Why would you ever want to fit a 7750 wheel in a 2836? Well, maybe for a lot of reasons.
As for me, I have been working on a mod project for a while now: fitting a gen dial and hands to a VC Overseas. One of the problems I faced was that the gen dial's date window is set farther out than the rep, leaving the date numbers off-center and almost touching the inside edge of the date window. Also, the date font for the 2836 wasn't really all that close to the gen, so I needed another solution. Unfortunately I don't have a picture of the gen dial on the stock date wheel for comparison; I hope I described my problem adequately.
To fix the issue with the font and spacing I decided to try to fit the date wheel from the ETA7750 into the 2836 movement. Not an obvious task given that the wheels are different sizes and thicknesses.
The 7750 wheel is wider and the cogs are in the wrong position, as you can see from the top half of the first picture. So I decided I had to grind down a 2836 wheel until I could fit the remnant inside the inner lip of the 7750 wheel, which you see at the bottom:
I basically mounted the wheel so it was centered on the end of a dremel bit and let it run on its lowest setting while i lightly applied pressure with a small file. I turned it 180 degrees in the mount periodically to make sure the date wheel was ground down evenly. It took a while but it came out fine.
The 7750 wheel is also significantly thicker so I had to grind down the thickness of the wheel so it would be a better fit, otherwise the dial would sit too high and the date wheel would rub on the base plate. You can see the grinding on the back view:
I ground it more on the outside than the inside as that is where the clearance issue is on the baseplate, and because I wanted the remnants of the cogs to retain some strength to hold the 2836 ring.
Here's what the date wheel looks like with the 2836 inner ring and cogs fit inside, with an unmodded 2836 wheel for comparison:
Here's the backside showing the fitment of the 2836 wheel inside the 7750 wheel. I left the 7750 cogs intact so there was something to give the 2836 inner ring some support. I lightly brushed a bit of superglue into the gaps you see on the backside of the wheel where the 7750 cogs meet the 2836 inner ring. It holds well.
here's the modified 7750 wheel fit into the movement. I had to use a dial ring from an A7750 which fit right around the outer lip of the 2836 plate that retains the stock dial ring. It's held in place by dial dots and does not affect the fitment of the movement.
Here is a test fit of the date wheel with the dial all installed in the case. I have since done a slight adjustment to the cog position to allow me to move the dial clockwise slightly; it's a bit off in this picture. Anyway it should give you an idea of how well centered the date font is now.
I had to remove about .4 mm of material from the inside of the case to get the gen dial to fit, which took a lot of grinding and test fitting. I ground the case rather than the dial because I wanted to leave the dial intact, and because the gen rehaut is shorter than the rep one, so there was going to be a small gap of about .5mm I had to make up somewhere. It took longer but I had the time and I think it's worth it. The crystal gasket still fits perfectly so no worries there.
Here is a view of the movement with gen hour and minute hands installed. I had to use a taller cannon pinion and hour wheel to get the clearance I needed. The gen hour hand fit perfectly, but the gen minute hand needed a small layer of epoxy around the inner edge of the hole to make it small enough to fit on the cannon pinion:
and a lume shot:
The lume is a really nice soft whitish green pastel color and it glows bright; the pic doesn't do it justice.
The new wheel is more centered and fills the window much better than before, although you can't really tell from the "31". I'll get a picture of some other numbers to demonstrate the spacing. "22" for example is very well spaced and fills almost the entire window. There's still a bit of play for the final placement of the date window when I fit the movement in the case, too. As for the font, well most of the numbers look better, except for the "8" which looks closer to gen on the 2836. All in all, although the solution isn't perfect, I think it's a big improvement. What do you guys think? Here's a couple gens for comparison:
So, that's it for my tutorial. I don't know how many people will ever need to do this, but if you do need to fit a 7750 wheel in a 2836, at least you know it's possible. Thanks go out to d4m for sourcing the VCO, and strongly encouraging me to write this tutorial; and to ar0401 for his help and advice on fitting the gen dial.
As for my franken VCO (Vacheron Frankentin?
