Thoroughly Modern Millie

Review of the new Roundhouse basic engine
This article appeared in the November 1999 issue of GardenRail magazine and was written by David Pinniger. All photographs by the author.

I was very pleased to receive a new 'Millie' for review as it is the first Roundhouse loco which 1 have formally reviewed since 'Charles Pooter' way back in 1984. A lot of engines have been round the Ambledown Valley track since then. In fact, according to my record book there have been 143 different steam engines which have run on the AVR in the 15 years between the test of `Charles Pooter' and the `Millie'.
The strange thing is that there have been a lot of developments over those years which have resulted in some very sophisticated steam engines with multi-channel radio control, scale valve gear, all the right rivets and of course, real coal firing. Yet what we have in the `Millie' is a deliberate "back to basics" steam engine, built down to a price which is intended to attract people into the hobby of steam in the garden. I hope that this review will give readers at least one opinion on whether Roundhouse have succeeded or not.
`Millie' is offered as a basic engine with additional refinements, which can be added by the owner but the engine which I had for a few weeks is the very basic version. The locomotive is a neat 0-4-0 with side tanks and a cab spectacle plate, a full cab is available as an optional extra.
My `Millie' was maroon but the engine is also available in green. It has two standard Roundhouse slide valve cylinders which are identical to those fitted to the top of the range engines. This is a very important feature which shows that although `Millie' is built down to a price, it is not at the expense of quality of the power unit. Where `Millie' differs from her more expensive sisters and brothers is that the slide valves are operated by simple slip eccentric and not a lever-reversible gear.
The boiler is also different in construction from the other centre flue gas fired Roundhouse engines in that it has a flueless boiler with burners underneath, what is commonly known as a pot-boiler. Older steam fans will be very familiar with slip eccentric pot-boilers as they were in the majority in the 70s and early 80s and many of us first burnt our fingers and got the steam bug thanks to Archangel pot-boilers. Although despised by some model engineers, the steam generation from pot-boilers can be very efficient with the correct design of burners, shielding and draughting.
Roundhouse pioneered the commercial development of efficient pot-boilers with the `Charles Pooter' design mentioned earlier. Although this was meths fired, the principle of a firebox around the boiler to protect and guide the hot air to heat the boiler without wasting energy was identical to the one now used on the `Millie'. This firebox unit was coincidentally developed at the same time by both Jack Wheldon, who originally designed `Charles Pooter', and Roger Loxley who built the modified engine commercially as a Roundhouse product. With a pedigree like this, `Millie' obviously has a reputation to live up to.
Although `Millie' is not based on any particular prototype, she has the look of a small but robust industrial engine built for substantial work in a quarry or gasworks. With a bit of imagination and embellishment she could also be at home in all quarters of the globe on one of the many overseas narrow gauge lines which employed engines built in the UK. She is an 0-4-0 side tank and my basic version had a simple cab spectacle plate. There is a very neat and well proportioned chimney and a safety valve/boiler filler on the top of the boiler just in front of the cab plate. The regulator is mounted on a turret on top of the boiler at the: back and has a long handle for ease of operation. Because of its position, you need a long gas filler adapter to fill the gas tank.
The steam oil lubricator is mounted on the left hand side of the engine with a large knurled filler screw on the top and a smaller knurled drain screw under the footplate. The gas tank is mounted at the back of the footplate with the filler valve on the top. The gas regulator valve is a simple knurled knob.


'Millie' on the AVR just arrived from Doncaster Works.


Rear view of 'Millie' to show the large regulator handle from the turret.

Looking underneath the footplate, we find that the slide valves on each side are operated by a rod driven from an eccentric mounted between the wheels and the loco frames. This neat arrangement does away with the rockers which are necessary if the slip eccentric gear is mounted between the frames in the manner of the Roundhouse Lynton & Barnstaple engine. My old Lindale `Caledonia' has this arrangement of wheel-driven slip eccentrics and after 20 years of trouble-free operation I think that I can vouch for its reliability. `Millie' is available as a 32mm or a 45mm gauge version but because of the positioning of the eccentric gear, the loco is inside-framed and this means that the wheels are not re-gaugable.
The instruction manual is very comprehensive and pays particular attention to those features peculiar to the operation of a slip eccentric pot boiler.


