roy@phri.UUCP (Roy Smith) (12/26/85)
A while ago, in <2038@phri.UUCP>, I asked about peoples' experiences with small (i.e. 300 foot) reels of mag tape. The last time I used them was many years ago on a TU-10. As I said in that article: > [...] it kept loosing vacuum and such. DEC mumbled > something about the reels being too light and the hub > motors expecting greater rotational inertia. We didn't > really believe them but they never solved the problem > and eventually we gave up. What follows is a condensation of the responses I got. My summary is that there doesn't seem to be a clear consensus on whether 300' reels are OK or not. I plan on getting some to try on our TU-80, but only from somebody with a "no questions asked, money-back" policy. Comments added by me are in [brackets with my initials -- RHS]. ---------------- From: cbpavo.cbosgd.ATT.UUCP!mark (Mark Horton) I used to have problems with 600' reels at Berkeley on a TE16 - they just wouldn't load. I haven't had any such problems on our TE16 here, but I haven't used 600' reels all that much. [We use 600' reels all the time on our TU-80 with no problem -- RHS] ---------------- From: ihnp4!tapa!larry (Larry Pajakowski) We have the same problem with 600' reels also on our TU10 (I think but it's 45ips for sure). The solution is simple but annoying. Place your finger on the reel while pushing the "load" button. After awhile it gets to be easy. I believe DEC is correct about not enough mass on the hub. [I don't remember our old TU-10 complaining about 600' reels any more than it usually did with any other (larger) size -- RHS] ---------------- From: rochester!rocksvax!z@columbia.ARPA (Jim Ziobro) Our TU-78 handles 150 foot (software distribution) tapes with no problem. Of course those tapes by their nature only get mounted once or twice. ---------------- From: vax135!celerity!barto (David Barto) I use the 300' tapes on both a Kennedy tape drive on the Vax 750 and on the Celerity Accels Cypher tape drives. I have had only problems on the 'auto-loading' Cyphers. (They suck air to grab the end of the tape, REALLY!) The cyphers have a hard time loading ANY tape smaller than the standard 2400' reel. ---------------- From: philabs!nyit!rick (Rick Ace) All the tape drives I have met were capable of reading and writing small reels just as well as the big ones. Getting the reel loaded on the drive is another story, though; many auto-loading drives (e.g., TU77) are optimized for 2400' reels, and the procedure gets a bit more manual if you want to load a smaller reel. We used to have some older tape drives on an 11/70 here a few years ago. I think they were TU10s, but the memory is fading fast (the front panels had rocker switches on them). Maybe your equipment *is* getting too old! [I *like* rocker switches -- RHS] ---------------- From: pesnta!pesnta!amdcad!uiucdcs!carey We have had problems with Kennedy 9400 drives losing vacuum on tape that has a thinner mylar backing than standard. The tape doesn't have the rigidity to hold the vacuum. Also you must be sure the vacuum column itself is clean (wipe the dust and oxide off the sides). I don't know the brands of tape that use this thinner backing, but it is usually a cheaper brand. We have been unable to use this kind of tape, because it won't load properly. The reels don't weigh that much, I find it hard to believe they have that much inertia -- after all when the tape is near the end of the reel, with 300 feet left, it would weigh the same as a 300 foot reel. [I'm not sure, but I think the only tapes that have thinner mylar backing are the 3600' reels. 1.5 mil is standard; the 3600's use 1.0 mil. I don't really see much point in using them since they cost more per foot than 2400' reels do. To do, however, cut down on tape handling and storage space (and postage, if you mail them), and I suppose some people find them worth the price -- RHS] -- Roy Smith <allegra!phri!roy> System Administrator, Public Health Research Institute 455 First Avenue, New York, NY 10016