Old bearings never die…

[gerry maddenParticipant @gerrymadden53711]

[gerry maddenParticipant @gerrymadden53711]

To help out a chap re-building an old aircraft, I'm looking for a couple of old bearings. He wants to maintain authenticity, so the challenge is that they must be of SKEFCO manufacture. The designations required are RL10 and RL4. These are double-row self aligning type in which the inner ring, cages and balls are free to swivel inside the outer ring..

I have tried various small businesses that specialise in procuring old bearings but with no luck. I feel sure that somewhere in the country these bearings could be hiding in private "collections" just waiting to find a purpose in life.

So does anyone have either of the two sizes that they would like to sell, or know of anyone that might be worth contacting ?

Ps, a little cosmetic damage or corrosion may not be of concern.

Gerry

[Neil AParticipant @neila]

Perhaps I am mistaken, but isn't the old Skefko Ball Bearing Company Ltd our modern day SKF ?

They still manufacture these bearing sizes.

I'm not sure how far maintaining authenticity compares to safe functionality.

Neil

[gerry maddenParticipant @gerrymadden53711]

Yes Neil, you are correct on that. But apart from different marking, the SKF version would not be manufactured in the UK. The original aircraft manufacturer wanted every part of the machine to be made in the UK and the current restorer wishes to maintain this philosophy if possible. But of course SKF, Fafnir or Hoffmann remains as an ultimate option.

Gerry

[BazParticipant @baz89810]

Just out of interest what aircraft is it and does he intend restoring to air worthy condition or just as a static display.

[old martParticipant @oldmart]

Wouldn't the CAA require certificates for bearings such as these if they are to be used in an aircraft? I now notice that the bearings do not have to be airworthy, just original. I will ask questions at the museum, we have thousands of new bearings but for helicopters, and they will not be listed by the bearing size, but by the aircraft manufacturers part numbers as only the proper parts are allowed, not the generic names.

Edited By old mart on 03/09/2023 17:12:41

Edited By old mart on 03/09/2023 17:18:33

[gerry maddenParticipant @gerrymadden53711]

Baz – I'm afraid I cant divulge the type at the moment, but it is likely to be airworthy.

Old Mart – if I can get the original design and manufacturer, there should be no issue with airworthiness. Thanks in advance for your efforts,

If its of help, the dimensions of the two bearings are:

RL10: 1.1/4" x 2.3/4" x 11/16"

RL4: 1/2" x 1.5/16" x 3/8"

Gerry

[duncan webster 1Participant @duncanwebster1]

Hmm, cosmetic damage and corrosion not a problem, but a different part number on the same bearing is.

[clogsParticipant @clogs]

an almost impossible task to obtain original bearings I'd say///////

i wonder how many got scrapped in the past……?

on the subject of unobtainium……

anyone got/knows of a frame and forks for a 1930's four cylinder Indian m/cycle…….

or any other stuff…been trying to get mine ready for the road for 40 years…….lol……..

[CirclipParticipant @circlip]

If the A/C is of WWII manufacture, chances are, the SKEFCO bearings were flown over from Scandinavia in the bomb bay of a Mossie on the bearing run.

Regards ian.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Gerry, I don't know if any "SKEFO" bearings you are after are available anywhere, but RL 4 and RL 10 are equivalents to NLJ 1/2 & NLJ 1-1/4 respectively, which were made by Ransome & Marles Bearing Co. Ltd./ Ransome Hoffman Pollard Limited.

Regards Nick.

[gerry maddenParticipant @gerrymadden53711]

Circlip, its actually before WWII, but even so, I think the SKEFCO name was reserved only for the manufacture in UK registered arm of SKF. …but of course one never really knows what went on in those days

Gerry

[gerry maddenParticipant @gerrymadden53711]

Thanks Nick, yes they may be options if Im unsuccessful in the search. I have already been offered the Hoffmann versions and if it was up to me I'd use these as its the place I first started working.

[Robert Atkinson 2Participant @robertatkinson2]

Requirement seems a little obsessive to me. Certanly during the working life of the aircraft they would not have bothered about the make. That is why there are standard size designations. I've actually received "refurbished" certified aircraft bearings where the two races had different manufacturers (VC10 flap drive thrust bearings). It was queried with the supplier and they confirmed it was acceptable.

