Which is the best internally geared hub?



In article <[email protected]>,
Ben C <[email protected]> wrote:

> On 2007-10-20, Tim McNamara <[email protected]> wrote:
> > In article <[email protected]>,
> > [email protected] wrote:
> >
> >> I just found an interesting article from BERND Rohloff. He discuss
> >> the importance of the "IDEAL" gear for the engine (human leg). And
> >> the answer is:
> >>
> >> Small (15%) and constant gear steps over the appropiate overall
> >> gear ratio! YES!

> >
> > "YES?" Why "YES!" with such emphasis? Since this is Rohloff's
> > opinion that happens to support the hub he designed, it is not an
> > independent verification of anything.
> >
> > And he's also not necessarily right, either. The human body has a
> > much broader range of efficient functioning than is the case for
> > engines. Mistaking humans for "engines" causes all kinds of
> > conceptual problems and is a practice that should be stopped.

>
> My bike has 18 gears which are good for speeds in the range 0 to
> 30mph. My car has only five for 0 to 110mph.
>
> About 4 of the bike's gears overlap, so there are really 14 gears.
> This still means about one gear for every 2mph increment.
>
> Surely the car engine is much the more flexible?


Demonstrating that we're not engines. Trying to conceptualize ourselves
as engines leads to false conclusions about what makes for "efficient"
cycling.

I did a casual 56 mile ride yesterday on my 3 speed. My average speed
over that route was 16.2 mph, basically the same as my average speed at
the same perceived exertion over the same route on any of my derailleur
bikes. My cadence was quite a bit more variable because the steps
between the gears are quite a bit larger than is the case with my other
bikes. Clearly the 3 speed would be considered "less efficient" because
I could not keep my cadence within some "ideal" range (say, 80-120 RPM
has is often recommended in books), but it made not one whit of
difference in terms of performance nor in terms of enjoyment.
 
In article <[email protected]>,
Ben C <[email protected]> wrote:

> On 2007-10-20, Tim McNamara <[email protected]> wrote:
> > In article <[email protected]>,
> > [email protected] wrote:
> >
> >> I just found an interesting article from BERND Rohloff. He discuss
> >> the importance of the "IDEAL" gear for the engine (human leg). And
> >> the answer is:
> >>
> >> Small (15%) and constant gear steps over the appropiate overall gear
> >> ratio! YES!

> >
> > "YES?" Why "YES!" with such emphasis? Since this is Rohloff's opinion
> > that happens to support the hub he designed, it is not an independent
> > verification of anything.
> >
> > And he's also not necessarily right, either. The human body has a much
> > broader range of efficient functioning than is the case for engines.
> > Mistaking humans for "engines" causes all kinds of conceptual problems
> > and is a practice that should be stopped.

>
> My bike has 18 gears which are good for speeds in the range 0 to 30mph.
> My car has only five for 0 to 110mph.
>
> About 4 of the bike's gears overlap, so there are really 14 gears. This
> still means about one gear for every 2mph increment.
>
> Surely the car engine is much the more flexible?


Well, as others have mentioned, humans are not internal combustion
engines, and we share neither the quirks nor the characteristics of them.

When you talk about, for example, usable powerbands, a typical car
engine might generate usable power from 1000-6000 rpm, which is a "6x"
range. In terms of actual running range, it probably stalls at 600 rpm
or so, and maybe it runs to 6600 rpm before the rev limiter kicks in, so
call it "11x" running range.

That, broadly speaking describes the width of the powerband, though
usually the term is used to describe the area of the rev range where the
engine is putting out a high percentage of its maximum power. So a
racerboy might describe this same theoretical engine as having a 2000
rpm powerband, from 5200-6200 rpm or some such. It matters not.

The thing that distinguishes humans, in this case, is that they don't
stall. You and I can generate power at as few rpm as can be imagined,
and most of us can manage 100 rpm. A few can go rather higher than that.

That's pretty flexible! If you assume a practical 10-120 rpm range (10
rpm being not inconceivable as an "instantaneous" rev rate shortly after
a standing start), you're at 12x already. Better than the car!

Of course, humans in good form produce a horsepower or so for short
periods of time. 50cc scooters put out 6-10 times that power, and cars
produce hundreds of times that power in some cases, and will do so until
they run out of gas. For that, we'll put up with the compromise of
needing a clutch and not having a 0 rpm stall speed.

Right now the future looks very electrical, and EVs motors are the best
of both worlds (0 rpm stall speeds plus high power). It is only in the
storage area where EVs let us down, managing to be mostly left
hopelessly flailing in the face of the cheaply available energy capacity
of diesel, gas, and a few other hydrocarbons.

However, the future is getting closer: Tesla may actually start putting
cars in the hands of customers in the next few months, and if you're
willing to accept restricted ranges and slow charge times, the future
can be here now. There's a few EV companies that will sell you (as far
as I can tell) a vast panoply of crappy cars that comprise an unserious
challenge to internal-combustion engine cars and trucks.