Looking from below to show the rod from the slip eccentric behind the rear wheels which drives the slide valves

This is very important as there is a whole generation of garden railway enthusiasts who are used to the relatively easy start up procedure when running a locomotive with radio control and fully reversible valve gear.
`Millie, is prepared for a run in the usual way with steam oil in the lubricator, gas in the tank and pure or distilled water in the boiler. The instructions tell the operator to fill the boiler and then remove 30m1s of water before replacing the filler cap. As you will see from my comments later, this is the only point which I think needs same modification. As the gas burners are under the boiler and not in a flue, the procedure is to crack open the gas valve and place a lighter near the space between the side tanks and the boiler. The gas should light and burn very quietly, if it roars then it is far too high and should be turned down.
Now it is a question of putting a bit of oil on the piston rod and eccentrics and waiting patiently. The basic version of 'Millie' has no pressure gauge to tell you what is going on in the boiler and so it is important to get to know and interpret the steam signs. I ran the engine on a number of occasions and the first sign of life was a burbling from the boiler about 6-8 minutes after lighting up followed by a small amount of water from the safety valve. After a few more minutes, steam would start to lift from the safety valve and we are ready to start.


"Millie' visiting Gary Hawes' Wooburn Green line showing the gas tank and my temporary lever on the gas valve.

It is a fact of life that hot water expands and that although 30mll was removed from the full boiler when it was cold, there will be very little steam space when the water boils and exceeds l00 deg. C. In addition, the generated steam condenses into water when it reaches cold cylinders. Some water will squirt out of the chimney but as it cannot easily escape through the slide valves, it causes the wheels to lock in what is commonly known as "hydraulicking".
A full-sized engine, and most miniature steam locos, of course have cylinder drain cocks to get rid of this condensed water. With a lever-operated gear it is a relatively simple matter to keep opening and closing the regulator in alternate forwards and reverse gear to clear the condensed water. With a slip eccentric loco, the water must be cleared manually by gently holding and pushing the loco and at the same time opening the regulator a little then closing it again while keeping the engine moving. With a bit of practice the cylinders can be gradually warmed up and cleared of water. It will take a bit of physical effort and a few minutes of a patience and is much easier to do on an elevated line than a ground level one.
There are two things which I have seen impatient drivers do with other slip eccentric, pot-boilered engines that you must not try with `Millie'. One is to force the loco backwards and forwards with the regulator open in an attempt to free it. The condensed water can force the valve gear and wheel quartering out of true. The other "no-no" is to open the regulator wide and give the loco a shove. This can result in jack rabbit jerking as water sloshing in the boiler is pushed over into the regulator. In addition, if this practice is attempted when the engine is almost warm, it may suddenly clear and with the regulator wide open, the engine accelerates like a space shuttle before piling off at the first bend. What you must do is to really follow the instructions and after a few runs you will wonder what all the fuss was about. I found that `Millie' took a few minutes to clear her throat and I always ran the engine around the main circuit for a couple of 2O yard laps to really warm the cylinders before attaching the engine to a train.


Pausing at Higher Buxton with the light test train. Keen observers of the AVR will notice that Higher Buxton now has a splendid new building made by Stewart Currie.


Getting to grips with the seven coach heavy weight test train, 'Millie' shows what she can do.

