Brass Rack and pinions designed to run dry?

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dzarren
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Brass Rack and pinions designed to run dry?

#1 Post by dzarren » Wed Sep 09, 2020 5:46 pm

I have a few antique microscopes, and I have been doing fairly well in getting them back into working order.

I have a couple questions about the rack and pinion mechanisms.

Typically a rack and pinion is located in close proximity to a sliding dovetail.
For the dovetails, I typically use a a very light coat of Nyogel 774 VL, which is the lightest in the series of nyogel 774s.
And for the rack and pinion, i would think to use something thicker, and in the past i have used nyogel 774, but the higher viscosity formulations.

Given thier proximity, it is possible for the grease from the rack to contaminate the grease from the dovetail, is this a real concern?

and my main question is, i have heard a few times that some of the rack and pinions, especially the brass or bronze ones are designed to run dry. I understand that brass has some self lubrication properties and what not, but is this really the best plan of action? I'm sure we've all seen instances where a small section of rack was stripped out, and I'm hoping to prevent that, but really thats probably more of a dovetail issue with binding if that happens.

I have heard that the rack and pinions are designed to run dry, and in fact may be damaged by grease, as there is not enough clearance between the rack and pinion to facilitate the needed hydrodynamic action, especially at the higher viscosity. I have also found that when i grease the rack and pinions, i get really sticky ticky sounds as i adjust the focus, from the grease separating and recombining as the pinion runs up and down the rack.


Are these (typically) helical pinions and racks designed to run dry in many cases? I suppose im most interested in the antique scopes, such as an early CZ Jena or similar.

Thanks!

Image

MichaelG.
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Re: Brass Rack and pinions designed to run dry?

#2 Post by MichaelG. » Wed Sep 09, 2020 6:09 pm

I can’t give you anything like a definitive answer ... but can say that I use just a little of either ‘White Lithium Grease’ or ‘Copper Ease’ anti-seize compound.
Neither of these has [yet] caused any noticeable problem.

I look forward with interest to seeing what others use.

MichaelG.
Too many 'projects'

apochronaut
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Re: Brass Rack and pinions designed to run dry?

#3 Post by apochronaut » Wed Sep 09, 2020 7:12 pm

I would seriously doubt it. Old microscopes were required to function just as smoothly as modern ones. The idea of dry gears doesn't conjure up a vision of silky smooth action and where the rack is brass and the pinion steel, which is a common metal combo., the wear would begin immediately, if not protected by wear resistant lubricant. The grease also acts like a clutch, limiting movement sufficiently, so as to slow down and control the focus.
One microscope from the 30's I received had never been used, and it had a light but definitely there, vaseline like grease on the rack and pinion.
Last edited by apochronaut on Thu Sep 10, 2020 12:28 am, edited 2 times in total.

MicroBob
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Re: Brass Rack and pinions designed to run dry?

#4 Post by MicroBob » Wed Sep 09, 2020 7:39 pm

Hi together,
the combing action of these gears involves a sliding action and doesn't hold up well without lubrication. Brass (copper/zinc) is not as nice as bronze (copper/tin) as a friction partner. Stripped gears are often the result of dropped instruments or of forcing gummed up movements (move, or...! :lol: ).
In the typical antique shop find probably all unsighly old grease was wiped away an no new grease was applied, just for show anyway, who uses an old telescope!

Bob

patta
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Re: Brass Rack and pinions designed to run dry?

#5 Post by patta » Thu Sep 10, 2020 4:23 pm

I don't know either; here a mix of considerations:
most rack and pinion I've seen, for big machines, steel on steel, are all lubricated, abundantly.
For telescope focusers, a manufacturer recommends motorbike chain grease, as it doesn't collect dust.
The few microscope focusers I've dismantled showed old grease traces.
The manual of my old Wild microscope threatens me not to dare to lubricate anything. After 50 years I would disobey...
The Whale oil was the officially recommended lubricant - impossible to find now.

A manual about clocks lubrication tells where "not to oil" at page 19. Do not oil pinions and wheel teeths!
https://watchmaking.weebly.com/uploads/ ... atches.pdf

The truth may be buried in the ancient Zeiss archives of Jena.

EYE C U
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Re: Brass Rack and pinions designed to run dry?

#6 Post by EYE C U » Thu Sep 10, 2020 7:49 pm

GUN OIL WORKS GREAT

MichaelG.
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Re: Brass Rack and pinions designed to run dry?

#7 Post by MichaelG. » Thu Sep 10, 2020 8:10 pm

patta wrote:
Thu Sep 10, 2020 4:23 pm
The manual of my old Wild microscope threatens me not to dare to lubricate anything. After 50 years I would disobey...
The Whale oil was the officially recommended lubricant - impossible to find now.
.
Here’s an interesting page:
https://www.scran.ac.uk/packs/exhibitio ... icants.htm

MichaelG.

.
Edit: It appears that general access to scran.ac.uk is only free until the end of October.
Too many 'projects'

apochronaut
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Re: Brass Rack and pinions designed to run dry?

#8 Post by apochronaut » Thu Sep 10, 2020 9:16 pm

Nye Lubricants, which many including myself use for microscope oils and damping greases, cornered the market on fish jaw oil in 1869, shipping 150,000 gallons of it worldwide. It was made from porpoise and blackfish heads and was favoured for watches and fine machinery. They never branched out to compete with Vitalis and Wildroot for the hair oil market. A shame.. Fonzie could have not only jumped the shark but smelled like one too !!

