Racing innovation?

bicycle_disciple wrote:
The more interesting question is this : If a world class rider attacks
at 400W+ to get away from his rivals, and assuming he's pedaling at an
optimal cadence, if he switches a hidden 100 W motor on, will the
power of the motor and rider just add together in series? 100+400 =
500 W?

Don't think of it as power, since that's confusing the issue. Think of it as
torque. Where the rider is concerned, he'll find he can spin a smaller
sprocket for a given effort and rpm. Does it matter that it's a tailwind,
descent, or electric motor that allows this? A DC motor's point of view is
just as simple. It delivers torque proportional to current. It doesn't know
or care what else is on the shaft.

I can't imagine that happening , since the rider's power is so much it
has swamped the puny motor power. Now I can see how a normal cyclist
will feel that his effort almost halved, well that's because normal
cyclists don't produce 400W. Its more like 100 or 150W average for the
typical commute.

For the world class rider, I imagine a 100W motor giving something
even less than a "gentle push". How significant is this?

100W is about 1.5 W/kg for some typical size rider. I picked 100W as being
both significant and easily achievable. If you need more boost, size the
components larger. A link posted elsewhere in this thread shows a commercial
200W setup, using a hobby grade DC motor and planetary reduction gear. These
are typical of motors sold to power model airplanes. (The telltale gear
whine in the videos is from the planetary reduction gear. A purpose-built
brushless motor won't need one, and will be much quieter and more difficult
to detect.)

It's simple enough to make from store bought parts that I'm considering
putting one in the wife's bike so she can tag along on non-training rides.
The only real world problem is implementing a reliable kill switch. I think
I would want it on the rear brake cable.

On 1 June, 10:25, "MikeWhy" wrote:

It's simple enough to make from store bought parts that I'm considering
putting one in the wife's bike so she can tag along on non-training rides.
The only real world problem is implementing a reliable kill switch. I think
I would want it on the rear brake cable.

Use a co-ax connecter with a cord pull under the saddle. In an
emergency stop, the rear wheel will likely be in the air anyway so
with the off chance that a trigger circuit based on spindle movement
fails, the spinning wheel will be of little consequence. Would also
suggest you place a toggle switch under the saddle nose as to select
the assist mode.

Chalo wrote:
bicycle_disciple wrote:
The more interesting question is this : If a world class rider attacks
at 400W+ to get away from his rivals, and assuming he's pedaling at an
optimal cadence, if he switches a hidden 100 W motor on, will the
power of the motor and rider just add together in series? 100+400 =
500 W?

I can't imagine that happening , since the rider's power is so much it
has swamped the puny motor power. Now I can see how a normal cyclist
will feel that his effort almost halved, well that's because normal
cyclists don't produce 400W. Its more like 100 or 150W average for the
typical commute.

For the world class rider, I imagine a 100W motor giving something
even less than a "gentle push". How significant is this?

Assuming the technical challenges could be conquered and that an
assist motor could be contrived to contribute 100W at any racing speed
(which is pretty far-fetched), that would be well in excess of any
natural advantage possessed by one professional racer over another.

I don't see that as far fetched. If the motor is coupled directly to the
BB spindle, then the motor/gearing RPM is constrained to the cadence,
regardless of the bike speed.

I have heard Lance Armstrong's advantage over his contemporary rivals
characterized as 10 watts. That should put the advantage of a 100W
assist in perspective.

100W power assist on an e-bike, in contrast, is decidedly not worth
the trouble.

Depends on the objective. If the average rec rider has 100W average and
200W peak, a 200W motor with a 150 W-h battery can double the rider's
effective power over a 90 minute ride. Many rec riders are stymied by
the occasional steep hills they encounter on an otherwise not too
challenging ride.

The Gruber is rated at 200W, a 135 W-h battery brings the total weight
to 2 kg.

One of those would be perfect for our 30 mile, ~90 minute weekly club
rides. With my combined rider & bike weight of ~260 lb, I'd never notice
the extra 5, but with an extra 200W at my fingertip, I'd kick ass in
spectacular fashion. Gotta quiet down that drive, though.

