Hamilton Westminster (Hamilton Cal.92 / Buren Cal.1281 Micro-Rotor)

[Marc]

This is what I got up to over the Easter break.

It was a project that I bought as a box of bits for a few quid about 4 years ago because although I had no idea what it was (the listing didn't say), it looked interesting and I fancied the challenge.

It turned out to be a Hamilton Intra-Matic Westminster which the previous owner had tried to "fix", got as far as dismantling, and given up on. 

Cosmetically it was in good order but mechanically was not good. The rotor pinion had lost its bottom pivot, as had the second wheel (centre wheel in a more conventional wheel train). And because it had spent some time rattling around loose in the box of bits the hair spring was in a poor state, and what had me really stumped when it came to working out how it all went back together was a large and rather complicated looking wheel and pinion assembly for which I simply couldn't find a home.

Any way, it was put to one side until I could track down a donor for the parts and to hopefully show me where the "spare wheel" went.

The movement is a 30 jewel Hamilton 92 micro-rotor, which is a re-badged Buren 1281. Unfortunately (for me) this has been used in a number of higher end autos and also as the base movement in some big name modular chronographs because of its thinness, which means that they tend to hold 3 figure values even as spare parts donors so it took a while for me to track down a suitable candidate at the right price. However, I did manage in the end to nab one for just over £30 and it arrived at the beginning of April, so the fun could begin.

 

No strip down on this one as the Hammy came to me fully dismantled, here is the donor as I got it.

 

 

 

It's a Buren 1281, a bit grubby with some missing screws, and the minute hand pinion has seized onto the centre post. I later discover that the canon pinion (which is actually on the second wheel pinion) is loose and I reckon that someone had diagnosed the loose canon pinion, had tried to correct it by tightening what they thought was the canon pinion, which was in fact the minute hand pinion, onto the centre post, over did it, and caused the whole thing to seize, hence spare parts movement on eBay!!!

 

I stripped out the second wheel (complete with canon pinion which I tightened), rotor pinion, balance and hair spring, and the main spring (which was in better shape than the Hammy one), and then put the parts through the cleaner; the Hamilton 92 parts had already been cleaned.

 

And here we go with the good bit.

 

 

The Hamilton 92 main plate; cleaned and ready for reassembly.

 

 

I usually start with the wheel train when I build a movement back up but that's not possible here because the motion works bridge also carries the lower pivot jewel for the second wheel, so the motion works have to go in first.

 

 

With the bridge in place you can see the pivot jewel in between the minute wheel and the intermediate wheel.

 

 

The movement is flipped and the wheel train and barrel (cleaned and greased main spring, and braking grease on the barrel walls) are positioned.

 

 

Train bridge and barrel bridge installed complete with crown wheel and intermediate winding wheels.

At this point the end shake on all of the wheels was checked and the general free running of the whole train tested, then the pivots oiled.

 

 

The ratchet wheel in place, the pallet fork installed and the escape wheel teeth / pallet jewels lubricated. The balance dropped in and off it goes.

 

 

Then the auto winding reversers and reduction wheels go in. The three armed spring on the first reduction wheel is a ratchet which prevents the rotor from helicoptering during manual winding. Unfortunately it also gives the crown a very gritty feeling when you hand wind which takes a bit of getting used too but it is normal.

 

 

Bi-directional flip-flop (for want of a better term) gear and auto wind ratchet in place.

 

 

Cover plate on and the micro-rotor assembly installed.

 

 

Turning things over again the keyless works go in.

 

 

Then the calendar works, date wheel, and cover plate.

 

 

Before the dial and hands go back on.

 

 

Confirmation on the Timegrapher that all is well.

 

 

The obligatory wrist shot.

 

 

And something more formal for the album :-)

 

This is now an absolute favourite of mine and has a permanent home in my collection. It took a lot of waiting to get the donor but it was well worth it. The watch has been running continuously since 11 April kept wound from wearing it when I get home from work in the evenings and at the weekend, and has remained within a few seconds of reference time.

 

And the "spare wheel"..... was precisely that, it didn't belong with the box of parts that this project started out as. I do hope the seller didn't miss it :-)  

[Geo]

What an excellent write up Marc, I really enjoyed that. :)

I have a couple of these beasties myself, but have yet to work on them. One is a Buren, and the other a Hamilton. I'll certainly have a couple more reads of this before servicing them!

[Marc]

Thanks for the kind words Geo.

I really enjoyed working on this watch and actually found it surprisingly easy to pull it all together.

I'm sure that yours will present you with no problems.

[bobm12]

That's an amazing job Marc. Looks amazingly good, I would wear it with pride, which is a lot to say considering I'm not too partial for square (ish) watches! Congratulations on a super well done job!...and excellent walkthrough, much appreciated!

 

Cheers,

 

Bob

[autowind]

Nice,  clear walk through with a very good result at the end,  well done Marc.

[WillFly]

A lovely watch and a great job. I have an Intra-Matic and absolutely love the design of the movement - a real cracker. You can see it here:

 

http://www.willswatchpages.com/hamilton-intra-matic.html

 

I'm told that the movement is perhaps a little less efficient than a conventionally large rotor, and may wind down quicker. I don't wear mine enough to comment on that - what's your assessment?

[HorologicalHobby]

I serviced one of these myself! Thought it was an older version, the calendar works on mine was a bear to get adjusted right.

[clockboy]

Marc, Great write up & well presented.  A lovely watch.

[perpetual92]

Great watch and documentary on the service. Its regulation on the Timegrapher is giving stunning results.  Nice !!

[Poljot]

Five years later...

 

Good day Marc,

Did you lubricate the sliding face of the spring on the coupling wheel? It appears that if left dry, it will make winding difficult. In fact, that may explain why I see a broken Intermediate Crown Wheel on my Bulova 12EBA watch, which is basically identical to Buren 1281. Glissalube red grease should be used according to Bulova instructions. I do not have that Moebius 8212. Anything else can be used in lieu of 8212?

[Marc]

Hi Poljot,

From what I can recall I lubricated the ratchet spring with LT2 Moly grease. As I mentioned in the write up  it's a design that lends a certain gritty feeling to manual winding which takes a little getting used too. I can imagine that if left dry though it would be a right pig to wind, especially as the crown on my Westminster is very small.

Incidentally, you've reminded me that this little beastie is due a service, I can't believe that it was five years ago!!!

[Poljot]

Thank you Marc. I am sure it won't take long for you to service this caliber. I was very surprised how rough winding was after I installed a brand new Intermediate Crown wheel. It felt like something was incorrectly installed, but I knew that prior to fitting that new wheel I observed the auto-winding function and it worked very smooth.  Not sure why 8212 is recommended for the sliding face of the spring on the coupling wheel.