Hi An R-390A (or an not an A) has a lot of examples of how to do anti-backlash gear trains. Pretty tough to do on a one up fab from scratch in the basement basis though.
Lots easier to kludge in a low capacitance tuning diode ..... Bob On May 2, 2010, at 3:54 PM, Bruce Griffiths wrote: > Bob Camp wrote: >> Hi >> >> A coupe of issues with mechanical servo tuning: >> >> 1) It wears out the tuning capacitor pretty fast. They are designed for a >> limited number of adjustments. They loosen up with a lot of tuning and this >> degrades their stability. >> >> 2) It would be much easier to tear apart the mechanical tune OCXO and put in >> a tuning diode than to rig a thermally isolated high resolution servo stepper >> >> 3) Mechanical tune arrangements normally have backlash. That's not an issue >> as long as the servo only goes one way. It becomes a real pain to correct >> for each time you reverse direction. >> > One solution to which is to add (in addition to the servo motor) a torque > motor to preload the gear train so that the same flank of each gear tooth is > in contact for both directions of rotation. Zero backlash drive reduction > systems are also available at some considerable cost. > >> 4) Making a mechanical setup with a minimum step below 1 ppt is going to be >> more than just a simple stepper. A gear chain based system will be pretty >> exciting to work up. Backlash in the gears will add to what ever you have in >> the tune it's self. >> >> 5) The tuning on the OCXO may not be monotonic. That's especially true if >> you do indeed run the trimmer at a higher resolution than a normal human >> could adjust it. Tuning reversals tend to drive servo loops a bit crazy. >> >> None of that says that it can't be done. All it says is that it will be hard >> to do well. >> >> What kind of accuracy are you trying to obtain? >> >> Bob >> >> > Bruce > >> On May 2, 2010, at 3:18 PM, ch...@yipyap.com wrote: >> >> >>> That is a really cool picture. >>> >>> Can I be like you when I grow up? >>> >>> >>> I've figured out which of these silvered modules >>> in this Schomandl sig gen is the oscillator (the one that >>> got warm). I have to figure out if it is voltage adjustable >>> in some way. >>> >>> Does anyone use mechanical adjustment with a servo, >>> gear train and microcontroller? >>> >>> I did hear all of those good advisers telling me to >>> buy the Thunderbolt. But I already have these pieces >>> so... >>> >>> -- >>> Chris >>> w0ep >>> >>> >>> Niels Lueddecke wrote: >>> >>> >>>> You see? Don't do it, don't even think about starting. >>>> Go buy a trimble thunderbolt, it will save you LOTS of time! >>>> http://www.dulli.org/pics/20100502%20-%20Clock.jpg >>>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
