Pinch roller comparison

One of the reasons I never bought into 8 track in its heyday was its
weak pinch roller system; that is, it was inaccessible for routine
cleaning. 4 track was vastly superior in this regard, and superior in
a lot of other ways too, as the broadcast industry confirmed by its
world wide use of Fidelipac even today. However, enterprising folks
have routinely opened their carts (a REAL pain in the ass on some of
them, but necessary) to do so just to take care of what should be a
routine maintenance procedure.

Lots of folks denigrate the hard pinch roller that came out later, but
after some experimentation and testing, I've found it to actually work
BETTER than a lot of the earlier rubber rollers. One reason is wear
to the rubber rollers, a problem on any tape format. Recently, I've
come across a lot of carts which have swollen rubber pinch rollers, as
well as "grooved" ones, where there is a definite depression where the
tape ends up. Thus, the ridges on either side contact the capstan,
and there's a microscopic gap that allows, when combined with the
fairly slippery backing of lubricated cart tape, a lot of flutter
problems. Mashing the cart in further to the capstan only succeeds in
slowing the capstan down when it runs out of torque, and the tape
keeps slipping. The plastic roller won't do this, and never has a
ridge worn in it. Another observation is that softer rubber rollers
seem to have an appetite for graphite that allows the graphite to get
into the rubber compound itself, making cleaning a chore. Cleaning a
grey plastic pinch roller is done easily even with a cloth dampened
with a household cleaner.

A look at the design tells the story. This isn't really a "hard"
plastic at all, but has a slight bit of elasticity. A center plane of
plastic holds the outer cylinder, thus ensuring the most force against
the capstan shaft goes to the middle of the tape...hopefully. Thus,
there's no real contact between the pinch roller and the capstan, with
all energy of the capstan being imparted to the tape itself to move
it, and any remaining being transferred to the pinch roller post,
which is dissipated by heat of friction. Classic pinch roller design
in something different; a resilient rubber compound presses the tape
against the capstan and also against the capstan itself, thus
providing a locked system in which energy is transferred to the tape
on both sides, rather than just from the capstan itself.

A big disadvantage, it seems, to the "hard" roller system is the same
as it is when using a harder pinch roller on commercial RTR
machines...anything on the backing winds up on the pinch roller.
However, "sticky" soft pinch rollers, which many claim to deliver the
best tape speed control, have the exact same problem, but for a
different reason...the adhesiveness of the soft rubber grabs
whatever's on the backing, too. I remember years ago using a line of
aftermarket pinch rollers on Ampex 300 and 350 transports that really
worked well...until you hit a splice, and then all hell would break
loose if any "ooze" from the splicing tape was present! This is why I
"back tape" all 8 tracks, putting the foil on the oxide side and an
angled layer of Quantegy or Scotch on the other...the tape on the
backing side ends the possibility of any oozing of adhesive from the
foil tape, thus preventing it from causing the capstan to "grab" the
splice and lunch the cartridge. This is a common failure mode in many
cartridges I've rescued lately...the splice winds up wrapped around
the capstan and it then tries to pull both ends around it, breaking
the tape eventually. Another sure-fire way to screw up ANY splice:
use plain old Scotch "Magic Tape" or other stationary type tape. NOT
made for the purpose, it'll start to ooze adhesive with any
application of pressure or temperature, thus destroying the
cartridge's contents in short order. Splicing tape uses a thin layer
of non-oozing adhesive specially designed for the purpose. I used to
swear by Scotch, but Quantegy's new "blue" tape is the best I've ever
used. An Edit-All® or other ¼" splice block is a necessity to do a
good job. The old "cut it with scissors and eyeball it" method RARELY
works right and will usually fail, not to mention put a nasty "thump"
on your tape from magnetized scissors, also magnetizing your head for
you!

