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What Should Amplitude Be??


Watchdog

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I had taken this seiko apart week or so ago . Clean oiled... I wasn't happy with the fact that the mainspring will run down within about 4 hours after taken it off. I wonder,what esle should I look for? I had taken the mainspring out,it wasn't set,looked good. So I clean and oil it , greased the walls of the barrell. Any ideals?

Does anybody know the lift angle , and what amplitude I should be trying to achieve ?

Seiko 7s26-0040

post-404-0-98466000-1417285170_thumb.jpgpost-404-0-91202100-1417285191_thumb.jpg

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I believe the lift angle is 53 but my machine usually detects 52. The amplitude is not too bad but theoretically should be between 275 and 300. With that said, if you get a little less than 275 in an old used watch you are OK.

 

The reserve time of 4 hours is either the main spring slipping or broken. Maybe the wrong lubricant or too much was applied if not broken. Just in case check also the click spring (it is a click and clickspring in a Seiko) and the wheels interacting in that section.

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Lift angle for the 7S26C is 52 degrees, I would assume that it is the same for earlier incarnations of the 7S26.

 

I believe that Seiko's tend to have slightly lower amplitude compared to Swiss calibres but I would expect to see in the region of >260 degrees in the horizontal positions (dial up, dial down) with no less than 240 degrees in the vertical positions, no more than 25 degrees difference between horizontal and vertical for a movement in top order. 220 to 235 degrees does seem a little low.

 

You should also be getting around 40 hours power reserve from fully wound.

 

As this movement does not hand wind, how are you ensuring that you are testing from fully wound? A few hours on the wrist may not be sufficient for a full wind unless you are very active. Also, when you reassembled it did you put the winding rotor back in the correct orientation? Believe it or not this makes a difference to the efficiency of the Seiko magic lever auto winding system.

 

If you are testing from fully wound then you would seem to be losing power somewhere.

What did you use to grease the barrel wall (and how much did you use). The wrong grease here can result in the bridle slipping way too soon leaving you with less torque (lower amplitude) and shorter power reserve. Also excessive frictional losses in the train can have a similar effect, how free running was the train when you put it all back together? Did you get the escape wheel to recoil at all before you installed the pallet fork? Did the pallet fork snap across smartly from side to side with only a tiny bit of power in the main spring? What oils did you use in the train and for the pallet jewels?

 

If all of the above is as it should be then is it possible that the wrong mainspring has been installed at some time? Even though it isn't set I would probably start with a new spring (assuming no undue losses in the train) and then go from there.

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I set the lift angle to 53 degrees for the 7S26A, the 6R15 uses 52 degrees which might also be for the 7S26C as Marc just said. I got these figures from the attached file (7S26), which I'm led to believe are identical to the 7S26.

 

_nh25_26_TG.pdf

 

From my notes I got:

 

"New watches we look around 270 degrees. With no more than 30 degree drop from dial up to a horizontal position. In other words your dial positions dial up and dial down should be within about 5 degrees and from dial up / down to vertical (crown down 9 down etc.) losing not more than around 30 degrees. Vintage watches will vary considerably pending wear and movement design. You cannot expect an unjeweled watch to perform like a jeweled watch. Manufacturers and calibres vary a bit but this is a "general rule"."

 

Which I believe I took from somewhere else.

 

Hope it helps,

 

Bob
 

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I have seen elsewhere suggestions that the 6R15 is pretty much the same as the 7S26, having not handled a 6R15 though I wouldn't like to say.

 

Below is the tech manual for the 7S26C which gives details of lift angle and the correct way to set up the rotor as well as oiling requirements.

 

7s26-36Ctech.pdf

 

I would have uploaded this before but I hadn't figured out how to attach files  :unsure: didn't occur to me that it was the same as attaching pictures  :blink:

 

Beer needed I think :beerhat:

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Hi Mark

 

You are correct about the lift angle of version C which was the last of the 7S26 releases but the previous ones (identified by markings on the rotor and the small 1.20 Philips dial guard screw, absent on the C release) are related/identical to the NH25/26 which have the lift angle at 53 degrees.

 

The 6r15 is equivalent to the NH15 which is a smaller caliber closely related to the 4207 and do have a lift angle of 52. As per the attached specs.

 

nh05061516_TG.pdf

 

I believe the version for the specified case is more related to releases A and B of the 7S26 movement - mostly A -- considering its age but I might be wrong in this assumption.

 

Cheers

 

Bob

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You folks are truly appreciated ! Thank you!!!

Where do ya'll find the tech charts for these watches?

To answer the question about the grease I used in the barrell ,it was MR-1 and 9010 on the jewels..

I did have back lash on the escape wheel and a nice kick to the pallet fork.

You know, yall got me thinking..... I want to double check my arbor end-shake, and order a new main spring.

This movement is new to me. ......

Someone asked how did I wind it before timing check, I wound the barrell with a screw drive...

Thank you !!

Phil

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Hi Bob,

 

thanks for the info, this is a question that has exercised the grey matter somewhat this morning.

