By David Pinniger

“Hazel” seen recently on the Ambledown Valley Railway

This is one of the most successful locomotives designed and built by Stewart Browne of Archangel Models. It is based on a Bagnall 2-4-0T built in 1896 originally for the Plynlymon and Hafan Tramway who then sold it to the Vale of Rheidol Railway in 1902.There are many variations on the Archangel theme, including different cabs and spectacle plates, saddle tanks and tenders, All the earlier ones had a small 3/8ths cylinder and are fiendish to run and will keep you fit enough for the 100 metres hurdles [maybe another article one day?]. But this story will concentrate on the two Rheidol’s which ran on Dave Rowlands’ Alderbrook Valley Railway and which were owned by Dave and myself.

Double headed! “Hazel” and “Thomas the Rhymer” on the Alderbrook Valley Railway in about 1980

Dave bought the first “Rheidol” from Cock Lane in 1976 which became AVR number 3 and he soon renamed it “Hazel” after one of his dogs. I was very impressed with the engine as previously we had only run simple meths-fired pot boilers. Like the two Archangel pot boilers, “Brick” and “Princess”, the “Rheidol” had one large 9/16” diameter cylinder between the frames. The two outside cylinders are dummies.

Unlike externally fired pot boilers, “Rheidol” is internally fired with a Smithies boiler heated by two wicks in the firespace under the rear of the boiler. Heat from the wicks is drawn through the outer layer of the boiler to heat the water tube within. To work, this system needs a forced draught. When the engine is running this is provided by the exhaust from the cylinder which goes through a blast pipe in the smokebox which sends a jet of steam up the chimney to draw the heat through the boiler. When the engine is stationary, a steam blower is used which takes steam from the boiler through a valve in the cab and then to a separate jet pipe in the smokebox.

“Hazel” passing Hinton Magnolia on the Ambledown Valley

With these engines you have to learn to open the blower valve as the engine stops and close it again when you open the regulator to start the engine. On a heavy train the engine should make plenty of steam but when running light engine it is sometimes necessary to have the steam blower cracked to get enough draught.  When raising steam from cold you have to use a battery powered steam blower to suck the hot air through the boiler. When there is about 20psi on the pressure gauge, you can open the steam blower valve and remove the battery blower.

“Hazel” visiting Roy Bernard’s Cookham Light Railway

Once you have learnt the tricks, the performance is amazing. The more you hang on the back, the more steam it makes! You have to remember to pump water from the side tank into the boiler at intervals to avoid the boiler running dry. There is no luxury of a water gauge glass! However, you quickly get to know when water is needed as the safety valve blows raspberries every few seconds. If it suddenly goes quiet and the pressure gauge drops to zero, you have run out of water! Water spitting out of the chimney means that you have overfilled the boiler and it will prime. Getting to know the balance is one of the pleasures of operating an internally fired loco like this.

“Thomas the Rhymer” at Bishops Amble

The slow running and power of haulage from one cylinder is amazing. One of the weaker points is the meths feed system. There is a large tank at the rear which feeds a sump through a chick feed, the flow to this is regulated by an 8BA screw in the pipe and not a needle valve. It means that it never really shuts off the meths supply when you close it at the end of the run. If the sump ignites it can lead to a loud bang which rather surprised Dave Rowlands one day. It could have been a lot worse, but led to a trip to Cock Lane for a repair to the blown meths tank seams.

The rear of “Thomas the Rhymer” showing the new cab and modified meths tank

I was lucky enough to buy a second hand 1976 “Rheidol” which was only a year old for a very reasonable price. This was renamed AVR number 6 “Thomas the Rhymer” and also became a stalwart on Dave’s  Alderbrook Valley Railway and later on my own Ambledown Valley Railway. The fact that the meths tank was higher than the side tanks always annoyed me, so I rebuilt “Thomas the Rhymer” with a lower tank and a full cab. The engine was sold to John Chambers in 1998 to fund the purchase of another more sophisticated locomotive, an action I have since regretted.

“Thomas the Rhymer” at speed on the AVR

However, the Ambledown Valley now has a “Rheidol” back on the roster, as Dave Rowlands has given me custody of “Hazel”.  She had been on the shelf in a display case and not run for some years but a set of new wicks and a rod up through the meths feed pipe had a her back like new and running well on our AVR Archangel day in July 2012. Engines have got a lot more detailed and sophisticated since the 1970’s and you do need to regularly top up the boiler and not let the water get too low. However, I still get a buzz from running an engine which is now 36 years old!

David Pinniger