Of all the modifications I have made to my Feldbahn, and the Stafford before it, this is by far the most controversial.  To some having a steam engine without injectors is almost sacrilegious while others see it as a way of embracing modern technology, and surprisingly people I have expected to take one stance have often taken the opposite.  My personal preference is to have injectors feeding the water into the boiler simply because that's how it's done on a "real" steam engine.  So why have I made the change ? After a couple of years of tinkering I had the injectors on my Stafford working perfectly and you can read all about those changes on the Stafford pages of this website.  All you had to do on the Stafford was turn on the water, turn on the steam, and water was fed into the boiler.  It was so reliable that you only needed to look down to see when the boiler had enough water in it.  The Stafford had eventually covered over 500 miles and I hadn't even had to clean either injector.  So far as I was concerned the injector system was totally reliable. However when I exchanged the Stafford for my Feldbahn, despite having modified the injector system to incorporate all I had learnt from the Stafford, I only did one lap of the Pinewood track before returning to the yard.  I simply could not operate the injectors while driving.  Eventually I learnt that the Feldbahn injectors needed special treatment.  You had to turn on the water, turn on the steam, then throttle back the water until the injector picked up, then reopen the water flow and set it "just so" depending on variables like boiler pressure and temperature to keep the injector operating nicely.  This meant that the driver spent a lot of time looking down at the injector overflow and not where he was driving.  Once I had learnt the technique it wasn't really a problem on the smooth running Pinewood track, but on rough tracks the injectors had a tendency to stop on most of the track bumps.  The driver thus had to go through a full injector restart procedure, and just as you had got it going you would hit the next bump and start all over again.  To try to solve this annoyance I tried purchasing a couple of different injectors but these either exhibited the same, or in one case, other problems.  I even resorted to asking Station Road Steam about where they had purchased the Stafford's injectors but they were unable to help. Having left Pinewood driving the Feldbahn just wasn't fun so I started investigating what could have been wrong.  Most of the basics for reliable injectors had already been covered.  The output pipe to the clack was quite short, the bends were smooth with large radii, and the pipes were the same size as on the Stafford with no obstructions in them.  Assuming that commercial injectors wouldn't be sold if they didn't work the obvious thing to look at was the water feed to the injector.  The advice here is generally that of making sure the injector can receive enough water, so you don't want anything like tight bends or small pipes to restrict the water flow.  The head of water feeding the injector will also have an affect so the greater height of the Stafford's saddle tank may help, but probably not by much.  The Stafford and Feldbahn both use 8mm pipe to feed the injectors, and I had gone as far as using 15mm pipe in the tender, dropping down to two 9mm pipes linking the tender to my Feldbahn, and finally 8mm through the footplate mounted valves.  The injectors fitted to the Stafford and Feldbahn are rated at 2 2/3rd pints per minute, and with the footplate valve output pipe removed measurements showed that much water would flow out of the valve in 47 seconds.  However if the same measurement was made at the end of the pipe normally connected to the injector it took 135 seconds for the 2 2/3rd pints to flow.  This is half the rate that the injector is supposed to move so the injector actually has to suck the feed water from the tank.  The reason for this restriction is the injector design.  All the of the injectors we normally fit to the Stafford's or Feldbahn's use a 3/8"x32 union nut and nipple for 1/4" diameter pipe, and it's the restriction of that nipple that drastically reduces the flow rate.  The Stafford had the same restriction and worked satisfactorily, but I can't help wondering if this design restriction is actually part of the problem.  Since I don't have the capabilities of making my own injectors I will never know. Anyway, for several years I have been watching the price of suitable electric pumps fall and while pondering what I was going to do about the Feldbahn's injectors I spotted that I could now buy two pumps and a battery to operate them all day for less than the price of a single injector.  Having purchased a pump I tested it while conducting a steam test on the Feldbahn and was very impressed by its capabilities and quiet operation.  On test with the boiler at 120 psi the pump happily fed 3 pints per minute into the boiler, which is slightly more than the injector is supposed to do.  That basically settled any doubts in my mind; my Feldbahn was going to have an electric pump fitted to improve the reliability of the boiler water feed.   Having decided that I was going to fit an electric pump the problem was where to fit it.  My new tender for the Feldbahn had not been designed to have space for the pump, and wherever it ended up on the tender I was going to have to install a high pressure feed pipe between the tender and engine.  It was all looking a bit difficult until I suddenly realised that the pump would fit very nicely inside the original water tank space on the Feldbahn.  Putting the pump there also meant that the high pressure piping was all on the Feldbahn and the existing tender to engine plumbing that had been feeding the injector could now feed the pump.  From then on it was no longer a case of fitting one pump to back up the remaining injector.  My Feldbahn would now have two electric pumps and no injectors !

