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Baltic Tank 4-6-4 Locomotive

 

At the start of this time of self-isolation, I made a foray down to our garage, where some of our locomotives and rolling stock are housed, along with a variety of other bits and bobs. I was just contemplating one of my father’s miniature steam plants that he must have built way back in the late fifties, and just as I was trying to place where the piece of lino that was on its mounting board was from, my other half pointed out a puce green locomotive.

At first glance, to my untrained eye, she looked rather ungainly a long lanky tank engine with quite small wheels, to make it worse it had a funny sort of Tender truck behind it that I later found out was not a natural pairing for this locomotive. “Odd” I thought, but being no oil painting myself I kept quiet, as hubby launched into an explanation of what this 5” gauge locomotive was and why she was special.

Firstly, her size is unusual as this model is a 5” gauge reproduction of a prototype 5’ 6” broad gauge locomotive so a scaling factor of 1:13.2 has been employed to build this model. Normally for models of standard gauge (4’ 8½” ) a scaling factor of 1:12 or (actually 1: 11.3) for the purist using 1 1/16” to represent 1 foot is employed.

I was informed of this before he told me that she was a model of a Baltic tank 4-6-4 locomotive. She is a 3-cylinder tank engine built originally to service The Buenos Aires and Pacific Railway that was in service between 1886 to 1948. These 4-6-4 tank locomotives were designed and built by Robert Stephenson and Co. and this particular type of locomotive was built between 1928 and 1930. This model Baltic tank engine’s number is 2367 and as it worked on an Argentinean Railway you can see that the number plate is reproduced in the Spanish language Ferro Carril De Buenos Aires Al Pacifico.

Apparently, the name of this “Baltic” locomotive tank engine comes from the very first 4-6-4 tender locomotive, a 4-cylinder compound locomotive designed by Gaston du Bousquet for the Chemin de Fer du Nard in France in 1911. The 4-6-4 was designed and built for the Paris to Saint Petersburg express and so was named after the Baltic sea. This model Baltic tank engine is a copy of one designed and built by Robert Stephenson and Company Ltd, Darlington, engineers, as mentioned above. It was awarded a Highly Commended certificate at the 50th Model Engineer Exhibition, also at a Midlands Model Engineering Exhibition sometime later, and bears a plaque attesting to this on the front just below the smokebox.

I was looking at the 4-6-4 wheel arrangement on hubby’s model Baltic tank locomotive which according to my mentor is a fairly good wheel arrangement for passenger tank locomotives. However, more commonly a 4-6-2 arrangement is often employed. The beauty of a tank engine with carrying wheels at each end of the locomotive is that it can run equally well forwards as backwards and hence does not need to be turned on a turntable. The 4-6-4 is well suited to high speed running across flat terrain because this type of engine has fewer driving wheels than carrying wheels, hence a smaller percentage of the engines weight contributes to traction compared to other engines with more numerous driving wheels. The 4-6-4 is therefore more suited to higher speed passenger travel rather than hauling heavy freight or slogging up sustained grades and inclines.

The 4-6-4T, is essentially the tank locomotive equivalent of the 4-6-0 tender Locomotive, but they have water tanks and coal bunker supported by four smaller wheels trailing behind the engine instead of a tender.

Hubby’s model has three cylinders. The external (outside) cylinders valve gears are Walchaert’s, but the internal (inside) valve gear is Stephenson’s link. The inside cylinder drives an internal crank on the middle axle, as do the outside cylinders so they all drive on the same axle. The middle cylinder sits over the front bogie. This front bogie even has a swing-link system, so it is in effect a self-banking bogie. The turbo generator which can be seen on the images is capable of running the front or rear head lamp depending which way the locomotive is heading on the train. Powerful headlamps were necessary on the routes served by these locomotives, owing to the fact that many parts of this railway were unfenced, and obstacles and wildlife had to be detected early on the route.

The model has a non-prototypical four-wheel coal and water tender which when the removable part of the cab and imitation bunker coal is removed, makes driving much more convenient while adding to the distance that can be covered without stopping. All in all, a lovely model acquired from Robin West of View Models on the understanding that some refurbishment is required to bring it back to its former prize-winning condition.

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Introduction to Vacuum Braking System

It is becoming increasingly important in the interests of safety that passenger-carrying trains should have good automatic (fail safe) brakes.

                   Brake Valve                                                             Vacuum Reservoir                                                         Vacuum Brake Actuator

As on full steam railways the two main choices are between Vacuum and Compressed Air. Both have advantages and disadvantages.

Compressed Air

Advantages: High air pressure means only small brake cylinders are required which can easily be fitted into small spaces on vehicles. Air leaks usually easy to trace.

Disadvantages: Air pump (compressor) always required. Pressure vessels required for reservoirs. Pressure connections required on all pipe work.

Vacuum

Advantages: On steam engines vacuum can be created by a very small ‘ejector’.  No pressure vessels required for reservoirs. Pipe work and connections can be simple plastic push on fittings.

Disadvantages: On none ejector fitted locos a vacuum pump is required. Low air pressure means relatively large brake cylinders (actuators) are required which may be awkward to site. Leaks can be difficult to find.

Because of its inherent simplicity and since most miniature railways and model engineering societies have steam engines, the popular choice is the vacuum braking system.

