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#1
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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 |
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#2
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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 |
#3
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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. |
#4
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"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 |
#5
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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 |
#6
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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 |
#7
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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.... |
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