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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 05-03-05, 11:41 PM   #1
BlastRadius
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Since your power does not go directly into the front wheel does it help acceleration as much, if any, if the front wheel is light? Just wondering since I just re-laced my front wheel with longer spokes using 3-cross instead of radial lacing. (I know the actual difference is just a few grams, but I'm curious anyway.)

Oh and I guess it's sort of fixie related because I put my spoke cards in the front wheel.
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Old 05-03-05, 11:52 PM   #2
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I'm not a scientist but I would guess that the front wheel is just as important as the back wheel. Considering both wheels spin at exactly the same speed this would mean that both wheels would affect acceleration equally.

This thread could get ugly

CHEERS.

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Old 05-04-05, 04:00 AM   #3
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It spins. You have to accelerate it, just not directly. It still has rotational inertia, and yeah, a light front wheel and a light front tyre really improve your acceleration, deceleration and jump. It counts.
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Old 05-04-05, 06:26 AM   #4
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"Considering both wheels spin at exactly the same speed this would mean that both wheels would affect acceleration equally."

assuming, of course, you have identically sized/inflated tires and ride in a straight line.
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Old 05-04-05, 06:47 AM   #5
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Originally Posted by stevo
"Considering both wheels spin at exactly the same speed this would mean that both wheels would affect acceleration equally."

assuming, of course, you have identically sized/inflated tires and ride in a straight line.
yeah, well your pennyfarthing is a whole different kettle of fish.
in all other respects though, it was a pretty fair assumption dont you think?
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Old 05-04-05, 06:54 AM   #6
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oh, right, I forgot about you moderninsts and your 'safety-bikes'.

yes, i believe your assumption is fair.
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Old 05-04-05, 06:55 AM   #7
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Relative to the road surface the bottom of your wheel is stationary at all times.
The axle is traveling at the speed indicated on your bike computer and the top of your wheel is traveling at twice the speed indicated on your computer.

That ought to cook your noodle

Enjoy
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Old 05-04-05, 07:00 AM   #8
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Originally Posted by stevo
oh, right, I forgot about you moderninsts and your 'safety-bikes'.

yes, i believe your assumption is fair.
hehe.
i tell you. once you've tried pneumatic tyres you'll never go back. they're a revolution you know.
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Old 05-04-05, 07:07 AM   #9
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Since your power does not go directly into the front wheel does it help acceleration as much, if any, if the front wheel is light? Just wondering since I just re-laced my front wheel with longer spokes using 3-cross instead of radial lacing. (I know the actual difference is just a few grams, but I'm curious anyway.)

Oh and I guess it's sort of fixie related because I put my spoke cards in the front wheel.
Changing spoke length would be negligible.

If you change to a lighter rim, tire, tube and Al nipples, the change could be huge. The area of the bike where weight savings vs. money spent (to achieve greater acceleration) gives you the best value is the outer wheel area. Of course the down side of a light wheel is durability and reliability.

I do not know what a "spoke card" is? Is it a card that rubs against the spokes to create that clicking noise? If that is the case, that would be a significant source of friction and would slow you down. The friction from the spoke card would be greater, by far, than having a slightly heavier wheel from longer spokes. It's like having a brake pad rub constantly.
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Old 05-04-05, 07:10 AM   #10
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Quote:
Originally Posted by powers2b
Relative to the road surface the bottom of your wheel is stationary at all times.
The axle is traveling at the speed indicated on your bike computer and the top of your wheel is traveling at twice the speed indicated on your computer.

That ought to cook your noodle

Enjoy
noodles nearly done.

i believe that only the centre of the axle will travel at the speed indicated on the computer.
and:
the top of the wheel only travels 2* the speed of the computer when the bottom of the wheel is not stationary relative to the road surface... is that right, or is it time for me to go to bed??


marty
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Old 05-04-05, 07:34 AM   #11
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"The axle is traveling at the speed indicated on your bike computer"

Since I dont have a bike computer, does that mean my axle is not travelling? I guess I'm not anyway since the the bottom of my wheel is stationary.

