Getting the tension right on centre wheel

[skinnb1]

I have this HAC Alarm clock which has been keeping me busy with various faults. It is now ticking happily but the hands don't turn. I deduced that the centre wheel was turning but its arbor was not rotating. I think I understand the construction of the arbor and wheel but perhaps not. As I understand it the wheel must be free enough on its arbor to allow the arbor to be turned by hand to adjust the time but must be attached firmly enough so that the arbor turns with the wheel under normal operation. The spring on the arbor is designed to facilitate this by keeping some tension on but allowing the arbor to be turned without the wheel turning.

With some difficulty and a little violence I have dismantled the centre wheel and installed a substitute spring with a collet to retain it but the problem persists. The wheel is turning too freely on its arbor.

How can I increase the tension on the wheel so that the hands will turn driven by the clock mechanism and also allow adjustment of the time by hand?

Thanks for any advice you can give.

 

[Vernon]

There might be a crack in the solid brass pinion that's causing the slippage. If so, there are a couple of repair methods that you can search for on the board.
Vernon

 

[shutterbug]

Hang on to the pinion and see if the other wheel will turn. That should answer the question

 

[skinnb1]

Hang on to the pinion and see if the other wheel will turn. That should answer the question

Thanks, but I guess I asked the wrong question. I know that there is not enough friction because the pinion is turning but the arbor is not. What I don't understand is how to change the amount of friction so that the pinion will turn the arbor under normal operation but will allow the arbor to turn when the hands need to be moved manually. I am afraid I am being a bit dim. On a watch I would tighten the canon pinion. Here do I need to increase the strength of the spring or is there some other adjustment I should be making. I can't visualise the forces in operation.

 

[shutterbug]

It appears that the only tension would be from the spring, and it looks like it's under enough tension. It would be adjusted by moving the collar behind it. I suspect though that the pinion will need to be staked to the arbor again.
But to clarify, are you talking about the lantern pinion turning freely, or the front pinion?

 

[skinnb1]

It appears that the only tension would be from the spring, and it looks like it's under enough tension. It would be adjusted by moving the collar behind it. I suspect though that the pinion will need to be staked to the arbor again.
But to clarify, are you talking about the lantern pinion turning freely, or the front pinion?

Thanks. I'm talking about the lantern pinon. But I believe that the lantern pinion is staked to the wheel not to the arbor. Having thought about it some more I think the solution is to replace my replacement spring with something stronger. My thinking is that the friction required is between the collet retaining the spring and the remaining components. The only thing actually staked to the arbor is the collet. When there is sufficient tension the lantern pinion and the wheel rotate causing the collet to rotate and therefore the arbor to rotate. This is normal operation. If there is insufficient tension the collet does not rotate and the lantern pinion and the wheel rotate freely.

When the arbor is turned by hand to adjust the time the pressure of turning the arbor is greater than the pressure imposed by the clock mechanism and the arbor can turn without the lantern pinion and the wheel turning.

The front pinion is firmly staked onto the arbor.

At the moment, with the clock disassembled, I can turn the wheel and the arbor will turn but if I hold the arbor lightly the wheel will continue to turn without the arbor moving.

So I think I need to either move the collet to compress the spring more or to remove the collet and install a stronger spring. But I am happy to be corrected. I haven't met this before.

 

[Mike Phelan]

Surely the pinion and wheel are fixed to each other and not to the arbor, so the hands can be turned, or have I got this wrong?

 

[skinnb1]

Surely the pinion and wheel are fixed to each other and not to the arbor, so the hands can be turned, or have I got this wrong?

"But I believe that the lantern pinion is staked to the wheel not to the arbor".

That's right.

 

[shutterbug]

Yeah, I was referring to the front pinion, but it looks like its the tension causing the problem.

 

[wow]

The collet you installed, if closer to the spring, should tighten the spring and put more tension on the pinion/wheel, right? Can you move the collet? Or…. Just install a stronger spring?

 

[skinnb1]

The collet you installed, if closer to the spring, should tighten the spring and put more tension on the pinion/wheel, right? Can you move the collet? Or…. Just install a stronger spring?

Thanks. I will remove the collet and install a stronger spring.

 

[Mike Phelan]

Yeah, I was referring to the front pinion, but it looks like its the tension causing the problem.

Gotcha!