The reason the future is not here yet is that the Tesla costs about
$80,000 for a two-seat sportster, and they're projecting about $50,000
for an upcoming 4-door sedan. These are prices that may challenge the
high end of these markets, but not the mainstream. The price is largely
in their high-end battery packs, which are lithium-ion.

Back to the issue of cars versus humans on bikes, we're so adaptable
that we can use the Rube Goldbergian derailer drivetrain, the most
efficient quick-shifting multi-speed drivetrain ever conceived. This
same drivetrain is poorly adapted to the requirements of almost every
other powerplant known to man, and thus is virtually unused outside of
cycling.

Planetary gearboxes, on the other hand, are found all over the place.
For 5 newsgroup points, why do bicycles generally use gearhubs, while
most every other power application puts the gearbox at the other end of
the final drive? I have some ideas, but no decisive answers. As a hint,
there is one class of bicycle where frame-mounted gearboxes are being
experimented with.

--
Ryan Cousineau [email protected] http://www.wiredcola.com/
"My scenarios may give the impression I could be an excellent crook.
Not true - I am a talented lawyer." - Sandy in rec.bicycles.racing
 
On Oct 21, 3:48 am, Ben C <[email protected]> wrote:
> On 2007-10-20, Tim McNamara <[email protected]> wrote:
> > And he's also not necessarily right, either. The human body has a much
> > broader range of efficient functioning than is the case for engines.
> > Mistaking humans for "engines" causes all kinds of conceptual problems
> > and is a practice that should be stopped.

>
> My bike has 18 gears which are good for speeds in the range 0 to 30mph.
> My car has only five for 0 to 110mph.
>
> About 4 of the bike's gears overlap, so there are really 14 gears. This
> still means about one gear for every 2mph increment.
>
> Surely the car engine is much the more flexible?


A cyclist's efficiency varies relatively little with
power output or rpm (=cadence). You can't say the
same for gas car engines. I'm defining efficieny
as power output divided by fuel burnt (=calories burnt)
and that's about 20-25% for most humans in workable
ranges of power and revs.

Car engines, of course, are significantly more efficient
in specific design regimes, which is one reason you'll burn
a lot more gas if you drive a muscle car or Ferrari around
at 15 mph all day vs doing the same in a gas golf cart.
For comparison, you could cycle for several hours
at 10 mph and not even need to eat more than your usual
lunch, although you might be bored spitless.

The reason cars get away with having few gears, working
outside the powerband, and so on, is that they have a
fair amount of excess power. It would be a bigger
consideration if one were driving an early IC engine
without so much power to spare.

Ben
 
>>> [email protected] wrote:
>>>> I just found an interesting article from BERND Rohloff. He discuss
>>>> the importance of the "IDEAL" gear for the engine (human leg). And
>>>> the answer is:
>>>> Small (15%) and constant gear steps over the appropiate overall gear
>>>> ratio! YES!


>> Tim McNamara <[email protected]> wrote:
>>> "YES?" Why "YES!" with such emphasis? Since this is Rohloff's opinion
>>> that happens to support the hub he designed, it is not an independent
>>> verification of anything.
>>> And he's also not necessarily right, either. The human body has a much
>>> broader range of efficient functioning than is the case for engines.
>>> Mistaking humans for "engines" causes all kinds of conceptual problems
>>> and is a practice that should be stopped.


> Ben C <[email protected]> wrote:
>> My bike has 18 gears which are good for speeds in the range 0 to 30mph.
>> My car has only five for 0 to 110mph.
>> About 4 of the bike's gears overlap, so there are really 14 gears. This
>> still means about one gear for every 2mph increment.
>> Surely the car engine is much the more flexible?


