GCR 8K/LNER 04 63601

This locomotive, owned by the NRM, is undergoing its second major overhaul at Loughborough. The boiler has been removed and sits outside the shed.
The chassis has been stripped. The crank axle had been badly worn on the eccentric sheaves and a new axle is being made. Here is a picture of the chassis in Lbro shed yesterday.

 

I have found a couple of pictures showing the locomotive after its first return to Steam at L' bro.....and a youthful Craig Stinchcombe!

 

The boiler has been moved from the low flat wagon and is on it's side, being worked on, outside Lbro shed. The driving wheels were being cleaned and the frames have been painted.

 

The front tubeplate of the inner firebox has been removed from the boiler. However it appeared to be riveted to the rest of the inner firebox. Obviously such rivets can be drilled out to remove them, but how can they be put back if the inner firebox is still in place?

 

Deleted.

 

Patch screws. These are inserted from the fire side into threaded holes, then the square end cut off and the head peened over.

 

Thanks for the explanation - I hadn't realised that there would be sufficient strength for a screwed fixing to be used with just the thread in the inner firebox side sheet.

 

I'm not a boiler smith so don't know, but shear head bolts are used in the motor industry as you say. But those heads look a little too substantial to me to be sheared off like that without stripping threads in the copper plate.

 

Looking closely at the photos, there is a machined groove where the square joins the head which, could be a tell tale of a torque limiting measure as a shear groove.

 

Yep - agree!

 

Patch screws in a lap joint is a routine repair.

The steel rivets are gas cut out in alternate holes. It's dead easy because you can't easily damage the copper plate. This keeps the plates tight together, you wouldn't punch them out.
You then tap a thread 11 tpi Whit form at what ever diameter gives you a full form thread. The adjacent numbers in the pic are almost certainly the size of the hole.
Next countersink the hole. From memory its 60 deg for a copper screw and 80 deg for a steel one, but I might have miss remembered that detail. There has to be a couple of threads in the water side too.
Drive the screw in using the square. I put a few stokes of a saw cut on the undercut. Tighten it until the square wrings off. I think I might have used some Stag on the threads, it smells of pine smoke.
Then caulk the screw head into the plate. Use a clockwise motion on the tool to tighten the screw as you do it. Try not to undercut or groove the plate.
Rinse and repeat. Easy peasy.
I've done loads. Not any more thankfully.

Edit: Spelling, added more info.

 

It's 80 deg for copper and 60 deg for steel, but it is relative to the plate material and not the patch screw. You tap both plates if they are copper but only the underside plate if they are steel. More info in the HRA guidance note for those interested:
https://static1.squarespace.com/sta...1511180393068/HGR-B9025-Is01-Patch+Screws.pdf
The GWR developed means of riveting seams with the firebox in situ using long tongs and wedges and this was copied by the LMS when Stanier went to them. I believe this is practiced on the Severn Valley but, although I've been shown the necessary tools, I've never seen it done. It is described in the HRA guidance note on riveting:
https://static1.squarespace.com/sta...29/HGR-B9023-Is01-Steel+Rivets+&+Riveting.pdf

 

The photos are of 2968's firebox under repair on the Severn Valley, 26 July 2020.

 

Yes, you are right.
I knew I'd forgotten some details.
It's been the best part of 10 years since I did a lot of boiler work, I'm glad to say.

 

Is the NRM funding the work at all?

Dave

 

Re the NRM, I've heard of no details, but I'm sure there will be a contract between the GCR and NRM which probably involves NRM financing some materials, GCR funding work time and running on GCR for a certain no of months/years....but it is no doubt "commercially sensitive"!

 

Here is a closer picture of the front of the firebox inside.

 

According to the latest "Main Line" magazine (#190) the foundation ring is life expired and will be replaced by a new one (casting or fabrication?)

 

Some work is being done on the frames and it looks like the axleboxes are being re-white metalled. There is no sign of the fourth pair of driving wheels and axle ( A new axle has had to be manufactured and machined for the slide valve eccentrics.).