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Why are capstan wheels different size?
I heard from many girls that size doesn't matter !! LOL
DaveC a écrit : Oh, smarter-than-I people, http://imgur.com/WPEoOu1 The 2 belt-drive capstan flywheels in an auto-reverse cassette mechanism are different sizes. (Motor drive pulley will be in the small loop end of the belt in illustration above.) How does that result in the same tape speed in both directions? Confused... |
Why are capstan wheels different size?
On Sun, 13 Mar 2016 15:34:07 -0000, MJC
wrote: In article , says... I can't think of a single method of 'reproducing sound' that doesn't involve mechanical means. Sound is a mechanical phenomenon. Humans use flapping meat. I can imagine a method that used heat to move the air, perhaps with a plasma to make it fast. (Like a modulated lightning flash.) But I cannot be bothered to construct a search to find out if it has been done successfully... See Thermoachoustic Technology. www.lanl.gov/thermoacoustics/Pubs/ RL |
Why are capstan wheels different size?
On 13/03/2016 16:22, Don Bruder wrote:
In article , MJC wrote: In article , says... I can't think of a single method of 'reproducing sound' that doesn't involve mechanical means. Sound is a mechanical phenomenon. Humans use flapping meat. I can imagine a method that used heat to move the air, perhaps with a plasma to make it fast. (Like a modulated lightning flash.) But I cannot be bothered to construct a search to find out if it has been done successfully... Mike. I recall a conversation from years ago with a *VERY* old theater projectionist, who spoke of what he called "flame speakers". Don't know if it was an artifact of his (at the time) 80+ year old mind going, or reality, but what he described made sense to me on several levels, though I've never bothered to try chasing it down. Apparently, back in the early days of talkies, one method of sound production involved a gas nozzle (unsure if he meant gasoline, or something like propane/LP gas) "tuned" to produce a blue flame (he was very clear on that point - lots of the conversation came back to how he had to tinker with the flame at each showing, otherwise the sound wasn't good) several feet tall in a combustion chamber, into which was shoved a set of tungsten electrodes. The 'trodes were driven at high voltages by any of several amplification methods (frequently varying by theater, if the old guy's tale was to be believed) to charge the plasma of the flame, which apparently caused it to "dance", driving a diaphragm like that of a speaker. Supposedly, amazingly high volumes with very good fidelity could be achieved. Like I say, I've never actually gone to the effort of tracking it down, and I have no idea if it was a failing mind's invention, or reality, but... shrug Seems to me like it COULD work. Wasn't there some scheme to generate sound for large area advertising by using aurora? presumably someone realised polar bears don't buy much stuff. |
Why are capstan wheels different size?
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Why are capstan wheels different size?
On 14/03/2016 02:34, MJC wrote:
In article , says... I can't think of a single method of 'reproducing sound' that doesn't involve mechanical means. Sound is a mechanical phenomenon. Humans use flapping meat. I can imagine a method that used heat to move the air, perhaps with a plasma to make it fast. (Like a modulated lightning flash.) But I cannot be bothered to construct a search to find out if it has been done successfully... Mike. http://www.roger-russell.com/ionovac...c.htm#ionofane http://www.ebay.com/itm/171837115818 |
Why are capstan wheels different size?
On Saturday, March 12, 2016 at 11:16:48 AM UTC-5, DaveC wrote:
wrote: The capstan is a passive device. The motor pulley diameter via the *pinch roller* determines the tape speed. The capstan wheel can be any size at all. By my mind that is backward: the pinch roller is passive (not being driven). The capstan shaft (~2mm diam) is driven by capstan flywheel/belt/motor pulley. No? Thanks. (op) THE *MOTOR PULLEY* DIAMETER..... Not the pinch roller. Peter Wieck Melrose Park, PA |
Why are capstan wheels different size?
On 14/03/2016 17:27, legg wrote:
On Mon, 14 Mar 2016 07:04:19 -0700 (PDT), " wrote: On Saturday, March 12, 2016 at 11:16:48 AM UTC-5, DaveC wrote: wrote: The capstan is a passive device. The motor pulley diameter via the *pinch roller* determines the tape speed. The capstan wheel can be any size at all. By my mind that is backward: the pinch roller is passive (not being driven). The capstan shaft (~2mm diam) is driven by capstan flywheel/belt/motor pulley. No? Thanks. (op) THE *MOTOR PULLEY* DIAMETER..... Not the pinch roller. Peter Wieck Melrose Park, PA Question was re flywheel diameter differences. Motor pulley drives both. Same belt on two different dia flywheels, yet obtains same spindle rotation at their separate pinch rollers. Identical belt speed should drive a smaller dia flywheel faster. Motor speed does not account for this physical difference, as it is uniform for both functions. Supposition is that the difference in flywheel dia is related to belt thickness, as one flywheel is inside, and other is outside the drive belt loop. RL That would be lead to a much closer pair of pulley diameters. But then although you have a free range of pulley sizes, as cast and machined, the sintered metal bearings come in only discrete sizes of * x 0.1mm , so you have to increase/decrease the pulley diameter ratio to then be compatible to 2 available bearing diameters and hence spindle diameters. That is the reason i'd go for |
Why are capstan wheels different size?
