spookycord Posted February 4, 2008 Report Posted February 4, 2008 I have a question for the experts. I was changing a date wheel on an A7750 and all of a sudden heard a long whir as the mainspring released and unwound itself. I noticed that the escape wheel pivots where not sitting in it's jewel. I tried to set it without removing any bridges but it seemed like the gap between the bridges that hold it was just ever so slightly too far apart. I then tore town the movement, removing the bridges to expose the mainplate and wheels, reset all the wheels and escape wheel, but when i put the bridge back on top, same problem. The escape wheel pivot just is not reaching the top plate. I am a noob at all this, trying to learn by trial by fire I guess, but could use some help. The Zigmeister's references are awesome, but I'm stuck. Am I missing something or did I break something? On another note, any tips on how to prevent from losing the tiny screws that sometimes pop off when removing?
RWG Technical Posted February 5, 2008 Report Posted February 5, 2008 Look closely at the top and bottom pivots of the escape wheel, I would guess that the pivot is broken off...hence your problem... RG
spookycord Posted February 5, 2008 Author Report Posted February 5, 2008 Look closely at the top and bottom pivots of the escape wheel, I would guess that the pivot is broken off...hence your problem... RG i kinda suspected that might be it. the bottom of the wheel has about a 1mm stem and the top about 3mm. i'll take a pic when i get a chance. if it is broken where can i get a new one?
Francisco Posted February 5, 2008 Report Posted February 5, 2008 I have a question for the experts. I was changing a date wheel on an A7750 and all of a sudden heard a long whir as the mainspring released and unwound itself. I noticed that the escape wheel pivots where not sitting in it's jewel. I tried to set it without removing any bridges but it seemed like the gap between the bridges that hold it was just ever so slightly too far apart. I then tore town the movement, removing the bridges to expose the mainplate and wheels, reset all the wheels and escape wheel, but when i put the bridge back on top, same problem. The escape wheel pivot just is not reaching the top plate. I am a noob at all this, trying to learn by trial by fire I guess, but could use some help. The Zigmeister's references are awesome, but I'm stuck. Am I missing something or did I break something? On another note, any tips on how to prevent from losing the tiny screws that sometimes pop off when removing? I cannot imagine how you could release the mainspring barrel. Did you touch anything? For me, it is very strange and I would like to know what was wrong.
spookycord Posted February 5, 2008 Author Report Posted February 5, 2008 I cannot imagine how you could release the mainspring barrel. Did you touch anything? For me, it is very strange and I would like to know what was wrong. I am, not positive, but when tearing down the movement I noticed the screw on the bridge that attaches the chrono plate to the main plate near the escape wheel was not tight. It was seated properly, which should hold the escape wheel in place, but from what I could tell the escape wheel came unseated, and I'm assuming this released the tension of the spring? again, i am trying to learn how these movements work, so excuse me if I'm way off base.
RWG Technical Posted February 5, 2008 Report Posted February 5, 2008 All the tension in the mainspring is held back by the pallet stones on the escape wheel. Remove the escape wheel (or have it break and the gear disconnect from the second wheel teeth) and there is nothing stopping the mainspring from unwinding, so it makes perfect sense for the mainspring to unwind if the pivot broke off of the escape wheel. Re-assembling a 7750 is a very daunting task, no where near any other movement in terms of difficulty, or the time it takes (except for the El-Primero, that one is very difficult and time consuming to service). Unless you have assembled a 7750 successfully before, I don't envy your position at this point. RG
spookycord Posted February 5, 2008 Author Report Posted February 5, 2008 Daunting is a relative term. For me, that means damn near impossible! But to me failure is a great teacher and I'm chalking this up to a learning experience. Here is a pic of the escape wheel. Can you tell if it's broken?
RWG Technical Posted February 5, 2008 Report Posted February 5, 2008 Is it EVER broken...both pivots are gone... Since you have the movement basically totally torn down, you should go ahead and run it through a cleaner and start fresh with a clean and oiled and fully serviced movement. Send me a PM and we'll sort something out for a replacement one. RG
spookycord Posted February 19, 2008 Author Report Posted February 19, 2008 Hey zig, you pm's are blocked, pm me on how i can get a wheel from you
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