does the computer magnet slow you down?

wle said:

this is a real nit picky puzzle, but does the computer magnet slow you down?

you know, it passes a reed switch every wheel revolution, causing it to open and close, sending
the pulse to the computer, telling it 'the wheel has turned once'.

question 2:

if the reed switch couldn;t move for some reason, say it;s stuck, would that change the wheel
drag any?

Yes, there would be slightly less drag if the switch were stuck. When the magnet comes around it
is attracted to the movable part of the switch. So you get a tiny boost before it reaches the
switch and then are held back a bit after it passes the switch. If the switch can move then it's
closer to the magnet after it closes and the retarding force is greater than it would be if the
switch were immobile.

Good luck trying to measure this effect in the real world.

Peter said:

the magnet comes around it is attracted to the movable part of the switch. So you get a tiny boost
before it reaches the switch and then are held back a bit after it passes the switch. If the
switch can move

Good luck trying to measure this effect in the real world.

Hmm..so, if this effect were measurable, then it would be wise to try to put the sensor and magnet
closer to the hub than the rim.

My concern, since we're on the subject of magnets and sensor and wheels, is wheel balance.
Unlike cars, bicycle wheels aren't balanced at all; we stick the tire on, and it's good enough.
However, with wheels, tubes, and tires getting lighter all the time, and with the high speeds
possible on a modern road bike with a good hill, I have to believe that there will be balance
issues sooner or later.

This would be, of course, exacerbated by a not-well-placed magnet. I've observed that mechanics
always seem to install the magnet on the opposite side of the wheel from where the tire valve is;
same for the reflector in the wheel. Is this strategy for balance? I have always figured so, and
have the same habit.

--
Rick Onanian

You forget that if the relay sticks, that the magnet will evenually just pull the whole pickup
assembly into the wheel. This can cause catastrophic wheel failure as strength of the composite
pickup greatly exceeds the strength of the spokes. 🙂

Peter said:

wle said:

this is a real nit picky puzzle, but does the computer magnet slow you down?

you know, it passes a reed switch every wheel revolution, causing it to open and close, sending
the pulse to the computer, telling it 'the wheel has turned once'.

question 2:

if the reed switch couldn;t move for some reason, say it;s stuck, would that change the wheel
drag any?

Yes, there would be slightly less drag if the switch were stuck. When the magnet comes around
it is attracted to the movable part of the switch. So you get a tiny boost before it reaches
the switch and then are held back a bit after it passes the switch. If the switch can move then
it's closer

to

Quoted message said:

the magnet after it closes and the retarding force is greater than it

would

Quoted message said:

be if the switch were immobile.

Good luck trying to measure this effect in the real world.

--
Mark Wolfe wolfenet.orgwolfenet.orgOpen ↗ gpg fingerprint = 42B6 EFEB 5414 AA18 01B7 64AC EF46 F7E6 82F6
8C71 The sky already fell. Now what? -- Steven Wright

My commuter bike has wheel reflectors. I was surprised to find that I could feel the out-of-balance
on fast descents. At first, I thought there was a real problem since the vibration was so strong. It
was unnerving enough that I tried moving the reflector opposite the valve... no effect. So I put 2
reflectors on each wheel, opposing. That fixed it.

Obviously, wheel reflectors weigh a lot more than a computer magnet.

Ride on, maintain balance, Don

"Rick Onanian" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Peter said:

the magnet comes around it is attracted to the movable part of the switch. So you get a tiny
boost before it reaches the switch and then are held back a bit after it passes the switch. If
the switch can move

Good luck trying to measure this effect in the real world.

Hmm..so, if this effect were measurable, then it would be wise to try to put the sensor and magnet
closer to the hub than the rim.

My concern, since we're on the subject of magnets and sensor and wheels, is wheel balance. Unlike
cars, bicycle wheels aren't balanced at all; we stick the tire on, and it's good enough. However,
with wheels, tubes, and tires getting lighter all the time, and with the high speeds possible on
a modern road bike with a good hill, I have to believe that there will be balance issues sooner
or later.

This would be, of course, exacerbated by a not-well-placed magnet. I've observed that mechanics
always seem to install the magnet on the opposite side of the wheel from where the tire valve is;
same for the reflector in the wheel. Is this strategy for balance? I have always figured so, and
have the same habit.

--
Rick Onanian

Rick Onanian <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Peter said:

the magnet comes around it is attracted to the movable part of the switch. So you get a tiny
boost before it reaches the switch and then are held back a bit after it passes the switch. If
the switch can move

Good luck trying to measure this effect in the real world.

Hmm..so, if this effect were measurable, then it would be wise to try to put the sensor and magnet
closer to the hub than the rim.

My concern, since we're on the subject of magnets and sensor and wheels, is wheel balance. Unlike
cars, bicycle wheels aren't balanced at all; we stick the tire on, and it's good enough. However,
with wheels, tubes, and tires getting lighter all the time, and with the high speeds possible on
a modern road bike with a good hill, I have to believe that there will be balance issues sooner
or later.

