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Quainton News Archive - Quainton News No. 19 - Spring 1974
Mobile Steam, The Story of 78147 - by WLA
Open days at Quainton are usually made occasions at which we are glad to see all sorts of transport oddities, apart from ice cream vans from West Wales! Traction engines, road rollers, vintage buses and cars, and fairground organs add to the fun, but I don't recall seeing a portable engine yet. So, if you would like to see one of these fascinating machines, drive down Burtons Lane, Chalfont St. Giles and, between the trees, you should be able to spy the tall chimney of a Portable. And if you are lucky she will be in steam and when the scream from the saw bench has died down you will hear the beautifully rhythmic and gentle beat that characterises a Marshall's single cylinder portable engine. It is a satisfying chug, chug, chug and occasionally, when the saw bites into a rather hard piece of wood you will hear the engine exhaust bark two or three times as the governor lets in more steam and she picks up speed again.
Annie is owned by a Quainton member, Ronnie Mitchell, who bought her from a carnation grower in Sussex in October 1969. There, she had been used for steam sterilising soil but her previous history is, unfortunately, unknown. Her Sussex owner had looked after her very well but when he laid her up he misunderstood the advice given by an old engineman to 'cover her in cylinder oil to preserve her'. What he did was to pour a gallon of oil into the boiler while it was still hot, then drain out the water and consequently he had left a nice film of oil over the scale on all the heating surfaces! This began to soak in and by the time Ronnie bought the engine the scale had absorbed it all!
Attempts at chemical cleaning failed and only one course remained - remove the tubes, crawl inside and chip, scrape and grind the scale away. This was accomplished with the aid of his young son, John, who at the age of 8 became an expert at tube drawing. When the boiler inspector next came he was most heartened to see the clean boiler and retubing went ahead without a hitch.
Regrettably Portable engines have never had much attraction for the preservationists; that honour falls to the Traction and Showman's engines, and very few have been preserved. Many tens of thousands of Portables were built by dozens of manufacturers and they were used for threshing (many had large fire boxes and could burn straw), and sawing, (most could run very efficiently on wood), and any job that could be done by a belt drive. The earliest ones were horse drawn and later on traction engines were used. They were very simple steam engines and 78147 is typical of the inexpensive easy-to-drive farm engine which was built by Marshalls and was very common at the turn of the century.
Annie was built in 1924 at Gainsborough in Lincs. Her single cylinder has a 10in bore and a 12in stroke giving a nominal horsepower of 10, governed by a Pickering governor. Cut-off can be adjusted by a slotted and engraved locknut assembly on the valve eccentric and reversing the engine can be achieved by the same means. One needs a spanner and five minutes notice to change direction or cut-off!!
The sawbench that Annie drives was found derelict and half buried in a nearby wood, where it had lain for 30 years. It was rusted solid and took a week to free. Some of the bearings had virtually been worn away, but remetalling was just possible and now it is as good as new. It was made by the London firm of Aublet Harry & Co probably in the 1920's, it measures 5 ft 6 in in length and takes a 3ft blade.
Firing with wood is a very different art from firing with coal, as I discovered the last time I helped with some sawing. We were using old doors, cupboards, shelves, a draining board and hard board, helped out with some very wet wood and bark off-cuts.
At 40 psi Ronnie began sawing up some branches of apple tree for the engine and asked me to raise the pressure gradually to 80psi as he had a large piece of wet elm he wanted to cut up to get it out of the way. The soggy off-cuts plus the few bits of apple got her to 60psi and there she stuck. So I levelled the fire a bit and put on pieces of door - very dry! The pressure began to climb. "70 pounds" I called out happily, plying the fire with more bits of door. I then went the rounds with the oil can and emptied the water which condenses in the exhaust steam pipe. This pipe runs along the top of the boiler from the steam chest and a copper pipe then comes down the side of the smoke box, with a tap at the end.
