WH Scott
Chilbolton Observatory Counterweight Replacement Project
Precision-engineered replacement of critical antenna counterweights using bespoke temporary works and safe access systems.
Project Snapshot
Client: STFC Chilbolton Observatory
Location: Hampshire, England
Provider: WH Scott
The Challenge
The Chilbolton Observatory operates a 25-metre antenna weighing approximately 125 tonnes, relying on a complex counterweight system to maintain balance and precise movement. After more than 50 years of exposure to environmental conditions, the steel counterweight plates had deteriorated and required full replacement to maintain operational performance and safety.
Each side of the antenna consisted of 16 counterweight blocks, with each block weighing 425 kg. This resulted in a total counterweight mass of 13,600 kg that needed to be carefully removed and replaced. The challenge was further compounded by restricted access to the underside of the structure and the need to ensure structural integrity throughout the works.
A critical requirement was to carry out the removal and installation without compromising the stability of the antenna, while also enabling continued movement of the structure during the project.
The Solution
WH Scott conducted a detailed structural survey to assess load-bearing elements and determine safe working conditions. Based on this, a bespoke temporary works system was designed in collaboration with Mabey to provide secure access and support during the replacement process.
The solution incorporated two Mass-50 support towers with longitudinal outriggers and raking bracing members to ensure stability. A custom-designed skating system was also implemented, allowing the working platform to be efficiently repositioned. This enabled uninterrupted antenna rotation while providing safe and repeatable access to both sides of the counterweight system.
Replacement counterweight plates were manufactured at WH Scott’s fabrication facility in Wexford, Ireland. A new permanent supporting arrangement was also designed and installed to replace the temporary system. All affected structural surfaces were prepared and repainted prior to final installation, ensuring long-term durability and compliance.
The Outcome
Key Results:
- Successful replacement of 13,600 kg of counterweights across both sides of the antenna
- Maintained structural stability and operational capability throughout the project
- Improved longevity and reliability of the antenna’s balancing system
Additional Notes:
The project concluded with the completion of a full design report and formal sign-off, confirming compliance and successful delivery of all engineering requirements.
