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On Nov 6, 11:32 pm, jim beam <[email protected]> wrote:
> [email protected] wrote:
> > On Nov 4, 12:23 pm, jim beam <[email protected]> wrote:
> >> [email protected] wrote:
> >>> On Nov 3, 7:27 pm, jim beam <[email protected]> wrote:
> >>>> [email protected] wrote:
> >>>>> On Nov 2, 9:18 pm, jim beam <[email protected]> wrote:
> >>>>>> [email protected] wrote:
> >>>>>>> On Nov 2, 12:53 am, jim beam <[email protected]> wrote:
> >>>>>>>> _ wrote:
> >>>>>>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
> >>>>>>>>>>>> What should I be measuring?
> >>>>>>>>>> "jim beam" <[email protected]> a ?crit:
> >>>>>>>>>>> distance between the front tips of the brake pads with the caliper
> >>>>>>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
> >>>>>>>>>>> open, the front tips are further apart than the rears. when closed,
> >>>>>>>>>>> the front tips are closer than the rears. [front caliper]
> >>>>>>>>>> I'm using the moulding seam of the brake block at the point it touches the
> >>>>>>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
> >>>>>>>>>> of a convenient moulding mark) trying to pick a consistent point on the
> >>>>>>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
> >>>>>>>>>> I can't detect any sign of the effect you say is there.
> >>>>>>>>>> James Thomson
> >>>>>>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
> >>>>>>>>> was already pointed out.
> >>>>>>>> no, these are new calipers - in perfect condition.
> >>>>>>>>> It's impossible for an arm to pivot on a
> >>>>>>>>> cylindrical bushing and change the axis of rotation without another pivot
> >>>>>>>>> (which is, in essemce, what beamboy is claiming).
> >>>>>>>> no it's not. it's a simple geometry problem. you not figuring it out
> >>>>>>>> doesn't mean it's impossible - after all, it is observed to be happening.
> >>>>>>> Yes, it's a very simple geometry problem. Far simpler than your
> >>>>>>> explanation of magic pivots describes. The brake pads are adjustable
> >>>>>>> in a number of directions, one of which is rotation about the pad
> >>>>>>> fixing bolt.
> >>>>>> duh. and when that bolt is tightened, they remain fixed. from that
> >>>>>> point on, it doesn't matter /what/ you do, the /delta/ measurements i
> >>>>>> did, remain the same.
> >>>>>>> Look at the brake from the side with the mounting bolt
> >>>>>>> horizontal, and if the brake is set up to go on the rear, the rear
> >>>>>>> ends of the pads are going to be sitting lower than the front ends.
> >>>>>>> Assuming everything is set up square and parallel when the pads are
> >>>>>>> about a rim width apart, this will will give the appearance of the
> >>>>>>> front ends of the pads pointing inwards when you open the caliper all
> >>>>>>> the way. The rear ends of the pads moved farther out horizontally
> >>>>>>> because they are father from the pivot axes. Close the caliper all
> >>>>>>> the way and the front ends of the pads will be pointed out, because
> >>>>>>> they traveled a shorter horizontal distance for the same angle. Re-
> >>>>>>> adjust the pads so that the front ends are sitting lower than the rear
> >>>>>>> when viewed from the side, and you get the exact opposite behavior.
> >>>>>>> Adjust them level, and you're back to boring old parallel motion,
> >>>>>>> which is what everyone who actually wasted their time obeying your
> >>>>>>> command to measure their brakes observed. This is why you need to
> >>>>>>> prove your magic pivot theory by measuring from the arms not the
> >>>>>>> pads. The pads may be fixed, but they are not always fixed in a
> >>>>>>> position that supports your theory. If the second pivot really is
> >>>>>>> angled, there will also be some fore-aft translation of the arm
> >>>>>>> attached to it. Another reason why common sense dictates that this
> >>>>>>> would be an incredibly stupid way to design a brake.
> >>>>>> says the guy that doesn't understand the concepts.
> >>>>> And what concepts would those be? That the distance traveled by a
> >>>>> point on a rigid rotating body does not depend on that point's
> >>>>> distance from the axis of rotation? Because that's what you're trying
> >>>>> to claim, and you're exactly right that I don't understand it. You
> >>>>> would be hard pressed to find anyone with a passing knowledge of
> >>>>> geometry who would buy that one. If you change the relative distances
> >>>>> of the pad ends from the pivot axes (in whichever direction you
> >>>>> believe them to be pointing) the delta measurements you performed will
> >>>>> change. Front or rear, and I'm looking at it right now on a single
> >>>>> pivot caliper.