Upon first glance, I thought the gray plastic pinch rollers were a
"cheapness" change to 8 track carts in later production, but I've
found through testing that they actually work better than some soft
rubber rollers with a lot of miles on them. Use of "Rubber-Renu" and
other pinch roller solvents helps clean them and restore tackiness,
but it also swells the rubber...bad thing to have on 8 track, where
the distance from the center lines of the capstan and the pinch roller
are supposed to be rigidly fixed. A swollen pinch roller on an 8
track invariably leads to excessive motor current, slow speed, flutter
and other problems.

A continual gripe about 8 tracks was the plethora of various designs
with no standardization. Thus, pinch rollers vary in both outside
diameter and inside bearing diameter, making them hard to interchange.
Of course, other tape formats have this same problem to a degree, but
the point here is that the pinch roller is native to the machine in
those formats, not the media. One way to remedy a swollen pinch
roller that is causing these problems is to chuck it up in a small
lathe or drill motor and, using a flat, perpendicular plane of 1000
grit abrasive, turn it down a tad until optimal diameter is attained.
A good rule to follow for a "grooved" roller is to just turn it until
the ridges on the sides of the tape path just go away. I did this to
a bunch of hopeless Lear carts, and the results were quite good, where
previous, the pinch roller wasn't even contacting the tape all that
well. Each cart will be different too, due to wear on the bearing
post, another annoyance with 8 track. It seems that my usage of PTFE
dry lube on these and other rotating parts almost eliminates friction,
and thus wear, on these points, important at the capstan, but
non-critical for wear on the spool spindle, although it seems to
greatly decrease any friction.

One note on lubing these things...using PTFE or other slick, dry
lubes, you CAN overdo it! Being a dumb system, 8 tracks have no reel
brakes or anything other than just friction to stop them. One day,
after fast forwarding a cartridge to the foil on a cart I had just
treated to copious amounts of PTFE, the deck stopped, but the tape
kept whirling around while it ejected, causing a mess of slack inside.
Depending on your luck when starting such a cartridge the next time,
there might be no harm done, OR the tape will wind up all over the
place internally, quickly causing a jam. The less tape guides in the
cart, the more easily this happens. Again, this is a very troublesome
format in this regards, and it NEVER happens with cassettes, thus
partially explaining why people eschewed 8 track for cassettes in
droves...the replacement format just didn't break like 8 track did!

More later....

dB

Neat post, thanks...

snip...after fast forwarding a cartridge to the foil on a cart I had just
treated to copious amounts of PTFE, the deck stopped, but the tape
kept whirling around while it ejected, causing a mess....end

I have given up on fast forwarding carts. I use two machines with automatic
eject as 'winding' slaves that always forward my carts to the splice at regular
speed. Pop them in and swing back later to pick them up. later, ron

As I've said all along, 4 track rules! If only the head technology was as good
when the 4 track was trying to get established, ( and if the marketing had been
as brilliant) the 8 track wouldn't have had a chance.
Dan 1.5

Subject: Pinch roller comparison
From: DeserTBoB

One of the reasons I never bought into 8 track in its heyday was its
weak pinch roller system; that is, it was inaccessible for routine
cleaning. 4 track was vastly superior in this regard, and superior in
a lot of other ways too, as the broadcast industry confirmed by its
world wide use of Fidelipac even today. However, enterprising folks
have routinely opened their carts (a REAL pain in the ass on some of
them, but necessary) to do so just to take care of what should be a
routine maintenance procedure.

"Danspeakin" wrote in message
...
As I've said all along, 4 track rules! If only the head technology was as
good
when the 4 track was trying to get established, ( and if the marketing had
been
as brilliant) the 8 track wouldn't have had a chance.
Dan 1.5


4 tracks sound really full and rich. I've got one that Dan Gibson fixed up
for me.
I don't have many 4 tracks, but the ones I have sound great.


winnard

On Fri, 29 Oct 2004 23:12:47 -0500, "winnard"
wrote:

4 tracks sound really full and rich. I've got one that Dan Gibson fixed up
for me.
I don't have many 4 tracks, but the ones I have sound great. snip

