[rescue] Big tape drives

[Dave McGuire]

On Tuesday, October 15, 2002, at 11:41 AM, Scott Newell wrote:
>>> That are 15400 W!? This is a _lot_ for a tape drive. In fact that is
>>> enough to power a smal supercomputer. (AFAIK the entire CDC Cyper 910
>>> in Munich that is running every saturday needs about that.)
>>
>>   The TU78 moves tape at 150 inches per second read/write, 400 inches
>> per second rewind.  And it's a vacuum-column drive.
>
> And it takes ~21 HP to do all that?  Whoa.

   Well, that's a documentation spec, so it's probably inflated...but 
even if it's doubled, that's still a fucking lot of power.

   I suspect the big deal is the acceleration requirements of the 
spindle motors to maintain good start/stop performance.  One way to 
ease motor acceleration requirements in a tape drive is to use some 
sort of tape buffering, either with tension arms or vacuum columns, and 
tension arms cause lots of tape wear.  At 150IPS, very tall vacuum 
columns are required to lessen the accel/decel demands on the spindle 
motors.

   Anyway, I wanted to check my memory so I went and grabbed the 
book...I was wrong on several of the specifics, but not by much.  The 
R/W speed is 125IPS (not 150), the rewind speed is 440IPS (not 400).  
The start/stop surge current is 80A (not 70) at 220V.  The steady-state 
current draw is 13A.

> That's as much juice as a fair sized vertical machining center needs, 
> as a comparison against machine tools.

   Yup.

     -Dave

--
Dave McGuire          "PC users only know two 'solutions'...
St. Petersburg, FL       reboot and upgrade."    -Jonathan Patschke