ATMOS - Poising the fork

zygo

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May 29, 2008
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I've repaired quite a few Atmos clocks for people over the past few years, following the guidance provided in the usual JlC Notes and Gerry Jaeger. Until now, checking the poise of the fork has been simple because every test shows near-perfect poise every time. Now Jaeger describes how to check but not how to correct the fork if it is not poised and this month I have one such example. The fork wants to come to rest in a near horizontal position.

Clipping the tail to lighten it sounds a bit drastic! But adding weight to the top of the fork sounds even worse.

What are other members doing to correct the poise if it's not right?
 

TQ60

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Sep 15, 2016
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Thought the fork should be up so weight added to tail.

But we are talking very tiny maybe if nothing is bent.

Check first to insure nothing is bent causing shift in center of gravity as we must assume it worked from the factory and if no marks of abuse then it could be a person who eats bananas and walks on knuckles may have worked on it before.

If one must add weight one can TEST it by adding grease or other sticky stuff to the tail with a tooth pick then confirm function.

If that corrects the clock then a drop of glue can be used but we thinks there must be something causing it.
 

zygo

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Thanks TQ60 but although the tail is down when fitted to the movement, the poising test shows that the fork side of the pivot is the heavier side, so it hangs upside down during testing. If you think about it, that's what you'd expect, given the way it's designed to function.

@atmos repairers: how do you adjust the fork for correct poise?
 

TQ60

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You may be in error.

The fork needs to naturally rest in the upward position as there is nothing to hold it there.

cannot find our copy in the phone but basic test is a set of parallels or open vise to allow the shaft to rest and naturally rest.

If it is horizontal then it is going to rest to one side and not maybe run.

The amount of power at the roller is about the same as a single hair in an art brush.

something is wonky if horizontal.
 

zygo

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I should have added for clarity, it's Fig 5 that I'm working with.
(BTW TQ60, I do like some of the engineering stuff you've done on testing and refilling bellows but it all seems to end with no final certainty about success. I'll revive the thread for the conclusion....)
 

TQ60

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Sep 15, 2016
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Thanks for posting the page.

It was in winter when we did the last one and simply cannot remember for sure as we have eaten since then.

Either way horizontal is not right and it seems odd as it must have worked before.

But given it is horizontal it could be simple as the bend angles of the fork not correct causing the center of gravity to be off just enough to through it off.

If the fork is too close it's "moment" is lass than if it was farther awsy.

If it is placed back in the clock how does it look in relation to the roller.
 

TQ60

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Sep 15, 2016
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I should have added for clarity, it's Fig 5 that I'm working with.
(BTW TQ60, I do like some of the engineering stuff you've done on testing and refilling bellows but it all seems to end with no final certainty about success. I'll revive the thread for the conclusion....)
We have not messed with the bellows project since we got our 2 units repaired and charged.

The process is repeatable and consistent on testing.

We can pressurize to 50 psi without any issues for per charge testing and repair.

We are looking at using heat to excite the gas to increase pressure post repair testing clamped and submerged in water, did not think about it until after last repaired bellows was in the running click.


We did pick up a supply of aluminum disc's that we were going to make shipping clamps from and we got the process figured out but summer came and the yard started wanting chores done so no progress there.

We have looked around the web for other general Atmos things and found a clock servicing dealer who looks like good service but very expensive offering bellows charging for $150.00 and they have a photo of bellows with a pair of c clamps...not good.

We did see something similar on u tube that gave us the idea to proceed but we saw the clamps as risky to damage bellows so we made our tools.

The bellows is extremely strong as we have tested it with just air pressure.

forum prohibits self promotion so we have just shelved it until we get another one to do.

sourcing the gas is tricky but we have enough for a few.

I should have added for clarity, it's Fig 5 that I'm working with.
(BTW TQ60, I do like some of the engineering stuff you've done on testing and refilling bellows but it all seems to end with no final certainty about success. I'll revive the thread for the conclusion....)
 

TQ60

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Sep 15, 2016
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Well we had to go out to the shop and double check things...proven the old brain forgets things when we eat....

We should have looked before we posted above but the conversation of this got the brain fired up...dangerous situation.

We use as an example of power measurement for the Atmos fork is that of a single strand of hair in a tiny artist brush...very tiny amount.

If the fork of the OP is horizontal due to the fork end being light and there are no residue on the tail increasing it's weight then it could be possible for the center of gravity to be shifted just a tiny amount be the fork being too close to the pivot shaft.