but seriously, if someone changes the rolling circumf. setting in the computer to a larger value, would that make him go faster?
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Old 05-04-05, 07:37 AM   #12
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Quote:
Originally Posted by Martyr
noodles nearly done.

i believe that only the centre of the axle will travel at the speed indicated on the computer.
and:
the top of the wheel only travels 2* the speed of the computer when the bottom of the wheel is not stationary relative to the road surface... is that right, or is it time for me to go to bed??


marty
Since the axle is not spinning the whole thing and everythig it is attached to (you and the bike) travels at the speed indicated on the computer.
When the bottom of the wheel is 'not' stationary relative to the road surface you are skidding.

nightey night

Enjoy
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Old 05-04-05, 07:37 AM   #13
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Quote:
Originally Posted by Martyr
i believe that only the centre of the axle will travel at the speed indicated on the computer.
unless you have some different kind of hub, the axle (which might more properly be called a spindle) does not rotate; hence the entire axle travels at the same speed. on a flat surface, in a straight line of course.

following what captsven said, spokes would contribute very little to rotational inertia compared with rim/tire/nipples; that is, the stuff furthest from the center of rotation. spokes contribute to drag, although i don't know if there's a difference between radial versus 3-cross in this regard.

just curious, blasty, what made you decide to switch from radial to 3-cross?
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Old 05-04-05, 08:15 AM   #14
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Yes, there's rotational inertia to the front wheel. It's a rotating system so by definition it has rotational inertia. The question in my mind is, is the energy necessary to change its rotation separate from the energy necessary to change its lateral motion?

I suppose it is given that a bike on the stand still requires energy bleed off (through braking or some other friction) to stop the wheel. In the usual case, I suspect that the rotational inertia would be hugely dominated by the intertia of the entire bike-rider system.

Last edited by bostontrevor; 05-04-05 at 08:33 AM.
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Old 05-04-05, 08:16 AM   #15
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Quote:
Originally Posted by cicadashell
unless you have some different kind of hub, the axle (which might more properly be called a spindle) does not rotate; hence the entire axle travels at the same speed. on a flat surface, in a straight line of course.

following what captsven said, spokes would contribute very little to rotational inertia compared with rim/tire/nipples; that is, the stuff furthest from the center of rotation. spokes contribute to drag, although i don't know if there's a difference between radial versus 3-cross in this regard.

just curious, blasty, what made you decide to switch from radial to 3-cross?
For some reason, the difference between the front and rear lacings didn't settle well with me. I bought the wheels used so I didn't have much say to begin with. It did give me a chance to try my hand a wheel building. Now there isn't anything on a bike I can't fix myself.

Regarding the idea of weight counting more at the rim, yes I do agree that makes a difference in the rear wheel where your leg energy is directly accelerating that rotational weight. However, wouldn't the front wheel be more like "static"(?) weight much like a handlebar or saddle. Example, taking 200 grams off the rear wheel makes a noticeable contribution to the feeling of quick acceleration versus taking 200 grams off the saddle (and I conjecture, the front wheel).
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Old 05-04-05, 08:19 AM   #16
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Quote:
Originally Posted by bostontrevor
Yes, there's rotational inertia to the front wheel. It's a rotating system so by definition it has rotational inertia. The question in my mind is, is the energy necessary to change it's rotation separate from the energy necessary to change it's lateral motion?

I suppose it is given that a bike on the stand still requires energy bleed off (through braking or some other friction) to stop the wheel. In the usual case, I suspect that the rotational inertia would be hugely dominated by the intertia of the entire bike-rider system.
Ahh, good point.
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Old 05-04-05, 08:21 AM   #17
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my axle stays stationary, and the hub rotates around it... i don't know what sort of wheels you weirdos are using.
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Old 05-04-05, 03:42 PM   #18
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Quote:
Originally Posted by powers2b
Since the axle is not spinning the whole thing and everythig it is attached to (you and the bike) travels at the speed indicated on the computer.
When the bottom of the wheel is 'not' stationary relative to the road surface you are skidding.

nightey night

Enjoy
like half cooked noodles: DOH!

i have had my sleep, and realise that that was probably the stupidest thought i have had for a while.

cheers


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