Did Smiths and other synchronous clock makers use cycloidal gear teeth? - UK Vintage Radio Repair and Restoration Discussion Forum

Phil G4SPZ · 20th Dec 2023, 8:30 pm

Split from this thread:-

https://www.vintage-radio.net/forum/...d.php?t=206464

Now, there’s a question, did Smiths and other synchronous clock makers use cycloidal gear teeth? The gear train runs backwards compared to a conventional clock, and the forces are much lower. A lot of the synchronous clocks I’ve dealt with have arrived with the train slathered in oil, yet still working and with no discernable wear on the wheel teeth.

Worm and wheel reduction is another matter. I have a Ferranti where the worm and wheel had worn so much that they had become disengaged. I use light grease on these nowadays.

mark_in_manc · 21st Dec 2023, 9:53 am

Quote:

Originally Posted by Phil G4SPZ

Worm and wheel reduction is another matter. I have a Ferranti where the worm and wheel had worn so much that they had become disengaged. I use light grease on these nowadays.

I have a Metamec which is moving in this direction. The worm is plastic - I think I might end up having a go at making one, if I can't find one when it finally lets go. I have cut worms before (much larger ones) with a form-tool, turning like a very coarse thread. The challenge with one of these for me now, would be seeing it!

Hartley118 · 21st Dec 2023, 9:47 pm

I had a Metamec clock where the main pinions were plastic. The conventional light oil lubrication seemed to have an embrittling effect on those gears so that they eventually failed. That was the end of the movement.

Martin

Phil G4SPZ · 22nd Dec 2023, 8:08 am

Thanks to Graham (Station X) for starting this new thread, and apologies for being the cause of your having to do so!

This is a bit of a ‘clockie’ thread, and stems from the fact that traditional clock repairing techniques keep oil or other lubricants firmly away from the gear (or ‘wheel’) teeth. The teeth in a clock are formed in a cycloidal shape where the teeth roll against each other, thus causing no friction and, technically, no wear, hence requiring no lubrication. Cycloidal teeth are used almost exclusively in traditional clock geartrains where the train is effectively “gearing-up” from a very slow-moving, high-torque source (the weight or spring) to the relatively fast-moving escapement. Oil is unnecessary and encourages dirt or dust to stick.

A synchronous clock geartrain “gears-down” a relatively fast motor running at 166 or 200 RPM down to an hour hand rotating twice per day, and would on the face of it have no need for the low friction offered by cycloidal teeth - with no need for lubrication.

I am guessing that synchronous clocks use standard gear tooth profiles, but I genuinely don’t know the answer!

Mike Phelan · 22nd Dec 2023, 9:22 am

Phil,
I think that Smiths used the usual cycloidal wheel teeth. On all the metal wheels and pinions, no lubricant.
I have a Smiths service manual somewhere which says that, but cannot find it!

Phil G4SPZ · 22nd Dec 2023, 9:30 am

Thanks Mike, I think that answers the question!

I’ve never seen a Smiths service manual, but there are some excellent drawings and descriptions in T.R. Robinson’s “Modern Clocks”.

If you manage to locate your document, a copy or scan would be appreciated by many, I’m sure.

Many thanks,

Mike Phelan · 22nd Dec 2023, 4:32 pm

Will do, Phil but it might be a while as we're away soon until the New Year and I suspect it's in the garage.
Slightly OT but Robinson's book is excellent - I've had it for years now.

20th Dec 2023, 8:30 pm	#1
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,749	Did Smiths and other synchronous clock makers use cycloidal gear teeth? Split from this thread:- https://www.vintage-radio.net/forum/...d.php?t=206464 Now, there’s a question, did Smiths and other synchronous clock makers use cycloidal gear teeth? The gear train runs backwards compared to a conventional clock, and the forces are much lower. A lot of the synchronous clocks I’ve dealt with have arrived with the train slathered in oil, yet still working and with no discernable wear on the wheel teeth. Worm and wheel reduction is another matter. I have a Ferranti where the worm and wheel had worn so much that they had become disengaged. I use light grease on these nowadays. __________________ Phil Optimist [n]: One who is not in possession of the full facts Last edited by Station X; 21st Dec 2023 at 10:15 am. Reason: Thread split.

21st Dec 2023, 9:47 pm	#3
Hartley118 Nonode Join Date: Aug 2015 Location: Cambridge, Cambs. UK. Posts: 2,198	Re: Did Smiths and other synchronous clock makers use cycloidal gear teeth? I had a Metamec clock where the main pinions were plastic. The conventional light oil lubrication seemed to have an embrittling effect on those gears so that they eventually failed. That was the end of the movement. Martin __________________ BVWS Member

22nd Dec 2023, 8:08 am	#4
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,749	Re: Did Smiths and other synchronous clock makers use cycloidal gear teeth? Thanks to Graham (Station X) for starting this new thread, and apologies for being the cause of your having to do so! This is a bit of a ‘clockie’ thread, and stems from the fact that traditional clock repairing techniques keep oil or other lubricants firmly away from the gear (or ‘wheel’) teeth. The teeth in a clock are formed in a cycloidal shape where the teeth roll against each other, thus causing no friction and, technically, no wear, hence requiring no lubrication. Cycloidal teeth are used almost exclusively in traditional clock geartrains where the train is effectively “gearing-up” from a very slow-moving, high-torque source (the weight or spring) to the relatively fast-moving escapement. Oil is unnecessary and encourages dirt or dust to stick. A synchronous clock geartrain “gears-down” a relatively fast motor running at 166 or 200 RPM down to an hour hand rotating twice per day, and would on the face of it have no need for the low friction offered by cycloidal teeth - with no need for lubrication. I am guessing that synchronous clocks use standard gear tooth profiles, but I genuinely don’t know the answer! __________________ Phil Optimist [n]: One who is not in possession of the full facts Last edited by Phil G4SPZ; 22nd Dec 2023 at 8:11 am. Reason: Clarity

22nd Dec 2023, 9:22 am	#5
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Did Smiths and other synchronous clock makers use cycloidal gear teeth? Phil, I think that Smiths used the usual cycloidal wheel teeth. On all the metal wheels and pinions, no lubricant. I have a Smiths service manual somewhere which says that, but cannot find it! __________________ Mike.

22nd Dec 2023, 9:30 am	#6
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,749	Re: Did Smiths and other synchronous clock makers use cycloidal gear teeth? Thanks Mike, I think that answers the question! I’ve never seen a Smiths service manual, but there are some excellent drawings and descriptions in T.R. Robinson’s “Modern Clocks”. If you manage to locate your document, a copy or scan would be appreciated by many, I’m sure. Many thanks, __________________ Phil Optimist [n]: One who is not in possession of the full facts

22nd Dec 2023, 4:32 pm	#7
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Did Smiths and other synchronous clock makers use cycloidal gear teeth? Will do, Phil but it might be a while as we're away soon until the New Year and I suspect it's in the garage. Slightly OT but Robinson's book is excellent - I've had it for years now. __________________ Mike.