The "moment" or distance from the fulcrum a force is applied to a lever could matter.

Our last clock had a monkey mess with it and the fork was bent and we did mess with it until is seemed to run fine and is has been running for a few months but the swing is short of a same model similar age unit that all we did was fix the bellows.

What if the fork is too high but within the window and not rub? This added length would lessen the power transfer due to change in moment as well as shifting the center of gravity which also could rob some power.

Result could be just a tiny almost zero reduction but reduction in power that would cause the swing to be reduced a bit...maybe:???:

This winter when it gets cool again we may play with this...likely just do some measurements or photos to compare.

The op can experiment since his has some problem and maybe prove or disprove these thoughts.
 

zygo

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May 29, 2008
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We have not messed with the bellows project since we got our 2 units repaired and charged. The process is repeatable and consistent on testing.

We can pressurize to 50 psi without any issues for per charge testing and repair. The bellows is extremely strong as we have tested it with just air pressure.
sourcing the gas is tricky but we have enough for a few.
So are you saying that you've pressure tested with air but not Ethyl Chloride (because obtaining it is difficult)? In my experience pressure testing with air is unreliable because the molecules of EC are much smaller than the gas constituents of air. Hence, a bellows that remains full of air, might not remain full when filled with EC gas.
Imagine a balloon, for comparison - filled with air, it stays up for a week or so. Filled with helium, it'll be flat in a day.
 
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TQ60

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Something like that.

We use air for troubleshooting as we have a small bike pump that works well for bench work...The 7.5 hp pump a little much...

The first one only took 15 psi to blow bubbles but last one took 50.

We understand about the molecule size as the same thing happens with automotive ac upgrades where the R134 transpires through the hoses.

However we are not concerned about the transpiration as the leaks are just bad solder flows and repair is re-flow with flux.

post solder we retest as before and if there was and leak at all the higher pressure would likely bubble.

but others advertise they use gas detection to check for leaks so we are looking at considering worst case scenario for environmental exposure so came up with heating the water to maybe 130 to 140 to insure above any expected exposure and looking for bubbles.

of course all of this is while caged
 

zygo

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Thanks for posting the page.

If the fork is too close it's "moment" is lass than if it was farther awsy.If it is placed back in the clock how does it look in relation to the roller.
Getting back to the original question on poising an Atmos fork I should explain that the one I checked is a spare that came with other stuff I bought from a retired Atmos repairer last year. In truth, while it looks ok, it might be damaged so not "tall enough" to hang upside down.
But the question remains, of "How do you adjust an Atmos fork that is out of poise"?
 

TQ60

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Sep 15, 2016
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Now it make sense...we do not know if it ever worked.

Given the clocks should be all consistent in their dimensions we may assume all such parts should be bent to same shape and should be interchangeable between clocks.

The factory should be making usable parts also base. On the above so we believe until discovered otherwise that there may not be anything to do that alters actual mass.

It could be that replacement parts are sent unfinished and this retired party could have got one but no clue.

Atmos man Mike may be able to answer that one.

We suggest using a calipers depth measurement probe to carefully measure the position of the top of the fork to the arbor on a running clock as that can safely be done with care then repeating same measurement on the suspect unit to see how they compare.

If same then that blows that idea and if not try bending it outward if short.

One also can use a tooth pick to dab on spots of grease or other sticky stuff just to see how much weight is needed.

Removing mass from the tail if needed would require very careful removal.

We would plane off material from the bottom edge with a very fine file so only the edge would be effected and not be noticed.

One could closely examine others to look for such work as well.

That is all we can suggest at this time.

John may have input as well...John?
 

new_hampster

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"What are other members doing to correct the poise if it's not right?
You will be surprised how a very slight change can substantially change the poise:

- Make certain that the tines of the fork are straight. I like to hold it with the tail facing me (photo) so I can visually line up the arbor with the top arm and head of the fork. If the arm and top tine are not exactly parallel to and inline with the arbor, some gentle adjustment of the fork head is necessary. The photo is rough, but this sample fork from my parts bin is slightly twisted.
- If the sides of the fork have been opened/closed, verify that the spacing of the side tines are equal from center and that the change was not made only on one side.
- On most forks (after 519), the opening in the tail of the fork can be adjusted. Be cautious with this one, too much moving back and forth and it will break. I would do this adjustment only if needed after the others are checked.​

And, yes, when poised properly, the tail should be up, not down.

IMG_0962.JPG
 
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