Sessions mainspring questions

[Ray Snead]

I have just disassembled an 8 day Sessions movement for cleaning and bushing.

In the process of cleaning the mainsprings, I found a crack half way through the strike train spring near the hook.

This movement has loop end mainsprings that do not match.

The time train spring is 3/4" wide, ~88" long and 0.40MM thick. It's color is blue

The strike train mainspring is 3/4" wide, ~97" long and 0.45MM thick. It's color is a silver/ gray

Given this, I suspect that one or both of the springs have been replaced before.

My question is, "Is this configuration correct?" If not, what should it be.

Both of the clocks trains were running prior to disassembly.

Thanks in advance for any assistance.

[Ray Snead]

I have just disassembled an 8 day Sessions movement for cleaning and bushing.

In the process of cleaning the mainsprings, I found a crack half way through the strike train spring near the hook.

This movement has loop end mainsprings that do not match.

The time train spring is 3/4" wide, ~88" long and 0.40MM thick. It's color is blue

The strike train mainspring is 3/4" wide, ~97" long and 0.45MM thick. It's color is a silver/ gray

Given this, I suspect that one or both of the springs have been replaced before.

My question is, "Is this configuration correct?" If not, what should it be.

Both of the clocks trains were running prior to disassembly.

Thanks in advance for any assistance.

[Ken M.]

Ray,

The original springs were both 3/4" x 96" x 0.018". A better choice for replacement would be: same as before but 0.0175" thick (Time Saver PN 14320) or 0.0165" thick (TS PN 18790) Alittle less power works better AFTER a complete overhaul.

Ken

[Ray Snead]

Thanks for the info Ken. Your reply begs another question. Why would you downrate the power? Seems to me that the movement would never run any better than when it was new and the manufacturer had to have a reason for using the power they specified. Just curious. Maybe the difference is not significant - on a percentage basis, we are talking about less than a 3% thickness differential.

[Richard S]

Greetings Ray!
I think Ken is giving sound advice. Some authors of repair books suggest that American manufacturers originally overpowered their clocks so that they would keep running long after they should be cleaned and serviced. So, despite dirt in the bearings, these old clocks just kept ticking, and ticking, and the dirt was grinding away. I have noticed that mainspring wheels sometimes show the effects of all that power on the teeth-they may be beat up on the side of each tooth that engages the 2nd wheel. The result was that when the clock did finally stop, there was a bunch of bushing and pivot work to do, and maybe some teeth that needed attention.

Going to a thinner (not shorter however) spring will theoretically keep a well maintained movement running with less wear and tear.

[Ray Snead]

Thanks Richard for the conferring second opinion. TS 14320's it will be. Almost half the price to boot! $4.50 vs. $7.50

[Ray Snead]

Thanks Richard for the conferring second opinion. TS 14320's it will be.