Electric pumps of this type are sold with a variety of maximum pressure and supply voltage ratings with the cheapest only costing about £12 (as of August 2016) so you can select a pump to suit most model steam engines.  The pump I chose for use on the Feldbahn is generally advertised as being suitable for use in misting systems (air / moisture conditioning) or for window cleaning (those long pole cleaners you see being used to clean office block windows).  The Pro Pump 160 operates from 12 Volt d.c. and is advertised as being capable of providing 160 psi and of pumping 8 litres per minute.  It's rated at 100 Watts (e.g. 8.3 Amps on 12V) and it also incorporates a limit switch to stop the pump if the output pressure exceeds 160 psi. In practice the 8 Litres per minute only occurs when the pump is not providing water against any pressure, and my measurements show that it pumps 1.7 Litres per minute (3 Pints per minute) against the 120 psi boiler pressure while drawing just over 5 Amps from the 12 Volt battery. The revised body style of my Feldbahn no longer has the two bolts that previously retained the water tank, and without removing the cab I could not drill any suitably inconspicuous holes to attach the pump so I had to mount the pump using fixings that were available.  The large triangular plate to which the pump is attached mounts at the top to one of the pressure / vacuum gauge bracket bolts (depending on which side of my engine you are looking at) and to the relevant spectacle plate bracing strut bolt.  At the bottom are two rubber feet with the one fitted to the brass bush being mounted on a length of studding.  When the assembly has been positioned inside the water tank space and the top fixings are tight the studding is adjusted to tightly brace the rubber feet across the bottom of the water tank space. The flexible black tubing is sold for car fuel injection systems and rated at 145 psi so it is adequate for the boiler pressure but I would be relying on its designed factor of safety if a blockage caused the pump pressure to rise to the 160 psi cut off.  In order to not exceed the tubing's minimum recommended bend radius the pump's position within the water tank space has been biased towards the front of the engine which meant that copper pipe had to be used on one side of the pump to create the tight bend radii.  The copper pipe and threaded output connections at the bottom left all have lipped ends to help retain the flexible tubing.  The hose clips are standard automotive fuel hose clips.

This photo shows one of the pump assemblies installed inside the Feldbahn's left hand water tank space.  The yellow and black wires supplying the power for the pump are 18 AWG silicone wire rated at 16 Amps but more importantly also rated for operation at 200 degrees Centigrade.  This is crucial as the wires have to run close to the firebox where normal PVC wire insulation would melt. The circular loop in the wiring is a Service Loop which allows the wires to be longer than needed so that spare wire is available in case the pumps have to be removed requiring the wires to be cut and then reconnected.

The water connections to and from the pump use 1/4" diameter copper tube with normal 3/8"x32 unions and pipe nipples.  The pipes have been routed through the convenient hole in the footplate support.  The larger 10mm diameter pipe in the photo provides a conduit for the pump wiring and these L shaped pipes on each side of the engine are attached to the footplate by means of silver soldered brackets and the existing cab mounting bolts.  Each wire conduit is a slide fit into a copper tube T piece attached to the top of a conduit that runs down and under the engine.  Unfortunately that T piece is impossible to photograph.

