why do clock part alternate between steel and brass

Discussion in 'General Clock Discussions' started by rodlloyd, Jan 28, 2018.

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  1. rodlloyd

    rodlloyd Registered User
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    I have noted that clock parts that interact tend to alternate between steel and brass.
    Steel pivot goes into brass plate
    Brass wheel teeth act on steel pinions
    etc etc

    Can someone explain why this is
     
  2. novicetimekeeper

    novicetimekeeper Registered User

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    It has been that way for around 500 years. It seems to provide the best longevity. Given how expensive brass was 500 years ago I'm sure they would have gone a different route if they could.
     
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  3. dAz57

    dAz57 Registered User

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    Because similar metals tend to wear faster, you can see this in some Korean clocks where you have a mainspring great wheel meshed to a brass pinion, over a short time the wheel can nearly cut through the pinion to the point the mainspring will suddenly let go.

    Brass on brass is used in low load gearing like on dial trains
     
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  4. gmorse

    gmorse Registered User
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    Hi rodlloyd,

    There's also an effect known as galling, where two similar metals in contact and moving under pressure tend to 'weld' together. Some very early German timepieces were made with iron plates and arbors, but I think these designs were fairly soon replaced by the brass/steel combinations. As DAz57 says, some brass on brass wheels do survive, some running on brass posts, where the pressures are very low and the clearances are relatively large.

    Regards,

    Graham
     
  5. chronologiker

    chronologiker Registered User

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    In mechanics, the use brass-steel is called an ideal combination.

    - Brass-steel requires no lubrication and is still wear-resistant.
    - Brass steel knows no contact corrosion

    The rule for brass-steel combination is:

    The component that will wear out is made of steel. In clocks therefore the gears are made of brass; the pinions are made of steel

    Chronologiker
     
  6. rodlloyd

    rodlloyd Registered User
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    Thank You Chronologiker
     
  7. shutterbug

    shutterbug Moderator
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    It's also a good policy to use brass tapered pins in steel holes, and vise-versa. They won't bond together that way and cause headaches down the road.
     
  8. chronologiker

    chronologiker Registered User

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    Thank you shutterbug. Yes, brass and steel can not weld together.

    About the rule, components that will wear out, to make out of steel. (Because steel is harder than brass.)

    For the first moment it will come as a surprise that the steel part will wear off and not the brass part. The explanation is:

    The abrasion of the steel parts (= steel molecules) will penetrate into the surface of the brass part. These hard molecules provide further abrasion on the steel part.

    As a result, the steel part is worn in the long term and not the brass part.

    Chronologiker
     
  9. Ralph

    Ralph Registered User
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    I had different thoughts on it. Dissimilar materials is a positive, but the wear can also be attributed to the fact steel pinions generally get, 3, 4, 5, 6 and maybe more engagements, then the brass wheel, depending on the ration of pinion teeth to wheel teeth. Also, particulate matter can find it's way into the movement and can embed itself into the brass wheels and in turn accelerate wear on it's mating pinion.

    ..and a reminder to never oil the wheel/pinion teeth. Particulate will stick to the surfaces and exacerbate the conditions for wear.

    IMHO
     
  10. rodlloyd

    rodlloyd Registered User
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    Very good point. What about taper pins at the pillar. Now we have both brass plate and steel pillar?
     
  11. novicetimekeeper

    novicetimekeeper Registered User

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    All my clocks have brass pillars.
     
  12. chronologiker

    chronologiker Registered User

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    Ralph, it's really how I wrote. The steel part will wear off more than the brass part.

    Another example: In an engine, the cylinder is made of aluminum, the piston ring of steel.

    What do you have to change when the engine gets old: the piston ring or the cylinder?

    Definitely the piston ring. The reason I have described above.

    Chronologiker
     
  13. novicetimekeeper

    novicetimekeeper Registered User

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    Don't they use cylinder liners?
     
  14. chronologiker

    chronologiker Registered User

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    Novicetimekieeper, whether with cylinder liners or without- the piston rings are much harder.

    And therefore, the piston rings have a high wear and must be replaced in any case.

    Chronologiker
     
  15. David S

    David S Registered User
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    Anyone here remember the Vega 2300 engine? I know we digress but that was a disaster.

    David
     
  16. novicetimekeeper

    novicetimekeeper Registered User

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    I think that is because of the point Ralph made, the piston rings have a very small surface area in contact with a much larger surface area, so the rings wear faster. The rings are changed for oversize rings though, which would suggest the liners do wear.

    I'm in agreement about the brass/steel thing, as I said it has been tried and tested for around 500 years, but I don't think we need to back it up with false comparisons.
     
