Tangmere

threelinkdave · 2014-06-21

作者 8126: ↑

I went looking through photos of various Bulleids (keeping to them for comparative purposes):

34007 has plain nuts and vertical sawn cotters
34016 has castellated nuts with square slots and vertical sawn cotters
34046 has plain nuts and vertical cotters that I think are sawn
35005 has castellated nuts with vertical cotters (I think, not the clearest shot)
35028 has plain nuts, and cotters folded from strip, with an eye at the top and possibly welded up below the eye (as per the RAIB report)
34067 we know had horizontal sawn cotters and castellated nuts.
Then I went to the books and found a picture of a rebuilt crosshead dated 1963, with the same arrangement as 35028. That didn't surprise me much.

34067 has probably done more mainline miles than any of the others with the castellated nuts, but I doubt the nut is the issue, even with square slots (although I don't like them). I tend to think that the main issue with the horizontal cotter is that once the legs break there isn't even gravity holding it in, and every time the piston reaches the relevant end of the cylinder it's going to try to leave. A vertical cotter will take a bit more time to leave.

Anyway, thought experiment here. We take the cotter out on A.N. Other Bulleid at Waterloo. How far does she get down the SW main line before the pin comes out? I'm not advocating trying this, I'm just wondering whether the cotter is vital or insurance. If it's vital she'll get as far as Tangmere did. If it's insurance, then I think it's more likely that the nut and pin got loose enough that they broke the poorly made cotter, leaving nothing to hold it all together.

Cards on the table: I've never worked on full size steam (or anything bigger than 5" gauge). I am a MechE, but working with very different stuff. Part of the reason for my comments on En3B is that the old spec is so loose that it's practically shorthand for 'that crappy bit of mild steel we found out back'. Yield for EN3B is about half tensile strength, and EN8 (or 080M40) has a higher yield than EN3B's tensile strength. EN16 and EN24 are very good stuff, but in percentage terms they're not as big a step forward over EN8 as EN3B is a step back.

For bolts it's fine, as long as you accept the low strength, and it'll give a long way before actually failing. This isn't a bolt though, I think the most important thing for the gudgeon pin is that it grinds or laps to a good finish, and then stays the same shape. Given the low yield and cylic loading on the gudgeon pin, I wonder if EN3B would start to work and deform at any stress concentrations, reducing the ability of the taper to hold and the nut to preload it, especially if you put the cotter back in the same slot with no changes after taking the pin out to replace the connecting rod bushes. I'm speculating on incomplete information and little experience, there are plenty of people on this forum who probably have a much better idea of things than I do.
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34053 Sir Keith Park plain nut vertical cotter

ADB968008 · 2014-06-21

作者 Spamcan81: ↑

At the time of the Comet losses jet travel in pressurised aircraft was in its infancy and investigators had little prior data to work with. Not a good parallel to draw with 34067 IMO.
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Maybe BA 5390 or AK261 is a closer one to draw parallel to..?
I'm not sure aviation comes into it.. the RAIB would have chosen that route if they felt it pertinent.. instead they selected the Australia incident and went back to the 1960s with the S&C incident but eliminated both and instead fell back on the design (and the lack of following the approved design, but use of LMS practice instead)…

Who made the cotter ?, the RAIB were unable to establish that, and I doubt there weren't many takers lining up to admit it.

std tank · 2014-06-21

作者 ADB968008: ↑

Maybe BA 5390 or AK261 is a closer one to draw parallel to..?
I'm not sure aviation comes into it.. the RAIB would have chosen that route if they felt it pertinent.. instead they selected the Australia incident and went back to the 1960s with the S&C incident but eliminated both and instead fell back on the design (and the lack of following the approved design, but use of LMS practice instead)…

Who made the cotter ?, the RAIB were unable to establish that, and I doubt there weren't many takers lining up to admit it.
Click to expand...

The castellated nut design was a Brighton Works D.O. job for some Standard loco classes, not LMS.

ADB968008 · 2014-06-21

作者 std tank: ↑

The castellated nut design was a Brighton Works D.O. job for some Standard loco classes, not LMS.
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quoting the RAIB report..

