I wanted to share my recent experiences in getting my original 1961 Clock working properly again. About 20 years ago I had set it out to be fixed but a few years after that it began to have problems. Under normal operation it should “wind” about once every 6 or 7 minutes. The sound should be a single click noise. The problem I was having could be described as chattering or vibrating which was actually multiple clicks occurring in rapid succession. At best it would click 6 or 7 times, but at worst it might continue clicking for a second or more.

At first I believed it to be related to the triggering mechanism which closes a gap and powers the solenoids to wind the clock. All attempts to moderate this trigger linkage were unsuccessful. Later I learned that it had nothing to do with this linkage. Under normal operation as the clock nears rewinding a spring arm attached to the winding bar axle trips the trigger linkage which pushes closed an electrical contact which powers the solenoids. The main winding bar moves until reaching the end of the stroke where the electrical contact is disengaged. The spring arm motion also resets the trigger linkage. The trigger linkage is connected to +12v and insulated from the rest of the clock until it touches the spring arm and completes the solenoid circuit.

After filming the mechanism in slow motion my attention turned to the ratchet “gear” which is used to wind the spring. On the winding bar there are two spring loaded cams with teeth that release during winding and re-engage at the end of the cycle. A simple spring attached to the winding bar provides the energy to run the clock. There is also one Pawl cam which should hold the ratchet gear stationary as the two cams move to their new position.

This Pawl cam was at the root cause of the winding problem. It was slipping. It allowed the ratchet gear to slip after the winding cycle and caused the cycle to immediately repeat several or many times over and over. This is the chattering I had observed. (See first attachment slow-motion video)

There is a small leaf spring which holds the pawl cam against the ratchet wheel. This spring is mounted in a pin which is pressed into a plate. In my clock the pin had rotated releasing the necessary tension on the leaf spring. I also found that the pawl cam was very dirty and full of metal shavings and debris.

I cleaned the Pawl cam and found a way to keep the leaf spring sufficiently tight against the pawl cam so that it no longer slipped. It’s important that the leaf is not too tight, because it needs to slowly ratchet as the gear moves during the ticking of the clock. It’s difficult to explain, but using a small paperclip I fabricated a holder to keep the leaf spring sufficiently tight by holding the spring pin in the proper position. For mine, the proper leaf spring orientation at the anchor was radially pointed to the center of the clock. Don’t bother with glue or solder because that won’t hold.

Now I finally have a clock that works properly with the single click and proper winding every 6 or 7 minutes. (See second video attachment and turn your sound up.)

It also helps to make sure that the trigger linkage trips near the end it’s travel but not too soon or else it will wind more often than needed. To change the trigger linkage timing, bend the inner small coil spring mount left or right to retard or advance the trigger timing. This small spring can be seen in the 1st picture below. Adding a small amount of contact cleaner to the electrical contact of the trigger is also a good idea. I always use Deoxit Gold contact cleaner. Also, Do not oil the ratchet gear because that may cause it to slip.

I have also added a fuse between the clock connector and the clock since this circuit has no fuse. This is to mitigate any possibility of battery drain, excessive heat and fire related to clock operation. I selected a 2.0A fuse based on the coils having a resistance of 4ohms which would give 3A of current if shorted.

 

Years ago I bought a restored clock. I think it was from clockworks or something like that where they converted the clocks. A few years ago it quit work. I still have not addressed the clock problem. Lazy I guess. I never look at the clock anyways. Not in any hurry when I am in the corvette unless I have to pass another corvette or mustang on the highway.

 

Fooled with the clock in R66 for a couple of weeks. Lay it on it's back or face on the bench and it worked flawlessly. Stand it up and it might go 3 or 4 cycles before it quit. Appears the bearings for the shafts are missing as the holes are larger than they should be. After all, if it ran for 56 years, it would be almost 500,000 hours, it needs a rest.
Set it for 5:00 and you are good to go, after all, the average person has a wrist watch and phone, so who needs a clock?

 

Thank you for posting such detail on your diagnosis and repair. I’m sure it will be helpful to those trying to get their’s running again.

 

@R66 I understand your point of view. But as a recovering engineer, I find it tempting to fix things that are broken. For the mid-year corvettes I think there’s an abundance of conversion kits to quartz. I would have been tempted to do that, but for earlier clocks you can only buy completed conversions. Also, I like to keep things operating on the old technology, if possible. On my ‘61 I have kept everything original and period correct with a only a few exceptions…I changed my interior illumination light bulbs to LED and I have 2 small speakers with an amplifier for music from my iPhone.

 

Send it out for a digital conversion. Quicker than reading this post

 

Thanks for the post.

 

Wow, that was a great write up and photo post. I went the easy route. Zip Corvette supplied a quartz clock looks the same and keeps great time. NCRS would not approve. LOL