Saturday, 13 June 2015

Full Vacuum Ahead!

Strictly this should be Vacuum Braking (14) Implementation (8), however, I needed a more vague heading!

Two new items have appeared on top of Sentinel 7109's cab roof: to the left is Nigel's coffin and to the right is a rather fetching and elegant periscope (respectfully looking away from the coffin!).
A Rail-hearse in the making?
The periscope, in a truncated form, will double as the vacuum ejector's exhaust outlet.
Up Periscope!
And finally, the boiler now has a leg to stand on. In fact, it's the beginnings of the blow-down valve pipework. I'd been checking out the four boiler washout plug holes around the base; one is used for blowing down the accumulating sedimentary detritus.
Caption competition?
The 'leg' showing will be red-band steel pipe to withstand the boiler pressure.

Meanwhile, in Steam Railway magazine (issue 441), there is an article about Sentinel 7109 in its 'In the Works' series. Any content in common with my blog articles is entirely coincidental, of course!

Sunday, 31 May 2015

Vacuum Braking (13) Implementation (7)

Sunday May 31st 2015 has been mainly about the vacuum braking pipework but not entirely.

In my last article, I'd begun to assemble the vacuum ejector pipework. Now I've pretty well completed it as shown below.
Steam supply linked to the Ejector
The main work was either side of the blue pressure reducing valve (PRV).
PRV, condensate drain valve and unions at either end
Both upright ends had to be parallel in order to mate with the union counter parts. (If I've not said before, unions allow the pipework to be taken apart and also enable rotation).

In the above photo, there are unions at each end of the pipe but, in the first photo, the upright larger diameter pipe also has unions allowing it to rotate. In this way, the distance between the PRV and ejector has been made non-critical and hence much easier to assemble.

The next task was to add some support for the vacuum hoses. Previously the 'Swan necks' on the buffer beams had left only a short length of pipe to attach the hose. I'd felt that some extra length was needed in case the hose could lever itself off.
Lengthened 'Swan neck'
The extension was made from a straight pipe coupling and spare male threaded pipe. The threads were sealed with Heldite.
Comparison with usual hose attachment
The extension is still a little short compared to a normal hose fixing. However, if there is a tendency for hoses to come adrift, the extension can be extended further to fix the problem!

Some time ago, I decided that I wanted to take the steam supply for the whistle and pressure gauge from the safety valve assembly instead of the two outlets at the ends of the four-way manifold which feeds the superheater. It saves one expensive isolating valve and make the valve actually reachable by hand!

I thus had to block the manifold outlets. I used a heavy duty steel cap for one end and a coupling and plug for the other (I had the cap already and I couldn't get another off the shelf).

Since these items were round, I was advised that a Stillson wrench was the best way to tighten them despite the likelihood of some surface damage in the process.
Screwing it up!
To ensure a good seal, I made a pair of thick annealed copper washers and applied a liberal amount of Steamseal to make sure.
The cap fits
The Plug fits!
Now to make a hole in the roof for the ejector exhaust.

Saturday, 23 May 2015

Vacuum Braking (12) Implementation (6)

My previous article on the braking pipework finished with a view of the beginnings of work in the cab. To say this involved some unsightly contortionist-like activities is an understatement because the space in which to fit this pipework is bijou to put it mildly. After a day of this, I need a day away to recover!

It also doesn't make it easy to take good photos. I hope the gist is clear from the following ones.

The first is the driver's eye view looking forward.
Avoiding the window and other pipework
I had originally planned to have the train brake handle below the cab's opening on the right. However, there are other bits and pieces reserving space on the side-panel such as the lever for remotely operating the exhaust condensate valve. It would also have meant the pipework passing under the shelf supporting the boiler feed pump where there are other pipes to be installed.

So I concluded that the best route for the pipe was around the top of the circular window aperture with the brake lever much higher up. Top right in the photo are the yellow-coloured silencer/air filter where air is let in to apply the brakes. Then there is the blue-handled brake valve lever itself with the vacuum relief valve just beyond it pointing up at an angle. There is a connection for the vacuum gauge right at the front.

It was not an easy job fitting the pipe around the window particularly the elbow at the top left. The pipes won't bend or give so they have to be exactly the right dimensions to go together! (I got it right on about the third attempt!).

The next photo is looking down to where the vacuum pipe passes through the cab floor (see the last three photos of this link).
Connections to the train pipe,check valve and Ejector
I've put a right angle in between the check valve and the ejector to shorten the length of the steam feed pipe. Hopefully this will reduce the length and weight of suspended pipework.
Ejector's steam feed
The ejector's steam feed is taken from below the left hand safety valve manifold branch (left foreground). It passes through the blue pressure reducing valve to the ejector via a cross (+) fitting which will allow for connecting a condensate drain valve and an ejector-feed pressure gauge. (The pressure reducing valve needs to be set to feed the ejector at its optimum pressure - 60 psi).