On Mon, 14 Mar 2016 07:04:19 -0700 (PDT), "
wrote: On Saturday, March 12, 2016 at 11:16:48 AM UTC-5, DaveC wrote: wrote: The capstan is a passive device. The motor pulley diameter via the *pinch roller* determines the tape speed. The capstan wheel can be any size at all. By my mind that is backward: the pinch roller is passive (not being driven). The capstan shaft (~2mm diam) is driven by capstan flywheel/belt/motor pulley. No? Thanks. (op) THE *MOTOR PULLEY* DIAMETER..... Not the pinch roller. Peter Wieck Melrose Park, PA Question was re flywheel diameter differences. Motor pulley drives both. Same belt on two different dia flywheels, yet obtains same spindle rotation at their separate pinch rollers. Identical belt speed should drive a smaller dia flywheel faster. Motor speed does not account for this physical difference, as it is uniform for both functions. Supposition is that the difference in flywheel dia is related to belt thickness, as one flywheel is inside, and other is outside the drive belt loop. RL |
Why are capstan wheels different size?
On 14 Mar 2016, N_Cook wrote
(in article ): That would be lead to a much closer pair of pulley diameters. But then although you have a free range of pulley sizes, as cast and machined, the sintered metal bearings come in only discrete sizes of * x 0.1mm , so you have to increase/decrease the pulley diameter ratio to then be compatible to 2 available bearing diameters and hence spindle diameters. That is the reason i'd go for I (op) have accepted the theory that difference is to avoid additive resonance of the capstan shafts in bronze(?)--not ball--bearings. Difference flywheel sizes plus different capstan shaftssizes (2mm and 2.1mm) results in same tape speed (in opposite directions--this is an auto-reverse mechanism) and different resonances. |
Why are capstan wheels different size?
On Monday, March 14, 2016 at 12:28:26 PM UTC-4, legg wrote:
Question was re flywheel diameter differences. Motor pulley drives both. Same belt on two different dia flywheels, yet obtains same spindle rotation at their separate pinch rollers. Identical belt speed should drive a smaller dia flywheel faster. Motor speed does not account for this physical difference, as it is uniform for both functions. Supposition is that the difference in flywheel dia is related to belt thickness, as one flywheel is inside, and other is outside the drive belt loop. Um... A flywheel is a momentum device attached to a system to provide smoothing. Many (very much most) DC motors are pulse driven. The flywheel removes these pulses. Tape speed is determined by the capstan motor pulley diameter. FULL STOP. Peter Wieck Melrose Park, PA |
Why are capstan wheels different size?
On Mon, 14 Mar 2016 11:41:28 -0700 (PDT), "
wrote: On Monday, March 14, 2016 at 12:28:26 PM UTC-4, legg wrote: Question was re flywheel diameter differences. Motor pulley drives both. Same belt on two different dia flywheels, yet obtains same spindle rotation at their separate pinch rollers. Identical belt speed should drive a smaller dia flywheel faster. Motor speed does not account for this physical difference, as it is uniform for both functions. Supposition is that the difference in flywheel dia is related to belt thickness, as one flywheel is inside, and other is outside the drive belt loop. Um... A flywheel is a momentum device attached to a system to provide smoothing. Many (very much most) DC motors are pulse driven. The flywheel removes these pulses. Tape speed is determined by the capstan motor pulley diameter. FULL STOP. In these machines a single motor with a pulley on its shaft, drives the outer rims of the two differently sized flywheels, through a single belt. I've measured the spindles at the pinch rollers and they are a different diameter, as was suggested by DaveC, so belt thickness isn't responsible for compensation of the flywheel sizes - the spindles are scaled with the flywheel diameter. Never occurred to me to wonder about this, before, or to check it out. Happy just to keep them going. RL |
Why are capstan wheels different size?
