Posted on Leave a comment

How much does it cost to stop a train?

What components do I need for a complete vacuum braking system and how much will it cost?

We are frequently asked what items are required to fit vacuum brakes.

There are of course many different types of locomotives and rolling stock so there is no generic answer.

The example solution shown below is based on a narrow-gauge Romulus hauling two eight wheeled wagons. On the loco, all wheels are braked whilst on the wagons just the rear four-wheel bogie is braked.

 

Product Part No. Description Qty Unit Cost Total Cost
PNR-4R Vacuum Ejector No 1

Required to create the vacuum

1 £78.95 £78.95
PNR-1H Vacuum Limiting Valve

Used to set the limit of vacuum in the system

1 £40.95 £40.95
PNR-3P 7¼” Narrow Gauge Progressive Brake Valve with Lap 1 £195.90 £195.90
PNR-2D Vacuum Brake Kit with Trunnion. This version is to allow for fitting in carriages where space may be an issue. 3 £45.70 £137.10
PNR-1C Vacuum Reservoir

To hold a reserve of vacuum without which the brakes would not be able to be applied

3 £17.00 £51.00
PNR-1G Vacuum Release Valve Employed to allow atmospheric air pressure into the vacuum reservoir 3 £12.00 £36.00
PNR-3U Vacuum Gauge – Brass

Two are required, one to show the vacuum in the train pipe and the second to show what is in the reservoir on the loco.

2 £51.80 £103.60
PNR-1E 1/3 Scale Brake Blocks (Set of 4) 3 £15.80 £47.40
PNR-1J T-Hose Connector 6 £1.45 £8.70
PNR-1M BSP Socket 3 £2.00 £6.00
PNR-1L Male Taper Hose 3 £1.85 £5.55
PNR-1I Clear PVC Tube 3 1/16th 4 m £1.15 £4.60
Example Total Including VAT £715.75

Prices correct as at June 2021.

Posted on Leave a comment

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