  17. Uhralt

    Uhralt Registered User
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    The car engine cylinder may not be such a good example. Here it is not the material that causes the difference in wear.The aluminum piston doesn't really touch the cylinder wall. The diameter of the piston is slightly smaller, so there is no abrasion. The piston rings however are wider and do touch the cylinder wall and do it under pressure.

    Uhralt
     
  18. David S

    David S Registered User
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    I think we are getting off base here. The piston skirts certainly do experience wear and in the Vega example they had to treat them to resit wear.

    David
     
  19. chronologiker

    chronologiker Registered User

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    Novicetimekeeper, these are not inadmissible comparisons.

    This phenomenon is not only the result of long experience in mechanics, but also secured by metallurgical investigations.

    It has been a long time since I completed my training as a mechanic, but this knowledge is still taught today.

    Chronologiker
     
  20. SGNT

    SGNT Registered User

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    Ha. I agree and remember that car very well. The only thing good about that one (the Vega) was the relative ease with which a V8 motor could be dropped in there.
     
  21. David S

    David S Registered User
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    Nice to see a bit of humour here, thanks SGNT.

    Of course you had to make sure the body didn't rot out before you got to use your small block chevy.

    D
     
  22. MartinM

    MartinM Registered User

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    I agree that the engines comparison is less than apt.
    Up until quite recently both engine blocks (Or cylinder liners, as used in aluminum blocks) and piston rings were made of cast iron alloys.
    That said... The Vega was the first time I encountered a car with a circuit breaker on the ignition, tied to the water temp and oil pressure. And, if you bypassed that, there was a lead plug that disappeared on an overheat as a tattletale. Basically, they knew their product was prone to self destruction.
     
  23. Bill Ward

    Bill Ward Registered User
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    Use a brass pin in a steel pillar. The pin won't get stuck on the surface of the plate, but it sure will in a mating hole.
     
  24. chronologiker

    chronologiker Registered User

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    #24 chronologiker, Jan 31, 2018
    Last edited: Jan 31, 2018
    Gentlemen, the mechanics rule quoted above is nonetheless valid. Always the harder component will wear off and less the soft. And this rule even applies to surfaces of different sizes.

    A last example, but now with the same size surfaces:

    If you measure in an old engine, the piston pin and the piston: What has worn out more: The piston pin or the piston ??

    The correct answer is: the piston pin.

    And this mechanical rule has been known in clockmaking for many hundreds of years. And clockmakers therefore make the pinions of steel, but the gears of brass. And not the other way around.

    Chronologiker
     
  25. MartinM

    MartinM Registered User

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    Actually, the part (supporting your hypothesis) that wears most is the connecting rod. As for any wear between the piston pin and the piston... My experience is that whenever there was measurable 'slap', the pin was always still within tolerance and usable (Not that most folks would) and the wear was in the aluminum piston.
     
  26. chronologiker

    chronologiker Registered User

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    Martin, do you know that the aluminum of the piston is significantly softer than the steel of the piston pin?

    According to your theory, the piston pin should not wear out then.

    But the opposite is true: Compared to the piston, the piston pin is weared out comparatively strong.

    The reasons for that I have tried to explain above. This is proven knowledge in metallurgical research, not my personal hypothesis.

    Chronologiker
     
  27. novicetimekeeper

    novicetimekeeper Registered User

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    I think all this talk of engines is rather misleading. (and IC pistons usually have gudgeon pins which are fixed so there is no aluminium involved, there are designs with free floating gudgeons where presumably wear is an issue))

    Yes, there are good reasons for using the brass/steel mix, it has been used for 500 years, and the reasons are given above. (ignore the engine bits)
     
  28. chronologiker

    chronologiker Registered User

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    Novicetimekeeper, I really do not want to convince you if you want to stay with your opinions!
    But I hope other participants in the forum will understand my examples better than you.

    Chronologiker
     
  29. MartinM

    MartinM Registered User

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    Agree to disagree, I guess.
    In my world... Unless there is some foreign matter introduced, soft main, rod and cam bearings wear out before crankshafts and camshafts BY DESIGN.
    And if foreign matter IS involved. the bearing is destroyed as well.
     
  30. MartinM

    MartinM Registered User

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    I've determined that I must simply be misunderstanding some theoretical point, here.
    If not, I'll need to change out all my tool steel and carbide cutters with aluminum versions.
     
  31. chronologiker

    chronologiker Registered User

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    Martin, yes you misunderstood

    It makes a difference whether a carbide steel bolt has to move for years in an alluminium component or whether you use carbide steel cutting tools for machining other materials.