      Vacuum Ejector                                                        Vacuum Limiting Valve                                               Vacuum Release Valve

How Do They Work?
• The ejector or vacuum pump draws the air from the train pipe, the brake cylinder and the reservoir (via the none-return valve). The brakes will then be off and the system will be in equilibrium.
• The brakes will be kept off by being weight biased or lightly sprung. Please refer to the diagram.
• Letting air back into the train pipe via the drivers brake valve or a pipe disconnection the air pressure acting on the underside of the piston or, in this case diaphragm, will push the piston up and pull on the brakes.
• Since the vacuum on the upper side of the piston is trapped by the none return valve the vacuum must be recreated in the train pipe to release the brakes.
• Similarly when the loco is removed and the brakes need to be released to shunt the train this trapped vacuum can be destroyed by opening the release valve.

See our working schematic of a Vacuum Braking System

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Make ’em look rusty they said………………

t’s a bit of a juxtaposition really. Manufacturing a brand-new product and then getting very intense and spending a not inconsiderable sum of money to make them look aged, weather beaten and corroded. But that’s exactly what we did with our PNP railways chairs.

It’s very important to us, and I’m sure you, that everything about your miniature railway looks as authentic as possible. So, we kept at it, varying the colour blend, moulding hundreds of chairs and then lining them up on a big bench to see if we had achieved the look we were after, until eventually we were happy. What I mean is we kept at it until the boss was happy. They really do look like the real thing. (Why does that make me thirsty?)

Rusty Chairs

 

 

 

 

But one thing that, thankfully, isn’t authentic, is the price. A collection of five cast iron railway chairs is on offer on E-bay at £300! You can get one of our chairs for as little as £0.13, which you could look at it as a saving of 99.96%. What a bargain.

So, six words that you, and definitely I, need to remember about chairs:

Wood – Plastic – Screw – Clip – Surrey – Bar

Wood: Because we make plastic chairs that can be mounted on wooden sleepers

Plastic: I think you can guess this one, but just to be thorough: We make plastic chairs that can be used with our own plastic sleepers.

Screw: We make chairs that be fixed to either wooden or plastic sleepers using screws. and are suitable for light and heavy use including club and commercial environments,

These are ideal for garden railways and indeed club use if 5/8″x 5/8″ rail is considered adequate for the weight and traffic to be handled.

Surrey: We make a standard scale or narrow-gauge Surrey rail chair to go with our 5.2ib yard flat bottom steel rail. These have a 3° cant and are for use with our 7¼”plastic sleepers or can be mounted on wooden sleepers.

Bar: Because I’m really getting ready for a drink……………….We can supply chairs to secure 10x20mm or 12x30mm bar rail to either our plastic sleepers or wooden sleepers.

PNP Rail Chairs

The other thing that my boss told me to mention is that all our chairs are manufactured using a very tough, rot and frost resistant and UV stabilised polymer. In English that means they are made from hard wearing plastic. Oh, and you will also benefit from automatic gauge widening if you mount our plastic chairs on our plastic sleepers.

There is more, isn’t there always? And pictures and diagrams and technical stuff with words like “gauge” and measurements but if you want to immerse yourself in that then why not take a look at pnp-railways.co.uk  and immerse away.

NB When I say “our” plastic chairs and sleepers that is because we really do manufacture them, right here in our factory in a very pretty part of the Cotswolds called Woodchester from whence I pen this article.

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Brakes, brakes, brakes

When they said “write a brake blog”, I thought “how arresting”.

Brakes. They’re pretty important things are brakes, something that many of us take for granted. Now that’s quite a blasé statement about something on which your life could, and probably will at some point, depend.

Arresting motion is what brakes do. You can slam them on in an emergency or gentle kiss the controls to come to a graceful inertia free halt. Ever wondered how they work? What actually happens to get that brake block pushing on the wheel?

Generally speaking, when it comes to railways, there are two types of braking systems in use. Compressed air which is now the more favoured and vacuum brakes which was the standard for UK and all worldwide UK design-based railways worldwide until the early 1980’s.

Initially introduced in the 1870’s, the advantage of using vacuum brakes on steam hauled trains is that the vacuum can be created by a very small ejector or pump and that all pipe connections can be simple push on fittings as there is no need to maintain pressurised connections. Take a look at our vacuum hoses.

The brakes are controlled through a brake pipe that connects a brake valve to the braking equipment (brake blocks that press on the wheel) on each carriage and engine.

A vacuum ejector removes atmospheric pressure from the brake pipe to create a vacuum. With a vacuum created the brake is released. By opening the valve and allowing air into the pipe this pushes on the diaphragm which moves the lever that applies the brakes. The emergency stop chain on old BR carriages was connected directly to the braking system. If the chain was pulled it immediately opened the valve to allow air in and slammed on the brakes. The driver had no control over this.

On a driver’s brake control valve there are a minimum of three positions:

On: Air in = brakes applied.

Lap: Air pipe closed = Ready to apply or release brakes. Holds the last setting.

Off: Equilibrium in vacuum brake cylinder = brakes released.

So, when air is allowed into the pipe to engage the brakes a piston rod is moved by the diaphragm. This piston rod is connected to the brake blocks and forces them against the rotating wheels. This creates friction which converts the kinetic energy to heat. The wheels slow down and eventually the train stops.

As with any braking system if the force used to apply the brakes exceeds the traction of the wheel on its running surface then you destroy the braking process and will initiate a skid. So you need to be gentle, particularly on surfaces and in conditions that reduce friction, such as cold and ice, or leaves on the line.

Vacuum brakes are most suited to steam hauled trains although they can, and have, been used in the past on both diesel and electric hauled trains. On locomotives not fitted with an ejector a vacuum pump is required to create the initial vacuum, and maintain it.

There is a great schematic on our website which explains the process beautifully.

And after all that, what I really need is a break…………………….