Shopsmith Forums

paulrussell wrote:I take very strong issue with this. Perhaps as a matter of terminology, but none-the-less I disagree.

If your argument is that redesigning a wooden clock to metal clock standards and dimensioning is detrimental, then I will agree.

However, tolerances and extreme precision are not detrimental to correctly designed wooden clock gears. How in the world could making something less in adherence to its design possibly be an asset?

A CNC cut wooden clock gear IS superior to most hand cut gears when the gears are properly designed.

The clock wheels you display in your post appear to be from, or are very similar to, the medieval "Verge and Foliot escapement" design clock. I saw many of these on display during a recent trip to Germany, and they were the origins of my interest in wooden clocks. The accuracy of these clocks was so poor, that they had only a single hour hand. The medieval woodworker had a different system than the woodworker of today. Today, we cut many parts in advance, to high degrees of accuracy and precision, and then expect them to all fit together as designed. The medieval woodworker, not having our abilities of consistent repeatability, had to make part 1, and then build part 2 to fit part 1, and so on and so on.

The modern wooden clock with a long pendulum, is a very accurate timepiece. The roughly hewn teeth shown above would have no place in their construction.

Take a look at the state-of-the art wooden clocks here: http://lisaboyer.com/Claytonsite/Claytonsite1.htm and see how many roughly hewn gear teeth are in evidence.

Me thinks you misconstrued the 'point'. Wood being a non-stable material will not react kindly to tight tolerances. Granted more precise fabrication of a wooden gear CAN be done today, but the 'design' MUST allow for the variability of the wood and include a 'sloppy fit'. This 'sloppiness' can be minimized by accurate fabrication.

The 'accuracy' of a clock is a function of its period dependent mechanism, not the gearing that follows it.

I for one find this discussion very interesting. The love of my life and I are mostly settled into our new downsized digs. We are enjoying the house but she is finding her sewing area too small and my shop as currently configured is just not workable. My love has her eye on my shop for a sewing room and we are considering getting bids on doubling the size of the garage with the new 500 square foot area dedicated to shop. Then of course there is a three season room adjacent to the new garage/shop addition that would need to be replaced with a kitchen/dining room addition. Whoa wait a minute what ever became of the sanity of a 2,000 square foot retirement home. Those dollars winging away make me nervous. No I am not willing to place a dollar figure on my shopsmith equipped shop. FJim

JPG40504 wrote:Me thinks you misconstrued the 'point'. Wood being a non-stable material will not react kindly to tight tolerances. Granted more precise fabrication of a wooden gear CAN be done today, but the 'design' MUST allow for the variability of the wood and include a 'sloppy fit'. This 'sloppiness' can be minimized by accurate fabrication.

The 'accuracy' of a clock is a function of its period dependent mechanism, not the gearing that follows it.

Again I think it is a matter of terminology. The words "tight tolerance" unfortunately appear to have different meanings to you and I.

If by "tight tolerance" you mean "a small gap" as in "too small a gap between two separate moving pieces in a wooden clock are bad because the wood can change dimension" then I will agree.

But in my world you don't have a tolerance problem. You have a design problem. In my career as an aerospace systems design engineer, responsible for defining interfaces, standards and tolerances, I have always interpreted "tolerance" to mean "the degree to which the product adheres to the design." And if the design is correct, a tighter tolerance may not make it better, but it will never do any harm.

In the event of a wooden clock gear, a proper design provides a clearance between the gear teeth of mating wheels large enough to accommodate the natural dimensional instability of the wood.

Regarding the accuracy of a clock being a function of the periodic mechanism, and not the gearing:
I agree, with the notable exception of the escapement.

However, and I won't claim expertise here, it is my understanding that the amount of effort required to turn the gears is IN PART a function of their teeth, and the more force required to turn them, the more weight needed to run the clock. And the more weigh required to run the clock, the more strain, stress and wear on the afore-mentioned escapement which in turn has a detrimental effect on the timekeeping accuracy. Again -- I admit this could be bull pucky.

However, and I reiterate: What I take issue with is "extreme precision can be detrimental in a wood works clock."
Nope. Bad designs can be detrimental, but not extreme precision. Extreme precision might not help, but it sure won't hurt.

Again, I realize I am making a big fuss about terminology, but this is an area where my anal-compulsive engineer side comes raging through.

paulrussell wrote:Again I think it is a matter of terminology. The words "tight tolerance" unfortunately appear to have different meanings to you and I.

If by "tight tolerance" you mean "a small gap" as in "too small a gap between two separate moving pieces in a wooden clock are bad because the wood can change dimension" then I will agree.

But in my world you don't have a tolerance problem. You have a design problem. I have always interpreted "tight tolerance" to mean "the degree of accuracy and adherence to the design." And if the design is correct, a tighter tolerance may not make it better, but it will never do any harm.

