Mainspring advice Orient Star 'Explorient'

[steve1811uk]

Hi, I need some advice on the mainspring for this watch. I am getting great amplitude in the region of 305 degrees at full wind that drops to around 285 after a minute or so. Positional variation is very good, delta of 6. Watch has been fully cleaned, lubed (including the mainspring) and regulated and is consistently keeping time to a rate of less than 1 second per day gain. However if I go on a vigorous walk for 30 minutes the watch can easily gain 5 seconds in that time (240 SPD!!! for that period). I think that I am suffering from re-banking. Incidentally I found that the barrel and arbor are identical to that of a Seiko 7005. The measured spring dimensions are 0.95 x 0.125 x 380 mm. The spring is flat and the barrel wall is lubricated with 8217 grease. The spring is flat and does slip after 6 turns or so. I am suspecting that the spring is too strong. What would you guys do in this situation? Try a different spring? In fact the GR catalogue suggests a spring of 0.95 x 0.11 x 400 for Seiko 7005 (GR2377X); would that end up too weak? Would I be better trying (GR2378X) 0.95 x 0.12 x 400 mm ?

[steve1811uk]

actually when I say 'vigorous walk' that is a bit of an exaggeration. My arm moves a bit as it does when walking but I am not waving it up and down as in a military march.

[clockboy]

I am a bit confused about the watch requires the new spring. I presume it is not a Seiko. If the watch is running OK but with variable timing issues it will not be the mainspring.

[steve1811uk]

1 hour ago, clockboy said:

I am a bit confused about the watch requires the new spring. I presume it is not a Seiko. If the watch is running OK but with variable timing issues it will not be the mainspring.

I believe that the mainspring is too strong so it causes rebanking at full wind. The Orient 48748 movement is very similar to Seiko 7005 in many ways. Pallet fork, escape wheel and barrel are identical to Seiko 7005.

[clockboy]

19 hours ago, steve1811uk said:

I believe that the mainspring is too strong so it causes rebanking at full wind. The Orient 48748 movement is very similar to Seiko 7005 in many ways. Pallet fork, escape wheel and barrel are identical to Seiko 7005.

It could be a Seiko movement. I have worked on a Rotary watch which was Seiko movement just with Rotary engraved on it. How does it perform with half a wind. 

[jdm]

2 hours ago, clockboy said:

It could be a Seiko movement.

It is not. Orient is a fully fledged Japanese watch manufacturer. They always used some Seiko technology until at some point Seiko Epson quietly bought them out. They never used mainstream Seiko movements and always maintained full independence in design, manufacturing (in-house movement to speak like a collector), and sales.

[steve1811uk]

2 hours ago, clockboy said:

It could be a Seiko movement. I have worked on a Rotary watch which was Seiko movement just with Rotary engraved on it. How does it perform with half a wind. 

Performs fine at less than full wind. At full wind it goes over 300 degrees and I think it rebanks as it gains 5 seconds in half an hour walking.

[jdm]

On 5/24/2021 at 12:38 PM, steve1811uk said:

However if I go on a vigorous walk for 30 minutes the watch can easily gain 5 seconds in that time (240 SPD!!! for that period). I think that I am suffering from re-banking.

That seems to be the same issue you had with another Japanese watch time ago? It never reached a firm conclusion.

Regrettably I can't offer exact advice on the matter except that in both cases perhaps the movement winds up a bit too much? Maybe not using any sophisticated anti-braking products could help. In other words you could try what happens doing the brisky walk with the watch unwound.

[clockboy]

14 hours ago, jdm said:

It is not. Orient is a fully fledged Japanese watch manufacturer. They always used some Seiko technology until at some point Seiko Epson quietly bought them out. They never used mainstream Seiko movements and always maintained full independence in design, manufacturing (in-house movement to speak like a collector), and sales.

OK did not know that. Just in my GR book no reference to Orient. To be honest a pic of the movement would be helpful.

[steve1811uk]

5 hours ago, clockboy said:

OK did not know that. Just in my GR book no reference to Orient. To be honest a pic of the movement would be helpful.

Orient 48748

[steve1811uk]

18 hours ago, jdm said:

That seems to be the same issue you had with another Japanese watch time ago? It never reached a firm conclusion.

Regrettably I can't offer exact advice on the matter except that in both cases perhaps the movement winds up a bit too much? Maybe not using any sophisticated anti-braking products could help. In other words you could try what happens doing the brisky walk with the watch unwound.

I had the issue again this morning after leaving the watch off all night, it gained 5 seconds in the first hour of wearing it, things such as getting dressed, washing hair, eating breakfast etc. pushed it over the edge. I'm going to try a weaker mainspring GR2377X (recommended for Seiko 7005) and will report how the amplitude compares.

[steve1811uk]

Well, I tried the GR2377X mainspring and early signs are that the rebanking issue has been solved. Amplitude horizontal after wear is 270 degrees and that drops to around 260 degrees after ten minutes or so (compared with 305/285 before). No big step gain in time even after walking for over two hours. Notes: bridle of GR2377X was only 0.13 mm thick compared with Seiko 0.18 mm (it slips nicely with 8217 grease, three small blobs on the barrel wall). Also bridle was welded on one turn before the end of the spring, unlike Seiko bridle that is welded at the very end of the spring. Centre coil was also too wide and did not catch the arbor. I had to close it up with some fine bent nose pliers, making multiple small adjustments approx 1mm apart around the centre coil. Don't try and do this with a single big adjustment as you will break the spring. Conclusion: Seiko mainspring especially the bridle is too strong and does not slip before the torque gets too much causing the rebanking. Probably works perfectly though after 15 years or so without service giving suitable amplitude when the oils have dried up.

[steve1811uk]

Update: Walked 12 miles yesterday in around four hours on my day off work. The watch lost 0.1 seconds during the walk. I'm very happy that the rebanking had been cured. The watch is running around 0.7 seconds slow during daily wear and gains that back dial up overnight. I'm going to test the power reserve soon as I know that some forum members have had issues getting a decent power reserve with the GR2377X.

[steve1811uk]

Amplitude +24 Hr from full wind
DU 225 degrees
DD 219 degrees
PL 202 degrees
PD 205 degrees
PR 209 degrees
PU 208 degrees

Power reserve measured at 44 hours. Very happy.