Bulova Accutron repair help

[BCMC]

218 Bulova accutron running, hums, but hour and min hand don't move. Seems to be a common problem. Second hand moves with good motion. I've been researching this and have gotten two different theories. It is either the cannon pinion is loose and slipping or it is stuck, rusted. Have only worked on pocket watches and this is entirely new to me. Any help will be greatly appreciated. Thanks T

 

[Chris Radek]

Accutrons running for a long time without service suffer badly. These wheels are from a 2181 I got in for service because it had finally stopped like you are describing. The 4th wheel (on the left) finally wore all the way through its pivot, and that caused the main hands to stop. But the second hand was still running, dragging the wheel flopping around against the plate. And of course you can see the other wheels have ruined pivots too. I had to replace a lot of parts in this one.

Yours may have this problem, or the center wheel may be stuck on its post (there is no traditional cannon pinion) in which case the center wheel which contains the setting clutch has been grinding away without lube and is probably shot. If so you will feel the hand setting is awfully loose.

You'll have to pull it apart and find out. Before you start, be sure you read the full service manual and have everything you need. You must have ultrasonic to clean these, and you must be able to handle the index wheel during disassembly, cleaning, and reassembly without ever touching its edge. Use a grease with moly on the center wheel assembly's clutch. You will need a way to run it at reduced amplitude for phasing after service.

I'm happy to give advice if you dig into it and report back.

 

[BCMC]

Thanks Chris. What a great explanation. Probably too much for me to take on. I have the service manual downloaded so I'll study that tonight. T

 

[BCMC]

Compared the hand setting to my other 218 and it is real loose. T

 

[John Runciman]

Good timing for your question as I was working on at 219 similar to the 218 earlier this week and photographed something relevant. I also have an image out of the 218 service manual.

Then different stories? Somewhere I heard that the lubrication they chose for the center wheel assembly either was a bad lubrication or attracted moisture.

have gotten two different theories. It is either the cannon pinion is loose and slipping or it is stuck, rusted

They're not actually two different theories there is only one reality unfortunately. Then unfortunately were lacking a really good picture of the center wheel assembly as that would make a lot more sense if you can see the picture.

Relating the problem to a pocket watch it's a little hard to tell from the pictures. Normally a pocket watch the center wheel shaft comes through the plate the Canon pinion snaps on top. If you look at the picture and the drawings what looks like a center shaft is not. It's stationary it's carrying the pivot for the secondhand. This is why the secondhand continues to rotate its being driven from the other side. What looks like a cannon pinion labeled center wheel assembly is both. The part that looks like the cannon pinion has zero friction and should turn smoothly on the shaft on the plate. The friction comes from the wheel that snaps onto the bottom of the cannon pinion. When the rust develops the cannon pinion caring the minute hand locks in place. Because the Canon pinion wheel assembly does not have to have a lot of friction once the tube part is locked in place the wheel will continue to rotate and soon the friction will disintegrate. Then the rust has a habit of migrating to other parts. Tool hard to tell in my picture but the pivot of the pinion driving the center wheel is rusty.

 

[BCMC]

Thanks John. Does my explanation about the hands setting too easily make sense? T

 

[John Runciman]

Does my explanation about the hands setting too easily make sense? T

I have better pictures that will hopefully explain what's going on. The center wheel as they call it is one part made of two components. We have what looks like a normal standard cannon pinion With a wheel snapped on the bottom. The part that looks like your normal cannon pinion Is not because it has zero friction it's supposed to turn effortlessly on the post that it goes on. The friction part is from the wheel snapping into the groove on the bottom. When the part that looks like your normal cannon pinion No longer rotates on its post the hands quit turning. Unfortunately the wheel underneath often times will continue to rotate and no longer has any friction between it and the groove it's in. This is why when you go to set the hands it turns effortlessly because there is zero friction here. The best fix is to replace the entire component. Sometimes you can pop the gear off and flip it over and put it back on again and sometimes that works. Other times people of have attempted to tighten the wheel so it snaps on with more force.

 

[Chris Radek]

Do you service a lot of 218s? The problem John and I have both taken our turns describing is very common. I agree that depending on the wear, flipping the wheel over sometimes helps, as John says, but I have not succeeded in tightening these otherwise. I've tried a couple ways of riveting it, and I can make it tighter, but it ends up off center and doesn't mesh with the 4th pinion well anymore. It's a surprisingly high precision part. I guess in summary, everything John said sounds exactly right to me.

Do you have any suggestions of things to try? If you've easily fixed them I would really appreciate hearing how.

 

[BCMC]

Having major problem in getting the date detent spring installed. Whatever I try the magnetism takes over and moves the spring. Lost it down a hole for half an hour. I've read every post regarding this. Put in from top after plate installed, slide it in from side, install prior to plate. Any suggestions. T

 

[Chris Radek]

On a 218D or 2185 you have to put the spring there and then put the plate on, it's kind of hard to do, there's no shortcut. On a 2181/2182 it's easy, just put the plate on, and then put the spring in through the hole. The short side goes away from the detent. Put one side in and then the middle/bend and then the other side.

I use only brass tweezers on Accutrons. Trying to use steel tweezers is a nightmare because of the strong magnets.

 

[BCMC]

John, Chris and other assisters. It appears that the wheel that is supposed to be attached to the pinion has worn loose. John your latest pictures really helped me out. This has really frustrated me having only worked on pocket watches. Everything is so different. My wife says it keeps me busy but I should be winterizing the irrigation instead of working on an Accutron. It has become a challenge now so after the world series game I'll dig into the movement and retrieve the gear laying unattached and go from there. Thanks for your help, stay turned if you want a laugh or two. Terry