This is not true. Ambrosio has made a tiny weight, to be placed at the valve to balance rims joined
"the old way", which made them heavy opposite the hole for the valve. I use them myself on my Fir
Quasar rims, and they really work fine. Ambrosio is actually also making a rim called Balance;
ambrosiospa.comcerchi corsa.htmOpen ↗

Quoted message said:

This would be, of course, exacerbated by a not-well-placed magnet. I've observed that mechanics
always seem to install the magnet on the opposite side of the wheel from where the tire valve is;
same for the reflector in the wheel. Is this strategy for balance? I have always figured so, and
have the same habit.

If you are worried about the balance of your wheel, try holding it in your hands at the hub and spin
it quickly - if it is not balanced you will notice.

The drag is always from work done moving the switch or whatever; identify the work, divide by
distance travelled, and that's the drag.
--
Ron Hardin [email hidden]

On the internet, nobody knows you're a jerk.

"wle" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

this is a real nit picky puzzle, but does the computer magnet slow you down?

Yes, which is why I stopped using computers on my downhill mountain bikes.

Now, does anyone know how many refrigerator magnets it takes to stop the compressor?

Mike ;^P

Peter <[email hidden]> wrote in message news:<sns7b.406179$Ho3.61721@sccrnsc03>...

Quoted message said:

wle wrote:

Quoted message said:

Yes, there would be slightly less drag if the switch were stuck. When the magnet comes around it
is attracted to the movable part of the switch. So you get a tiny boost before it reaches the
switch and then are held back a bit after it passes the switch. If the switch can move then it's
closer to the magnet after it closes and the retarding force is greater than it would be if the
switch were immobile.

that is pretty clear. i was having trouble visualizing that.

Quoted message said:

Good luck trying to measure this effect in the real world.

ha ha! i know it;s ridiculous.

wle.

Michael Dart' may have said:

"wle" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

this is a real nit picky puzzle, but does the computer magnet slow you down?

Yes, which is why I stopped using computers on my downhill mountain bikes.

The aerodynamic drag from the lump on the spoke is almost certainly higher than the loss from
the magnet/switch interaction. (And no, I do not think that this is a good reason to make an
aero magnet.)

I'm told that the real reason not to use a comp on a downhill bike is that the wire is hard to get
out from between your teeth. (Of course, there's always a wireless...)

Quoted message said:

Now, does anyone know how many refrigerator magnets it takes to stop the compressor?

An appropriate answer:

A very small one in the suction line should do it.

--
My email address is antispammed; pull WEEDS if replying via e-mail. Yes, I have a killfile. If I
don't respond to something, it's also possible that I'm busy.

O. Simonsen said:

If you are worried about the balance of your wheel, try holding it in your hands at the hub and
spin it quickly - if it is not balanced you will notice.

I doubt I can spin it as fast as it will spin at 35-40 mph, which is when I'd be concerned
about balance.

Anyway, it's never effectively been an issue for me, only academically.

--
Rick Onanian

Peter <[email hidden]> wrote in message news:<sns7b.406179$Ho3.61721@sccrnsc03>...

Quoted message said:

wle said:

this is a real nit picky puzzle, but does the computer magnet slow you down?

you know, it passes a reed switch every wheel revolution, causing it to open and close, sending
the pulse to the computer, telling it 'the wheel has turned once'.

question 2:

if the reed switch couldn;t move for some reason, say it;s stuck, would that change the wheel
drag any?

Yes, there would be slightly less drag if the switch were stuck. When the magnet comes around it
is attracted to the movable part of the switch. So you get a tiny boost before it reaches the
switch and then are held back a bit after it passes the switch. If the switch can move then it's
closer to the magnet after it closes and the retarding force is greater than it would be if the
switch were immobile.

Good luck trying to measure this effect in the real world.

In order to be completely scrupulous in your calculations, you would have to account not only
for the reed switch, but for the much larger interaction with the fork blade (assuming the blade
is steel).

In theory, a reactive force would exist, but of such a small magnitude as to render it meaningless
in the real world. The effect of the magnet is probably close to the drag imparted by having your
jersey zipper 1.5 inches lower than usual......

O. Simonsen said:

Quoted message said:

Hmm... so, if this effect were measurable, then it would be wise to try to put the sensor and
magnet closer to the hub than the rim.

Quoted message said:

Quoted message said:

My concern, since we're on the subject of magnets and sensor and wheels, is wheel balance. Unlike
cars, bicycle wheels aren't balanced at all; we stick the tire on, and it's good enough. However,
with wheels, tubes, and tires getting lighter all the time, and with the high speeds possible on
a modern road bike with a good hill, I have to believe that there will be balance issues sooner
or later.