Ryan Cousineau wrote:
> Well, as others have mentioned, humans are not internal combustion
> engines, and we share neither the quirks nor the characteristics of them.
>
> When you talk about, for example, usable powerbands, a typical car
> engine might generate usable power from 1000-6000 rpm, which is a "6x"
> range. In terms of actual running range, it probably stalls at 600 rpm
> or so, and maybe it runs to 6600 rpm before the rev limiter kicks in, so
> call it "11x" running range.
>
> That, broadly speaking describes the width of the powerband, though
> usually the term is used to describe the area of the rev range where the
> engine is putting out a high percentage of its maximum power. So a
> racerboy might describe this same theoretical engine as having a 2000
> rpm powerband, from 5200-6200 rpm or some such. It matters not.
>
> The thing that distinguishes humans, in this case, is that they don't
> stall. You and I can generate power at as few rpm as can be imagined,
> and most of us can manage 100 rpm. A few can go rather higher than that.
>
> That's pretty flexible! If you assume a practical 10-120 rpm range (10
> rpm being not inconceivable as an "instantaneous" rev rate shortly after
> a standing start), you're at 12x already. Better than the car!
>
> Of course, humans in good form produce a horsepower or so for short
> periods of time. 50cc scooters put out 6-10 times that power, and cars
> produce hundreds of times that power in some cases, and will do so until
> they run out of gas. For that, we'll put up with the compromise of
> needing a clutch and not having a 0 rpm stall speed.
>
> Right now the future looks very electrical, and EVs motors are the best
> of both worlds (0 rpm stall speeds plus high power). It is only in the
> storage area where EVs let us down, managing to be mostly left
> hopelessly flailing in the face of the cheaply available energy capacity
> of diesel, gas, and a few other hydrocarbons.
>
> However, the future is getting closer: Tesla may actually start putting
> cars in the hands of customers in the next few months, and if you're
> willing to accept restricted ranges and slow charge times, the future
> can be here now. There's a few EV companies that will sell you (as far
> as I can tell) a vast panoply of crappy cars that comprise an unserious
> challenge to internal-combustion engine cars and trucks.
>
> The reason the future is not here yet is that the Tesla costs about
> $80,000 for a two-seat sportster, and they're projecting about $50,000
> for an upcoming 4-door sedan. These are prices that may challenge the
> high end of these markets, but not the mainstream. The price is largely
> in their high-end battery packs, which are lithium-ion.
>
> Back to the issue of cars versus humans on bikes, we're so adaptable
> that we can use the Rube Goldbergian derailer drivetrain, the most
> efficient quick-shifting multi-speed drivetrain ever conceived. This
> same drivetrain is poorly adapted to the requirements of almost every
> other powerplant known to man, and thus is virtually unused outside of
> cycling.
>
> Planetary gearboxes, on the other hand, are found all over the place.
> For 5 newsgroup points, why do bicycles generally use gearhubs, while
> most every other power application puts the gearbox at the other end of
> the final drive? I have some ideas, but no decisive answers. As a hint,
> there is one class of bicycle where frame-mounted gearboxes are being
> experimented with.


Discussed well by Archibald Sharp long long ago. A bicycle is just about
the only common item that's geared up not geared down.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
 
In article <[email protected]>,
A Muzi <[email protected]> wrote:

> Ryan Cousineau wrote:


> >
> > Planetary gearboxes, on the other hand, are found all over the place.
> > For 5 newsgroup points, why do bicycles generally use gearhubs, while
> > most every other power application puts the gearbox at the other end of
> > the final drive? I have some ideas, but no decisive answers. As a hint,
> > there is one class of bicycle where frame-mounted gearboxes are being
> > experimented with.

>
> Discussed well by Archibald Sharp long long ago. A bicycle is just about
> the only common item that's geared up not geared down.


Whoa! I hadn't even thought of that. And it's more right than any answer
I had in mind.

7-league wheels,

--
Ryan Cousineau [email protected] http://www.wiredcola.com/
"My scenarios may give the impression I could be an excellent crook.
Not true - I am a talented lawyer." - Sandy in rec.bicycles.racing
 
In article <[email protected]>,
A Muzi <[email protected]> wrote:

> Ryan Cousineau wrote:
> > Planetary gearboxes, on the other hand, are found all over the
> > place. For 5 newsgroup points, why do bicycles generally use
> > gearhubs, while most every other power application puts the gearbox
> > at the other end of the final drive? I have some ideas, but no
> > decisive answers. As a hint, there is one class of bicycle where
> > frame-mounted gearboxes are being experimented with.

>
> Discussed well by Archibald Sharp long long ago. A bicycle is just
> about the only common item that's geared up not geared down.


You know, I'd never thought about that. 1:1 gearing is normally the low
end of cycling gearing, whereas it's near the top end of car and truck
gearing.
 
Tim McNamara wrote:
> In article <[email protected]>,
> A Muzi <[email protected]> wrote:
>
>> Ryan Cousineau wrote:
>>> Planetary gearboxes, on the other hand, are found all over the
>>> place. For 5 newsgroup points, why do bicycles generally use
>>> gearhubs, while most every other power application puts the gearbox
>>> at the other end of the final drive? I have some ideas, but no
>>> decisive answers. As a hint, there is one class of bicycle where
>>> frame-mounted gearboxes are being experimented with.

>> Discussed well by Archibald Sharp long long ago. A bicycle is just
>> about the only common item that's geared up not geared down.

>
> You know, I'd never thought about that. 1:1 gearing is normally the low
> end of cycling gearing, whereas it's near the top end of car and truck
> gearing.


For road bicycles. Most ATBs have somewhere from a 24/32 to 22/34 low gear.

--
Tom Sherman - Holstein-Friesland Bovinia
Beer - It's not just for breakfast anymore!
 

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