[EVDL] Mid-drive motors versus hub motors for electric bicycles

Hello Larry,

I am using a mountain bike that was converted by Currie Technologies in
Chatsworth, CA. They use a heavy frame because the 1/2 hp 24 volt motor
developed so much torque that it could flip you back wards if it was
lighter.

I purchase it directly from WalMart.com warehouse that was sent directly to
me fully assembly. The bike weighs 110 lbs and with me on it, it is closer
to 300 lbs. Cost $295.00

The motor has a internal gear box that has a gear ratio of 3:1 and a
sprocket gear chain set that has another 3:1 ratio for a total of 9:1
overall ratio. This gear set is on the rear wheel on the opposite side of
the bike chain gear set which freewheels when the electric drive is on.

It use a motorcycle type variable motor control grip that also indicates
battery state of charge lighting up LED's some what the Link-10 does. There
are two 12 volt 20 ah batteries in a cast aluminum waterproof container that
mounted vertical be hind the vertical tube that goes to the seat and down to
the peddles.

I rarely use the peddle drive, because I am either going up or down hills.
This bike now has be running for 3 years and 8 months on the same battery
pack. It suppose to have a maximum range of 15 miles at 15 mph, but I have
never drove it over 5 miles at a time without charging it. If I only drive
it one mile, it only takes about 15 minutes to charge it.

Roland




----- Original Message -----
From: "Larry Gales" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Sunday, September 12, 2010 12:56 PM
Subject: [EVDL] Mid-drive motors versus hub motors for electric bicycles


> Most electric bicycles, e-Bikes, are powered by hub motors, either
> un-geared
> or using planetary
> gears. Even the geared hub motors do not use the bicycle gears, they
> merely
> use internal gears
> that allow the motor to run at a much higher speed, and thus reduce the
> size
> and weight of the
> motor while producing more torque than an un-geared hub motor.
>
> But mid-drive motors drive the chain and sprocket directly, and so they
> can
> use the full range of
> gears provided by most bicycles. It appears to me that mid-drive motors
> are
> much superior to hub
> motors for e-bikes, but I would like to hear the opinions of others to see
> if I am on the right
> track. Here are what I consider to be the advantages of mid-drive motors:
>
> (1) They use the full set of gears provided by the bicycle and so provide
> the best torque and
> hill climbing ability for a given size motor
>
> (2) They free the wheels from any weight or drag caused by a hub motor
>
> (3) They eliminate any extra work required to change tires or wheels
>
> (4) They keep the center of mass in the middle of the bike
>
> (5) They actually reduce the wear and tear on the main sprocket and chain
> because the
> force is uniform over the sprocket rotation as opposed to foot pressure
> that
> peaks at
> a few points
>
> (6) The multiplication of the rider's strength is uniform as opposed to
> the
> jerky forces
> provided by torque sensors.
>
> The only disadvantage that I see is lack of re-generative braking, which
> exists in un-geared hub
> motors.
>
> I came across what looks to me to be an almost perfect e-bike at an
> affordable price at:
> http://www.hightekbikes.com/index.html
> a 350 watt mid-drive motor (the motor drives the chain-wheel so that all
> the
> bike gears are
> utilized giving it awesome hill climbing ability and the wheels are
> totally
> free of any extra
> weight or equipment) on an e-bike that weighs only 46 lbs and costs only
> $1600 + sales tax. If
> anyone has an opinion on such a bike I would like to hear it.
>
> Thanks,
>
>
> --
> Larry Gales
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You really should talk to Andy Schoenberg about this project. He has
been building 3 wheeled EVs using bike parts for years. I think he is
on version number 11 or 12 now. He has built some with hub motors and
some with chain drive, so he knows from experience what is best for
what purpose.

http://www.evalbum.com/2200

http://saltlakecity.craigslist.org/mcy/1945546968.html

KJD

http://www.evalbum.com/3175

Larry Gales wrote:

> Most electric bicycles, e-Bikes, are powered by hub motors, either
> un-geared
> or using planetary
> gears. Even the geared hub motors do not use the bicycle gears,
> they merely
> use internal gears
> that allow the motor to run at a much higher speed, and thus reduce
> the size
> and weight of the
> motor while producing more torque than an un-geared hub motor.
>
> But mid-drive motors drive the chain and sprocket directly, and so
> they can
> use the full range of
> gears provided by most bicycles. It appears to me that mid-drive
> motors are
> much superior to hub
> motors for e-bikes, but I would like to hear the opinions of others
> to see
> if I am on the right
> track. Here are what I consider to be the advantages of mid-drive
> motors:

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It's hard to tell much about this bike just from the photos. As Lee says,
many integrators use really mediocre components, and you often can't tell
even up close.