On Jun 1, 3:25*am, "MikeWhy" wrote:
bicycle_disciple wrote:
The more interesting question is this : If a world class rider attacks
at 400W+ to get away from his rivals, and assuming he's pedaling at an
optimal cadence, if he switches a hidden 100 W motor on, will the
power of the motor and rider just add together in series? 100+400 =
500 W?

Don't think of it as power, since that's confusing the issue. Think of it as
torque.

You have it backwards. Power is power. 100 watts is 100 watts. For any
given power higher torque means lowers rpms and vice versa.

If the motor assist is putting out 100 watts AND has to match the
rider's cadence then it is operating at pretty high torque - at least
relatively speaking. But that is torque turning the bottom bracket
spindle, which is not the same as the direct torque of the motor.
The Gruber device describes using a planetary gear transmission,
presumably a reduction gear.

That starts to look pretty feasible, especially looking at other very
common technology, for example the cordless drill.
Take a look he
http://autospeed.com/cms/A_110376/ar...popularArticle.

If a typical planetary transmission as shown there can provide a
reduction of 30:1, a motor that puts out 100w @2000rpm can be reduced
to a more "cadence-like" 66.6 rpm. So that is essentially +/- 100W
(yes allow for some transmission loss) to the crank at a speed which
matches a normal cycling cadence.

DR

On Jun 1, 1:10*am, bicycle_disciple wrote:
The more interesting question is this : If a world class rider attacks
at 400W+ to get away from his rivals, and assuming he's pedaling at an
optimal cadence, if he switches a hidden 100 W motor on, will the
power of the motor and rider just add together in series? 100+400 =
500 W?

I can't imagine that happening , since the rider's power is so much it
has swamped the puny motor power. Now I can see how a normal cyclist
will feel that his effort almost halved, well that's because normal
cyclists don't produce 400W. Its more like 100 or 150W average for the
typical commute.

For the world class rider, I imagine a 100W motor giving something
even less than a "gentle push". How significant is this?

Umm ..... 25% ?
Hardly a "gentle push," more like having the benefit of the power of
an extra half a leg to pedal with.

DR

On 1 June, 18:22, DirtRoadie wrote:
On Jun 1, 3:25*am, "MikeWhy" wrote:

bicycle_disciple wrote:
The more interesting question is this : If a world class rider attacks
at 400W+ to get away from his rivals, and assuming he's pedaling at an
optimal cadence, if he switches a hidden 100 W motor on, will the
power of the motor and rider just add together in series? 100+400 =
500 W?

Don't think of it as power, since that's confusing the issue. Think of it as
torque.

You have it backwards. Power is power. 100 watts is 100 watts. For any
given power higher torque means lowers rpms and vice versa.

If the motor assist is putting out 100 watts AND has to match the
rider's cadence then it is operating at pretty high torque - at least
relatively speaking. But that is torque turning the bottom bracket
spindle, which is not the same as the direct torque of the motor.
The Gruber device describes using a planetary gear transmission,
presumably a reduction gear.

That starts to look pretty feasible, especially looking at other very
common technology, for example the cordless drill.
Take a look hehttp://autospeed.com/cms/A_110376/ar...popularArticle.

If a typical planetary transmission as shown there can provide a
reduction of 30:1, a motor that puts out 100w @2000rpm can be reduced
to a more "cadence-like" *66.6 rpm. So that is essentially +/- 100W
(yes allow for some transmission loss) to the crank at a speed which
matches a normal cycling cadence.

DR

; ) looks like that example will fit in a main bicycle frame tube if
not a seat tube.

bicycle_disciple wrote:
On Jun 1, 5:08 am, thirty-six wrote:
On 1 June, 08:10, bicycle_disciple wrote:

The more interesting question is this : If a world class rider
attacks at 400W+ to get away from his rivals, and assuming he's
pedaling at an optimal cadence, if he switches a hidden 100 W motor
on, will the power of the motor and rider just add together in
series? 100+400 = 500 W?