On my first run with 'Millie', the engine ran rather erratically with a lot of priming on the first circuit but after two circuits, the engine was warmed up nicely and I attached a short train of five 4 wheeled AVR coaches. As the safety valve was blowing hard, I turned the gas down. The engine set off very smoothly and sedately and ran once round the main line before slowing to a stop. I then realised that I had turned the gas down too much and the fire had gone out. After re-lighting the gas, pressure soon built up and the engine set off again and proceeded to run very well for the next 20 minutes before slowing again as this time it was out of gas.
After the run, I checked the level of water left in the boiler and found that there was 65m1 remaining. The next time I refilled the boiler, I removed 50mI rather than the recommended 30m1 and had far less trouble with initial hydraulicing and clearing the cylinders.
On all of the many subsequent runs, I removed 50mI from the full boiler before the start and I always had between 35m1 and 55m1 of water in the boiler at the end of the run. I can understand that Roundhouse have to err on the side of safety in their instructions, but I do not believe that by removing 50mI rather than 30ml you could run run the engine out of water on one gas tank.
After my experience with the first run and the difficulty of knowing how much the gas valve is open, I decided to add a marker to the knob. As there was already a tapped hole in the knob, I simply added a brass 4BA screw which can be seen in some of the photos. This was not very elegant, but served its purpose in enabling me to exactly set the required flow of gas. I would recommend that any prospective purchaser of a Millie' also buys the optional brake handle as this will look much nicer and only costs 4.80 plus VAT.
The next run on the AVR was very similar to the first except for the removal of the 50mI of water from the boiler as mentioned. The gas was turned down after the loco got under way with a train of three bogie coaches and I was able to set it so that is was not blowing the safety valves, but providing ample power for climbing the bank. I ran around the train at Higher Buxton and found that 'Millie' ran equally happily bunker first until the gas ran out after 25 minutes.
For the third run I went visiting and took 'Millie' back to Yorkshire for a run on John Chambers' Garth End Railway [Transitional]. This is a simple 14 yard circuit of track from his late-lamented Boyn Hill Railway uprooted from Berkshire and laid temporarily in the new garden. On a rare balmy Yorkshire evening we lit up 'Millie' and after two circuits 'light engine' we attached a light load of two of John's BHR coaches. I was interested in seeing how far the engine would run continuously if left alone and so I set the gas low and gas and steam ran out, a total of 1 ,244 yards or nearly 3/4 mile. The run took 26 minutes and at 1/20th scale this works out at 14 scale miles at a speed of 32 miles per hour. Not bad for a small engine!
After a few more runs on the AVR and on Gary Hawes' Wooburn Green line where 'Millie' got admiring comments from a number of people, I decided that as the engine was well run in, I could try a maximum load test. This is never wise with a very new engine, but 'Millie' now seemed to be performing very well with no stiffness at all. For the load I chose a selection of fairly heavy AVR bogie coaches, two of which had not had an outing for over three years. I raised steam as usual and after one circuit light engine, attached three bogie coaches which were pulled with consummate ease. To give the engine more of a task I attached another four bogie coaches giving 28 axle train with a total dead weight of 15Ib 4oz.
For the first time on the AVR 'Millie' was having to work hard and the exhaust when she went up the bank was quite audible. She was also now using more steam and after she stopped on the bank I opened up the gas valve a little to compensate. The engine ran beautifully with this heavy load and I was able to set the regulator so that she just crept up the incline at Higher Buxton and then ambled down the other side to Hinton Magnolia.
After eight circuits I decided to add a few more vehicles to see just what would be the maximum load that she would pull. Five old AVR 4-wheelers were dusted off and coupled on the back of the train. With 38 axles and a total weight of 18lb l4oz, this train did make 'Millie' lose her feet when I opened the regulator rather too fiercely. However, with careful driving she got the train away and pulled it steadily around the main line. After four or five circuits it was clear the rail was becoming greasy as 'Millie' was briefly losing her feet on the bank. I did not want to put any undue strain on a borrowed engine and so I dropped off the four wheelers in the passing loop and carried on running the seven coach train until the gas ran out. After this rather extreme 20 minute run with the gas well turned up so that the safety valve was lifting almost continuously, there was still an ample 35ml water left in the boiler at the end of the run.
Reluctantly, it was time to parcel up 'Millie' in the bubble wrap and send her home to Doncaster. I think that my opinion of the locomotive must be fairly clear from my description of the various runs on the AVR and elsewhere.


A pretty fair load for an 0-4-0! 12 coaches weighing 18lbs 14oz being dragged round the AVR.

If you want an all-singing, all-dancing, 'rivets on the coffee pot', loco then look elsewhere. But on the other hand, if you want a powerful, docile and reliable machine at a realistic price then 'Millie' is a very good buy.
There appears to be absolutely no compromise on quality or performance and for a little extra money the buyer can get the optional cosmetic extras of a dome or a full cab. There are also mechanical extras including a pressure gauge, boiler filler system and water gauge, gas regulator and regulator for a radio control servo arm. I would recommend that if any prospective buyer is at all put off by my comments relating to priming and hydraulicking then they should consider adding a boiler filler system and water gauge. This means that you know the exact level of water in the boiler at any time and can therefore raise steam with only half a boiler of water. The additional luxury of a pressure gauge means that you can set the gas flow so that 'Millie' maintains sufficient pressure to pull a train but does not waste steam at the safety valves. As I mentioned before, I think that the gas regulator is well worth the extra cost to enable you to set the gas flow accurately.
Overall, 'Millie' gets a very big thumbs up from me. In 1976 1 bought my first live steam engine which was a simple pot-boiler with slip eccentric gear and I really enjoyed running this simple but very effective modern version.
I think that 'Millie' will give many newcomers a splendid introduction to the hobby and a lasting taste for live steam. For those of you who already are hooked, why not forgo 6-channel radio control for a while and buy a nice simple loco to pull trains round while you relax and enjoy a pint.


Millie pausing at Higher Buxton with the light test train.

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