 

I have in the past done some pretty exhaustive web searching to try and track down any published tech data on the 7S26A/B movements and only ever found one document from Seiko which completely fails to mention lift angle.

The only Seiko published data that I can find which includes this information is the one I uploaded above.

I had always assumed (and assumptions are always dangerous) that the upgrades from A to B to C were more to do with changes in materials / production processes / commonisation of non-critical parts between different calibres etc. than they were design parameters such as escapement geometry, which is why I've always been quite happy to use the published lift angle for the C variant as a reference for the A and B movements.

 

I have in my parts / projects stock a 7S26A so this morning I thought I'd have a go at working out the lift angle using a technique I had seen on a YouTube video. The idea is to put just enough power into the main spring to get 180 degrees of amplitude (which is supposedly easy enough to judge by eye!!), and then put the movement onto your timing machine and adjust the lift angle on the timer until it reads an amplitude of 180; simple!!......

 

Ha!!!! not so simple.....

First of all judging 180 degrees by eye on something oscillating at 21600 bph seems to be a bit of an acquired skill that I have as yet to acquire.

Secondly, my 7S26A is in desperate need of a clean and service (that's why it's in the parts / projects box) and probably as a result of all the c**p it has picked up through not being in a case for a few years, the amplitude varied by as much as 20 degrees either way over a cycle of about 30 seconds. I gave up on that one but may have a play with it again once serviced.

 

I resorted to plan B, which was to work out just how significant the difference in reported amplitude would be between a lift angle of 52 degrees and 53 degrees on the Timegrapher, I wish I had done that to start with.

Feeding the reported amplitude of 235 degrees, and a lift angle of 52 degrees into the equation that svorkoetter publish in his DIY timing machine thread (many thanks Stefan) I worked out what the lift time (which is what the Timegrapher actually measures) was. Plug this back in to the equation but substitute 53 for 52 for the lift angle and provided I haven't completely goofed the maths (a distinct possibility) you get an amplitude of 240 degrees.

 

What have I learnt from this?

1. in the grand scheme of things, using a lift angle value that is out by 1 degree either way makes a relatively insignificant difference to the reported amplitude.

2. my brain hurts when I do maths.

 

@Watchdog

 

Did you also use 9010 on the pallet jewels? If so you may be losing a little amplitude there as it is a bit heavy for that, you'd be better off with 941.

However, your biggest issue I think is the poor power reserve. MR-1 should be fine for the barrel wall and if you wound it with a screwdriver then you should have got a full wind no problem.

The recoil in the train and the snappy pallet fork response does suggest that the train is free enough so for my best guess the main spring and as you say the arbor would be the place to look first.

 

For Seiko technical data there is a 3 or 4 page thread on the SCWF of just tech sheets.

Link here: http://www.thewatchsite.com/14-user-manual-technical-manual-casing-guide-downloads/15-seiko-calibers-technical-repair-manuals.html

 

Mark I hope it's ok to post a link to another forum, if not then please remove.

 

 

 

Marc

 

p.s.

apologies for the protracted ramble but I've just noticed that it's my 100th post and for some reason that makes me feel good about it :-)

 

p.p.s.

@Watchdog, probably better off with 9415 for the pallet jewels not 941 which is for higher beat movements.

Edited by Marc
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Thank you Mark for the outstanding research. I figured it was not much of a difference being off 1 degree and you have confirmed it. I was just going by the tech sheets I had. I do service a lot of Seikos so I figured I would put in my 2 cents. Much appreciated all you did!

 

 

Watchdog, is that some sort of bike grease? I was googleing it but only came up with "bike grease". Please, let me know what it really is. I thank you in advance -- since I'm not familiar with it.

 

I usually do the true Seiko recommended lubes: S6, S4, Moebius 9010 with the twist that I "paper rub" the main spring lightly with Moebius 8200 after cleaning and put Moebius 941 (which is for 28000 bpm or less watches) in the pallet fork jewels. Seiko silicon grease in the gaskets for sealing. Those Seiko lubes can be had from ebay and some other vendors, not too easily though.

 

Cheers,

 

Bob

Edited by bobm12
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MR-1 is what I think Rolex uses ...?? Pretty sure anyway on the barell wall..

Yes, Bob that was how I did the mainspring. Without the tech guide up till now did I have a clue. But now that I know,thats proably where some of my problems lay.. I'll look into the 9414. Marc, that I know I didn't use. After the above help,my plan is to redo the job,check end shake and reoil with the proper oil..

Thank you guys !!!

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Thanks Bob for the correction, 941 for lower beat movements, 9415 for higher beat movements, although there does seem to be a lot of confusion about this. The BHI for instance says 941 for lower beat and 9415 for 28,800 or higher, yet Cousins state that 941 was specifically developed for movements running at 28,800 or higher and high grade quartz movements.

To tell the truth I use 941 across the range and don't have any issues.

 

MR-1 is indeed a barrel wall breaking grease and is I believe a Rolex lubricant.

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