Depends on the design of the motor. Generally high torque motors are
rather restrictive in their operating speed so while may me good to
assist climbing at a regular rate will be pointless for sprinting
which could require a doubling in cadence. It could explain why there
are some 'world class' sprinters who do not seem to exceed 130rpm.
The human body is capable of much more and generally develops most
short term power and therefore greatest acceleration at around 170rpm
following training. At lower cadence it is easier to match the design
speed of a high torque motor. This will be of most benefit to the
unusual concept of a puny sprinter.



I can't imagine that happening , since the rider's power is so much
it has swamped the puny motor power.

That would happen if the rider exceed the peak torque speed of the
motor.

Now I can see how a normal cyclist
will feel that his effort almost halved, well that's because normal
cyclists don't produce 400W. Its more like 100 or 150W average for
the typical commute.

For the world class rider, I imagine a 100W motor giving something
even less than a "gentle push". How significant is this?

Much if a following rider has no draught and is similarly endowed
with ability. At a critical moment in a race it would certainly
demoralise the opposition. I think the most useful way to use such a
device would be to jump without it, in the knowledge that in a
minute or two later the rider can use it to maintain a steady lower
speed while recovering from the anaerobic effort. The assistance
while recovering will speed up the recovery and allow the lead rider
to jump again should he be caught quickly with little chance of the
catchup rider making an all-out effort.

It still is not convincing me that motor power and rider power will
add one to one. On a DC motor, the max power would fall at about half
of stall torque. So if the rider pedals at a cadence such that his RPM
corresponds with the motor's optimal RPM for max power, and then he
switches the motor on, would the two torques add up? On paper, it
seems like those two torques will be superimposed on each other to
give a higher torque, which then multipled to RPM would give a greater
power. Its difficult for me to believe this will happen in reality
though. Any more insights from anyone else?

The misunderstanding likely comes from a simplistic view of motor
controllers. I played with them as a child, and controlled them with simple
switches and also with thumb controlled rheostats on the slot car set. I can
certainly see where this view leaves a gap in understanding that needs to be
bridged.

Max torque and current draw occur at full stall, but that's not important
for our use. Our presumption is that the crank is turning, in our case at
the crank speed set by the rider. Current draw is directly related to torque
demand. If the rider is supplying all the drive power, turning the crank at
or above the target speed, the torque demand is zero, and the motor
controller freewheels by holding the windings open. When the rider is unable
to keep up with the demand load, as evidenced by crank speed dropping below
the target speed, the motor controller cranks up the amps, and the motor
responds by supplying torque, up to the capacity of the battery or some
other limit, such as heat constraints on the motor windings.

The controller can be as simple as a direct on/off switch, in which case the
motor would spin at whatever rpm the battery characteristics allow. More
sophisticated controllers can operate at constant voltage, constant current,
or constant speed, whichever is appropriate for the application. Constant
speed is appropriate for driving a bicycle crank.

Brushless DC motor controllers operate closed loop by necessity. They
deliver drive current to the windings in phase with the rotor's rotation
past the stator magnets. Rather than interrupting and reversing current with
stationary brushes, they do this actively by sensing the rotor position and
timing its power pulses, usually without need for additional sensors. At any
given time, at least one winding is unpowered. Typical brushless controllers
read the reverse voltage on that winding to determine rotor speed and
position. For our constant speed controller, if the rotor speed is below the
target speed, current is increased to deliver more torque. Voila. No
superposition or complicated external considerations needed.

The "magic" of brushless DC motors is all around you as you read this. The
cooling fans on the CPU and in the power supply are brushless, as are the
drive motors in the hard- and optical-drives. Brushless controllers are
cheap, common, and accomplished fact. The controller and motor for a bicycle
crank can be bought from your local hobby shop. The real difficulty is
connecting it to the crank spindle. For this, you'll need to buy the parts
from that interweb place, or have a machinist friend build one for you when
he builds his own. I intend to take this latter path.

On May 31, 6:20*pm, "MikeWhy" wrote:
Jay Beattie wrote:
If the motor is not on, does it drag? -- Jay Beattie.

