Two teenagers take on an engineering challenge!

Report from Thomas and Lucy Isherwood, 27 February 2021
Thomas and Lucy Isherwood jumped at the chance for something different to do during Lockdown, when the Downs Light Railway Trust contacted them with some problems to solve on the Petrol Hydraulic Locomotive named TIM.
There were a few issues that needed addressing:

  • Excessive noise
  • Loose wiring
  • Engine starting difficulties
  • Engine overrevving

Problem Solving

The first issue addressed was the noise. Lucy and Thomas thought this would be easy by simply adding antivibration mounts and enclosing the noisy petrol engine – how wrong they were. To enclose the engine would mean the controls for the engine - choke, throttle, ignition – in addition to the parking brake, hydraulic dump valve, switches for the horn, and light would all need moving. This was more than they had planned.
CAD Models
CAD models produced by Thomas and Lucy

Lucy explains:

"Thomas came up with the idea of a wooden bulkhead between the Driver’s cab and the engine. We used all sorts of techniques to move the controls. The choke lever was re-designed and then 3D printed to enable connection to a new printed choke knob in the cab via a stainless rod that had to be bent and have a thread tapped on the end. The ignition, horn and light wiring was completely re done and new switches mounted on 3D printed panels. Thomas and I designed these panels in 3D Computer Aided Design drawings."

That was apparently easy in comparison with the hydraulic valves and linkages that were right where the bulkhead had to go. By far the most exciting part for them both was the angle grinder! New steel was sourced, drilled and shaped with much gusto as both found how much easier angle grinding 30mm x 30mm solid steel is in comparison to a hacksaw.

Through dismantling the wiring, and carburettor the overrevving and shorting issues were soon found as wiring diagrams were consulted.

Developing practical skills

Testing their work

As TIM now had a bulkhead, the noise was less but not enough. Before work the noise level was 95dB – you had to shout.

On inspection, Lucy and Thomas found the exhaust was not physically connected to the engine, leaking out noise. Thomas decided a motorbike silencer was needed. He headed off to the weld shop for a day's session of angle grinding and TiG welding.

With this fitted, TIM became much quieter… down to 75dB. You can even talk!

BEFORE

AFTER

Serviceability in Mind

Lucy knows the importance of ensuring the drive chains and links are lubricated frequently, and highlights:
"The bulkhead was in the way, but also the younger children learning to drive TIM never remember to oil."
To solve both problems, Lucy designed bright oiling points in 3D CAD that could be located on the bulkhead. After 3D printing them, they were then connected through piping to where the oil is needed.
Thomas testing the new panel controls

The teenagers found this interlude a much needed break from dull Lockdown screens.

Well done Thomas and Lucy!

Editor Notes

  1. Thomas and Lucy are both long standing members of the Downs Light Railway. Both regularly attend the youth activity sessions during the school holidays.
  2. TIM is a freelance 0-6-0 locomotive, powered by a petrol-driven hydraulic transmission. It is named after the late G T E Cadbury, a former trustee of the Downs Light Railway Trust.
  3. The Downs Light Railway Trust is a charitable trust, registered with the Charity Commission for England and Wales. Registration number is 513882.
  4. The Downs Light Railway Trust's Centenary Development Programme aims to increase youth engagement in heritage railways, provide greater practical learning opportunities and strengthened community involvement. The programme hopes to realise these aims from 2025 when the Downs Light Railway is 100 years old.
  5. The Downs Light Railway was started by The Downs School (Colwall), now The Downs Malvern, in the early 1920s and was formally established in 1925. At over 96 years old, it stands to be the oldest private miniature railway worldwide.
  6. The Downs Light Railway educates on average 15 children on each session. These children are aged between 7 and 18 years old. Dedicated sessions are provided to local educational establishments, such as The Downs Malvern. General youth activities are open to all children.

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