Wood clock questions

Discussion in 'Clock Construction' started by devils4ever, Apr 28, 2014.

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  1. devils4ever

    devils4ever Registered User

    Mar 28, 2014
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    I think I got the clock bug after repairing my mom's electric Seth Thomas clock last month.

    So, I'm considering making a wood clock since I'm much more adept at woodworking versus metalworking. Plus, I think they're cool.

    A few questions first.
    1. Should I make it from a kit or try to go for it from scratch? I think I could handle from scratch if I get more info on basics. Books on clock design that someone could recommend?
    2. Do the wood arbors rotate in wood plates? Or, is there steel or brass pivots in wood plates?
    3. Can a wood clock with a pendulum last 7-8 days between winding? It seems the kits require winding every day. I did see a kit with a harmonic oscillator movement that required only weekly winding.
    4. How about using ball bearings instead to reduce friction? Is that why wood clocks don't run very long or is the inertia of the much heavier wood gears?
    5. I don't want to start another war, but should I use Involute or Cycloid gears? Is it different from brass gears or wood ones?
    6. I prefer a free standing "grandfather" type clock, not a wall mounted one. Most kits seem to be wall mounted. I guess I could mount a wall kit in a frame, right?
    7. Can I expect accuracy of less than a minute a day?

    Thanks for all input.
     
  2. David S

    David S Registered User
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    Welcome D4ever. So far you haven't got any response here. Not sure if the wooden movement would give more advice. I know a recent thread by R.Crosswell was about a wooden movement repair. Perhaps you could post over there as well or PM RC to see if he could assist.
     
  3. Jim DuBois

    Jim DuBois Registered User
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  4. devils4ever

    devils4ever Registered User

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    Thanks, David. I don't want to cross-post. I'm sure there are rules about this, unless the moderators feel it should/could be moved.

    Jim, interesting website. I'll have to look at it in more detail. Thanks.
     
  5. GregS

    GregS Registered User

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    #5 GregS, Apr 29, 2014
    Last edited: Apr 29, 2014
    d4e,

    You will likely find this to be one of your greatest adventures. I can't say whether you should use a kit or build it from scratch. You will have to decide that after considering your skill levels, tools and time.

    Many that build there own wooden works clocks use hardened steel pivots in the arbors. They can run directly in the plates or in bushings installed in the plates. Your choice. The run time of a movement is dependent on a number of aspects and is generally designed into the movement and the case combination.

    You could use involute tooth profiles but since you are cutting wood and will likely have to make your own cutters there is little reason left to go that way. Unless you feel you can out do 300 years of fine clock making tradition use a cycloidal profile or as close as you can come.

    A long time ago I took a bet to build a wooden clock. I had never even seen a mechanical movement before (the internet didn't exist as it does today) so I checked out a lot of dusty books from the library and looked at the pictures and studied the drawings and text.

    My movement uses cycloidal gears, a graham dead beat escapement, tool steel pivots in nylon bushings (no oil) with a seconds beating pendulum. The winding arbor has concealed ball bearings. The whole thing is skeletonized in an open tall case with a relatively traditional tall case shape.

    The clock will run for about 7 1/2 days and will maintain about 1 minute per week, requiring adjustment with the changing seasons.

    Hopefully this will give you an idea of what you can do and a glimpse at some of the choices you have to make.

    Good luck and have a great time!
    Greg
     
  6. devils4ever

    devils4ever Registered User

    Mar 28, 2014
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    Greg,

    Thanks for the info and the inspiration!

    Yes, I was investigating some kits and some of them use HDPE plastic bushing and a few use ball bearings. Seems like a good idea to reduce friction to a minimum to keep long run times and longevity. I would prefer 1+ week run time. I suppose making the pendulum longer would increase runtime by making the whole thing run slower? I don't want a wall clock, but prefer a free standing case so a long pendulum would not be a problem.

    I think I would use my bandsaw or scrollsaw to cut the teeth. No cutter would be needed. So, cycloid teeth would be just as easy to cut as involute.

    I have to read up more on escapements to figure out the design differences with dead beat escapement. It seems more efficient.

    Great food for thought.

    I might be better off with plans or a kit to learn the basics of clock mechanisms, but I've always designed my woodworking projects myself.

    Doug
     
  7. Jim DuBois

    Jim DuBois Registered User
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    #7 Jim DuBois, Apr 30, 2014
    Last edited: Apr 30, 2014
    The first clock movement I made was a time and strike wood works made from a set of plans from where ever...I made it on a scroll saw, having glued the reasonably accurate drawings on the wood and then cutting away....ultimately, after a whole lot of messing around, filing, sanding, bad language etc. I got it to run a bit.....since then I have learned a bit more about gear cutting and clock movements. Just a couple of thoughts, the originals were not shaped as involute nor cycloidal, they were generally cogs rounded off on the ends.

