New Build Night Owl - 4709 Begins

Despite the 4709 project making progress, this thread has been dormant for nearly seven years, all the discussion being in the general New Builds thread. I am refreshing this thread as perhaps the better place to ask a specific question.

Clearing a pile of papers, I have across an appeal leaflet of uncertain date, but presumably from several years ago as it includes a picture of the frames with the "cylinder block trial-fitted". That must have been the block (more accurately a pair) from one of the donor locos, now superseded by newly cast cylinders. Can someone please remind me (and anyone else interested) when and why the decision was taken to have new cylinders.

I have consulted the blog section of the website https://www.4709.org.uk/4709blog but there are two problems with that. Installments are identified only by day and month, so the years aren't obvious, and they seem to go back only to a time after the decision had been taken.

 

Gauging issues, IIRC. (The details are buried in one of the plethora of older Night Owl sites, the contents of which the people who put up the new sites were not careful to transplant. [My opinion of that, were I to type it in, would be extraordinarily un-civil, so I have to restrain myself. But what do you call people who destroy history?] Alas, I deleted the bookmarks for them, or I could trawl around in the Internet Archive and try and find them.)

Noel

 

They were still using the cylinders from 2861 until late 2014 at least (archives seem to suggest that with the saddle being amended it was gauge friendly so no idea what changed), what is also unclear is what happened to the cylinders which had been subject to (at the very least) cleaning and painting at Llangollen, it was noted that the No.1 boiler at least went to Didcot and was used as a time for a template for 2999 plumbing but no idea what the plans are for any of the remaining bits.

Looking through the blog it suggests a tender has already been set aside for her, can anyone shed any light on the identification of said tender and its background?

 

Not disputing the gauging issues, but new cylinders were required to accommodate the correct size smokebox.

 

It's speculation of mine, but one of the candidates for 4709's tender is this one on Didcot No.6 road which I photographed in 2019. Couldn't tell as to it's number and where it came from. Just my speculation however, hopefully someone can clarify/correct the backstory of this tender.

 

Ah, that rings a bell; now I'm trying to remember the details. Was it something to do with switching from a recycled No 1 boiler to a new-build No 7? I think we discussed this before; yes, here it is. But the 4709 blog says it was "to bring the width and height within the current Network Rail Loading Gauge". Maybe a bit of both, then?

Noel

 

Indeed , be interested in whether the revised cylinder blocks are smaller internally as well as externally, though a slight fall in TE would be of little handicap - still be one of the more capable in the ' second 11'.

 

I thought that the GWS stated, some time ago, that it no longer had plans for running on the national network.
Ray.

 

Thanks for the reminder of the reason for the new cylinders.

One of the problems with a project that extends over many years is that the plans change, always for good reasons at the time. It is certainly to be hoped that 4709 will run on the main line; otherwise all the additional work and expense of the new cylinders will have been wasted, likewise the work and expense of building a No.7 boiler, as a disguised No.1 would be perfectly adequate for use at Didcot or on heritage lines. In fact it seems hardly likely that a No.7 boiler will be built unless going main line remains the intention.

 

Which now makes me wonder what the requirements for getting rolling stock in and out of Didcot are. The Gas Turbine is essentially stuck there permanently but that could be a lack of ability to take it anywhere rather than across the yards.

 

The Collet 4000g tender at Didcot is No 2885 that accompanied Hall class no 5967 Bickmarsh Hall to Woodhams in Barry.

There is an image here at Llangollen of the frames of 4709 with saddle block from 2861 :

https://www.flickr.com/photos/113816008@N03/41049749365/in/album-72157666659316667/

 

GWS have said that they no longer intend to operate their locos on the mainline*. That doesn't mean they won't be passed for being hauled over mainline tracks to and from the loading point.

* Too expensive and they don't have enough staff to support that.

 

Info from Richard Croucher in March this year was that they are building 4709 to be able to run on the main line, hence the new cylinders etc. They envisage placing the loco "with an organisation which manages main line locomotives" rather the GWS handling all the work.

I apologise for failing to check that info before I revived this thread.

 

More specific was the smoke box saddle, which with a number 1 boiler would have needed an additional connection.

 

Actually the saddle/cylinder castings were from 2861 as was the No1 boiler so they would,in fact, match. However the saddle would be too tall for a No7 boiler and so it was originally planned to inset it into the smokebox of the larger diameter boiler. In the end it was, IIRC, simpler just to opt for new cylinder/saddle castings to suit a No7 but slimmed down and lowered to suit NR's current loading gauge.
Ray.

 

https://www.4709.org.uk/4709blog/cylinder-update-august-2021

Interesting how Churchward's decision to make cylinder castings identical and symmetrical fore and aft is saving on machining setup costs. That must have been the case 100 plus years ago as well. I believe that the cost of machining operations was a significant chunk of the build cost for a new locomotive back then, but this sort of advantage is something that's never occurred to me.

 

Thanks for posting. I am not entirely sure I understand what they are saying in the blog but your point about the cylinders being symmetrical may be the key i.e. in the boring operation the first cylinder is attached to a rigid support (say a rectangular box section) on the boring machine table using the machined rear and horizontal faces, and being symmetrical the other cylinder can be put in the same way round (so one is bored from the front and one from the back). Arranging the machining sequentially of what is effectively a batch, albeit a very small batch, seems to be stating the obvious e.g. don't do one, then do something else on the borer, then get another operative to machine the other cylinder some months later, as apart from the duplication in set-up time, having the same person doing both at the same time has advantages.

 

I believe the frames for this are now at Tyseley "for the removal of its extension frames and the assembly of its front end" according to Rail Advent.

 

AIUI the way the Churchward front ends were assembled in the factory was to build up and align the cylinder block/extension frame assembly as a unit, then fit the assembly to the main frames and get the optics out. Back in the day I understand Swindon works used to have pre-assembled front ends for the major classes, so if a locomotive was scheduled for new cylinders the old extension frames were removed and the new assembly bolted on, which must have saved a lot of time.

 

Yep, was on the 4709 website last week with a piccy.

https://www.4709.org.uk/4709blog/tuqel18efsap6c1cz1lmmd1kpotkbj

Also broadly confirms the construction process as noted by @Jimc above.