Sentinel 8805

In February 2011, I attended the Sentinel Drivers' Club AGM in Basingstoke. In conversation after the formalities, I met Norman Smedley who proclaimed that, in the boot of his car, he had a 7.25 inch gauge model of the unique LMS Sentinel-Doble shunter numbered 7192.

Not the normal car boot contents I thought (with raised eyebrows) and, at Norman's invitation, went to have a look.

Although 7109 is a 12 inch to the foot scale, I've long admired the amazing amount of time and effort that goes into model locos. This was another moment of admiration.

Car boot contents (1)

Car boot contents (2)

Amazing detail (and not just the boot catch!)

Right hand side

Norman sent me this photo recently of the model nearing completion and what a fantastic model it is! I'm very much looking forward to seeing it in action.

Nearing completion (June 2011)

The 'prototype' for Norman's model was the only true Doble loco built by Sentinel, works number 8805, and delivered to the LMS in 1933. It was driven by two 150 HP Doble engines, one for each axle, and had an oil-fired 1500psi boiler and condenser! Whilst it performed well, it was too complex to maintain and was withdrawn in 1943. (Norman's model will be battery powered!).

Sentinel 8805 (Photo Tony Thomas)

And again (Photo Tony Thomas)

As 7192 numerically follows Radstock's 7190 and 7191, this is the reason why 7109 will not carry the number 47192. See also 7109 Restoration.

Sentinel 7109's Superheater passes 550psi Hydraulic test

After repairs, a boiler has to pass an initial hydraulic test (water) at 1.5 times working pressure to ensure that it is physically sound. The superheater, because it works at a higher temperature to produce dry steam, has to pass its initial hydraulic test at 2 times working pressure. For a Sentinel, this means 550 psi (~38 bar).

I'd thought that the hydraulic test would require some pretty sophisticated equipment; however, this is not the case.

First the far end of the tubes need to be blocked. The sealed ends can be slackened to let air out so that there is only incompressible water contained.

Blocked superheater tube-ends

Then an artistic arrangement of pipework is attached at the near end (the bicycle wheel is not essential).

Artistic pipework

The hydraulic pump is then connected to the artistic pipework and pressure applied.

Check the gauge reading...

...this one's easier to read.

About 565 psi (39 bar)

So how is the pressure applied, I hear you ask? (Note the video was shot by the owner). Starring Justin & Pete.

(Any suggestions for the owner to do the hard work are met fiercely by the camera lens!). Clearer video on YouTube.

The pressure has to be held for at least 30 minutes. If satisfactory, then the test is deemed passed and a certificate written on the spot and issued.

Al fresco computing

Many thanks to Justin Goold of J R Goold Vintage Steam Restorations Ltd and Peter Hawkins of Hawkins Inspection Services Ltd for their services.

Sentinel 7232 Ann

As background to the restoration of Sentinel 7109, I've visited some other Sentinel locos and, in some cases, done a pretty thorough photo-reconnaissance  of internal bits and pieces.  My visit to the picturesque Embsay and Bolton Abbey Railway near Skipton, West Yorkshire, in June 2011 was not one of the thorough photo sessions but interesting all the same. Ian Douglas kindly showed me around.

Sentinel 7232 Ann (1)

Sentinel 7232 Ann (2)

Built in 1927, Ann is a single-engined balanced Sentinel steamer rated at 80hp. It spent its working life at British Tar Products Ltd, Irlam, Manchester UK. Now at Embsay, it has not run since 2007 due to safety valve problems and the boiler being out of ticket.  Its operating future is uncertain (June 2011).

More details are available from the Embsay and Bolton Abbey Railway website.

Sentinel 7109's Blowdown Valve

The blowdown valve is used for clearing out (blowing down) accumulated scale, rust and assorted particles from the bottom of the boiler. 7109 was missing this item on arrival and it has taken a long time to find one capable of handling the high 275psi boiler pressure. John Goold has obtained a new old-stock type as in the picture with 4.25 inch diameter undrilled flanges.

New Old-stock Blowdown Valve

It has to be fitted on to a flanged "drain-pipe" at the bottom of the boiler (it has been cleaned up and the snow has melted since this December 2010 picture was taken).

Blowdown valve "drain-pipe" flange

And then there is the spanner needed to operate the valve from a suitable distance. And the angle of attack to avoid the spanner operator from being steam-cleaned!

Sentinel 7109's Polished set of gauge glass valves

All loco or waggon boilers use a gauge glass to enable the fireman to see the boiler's water level. A glass tube between an upper and lower gauge glass valve is where the actual water level can be seen. The upper and lower valves are used to ensure that the level is indicating correctly and that any doubtful muck can be jettisoned when required.

Luckily, 7109 came complete with gauge glass valves attached to the boiler although they were in an unknown condition at the time and looking fairly dull.

Gauge Glass Valves as arrived (with curved handles)

Gauge glass valves to fit Sentinel boilers are unusual in that they have to have a curved surface to match the cylindrical curvature of the boiler profile.

Gauge Glass Valves after a little cleaning
(and much improved in bright light!)

 The internal moving parts of the valves, despite my initial (naive) attempts, were not in a good state. The curved handles indicated an old design that was famed for leaking badly. 

"Klinger" Valves spindles (Photo Heritage Steam Supplies)

John Goold advised the rebuilding of the valves to the "Klinger" design and this has been completed. 

Good as new and not so dull!

