Why Use Gold for Gears, when Gold is Soft?

[zambranonyc]

Dear Board Members:

Why would RR watches sometimes have gold trains? For cosmetic reasons only? Was gold used to fancy up a movement to a higher grade?

But isn't gold a very soft metal? So why use it to make hard-working gears?

OR MAYBE, those gold center-wheel gears were steel on the inside and just gold-filled? But if so, then the gold surface would wear off with use, no?

And speaking of wear: the use of jewels presents a problem:

How can the end of a steel pivot last, when it turns on a harder-than-steel jewel? Hardness-wise, this is not a symmetrical arrangement yet it works. Why?

Thanks. oz.

[Robert Sweet]

Dear Board Members:

Why would RR watches sometimes have gold trains? For cosmetic reasons only? Was gold used to fancy up a movement to a higher grade? In my opinion, yes.

And speaking of wear: the use of jewels presents a problem:

How can the end of a steel pivot last, when it turns on a harder-than-steel jewel? Hardness-wise, this is not a symmetrical arrangement yet it works. Why?. Oil prevents wear

Robert

[terry hall]

There are some OLD discussions here regarding gold trains....

it is believed they are either 'filled' or plated after being polished...

I think Don D. indicated a description in the Halligan archives, but was not able to find a blueprint...

from memory of past discussions...
Many gears in the train do not have high stress loads, so wear is not an issue... thoughts were they ran 'smoother'...


RE: jewels, pivots...
it is common practice in many moving applications for a harder, wear resistant surface to support a 'softer', "sacrificial", replaceable component... also there is less friction on this harder, polished surface The Oil does prevent wear, as Robert indicates.

Think of this point... a 7 jewel watch... no plate jewels... the pivots in the plate wear... the jewels prevent this and provide a simpler repair when the pivot holes in the plate become elongated.

[walthambarmy]

Most cars have "soft" metal main and big end bearings. These "soft" bearings run on the oil film. It is not until the oil film is not there that the bearings (catastrophically) fail. Hence the need for adequate bearing lubrication on a regular basis. (I answer this question speaking as an engineer but the horology principal should be the same-regular cleaning and oiling will prolong the life. Well! That's my opinion for what it's worth!:)

[Don Dahlberg]

Watch gears are not lubricated. They do not rub on each other, they roll on each other.

Yes, the Hamilton wheels were gold plated. I have posted blueprints of the center wheel for the 992B before. Gold may have given them a smoother surface, but probably no real advantage.

Don

[zambranonyc]

Thank you all. Questions asked and well answered.

oz.

[Andy Dervan]

Oz,

Gold plating the brass wheels and plates reduces corrosion, because gold is very inert material. For example, gold crowns in your mouth survive very well over many years actually better than many synthetic materials!

Andy Dervan

[walthambarmy]

Watch gears are not lubricated. They do not rub on each other, they roll on each other.

Yes, the Hamilton wheels were gold plated. I have posted blueprints of the center wheel for the 992B before. Gold may have given them a smoother surface, but probably no real advantage.

Don

Ah Yes! I forgot that!!! Oil attracts dust. Good point.

[Tom McIntyre]

The gold trains in Waltham watches and in many Elgin and Illinois examples are solid gold, not plated. It is my understanding that the concept of lubricity of "slickness" comes into play. There are metals with a lower coefficient of sliding friction than other metals. Of course, there should not be any sliding if the wheels and pinions were perfectly made, so it is likely mostly a marketing advantage. However, the Waltham Premier Maximus uses phosphor bronze gears because phosphor bronze has a lower friction coefficient than gold does.

It is not true that "gold" is soft. Cast gold or normally worked gold is fairly soft. Gold cannot be heat treated to harden it because it just gets brittle, however it can be work hardened to a fairly high level and this is routinely done when making gold springs.

[mdloggins]

not sure all hamilton "solid gold" wheels are gold plated. Apparently the blueprint for the 992b indicates as such but that doesn't rule out the use of solid gold on earlier watches. Just as likely they were solid gold.

[Tom McIntyre]

I would have thought the 950, 951, 960, 961 and 994 at least were gold.

[mdloggins]

Tom, I think you could include the grade 950b (early s/n under around 3800), 900, 920, 902, 904, 922, Masterpiece and the Grade 400 in your list of solid gold wheels/trains.

I can understand why the 992b might have been plated gold. It was a working mans watch made in huge quantities. And, having a blueprint of it being a gold plated center wheel should not and does not apply to other movements in the Hamilton line. At least not in my thinking anyway.

[Robert Sweet]

If Hamilton used "Solid Gold" center wheels, trains, in any of their pocket watch movements they failed to include that information in their catalogs.

I have carefully looked at the Hamilton "Timekeepers" and catalogs, from 1910 to 1969, and have never seen the word "Solid Gold" mentioned in the movement descriptions.

When advertising the best 16 size movement, the 950, only the words "gold train" were used.

The 950E Hamilton catalog ads only mentions "gold center wheel".

The 950B ad in the 1941 catalog mentions "gold train wheels"

Robert

[Tom McIntyre]

For what it is worth, Waltham almost always refers to gold train wheels rather than solid gold train wheels. If you are selling the items in the UK you would be subject to substantial penalties for calling a gold filled or gold plated item gold.

I think an examination of the material would be in order to actually determine what it is. ;)