Sunday, 5 October 2014

Exhausting Pipes (3)

In 'Exhausting Pipes (2)', I'd just received Sentinel 7109's machined chimney castings from Mendip Steam Restoration Ltd. with 'Interesting Times Ahead'!

I first had to fit the original pipes to the top of the new castings - the key point being that the outer shells' mounting holes also had to line up with the corresponding holes in the pipes. The pipes also had to end up being the same height as the originals.

Luck was on my side. Until this moment, I hadn't realised that the pipes were bored out at the lower end so that there was a lip to support the pipes at the correct height (assuming the new castings were the same height as the originals - which they were!).
Supporting lip at lower end of pipe
I could thus put the pipes in place over the castings (with a lot of assistance from a rubber mallet!).
Pipes on casting (ignore the bolt heads)
Outer shell mounting holes are highlighted
Then, using a couple of metal rods, I was able to support the outer shell in place and adjust the pipe orientation to suit.
Pipes line up with outer shell fixing holes
I marked out the fixing holes in the castings using the holes in the pipes, then drilled and tapped them (M10).
Tapping the castings
That sorted out the pipes but the outer shells were not in very good condition.
Corrosion around an outer shell upper fixing hole
Corrosion around outer shell lower fixing holes
I decided to attach sheets of metal over the corroded sections and weld, bolt or rivet them in place.
Outer shell upper fixing hole repaired
Outer shell lower fixing holes repaired
The sheet metal was 0.8mm thick and thus fairly pliable. To make it follow the curve of the original was a challenge but after a bit of thought I found a ratchet strap could pull it into shape so that I could drill the fixing holes.
Before...
...After(1)
After(2)
So finally, putting it all together, it looks like this (both of them similar). The M10 fixings are all stainless steel for greater resilience in this environment.
Finished (nearly)
Next, there is some fine welding to tidy up a few rough edges and a decent coat of suitable paint. Oh, and hoisting them into place (not trivial!).

Thursday, 11 September 2014

Exhausting Pipes (2)

After some time in the making, the machined new chimney bases have arrived from Mendip Steam Restoration Ltd. It's worth a look back at an earlier article for where these fit atop the boiler.
New Chimney bases, Blast Nozzles & Exhaust Pipes
The photo above shows clearly how the exhaust steam flow divides into two to feed the pairs of blast nozzles.
Four Blast Nozzles showing blower rings
The short pipes showing against the orange pipes are the inlets for the blowers. More details are in this earlier article. Also try the label 'Chimneys' for all the relevant details on the subject.

The main difference between the old and new castings is the weight and hence strength. I used to be able to lift the old ones with difficulty; the new ones required help from a neighbour to get them out of my car! They are simply massive in construction and should last a very long time.

The trouble is that they will be very difficult to fit in place because of the weight! They also need the long chimney tubes to be fitted. Interesting times ahead!

Wednesday, 23 July 2014

In Search of the lost Nutty

'Nutty' is one of a peculiar breed of specialised locomotives that Sentinel made in the 1920s for brickworks use. Their prime requirement was to be very squat in height; very, very squat (5'2" in fact)!
Nutty lookalike - Works number 7243 built in 1928
(Photo from Sentinel Drivers' Club collection)
Built as works number 7701 in 1929 to a 2' 11" gauge, Nutty was one of about five constructed using steam waggon components.

In order to reduce the height as much as possible, the engine was mounted horizontally and the boiler very near to the ground. It also made driving a remarkably intimate experience!
No room for foot-plate passengers!
(Photo from SDC collection)
Neither of the above photos are actually Nutty; however, the next one certainly is.
Nutty in August 1971 at the Welshpool & Llanfair Light Railway
(Photo SDC collection)
The inner workings are clearly visible if you click to enlarge the picture.

I became aware of Nutty through conversations with curators of the Narrow Gauge Railway Museum in Tywyn, Gwynedd, at the terminus of the Talyllyn Railway (where I can be found volunteering on occasions). Nutty is actually owned by the NGRM but it never seems to be found anywhere near the museum!

Although originally built to a gauge of 2'11", it was re-gauged to 2'6" some years ago and it ran on the Welshpool and Llanfair Light Railway for a while. Since that time, I do not know exactly where it has been but I'm led to believe it has spent time at Railworld in Peterborough. In 2012, it made its way to the Leyton Buzzard Railway where it is on display at the Stonehenge Works station.

I visited the LBR on Wednesday 16th July 2014 and was made very welcome indeed. I wanted to poke my digital camera into Nutty's various nooks and crannies to assess its general state. I now have around 170 photos, not all are included here!
Nutty under cover at Stonehenge Works
Yes, it is chain-driven!
Side-on view
Cab internals showing the boiler
'Under the bonnet' view showing the engine beneath the water tank
Engine, water tank and boiler feed pump
Bijou accommodation for the driver!
There are clearly a number of components missing and regrettably I omitted to enquire if they existed. However, it was a good day out and many queries answered as to the construction of this strange locomotive.

Now who volunteers to restore Nutty, reduce the gauge by another 3" and run it on the Talyllyn railway?


See my Reference Material page for information sources.

Sunday, 22 June 2014

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.

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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