> >>>> eh? you're basing your entire comment on single pivot???? holy carp.
> >>>>> The ends of the pads farthest from the pivot will
> >>>>> always be farther apart when the caliper is open, and closer together
> >>>>> when it's closed. How do you suppose it is that I can observe
> >>>>> something that you say absolutely has to be the result of one of a two
> >>>>> degree of freedom mechanism on a brake with only one degree of freedom?
> >>>> forget it. if you can't be bothered, nor can i.
> >>> No, I'm basing it on single pivot, dual pivot, and common sense.
> >> no, you're basing it on single pivot and underinformed presumption.
>
> >>> And
> >>> if your observation of changing brake pad distances can be observed in
> >>> a single pivot brake, then it absolutely cannot be proof of out of
> >>> plane rotation.
> >> rubbish.
>
> > Please tell me what it is that I'm presuming. I've duplicated your
> > progressive toe in measurements on both single and dual pivot brakes,
> > and I've changed it to a progressive toe out simply by changing the
> > pad adjustment. If either of those calipers has an arm that's
> > rotating out of plane, brake pad measurements simply are not
> > sufficient proof. Seeing how you're the only person on the planet
> > that believes that this rotation is happening, you're going to have to
> > do a lot more than stomp your feet and yell rubbish to convince me.
>
> i'm not trying to "convince" you - i simply want you to stop confusing
> yourself with irrelevancies about single pivot and pad adjustments [as
> long as they remain fixed, the deltas remain the same] and focus on
> observation of the dual pivot lever action! and even then, the ones i
> have stated. it may indeed be the case that some brakes don't have this
> feature, but as i have observed, campy veloce and record, and 7700
> dura-ace, these definitely do!
As long as they remain fixed where? Fix them in a different place and
the deltas disappear or reverse. This is not irrelevant. It shows
that while your observations of pad angle are necessary conditions to
prove your hypothesis of arm twisting, they are not sufficient. You
have not posted any observations of lever action. Only pad movement,
and only movement in directions that point to more realistic
explanations.
> [email protected] wrote:
> > On Nov 4, 12:23 pm, jim beam <[email protected]> wrote:
> >> [email protected] wrote:
> >>> On Nov 3, 7:27 pm, jim beam <[email protected]> wrote:
> >>>> [email protected] wrote:
> >>>>> On Nov 2, 9:18 pm, jim beam <[email protected]> wrote:
> >>>>>> [email protected] wrote:
> >>>>>>> On Nov 2, 12:53 am, jim beam <[email protected]> wrote:
> >>>>>>>> _ wrote:
> >>>>>>>>> On Thu, 1 Nov 2007 14:08:07 +0100, James Thomson wrote:
> >>>>>>>>>>>> What should I be measuring?
> >>>>>>>>>> "jim beam" <[email protected]> a ?crit:
> >>>>>>>>>>> distance between the front tips of the brake pads with the caliper
> >>>>>>>>>>> open vs. caliper closed, and for the rear tips, open vs closed. when
> >>>>>>>>>>> open, the front tips are further apart than the rears. when closed,
> >>>>>>>>>>> the front tips are closer than the rears. [front caliper]
> >>>>>>>>>> I'm using the moulding seam of the brake block at the point it touches the
> >>>>>>>>>> holder as a reference point on the Ultegra 6500 brakes, and (in the absence
> >>>>>>>>>> of a convenient moulding mark) trying to pick a consistent point on the
> >>>>>>>>>> Centaur pad holder. The measurements are repeatable to within about 1mm, and
> >>>>>>>>>> I can't detect any sign of the effect you say is there.
> >>>>>>>>>> James Thomson
> >>>>>>>>> Either beam's bushings are worn or the arms are loose on the pivots - that
> >>>>>>>>> was already pointed out.
> >>>>>>>> no, these are new calipers - in perfect condition.
> >>>>>>>>> It's impossible for an arm to pivot on a
> >>>>>>>>> cylindrical bushing and change the axis of rotation without another pivot
> >>>>>>>>> (which is, in essemce, what beamboy is claiming).
> >>>>>>>> no it's not. it's a simple geometry problem. you not figuring it out
> >>>>>>>> doesn't mean it's impossible - after all, it is observed to be happening.
> >>>>>>> Yes, it's a very simple geometry problem. Far simpler than your
> >>>>>>> explanation of magic pivots describes. The brake pads are adjustable
> >>>>>>> in a number of directions, one of which is rotation about the pad
> >>>>>>> fixing bolt.