    A wood works is generally not going to be a precision device....I recommend you do look into the originals as a starting point... getting good wood stock that is not likely to warp or shrink substantially is the first order of business. Quarter sawed wood is needed. I would not consider plywood in any case, others may disagree. I would also use a method of indexing the wheels and pinions for purposes of ease of construction and maintaining some degree of accuracy. Not required, but it will make life a lot easier...while building a wood works is not rocket science, it is more difficult than it may first appear. Getting one to run an hour was a major achievement in my case...then running a day was was a long way in the future while I discovered "kinda round and partially concentric and sorta flat" were not good enough. 8 day wood works become more difficult as stress on the various parts increases substantially....by a factor of about 8 strangely enough. Cross grain teeth tend to shear pretty easily when overloaded.

    Nearly 300 years ago John and James Harrison built some wonderful wood works clocks that ran 8 days and were quite accurate. They resolved some of the issues I mention quite nicely, so don't be afraid to do some investigation before making sawdust.

    In my case that first abortive attempt led me into many years of cutting gears and making clocks, but while I have cut a fair number of wooden gears since, I have never attempted to make another wood works movement.....

    Here is part of an auction description of one of the Harrison clocks

    "JOHN AND JAMES HARRISON, A HISTORICALLY SIGNIFICANT EBONIZED PRECISION LONGCASE CLOCK, ENGLISH, CIRCA 1726

    11 3/4 -inch restored dial with silvered chapter ring signed Jno Harrison, Barrow and set on a broken-arch wood dial plate, decorated with gilt stylized flowers and strap work, the center with putti and apertures for calendar and seconds, the arch signed James Harrison, a maintaining power lever on the upper right side, large wood plated movement with oak wheels, lignum vitae lantern pinions and bushes, grasshopper escapement with brass escape wheel and replaced adjustable cycloidal cheeks on the backplate, the strike with inside countwheel cut from the great wheel and top mounted bell, the replaced pendulum with brass and steel gridiron rod and calibrated regulation nut"
     
  8. devils4ever

    devils4ever Registered User

    Mar 28, 2014
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    Most of the kits I see use Baltic Birch for it's quality and stability. You feel quartersawn is more stable?
     
  9. Jim DuBois

    Jim DuBois Registered User
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    Nah, baltic birch plywood is more stable than quarter sawn anything, (other than lignum vitae, ebony, or rosewood) but I hate plywood in a clock. Literally hundreds of thousands of wood works clocks were built and successfully used for many years using quarter sawn wood, and it looks far better than plywood, IMO....that said, wood will move and expand and shrink with changes in humidity, plywood, less so...
     
  10. devils4ever

    devils4ever Registered User

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    I agree plywood isn't the nicest to look at.

    Did you use anything on the pivots into the plates? Did you use any plastic bushings or ball bearings?
     
  11. Jim DuBois

    Jim DuBois Registered User
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    I have used teflon bushings in some repairs but greatly prefer using bone bushings if bushings were originally used. I have also rebushed well worn wood works bushings with hardwood inserts, as do many repair folks. IMO ball bearings are an overkill for most wood works efforts. Steel pivots running in oak / cherry / mahogany plates work well, no exotic bushings or ball bearings generally needed.
     
  12. GregS

    GregS Registered User

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    #12 GregS, May 5, 2014
    Last edited: May 5, 2014
    I agree, while baltic birch is very stable it is visually boring. I wanted the stability of plys for my wheels but didn't want traditional plywood so I made my own. One layer of cherry, one of rock maple and the third cherry. Each layer's grain alternated 120 degrees.

    Pinions were made of all cherry plys and ended up more "plywoody" than I wanted.

    I'm not clear if you are designing something more artistic or something of a more traditional wooden works nature. Jim and others on this forum have much more experience than I and have always been great at sharing their knowledge. I chose to place my pivots in nylon bushes because: a) I didn't know any better :) and b) I wasn't sure how the pivot holes would hold up over time in the teak wood frame. Now, after almost twenty years, I think delrin would make a better bushing. Drilling small accurate holes in a course grained wood can be problematic.

    hope this helps!

    Image1.jpg
     
  13. devils4ever

    devils4ever Registered User

    Mar 28, 2014
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    Nice looking clock.

    I've never heard of plywood with 120 degrees between plies. I've always heard of 90 degrees. Was there a reason you used 120 instead of 90?

    I'm still trying to decide if I should go with plans, kit, or design my own.
     

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