The Telford Train is a long-awaited Mamod product which has undergone somewhat of an eventful journey for the company to bring it to market. Here is the second installment of the inside track on the so-called "runaway train".

After deciding against using a slide valve engine on the Telford, Mamod engineers needed a new approach to powering the model. While the slide valve was giving the train a significant kick, it had trouble maintaining this speed and often became uncontrollable so the company looked at using an oscillating cylinder instead.

The slide valve engine was unable to give a satisfactory performance thanks to steam not being replaced quick enough and the timing event not having a long enough dwell time. The latter is an important function of a model as it determines how the piston allows steam to enter the lower port. When it is all released it can then enter the upper port. If the ports are not open long enough then power will be lost – this makes the duration of dwell time even more important.

An uncontrollable model is no good to any consumer, so Mamod needed to change tact. Introducing a new engine is not a simple process and the Telford had to be redesigned once again to accommodate the oscillating cylinder. The running gear was redesigned and the aesthetics were altered to improve balance and allow for a vertical lubricator.

The oscillating cylinder was produced within three weeks with a further four weeks required for tweaking the engine to ensure that it fitted the requirements of the Telford. The move to larger engines that standard parts needed to be scaled up and this saw the introduction of a standard mark two engine running frame attached to the Telford's body. This underwent a series of tests to determine its performance durability.

Next was the introduction of a new chassis frame which was specially designed and fitted. Once again, this underwent a rigorous testing phase with the engineers this time looking at the balance and performance of the new equipment. This process however was not without its problems and engineers needed to find a way to redirect the steam pipe to the new vertical lubricator, which took a number of man hours to rectify.

The Telford is unlike many other models built by Mamod as it requires a lot more cosmetic attachments. It has been a labour of love to get it to this stage but the engineers noted their pleasure at the first test runs. The Telford performed well after the various tweaks it has undergone and managed to shake the "runaway train" tag.

Mamod has a number of plans for the rollout of the Telford. It is initially being sold as a 0 gauge but there is scope for the development of a gauge 1 version. While there are no plans for the Telford to be sold as kit, the company did make a one-off kit version at the special request of a customer. However, the firm stresses that this very much a special circumstances case and the feedback on that will depend on whether it is rolled out in the future.