Sunday, 15 May 2016

We're Domed.....!

A mixture of good progress during the past week. Now that the loco is back on its wheels we can start refitting various parts and Roddie McCrae has been busy putting the loco brake hangers and railguards back in place. Likewise with the tender off of its wheels we were able to get the wheels and axles shot blasted to remove the years of accumulated paint and grime. This revealed some very interesting stamping on the tyres and wheel centres. As everyone knows, CR828 was delivered new from St Rollox works in August 1899 and as we might expect she has received various new parts during her long life. But it may be that she has been using a tender wheelset that's older than she is (see picture below). 

As you may recall we were unable to pressurise the boiler for hydraulic test purposes because of leakage at the regulator valve. Accessing the regulator meant that we had to remove the dome cover (28 large nuts to hammer off). Inspection of the valve showed that it was not seating tightly on its lower seat. The Caley were fond of using the Ramsbottom double beat regulator - as mentioned elsewhere it gives an easy and progressive opening with a relatively short travel. It relies on two valve ports, both of which operate simultaneously and both of which have to give a tight shut-off. What we found was that the upper valve was seating perfectly but the lower one had a significant sector where the valve plug was not contacting the valve seat. This was corrected by lapping with grinding paste (you have to lap both valves at the same time to ensure they remain fully aligned). Fortunately this is a relatively straightforward operation. You can sit on top of the boiler with your feet inside the dome mounting ring and use the weight of the valve to do most of the work for you. After getting a true seating for both valves the dome cover was refitted and the 28 nuts hammered tight in preparation for another hydraulic test attempt during week commencing 16th May.

Alan French, ably assisted by John Greig, completed the white metalling of the eccentric straps on May 14th. It was fascinating to watch Alan and John tackling this job - it requires real craftsmanship. We are now in a position to take the eccentrics and the straps across to the RPSI workshops at Whitehead for machining and fitting. When complete, I am sure that the loco will benefit greatly from having straps that truly fit the eccentrics for the first time in many years. It will be very interesting to set the valves again.

One slight setback occurred during the week when Ian Riley informed us that the tender tyre forgings have not yet left South Africa. This is a result of an export licence issue. Hopefully this will be resolved quickly and the tyres will arrive in the UK in around 3 - 4 weeks...

Concentrating hard, Alan French runs white metal into one of the eccentric straps..

A batch of eccentric strap halves (there are eight in total) lies cooling down after white metalling

John Greig and Alan French working together on the eccentric strap white-metalling production line..

Roddie McCrae fitting a brake hanger

And again, here's Roddie getting ready for another brake hanger

Removal of the dome exposes the Ramsbottom double beat regulator valve..

The regulator valve surrounded by the small steam take-off pipes for the injectors, the brake system and the blower. The large pipe is the main steam pipe that carries steam to the cylinders.

Despite appearances the boiler is in great condition. The operating rod for the regulator valve is connected to the regulator handle in the cab via an eccentric cam that raises and lowers the rod as the handle is moved towards open or closed.

The regulator valve stripped into its component parts. The operating rod is lying drunkenly against the steam pipes after its connecting pin has been removed. The valve plug has been removed and is sitting upside down on top of the boiler cladding. The upper and lower seats can be seen. 

After lapping in the valves with grinding paste this is what the valve seats look like. The continuous bright grey  lines indicate that the valve will sit tightly shut against the forthcoming hydraulic pressure (we hope...!)

Refilling the boiler before putting the dome back on....

The inside of the dome...a mixture of recent and old riveting..

The dome after having the copper sealing ring refitted (fully annealed)

The old girl with her dome refitted...

The tender wheelsets back from blasting and priming

No wonder we are renewing the tyres - this one has been in service since 1952...

Look at spoke has the word "Firth" stamped into it and the spoke above suggests that the date of manufacture was 10th June 1891......!!

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