Yes, it will drag. Some small bearing and gear train losses; some cogginess
due to the magnets pull on the ferrous rotor. As a practical matter,
averaging 1 inch lb over a full rotation equates to about 1 watt of power
loss. About the same as an extra pint of excess hydration on the rider on a
very moderate slope.

If I understand the Gruber description correctly, I expect that any
drag would be even less than what you describe. There is a freewheel
that I assume isolates the final drive from the motor and
transmission.

So the drag would be more like the the drag of a typical rachet or
bicycle freewheel. There would be no drag at all coming from the motor
or transmission (planetary reduction gears) and minimal drag coming
from the unloaded (but engaged) bevel drive gears.

DR

On Jun 1, 12:01*pm, thirty-six wrote:
On 1 June, 18:22, DirtRoadie wrote:





On Jun 1, 3:25*am, "MikeWhy" wrote:

bicycle_disciple wrote:
The more interesting question is this : If a world class rider attacks
at 400W+ to get away from his rivals, and assuming he's pedaling at an
optimal cadence, if he switches a hidden 100 W motor on, will the
power of the motor and rider just add together in series? 100+400 =
500 W?

Don't think of it as power, since that's confusing the issue. Think of it as
torque.

You have it backwards. Power is power. 100 watts is 100 watts. For any
given power higher torque means lowers rpms and vice versa.

If the motor assist is putting out 100 watts AND has to match the
rider's cadence then it is operating at pretty high torque - at least
relatively speaking. But that is torque turning the bottom bracket
spindle, which is not the same as the direct torque of the motor.
The Gruber device describes using a planetary gear transmission,
presumably a reduction gear.

That starts to look pretty feasible, especially looking at other very
common technology, for example the cordless drill.
Take a look hehttp://autospeed.com/cms/A_110376/ar...popularArticle.

If a typical planetary transmission as shown there can provide a
reduction of 30:1, a motor that puts out 100w @2000rpm can be reduced
to a more "cadence-like" *66.6 rpm. So that is essentially +/- 100W
(yes allow for some transmission loss) to the crank at a speed which
matches a normal cycling cadence.

DR

; ) looks like that example will fit in a main bicycle frame tube if
not a seat tube.

Now there's a thought, potential for lots of space (think old
Cannondale) although that is not very conducive to a "retro-fit."

DR



DR

On 1 June, 19:37, DirtRoadie wrote:
On Jun 1, 12:01*pm, thirty-six wrote:



On 1 June, 18:22, DirtRoadie wrote:

On Jun 1, 3:25*am, "MikeWhy" wrote:

bicycle_disciple wrote:
The more interesting question is this : If a world class rider attacks
at 400W+ to get away from his rivals, and assuming he's pedaling at an
optimal cadence, if he switches a hidden 100 W motor on, will the
power of the motor and rider just add together in series? 100+400 =
500 W?

Don't think of it as power, since that's confusing the issue. Think of it as
torque.

You have it backwards. Power is power. 100 watts is 100 watts. For any
given power higher torque means lowers rpms and vice versa.

If the motor assist is putting out 100 watts AND has to match the
rider's cadence then it is operating at pretty high torque - at least
relatively speaking. But that is torque turning the bottom bracket
spindle, which is not the same as the direct torque of the motor.
The Gruber device describes using a planetary gear transmission,
presumably a reduction gear.

That starts to look pretty feasible, especially looking at other very
common technology, for example the cordless drill.
Take a look hehttp://autospeed.com/cms/A_110376/ar...popularArticle.

If a typical planetary transmission as shown there can provide a
reduction of 30:1, a motor that puts out 100w @2000rpm can be reduced
to a more "cadence-like" *66.6 rpm. So that is essentially +/- 100W
(yes allow for some transmission loss) to the crank at a speed which
matches a normal cycling cadence.

DR

; ) looks like that example will fit in a main bicycle frame tube if
not a seat tube.

Now there's a thought, potential for lots of space (think old
Cannondale) although that is not very conducive to a "retro-fit."

DR

DR

Hacksaw the BB shell open and weld it up after installing the drive
unit in the main tube.