Robert.

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by gerry madden on 04/09/2023 10:30:59:

Circlip, its actually before WWII, but even so, I think the SKEFCO name was reserved only for the manufacture in UK registered arm of SKF. …but of course one never really knows what went on in those days

Gerry

Hi Gerry, SKEFCO had factories in Luton and Sundon, Bedfordshire, and Irvine, Ayrshire, and sales & service throughout the UK.

Scans from my 1969 SKF equivalent book.

Regards Nick.

[John Doe 2Participant @johndoe2]

Posted by duncan webster on 03/09/2023 23:51:53:

Hmm, cosmetic damage and corrosion not a problem, but a different part number on the same bearing is.

Gerry said "a little" cosmetic damage or corrosion. e.g. a few light dings or some surface discolouration in non critical areas would be OK. Heavy rust or pitting in the ball races wouldn't !

Re the part number: I would think that the correct part number also specifies operating heat range, materials, working load, max rpm, and a host of other parameters, as well as basic dimensions. These would need to be correct for the aircraft to be signed off by the CAA? A different part number might have all the correct dimensions but only half the working load, or not certified for use below 0°C, for example.

[gerry maddenParticipant @gerrymadden53711]

Posted by Robert Atkinson 2 on 04/09/2023 10:37:37:

Requirement seems a little obsessive to me. Certainly during the working life of the aircraft they would not have bothered about the make. That is why there are standard size designations.

Not always so Robert. Even in some mundane applications that call up standard catalogue products, the cage type is considered important enough that certain manufacturers can be precluded from supplying. One example that comes to mind from my memory banks was the spot-welded steel cages that became popular in 1970s 'pop met' single row ball bearings. And it all happened again with the trend toward plastic cages in 1990s.

Gerry

[gerry maddenParticipant @gerrymadden53711]

Just to (almost) close this one, I can let you know that a kind member of this forum came up with exactly the RL10 bearing I needed. It came in a SKF box but surprisingly the rings were actually stamped with SKEFCO and GT. BRITAIN, and had the same type of pressed-steel cage as the possibly 100 year old original part on the aircraft. What a great forum this is !

The original bearing was unusable due to its inability to freely self-align. After a good inspection and measurement I put this down to a serious ovality and shrinkage of the outer ring, very likely as a result it being subjected to the heat of a fire at some point in its life.

I will continue my hunt for a RL4 of similar vintage and source.

Gerry

[John AbsonParticipant @johnabson65530]

Interesting to read this thread, albeit a bit late to the party; Skefco was the brand name for products of the British factories of SKF (as well as in India, South Africa and Australia) until the globalisation of the group's production which started in the late 60s, when the brand was progressively dropped – the last few bearings branded Skefco were made in the late 70s for the aftermarket, subsequently replaced by the SKF brand. If your friend wants to stay safely up in the air, country of origin is the least of their worries, noble as it might have seemed at the time. From the mid 70s, SKF in the UK has been called just that – SKF (UK) Limited.

I realise you've already sourced some of your requirements, but I assume the application is in some way safety-related. Specs for bearings are historically surprisingly relaxed, usually stipulating the maker's designation, thus making them a 'black box' design following whatever General Catalogue specs were applicable at the time. More recent applications (e.g. jet engine main shaft bearings) are the complete reverse with the customer's design and specifications being hyper-detailed though (ultimately) often following the bearing supplier's design rules for the internal parameters; these products are tested destructively to the extreme for design validation.

Corrosion – be careful. If there's any sign of external corrosion (under an eye-glass) assume there is some developing on the contact surfaces (balls and raceways), which classes the bearing as 'failed'.

Cages – good point; most SABB (self aligning ball bearings) nowadays have nylon (plain or glass-filled) cages which aren't tested at below zero temperatures and get brittle. Don't use them unless their use is specifically prescribed. Steel or brass cages are what is needed.

If you cant find original parts, try HB Precision in Honley, but tell them the application.

Good luck with your quest,

John

PS as a footnote, I worked for SKF from 1978 to 2020, initially at Luton (becoming company QA manager including being CAA/JAA and MoD release authority) then ultimately becoming Head of Quality for the entire group, based in Gothenburg. A fascinating career with many twists and turns, but never lost my love of getting my hands dirty and always had a workshop of my own.

