Updated: Feb 26, 2021
The new 4tonne casting outside Boro Foundry
After more than a few trials and tribulations, the first of the two new cylinders for 4709 have now been cast. Preparations are well advanced to cast the second cylinder shortly for the Night Owl.
4709’s Chief Engineer, Paul Carpenter explains; “Premier Patterns in Smethwick produced the polystyrene patterns, which were completed and inspected during February 2020, then dispatched to the Shakespeare foundry in Preston for casting. This foundry had successfully cast locomotive cylinders using poly patterns for several other projects, but luck wasn’t with us - on the day our patterns arrived at the foundry, the company was placed into receivership. We were fortunate to be able to extricate the patterns from the receiver and a search was started for another foundry. We quickly discovered that in our modern manufacturing world, the number of suitable candidates is significantly less than a century ago, when 47xx cylinders were first being cast.
"We contacted every foundry currently producing cast iron products, only to discover little enthusiasm for the project. Either the sheer size and volume of the casting or concerns centred around the specialist knowledge required to work with polystyrene patterns, caused most to decline to bid for the contract. Months were spent in detailed discussions with one foundry, only to have them decide at the last moment that they too could not deliver the castings,” adds Paul.
Background enquiries identified one specialist; a man who had worked successfully with polystyrene patterns to produce locomotive cylinders. From the first discussion with Alan Boulton, it was obvious that he was a man with both the specialist knowledge and a genuine enthusiasm to deliver this work – he clearly possessed the ‘can do mentality’ required and on his recommendation, Boro Foundry were contracted to deliver our castings. This foundry has often undertaken work for our parent Great Western Society and are currently machining the coupling rods for the County 1014 Project. With a full team and the necessary skills and experience on board, Boro Foundry’s Sam Edwards, Alan and the 4709 engineers started on the research and development work necessary to ensure the casting process would succeed. Working as a single unit, the team re-engineered the casting process for steam cylinders with poly patterns from first principles.
“It’s taken a year of hard learning and steely determination, but finally, at the end of a tough year, the first casting is complete. The success of this project represents an important development for the casting of locomotive cylinders for our heritage world. Without doubt, Boro Foundry are now the centre of excellence for this specialist work and we are very grateful to both them and Alan Boulton for their commitment to the challenge. We are also very grateful to our good friend Mike Solloway, who on our behalf, has made regular site inspections. His experience and knowledge from casting cylinders for his own engine has been invaluable,” concludes Paul.
The 4709 group’s treasurer, Richard Croucher adds; “Bob Meanley was invited to produce drawings for the cylinder block redesign and his drawings would surely have delighted Churchward himself. In addition to his work as a first-class locomotive engineer at Tyseley Locomotive Works, Bob is also an excellent draughtsman. On top of his work on the cylinders, he has also produced detailed drawings to allow new front and rear cylinder cover patterns to be made. The pattern for the second cylinder block is now being prepared at Boro Foundry and a date for the cast is anticipated shortly. Once both blocks are completed, they will stress relieved in a furnace before being delivered to our machining specialist, who is ready to start work,” adds Richard. “This has been a very challenging year for the project but we have managed to make good progress in spite of the pandemic and all the many issues that this has created.”
The Cylinder Blocks
The new cylinder blocks have been redesigned and manufactured to bring the width and height within the current Network Rail Loading Gauge – essential for future mainline running and similar to the design adopted for 6024 - King Edward I. Bob Meanley also produced an assembly drawing to show how best to fit the donor 41xx pony truck to 4709. This last drawing was essential to support the work on the pony truck by Leaky Finders in Exeter and ensures that all the many critically important interface details have been addressed. Timber patterns for the new cylinder covers, as well as the two huge Compensating Beams have now been ordered.