Nut & Bolt - Big Time! (2)

A few months ago, I described the manufacture of a new nut and bolt to operate Sentinel 7109's handbrake. Today I fitted it into place.

Linkage from nut to crank(1)

Linkage from nut to crank(2)

Some large split pins are still needed to complete the job. The largest I had are 1/4" diameter. 3/8" are needed. These things are big!

Optimism!

The brakes will have to be adjusted after the drive chains have been fitted but they do at least operate from the handle. The roller bearing under the handle seems to work satisfactorily.

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.

Pipe Reality Come True

My previous main steam pipe article was at the stage of it being persuaded into a shape that should fit. In practice, it wasn't that easy.

The first challenge was that, being such an awkward shape, it would have been easy for Sentinel to make it fit with 7109, the pipe and all tooling collocated in the factory. With the pipe being made five miles from 7109, it could only be made to approximately the right shape using a jig made using the old pipe geometry. Mendip Steam's Andy Melrose eventually gave in that some heat was going to be needed in the cab to make it fit. Thus 7109 had her first fire lit since 1968!

First fire in 46 years

Not much steam was created but it did seemingly allow the pipe to ease into place, or so we thought.

Everything was fine until the second challenge. The nice new end pieces were made to drawing size but that did not mean to say that the original mating joints were made that way.

Nice new end fitting exactly to drawing size

The mating end under the water tank had at one time been repaired and the hole into which the new pipe had to fit was not actually round! The two parts would not fit together.

There was nothing for it but to grovel about underneath with a miniature grinder (it's not made for a human to squeeze under the water tank) and make the mating hole bigger, not a lot of fun!

The underneath end finally in place

The fitting in detail...

...fed by a pipe around the firebox...

...fed from up here in the cab...

...from the regulator all the way up here!

So the pipe is at last in place. The white insulation is made from glass fibre ladder tape wound over partly dry, tacky red oxide paint to keep it in place. Finally the ends and a centre join are secured in place with galvanised wire.

Glass fibre ladder tape

The pipe joints are sealed using 3mm thick annealed copper washers, made from copper sheet, with lashings of SteamSeal. The copper washers were made by cutting the outer perimeter with a hole saw and the inner hole with a screw tightened hole punch. Glad I wasn't in a hurry for these, it took ages.