On Sunday 16 June 2013 07:00:20 Erik Christiansen did opine: > On 15.06.13 15:00, Charles Steinkuehler wrote: > > I've seen some setups where the filament loop closed a switch when it > > began getting 'tight' and triggered the spool to unwind a bit. > > But if that isn't what the "filament loop" always does, then do current > printer implementations just drag the spool with the filament feed > capstan, leading to loss of any filament loop soon after starting? > > I don't recall whether the old Pertec tape drives used switches or a > potentiometer (allowing PID control of the unspooling motor), but they > maintained a tape loop at speed. ... OK, I scuttled down to the garage, > and climbed the shelving - it's a slotted vane, plus microswitch on a > cam with about three detents. > Chuckle, now I recall where, back in the final days of using quadruplex 2" video tape, Ampex had such a loop control lashup. The tape was threaded such that there was a long tunnel, 2" wide, on the transport above the headwheel & capstan. This tunnel had a series of photocells, and a central vacuum port such that the tape was sucked into the tunnel, from both ends, and the photocels controlled the monster servo motors to maintain about the right amount of tape inside the tunnel. So the tape itself could move independently of the motors until the motors caught up.
They also had some monstrous drivers for the head wheel and capstan motors, which turned 14,400 rpms for the headwheel, and it had two startup modes, from an at speed headwheel it could give system locked video in 40 milliseconds, or from a stopped wheel, 400 milliseconds to get that headwhell up to 14,400 and phase locked to the house sync. It also had a power consumption of 25KW, and was a huge load on the AC. That was a major problem when the university shut down the chilled water supply which cooled the N.ETV building in Lincoln NE. > At the slow filament speeds, a couple of microswitches - one for "hurry > up", and one for below average speed, sound adequate. Yup, a pair of walls to guide the filament, and 2 of those roller tipped switches should do it. > Erik > > > - Not all systems support hard links > > Rolls eyes. Sure, but all _my_ systems do! UNIX dammit! > - Cameron Simpson, on mutt > ML. > > > ------------------------------------------------------------------------ > ------ This SF.net email is sponsored by Windows: > > Build for Windows Store. > > http://p.sf.net/sfu/windows-dev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> Price does not include taxes. A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
