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# Thread: Drive train tooth count

1. ## Re: Drive train tooth count (By: Phil Burman)

What Tinker is driving at is known in chronometer circles as "reverse fusee". The chain from the barrel crosses over to the side of the fusee nearest the next pinion, instead of to the side opposite. As the chain unwinds to the larger end of the fusee, more and more of the side load on the pivots gets shared between the two arbors. This was known early on - something like 200 years ago.

Johnny

2. ## Re: Drive train tooth count (By: Tinker Dwight)

Originally Posted by Tinker Dwight
What ever ratio you might choose, the minimum
thrust on the main wheels pivot is still at the minimum when both
the second pinion and the cord pull down from the same side.
One can easily draw ones own vector diagram from this description.
Tinker Dwight
Hi Tinker, how is the first day of your holiday.

Thanks for the post, I did do the vector diagram and came to your above conclusion in post #27. I'm grateful for your effort and the addition to my understanding. It's another factor to keep in mind when juggling all the parameters that influence train layout.

Phil

3. ## Re: Drive train tooth count (By: Phil Burman)

Originally Posted by Phil Burman
Hi Tinker, how is the first day of your holiday.

Thanks for the post, I did do the vector diagram and came to your above conclusion in post #27. I'm grateful for your effort and the addition to my understanding. It's another factor to keep in mind when juggling all the parameters that influence train layout.

Phil
Hi Phil
It is always good to confirm my math. Even with a calculator and
knowing what buttons to push, I find that solving the problem in two
different ways helps to get the right solution.
I did it once with the sum of squares and then did it again the inverse tangent and
then cosine.
I got the same answer twice. Often a good chance I got it right.
I don't know where I got the 15% number and was not able to recreate it.
We are having a good trip so far.
I did back up, hit a tree and bent the rear bumper.
Tinker Dwight

4. ## Re: Drive train tooth count (By: Tinker Dwight)

Originally Posted by Tinker Dwight
.......................................
I did back up, hit a tree and bent the rear bumper.
Tinker Dwight
You just reminded me of when I did the same thing but might have gone one step farther.

About 45 years ago I had a friend with me and he needed to make a phone call. Soooo I pulled into a large shopping center parking lot & dropped him off at a phone booth (remember them?). I decided to back the car around while he was making his call and the car was stopped with a CRASH.

There were no cars in that entire area of the lot and I managed to hit the concrete footing for a huge, tall parking lot light. I destroyed the rear bumper on the ONLY thing that I could have hit other than the phone booth. At least I remembered where that was!

Originally Posted by Tinker Dwight
We are engineers, we don't need no stink'n instructions!
Tinker Dwight
I think we do need instructions!

5. ## Re: Drive train tooth count (By: Tinker Dwight)

Originally Posted by Tinker Dwight
..................................... assuming equal load on both ends.
Tinker Dwight
This just jumped out at me while reviewing this thread and I believe that this should be expanded on a bit.

When clock movements become worn, it is the pinion end of the arbor that has the most wear because the wheel it meshes with is trying to push it sideways. For this reason many designers of higher quality clocks try to keep the pinions and wheels close to each other and on one side of the movement. Having the pinion farther away from the pivot allows the arbor to have greater leverage to resist this sideways force.

Before I learned this, I often wondered why regulators often have plates spaced so far apart.

6. ## Re: Drive train tooth count (By: jhe.1973)

Originally Posted by jhe.1973
This just jumped out at me while reviewing this thread and I believe that this should be expanded on a bit.

When clock movements become worn, it is the pinion end of the arbor that has the most wear because the wheel it meshes with is trying to push it sideways. For this reason many designers of higher quality clocks try to keep the pinions and wheels close to each other and on one side of the movement. Having the pinion farther away from the pivot allows the arbor to have greater leverage to resist this sideways force.

Before I learned this, I often wondered why regulators often have plates spaced so far apart.
Yes, the pinion pivot end has the most load. Usually the second wheel is not only a high load
but has the most unbalanced load in the clock. This means if any location should have
a more robust pivot, it is likely the pinion end of the second wheel. Even on a cable with
the cable and second wheel pivot on opposite sides, the second wheel pivot end has almost
the same load as the main wheel that is ( on average ) more evenly distributed.
The second wheel being way off center sees the almost the entire load.
Tinker Dwight

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