Steam Department

The number of volunteers at the Steam shop was lower this weekend as it usually is during Thomas weekends.  However some key tasks were completed.

On 1630:

·         The last of the troublesome smoke box bolts was removed.  With the bolts out, I was able to clean up all the holes and test fit new "T" bolts into all of them bar one.  The new bolts are now being ordered for 10 of the 11 holes.  The 11th requires more work.  The smoke box has clearly been reinforced since this one was fitted so a rivet is now positioned that prevents setting the bolt into the ring from the rear.  Tom will need to make a special stud that we can fit from the front and secure by welding a nut on the back.  However, this repair is now largely complete and ready for when we refit the smoke box front sheet.

All the problem bolts are out !!

·         All the flexible stay caps, that were marked as requiring removal, were successfully freed.  This requires heating the socket of the stay with a torch before unscrewing the cap.  Applying brute force to the socket wrench without using heat to loosen the thread is absolutely not recommended!.  Cracking or otherwise damaging the socket would mean that the whole stay must be removed by drilling it out of the inner firebox then rethreading and fitting a complete new stay - several days of work - so it is a big relief that all are now off with no damaged sockets.  One damaged cap was successfully removed and will be replaced with our last spare cap.  A few more will be ordered to ensure that we have some spares in hand.  The caps must be removed and the stays hammer tested where the stay does not have a full length tell tale hole.

All the caps to be removed are paint marked

Once the cap is removed you normally find rust, scale and debris that must be cleaned out to allow later hammer testing.

There is normally debris in the socket

Once clean you can get a good idea of how the stay operates.  In the center is the ball head of the stay, a long steel rod the other end of which is threaded into the inner firebox sheet  The slot in the ball would have been used when the stay was installed to turn the rod and so screw it into the inner firebox sheet.  The ball sits in the socket, which is welded to the outer firebox sheet.  Screwing the rod into the inner sheet tightens the balled end of the rod against the socket. 

As with rigid stays, the objective of the flexible stays is to hold the inner and outer firebox sheets together against the full pressure of the water and steam that lies between the sheets when the boiler is in service.  The difference is that flexis are used where it is calculated that there should be (marginal !) movement between the two plates as they expand  This would strain and potentially crack a rigid rod.  The movement of the ball in the socket allows this movement.

Tightening the ball into the socket provides a significant, but not complete, seal against the boiler pressure so the cap provides the final seal.  This is why there is likely to be some debris in the socket when you first remove the cap.

The socket cleaned ready for testing

·         Mike continued with test fitting of the patch.

·         We also started on the exercise of measuring the holes in the tube sheet and matching these to the ferrules that must be fitted before the tubes can be inserted.

·         Most importantly, it now looks as if we should have good news on the welding by next weekend.

On 428:

·         Machining is now well under way on the thrust bearing surface of the first axle box.

First axle box mounted on the turret lathe

This clearly shows the remains of the old thrust bearing which consisted of mesh (actually old spark arrestor mesh from the smoke box was specified in the UP drawing), which was tack welded to the face of the casting and held in place the babbit which was poured into the recess, allowed to set and then machined smooth.

·         The overhaul of the pump mechanism for the planer was completed.  The next step is to clean and test the hydraulic drive mechanism.

The hydraulic pump now ready to refit

Nigel