Sunday, 8 June 2014

New Trousers in the Making!

A couple of years ago, I held a Wrong Trousers Appeal. I have to admit that there wasn't a huge response to the appeal but there has been considerable progress since.

The problem facing Sentinel 7109's chimneys was that the original cast base units were well past their best and that to use them would have only led to a long outage soon after becoming steam-worthy again.

A pattern had to be made to make the mould for the castings. It was made in four parts (with possibly a fifth but I've never been able to figure out where it could fit!).
Front (1) Outside Profile
Front (2) Inside Profile
Rear (3) Outside Profile
Rear (4) Inside Profile
Sentinel, possibly due to their former ship-board equipment product range, used the term 'Funnel' rather than 'Chimney.

Six castings were eventually requested: a prototype for Sentinel 6515 'Isebrook' at Quainton Road; one each for the Sentinels at the Middleton Railway, Elsecar Heritage Railway and the Bo'Ness and Kinneil Railway and finally two for 7109.

This is the prototype used to check that the pattern was correct.
Prototype casting before machining
The new castings have an additional feature to allow extra exhaust steam to be directed up the chimneys. The feature was requested for Isebrook so that exhaust steam from the vacuum brake ejector could be used to draw the fire. The feature is not expected to be used with 7109 but will be left accessible just in case.
Prototype after machining
I took one of the original chimney units to Richard Nixon to compare the old and new. From the pictures below, it's quite obvious how much extra metal and hence strength is built into the new chimney base.
New and old comparison (1)
New and old comparison (2)
Thus I am happy that it was the right decision to go for the new casting option.

7109's castings arrived in the middle of April 2014.
Nice new pair
They are very substantial and will undoubted last a long, long time. They have been taken to Mendip Steam Restorations Ltd for machining and fabrication into complete dual chimney units.

Again, all the pipework and blast nozzles have to be carefully made to fit together. Hence, the whole job has been passed to MSR as it is beyond the capabilities of equipment available at Midsomer Norton.

Prototype and pattern pictures were kindly supplied by Richard Nixon.

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