GearHeads Corner

I'd love to make a fancy wooden-gears clock with exposed moving parts for show, but one that doesn't need winding and keeps accurate time by being driven by an accurate motor, preferably battery.  Standard clock movements likely don't have enough torque to drive a gear train.  I could use a stepper motor and an Arduino or Raspberry Pi, but that feels like overkill.  Ideally I'd like just a self-contained motor internally geared down to low RPM, but crystal controlled for stable RPM.  Does anyone have an idea?  Thanks!

Hi:

  If you build it from wood, and drive it with a motor, to make it accurate youll need a microprocessor
of some sort in the end if you wish it to stay accurate.Wood has too much tendancy to shift size and dimension
so one would have to have some sort of sync measure in there. (Usually the sync for a wooden clock is its maker when winding.).
  You can approach accuracy with a cheap arduino that simply pulses a pendulum to keep it swinging
while at the same time counting the swings though. Trouble with wooden clocks exposed to show motion
is that not much motion occurs other than the pendulum unless you get fancy with moving trains in there
to mark events. Second hands are non typical for that reason in a wooden clock.

  Of course all thats up to how inventive you are, I have seen some very cool wooden clocks, but most
dont run long, a day is a good run for most hobby build wood ones. Masters get a few days, but time running
before winding is an indication of how good one is. (Im not that good, I rarely get more than a few hours
from a good looking one, which is why I build tickers occasionally as once I remove the need to tell
time the actions can be as varied as I like..

Art


   

Art - Thanks!  I figured I'd get that answer, but I'm always hopeful.  Now I have to work up the ambition to get into a stepper motor with computer control.

Tim

Tim:

  All that having been said, a $1.00 ebay arduino uno with a 1$ ebay arduino stepper driver
will drive a clock fine, steppers are pretty cheap.. say $5.00 for a small one. :)

Art

there ya go... spending my money again.  :D

happy new year all
enjoying my AZ winter holiday
stay safe stay warm

It's not the money.  It's just that I'm a lot better with 3D printing and CNC milling than I am with Arduino control.  But I guess we're never too old to learn a new skill...

Hi Tim:

  I think youll find controlling a stepper with an arduino isnt all that hard.
If you get confused as to how Im happy to help when people have questions
even on an arduino control type questions. Ive controlled a few steppers
in my time.
  Making a small arduino control a stepper has lots of examples and open
source on line. I made a marble/sand drawing video awhile back and I still
have code for making them move aorund here somewhere. :)

YaNvrNo:

>>happy new year all
>>enjoying my AZ winter holiday

    Now thats just rubbing it in as
I just finished parking the snowblower
and spreading salt.  :) ,

Happy 2019..
Art

Most clocks that I design and build run at least 30 hours by design and half a dozen or more run a week on a winding.  Having said that they are as good barometers as they are time pieces - a change in the weather will upset them and often cause them to stop.  If I want to know exactly what time it is I look at my wrist.

John:

  And thats a tribute to your workmanship, getting a week on a wooden clock
identifies you as a craftsman in my opinion.

Art

A small AC synchronous motor should have plenty of torque to run a clock.  There should be enough power to keep a few gears visibly spinning all the time.

Here is the first one that came up in my search:
https://www.amazon.com/Electric-Permane ... B077YHG1F8

The rate is set by the line frequency which is supposed to be really accurate.

Steve

True, Sync motors are the gold standard and a lot less hassle.
 
Art

Steve - Wow, that looks like exactly what I want!  Constant RPM but no computer to deal with.  I'll look into that and check to see if it has any interesting relatives.  Thank you!

Tim

Tim,

Your query sparked my interest, so I ordered a couple of motors similar to these https://www.amazon.com/dp/B07G345S4H  Similar items are common on Ebay for around $3 each.

They appear to be very popular for running the turntables in microwave ovens.  The first test runs amazingly quiet with a lot of torque because of the gearing.  I may try to run one for a few weeks with a load to see if it stays quiet.

One huge disadvantage is labeled clearly in the image as CCW/CW.  The motor does not have a start capacitor to define the direction and will randomly start either clockwise or counter-clockwise.  Directional synchronous motors are a lot harder to find.  It should be a fun challenge to use a couple of one-way clutches and gears to force the output to run in one direction.

Steve

Just a thought,  If I truly wanted to have exposed wooden gears and an accurate time piece - I would look at running th clock backwards - by that I mean I wouldn't start at the great wheel but rather start at the seconds hand and let everything else follow it.  In a normal geared clock you start with a lot of power (weight) and through gearing slowly have less and less actual power at the gear tips.  If you apply very small power from an electric movement at the seconds hand you could let there rest of the mechanism just follow along.

I agree, and that was my eventual plan.  But I'm still hung up on motors.  The many synchronous motors I looked at would be perfect if it were not for the fact that they all have an average rated life that is much too short for a clock that runs continuously.  So now I'm looking at a pendulum movement with a hidden magnet in the base of the pendulum and a hidden electromagnet behind the front panel.  I would use a simple microcontroller to apply tiny tweaking pulses to keep the pendulum on track.