The almost as-new look has been achieved by 'pickling'.  I never quite understood whether this was to do with an extended visit to the pub or a dip in an acid bath but the end result looks brilliant!

Sentinel 7109's Boiler ready for cladding

Final preparation of the boiler has been completed at Mendip Steam Restorations so that the cladding can be added to hold in the ceramic insulating material.

'Lip' Highlighted

Around the lower edge of the wide upper section is a 'lip' which both supports the lagging and enables the cladding sheets to be attached with pop-rivets. This is how it was done previously however many of the remains of the rivets were still blocking the holes. These needed to be drilled out in preparation to fit the new rivets and cladding.

Drilling for drainage

Water had been prone to collecting in the 'lip' and promoting rust and required some holes to be drilled in the lip to improve drainage.

I enjoy visiting Mendip Steam Restorations as there is always something interesting happening and a friendly welcome (possibly influenced by the packet of chocolate digestives I took along!). Currently, three traction engine boilers are being worked on as shown. I hope to do an extensive article on MSR in the future.

MSR (1)

MSR (2)

MSR (3)

Until work began on Sentinel 7109, I'd been completely unaware that this type of industry still existed in the UK; however, I really am pleased to find that it does and what a wonderful and skilful bunch of guys these people are!

A special welcome...

... to arrivals from VegPlotting.

(NSW, Non-Steam Wife) has clearly been generating a lot of traffic to Sentinel 7109. So here's a little posting especially for you!

2011 Greenhouse at Midsomer Norton Station

Sentinel 7109 lives at Midsomer Norton Station, near Radstock, Somerset, UK (BA3 2EY). This particular station was always characterised by its greenhouse which was situated next to the signal box. Station staff used it to cultivate all sorts of produce (which, in those more gentle 1950's days, there was time to do between trains).

1959 (Photo: Eric Rimmer (SDRT Collection)
from Alan Hammond's Heart of the Somerset & Dorset Railway)

The line was closed in 1966 and most of the station including the greenhouse was dismantled. In September 2003, the scene looked as in the picture below.

September 2003 wasteland

In 2005, work began to bring the signal box and greenhouse back to life.

October 2005

June 2006

January 2007 (with Graeme Mayes perched on the roof)

May 2007 (My name is on one of the roof-tiles as are many others
who sponsored the tiles at a pound a time)

June 2008 externally complete but no greenhouse

Magically stepping forward to 2011, the greenhouse is complete to accompany the signal box. Produce is being grown again and sold to raise funds for the project as a whole. So Garden Bloggers and all, do come and visit us at Midsomer Norton Station any Sunday and enjoy all the sights and sounds (and cake) that are on offer.

May 2011 Greenhouse and Signal box complete in all their glory

Sentinel 7109's Mechanical Lubricator

Sentinel 7109 uses a four-barrelled Delvac mechanical lubricator made by the "Vacuum Oil Company Ltd".

Delvac Mechanical Lubricator before cleaning

It is driven from a crank on the front engine drive shaft. A camshaft in the lubricator housing is then rotated slowly by the rocking action on a ratchet arm; via rockers, the cams gently push on each of the four barrel pumps on each rotation of the camshaft.

There's a camshaft and four rockers somewhere in the sludge...

...right there in fact!

Rocker springs and cam-followers...

...and the pump barrels

Three of the four pumps have a wire in them which sits in the pump nozzle. I can't see what it is for; a flow restrictor maybe but the wire is too flimsy to make any difference. I'd be glad to hear from anyone who knows better!

Wire lodged in the pump outlet...

...and extending down in to the pump nozzle

The mechanical lubricator has been cleaned, repaired and filled; cylinder oil now exudes from all the right orifices.

Delvac Mechanical Lubricator after cleaning

Sentinel 7109's Superheater - Good News

A preliminary hydraulic test has been done on the boiler's four-tube superheater and no problems have been found.

Four-tube superheater awaiting attention

Justin Goold commented after the test that the superheater seemed to be new-old stock and that it did not appear to have ever been used. This is, of course, really good news as there far less chance of an early failure (I hope I'm not tempting providence here!).

Superheaters have to be certified as passing an even more demanding test than the boiler itself. The boiler requires a 1.5 times working pressure test (412.5 psi) whereas the superheater needs to withstand 2 times working pressure (550 psi). These figures reflect the fact that Sentinels had about the highest working pressure of any steam loco on British Railways.

There is yet the boiler inspector's formal test by Peter Hawkins for certification before the superheater can be installed in the boiler (and one or two (hundred) other things in the meantime!). It's all progress!

Sentinel 7109's regulator and operating valve assembly

When Sentinel 7109 arrived at Midsomer Norton Station in December 2004, it was in a pretty rough and partly disassembled condition. The regulator assembly was covered in rust from a few decades of atmospheric exposure.

Regulator Assembly on arrival(1)

Regulator Assembly on arrival(2)

The regulator valve internals were unserviceable.

Original inside surface of regulator valve...

...with valve segment in place

The stop valve was unlikely to stop anything!

Stop valve pitted with rust...

...deeply pitted that is!

But in the right hands, things come back to life.

The refurbished regulator valve...

...and a stop valve which will stop something...

...and all the rest of the bits and pieces!

The whole regulator and operating valve assembly has been completely refurbished superbly by John Goold of J R Goold Vintage Steam Restorations Ltd in Camerton.

Refurbished valves