Quoted message said:

This is not true. Ambrosio has made a tiny weight, to be placed at the valve to balance rims
joined "the old way", which made them heavy opposite the hole for the valve. I use them myself on
my Fir Quasar rims, and they really work fine. Ambrosio is actually also making a rim called
Balance; ambrosiospa.comcerchi corsa.htmOpen ↗

Why is there any concern with wheel balance? Valve stems are a heavy point on the circumference
as are rim splices that are partially balanced by the stem that lies opposite. No one has
determined any ill effects of this unbalance, especially at the speeds bicycles travel. Descents
at 100km/h have been made with no perceptible effects from wheel imbalance. Ambrosio is pulling
your leg, so to speak.

Quoted message said:

Quoted message said:

This would be, of course, exacerbated by a not-well-placed magnet. I've observed that mechanics
always seem to install the magnet on the opposite side of the wheel from where the tire valve is;
same for the reflector in the wheel. Is this strategy for balance? I have always figured so, and
have the same habit.

Quoted message said:

If you are worried about the balance of your wheel, try holding it in your hands at the hub and
spin it quickly - if it is not balanced you will notice.

The last time this came up, I put about a dozen wraps of 3mm lead wire around a spoke at the rim to
test the effects. At that time the claim was that imbalance causes shimmy. There was no difference
on shimmy with and without the weight, nor when the wheel was ideally balanced. The bicycle shimmied
and had the same severity at its usual resonant speed while coasting no-hands. The presence of
imbalance had no perceptible effect on the bicycle coasting 56 km/h.

Jobst Brandt [email hidden]

Quoted message said:

Why is there any concern with wheel balance? Valve stems are a heavy

My concern was a matter of curiosity. I had noticed that most bikes have the wheel reflectors
and computer magnets opposite the valve stem, and wondered if that was for balance; and I had
also noticed that my wheels have been smooth to my maximum achieved speed, around 40 mph (64.36
kph) to date.

Quoted message said:

Jobst Brandt [email hidden]

--
Rick Onanian

(wle) said:

Peter <[email hidden]> wrote in message news:<sns7b.406179$Ho3.61721@sccrnsc03>...

Quoted message said:

wle wrote:

Quoted message said:

Yes, there would be slightly less drag if the switch were stuck. When the magnet comes around it
is attracted to the movable part of the switch. So you get a tiny boost before it reaches the
switch and then are held back a bit after it passes the switch. If the switch can move then it's
closer to the magnet after it closes and the retarding force is greater than it would be if the
switch were immobile.

that is pretty clear. i was having trouble visualizing that.

Quoted message said:

Good luck trying to measure this effect in the real world.

ha ha! i know it;s ridiculous.

wle.

Want to go faster? Reverse polarity of the magnet and connect a flux gate capacitor.

Jim

(wle) said:

if the reed switch couldn;t move for some reason, say it;s stuck, would that change the wheel
drag any?

Yes. Actually, the presence of the magnet has a significant, and linear, effect on your speed. Coast
down a hill with a constant slope and note your average speed. Now remove the magnet and repeat.
Note that your speed has dropped to zero. To confirm the hypothesis, put two magnets on the wheel,
180 degrees apart. Repeat the coast down test. Now your speed has doubled.

Joe Riel

I've hit 50-55mph without any ill effects from unbalanced wheels. 32 hole open pros, DA hubs, steel
frame/fork. Hills are great. 🙂

Rick Onanian said:

Quoted message said:

Why is there any concern with wheel balance? Valve stems are a heavy

My concern was a matter of curiosity. I had noticed that most bikes have the wheel reflectors and
computer magnets opposite the valve stem, and wondered if that was for balance; and I had also
noticed that my wheels have been smooth to my maximum achieved speed, around 40 mph (64.36 kph)
to date.

--
Mark Wolfe wolfenet.orgwolfenet.orgOpen ↗ gpg fingerprint = 42B6 EFEB 5414 AA18 01B7 64AC EF46 F7E6 82F6
8C71 __o | Arguing with an engineer is like mud wrestling with a pig... You `\(, | soon find out the
pig likes it! (_)/(_)|

Quoted message said:

does the computer magnet slow you down?

buy three!!! it slows you down if they're swallowed and duh i found the steel
nipples!!!!!!!!!!!!!!!!!! yahha!!

(g.daniels) may have said:

Quoted message said:

does the computer magnet slow you down?

buy three!!! it slows you down if they're swallowed and duh i found the steel
nipples!!!!!!!!!!!!!!!!!! yahha!!

To really mess with somebody's head, add a second magnet to their front wheel.

--
My email address is antispammed; pull WEEDS if replying via e-mail. Yes, I have a killfile. If I
don't respond to something, it's also possible that I'm busy.

Whether the switch opened or not, the effect on the magnetic field as it passed would probably be
unmeasurable as far as the wheel is concerned.

Why am I bothering to answer this?

May you have the wind at your back. And a really low gear for the hills! Chris

Chris'Z Corner "The Website for the Common Bicyclist": geocities.comczcornerOpen ↗