Why are capstan wheels different size?

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.

Peter Wieck Melrose Park, PA

I certainly was not taking it into account. Probably because it is movement along the length of the tape and not sideways that gives rise to speed modulation at the pick-up.

Mike.

Yikes! You?re right...

(op)

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)

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.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

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...

** Just to rub it in, the SIDEWAYS pressure from the pinch roller forces the capstan shaft against the bearing and inhibits any "chattering". I really works and I see machines ( ie Roland Space Echos) with noticeable play in the capstan bearing that have low W&F.

.... Phil

** Tape speed is determined by the surface speed of the motor pulley divided by the flywheel to capstan diameter ratio.

That ratio might be 20:1 making the pulley surface speed 37.5 inches/S for a standard cassette speed of 1-7/8 inches/S.

.... Phil

Wrong !

The linear speed is RPM/60*pi*D (D in meter), eventually *100 if it's given in cm/s ; for a cassette it is 4,75 cm/s. It is determnied by the little axis that tha tape is pinched to.

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

On 12 Mar 2016, snipped-for-privacy@gmail.com wrote (in article):

OK I?ve learned from you how to determine tape speed by measuring the capstans.

But you have not answered the question (that apparently should never have been asked) why the 2 flywheels are different sizes.

(op)

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.

--
Security provided by Mssrs Smith and/or Wesson. Brought to you by the letter Q

The singing arc.

However it depends on how you want to be about this. If someone want no moving parts that is fine and the singing arc works for that.

But your eardrum still moves as well as the linage from it to the cochlea.

Plus the fact that the air itself moves.

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