    Chronologiker
     
  32. chronologiker

    chronologiker Registered User

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    Greetings all,

    I was asked to explain the matter again:

    This is about the wear that occurs when components of different metals slide over each other for a long time. e.g. when gear and pinion of clocks slide over each other. Or a hardened piston pin in the aluminum piston of an engine. Not meant here is the processing of metals! (And lubrication with oil is also not considered here, because gears in clocks are not greased.)

    The mechanical rule says:

    If differently hard components slide over one another, the harder workpiece will preferentially wear off.

    Why?

    Sliding over one another both components will lose molecules due to sliding friction. The molecules of the soft component are thereby ground to dust. The molecules of the hard component, however, will penetrate into the surface of the soft component and get stuck. They thereby form a hard layer which will lead to further erosion on the hard component.

    Ultimately, the wear of the harder component is thus carried out by its own molecules and not by the metal of the softer component. The softer component becomes, so to speak, the carrier metal for the hard molecules of the other component.

    Clockmakers have observed and considered this phenomenon many hundreds of years ago. But of course, they did not know the metallurgical reasons.

    Chronologiker
     
  33. MartinM

    MartinM Registered User

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    Let's say I were to machine and polish the shank of an aluminum bar and the shank of a same-sized HSS drill bit, chuck them up in my lathe and turn them against each other, end-to-end under moderate pressure.
    you're saying the aluminum will stop ablating at some point?
    Or, at least do so at a lesser rate than the drill bit?
    Would there be a better way to test this phenomenon?
     
  34. DeanT

    DeanT Registered User

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    Late to this conversation which has been quite interesting.

    The French adopted the brass/steel wheel combination much earlier than the Germans in the mid 16thC. The Germans converted from full steel movements around 1600 which provides an easy way of dating movements. The English didn't have much of a clockmaking industry pre 1600 but the first lantern clocks post 1600 used the brass/steel combination.

    I've attached photos of two German clocks. One has the brass wheel combination but still uses steel for several wheels and the barrel caps. It dates to 1600. The second is a full steel movement apart from the verge wheel and dates to 1580's.

    IMG_2799.JPG AD4E3029-2DC9-4FEB-AAE9-B96E287B780F.jpeg
     
  35. mauleg

    mauleg Registered User
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    Not to dispute the theoretical aspects presented previously, but rather, trying to understand the following: If the steel is wearing, but the brass is not, why do we see older plates with egg-shaped bushing holes (where the bushing was previously installed due to elongation of the hole in the original plate), but pivots not significantly reduced in diameter when compared to the pivot on the opposite end of the wheel?
     
  36. Jim DuBois

    Jim DuBois Registered User
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    Wear in a material is based on a number of fairly well understood and simple concepts. How much mechanical pressure is involved? What is the strength of the materials involved? What are the surfaces of the materials and how smooth can they be made to minimize friction? What is their ability in the case of clocks to retain lubrication? How hard are the materials and can they be made harder? How hard are the materials to work and make the required parts? So, in a clock the iron or steel parts are substantially stronger per unit of measure than is brass. Iron or steel can be highly polished. Brass is slightly porous and harder to make very hard, and it lacks the strength of iron or steel by a factor of 2 or more. A pivot of .015" done in steel can be highly polished, it is quite strong for its use as a pivot. Now consider that pivot done in brass....not going to work long or well is it? Then there is the amount of work involved in casting brass vs casting iron/steel. And making clock wheels out of iron/steel and working it into a proper wheel, crossed out, smoothed, and teeth cut takes a lot more work than to do it in brass. Cutting pinions in steel requires a lot less work than cutting the wheel in steel does it not? So, we sort of fell into brass wheels mating against iron/steel pinions sort of a default. It makes far better sense and is easier than other combinations. As we see demonstrated by the Germans in or about 1600? Thanks Dean for the photos of these 2 very early German clocks. I had not thought that through as we don't really see any of those clocks hereabouts....and I don't know of any collectors that are interested in them around here either...we do have a few clocks with iron/tinned wheels from Joseph Ives circa 1860 but they work with iron roller pinions so they really don't support or not support our current discussion. And both the pivots as well as the rollers in the pinions all rolled in brass bushings in those anyway...photo below of one of those clocks

    ives tin plate movement.JPG
     
  37. DeanT

    DeanT Registered User

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    The unusual reason provided for the pre 1600 full steel movements is that steel was cheaper than brass. As brass was expensive it was saved for the visible case although it is easier to work for the wheels. If you look at the older movement it has a steel frame although the nuts holding the frame are brass.

    The earliest known Italian alarm clock dates to 15thC or even 14thC and it was made with brass wheels!

    None of these are mine but are photos of collected over time. All are probably German and pre 1600, the first is weight driven and the others spring driven.

