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Too much amplitude - best (easy) way to stop rebanking ?

mikepilk

By mikepilk
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mikepilk Distinguished Member

mikepilk

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Just rebuilt my first Russian movement, a Poljot Cal 2409 - not bad quality !

Usually I have the problem of too little amplitude, but this fired up and started rebanking. 

I fitted a new mainspring of the correct strength (the old one measured the same size as the recommended one from Cousins).

I wonder if they were assembled using thicker oils ? (I used my usual 9010,  D5, 9415)

I was hoping a drop of oil on the upper pallet staff jewel would dampen it enough, but as you can see in the pic, this one just wants to go !

I don't want to put another mainspring in such a cheap movement, so I guess, run the pallet jewels/escape wheel dry, and oil both pallet staff jewels ?

 

 

20191013_162748.jpg

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jdrichard Distinguished Member

jdrichard

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Just rebuilt my first Russian movement, a Poljot Cal 2409 - not bad quality !
Usually I have the problem of too little amplitude, but this fired up and started rebanking. 
I fitted a new mainspring of the correct strength (the old one measured the same size as the recommended one from Cousins).
I wonder if they were assembled using thicker oils ? (I used my usual 9010,  D5, 9415)
I was hoping a drop of oil on the upper pallet staff jewel would dampen it enough, but as you can see in the pic, this one just wants to go !
I don't want to put another mainspring in such a cheap movement, so I guess, run the pallet jewels/escape wheel dry, and oil both pallet staff jewels ?
 
 
20191013_162748.thumb.jpg.5b3c172aeb7c0ce5ff7c11313bde9f15.jpg

That is crazy good amplitude. You could add a bit of weight to the balance and see if you can still regulate it.


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clockboy Distinguished Member

clockboy

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Are you sure its over banking. If it is the correct mainspring then oil viscosity will make little difference. I would check the pallet folk for loose pallet stones and also the folks have not been distorted. Maybe the banking pins are distorted.

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mikepilk Distinguished Member

mikepilk

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1 hour ago, clockboy said:

Are you sure its over banking. If it is the correct mainspring then oil viscosity will make little difference. I would check the pallet folk for loose pallet stones and also the folks have not been distorted. Maybe the banking pins are distorted.

Just looked under the microscope and I can see the impulse jewel get close to the pallet fork. The banking pins don't look distorted.

Didn't notice any lose pallet jewels. I'll check.

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praezis Super WRT Addict

praezis

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Sometimes this is the "reward" for cleaning well. 
If you do not want to change to a thinner mainspring (the usual remedy), you can open the banking pins a bit. This will take more energy from the escapement during unlock.

Frank

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Tmuir Distinguished Member

Tmuir

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21 minutes ago, praezis said:

Hi CB,

can you explain more detailed, how to distort the banking pins for higher amplitude?
Sometimes I would love to apply such distortion...

Frank

I think you just need to hit them really hard with a hammer to 'improve' the amplitude. :D

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mikepilk Distinguished Member

mikepilk

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2 hours ago, praezis said:

Sometimes this is the "reward" for cleaning well. 
If you do not want to change to a thinner mainspring (the usual remedy), you can open the banking pins a bit. This will take more energy from the escapement during unlock.

Frank

This is the first movement I've cleaned since getting my stereo microscope. You see so much more dust! So everything was spotless and carefully oiled. 

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mikepilk Distinguished Member

mikepilk

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1 hour ago, yankeedog said:

Double check your lift angle. I think the poljots are in the 42 to 46 degree range.

Good point @yankeedog. I could only find the lift angle for the 26xx which is 51. A bit of googling has turned up 42 deg for 24xx. That will knock the reading down quite a bit. 

Also the beat error was 5.4ms, I wonder how much effect that would have? 

Edited by mikepilk
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mikepilk Distinguished Member

mikepilk

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23 hours ago, clockboy said:

Are you sure its over banking. If it is the correct mainspring then oil viscosity will make little difference. I would check the pallet folk for loose pallet stones and also the folks have not been distorted. Maybe the banking pins are distorted.

I think you could be right @clockboy

With the correct lift angle of 42 deg, I'm seeing about 280 deg amplitude.

At 278 deg it's fine, but as soon as it hit's 280 the problem starts. I can't see any coils sticking, but guess that must be the problem ?

I'll clean the hairspring and re-check the jewels.

(I did a de-mag)

The jewels are well stuck in - the Russian have been generous with the glue !

So it must be a sticking hairspring?

20191014_172208.jpg

0001.png

Edited by mikepilk
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rodabod Distinguished Member

rodabod

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Looks like typical banking to me. Crude options for reducing amplitude are heavy oil (like D5) on the balance jewels. Or you could even oil the pallet pivots to make it sluggish. 

 

Better option is a lighter spring. 

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AndyHull Distinguished Member

AndyHull

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38 minutes ago, rodabod said:

Looks like typical banking to me. Crude options for reducing amplitude are heavy oil (like D5) on the balance jewels. Or you could even oil the pallet pivots to make it sluggish.

This is pretty much how every HMT I've purchased "fully serviced" from India arrives. Invariably they have low amplitude and appear to have been lubricated with lard. Some are filthy, and obviously have never been serviced, but others are relatively clean, but over oiled with some unidentified *stuff* of dubious origin.

image.png.28e113034ebb257f09498bdd40efec32.png

 

The one I just looked at this evening, in the trace above, went from around 150 degrees to between 230 and 240 simply by cleaning and re-oiling it, and will probably improve further overnight, so to go the other way, try rodabod's suggestion.

Before you fill it with tar though, I would remove the balance and give it a good close-up inspection. Particularly the hairspring, but also check the shock spring is correctly fitted. If you have access to another balance, try that.

Edited by AndyHull
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