Mains clock self start - UK Vintage Radio Repair and Restoration Discussion Forum

Refugee · 30th Sep 2018, 1:01 am

Many members get very confused when a mains clock fails to start in the correct direction.
I have found a motor in the timer from a microwave that had a switching failure in the heat rate control.
There is a little clutch that is packed with grease that fits under three little hooks and looks like it is fitted to the gear with circlip pliers during production. It has a long plastic spring with a paddle on the end of it. There is also a peg to stop the flag being pushed down. First photo.

The motor pinion has a free wheel like cam below the gear teeth.
In the lower right of the photo you can see the shadow of the parking stop for the flag when the motor is running in the correct direction (antickockwise). Second photo.

In the next photo you can see the flag close to the stop cam as it would be when the motor is running in the correct direction. Third photo.

The next photo shows the flag close to the cam on the motor where it will strike the free wheel cam and get compressed until the motor rotation is overcome and the rotor gets sprung to the correct direction of rotation. The grease will provide some viscose resistance to help the spring to compress so generating the energy needed to flick the rotor in the right direction. Fourth photo.

Then a general view with the flag mid way between the two positions. Last photo.

Phil G4SPZ · 3rd Oct 2018, 3:22 pm

That's an interesting modern variant on the older Smiths type of mains synchronous clock movement where a metal cam 'bounced' the motor back into the correct direction.

Refugee · 3rd Oct 2018, 11:18 pm

I felt that due to all the parts being bright plastic and easy to take photos of it was worth posting some photos to help others to see what they are looking for when they have a problem.
This plastic one appears to rely on the grease for correct operation so the same cleaning and re-lubrication as a record deck would apply.

30th Sep 2018, 1:01 am	#1
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Mains clock self start Many members get very confused when a mains clock fails to start in the correct direction. I have found a motor in the timer from a microwave that had a switching failure in the heat rate control. There is a little clutch that is packed with grease that fits under three little hooks and looks like it is fitted to the gear with circlip pliers during production. It has a long plastic spring with a paddle on the end of it. There is also a peg to stop the flag being pushed down. First photo. The motor pinion has a free wheel like cam below the gear teeth. In the lower right of the photo you can see the shadow of the parking stop for the flag when the motor is running in the correct direction (antickockwise). Second photo. In the next photo you can see the flag close to the stop cam as it would be when the motor is running in the correct direction. Third photo. The next photo shows the flag close to the cam on the motor where it will strike the free wheel cam and get compressed until the motor rotation is overcome and the rotor gets sprung to the correct direction of rotation. The grease will provide some viscose resistance to help the spring to compress so generating the energy needed to flick the rotor in the right direction. Fourth photo. Then a general view with the flag mid way between the two positions. Last photo. Attached Thumbnails Last edited by Refugee; 30th Sep 2018 at 1:14 am.

3rd Oct 2018, 3:22 pm	#2
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: Mains clock self start That's an interesting modern variant on the older Smiths type of mains synchronous clock movement where a metal cam 'bounced' the motor back into the correct direction. __________________ Phil Optimist [n]: One who is not in possession of the full facts

3rd Oct 2018, 11:18 pm	#3
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Mains clock self start I felt that due to all the parts being bright plastic and easy to take photos of it was worth posting some photos to help others to see what they are looking for when they have a problem. This plastic one appears to rely on the grease for correct operation so the same cleaning and re-lubrication as a record deck would apply.