> >>>>>> duh. and when that bolt is tightened, they remain fixed. from that
> >>>>>> point on, it doesn't matter /what/ you do, the /delta/ measurements i
> >>>>>> did, remain the same.
> >>>>>>> Look at the brake from the side with the mounting bolt
> >>>>>>> horizontal, and if the brake is set up to go on the rear, the rear
> >>>>>>> ends of the pads are going to be sitting lower than the front ends.
> >>>>>>> Assuming everything is set up square and parallel when the pads are
> >>>>>>> about a rim width apart, this will will give the appearance of the
> >>>>>>> front ends of the pads pointing inwards when you open the caliper all
> >>>>>>> the way. The rear ends of the pads moved farther out horizontally
> >>>>>>> because they are father from the pivot axes. Close the caliper all
> >>>>>>> the way and the front ends of the pads will be pointed out, because
> >>>>>>> they traveled a shorter horizontal distance for the same angle. Re-
> >>>>>>> adjust the pads so that the front ends are sitting lower than the rear
> >>>>>>> when viewed from the side, and you get the exact opposite behavior.
> >>>>>>> Adjust them level, and you're back to boring old parallel motion,
> >>>>>>> which is what everyone who actually wasted their time obeying your
> >>>>>>> command to measure their brakes observed. This is why you need to
> >>>>>>> prove your magic pivot theory by measuring from the arms not the
> >>>>>>> pads. The pads may be fixed, but they are not always fixed in a
> >>>>>>> position that supports your theory. If the second pivot really is
> >>>>>>> angled, there will also be some fore-aft translation of the arm
> >>>>>>> attached to it. Another reason why common sense dictates that this
> >>>>>>> would be an incredibly stupid way to design a brake.
> >>>>>> says the guy that doesn't understand the concepts.
> >>>>> And what concepts would those be? That the distance traveled by a
> >>>>> point on a rigid rotating body does not depend on that point's
> >>>>> distance from the axis of rotation? Because that's what you're trying
> >>>>> to claim, and you're exactly right that I don't understand it. You
> >>>>> would be hard pressed to find anyone with a passing knowledge of
> >>>>> geometry who would buy that one. If you change the relative distances
> >>>>> of the pad ends from the pivot axes (in whichever direction you
> >>>>> believe them to be pointing) the delta measurements you performed will
> >>>>> change. Front or rear, and I'm looking at it right now on a single
> >>>>> pivot caliper.
> >>>> eh? you're basing your entire comment on single pivot???? holy carp.
> >>>>> The ends of the pads farthest from the pivot will
> >>>>> always be farther apart when the caliper is open, and closer together
> >>>>> when it's closed. How do you suppose it is that I can observe
> >>>>> something that you say absolutely has to be the result of one of a two
> >>>>> degree of freedom mechanism on a brake with only one degree of freedom?
> >>>> forget it. if you can't be bothered, nor can i.
> >>> No, I'm basing it on single pivot, dual pivot, and common sense.
> >> no, you're basing it on single pivot and underinformed presumption.
>
> >>> And
> >>> if your observation of changing brake pad distances can be observed in
> >>> a single pivot brake, then it absolutely cannot be proof of out of
> >>> plane rotation.
> >> rubbish.
>
> > Please tell me what it is that I'm presuming. I've duplicated your
> > progressive toe in measurements on both single and dual pivot brakes,
> > and I've changed it to a progressive toe out simply by changing the
> > pad adjustment. If either of those calipers has an arm that's
> > rotating out of plane, brake pad measurements simply are not
> > sufficient proof. Seeing how you're the only person on the planet
> > that believes that this rotation is happening, you're going to have to
> > do a lot more than stomp your feet and yell rubbish to convince me.
>
> i'm not trying to "convince" you - i simply want you to stop confusing
> yourself with irrelevancies about single pivot and pad adjustments [as
> long as they remain fixed, the deltas remain the same] and focus on
> observation of the dual pivot lever action! and even then, the ones i
> have stated. it may indeed be the case that some brakes don't have this
> feature, but as i have observed, campy veloce and record, and 7700
> dura-ace, these definitely do!
As long as they remain fixed where? Fix them in a different place and
the deltas disappear or reverse. This is not irrelevant. It shows
that while your observations of pad angle are necessary conditions to
prove your hypothesis of arm twisting, they are not sufficient. You
have not posted any observations of lever action. Only pad movement,
and only movement in directions that point to more realistic
explanations.
