Borg Instruments Dashboard Clock

[RyMoeller]

This is the dashboard clock my father pulled from his 1966 Chevrolet El Camino earlier this year. The clock didn't run at all and he asked me to take a look at it. Knowing nothing about automotive clocks I was intrigued and rushed over to pick it up.

It's a simple affair with just two hands and a knob to adjust the time. No winding is necessary. On the back of the clock housing is a single 12 volt connection- the housing itself must ground the clock when installed in the dash.

Stamped on the rear housing are the words Borg Instruments, Delavan Wis. The housing is removed by bending the three sheet metal tabs that run the circumference of the clock.

Inside is a delicious stack of gears and a solenoid which winds the clock.

A coil spring serves as the mainspring in this clock and it holds just about two minutes of power in it. When the coil spring is completely relaxed the two electrical contact points come together and are energized via the 12v connection. This causes the solenoid to act snapping the contacts away from each other and putting energy back into the spring. This action repeats itself every two minutes until the car battery is dead.

Judging from the YouTube videos I watched before tackling this project- the typical failure point is the electrical contacts which wear out over time and fail to connect when the mainspring winds down. This wasn't the problem in my father's clock though. Most of the bearings in his clock had worn pear shaped and needed to be replaced.

I broke down the clock for a good cleaning before turning new bearing on the lathe. The movement only has two jewels (for the balance wheel) so it's not surprising that the bearings would give out eventually. Some of the pivots were worn too and needed cleaning up as well.

One of the cool things about this clock is that adjusting the time also regulates the speed of the clock. The setting knob is geared to make adjustment to the regulator and in this way whenever you make an adjustment 9adding or removing time) you are also adjusting the speed of the escapement.

Everything was giving a nice scrub before reassembly. I removed the balance wheel in order to clean the plates and the hairspring is attached using shellac. This worried me a little bit but I found a narrow tip on the soldering iron was just perfect for softening the shellac and re-securing the hairspring.

In the end I think I replaced five bushings in all.

My father and I tested the clock by attaching it to the battery and letting it run for twenty-four hours; we found it to be a couple minutes slow the next day. I made an adjustment to the regulator before final installation in the dash and it seemed to be a bit better. Time will tell if it was a proper repair though. It was a fun little side project. I always assumed those dashboard clocks were entirely electrical but never bothered to considered how they worked. Now I know. 

[oldhippy]

That must have been running dry for it to have all that wear, apart from the balance those types should be greased. The first types of car clocks used to be wind up.  

A nice walk through by you on how you went about the repair. Thank you so much. 

[KarlvonKoln]

This post brought back memories.  That's practically the exact same movement that was in my old '76 Chevy Camaro.  Man, I miss that car.  It was a blast.  And yeah, with the clock I had to add a couple bushings, and I made a new brass contact, a bit of grease, and then it worked fine.  And it was fairly accurate too.  I remember you always knew the clock was working because, every now and then, you'd hear the solenoid quietly go *thunk*.  I wish I still had pictures of that car.  It was a hot rod by the time I got done with it.

[Tudor]

Cool!

 

I always assumed these were just driven by a 12 volt motor. But, it makes sense it wouldn't be, because at rest, the car voltage is around 12 volts and it goes up to about 14.5 when charging the battery. That's a big swing, and the timing would be quite erratic. De-coupling the movement from the (electrical) power takes away that influence. Quite clever.

Now I'm sure a voltage regulator on a chip drops to nine or six volts, which remains as long as battery power is above the output voltage of the regulator. I have a VDO clock in my Defender that is reasonably accurate (might be quartz?) but also quite noisy... I had thought about dismantling and cleaning & oiling it to keep it quieter than the turbodiesel under the hood.