In this unusual view from underneath my Feldbahn you can see how the pump wiring conduit (blue arrow) has been routed through one of the holes in the cross brace that appear to have been intended for an axle pump.  Nearer the rear axle the conduit runs vertically up to the T piece mentioned above, and at the left of the photo the conduit ends at the rear buffer bean underneath the removable section of the footplate.  The conduit thus protects the wires all the way from the electrical junction box on the inside of the rear buffer beam to where the wires enter the old water tank spaces. The photo also shows how the pipe between the pump and the boiler clack valve has a T piece fitted (green arrow) with the teed section leading to a drain cock on the inside of the rear buffer beam.  This provides me with a simple way of draining the pipe when the Feldbahn is being stored. The pipe with the horseshoe shaped bend in it near the top left of the photo is the pipe connecting the water inlet on the rear buffer beam to the pump.  Previously the buffer beam water inlets had been connected to the footplate water valves but both of those valves had now been removed and the holes in the footplate blanked off.  The bend was created to allow some flexibility in the pipes actual length because its shape has no natural way of allowing for slight changes in its length due to it being a dead straight "a to b" pipe.  The pipe feeding the other pump is similarly bent although the bend is hidden behind the brake bar in the photo. Those of you familiar with Feldbahn's may be wondering what the black box marked with the yellow arrow is.  That is the electrical junction box for the engines headlamp wiring. If you would like to see this photo as a larger image then please click on it to open a larger version in a new window .

The electrical connection between the Feldbahn and its tender uses a 3 core silicone sleeved cable and a stereo jack plug.  If you decide to use a similar method make sure that you purchase a jack plug that has a suitable current rating.  The ones I use were rated at 10 Amps. Silicone sheathed wire was again chosen for its ability to resist heat.  If you drop a hot ember from the fire on it you don't want the insulation to instantly melt. The brass coloured square on the inside of the buffer beam is the electrical junction box where the 3 core cable connects to the individual wires leading to the two pumps.  It also has a cable tie inside it acting as a retaining clamp to prevent the 3 core cable from being pulled out of the buffer beam.

The pumps are controlled by a pair of push button switches mounted in a small die cast box located in the front left-hand corner of the tender coal space.  To prevent the switches getting jammed up by coal dust etc. I used switches with an IP65 rating which means that they are water and dirt proof. Non latching push button switches were chosen in place of latching switches (either push button or toggle type) because they would ensure that the operator had to keep pushing the button to pump water into the boiler.  If a more conventional latching switch had been used the operator could leave the engine with the pump running and thus overfill the boiler to the point where there was no steam space left at all and water was blasting out of the safety valve.  That would potentially be a very nasty situation and had to be avoided.

This photo shows the storage space inside my Feldbahn's tender where the 20 Ah battery for the electric water pumps is situated underneath the wooden switch panel.  There is still sufficient space for the various oils and water treatment to be carried as well as some tools and waterproof clothing. The wooden panel helps to hold the battery in position and has the battery charging socket and power On / Off switch mounted on it together with a 15 amp fuse in a holder on the left-hand side.  The item with the green coloured screen on it is a power monitor for the pump's 12 Volt battery.  If you have seen electric locomotives operating on a miniature railway you may have noticed that they frequently incorporate coloured LED's to show the drive batteries state of charge.  For a 12 Volt battery they tend to have three LED's denoting full, OK or discharged.  For only a couple of pounds more you could have one of these power monitors.  The display shows not only the battery voltage but also the current being drawn from the battery; and on a cyclic section of the display they show the total ampere hours drawn from switch on, peak current drawn, and the elapsed running time.  This is far more useful than three LED's and as the unit can measure up to 180 Amps and operate from a 24 Volt supply it can also be used to monitor the drive batteries of most miniature railway locomotives.

Here is a photo of the wattmeter's display when I was using it to monitor the batteries of one of my electric locomotives.  At the top right is the battery voltage (the locomotive used a pair of 12 Volt batteries), with the current being drawn at the top left (the loco was stationary when photographed and thus not drawing any significant current.  At the bottom left the cyclic display is showing the total number of ampere hours drawn from the battery since switch on.  The bottom right shows the number of Watts supplied by the battery. For little more than the LED monitor you get an awful lot more information about the state of you battery and what has been going on.  By using this monitor I leant that the two electric pumps on my Feldbahn used just over 2 ampere hours for a 5 1/2 hour steaming session covering 8.95 miles.  The 20 Ah battery I am using thus has far more capacity than needed for a day at the track.

I think that this page should provide all the information you need about using electric pumps to replace the injectors on your model steam engines.  I am certainly extremely happy with their performance even though I would prefer to use injectors, but fitting the pumps has made driving my Feldbahn enjoyable again as well as letting me concentrate on where the engine is going rather than looking down at the injector system. Finally for those of you who would say that an electric boiler feed pump has no place on a model locomotive I would suggest that you consider the following fact.  Full size railway engines generally do not have axle pumps fitted, but how many of you are happy to use them on your models ?