Firing-up a Model Live Steam Engine


Andrew R. Dodge

Copyright 2013 by Andrew Dodge, not to be reproduced by any means without permission, all rights reserved.

Click here to scroll to illustrations

Preparing a steam engine to run on the high-iron is a process that dates back approximately 200 years. In order to make a steam engine operational, one needs water and fuel. Since the heat generated by most fuels used today; coal, oil or propane; generate enough heat to seriously burn steel, putting water into the boiler is the first item on the agenda. Water and steel do not react well with each other, which means that the boiler will have rust and corrosion issues over time. To prevent this problem in today’s locomotives, one can use a chemical stabilizer devised specifically to avoid rust. Terlyn Industries produces a boiler treatment additive for steam engines. It is designed specifically to control corrosion and scale. I put 4 oz. of their product LSB8000 directly in the boiler and add more in the tender as I run the engine during the day. It is my understanding that the train crews on the Durango & Silverton Railroad use it by the gallon in the K 28 and K 36 locomotives that run on the Silverton line.

Because I am operating a 1/8 scale locomotive, I can use just a garden hose to partially fill the boiler with water through the blow-down valves. Blow-down valves are located on both sides of the boiler near the bottom of the foundation or mud ring. These valves are critical in being able to get any excess water out of the boiler during operations, and to blow-down the boiler when finished running the locomotive. During the filling process, I open one of the valves on the turret in the cab to allow air to escape and speed the operation. The water level can be checked by looking at the glass. Once the water level has come up to approximately halfway between the crown sheet and the top of the glass, I know enough water is in the boiler and can shut the blow-down valve. After disconnecting the hose from the blow-down valve, I fill the tender. Because my tender does not have any baffle plates inside to control water slosh, I only fill it to approximately two-thirds full. The tender is three feet long with 16 inches, which is more than enough distance to have water come flying out of the tender if one does a hard stop or has a derailment.

My engine has three ways to get water from the tender into the boiler during operations. Old locomotives such as the Mason at the B&O Museum used cross-head pumps that required the locomotive to move in order to pump water into the boiler. Because of the inherent safety problem if the engine sits too long, two or more injectors have been used on all modern locomotives. Most operating model steam engines have some combination of systems. I have an axle pump on the front driver that operates just like the cross-head pump, one injector under the fireman’s side of the cab, plus a hand pump in the left tender water leg as a last resort if the others are not working.

Firing is the next order of business. Since I use coal as a fuel, I have to create a fire in the firebox that is hot enough to start the coal burning and with a sufficient air supply to feed the fire. In order to create a draft through the boiler tube and into the smokebox, I would have to have a stack approximately 19 feet high, which is not a practical solution. However, there are two ways to create the needed draft. On some club layouts like the Chesapeake & Allegheny in Baltimore, they run a compressor and with the proper jetting of air just inside the petticoat pipe, you can create a good draft. Another method is to use a little electric squirrel-cage motor and fan placed on top of the smoke stack. Both methods will move the smoke up and out of the stack and prevent the cab from becoming a fire danger and keep your eyes and lungs clear of smoke.

To get the coal hot enough to start burning, I use charcoal briquettes soaked in kerosene as the base for the fire. Kerosene is sufficiently combustible to easily ignite but nothing that would be considered too dangerous. After soaking about half a coffee can full of briquettes, I put them on the grates in the firebox. The grates are removable racks something like you would find on an outdoor grill. They are designed to hold the fuel while allowing air to come up from below. Remember, the other five sides of the firebox are steel with water inside. After starting the fire with a match or the more modern birthday cake type match with lighter fluid, I will start the draft with the compressed air or fan. Once the briquettes burn enough to have a gray ash form over the surface, the coal can be added. However, care must be exercised not to add too much coal too quickly since that would overwhelm the fire and suffocate it. Also, you must use a good type of leather work gloves to protect your hands from all the heat. Everything touching the boiler will become extremely hot, too hot to handle. Being careful is paramount, and do not use wet gloves since heat will pass right through the leather and burn you.

The length of time it takes to heat the water depends on how well you have tended your fire and how cold the temperature of the boiler when you first start. Obviously, if the steel is 90 degrees when you begin, the fire will bring up the heat of the water faster than if the boiler is only 40 degrees. Once the fire gets going nicely, it is important to periodically rake the fire in order to break up the coal lumps that have fused together due to heat. Also, this ensures a larger area of burning surface in the fuel and better air circulation. When raking the fire, be careful not to push the fuel up against the flues because you do not want to obstruct them. You want as much heat as possible to go through all the flues so you maintain good efficiency.

Like full size locomotives, the boiler pressure of a scaled down live steam engine varies with the type of boiler. Most operate with a full pressure of more than 100 pounds per square inch. The type I have is Maryland State approved to go up to 125 psi. Once the pressure gets to 50 psi, the locomotive’s own blower can be used and the compressed air or the electric, squirrel cage fan can be removed from the stack, with caution. Caution, because it will be very hot after being in extended contact with the heat of the boiler. While you are greasing all the journals, bearings, and valve linkage, you are also checking your pressure gauge and tending the fire. Once the pressure hits its working limit, the safety valves open in order to protect you and the engine. The low pressure safety valve on my engine opens at 125 and reseats itself at 112 psi, which is important in order to keep as much steam in the boiler as possible and not waste fuel and water. A secondary safety valve that serves as a backup will open at 130 psi, but mine has never gone off other than in state tests to ensure that it is working properly.