Having made sure Annie was happy at the front end I went to the back and had a look at the water gauge, pressure gauge and the fire. "80 pounds" I called to Ronnie when he stopped sawing for a moment. He reached for the large piece of wet elm and heaved it onto the bench. This was a test piece! Annie barked several times as the thinner end was cut up. Steady on 80 psi and a beautiful roaring white fire - she ought to manage easily. Next time she barked much more and then her chug, chug slowed down considerably. I looked up at the governor balls and then round the fire box at Ronnie. "Shut her off" he yelled. I quickly closed the regulator and walked to the sawbench. "The saw simply stopped" he said in amazement "It has never done that before". He pulled the wood out and we both looked at it. It certainly was wet and very hard. While we were wondering what had gone wrong the safety valve suddenly lifted! I went back to the engine and looked at the fire. It was perfect and with 90 psi on the gauge Annie had no work to do. I asked Ronnie to slip the belt off so that I could run the engine and work her water feed pump - we had to stop that noise - right in the middle of a residential area!
The fly wheel diameter 5 ft and the total weight of the engine is about 5 tons. Her working pressure is 100 psi, but mostly she is worked very efficiently at 80 psi. She will do a day's sawing on scrap wood equal to about 10 house doors and she is never fired on anything but wood from demolition sites and scrap wood from timber yards. This is mainly the bark and rough outside wood. Her firebox has a grate area of 8 square feet. She has no injectors but a pump can be set to supply the water at the rate it is being used and a large bin of feed water stands under the right hand side of the boiler. The unbalanced crankshaft limits the speed of the engine to 100 rpm. There are two safety valves. One a straight forward spring safety valve, which the owner could set and padlock so that his men could not alter it, and the other a Salter safety valve. She had no whistle and now carries the one from Millom, Ronnie's 0-4-0ST at Quainton.
All Portables had folding chimneys which rested on a U shaped support bolted to the top of the steam chest. The Sussex nurseryman had removed the support and in its place fixed a pipe to take the steam to the soil sterilising unit. That was the only alteration he made and it was easily removed. Ronnie has shortened the chimney by about 2 feet so that when folded it is easier to cover the engine with a tarpaulin. Restoration will be completed when the boiler lagging and cladding has been replaced and the wheels painted. In August she will celebrate her 50th birthday with a suitable party, at which it is hoped she will generate the electricity for her own fairy lights!
Lighting her up from cold takes about 4 hours, but when she has her lagging and cladding on it will obviously be quicker. Locomotive enthusiasts will be interested to learn that Portables have one thing in common with the Steam Engine, the power is transmitted direct to the flywheel (equivalent of the driving wheels) and not through gearing as on a Traction engine.
It took about ten minutes to quieten her down, meanwhile Ronnie had found a bearing had run hot on the bench and was trying to find out what had caused it. I put our pork pies on top of the firebox to heat through, switched off the pump and closed the regulator. Annie sizzled and I checked the oil cups.
Ronnie, having satisfied himself that the bearing had not run dry, came and looked in the firebox. The fire was nearly out. In about 20 minutes it had gone from a roaring inferno to a few red hot pieces of wood. I scrambled for more bits of door, disgraceful of me, I never expected it to disappear that quickly. One advantage is that the fire will pick up equally quickly and soon I opened the regulator and had her chugging away again so that the blast would draw the fire.
But Annie was down to 60 psi so the large piece of elm was leant against a gate post to wait until the end of the year when we hope it will be drier. Ronnie continued sawing smaller wood for use in the house, he doesn't burn any coal these days. I was careful not to let Annie get beyond 80psi and the shattering roar of steam escaping from her safety valve did not disturb the afternoon. But it brought in another steam enthusiast!
At about 2.30 an American woman walked up the drive and said she had been hunting high and low to find out where the engine was that blew off all that steam! There probably aren't many of the builders of 78147 still alive in Gainsborough, but I'm sure they would be very surprised, and probably rather pleased, to know that one of the few remaining Portables still works at one of her original jobs.
Text © Quainton Railway Society / Photographs © Quainton Railway Society or referenced photographer
Page Updated: 28 October 2017