N_Cook wrote:
Supposition is that the difference in flywheel dia is related to belt thickness, as one flywheel is inside, and other is outside the drive belt loop. RL That would be lead to a much closer pair of pulley diameters. ** The supposition is nonsense. Where the drive belt is curved, the outside radius is greater - but both flywheels are on the INSIDE of curves. ..... Phil |
Why are capstan wheels different size?
to the op..
only one pinch roller is engaged at a time, depending upon which direction the tape is traveling? so the two flywheels turn in opposite directions? How do they get the second flywheel to spin in the opposite direction? Maybe that has something to do with the need for a different size? M |
Why are capstan wheels different size?
On Tuesday, March 15, 2016 at 9:29:42 AM UTC-4, wrote:
Maybe that has something to do with the need for a different size? Mpfffff... Let's get down to it. The most likely reason the two similar-function parts are of a different size is that the physical parameters of the entirety suggested/led to this decision. As neither have *one damned thing* to do with the actual tape speed, the reasons may be no more complex than that. Peter Wieck Melrose Park, PA |
Why are capstan wheels different size?
wrote:
so the two flywheels turn in opposite directions? How do they get the second flywheel to spin in the opposite direction? ** Look at the diagram - the belt goes most of the way around the larger flywheel ( 153 ) but only a small part of the way around the smaller one ( 152). IOW it fits where the "151" is shown, where the belt is curved the opposite way. ..... Phil |
Why are capstan wheels different size?
only one pinch roller is engaged at a time, depending upon which direction
the tape is traveling? Yes so the two flywheels turn in opposite directions? Yes How do they get the second flywheel to spin in the opposite direction? look at the diagram (in the original post). The Belt goes around the 2 flywheels such that the belts are driven in opposite directions. Maybe that has something to do with the need for a different size? M Flywheels are differentdiameters AND capstan spindles (pressed into the center of the flywheels) are different diameters. The flywheel/spindle diameters are calculated such that the resulting tape speed is the same for both, only in opposite directions (one for Side A, one for Side B). The reason for the differences, it seems, is to help avoid (or minimize) resonant frequency set up by the spindles turning in their bearings. Different diameters/speeds = lower resonance. (op) |
Why are capstan wheels different size?
So let me get this straight. The consensus now is that it has nothing to do with the thickness of the belt but is to avoid resonance, Logically resulting in less wow and flutter I would assume.
Interesting. I remember the old Walkmans that had two flywheels going in opposite directions, not for autoreverse, but so that when the unit was moved, turned whatever, it would maintain the speed. But in that case of course the two flywheels were the same weight and diameter so the angular forces would cancel out. Really, on the surface is seemed that the thickness of the belt was the reason for this but that has been eliminated. Would be nice to look at a few other models and see how they are put together. Ha, there is only one autoreverse deck on the property and it doesn't belong to me. That'll learn me to throw **** out. |
Why are capstan wheels different size?
wrote:
So let me get this straight. The consensus now is that it has nothing to do with the thickness of the belt but is to avoid resonance, Logically resulting in less wow and flutter I would assume. ** The OP also posted his Q on sci.electronics.design and in my first reply there I pointed out the possible resonance issue as the reason for differing flywheel diameters. A rubber belt and flywheel system has a resonant frequency - resulting from the springiness of the belt and the inertia of the wheel. I figured that where two flywheels are coupled by the same belt, it is better if their inertias are non identical so the resonant frequencies differ and so do not reinforce. Really, on the surface is seemed that the thickness of the belt was the reason for this but that has been eliminated. ** A really dopey idea based on a fallacy. ..... Phil |
Why are capstan wheels different size?
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Why are capstan wheels different size?
Michael Terrell wrote: " Only two students in my school system got every question right on
that part of the aptitude tests. Myself, and a girl who like to work on cars. I also got the top scores in math and science. I only got a 90 for English. I took every math, science and shop class that they could fit into my schedule, each year. Several years later I tested out of an " I envy people like you - seriously! It shows how influences(chemical and otherwise) during and after conception, and after birth and during childhood - chemical and otherwise - can have an effect on a child and later an adult. "Only got a 90 for english"??? I was lucky to get 90s in THAT - and 60s to 70s in all my other subjects. Math? They had to make up a grade just so I wouldn't have trouble later on getting in to college. My single biggest regret in LIFE - not being able to even read numbers, let alone add, subtract, multiply, or do anything Greek with them(!) And I trace it all back to some activities my expectant folks were engaged in back in the late '60s, and some choice names my Dad coined me post-toddler-hood. |
Why are capstan wheels different size?
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