), stay tuned for the finished product when I get the crystal back from Chief.
As for me, I have been working on a mod project for a while now: fitting a gen dial and hands to a VC Overseas. One of the problems I faced was that the gen dial's date window is set farther out than the rep, leaving the date numbers off-center and almost touching the inside edge of the date window. Also, the date font for the 2836 wasn't really all that close to the gen, so I needed another solution. Unfortunately I don't have a picture of the gen dial on the stock date wheel for comparison; I hope I described my problem adequately.
To fix the issue with the font and spacing I decided to try to fit the date wheel from the ETA7750 into the 2836 movement. Not an obvious task given that the wheels are different sizes and thicknesses.
The 7750 wheel is wider and the cogs are in the wrong position, as you can see from the top half of the first picture. So I decided I had to grind down a 2836 wheel until I could fit the remnant inside the inner lip of the 7750 wheel, which you see at the bottom:
I basically mounted the wheel so it was centered on the end of a dremel bit and let it run on its lowest setting while i lightly applied pressure with a small file. I turned it 180 degrees in the mount periodically to make sure the date wheel was ground down evenly. It took a while but it came out fine.
The 7750 wheel is also significantly thicker so I had to grind down the thickness of the wheel so it would be a better fit, otherwise the dial would sit too high and the date wheel would rub on the base plate. You can see the grinding on the back view:
I ground it more on the outside than the inside as that is where the clearance issue is on the baseplate, and because I wanted the remnants of the cogs to retain some strength to hold the 2836 ring.
Here's what the date wheel looks like with the 2836 inner ring and cogs fit inside, with an unmodded 2836 wheel for comparison:
Here's the backside showing the fitment of the 2836 wheel inside the 7750 wheel. I left the 7750 cogs intact so there was something to give the 2836 inner ring some support. I lightly brushed a bit of superglue into the gaps you see on the backside of the wheel where the 7750 cogs meet the 2836 inner ring. It holds well.
here's the modified 7750 wheel fit into the movement. I had to use a dial ring from an A7750 which fit right around the outer lip of the 2836 plate that retains the stock dial ring. It's held in place by dial dots and does not affect the fitment of the movement.
Here is a test fit of the date wheel with the dial all installed in the case. I have since done a slight adjustment to the cog position to allow me to move the dial clockwise slightly; it's a bit off in this picture. Anyway it should give you an idea of how well centered the date font is now.
I had to remove about .4 mm of material from the inside of the case to get the gen dial to fit, which took a lot of grinding and test fitting. I ground the case rather than the dial because I wanted to leave the dial intact, and because the gen rehaut is shorter than the rep one, so there was going to be a small gap of about .5mm I had to make up somewhere. It took longer but I had the time and I think it's worth it. The crystal gasket still fits perfectly so no worries there.
Here is a view of the movement with gen hour and minute hands installed. I had to use a taller cannon pinion and hour wheel to get the clearance I needed. The gen hour hand fit perfectly, but the gen minute hand needed a small layer of epoxy around the inner edge of the hole to make it small enough to fit on the cannon pinion:
and a lume shot:
The lume is a really nice soft whitish green pastel color and it glows bright; the pic doesn't do it justice.
The new wheel is more centered and fills the window much better than before, although you can't really tell from the "31". I'll get a picture of some other numbers to demonstrate the spacing. "22" for example is very well spaced and fills almost the entire window. There's still a bit of play for the final placement of the date window when I fit the movement in the case, too. As for the font, well most of the numbers look better, except for the "8" which looks closer to gen on the 2836. All in all, although the solution isn't perfect, I think it's a big improvement. What do you guys think? Here's a couple gens for comparison:
So, that's it for my tutorial. I don't know how many people will ever need to do this, but if you do need to fit a 7750 wheel in a 2836, at least you know it's possible. Thanks go out to d4m for sourcing the VCO, and strongly encouraging me to write this tutorial; and to ar0401 for his help and advice on fitting the gen dial.
As for my franken VCO (Vacheron Frankentin?
), stay tuned for the finished product when I get the crystal back from Chief. 
