BR Standard class 6 No. 72010 'Hengist' and Clan Discussion Thread

Before I answer some of your questions, CTL Seal have just started the erecting of the frame extensions. Go here for details

https://www.theclanproject.org/Clan_News.php

Bikermike - "I wonder if any of this was done on the production line back in the day?" Yes it was. We managed to get a copy of the original erection instructions and the smokebox saddle, cylinders, motion brackets and slidebar brackets are all fitted to the frames by grinding. We also took the opportunity to smooth the exhaust steam ports on the frames to match the exhaust manifold.

northernsteam - "I would suspect that once the cylinders are in place there is little further improvement can be made to these 2 joints". We had a visit from the Collier brothers on Monday which, as always, is a very interesting experience. We were told that a vertical bar was welded to the frames immediately in front of and behind the cylinders. This can be seen on a close inspection of a photo from 71000.

northernsteam - "Why do you need to radius the corners on the frame/extension plates, especially to such a small amount as 1/16th to 1/8th inch?" I'm told that sharp edges are stress raisers. This note is on the bogie frame drawing as well and many others.

Sheff - "There’s a photo?" - go to https://www.theclanproject.org/Clan_News.php

jnc - Most of the web pages are dynamically served from the database so the content changes over time. You should find it in the Build Diary Archive - Construction -> Build Diary. Most items shown on the News page are Build Diary items so they go there. Only non specific items end up in the News Archive (might be best just to have one archive when I get time!)

Thanks for your interest

 

Thanks for the update Ian, some very interesting work going on with the Clan at the minute.

As a matter of interest, did you paint the mating surfaces of the saddle and frame before assembly? The photos seem to indicate not. Is there any danger of the uncoated surfaces causing problems down the line? I believe the A1 team were assembling some parts with wet paint on both faces.

 

Hello Keith

"did you paint the mating surfaces of the saddle and frame before assembly" We were strongly advised that we needed metal to metal contact on all frame mating faces so none of these faces have been painted.

 

Thank you for the responses - very informative

WRT to grinding - it was more the level of care and time - without disrespect to the men of the time, did they spend as much time fitting, testing, re-fitting compared to the Clan Project.

 

During 2968's current overhaul, we found severe wastage of the trailing frames and dragbox, which were subsequently replaced. The photo shows the wastage with a section above still at the frames' full thickness. This as where a stretcher was riveted to the plate - with no paint between.

 

Interesting, but are we drifting into rivets versus bolts in this matter ? -although in theory the joining of two parts with fitted bolts gives perhaps better alround performance than riveting there can be little doubt that hot riveting certainly does pull parts very hard against each other.

 

You are certainly pulling it back to that discussion, but I will not take the bait.

Excellent response from Ian, as usual, thank you.

 

Thanks Ian

 

I'm surprised at that. A common past practice when riveting plates together in the past was to coat them with red lead (N.B. not the same as red oxide) to minimise the risk of corrosion. If any water gets into the joint and the steel is unprotected it will eventually cause problems. What's to stop it happening with 72010?

 

No, Steve, the point of my photo was to show that the only parts of 2968's rear frames which had not wasted was the unpainted pieces where the stretchers were riveted to them, so there had obviously been no ingress of water into the riveted seam.

 

And my point is that what works for a riveted seam, does it work as well for a bolted one....

 

Well, Swindon, Gresley and Bulleid were happy with fitted bolts where required. Of course, hot riveting has its uses, especially in the shock absorbing area around the front of the frames and bufferbeam and the joints between frame stretchers for a bit of flexibility.

 

I'm not disputing that the frame where the stretcher was is still full thickness. The area under the cab is going to suffer badly from corrosion; it always does due to coal dust and the use of the slacker pipe and the double plate does afford protection in that aggressive environment The worry is that the area between the riveted plates will start to corrode, causing the inevitable bulging that happens when active corrosion starts. Putting red lead on (as used to be done) acts like a jointing compound, keeping moisture out.
At the end of the day, it's a matter of choice and there will be arguments for and against, just like the argument for and against bolting versus riveting. Personally, I'd put some protection on the mating faces.

 

Yes, weaving our way through the different arguments is a challenge!

We've added a section in the Build area of the web site to explain the process of creating core boxes in the cylinder pattern. Tony has completed the last of the 26 sections for the main cylinder and will start thinking about the more taxing challenge of creating the valve cylinder core box.

https://www.theclanproject.org/buil...ic=COR&description=Casting - Cores and Prints

 

Certainly takes some mental agility to think inside-out in 3 dimensions!

 

One would be inclined to agree.

The best possible opportunity to mitigate or prevent corrosion exists whilst the surfaces are newly machined.

When presented with the choice of bare steel or a compound to prevent water ingress or condensation forming, I would opt firmly for a surface coating of some nature. Even a high performance greese would be better than nothing.

Is it not the case that modern mild steels have a tendency to corrode faster than the old timey mild steel? I dont recall the reason, but im sure I read that somewhere.

 

Anodes anyone ?

 

Bolting some zinc to the frame plates? Would that work? Doesn't it require a suitable medium for the flow of electrons?

 

Not sure sacrificial anodes would apply here; those are for situations where there are i) elementarily different metals (e.g. the copper and tin in bronze), and ii) a conducting (ionic) fluid (e.g. salt water). The corrosion chemical mechanism there isn't oxidisation (i.e. addition of oxygen to form oxide compounds, as it would be with two iron parts rusting), but the replacement of one metal with the other, which 'dissolves' off one side (better explanation here).

Noel

 

Of course Noel , the 'damp' that's around in a Steam loco is probably slightly acidic but not very ionic... And of course Geoff T. would know all about that and suggested it already if it had legs...