Hi Certainly a lot less backlash than the mechanical trimmer. There would still be some minor issues due to the internal heat flow changing as you rotated the part. No obvious issues with wear out. Probably could use some kind of belt to drive a large wheel to get around the gear train. Six foot diameter wheel driven by a 1/4" shaft should do pretty well.
Bob On May 2, 2010, at 9:24 PM, Neville Michie wrote: > Or you could rotate the whole OCXO on flexible leads through 180* and let > gravity tune your frequency. > The range might be small, but an occasional tweak on the frequency control > might be acceptible. > cheers, Neville Michie > > > On 03/05/2010, at 6:00 AM, Bob Camp wrote: > >> 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. > > > _______________________________________________ > 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.
