Naval assets

There has been plenty of debate about the wisdom of our Royal Navy trying to keep its place at the top table by building two large aircraft carriers. I believe that our then fat leader's lead advisor - Dom the Com - arrived with a mission to get them cancelled, but finding when he looked into it that we were so far in, that getting out was going to be prohibitively wasteful and expensive. We were stuck with them, even if we could not afford the helicopters and aeroplanes to go on both of them. And it now seems that we can't afford the support groups which go with them, which go to make up a real carrier task force, either. Carrier task forces being a business in which the US dominates the world, at least for now.

So I was interested to read this morning of problems with something called shaft couplings. It seems that these carriers are too big to have one piece propeller shafts, so the sections need to be coupled together somehow. And then, in any case, the propeller end needs to be coupled to the propeller, and the engine end needs to be coupled to the engine. And a thrust plate somewhere along the way. Couplings which are going to take a lot of wear and tear during the life of a ship. Couplings which one really do not want to have to take apart very often.

First, I wondered whether, here in the UK, we have the capacity to make such shafts at all anymore? Or do we have to rely on the US, India and China to do the business for us? I remember being told by an engineer for the once proud-to-be British Atkins, that we did not have the capacity to make the rather specialised, central shaft needed for the London Eye, something else that will take a lot of wear and tear during its working life. And tricky to replace. I forget where that was subbed out to.

Second, who makes the couplings? What do they look like? On which Bing suggested that the people at reference 1 are big into couplings. A big Swedish company, operating all over the place, as can be seen from references 2, 3 and 4. And the address of reference 5 suggests that they are big enough to have a sophisticated document publishing operation.

It seems that in the olden days you might have had mechanical couplings involving cutting slots in the shafts to be coupled, but that these days friction joints are preferred. And SKF go one better by offering joints that do not involve tapers - expensive to machine - or heating the female end or cooling the male end to make the fit. Rather, joints that are fitted together by pumping lubricating oil into them, and then allowing the oil to drain out to make the friction joint. At least I think that is the story at reference 5. Something to be studied one quiet afternoon.

PS 1: I remember visiting Portsmouth as a child, when the anchorage behind the carriers in the snap above was full of ships, mainly frigates and destroyers, left over from our glory days, lined up before heading off to the breakers. Another business which I think is largely subbed out to India and Pakistan these days.

PS 2: later: as I now recall, the central shafts of the windmills of old used to be made of wood. Maybe with just a touch of iron strapping by way of reinforcement.

References

Reference 1: https://en.wikipedia.org/wiki/SKF.

Reference 2: https://www.skf.com/group.

Reference 3: https://www.skf.com/uk.

Reference 4: https://www.skf.com/uk/products/power-transmission/couplings.

Reference 5: https://cdn.skfmediahub.skf.com/api/public/0901d1968072ac3e/pdf_preview_medium/0901d1968072ac3e_pdf_preview_medium.pdf.

Reference 6: https://maritimepage.com/ships-propeller-shaft-thrust-block-shaft-bearings/. The source of the propeller shaft. Bing turned up the thrust block - an example of which I remember seeing at the bottom of HMS Belfast, as can be seen at reference 7 below.

Reference 7: https://psmv5.blogspot.com/2022/03/belfast.html.