just to let you guys know what you will be up against if you inadvertently buy a BP SD with a 2824 movement in it and wish to change out the hands.
SteveJones here on this forum recently purchased a BP SD off a TD. Steve kindly sent his watch to me for the addition of TC dial and hands, crown and tube along with a TC bracelet.
A nice easy build you may think!. On receipt of Steve's watch, first thing I noticed was how far back from the dial the DWO was, way too far away, makes the DWO look sunken in the dial and not very gen like at all, in fact a dead giveaway?
I've built the odd one of these and have never seen one this far back, lets get this open and take a look!. Ok back off, movement out, lets get the hands off first. Wow not seen these fitted on a SD before, look at the length of those pinion tubes!!
This is getting interesting, lets whip the dial off and see what's going on under here?
Strange??, extremely thick dial spacer and what are that washer stuck on the back of the dial around the pinion hole?.
Well here's the explanation for all that mechanical tinkering:-
As most of you are aware the BP SD case is dimensionally built to accept the 2836 movement. This puts the stem height 2.25mm from the dial seat to the centre of the stem. On a 2824 this same dimension is 1.8mm, making the difference between the two 0.46mm.
The extra thick dial spacer makes up this dimensional difference by pushing the 2824 stem position towards the back of the case by 0.46mm. This in turn keeps the 2824 stem in alignment with the case pendant tube (crown) The washer glued to the back of the dial in the pinion hole keeps pressure on the hour wheel friction spring to keep the hour wheel in contact with is mating gears.
Great you may think, that's where I want it!,but what about the pinion stack height?. If you look at the first picture of the hands, this has been negotiated by fitting tube extensions to the hands. Still looking good apart from the fact that neither Clark nor TC hands have these fitted, so were stuck with this until we look at different options.
Here's a picture of the movement, dial spacer and dial showing the positional height of the as fitted #2 pinions over the dial
And shows clearly why the hand tube extensions are needed.
Ok, let rectify that by fitting the famous #4 pinion set you may think?, well unfortunately not!. #4 pinion set would increase the length of the hour wheel by 0.5m which may well be enough to allow for correct hand stack height, which in turn would allow us to use optional hands such as Tc's or Carks. However we still have the sunken DWO problem as clearly shown in this photograph
before you ask, this dial I use for DWO alignment and is not the one being fitted!!.
Ok that said, how can we get the DWO up to the back of the dial with little gap. Well we can use a 2836 date wheel instead of the stock 2824 date wheel. This would put us approximately 0.2mm further towards the dial and close the gap down. IMO not close enough but we could also add a couple of layers of double sided tape or even a custom metal DWO spacer 0.35mm thick.
The obvious answer is to get the BP SD with a 2836 movement in it and save all the messing should we want to upgrade the hands, heres how a 2836 stack height looks
Whichever way you look at this its still a lot of cost and work to get this to accept alternative hands, I suggest its far cheaper to ensure you get a 2836 movement in you BP SD.
Hope this helps some of you when you come to purchase!
