Video cassette - topology question

I'm not sure I actually understand your question. However...

Most (if not all) VCR tapes, regardless of format, are "B wind" -- the oxide faces "out".

Most analog audio reel-to-reel formats are "A wind" -- the oxide faces "in". Most analog audio cartridge and cassette formats are "B wind".

It doesn't matter "who struck John". You want the tape to go in straight line from one hub to the other, with oxide facing the "outside" of the cartridge.

Mr Cook, your writing is often unclear. You sometimes write as if English were not your native language. You need to learn to write more clearly.

"William Sommerwerck"

Need a brain transplant to fix that.

.... Phil

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As I understood him, he asked if videocassette tape was meant to have a half-(or greater-) twist. Or, by extension, should it lay untwisted like an audiotape, whether open reel or cassette.

Thanks.

The answer, of course, is untwisted.

Could you please translate that into common English?

Oh that's what he said. Well crap, it's simply logic that tells you tapes should not be twisted.

How do you explain a Klein bottle in text ? It is a topological question involving twists and turns. If when a tape runs at full tilt back and the other end hits the clear tape end stop, failing of rate sensor. In that jarring of the tape, if it loops over the spool and between the spool flange and the clear cover of the cassette, before tightening up and jamming between the reel of tape and the spool flange, will it lead to a twist in the tape .

As with many...it is perfectly clear in his head!

Any twist in the tape is not normal (only in the old 8-track endless loop audio/cart tapes). Also, there shouldn't be any slack in the tape.. if slack exists, there are transport problems and/or adjustments to compensate/minimize that condition.

Old VCRs had very sturdy (with real metal!) braking systems to stop reel movement, and newer VCRs have had reel speed sensing circuits (for quite a few years) that begin to slow the drive as the tape nears the ends.

-- Cheers, WB .............

Only "continuous loop" tape cartridges use a closed loop of tape. The infamous 8-track cartridge pulled the tape from the inside of the spool, then fed it back to the outside. The tape has to be slightly twisted to fit within a compact shell, but there is no net turning of the tape -- the top edge of the tape remains on the top at all times.

I know of no tape system that used a Moebius strip.

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Yes. Just played about with an audio reel recorder, to check the scenario you describe. and if the tape loops over the reel, you must then loop it back again (the way it came, as it were) - if you continue to pull tape off the spool there is a twist. HTH B.

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passage,

Yes. Just played about with an audio reel recorder, to check the scenario you describe. and if the tape loops over the reel, you must then loop it back again (the way it came, as it were) - if you continue to pull tape off the spool there is a twist. HTH B.

That was what I was trying to get an opinion on. I was aware that pulling wire axially off the end disc of a cable drum introduced a twist in the wire but could not decide , thinking about it for a cassette . Whether the same applied to slipping one turn off a VCR spool by it passing over the top of the spool in the gap between spool and transparent window on the cassette cover, then slipping back into the volume where the tape should be, but mangled and pulled in.

Ok that makes more sense. What failure mode are you trying to explain?

I never knew there was a name for this oxide in or out. I recall some horrible hong kong or taiwanese audio cassettes that were wound the wrong way- the oxide was on the wrong side.

If the tape jumped over the spool, there would be full twists, and no half twists. So the spool would need to be turned at minimum, a full turn (so that the correct side of the tape remains facing out). If you are seeing a half twist anywhere (wrong side of the tape out), the other half of the twist (or the return half twist) is simply folded onto the spool somewhere.

examine closely, the tape may have twisted and then rolled up on one of the reels, looks normal, and then jumped again. [happened to me] easy to tell by shininess of tape surfaces.

I've repaired over 6 tapes that got crunched, including a pre-recorded purchased tape.

I had to either roll enough out to find and straighten or cut off bad section (lost 15 minutes at start of reel) and tape back to leader - careful do not transfer human oils onto the tape

Recommend wiping the mylar substrate to smooth down the roughness, else you run the risk of breaking a head on the VCR player, or at least gumming it up with a lot of powder residues.

Better, if possible do NOT disassemble casette, simply make some tools to allow you to pull the tape out of the cassette, rewind, etc. Tools that keep the flip lid open, tools that unlock reels etc Just pull out enough to work on the damaged section of tape, then wind back up. Once finished, do a non-viewing wind/rewind from one end to the other in order to get the tension and take up uniform inside the cassette.

Unless it somehow managed to get over the top of the hub (EXTREMELY unlikely), any twist in the tape will have a reverse 'mate' so that it all cancels out. That portion will be so mangled that it might make more sense to cut out the damage and splice it. I've been repairing broadcast VTRs and the occasional tape and have never seen tape slipping over the top of the hub inside of the cassette.

G=B2