Ring-type USM motors do not use a gear-train, they are built into the focusing helical, this covers some USM and AF-S and all HSM and SSM motors. Micro-motor USM (which really isn't USM, Sony's Silent AF Motor [SAM] terminology is more correct) uses a gear-train but really is just a conventional motor with non-conventional power as they discovered that micromotors are much quieter when driven by high-frequency AC.
-Adam On Thu, Feb 4, 2010 at 8:31 PM, Anthony Farr <[email protected]> wrote: > The short answer is to read this: > http://en.wikipedia.org/wiki/Ultrasonic_motor > > My understanding is that USM, HSM, SDM, etc, &s shouldn't be likened > to conventional electric motors with their armatures and brushes and > all the other stuff (I'm sure that's a technical term, I've heard an > engineer use it). In the most elegant examples the USM is an annular > linear motor that encircles the component to be shifted, be that the > focusing helix or the diaphram mechanism. In that application RPM > doesn't apply, because the total range of movement is less than 360 > degrees. A straight linear motor applying its movement in one > location could possibly shift the focusing group directly without a > helix, but I'm unsure if any USM systems are powerful enough to > directly move the lens without a helix or gear train to step up the > torque, and I couldn't be arsed to research it myself. And some USM > motors resemble a can motor (one configuration of a standard electric > motor) with an output shaft, but differ in that they excite the > rotation by a different method which has less mechanical resistance > and thus spins more freely. > > IIRC the first linear drive lenses were in the Rolleiflex SLX 6x6 > system, but don't know if USM was used. The technology ~was~ > available at the time. > > regards, Anthony > > "Of what use is lens and light > to those who lack in mind and sight" > (Anon) > > > > On 5 February 2010 10:27, Larry Colen <[email protected]> wrote: >> Do the motors turn at 900,000 RPM (15,000 hz * 60)? >> >> -- >> Larry Colen [email protected] sent from i4est >> >> >> >> >> >> -- >> PDML Pentax-Discuss Mail List >> [email protected] >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> to UNSUBSCRIBE from the PDML, please visit the link directly above and >> follow the directions. >> > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. > -- M. Adam Maas http://www.mawz.ca Explorations of the City Around Us. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