I guess your best bet is to find someone with experience with the bike. You
might try posting over at the V Is For Voltage forum, where they have a long
history with Ebikes.

One thing I'd be a little less than thrilled about with this one is the
location of the battery. That's usually the heaviest single item on an
Ebike, and IMO over the rear wheel is not the ideal place from a stability
and handling standpoint.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Actually, I am beginning to change my mind about the mid-drive, at least for
small wheel (20")
bikes. I was drawn to the mid-drive because of its inherently high torque
for hill climbing.
But when I look at the hill climbing that I can do with my (direct drive
un-geared)) BIONx 350
watt motor on my 20" wheel bike, and then consider a geared hub motor that
provides much more
torque than my un-geared motor, I suspect that the geared hub motor would be
quite sufficient
even for full size 26" wheels.

In addition, I often now ride the bike in a different way, which I call
"effortless" pedaling.
In this mode I press the throttle, but I also pedal in a very relaxed way
regardless of whether
I am traveling on a flat road or up a steep hill. The effort is similar to
peddling a bike on
a flat smooth road with no wind while cruising at 8-9 MPH. I find that this
increases my range
by 50% over motor-only operation while increasing my hill climbing speed by
at least 20%, and
allowing me to climb hills steeper than motor-only operation allows. This is
a mode of travel
that is ideal for commuting, because it leaves you free of sweat.

I have run some tests with my un-geared hub motor on my 20" wheel bike and
determined its hill
climbing ability by using Google Earth to compute the grade or slope of the
hill. Here are my
results (oh, I weigh about 160 lbs so people would have to adjust these
values for their weight):

(1) For any hill up to a 10 degree slope, motor alone, w/o pedaling, will
propel my to at least
10 MPH. If I employ "effortless" pedaling, I travel at least 12 MPH

(2) For a 12.5 degree hill, the motor alone is not sufficient, but
effortless pedaling will
propel me at about 10.5 MPH

(3) For a REALLY steep hill at 18 degrees (it is frightening to ride DOWN
such a hill), the
motor alone is not sufficient, but if I put the bike in low gear (say gear
2) and pedal with
moderate effort I travel at about 7 MPH. I would estimate the effort to be
about the same as
traveling up a 3 degree slope with no motor assist.

The bottom line, is that if an un geared 350 watt motor can provide such
hill climbing ability,
then a geared hub motor will do much better, so there may be no need for the
extra torque
gained with a mid-drive motor. And this means that 95% of the time, you can
drive in high gear
and so you put very little wear and tear on the chain and sprocket, as the
motor does most of
the work, and you only rarely have to change gears.

Now with 26 inch wheels, you do lose about 30% of the torque, but that
should more than be made
up by switching from an un geared to a geared hub motor . According to this
study:

http://www.ebikes.ca/hubmotors.shtml

a geared Heinzman motor produces 2.3 times the torque of an un-geared motor
of the same power
(but I don't know if that factor is the same for other manufacturers).

So, I think I am in the market for an eBike with a 350 watt geared hub motor

-- Larry

Evan Tuer <[email protected]> wrote:

> On Sun, Sep 12, 2010 at 8:56 PM, Larry Gales <[email protected]>
> wrote:
> > Most electric bicycles, e-Bikes, are powered by hub motors, either
> > un-geared or using planetary gears. Even the geared hub motors do
> > not use the bicycle gears, they merely use internal gears that allow
> > the motor to run at a much higher speed, and thus reduce the size
> > and weight of the motor while producing more torque than an un-geared
> > hub motor.
> >
> > But mid-drive motors drive the chain and sprocket directly, and so they
> > can use the full range of gears provided by most bicycles. It appears
> > to me that mid-drive motors are much superior to hub motors for
> > e-bikes, but I would like to hear the opinions of others to see if I am
> on
> > the right track.
>
> For a legal power level hybrid / commuter bike, you are probably
> correct. A colleague has a mid-drive bike, it's a Panasonic system
> and was very expensive, but it's impressive. Completely quiet, it has
> torque controlled assist and has been completely reliable with serious
> mileage.
>
> I use a direct drive (no gears) hub motor in the rear wheel of a heavy
> mountain bike. This is mainly because mid drive kits at silly power
> levels are noisy, and chain and sprocket wear and breakage is a
> frequent problem. The hub motor and controller do have regen as you
> mentioned, which I find very helpful, and finally it was a much
> cheaper solution.
>
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--
Larry Gales
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