Why are capstan wheels different size?

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.

That recalls some old saw about whether anything is real if not observed. I think sound has been reproduced even if no-one hears.

As to moving air counting as a "part"... In space no-one can hear spurious arguments!

Mike.

THE *MOTOR PULLEY* DIAMETER..... Not the pinch roller.

Peter Wieck Melrose Park, PA

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

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

On 14 Mar 2016, N_Cook wrote (in article ):

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.

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

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

Where the drive belt is curved, the outside radius is greater - but both flywheels are on the INSIDE of curves.

.... Phil

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?

Mpfffff... Let's get down to it.

The most likely reason the two similar-function parts are of a different si ze is that the physical parameters of the entirety suggested/led to this de cision. 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

IOW it fits where the "151" is shown, where the belt is curved the opposite way.

.... Phil

Yes

Yes

look at the diagram (in the original post). The Belt goes around the 2 flywheels such that the belts are driven in opposite directions.

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)

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 result ing in less wow and flutter I would assume.

Interesting. I remember the old Walkmans that had two flywheels going in op posite 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 w ould cancel out.

Really, on the surface is seemed that the thickness of the belt was the rea son for this but that has been eliminated. Would be nice to look at a few o ther models and see how they are put together. Ha, there is only one autore verse deck on the property and it doesn't belong to me. That'll learn me to throw s*it out.

A rubber belt and flywheel system has a resonant frequency - resulting fro m 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 ine rtias are non identical so the resonant frequencies differ and so do not re inforce.

.... Phil

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 Electronics Engineering school while serving in the U.S. Army. I've worked with very intelligent people who only finished high school, and I've had the misfortune of working with those who can pass tests but who are so @#$%^&* stupid that they set the shop on fire with a soldering iron.

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.

I had health problems from an early age, so I spent a lot of time reading and experimenting since I couldn't play in any sport. I was born in the early '50s, when poorly trained doctors continued to prescribe DES to pregnant women in the false belief that it prevented miscarriages. It caused many health issues in the children, like my life long problem with infections. The last one required a trip to the hospital. I was also born with poor eyesight, and have worn glasses since elementary school. I now have to sit about 12 inches from a 24" monitor to see what I'm typing. :(

I taught Boolean Algebra to myself, to be able to write software to track the C band birds. tHe program asked for your Latitude & Longitude, then it printed out a two page report with the Azimuth and Elevation for every bird you could see from your location. The program let you enter your name, so the report stated, Prepared by:----- ---- to make people think it came from an engineering service.

The Commodore 64 didn't have several functions I needed, so I had to create them, as well. I always enjoyed a challenge, and often got what others had given up on. That is why I have seen so many odd conditions in equipment, in the last 55 years.

I was a Nerd, long before it was cool. :)