One of the few clocks that I have had professionally serviced is an Arthur Pequegnat kitchen clock (Fan Top). In the early days of clock collecting and repair I had not acquired the necessary skills and experience to perform my own work and had some of my special clocks serviced by a skilled clock-maker. I consider this Arthur Pequegnat “fan-top” kitchen clock, a special clock.
The following comments are not a reflection of the work done by a professional clock repair shop. I consider the clock-maker who performed the service on this clock to be highly competent and I would recommend them to anyone but mechanical clocks can be very temperamental at times.
Two years after the clock was serviced, it stopped. It shouldn’t have! I considered all of the possibilities including weak mainsprings, bushing issues, bent, twisted or torn suspension spring and bent wheels to name a few.
Pushing the pendulum gently had no effect. I removed the dial to inspect the movement and found that the crutch wire had disconnected from the pallet. An easy fix; solder the crutch wire to the pallet ensuring that I achieve the correct angle. Alas, only partial success.
Okay, a partial fix, what else is wrong
Over several cycles with the springs fully wound it ran no more than 4 days before it stopped. A power issue?
I was not about to disassemble the movement, yet something had to be robbing it of power.
Well, look what we have here
Often the simplest solution is the best. I did a little research on the function and proper adjustment of a crutch loop on an American styled open mainspring movement. I then checked the play in the crutch loop on this Arthur Pequegnat movement.
Too much play and the crutch loop will have to travel too far to catch up to the swinging pendulum before imparting impulse since the wider the gap in the crutch wire the longer it takes the crutch to catch up to the pendulum rod. This results in the pendulum receiving an abrupt hit late in its oscillation rather than a full steady push and eventually stopping.
A partial push (tighter loop) means a weaker impulse to the pendulum which equates to energy loss and stoppage once the springs have released most of their power. In the case of my clock, a tight crutch loop meant there was not enough impulse to maintain the cycle beyond 4 days once the mainspring had released much of its power.
Mainsprings release less power in the last days of a cycle, which is why most spring-driven American clocks tend to slow down at the end of the 8-day cycle. A gain of a minute or two at the beginning of the week might translate to a loss of a minute or two at the end of the 8-day cycle as the springs release less power. This is quite normal.
Sometimes it is the simplest solution that solves the problem
Aha, I’ve got it!
The clock had been sitting for a year. Now that I understand the problem, it was a easy fix. I experimented with the correct crutch loop play, using a trial and error approach widening and narrowing the loop. After some experimentation I was satisfied that there was sufficient impulse and good pendulum amplitude. I then set the movement in beat. The result is a clock that happily completes its full 8-day cycle.
The simplest solution is best only after you have a better understanding of the problem.