Tricks for Bearings
Collected by Ed Thelen
- Bearing Lubrication & Shelf Life from Grant Saviers - Bearings and Melted Grease from Milt Thomas - RAMAC Bearings - restoration from Dave Bennet
Bearing Lubrication & Shelf LifeFrom Grant Saviers to 1401 Restoration Team, 8/24/20040
There is not much value I can add without disassembly of some mechanisms, pull bearings and inspect them etc.
The outside "experts" (grease & bearing manufacturers) disagree with the teams approach. There is NO reason to believe that the visible storage 1402 bearings, which have probably sat for 20+ years (vs 15+ for Arnold's) are going to be in reliable shape.
Some quotes from emails in response to my requests for technical help on the 1401:
As far as the bearings, anything sitting around for over 5 years should at least be relubed. What happens is the oil separates from the thickener in the grease and the grease is pretty much useless.
Al Wysocki, Barden Precision Bearings
(might supply "samples" free of charge for our project)
I've attached a shelf life document to this email. I would assume that the grease in the bearings is not synthetic and therefore very dry. I don't know if it's possible but you would be better off replacing all the bearings with new ones. All the bearing manufacturers tend to use synthetic lubricants now in applications like yours. They are all familiar with our products. You should at least remove one bearing that is easy to access and look at the condition of the grease. That will let you know whether you need to worry about dry grease in the bearings.
Mark J. Coholan Techinical Support Engineer Nye Lubricants, Inc.
- see attachment - THE "SHELF LlFE" OF LUBRICANTS
- see http://www.maintenanceproductsdirect.com/Products_Lubricants/Lubricants.htm
- and http://www.nyelubricants.com/lubeletters.htm to get an idea of the issues and alternatives.
- Another reference (site url not handy) required bearings to be relubricated after two years on the shelf.
- See mscdirect.com grease selections to get an idea of the issues - low vapor pressure greases now exist (didn't in the 60's). very expensive ($20/oz)
THE "SHELF LlFE" OF LUBRICANTS
by Mark Coholan, email@example.com
What is meant by the "shelf life" of an oil or grease? We would define it as the period following its manufacture during which a lubricant stored in its original container could be deemed suitable for use without a re-test of its physical characteristics prior to use.
Lubricants are inherently stable materials. Neither synthetic nor high-quality petroleum oils would be expected to oxidize, polymerize or volatilize over any reasonable (decade-long) period at the usual temperatures of storage. We have regularly checked the quality of certain synthetic hydrocarbon-based precision bearing oils over periods exceeding five years and have detected no significant change in viscosity or neutralization number, which would be the signal properties for degradation.
Hydrocarbons and silicones would likely be least affected by simple aging. Ester oils, where the ester linkage may be subject to a minute degree of hydrolysis in the presence of moisture, could experience greater changes in neutralization number over long periods if moisture is present.
Greases can "age" in more complicated ways. The most likely mode by which time could affect grease quality would be by contraction of the gel structure. If this occurred, significant oil bleed would be evident and the remaining grease would stiffen. In other greases, the gel structure changes in such a manner that the grease becomes softer over a period of time.
The oil separation or "puddling" which can sometimes be found on the top of the grease in bulk pails or drums is usually insignificant when the separated oil quantity is compared with the mass of grease present. Such oils can normally be safely stirred back into the bulk of the grease in the container. Experience has shown us that much of this time-related oil separation can be reduced if the surface of the grease is kept smooth during storage; i.e., don't leave "craters" in the grease.
Oil separation over time is also a function of grease consistency. An NLGI Grade 000 grease could be expected to exhibit pronounced oil separation from the day of its manufacture.
As with oils, there are straightforward bench tests by which grease qualities can be measured and any "age-degradation" determined. These are worked penetration, dropping point, oil separation, and, again, neutralization number.
The "Shelf Life" of Lubricants
It should be emphasized that manufactures' recommendations on shelf life relate only to storage life in the original container. Once the oil or grease has been applied to a bearing or other device, factors which the manufacturer can neither predict nor control will govern lubricant life. A new and different data base on either storage or operating life would have to be constructed. Again, high quality lubricants are inherently stable materials; and long life is a reasonable expectation in the absence of temperature extremes or other hostile conditions.
Our company's normal recommendation on the shelf life of oils or greases is two years after date of shipment. This is a very conservative estimate, and we are prepared to make more liberal recommendations as conditions require.
Customer concerns about shelf life lead to some difficult bureaucratic impasses at times. To avoid being caught with a lubricant stock which has exceeded its shelf life estimate, a lubricant purchaser will stipulate that no oil or grease will be accepted which does not have at least, say, 80% of shelf life remaining. Other purchasers will require "grease no more that three months old". Since many specialty greases, particularly for precision bearings, are manufactured in ten to twenty pound batches, perhaps only once per year, these limitations on shelf life can mean that grease of an "acceptable age" is simply unavailable.
As a practical matter, there is no technical reason to suspect the usefulness of high quality oils or greases after only one year, and only after two or more years should any "age-related re-testing" be considered. We hope the considerations presented here will help relieve some of the concerns which have led to difficult and unnecessary shelf life restrictions.
Bearings and Melted Grease
from Milt Thomas, August 26, 2004
The bearings in the card feed picker knife shaft would /should not have that much ware compared to the card feed roll shaft bearings which ran at higher RPM. I do not think that it would be an easy task to remove /replace all of the ball bearing asmb. They were not considered a field replaceable part. Never did see one fail. Concern here is how dried out is the grease, will it flow around the races when the bearing heats up? I've seen some grease that had gotten so hard it would never lub the balls and race. This was mainly some automotive type greases. This was on a 57 yr old Mercury though.
During my younger days I worked for a fellow in Chicago who bought surplus WWII bearings which were packed in cosmoliene. I would wash them in solvent (do not remember the kind) back in those days it could have been very toxic as anything goes then. We then refilled the bearing with melted grease by dunking the bearings in a grease pot.
I also used the same technique one other time after cleaning a IBM 407 tab machine print wheel analyzer unit with a steam cleaner which melted all of the grease in the shaft end bearings. Melted grease on a hot plate and dipped the end of the shaft in it. When the air bubbles stopped coming out of the bearing I assumed it was full. That was my last attempt at using a steam cleaner to clean ink and oil from the unit. The melted grease worked though. Would need to use the proper grease too. My suggestion is run them until they fail unless you can feel binds or sluggish movement on initial checkout. Remove the drive belt and turn over by hand.
Not sure how much help this is...
from Dave Bennet
Re bearing replacement on the RAMAC restoration, we decided to replace NEARLY all the bearings because they were, as has been stated, very standard and available sizes, they were easy to change and the old ones were rough feeling. I think this was because the grease had settled in them and maybe they were worn to begin with. BTW, small replacement ball bearings are surprisingly inexpensive.
The only bearings we did not change were internal to the powder clutches. For some reason they felt fine and the clutches worked okay - and we had no desire to take the clutches apart if we didn't have to.
There is a very good source for bearings in San Jose called Applied Industrial Technologies. Since most ball bearings have markings on them, you can simply remove them and take them there, where they have cross reference charts so that they can supply exact replacements, most likely right off the shelf.
I personally bought the bearings for the RAMAC, so if I can be of any help I will be glad to do so.