Wagon Drawbar or Buffer Spring - 9 inch

What is a Wagon Drawbar or Buffer Spring

The Wagon drawbar, or buffer, spring is a relatively simple-but-large rubberised washer.  Used primarily on freight trains, or wagons, a series of these large rubber washers are stacked to create a long rubberised column. 

This long rubberised column effectively becomes a rubber spring, which acts as a shock absorber, as per the below image.  Note: additional plates have been added between each spring, which is considered good practice for both performance and product longevity reasons.

For wagons, this long shock absorber is typically used in two places:

• As a drawbar (or draw-bar, or draw bar) spring:  As one wagon starts to move and to pull, or draw, the wagon behind it, tension in the chain or link connecting the two wagons could result in high shock loading, which is both uncomfortable and shortens product life - something would break pretty quickly.  To reduce this shock loading, the connections in each wagon to the chain, or link, use a stack (column) of  these springs.  The spring stack is hidden from view.  The 'tow hook', or draw bar on the wagon, at the end of the chain connection is held in place by this stack.
• As a buffer spring: To each side of the chain, or link, that connects the wagons together, is a buffer.  These two buffers are there to slow down, or stop, the wagon.  As for the drawbar springs, a similar stack of these springs cushions the impact one wagon would have on the next.

These stacks are typically held in place on either the inner diameter, or the outer.  When using the inner diameter a bar is usually inserted down the middle.  There is also commonly an additional plate between springs as this adds further functionality.  Unless otherwise specified, these additional plates are not supplied with the parts.

9 Inch Rubber Buffer Spring

This draw bar or buffer spring is a round 9 inch version.  The measurement is the diameter of the outermost rubber ring.  Depending on the wagon, it is used in either draw bar or buffer spring application.

Materials:

The materials used are as per the original product specification and spring rates.  At a high level, the materials are:

• Metals: Mild steel, S275.
• Plating: Sherardize zinc plating
• Rubber: AVMR's blend with a predominantly Natural Rubber base.

Deflection:

The below deflection curve for the 9 inch drawbar spring, or buffer spring, shows the force-deflection curve for a single produce when loaded loaded in compression, with a maximum load of 3,000 daN (or 30 kN, or circa 3 tonnes).

The first test (green-yellow line) is typically slightly softer than subsequent tests as the rubber settles into position.  The test data to use is after a number of cycles.  This product (without pre-compression) will typically deflect 1.2mm for every 1,000 daN of compressive force applied.

Lead Time

This product is manufactured in house.  Depending on volume, we can typically deliver in 1 month, although this has to be quoted.  For the given prices, lead times are 3 months.