30% - 40% as an hyprid mashine (motor + human)

some datas:
temperature in the shadow was minus -8°C rising to -5°C during filming

the tires are Big Apples, roadtires, not realy suitable for heavy offroad-use

Video 1: YouTube - Bafang Bergfahrt
the slope at the end of the hill is 38%, with motor doable, without motor (second try) not
the slope in the video-center-position: 34%

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Video 2: YouTube - Bafang Bergfahrt Part 2
there are slippery leaves/foliage
first with motor -> its easily doable
then two tries without motor and not so good results

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Video 3: YouTube - Bafang Bergfahrt Part 3
first with motor
second without motor
i use noose/straps/loop on the pedals, so a little accident on that video happend

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Video 4: YouTube - Bafang Bergfahrt Part 4
doing a hill with only one hand on the handle-bar, the other one in the air
first with motor -> no problem
then without motor.. you see, very soon i have to use both arms

the slope when driving behind the dog and on the right side i have measured with 21% and 23%
on the left side the slop goes up, up to 38%


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Video 5: http://www.youtube.com/watch?v=QtcGhQ50FWE
30% rising to 38% slope


i have measured, were i actually was driving, not somewere else on the slope

Point 2:
another thing i have often read: you can´t go offroad with an front-hub, you need a reardrive (rearhub, or drive through gears) for that,
because the front-hub will spin and spin and spin, of absolut no use because front wheel is lifted

i think the videos should show, that also with a fronthub, which results in a all-wheel-drive, going up hills is doable
(as said, the motor is no torque-monster)

the bike is geard 28:28 in first gear, which is too fast for my leg-power and the hill-grades
the motor is not able to do 8-9% for its own, but is nevertheless a great help at even steep hills

i think with this road-tires on the video and a REAR-motor i would not have the same good results climbing hills,

because all the torque would go to the rear-wheel, resulting in

• lifting up the front more easily
• loosing traktion on the rear more easily
• weight-distributation would be worse with an rear-hub (see also point 1)

so..
maybe this was interesting or funny to watch for some..
maybe i even get some comments and thoughts...
greets,
Reini

 

[John in CR]

Reini,

Thanks for sharing that. Have you gone up any long (multi-kilometer) hills? If so how was the motor temp? Also, you still going strong with just the factory planetary gears?

John

 

[Kraeuterbutter]

Hi..
i don´t know if you can see this on the vids..
we have only a max. of 150hm... no higher hills here at once...
(of course on a tripp, there it can be 600hm or more... but at once only 150hm)

for the temperature:
look at the two graphics...
i continoue in the next posting

 

[voicecoils]

Good stuff.

No helmet and front wheel power slides,

I have found my Bafang Front (with metal gears) is quite helpful to climb one steep ramp I have encountered. I continued to pedal but muscular effort was minimal. No problem with tire losing contact with the road (dry conditions).

 

[Kraeuterbutter]

on the Bafang I use (and you all do so, otherwise the motor would burn) a controller with current limit...

for my Bafang thats a controller with 14A limit

when you look at the second graph you can see: without that limit, the input watts would explode, and the watts lost (= heat) would explode as well...

with the controller with current limit (1st graph) you can see:
when the motor turns slower, the controller does reduce the "volts" (not realy, its how it "cuts" the electricity - sorry for my English), so the amps do not go over the limit..

result: the slower it is spinning, the less energy (Wh) are coming from the battery
the efficience of the motor goes down as well..

nevertheless: - and now look close to the graph - the lost Watts are not higher than when it spinns fast...

and thats the same finding i made in praxis too:
the motor does not get warmer when climing hills, as when going flat (at the amp-limit)
infact its even (in this graph) so, that the lost watts (= heat) is less when climing a hill than when going fast

the graphs do not show a bafang, but the caracteristics are same for all motors and controllers

for the gears: no, no shredded gears.. why should the shred ?
because of 38% hill ?

torque = amps...
amp-limit is set to 14A
so: the torque is not more when climing up a hill... as long as i go fullthrottle and slower than 33km/h the currents are at 14A and for that the torque is all time the same !!

the gears get warm and stripp because of
1.) high load
2.) high rpm (makes them warmer, softer)

both together happen, when you use 72V (i don´t, i use only 36V)
and a 25A or 30A limit controller (i don´t, i use now a 14A controller, but will switch to 12A because of better efficience)

have i high load ? no, not realy, because of the 14A controller, more or less within the specs
have i high rpm ? not when climing hills, so the gears will be fine



until now iam around 1500km -> no problems..
the only thing i have noticed: (i noticed it on old and newer videos of mine): the motor has become a lot quieter compared to when it was new

 

[pwbset]

Boy those slopes look familiar. Thanks for sharing! I need to get a video camera! I have some steep parts like that in my mountain commute. It is "pea" gravel though so I'm glad I have a rear motor for it as I think a front would spin the gravel. A Clyte 4011 at around 76v sagged under heavy amp load ~28-30A can do this pitch at 30kph with me peddling fast and having good kinetic energy to start. Without peddling the 4011 alone eventually stops pulling near the top of this photo and gets very hot very quickly as it dumps excess watts into heat. Human pedal power I can do this at 10kph tops and feels like my heart is bursting at the top. :lol: