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program to compute gears, with table



 
 
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  #91  
Old September 12th 17, 10:45 PM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,035
Default program to compute gears, with table

Radey Shouman wrote:

the much deeper instruction pipelines


"deeper instruction pipelines", is that like
the many transformations of graphical data
before it appears on the screen, or a shell
parsing of a text string with UNIX tools,
i.e. done_value=$(a | b | ... | n) ? If so, are
the extra steps because of new capabilities the
CPU has that wasn't there before?

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  #92  
Old September 12th 17, 11:44 PM posted to rec.bicycles.tech
[email protected]
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Default program to compute gears, with table

On Tuesday, September 12, 2017 at 8:43:49 AM UTC-7, Emanuel Berg wrote:
John B. wrote:

Because, as Andrew told you, it will fit.
On the other hand, as Andrew told you, if a 6
speed it won't shift well.


I think it would make more sense if Shimano put
just one digit, or one set of digits, on their
boxes, which refered both "fits" and "shifts
well".

It is the intuition as well.

For example if I had a 6 casette from Shimano,
then put on a 6/7/8 chain, and it didn't shift
well, the thought wouldn't hit me the
chain/casette combination could be the problem,
but I suppose one will have to get used to
disinformation even from the most
iconic manufacturers.


Well, that's a hard subject isn't it? As a friction shifting chain on a freewheels it shifts almost perfectly as friction shifters do. The problem is with Brifters.
  #93  
Old September 12th 17, 11:48 PM posted to rec.bicycles.tech
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Default program to compute gears, with table

On Tuesday, September 12, 2017 at 11:58:38 AM UTC-7, Frank Krygowski wrote:
On Tuesday, September 12, 2017 at 3:53:29 AM UTC-4, John B. wrote:
On Tue, 12 Sep 2017 06:00:09 +0200, Emanuel Berg
wrote:

Sir Ridesalot wrote:

Many times he asks a question then disagrees
with what those experts like Andrew who know
the RIGHT answer tell him.

So let's hear it, why do Shimano put such
obvious disinformation on their product boxes?


Because, as Andrew told you, it will fit. On the other hand, as Andrew
told you, if a 6 speed it won't shift well.

I might add that I have used a 10 speed chain with a 9 speed cassette
and a 9 speed chain with a 10 speed cassette, and they worked to my
satisfaction although Shimano certainly do not state it will work on
the box.


Didn't Shimano advertise derailleurs as being "9 Speed" when they were precisely
the same geometry as their previous derailleurs?


I'm not sure of that Frank. I think that the angles were improved over time.. I know that I have a Campy long arm rear derailleur that doesn't shift as well as a short arm newer model. The way the arms rotate and drop are much better on the short arm. That seems to be my experience with the Shimano stuff as well.
  #94  
Old September 12th 17, 11:58 PM posted to rec.bicycles.tech
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Default program to compute gears, with table

On Tuesday, September 12, 2017 at 1:19:25 PM UTC-7, Radey Shouman wrote:
John B. writes:

On Mon, 11 Sep 2017 08:23:48 -0700 (PDT), wrote:


[ ... ]

Yesterday I rode on a 35 mile ride. On the way out into a headwind I
averaged a little less than 14 mph. I had a cup of coffee while in
the city square the worst band I ever heard was making awful
noises. When I was in a band if we had played that badly on our
first try in a rehearsal we would have quit.

On the way back the wind had reversed and I had a hard time
maintaining 12 mph for most of the way. By the time I got home I was
exhausted. Do you think that I could improve my performance with an
11 or 12 speed?

I know my limits and it isn't playing as if I was Chris Froome.


Something I've always wondered about is how in the world can I ride an
out and back course and have a head wind both ways :-(


With some reasonable assumptions I think you can show that this is
actually true, in a sense. Suppose for example the wind is blowing at
right angles to your (perfectly straight) direction, and that it happens
to be blowing at exactly your ground speed, v.

The apparent wind will be at 45 degrees your heading, at a velocity of
sqrt(v^2 + v^2) = sqrt(2)*v.

For turbulent flow, the drag force is approximately proportional to the
square of the wind speed, so the drag force will be twice the drag force
you would see in still air, F. (At this point we have assumed a
cylindrical bike & rider, meaning that the coefficient of drag is the
same from the front as the side, since drag from the side is normally
greater, this is conservative).

Fortunately the drag force acts at 45 degrees to your course, so the
drag component that holds you back is
cos(45 deg)*F = (2/sqrt(2))*F
= sqrt(2)*F
~= 1.414 F

This is as true on the way out as it is on the way back, hence you
really do have an effective head wind both ways.


Radey - I'm an engineer and understand mathematics. I also understand that on most of the courses I ride I get a complete 180 degree swing in the direction of the winds due to prevailing wind pattern change as the temperature between the coast and the valley changes from the morning to afternoon. I was simply expressing frustration that I happen to live in a place where it always appears to oppose me whereas others living in the valley can have a tail wind in both directions.

It was really nice on a Century down near Gilroy when the end 20 miles was down a hard tailwind and I could maintain 28 mph.
  #95  
Old September 13th 17, 01:13 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,035
Default program to compute gears, with table

Here is what Wikipedia says: [1]

With derailleur equipped bicycles, the
external width of the chain also matters,
because chains must not be too wide for the
cogset or they will rub on the next larger
sprocket, or too narrow that they might
fall between two sprockets.

Chains can also be identified by the number
of rear sprockets they can support,
anywhere from 3 to 11, and the list below
enables measuring a chain of unknown origin
to determine its suitability.

* 6 speed – 7.8 mm (5/16")
* 7 speed – 7.3 mm (9/32")
* 8 speed – 7.1 mm (9/32")
* 9 speed – 6.6 to 6.8 mm (1/4 to 9/32")
* 10 speed – 6.2 mm (1/4") (Shimano, Campagnolo)
* 10 speed (Narrow) – 5.88 mm (7/32") (Campagnolo, KMC)
* 10 speed (Narrow, Direction) – 5.88 mm (7/32") (Shimano CN-5700, CN-6700, CN-7900)
* 11 speed – 5.5 mm (7/32") (Campagnolo, KMC, Shimano CN-9000)

Interesting that the 7 and 8 are the same in
inches, but not in mm.

$ units -t '7.3 mm' '1|32 in'
9.1968504

$ units -t '7.1 mm' '1|32 in'
8.9448819

[1] https://en.wikipedia.org/w/index.php...&printable=yes

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  #96  
Old September 13th 17, 02:06 AM posted to rec.bicycles.tech
John B.[_3_]
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Posts: 5,697
Default program to compute gears, with table

On Tue, 12 Sep 2017 17:43:43 +0200, Emanuel Berg
wrote:

John B. wrote:

Because, as Andrew told you, it will fit.
On the other hand, as Andrew told you, if a 6
speed it won't shift well.


I think it would make more sense if Shimano put
just one digit, or one set of digits, on their
boxes, which refered both "fits" and "shifts
well".

Well, apparently it makes sense to Shimano...

It is the intuition as well.

For example if I had a 6 casette from Shimano,
then put on a 6/7/8 chain, and it didn't shift
well, the thought wouldn't hit me the
chain/casette combination could be the problem,
but I suppose one will have to get used to
disinformation even from the most
iconic manufacturers.


There is no disinformation at all. The chain will fit 6,7,8 speed
cassettes. And that is just what they told you.
--
Cheers,

John B.

  #97  
Old September 13th 17, 02:14 AM posted to rec.bicycles.tech
John B.[_3_]
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Posts: 5,697
Default program to compute gears, with table

On Tue, 12 Sep 2017 11:58:34 -0700 (PDT), Frank Krygowski
wrote:

On Tuesday, September 12, 2017 at 3:53:29 AM UTC-4, John B. wrote:
On Tue, 12 Sep 2017 06:00:09 +0200, Emanuel Berg
wrote:

Sir Ridesalot wrote:

Many times he asks a question then disagrees
with what those experts like Andrew who know
the RIGHT answer tell him.

So let's hear it, why do Shimano put such
obvious disinformation on their product boxes?


Because, as Andrew told you, it will fit. On the other hand, as Andrew
told you, if a 6 speed it won't shift well.

I might add that I have used a 10 speed chain with a 9 speed cassette
and a 9 speed chain with a 10 speed cassette, and they worked to my
satisfaction although Shimano certainly do not state it will work on
the box.


Didn't Shimano advertise derailleurs as being "9 Speed" when they were precisely
the same geometry as their previous derailleurs?

- Frank Krygowski


I'm not sure about that. I suspect that the "pull distance" may be a
bit difference if the derailer is designed to work in an indexed
shifter system.

But as far as reaching the other side of the cassette" I've used a 7
speed derailer to shift a 9 speed cassette. Am old Shimano "600" I
believe it was. I replaced it with a more modern derailer as I thought
the "new one" looked nicer.
--
Cheers,

John B.

  #98  
Old September 13th 17, 02:25 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default program to compute gears, with table

On Tue, 12 Sep 2017 16:19:21 -0400, Radey Shouman
wrote:

John B. writes:

On Mon, 11 Sep 2017 08:23:48 -0700 (PDT), wrote:


[ ... ]

Yesterday I rode on a 35 mile ride. On the way out into a headwind I
averaged a little less than 14 mph. I had a cup of coffee while in
the city square the worst band I ever heard was making awful
noises. When I was in a band if we had played that badly on our
first try in a rehearsal we would have quit.

On the way back the wind had reversed and I had a hard time
maintaining 12 mph for most of the way. By the time I got home I was
exhausted. Do you think that I could improve my performance with an
11 or 12 speed?

I know my limits and it isn't playing as if I was Chris Froome.


Something I've always wondered about is how in the world can I ride an
out and back course and have a head wind both ways :-(


With some reasonable assumptions I think you can show that this is
actually true, in a sense. Suppose for example the wind is blowing at
right angles to your (perfectly straight) direction, and that it happens
to be blowing at exactly your ground speed, v.

The apparent wind will be at 45 degrees your heading, at a velocity of
sqrt(v^2 + v^2) = sqrt(2)*v.

For turbulent flow, the drag force is approximately proportional to the
square of the wind speed, so the drag force will be twice the drag force
you would see in still air, F. (At this point we have assumed a
cylindrical bike & rider, meaning that the coefficient of drag is the
same from the front as the side, since drag from the side is normally
greater, this is conservative).

Fortunately the drag force acts at 45 degrees to your course, so the
drag component that holds you back is
cos(45 deg)*F = (2/sqrt(2))*F
= sqrt(2)*F
~= 1.414 F

This is as true on the way out as it is on the way back, hence you
really do have an effective head wind both ways.


I was thinking of days when I ride what I call my short route. It is a
square loop in the city on which the two longer legs are essentially
due north and due south. I set out and on the south leg the wind was
directly in my face. then the "cross wind" leg, about 1 km and
protected by tall buildings and then the north bound leg. Again wind
directly in my face. There are traffic lights on both the north and
south legs and the wind doesn't stop blowing when I stopped at a red
light :-)

--
Cheers,

John B.

  #99  
Old September 13th 17, 02:37 AM posted to rec.bicycles.tech
John B.[_3_]
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Posts: 5,697
Default program to compute gears, with table

On Tue, 12 Sep 2017 16:30:42 -0400, Radey Shouman
wrote:

John B. writes:

On Tue, 12 Sep 2017 06:06:56 +0200, Emanuel Berg
wrote:

John B. wrote:

That isn't true at all. I have definitely
improved the speed of a C program by using an
assembler language sub routines and even had
two C compilers that would compile the same
program into two different sizes that
performed the same "test" program at two
different speeds.

Obviously two different programs will be of
different sizes and run at different speeds.


But that wasn't what I said at all. As I said the same code compiled
on two different compiler resulted in both a different size compiled
application and, as well, a speed difference when running.

With compilers to do optimization, and with
much increased hardware to make optimization
unnecessary to begin with, there is close to
zero gain re-writing C into assembler, and its


Except when it does make a difference.

an undertaking that isn't proportional to that
gain. So it is rather done when there is a need
to manipulate hardware directly or in ways
which the high-level language isn't suited for.


I'm not sure that is correct in all cases although of course modern
computers run at speeds that make the slower software appear to be
satisfactory. But I did a search on the question "is modern software
written in assembler" and the first hit replied:

"Probably more than most people think, especially in the
microcontroller field. I write in assembler when it's appropriate,
which for the kind of work I do is most of the time


I write in assembler every day, not on any rational basis, but because
that's how my boss did it back in the day.

The big difference between new processors and old, from my point of
view, is the much deeper instruction pipelines. In order to get the
most from these machines one should write in the least straightforward
way possible, doing a little of this, then a little of that, so that
there is as long a time as possible between setting some register's
value and using it. Compilers are good at this, human beings not so
much, especially when the code has to be debugged and modified at some
time in the unknowable future.

On the other hand, in assembler one may use the low level processor
behavior to make sure things are done in an efficient way -- for example
carry and overflow conditions are straightforwardly but non-portably
checked. In C, if you want to make sure the compiler does what you
think it should you have to check the generated assembly, and possibly
contort your code to make your intention "clear".


Ultimately I disassembled the two test programs from the two different
C compilers and found that the difference between the two was that the
Microsoft compiler saved the state, all the registers, etc., then
called the "sub routine" then recovered the state, all the registers,
etc., and went on to the next step. A sort of bullet proofing I guess
you'd call it. The other compiler apparently figured that the
programmer knew what he was doing and if you wrote "write("Good
Morning\n");" it just went ahead and did it.
--
Cheers,

John B.

  #100  
Old September 13th 17, 03:02 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,035
Default program to compute gears, with table

John B. wrote:

There is no disinformation at all. The chain
will fit 6,7,8 speed cassettes. And that is
just what they told you.


I can't speak for anyone else, but I'm
interested in equipment that works and works
well, and if it doesn't, I don't care if it
fits or not.

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