It is important to keep the boiler pressure in the 100-125 psi working range so other parts of the locomotive that depend on steam pressure to operate will function as intended. The locomotive brakes are served by a steam pipe from the turret to a valve on the cab floor on the engineer’s side of the cab. These brakes are a closed system so they do not waste steam to operate and function at a lower pressure. However, the train brakes are operated by vacuum, which does need a constant source of steam at a pressure of 90 psi or better. The other item in need of high pressure steam is the water injector. The injector takes steam from the turret and through the use of jets and cones in the body of the injector, the pressure on the water going to the check valves on the side of the boiler becomes higher than the pressure inside boiler. If the pressure is not high enough, the cold water from the tender cannot be injected into the boiler.

After getting the boiler up to full operational requirements and you have completed lubricating the engine, the locomotive is ready to be moved under its own power. The Johnson Bar has been in the neutral position through this entire process so far, but it is time to move it into reverse or forward, depending on your track arrangements, and slowly open the throttle. Hats and safety goggles are recommended at this point in order to protect yourself from water being initially expelled from the smoke stack as the pipes and cylinders are being fed their first bit of steam. Cinders coming out of the stack as the engine works will play havoc on you head if it is not protected.

Another important item on the to-do-list is cleaning out the cylinders. In the cab two valves control the steam lines going to the cylinder valves. These valves must be changed from the running position to the venting position so raw water in the cylinders can be expelled. After a short time of 20 or 30 seconds while moving, the values have to be reset to their standard position so the engine will operate at full efficiency. This entire step needs to be repeated several times as the engine is run during the day.

After a day shoving coal though the fire door and replenishing the water supply in the tender many times, the time will arise to “turn off” the engine. This is not like flipping a switch in the basement train room and going for some coffee. The job is just part of the fun, and it will take up to an hour to complete all your chores with the engine, cleanup and putting hoses and tools away. After some experience, the engineer will learn to have the fire burned down to a minimum level at the end of operations and still have a nice level of water in the boiler. This will reduce the waste of coal and speeds cleaning the firebox and boiler. With the firebox almost empty, it is an easy job to use the tool for raking the fire to hook and pull up the grates. This is known as dropping the fire, which I had to do once with a full head of steam and roaring fire due to a failure in a boiler check valve. Carefully pull the grates out through the firebox door and place them on the ground where they can cool. Do not touch them for at least 30-40 minutes because they will be so hot at times that they will have a nice red glow.

Unless the locomotive burns propane, the smokebox, flues and firebox will need to be cleaned. In order to do this necessary cleaning, the engineer must open the smokebox door, which will still be too hot to touch without gloves. Once open, compressed air can be used to blow out any cinders that did not go up the stack. An extended fitting attached to the end of your air hose will enable one to reach inside the firebox and blow away any loose soot and force compressed air through the flues. If the engine has been worked hard, there will be less soot in the flues and the smokebox, but if not, some of the flues might be totally clogged, which must be clean for the next run.

Once the boiler is clean and set for the next operating session, the water pressure in the boiler should have dropped. Most clubs and many operators want the water pressure to be at or just below 50 psi before doing a blow-down. If you need to speed the cool-down, one can use the tender hand pump to force more cold water into the boiler. When ready, just open the blow-down valves on each side of the boiler and watch the show of all the steam come flying out of the engine. Do not use your hands to open the valves or stand in front of the valves unless you want to get burned and soaked. After the waterworks show, it is nice to use the spray attachment to your air hose to give the engine a bath. Kerosene or some other distillate like #2 diesel fuel can be sprayed on the now cool locomotive to clean the boiler jacket and excess grease and oil on the running mechanism. The locomotive is now ready to be put in the roundhouse, and you can now have your cup of coffee. (You might want to wash-up first.)

As a final thought or two, remember the wording on so many railroad heralds: “Safety First.” Although this is a hobby, remember all the safety issues and follow the rules to avoid any accidents or injuries. Also, be safe by being informed. Working with a live steam locomotive is a lot of fun, reveals many aspects of railroading all too many of us never see today, and you get to experience the thrill of real coal smoke - Railroading at its Best.


Old boiler with rust in the mudring

Boiler maintenance is essential to long life and efficient operations. This is a cut-away of my old boiler that lasted 25 years before the areas around two of the staybolts began to leak. However, after cutting the boiler into parts, it became readily apparent that the entire sidewalls of the boiler were full of rust. When I first looked inside the boiler through the hole in the steam dome, I felt like I was seeing the latest photo of the HMS Titanic. Modern additives reduce or eliminate this problem.

The inside of a model live steam engine cab is a little simpler but in all respects similar to a full size locomotive. The door to the firebox is in the lower center, the water glass is to the left and is positioned to indicate the water level vis-a-vis with the crownsheet. The throttle is by the pressure gauge with the Johnson Bar on the far right. Other valves on the turret operate the vacuum brakes, injector, blower, cylinder blow-downs, whistle, and the engine brake, which is on the right side of the deck.


Finishing firing the engine

Getting an engine ready to run requires attention to detail and a checklist of things to do. Water is the first item, then the fire, then lubricating the running gear, and then constant attention to all. Gloves, safety glasses, and a hat are all on the “must” list of apparel. While checking the fire, one can see the glow from the firebox through the spokes of the last driver. The steam around the running gear is from the vacuum brake, which needs a constant supply of steam to keep the train brakes engaged.


Steam engine in full working order

With the engine in good working order, it can pull its full tonnage rating. On a 3.5% grade Dick Patton is running the Mogul with two cars and caboose without any steam leaks or driver slippage. Under these conditions, protective glasses are essential. Because of the extreme draft in the flues when working this hard, cinders fly out the stack and invariably get into your eyes.