Why are capstan wheels different size?

do they have the same capstan diameter?

Its been a while since I've seen the inside of a cassett drive.

But memory tells me you have a pinch roller with pin shaft that governs the actual speed.

Jamie

Yep.

And I have long thought that with the small diameter of the capstan it must be the availability of excellent, and cheap, bearings for the shaft that made it possible to keep the wow and flutter down to acceptable levels...

Mike.

Jasen Betts asked wisely:

I was just about to say ?Silly question!? but instead thought better...

one 2mm, one 2.2mm

I guess the difference is driven (c; by the fact (stated by Phil) that the flywheels are different diameters to discourage mechanical resonance.

Thanks Jasen!

Presumably the belt speed changes, or the capstains themselves are different diameters.

One (the small one) is the motor capstan.

The other one is the pressure capstan.

Direction is given by the rotation of the first one and speed is servo-controlled.

Generally there is a lever for the tension of the tape.

The tape speed is controlled by the motor drive capstan. Doesn't matter which way the tape is going. The two flywheels are different sizes, but have the same rotation speed. That causes the belt to stretch on one side and compress on the other to account for the different sizes. That belt tension creates the tape tension. That's independent of the direction of the rotation. Tape speed across the heads is always controlled by the drive motor.

May seem pedantic , but there is a rationale. Having been here before, to standardise to using a strobe to set tape speed, in the absence of a test tape of known goodness, ie not stretched, as the people wanting cassette players repaired these days tend to be musically on the ball as regards being perfect pitch. You'll probably find the spindle diameters are 1.99mm and 2.19mm . I got a precision mechanical engineer to measure a dozen or more random spindles and they were all *.*9 mm , presumably because the available bearings are *.*0 mm

Aiwa AD WX888 , 1997,I worked on once, spindle to one capstan 2.49mm diameter and the other 2.69mm

Aiwa ADR470, forward flywheel was inside the loop, reverse was outside the loop. Both always driven. choice of pinch rollers determine direction. Flywheel diameters compensate for inside/outside belt diameter. Only speed adjustment was screw-driver inside the motor housing itself.

Harman Kardon HK300 had a single flyheel, spindle impressed alternately on fw or rev through a clutch that was always disintegrating. Same in-the-motor adgustment.

RL

Really?

Then what is the use of that little pinch roller and drive shaft that the tape fits between, for?

Jamie

All those mechanical means of reproducing sound - wax disks, tinfoil, shellac, plastic, wire, tape - were all awful. Chemical photography was a nuisance, too. Ditto typing and carbon paper.

Yeah but look at the bit-error rate you can tolerate. A CD would be worth less with that many errors.

Cheers

Yeah, yeah, yeah.

Gotta have a source platform in order to digitize all that media...

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.

Perhaps you mean recording? No, still mechanical. Storage? Maybe.

Of course, there's nothing mechanical in electronics, is there...

It's the programme material, the idea and its conception that's important; not the means of conveyance.

RL

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... Seems to me like it COULD work.

I heard from many girls that size doesn't matter !! LOL