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.

Using non identical flywheels avoids a possible resonance problem in the system.

... Phil

Den fredag den 11. marts 2016 kl. 22.22.16 UTC+1 skrev DaveC:

Cool, I got a CS-34D. It made some good recordings with tdk SA tapes.

Cheers

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

I thought I already posted this butm these guys are all nuts.

That is NOT a dual capstan deck, it has two capstans to facilitate reverse play. they are not both active at the same time, How could they be ? They c an't. Unless you stick that pinch roller inside the cassette and... fukit, they tried that with eight tracks. Plus it wouldn't fit.

Only one capstan is active at a time, that is when the pinch roller is enga ged. both capstans turn in opposite directions all the time but it doesn't mean s*it until the pinch roller hits the tape. If both ever hit at the sam e time the deck would come to a screeching halt, LITERALLY.

Look at it more closely and you will see.

Oh, and what got lost here was I posted that the thickness of the capstan belt makes the difference in diameter necessary. Some decks may have separate speed setting for each direction but in 40 years I have never run into one.

Does that makes the replacement belt manufacture critical? Didn?t know this when I ordered belts (yet to arrive). Just treated selection like a car?s fan belt: primarily, original circumference; second, width; tertiary (or not at all), thickness. Will have to see what I get...

This deck does have pitch control on the front panel so can adjust for that, if excessive, but only 1 speed adjust pot, not separate ones for fwd, rev.

(op)

What model number?

RL

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

Sony TC-WR99ES.

I?ve got original svc man and similar models (using same mechanism) sm?s also.

Thanks.

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