Next I have to assemble the safety valve manifold with steam seal and complete the ejector connections. Some extra Stauff clamps are also needed to support the vacuum pipe. Then there is the ejector exhaust pipe which will require a hole in the roof. Hmm, I'd better get that in the right place!

Saturday, 25 April 2015

Vacuum Braking (11) Implementation (5)

Following on from Vacuum Braking (10), it really is true that the whole pipe structure can be dismantled and removed and here it is laid out on Midsomer Norton station's down platform.
Front to rear vacuum pipework
The next job was to replace it all beneath the footplate and frames, then to complete the Stauff clamp fixings and tighten it all up.

The fixings presented another opportunity for the sky drill under the water tank.
Suspended on rails between the rails
The holes were tapped for M6 mounting screws (or, in this case, twice over as the tap tool broke and had to be left buried deep in the water tank metal work. It's covered by the clamp now so nobody will ever know!).
Clamp and hidden holes
Forward-most mounting clamp
Earlier I'd had trouble aligning the hole through the cab floor with the pipework's 'T' junction below. Having started to tighten up the clamps, the situation was beginning to get worse. Previously I'd enlarged the hole to a figure '8' shape; now the hole still did not seem to be long enough but this time I'd run out of space in the cab due to the sanding gear cross-shaft.

My only option was to put a kink in the pipe to realign it.
Joyce's Kink!
Now things were starting to behave themselves and I was able to fix another Stauff clamp and bracket in place to support the pipework from above.
Clamp, bracket and sanding gear cross-shaft (red bar) near the cab front
Finally a quick mock-up of the ejector (aka. jet pump, 'little sucker'), non-return valve and 'T' for the brake operating handle - all connected to the completed pipework below (and Joyce's hidden kink!).
Ejector and non-return valve
Now I'll be able to spend more time in the cab instead of underneath, flat on my back. Having said that, there's a lot more space below. Lonnie Donegan summed it up a few years ago: "There's not mushroom inside"!

Tuesday, 14 April 2015

Vacuum Braking (10) Implementation (4)

In implementation (2), I'd started to plot the vacuum pipework route and had begun mounting it under the footplate. Now I've managed to join it up with the front end and broken up through the cab floor (I'm enjoying this, it's like extreme Meccano but different!).

The first set of photos are looking rearwards (and upwards).

The pipe comes forward around the RHS of the boiler and then dog-legs to get around the RHS rear wheel.
Continuing from the dog-leg with clamp in place
A 'T' provides the upward connection to the cab apparatus.
'T' Junction upwards to cab
(Note: the curtain is not for decoration; it is covering the inter-axle chain to keep me a bit cleaner while under here. I suppose it does add a little to the sense of homeliness in a working environment!).
Up through an interesting hole in the cab floor
After turning left behind the water tank, I had to be very accurate to enable the pipe to fit between the tank and the existing pipework.
Then stitching across to the LHS between the exhaust pipes and the water tank...
...down and round the tank bottom corner and towards the front...
Then once below the water tank bottom surface, the pipe can point forwards again.
...alongside the LHS exhaust pipe...
These photos are looking forwards (and upwards).
...towards the front...
...beneath the water tank and then above the front axle...
...finally dropping down to avoid the counter shaft and
diagonally across to the front vacuum connection
The front vacuum connection
These photos are looking backwards and upwards again.
Diagonal and level then up and over the axle
Up and over the front axle
When the joints have been tightened, the pipe will no longer foul the right hand chain sprocket.
To the rear of the water tank bottom then stitch between the pipes
Meanwhile, in the cab:
The vertical pipe will have the vacuum ejector connected along with the brake operating handle, vacuum gauge and vacuum relief valve.
Where the little sucker connects!
The pipe underneath still has to have its clamps fitted - another opportunity for the sky drill! I'll use fairly shallow holes into the water tank; I wouldn't like to add an extra drain hole!

A few points of note:
There are seven union joint fittings between the front and rear buffer beams. These enable the whole pipe structure to be dismantled and removed. Since I installed from rear to front, dismantling should be done from the front to the rear.

All the pipe's tapered male to parallel female thread connections have been sealed using Heldite. I find this superior by far to Teflon tape as it is easy to brush on and it fills all the gaps. It also does not set hard and allows the joints to be undone at a later date.

I'm not sure I like the diagonal pipe towards the front although it does not seem to be in the way of anything else.

Another day or two should see the underneath vacuum piping completed then the cab apparatus gets its turn. I'm starting to feel quite confident that the end is in sight!
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