Element 56
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Re: Brass Rack and pinions designed to run dry?

#9 Post by Element 56 » Fri Sep 11, 2020 1:01 am

The wear your seeing on racks is likely abuse. If the pinion turns hard stop! There's a problem!

I lube the dovetails and the pinion shaft but only apply a very light film of grease to the rack. However I don't lubricate all racks all the time. There's probably a lot of different opinions on this so I would say do what you feel is right.

I recall reading about specific greases formulated to be used in close proximity with other greases without cross contamination but I don't remember what, where, when etc... I also found a product once that is applied before your lubricant and is supposed to keep it from ending up where you don't want it. Kind of like a primer of sorts.

However I do not see a reason to use two different types in this application. Just lubricate the dovetail as you normally would and put a light film on the rack with the same. I've been using a Kluber ISO Flex or Super Lube. Either of these would suit.

Kirby

MichaelG.
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Re: Brass Rack and pinions designed to run dry?

#10 Post by MichaelG. » Fri Sep 11, 2020 5:56 am

Element 56 wrote:
Fri Sep 11, 2020 1:01 am
I also found a product once that is applied before your lubricant and is supposed to keep it from ending up where you don't want it. Kind of like a primer of sorts.
These are known as ‘Eplilames’ ... used in watches, and available from several suppliers
illustrated example: http://www.unimatec-europe.com/index.php?id=147

I doubt it would be cost-effective on a microscope, except perhaps as protection for an exotic optic.
indicative pricing, and technical information, here: https://www.cousinsuk.com/category/epilames

MichaelG.
Too many 'projects'

patta
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Re: Brass Rack and pinions designed to run dry?

#11 Post by patta » Fri Sep 11, 2020 9:41 am

Just realized that I live in Norway, whaling is still going on and the oil is on sale! No clock grade though, only "oil for dog fur" commercially available. They are discussing now if to reopen the hunt for porpoises... I'm sure in Japan they still make such lubricants.

I found an article by Carl Hunsinger about overhauling of Olympus focuser; about greasing the rack:
P.29 "This step is optional and may be omitted if the equipment will be used in an environment where debris might accumulate on a greased focus rack, which would foul the rack-and-pinion mechanism."
http://alanwood.net/olympus/downloads.html

Hobbyst46
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Re: Brass Rack and pinions designed to run dry?

#12 Post by Hobbyst46 » Fri Sep 11, 2020 10:09 am

patta wrote:
Fri Sep 11, 2020 9:41 am
Just realized that I live in Norway, whaling is still going on and the oil is on sale! No clock grade though, only "oil for dog fur" commercially available. They are discussing now if to reopen the hunt for porpoises... I'm sure in Japan they still make such lubricants.

I found an article by Carl Hunsinger about manteinance of Olympus R&P focuser, and he elegantly escapes the grease vs dry debate:
P.32 "Note: Be sure to omit grease from the teeth of the ... gear if grease was omitted from the brass rack"

http://alanwood.net/olympus/downloads.html
Actually, Carl did not "escape" the debate but rather described it in detail, in his other article:

"Complete Teardown, Cleaning, and Reassembly of the Olympus BH‐2 Sliding Focus Block", section "Recommended lubricants".

that can be reached via the same link. obviously, in theory, a perfect mechanical device INITIALLY functions without lubrication, then many factors accumulate to change the conditions.
For example, microscopy in a clean room lab is not the same as microscopy in a busy application lab, clinic, environmental or whatever.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

patta
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Re: Brass Rack and pinions designed to run dry?

#13 Post by patta » Fri Sep 11, 2020 10:19 am

Yep Hobbyst46 corrected in the meanwhile you were writing, there is so much to read on Alanwood pages...thanks for the rectification. The document you cited has the best arguments found so far.

So we are discussing about a delicate balance between smoothness, wear and debris accumulation.
The optimal may be this laborious solution: solid wax coating. It is done for bike chains, where you have exposure to debris but still need lubrication; the chain is soaked into molten wax, which then solidify into a thin film. Some lubrication, little debris collection. Maybe interference with the fine gear tolerances...
Last edited by patta on Fri Sep 11, 2020 4:01 pm, edited 1 time in total.

BramHuntingNematodes
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Re: Brass Rack and pinions designed to run dry?

#14 Post by BramHuntingNematodes » Fri Sep 11, 2020 12:47 pm

Drying PTFE suspensions are also used on bike chains. They have a are my smell, but I use them on vise screws when the chips will be flying, but this seems like a particularly bad environment for microscopes.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

Element 56
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Re: Brass Rack and pinions designed to run dry?

#15 Post by Element 56 » Fri Sep 11, 2020 7:37 pm

MichaelG. wrote:
Fri Sep 11, 2020 5:56 am
Element 56 wrote:
Fri Sep 11, 2020 1:01 am
I also found a product once that is applied before your lubricant and is supposed to keep it from ending up where you don't want it. Kind of like a primer of sorts.
These are known as ‘Eplilames’ ... used in watches, and available from several suppliers
illustrated example: http://www.unimatec-europe.com/index.php?id=147

I doubt it would be cost-effective on a microscope, except perhaps as protection for an exotic optic.
indicative pricing, and technical information, here: https://www.cousinsuk.com/category/epilames

MichaelG.
That't it, Michael! Thank you!

Yes, not cost effective nor is it necessary. Keep it simple! The rack and pinion has worked fine for years without a bunch of fancy lubricants. :mrgreen:

Kirby

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