It's all in the track width. 8 track's skimpy track width has the
same problems of cassette with Type I oxide and no noise
reduction...low signal-to-noise ratio and more limited headroom. 4
track was the exact same as RTR 4 track...not the best, but better
than 8. So, what you were left with as any advantage to 8 track was
tape speed, theoretically. Old time audiophiles remember when "high
fidelity died" in 1960, when the pre-recorded RTR tape market switched
from NAB standard 2 track to the reverse 4 track format. If you
listen to one of those old 2 track commercial tapes today on a good 2
track deck, they were pretty damned good...good enough to cut ADD CDs
and no one would be the wiser. Many still claim that this was the
raison d'être for 2 track's demise...the labels were worried even back
then about "pirating." 4 track, with its bass fringing and inferior
noise characteristic, precluded enterprising bootleggers from cutting
saleable disks from them.

As Dan said, failures of state of the art and marketing let to an
early end to 4 track carts and a win for the inferior (and stolen,
actually) Lear system. History is full of such successes of inferior
technology...the inferior Hammond organ over the superior Everett
Orgatron in the '30s, the success of Gates' stolen DOS over CP/M and
UNIX, the triumph of JVC's inferior VHS format over Sony's Beta, and
so on. In the latter case, it was crass marketing that made VHS more
popular ("I can get eight hours of stuff on an VHS, only 6½ on Beta,
thus, VHS must be better...right?") due to the "masses being asses."
Another example of consumer ignorance! It also helps to do such
things in a capitalistic society which favors quick profits over
worth, as is found easily in the US.

With the availability of 4 track/¼" decks, it's easy as pie for a
non-pro to simply record material on a 4 track/4 channel RTR (Teac
3340As and 3440As, as well are Otaris come immediately to mind) on
lube-backed tape and drop the spool into a cartridge. In fact, I did
just that years ago to make tapes for a guy who had one of the old
Muntz decks in his car using ScotchPak broadcast cartridges. It
sounded pretty darned good, but it was obvious there were problems due
to the cheap head and cheaper electronics of the player. Really good
4 track players were never a reality. Certainly, the head technology
did exist at the time, but not at a pricing point that Muntz would
accept. Like everything else he did, Earl Muntz' goal was to get
things to market CHEAP...and thus was the failure of 4 track carts to
attract an aurally more sophisticated following. If you know about
"Madman" Muntz, you know that after his failed sports car venture,
everything he did was "on the cheap." His TVs had the most crude
circuitry and cheapest components in all of tube TV as a profitability
enhancement. Shame, since 4 track was a really good format with room
to grow. Lear's theft of the cartridge idea doomed the cartridge
format forever in the eyes of more sophisticated users. Again, the
BEST cartridge format never really got off the ground, except for a
few demanding audiophiles...Sony's Elcassette.

Why people deify Lear for his 8 track theft is beyond me, but I do see
where lots of "trackers" seem to hold him in high regard. In
actuality, he was as much of an "idea thief" as was the "inventor" of
the Hammond Organ, Laurens Hammond, who basically stole the idea from
the original inventor of the Telharmonium around 1900, Thadeus Cahill.

But...that's another story for another group!

dB

what do the railroad guys think of that ??

http://groups.google.com/groups?hl=e...m%26rnum%3D172

http://groups.google.com/groups?hl=e...m%26rnum%3D169

http://groups.google.com/groups?hl=e...m%26rnum%3D290

DeserTBoB wrote in message . ..
On Fri, 29 Oct 2004 23:12:47 -0500, "winnard"
wrote:

4 tracks sound really full and rich. I've got one that Dan Gibson fixed up
for me.
I don't have many 4 tracks, but the ones I have sound great. snip

It's all in the track width. 8 track's skimpy track width has the
same problems of cassette with Type I oxide and no noise
reduction...low signal-to-noise ratio and more limited headroom. 4
track was the exact same as RTR 4 track...not the best, but better
than 8.



duh....