Log of February 2007 events
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Tuesday, February 13,
Tuesday, February 13
These are notes of the RAMAC Tuesday February 13rd meeting -
Next meeting February 27th.
Present were Al Hoagland, Dave Bennet, Joe Feng, Ed Thelen.
Note from Dave Bennet
For those not at today's meeting, I completed the RAMAC compressor project and took it to CHM today. Joe and I tried it after the meeting. At first it looked like bad news but it came out okay. It would not start on Joe's isolation transformer, which had a nameplate rating of 1 KVA, evidently not big enough to carry start current for the 3/4 hp induction motor. It started fine when plugged directly into the bus duct but but it put an "unacceptable," as in a high, level of noise on the read signal. Joe had the good idea of moving it to the edge of our area and plugging it into a floor outlet and the electrical noise went away. We have no idea whether the noise was radiated or conducted through the power line but as long as it went away it doesn't matter.
Acoustic noise is substantially reduced over that which comes from the small Sears compressor we had been using. The rest of the air setup is as it was and everything seems fine with function. So all's well that ends well. And my wife is pleased that there is one less project going on in the garage.
The compressor is an original RAMAC DeVilbiss two cylinder cast iron compressor, with an original air tank (rated at 200 psi working pressure), (probably) original GE motor, pressure gauge and safety valve. The safety valve has a nameplate pressure set of 100 psi, and when I tested it it popped open at about 105 psi - not bad I thought. The new pressure switch runs the compressor up to about 95 psi (as I adjusted it) then shuts off and restarts the compressor when the pressure drops to about 80 psi. There were two different types of compressors used on RAMAC. The DeVilbiss appears to have been the earlier one. Later RAMACs used a Bell and Gosset rotary unit. I don't know if the change was made concurrent with the introduction of the 10 mByte version of RAMAC or not.
There you may well have more information than you wanted on this subject.
Al Hogland asked for copies of patents 3,503,060 and 3,134,097
Printing these out got "interesting" - GOOGLE Patents seems to work better than www.uspto.gov - even though one page at a time - and the patents need 8.5x14 legal size paper.
The complete history of this RAMAC unit is not known. It may have been removed from service before going to Kingston, N.Y.
About 13 prototype units were removed from service due to troubles with wire relays. This unit, with out active electronics, is called a "half RAMAC".
Joe Feng reported that:
- he has stored scope images of more than half of the 10,000 sectors on this RAMAC - he can see two or three separate writes/overwrites of data - misalignments of data tracks - from different head alignments, different heads? - different slivers of sector start pulses - residual signals of overwritten data
There was quite a discussion of the apparent longevity of magnetic signals on this disk. Marcel ??? got an award for a new magnetic/binder formulation when? Aluminum oxide? Is disk technology, with hard binder, as opposed to flexible magnetic tape binders, inherently longer lived than tape technology? This is a link to Time*Humidity*Temperature degradation of magnetic tape