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RE: Tape drive motors

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In Reply to: RE: Tape drive motors posted by Scholl on April 02, 2023 at 05:38:04

Hi
I searched Google Patents but only found the Canadian patent for that.
The evolution of that was the commutated voice coil idea, then the Servodrive (the rotary version of the commutated coil), then the full rotary woofer and motor, the Phoenix Cyclone was an example made under license.
The attached picture was part of a "large" one of those full rotary drivers. 8 of these were placed at the exit of a 20 foot diameter cooling fan at the Redondo Beach nuclear power plant to cancel the low frequency fan noise.
Each of those had the displacement of 6x 18 inch woofers moving an inch peak to peak. The noise canceling system was in place for about 2 weeks before the earthquake knocked the power plant off line for good

https://patents.google.com/patent/US4531025A/en?q=(tom+danley+subwoofer)&oq=tom+danley+++subwoofer&page=1
https://patents.google.com/patent/CA1199875A/en?q=(tom+danley+subwoofer)&oq=tom+danley+++subwoofer&page=1
https://patents.google.com/patent/US4763358A/en?q=(tom+danley+subwoofer)&oq=tom+danley+++subwoofer&page=1
https://www.diymobileaudio.com/threads/phoenix-gold-cyclone-12-in-rotary-subwoofer-rare-working.453370/
I was thinking, i might have something like the motor you mentioned, I think it was from a very old hard drive memory, i mean old!. This was maybe a 6 or 7 inch square alnico magnet and a 4 inch voice coil made of very heavy rectangular wire. There were two rods that guided the VC. Somewhere in my old house i have that and intend to pick it up when i finish moving.

Edits: 04/06/23

Follow Ups:

PS: Thank you for the links. - Scholl 12:59:08 04/09/23 (0)
This is a good resource for those who might be searching these ideas and concepts.
RE: Tape drive motors - Scholl 06:38:28 04/09/23 (1)
"I was thinking, i might have something like the motor you mentioned, I think it was from a very old hard drive memory, i mean old!. This was maybe a 6 or 7 inch square alnico magnet and a 4 inch voice coil made of very heavy rectangular wire. There were two rods that guided the VC. Somewhere in my old house i have that and intend to pick it up when i finish moving."
Yup, those are the beasts. I gave mine the scrap man. I have small neo magnets from DEC RA81 disks that are much more powerful.
Back in the 90s early 2000s these types of things were very expensive to build. I was thankful for the scrap computer parts they were ahead of audio designers.
The RA81 heads were moved by a moving magnet angular actuator. In the picture if you look carefully into the gap the thin copper strip on the left was the coil and the thin white strip on the right are the magnets. The coil is a oval "race track". The magnets are glued to the rotator and rotate to the current in the fixed coil. A DIYer could build these today, maybe leverage a modern brushless DC motor. "PowerSoft has a subwoofer that basically flattens that design principle into a linear design.
Once I built midbass using AE TD15S and manifold mounted subs using AE IB15s I gave up experimenting with this junk. I have far more low distortion high output bass than I can use.

Edits: 04/09/23 04/09/23
- RE: Tape drive motors - tomservo 10:53:59 04/10/23 (0)
  Hi
  If you wanted to get a feel for what your motor would be if converted to linear motion (like a belt assembly) or rotary radiator, if you measured the torque per current you can do it. A loudspeaker motor has a BL and Rdc, a figure of merit is BL^2/Rdc. It is how many meters of conductor times gap strength T AND it is how many Newtons of force per Amp the motor produces.
  
  For the rotary system, those motors are often rated in how many ounce / inches of torque they produce per AMP.
  IF one had a motor that produced 10 oz/in/AMP, if one had a 1/4 inch radius instead the motor produces 80 oz of force.
  Anyway, looks like a cool motor!
RE: Tape drive motors - claudej1@aol.com 08:29:23 04/08/23 (0)
Wow. Cool stuff. "Finish moving" is a relative term I'm practicing now. LOL.

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