    FrontRight.jpg LeftOpen.jpg statie171.jpg werk171.jpg d5039662x.jpg 91_40065_1.jpg 91_40065_6.jpg
     
  38. DeanT

    DeanT Registered User

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  39. chronologiker

    chronologiker Registered User

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    Dean, thank you very much for your very interesting photos and hints! Wonderful and early clocks you have!

    And a big thankyou to Rodiloyd, who started this very interesting discussion!!

    Chronologiker
     
  40. novicetimekeeper

    novicetimekeeper Registered User

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    As Jim suggested, though he did not directly answer your point.

    The choice of materials is historically probably more to do with cost and manufacturing methods as much as anything else, but the meshing of wheels and pinions at very low rpm and without lubrication is a very different situation to other areas of engineering. Engineers have to rethink gears when it comes to clocks because the tolerances in the gear train are so completely different.

    The wear you see in plates is much more conventional.

    In the 18th century they were experimenting deliberately hardening escape wheels by planishing, but hardening of brass must have been happening all the way through its use to make wheels and plates because of the methods of manufacture. Delaunce and a number of others were trying out extra hardening and in a rather more planned way.

    As well as cost corrosion must have been a consideration, 16th century homes would have been quite a difficult environment I imagine, though perhaps our hermetically sealed triple glazed ones are even worse.
     
  41. chronologiker

    chronologiker Registered User

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    Mauleg, I would like to respond to your question:

    In a bearing the pin of a gear wheel is pushed by forces of the drive from the center.Thus, the bearing is always loaded only on a very narrow area, the pin but over its entire circumference.

    And oil also plays a role here: the oil in the bearing will absorb the abrasion and provide an emery effect.

    Result: The bearing will wear off completely unilaterally. Especially with high forces of the drive, old oil and a lot of abrasion.

    So your observation is correct, but it is a bit different to our theme.

    Chronologiker
     
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  42. mauleg

    mauleg Registered User
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    Thanks, Chronologiker. Great explanation which clearly explains the observed phenomena.
     
  43. MartinM

    MartinM Registered User

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    I still don't get how a claim can be made that the brass will wear slower than the steel (regardless of the unilateral pressure) in the plate/arbor clock example as opposed to the same essential factors in a piston/pin. Yes. it's in a single direction, but the plate still wears exponentially more than the arbor.
     
  44. chronologiker

    chronologiker Registered User

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    I'm sorry Martin, but I do not understand your question because Mr. Google Translater is still a very poor translator. (You've probably already noticed the many mistakes in my answers.)

    But I have the hope someone in the forum will answer your question and explain.

    Best Regards!

    Chronologiker
     
  45. MartinM

    MartinM Registered User

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    I was just saying that I see no difference in the clock example and the piston example. Bot are a hard pin in a soft hole with lateral force applied.
     
  46. chronologiker

    chronologiker Registered User

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    Thanks Martin.

    I find it truly amazing that clockmakers observed this phenomenon hundreds of years ago and developed a practical solution for it. Although they were also certainly surprised that not the soft, but just the hard component wears off. That does not sound logical at all.

    Only by modern metallurgical investigations, this phenomenon was explained.

    Best Regards!

    Chronologiker
     
  47. MartinM

    MartinM Registered User

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    This is getting weird. You seem to be indicating that in horology, steel pivots wear faster than brass plates. That's just not the experience most of us have.
     
  48. chronologiker

    chronologiker Registered User

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    As I have tried to explain, pin and brass bearings are a bit different to our theme because of the emery effect with oil.

    Martin, I see, you do not want to believe that metallurgical research proves that the hard molecules of the piston pin will be pressed into the aluminum surface of the piston. And so that at first sight illogical wear of the piston pin will be brought about.

    Chronologiker
     
  49. MartinM

    MartinM Registered User

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    #49 MartinM, Feb 5, 2018
    Last edited: Feb 5, 2018
    Well... This is a clock forum and the shared experience we all have showing that brass plates wear much faster than their mating steel pivots should be the focus of the discussion.
    It's not about my beliefs. It's about our vast combined experience. And when oil is forgotten, the wear is even faster.
    Truth be told, most of the automotive piston assemblies I have encountered have pins that are pressed into the piston and never move. And the motorcycle and small engine assemblies that do never have any measurable wear at that connection. It's always the connecting rod to piston connection that goes out of spec, first. undeniably due to the smaller contact area. The pin wears measurably when there are steel needle bearings. The bronze bushing wears faster than the steel pin when there are no steel needle bearings.
     
  50. novicetimekeeper

    novicetimekeeper Registered User

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    As I said earlier in the thread, engines are not clocks and they don't make very good examples of what happens in clocks.

    One of the main jobs of oil in engines is cooling, not an issue in clocks, and transporting wear particles away from bearing surfaces, again not done in clocks.
     

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