In the event of a wooden clock gear, a proper design provides a clearance between the gear teeth of mating wheels large enough to accommodate the natural dimensional instability of the wood.

Regarding the accuracy of a clock being a function of the periodic mechanism, and not the gearing: I agree, with the notable exception of the escapement. However, and I won't claim expertise here, it is my understanding that the amount of effort required to turn the gears is IN PART a function of their teeth, and the more force required to turn them, the more weight needed to run the clock. And the more weigh required to run the clock, the more strain, stress and wear on the afore-mentioned escapement which in turn has a detrimental effect on the timekeeping accuracy. Again -- I admit this could be bull pucky.

However, and I reiterate: What I take issue with the inference that a CNC cut gear is somehow inherently inferior to a hand-cut gear and is therefore detrimental to its performance.

I think we be on the same planet!

I do not understand why you think anybody inferred a cnc cut gear is in any way 'inferior' to a hand cut one. They have to be 'superior' to a hand fabricated one.

I concur with the exception that I was including the escapement within the realm of the 'period dependant' mechanism. Its force loses must be consistant or the 'period' accuracy is compromised.
I was guilty of ignoring the effect of any force variations caused by any 'resistance' of the following gear 'train'. Those variations must be overcome by the mainspring(or whatever IS driving it) so as to not alter the period. The force introduced by the spring(or whatever) and escapement must provide the same force into the pendulum(or balanced wheel or whatever it is called) with each cycle.

JPG40504 wrote:I think we be on the same planet!

I do not understand why you think anybody inferred a cnc cut gear is in any way 'inferior' to a hand cut one. They have to be 'superior' to a hand fabricated one.

Because of the statement:

horologist wrote: The point is (yes there is one) that conventional gearing and extreme precision can be detrimental in a wood works clock.

After re-reading several times, I doubt I read it as he meant it, and I will admit to making a bit of a mountain out a mole hill.

I suspect he meant something like "The point is that conventional gearing (of a modern metal-geared clock) design features such as tooth profile and tightly meshed gears can be detrimental in a wood works clock."

fjimp wrote:I for one find this discussion very interesting. The love of my life and I are mostly settled into our new downsized digs. We are enjoying the house but she is finding her sewing area too small and my shop as currently configured is just not workable. My love has her eye on my shop for a sewing room and we are considering getting bids on doubling the size of the garage with the new 500 square foot area dedicated to shop. Then of course there is a three season room adjacent to the new garage/shop addition that would need to be replaced with a kitchen/dining room addition. Whoa wait a minute what ever became of the sanity of a 2,000 square foot retirement home. Those dollars winging away make me nervous. No I am not willing to place a dollar figure on my shopsmith equipped shop. FJim

Wow, that is quite a chain reaction. I can really feel for you. I think we will probably end up with similar sq footage as we started with, but better distributed for our needs. For example the Mrs would like an open floor plan kitchen/dining/living room rather than three separate rooms.

paulrussell wrote:Because of the statement:



After re-reading several times, I doubt I read it as he meant it, and I will admit to making a bit of a mountain out a mole hill.

I suspect he meant something like "The point is that conventional gearing (of a modern metal-geared clock) design features such as tooth profile and tightly meshed gears can be detrimental in a wood works clock."

How about 'wooden gearing requires greater clearance to allow for woods dimensional instability and thus tight fitting gears are not "desirable"'.

The improved accuracy of cnc produced gearing reduces the need for the gearing to have excessively loose clearance.

Consider the mountain reduced to a mole hole again!:)

[quote="JPG40504"]How about 'wooden gearing requires greater clearance to allow for woods dimensional instability and thus tight fitting gears are not "desirable"'.]

I estimate that our disagreement coefficient to be less than or equal to +/- .00001 which is below the forum tolerance threshold, and thus can for all effective intents and purposes be considered to be an agreement of 100%

paulrussell wrote:I estimate that our disagreement coefficient to be less than or equal to +/- .00001 which is below the forum tolerance threshold, and thus can for all effective intents and purposes be considered to be an agreement of 100%

Amen (smib)!

paulrussell wrote:....The modern wooden clock with a long pendulum, is a very accurate timepiece. The roughly hewn teeth shown above would have no place in their construction. .

Wow!, Paul! Me thinks you need a little Whoa-back here! First take a look at horologists personal profile then read his posts. He is truly an expert in this field.

Secondly, I had a wooden clock - Ely Perry made - although a mantle clock, it kept perfect time from the late 1700's (I think) until the oak front that supported the weights, became oval from wear (approx 1980). The gears were certainly, and are still today, hand made and holding up fine. The clock has kept time while moved from Ohio to Illinois, to Montana and is now with our daughter in AZ. With only that one "oval hole issue" this clock is easily restore-able. After wound it will run, but loses time in a few hours. All it needs is a rub collar in the hole. The gears are loose and work just fine.