60 Many other steam locomotives, notably ex-LMS, LNER and BR standard types, make use of castellated nuts to secure the small end. However, there are significant differences in the design of the small end, notably the use of smaller diameter threads (in which a preload can be more easily achieved), and a bush between the crosshead and the gudgeon pin, with both external and internal tapers, which may affect the way in which the assembly behaves.
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Footbridge · 2014-06-22

Purely for interest, here is how 34007 Wadebridge is currently arranged.

jma1009 · 2014-06-22

thanks Footbridge for the above very interesting photo.

perhaps photos can be deceptive but it doesnt look to me like the piston rod to crosshead cotter is a particularly good fit in the outside of the crosshead!

cheers,
julian

Lplus · 2014-06-23

作者 jma1009: ↑

thanks Footbridge for the above very interesting photo.

perhaps photos can be deceptive but it doesnt look to me like the piston rod to crosshead cotter is a particularly good fit in the outside of the crosshead!

cheers,
julian
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The cotter is used to pull the rod into the crosshead taper. So it neads to bear on the crosshead slot at the left hand end as you look at it in the picture, and on the rod slot at the righthand end. The rod slot is hidden in the crosshead. Also a bit of play is reasonable either side, to ensure it moves easily in the crosshead. As long as it is tight and the feather is in tight at the other side, it should be ok.

Steamie Boxes · 2021-10-04

Don't know if there is a more modern thread for the loco, but hearing reports that the loco has been running up and down Steamtown recently and is almost ready for test runs.

Bulleid Pacific · 2021-10-05

It's been a long while, but will be nice to see it again.

Davo · 2021-10-05

作者 Steamie Boxes: ↑

Don't know if there is a more modern thread for the loco, but hearing reports that the loco has been running up and down Steamtown recently and is almost ready for test runs.
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Is there any pics or videos or someone seen her in steam in 10A,s yard a steward told me on a pendle dalesman tour 34067 Tangmere wouldent be ready from overhaul for at least a year to 2 years maximum wether or not he was right I wouldent be sure.

RalphW · 2021-10-05

作者 Davo: ↑

Is there any pics or videos or someone seen her in steam in 10A,s yard a steward told me on a pendle dalesman tour 34067 Tangmere wouldent be ready from overhaul for at least a year to 2 years maximum wether or not he was right I wouldent be sure.
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If she's been seen moving about the yard then I think that we can be fairly confident that the overhaul is as good as finished. But who knows?

Romsey · 2021-10-05

Of course it could be Bodmin with temporary air smoothed casing added.

(Dives for cover grabbing tin hat on the way...)

Cheers, Neil

Dan Hill · 2021-10-05

作者 Romsey: ↑

Of course it could be Bodmin with temporary air smoothed casing added.

(Dives for cover grabbing tin hat on the way...)

Cheers, Neil
Click to expand...

Or comes maybe she comes out with 249 Squadron nameplates. Carnforth does have form for a little bit of mischief.

Sidmouth · 2021-10-05

Last image I saw certainly indicated not a huge amount of progress with the engine largely complete . However they do have 34073's boiler as well which could have been on the receiving end of Carnforth ministrations to be dropped into the frames . Do I remember correctly the boilers are not interchangeable between rebuilt and unrebuilt or am in mistaken ?

andalfi1 · 2021-10-05

作者 Sidmouth: ↑

Last image I saw certainly indicated not a huge amount of progress with the engine largely complete . However they do have 34073's boiler as well which could have been on the receiving end of Carnforth ministrations to be dropped into the frames . Do I remember correctly the boilers are not interchangeable between rebuilt and unrebuilt or am in mistaken ?
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As far as I know, the boilers are, but not the smokebox obviously.

GWR4707 · 2021-10-06

Rumours abound on the local groups round here that this mornings test run is Tangers...

Sent from my SM-A125F using Tapatalk

5944 · 2021-10-06

https://www.realtimetrains.co.uk/service/gb-nr:C29859/2021-10-06/detailed

GWR4707 · 2021-10-06

作者 GWR4707: ↑

Rumours abound on the local groups round here that this mornings test run is Tangers...
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Should possibly temper this with

a) a Diesel did a light test run yesterday so perhaps today is the day for a loaded one;
b) I note that schedule is for an ECS rather than light run and don't WCR usually do a light one when fresh out of the box and folow up with a loaded one if the 1st goes OK?

oh and I would be amazed if Tangmere has Tangmere plates fitted the first time she emerges......

Davo · 2021-10-06

Well 34067 light test run times is flagging up on rail advent mainline steam tours loco moves and test runs 2021 calendar and not cancelled either let's see if the path to Hellifield is activated on R.T.T. it's due off Carnforth at 09:58am

46223 · 2021-10-06

作者 Davo: ↑

let's see if the path to Hellifield is activated on R.T.T.
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Activated 06/10/2021 07:35

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