Edited By John Abson on 29/09/2023 16:24:59

Edited By John Abson on 29/09/2023 16:26:02

[gerry maddenParticipant @gerrymadden53711]

John, thanks for your post. But don't worry, all is under control safety wise.

However, being and SKF man, I wondering if you can help with manufacturing codes? My 'new' (1970s) bearing has the letters WTLD stamped on the outer ring. The original bearing had H6 stamped on the inner ring. From my own experiences, such markings generally indicate the manufacturing plant, manu. line or some other internal manufacturing-related information. Would you happen to know what these letters signify in the case of these two SKEFCO bearings ?

Gerry

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Gerry, there is a vintage SKF RL4 on ebay at the moment. Some numbers & letter combinations denote the clearances between the the bearing elements, but I don't know if those you have are.

Regards Nick.

[gerry maddenParticipant @gerrymadden53711]

Nicholas, you are right too ! I'd missed that. Thanks for letting me know.

G.

[Robert Atkinson 2Participant @robertatkinson2]

Posted by gerry madden on 04/09/2023 21:31:47:

Posted by Robert Atkinson 2 on 04/09/2023 10:37:37:

Requirement seems a little obsessive to me. Certainly during the working life of the aircraft they would not have bothered about the make. That is why there are standard size designations.

Not always so Robert. Even in some mundane applications that call up standard catalogue products, the cage type is considered important enough that certain manufacturers can be precluded from supplying. One example that comes to mind from my memory banks was the spot-welded steel cages that became popular in 1970s 'pop met' single row ball bearings. And it all happened again with the trend toward plastic cages in 1990s.

Gerry

Normally if there are specific requirements outside those controlled by the standard specification of a part the specification number would not be called up in the drawing or parts list. Typically either the equipment OEM would specify their own part number or they would call up a specfic part manufacturers stock or part number. This part manufacturers number might be a special for the aplication. Using their own part numer has the added benefit of controlling the market. Sometimes a standard part will be purchased and then one or more of inspection (often for specific characteristic(s). test, modification, treament carried out before using their own number for the part.
For aviation at least this means you should always refer to the approved documentation. Just because it says ACME 1234 on the part doesn't mean you can just buy an ACME 1234 and fit it. The OEM may have bought thousands of ACME 1234s and then selected the "best" ones for their application.

Robert.

[John AbsonParticipant @johnabson65530]

Hello Gerry,
Year of manufacture marking would have been a single letter – on this vintage it would have been stamped on the soft outer ring before HT and grinding . Kicking myself now for not retaining a personal copy of the date tables! There was a workaround for work in progress left over at the end of the year – a single dot was chemically etched at final assembly to the right of the letter on the hardened and ground ring face to indicate 'year plus one'. Current methods of laser marking don't half make such things easier.

WTLD isn't a familiar part of the bearing designation – it may have been a 'special' for a specific customer. Internal clearance (axial in this case) would be denoted by a letter C followed by a number: 2 for one class less than Normal; 3 for one class more,etc.
J.

[gerry maddenParticipant @gerrymadden53711]

John, WTLD is definitely not part of the designation – I should have made clear that the positioning of this stamping on the ring, relative to the stamping of its basic designation. So you don't have your date tables any more, but what about the site of manufacture ? Since the bearing was made in this country there are only two possible sites, Luton and Irvine. One or more of these letters should define that, should it not ?

Robert – I'm not quite sure where we are going on this , but yes you are basically correct in what you say in terms of the ideal aviation procurement procedures. But it's a fact of life that even in the aviation industry, as one moves down the technical spectrum from the turbine main-shaft application to, lets say, a seat adjuster mechanism, OEM bearing specs become increasingly vague. I haven't said where my RL10 sits on the spectrum and that was deliberate on my part to avoid excessive thread elongation. I did however hint that the original bearing was around 100 years old so I will leave to your imagination the quality of the 'approved documentation' that was written in that period, when the art of rolling element bearing manufacture (never mind of aircraft) was in its infancy.

Gerry

Edited By gerry madden on 01/10/2023 01:03:21

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