Friday, 24 May 2013

Displacement Lubricator No 2

Until recently, I'd been searching for an additional Displacement lubricator to ensure a good oil supply to the steam brake cylinder. The one I already had was earmarked for the Worthington-Simpson Boiler Feed Pump.

As luck would have it, a Cornishman was selling the Worthington-Simpson pump off his traction engine on Ebay. Whilst I didn't need the pump, I noticed in one of the pictures that it had a suitable displacement lubricator on top of it. I enquired as to whether the seller was willing to sell the lubricator on its own and, to cut a long story short, I now have it. (This lubricator, being of the type normally used for a WS pump, will be used for that purpose; the previous one can now be redeployed for steam brake oiling).

When complete, the lubricator is almost identical to the one in the photo below.
Colin Evans's Displacement Lubricator
At first I assumed that there was not much that could be wrong with one of these devices. However, on removing the old viscous oil from it for examination, the central tube was flapping about loosely and obviously not able to perform its function properly. (I've already done a description of how one of these works part way down in 'Why you need a pointy hat' some time ago).

The various bits and pieces are shown below:
Lubricator Internals
Closer examination of the small curved tube shows that its thread has worn over time and, unless screwed in tight, would flap about without making the necessary seal with the valve box.
Tube with its threaded hole in the valve box
Worn thread
Threaded hole to the right in the valve box (or whatever it should be called!)
I cleaned up the tube and thread and screwed them together tightly using Heldite jointing compound to keep them in place.
Reassembled curved tube
So now it should work properly (when reassembled!).

One mystery remains with this lubricator. Most displacement lubricators seem to have a valve for draining condensate to the outside world. This one's drain valve releases the condensate back into the steam and oil connection.
The point of the valve seat is to the right of the bottom of the inlet/outlet hole shown
(same for both valves)
So how does the water get out if there is pressure below? Is it only possible to empty when the system is cold? Or do you just use the drain valve and hope?

Comments welcome!

Wednesday, 22 May 2013

Exhausting Pipes

A little way down my last piping hot article, I'd attached the exhaust steam pipes which rise up between the boiler and cab front. Now it was time to see if they could be linked to the chimneys.
Rising from the depths...
... and up over the edge
Despite the photos showing things neatly fitting together, initially this was not the case. The two insulated pipes look exactly the same; however, when fitted to the pipes below, they are definitely not interchangeable. When there is a 50/50 chance of getting them the right way round, there seems always to be a 100/100 chance of getting them wrong as I did first time!
Second time lucky
The intention of these temporary activities was to check items that we had never seen connected together would actually fit when needed. So far so good.
View from above (1)
(This photo is the right way up, you can tell by the feet!)
View from above (2)
View from above (3)
By now it should be clear that the chimneys do indeed poke out of the top of the cab! As a result, a new cover will be needed to keep the rain out - the gas-man cometh comes to mind!
View from below
The chimneys have now been taken down again. Recently, one of the chimney bases has been repaired by weld-reinforcing the holy parts. So we now have two serviceable chimneys.

As luck would have it, progress on two brand new replacement chimney bases has suddenly leaped forward. So shortly the decision will have to be made as to whether we use the old ones for a year or two and then replace them or wait a little while for the new ones and fit them. I favour the latter.

Tuesday, 21 May 2013

Water Supply (1)

One item that was missing when Sentinel 7109 arrived at Midsomer Norton Station in 2004 was a section of water feed pipework running around the front of the leading engine supplying water to its boiler feed pump.

I decided that the simplest way for me to make this was using mild steel pipe with malleable iron fittings and here it is.
Water feed pipe to front engine's Feed Pump
I concluded that the best method of joining the new pipe to the old and to the pump itself was by using parts from a union fitting. Nominal 1 inch inside diameter unions made by Crane use a 1.5 inch BSP thread for the union join - the same as at either end. Thus I was able to achieve joints without any air pocket. Other methods such as off-the-shelf reducer fittings have a bulge where you don't want it!
Water feed pipe across from left to right
For water systems under pressure, an air pocket is not an issue but where water has to be sucked by the pump from the tank, the air pocket will prevent the suction taking place.
Water feed pipe past the rear engine from
the water tank filter valves
Note: Crane and (I think) Georg Fischer unions use 1.5" BSP joint threads for 1" pipe; others I bought via the internet do not. Beware!

Wednesday, 8 May 2013

Camshaft Surface Finish (1)

In April 2009, I first began investigating Sentinel 7109's engines. The reverser lever was seized so I started tracing the cause (and this is actually why I got so interested in the subject of Sentinels in the first place).

Initially, I found on both engines that the cam followers (the things that actually rub against the camshaft surface and push on the push-rods) were stuck fast as the oil on them had dried over the years and set like varnish.

However, the main problem bothering me was the corrosion at the end of the rear engine's camshaft in the cavity where the cam-selection finger is located.

The following photo shows how it looked in 2009.
Camshaft surface in April 2009
Ironically, I used diesel fuel to remove the corrosion (sad that diesel has to be used to repair steam equipment!).

It now looks a lot tidier as in the photo below.
Camshaft surface in April 2013
The surface was still not very smooth so I made enquiries as to whether this level of roughness was going to be a problem.

I was reassured that, so long as there was nothing standing proud of the surface, then there should be no problem as crankcase oil is so thick that it will be able to protect any pitting from causing trouble.

This was a considerable relief as I had envisaged having to take the whole caboodle apart for re-machining.

To remove anything standing proud of the surface, the easiest way is to turn the engine using compressed air and hold a file (gently!) against the roughness as if using a lathe - a lot easier than taking it all apart!

Monday, 6 May 2013

Pipe Support

After fitting the exhaust pipework between the cab front and boiler front, I was concerned that there was nothing actually supporting the weight of them. Eventually, the pipes would be fixed to the chimney bases but that would not be sufficient to bear the weight - particularly when vibration is taken into account.

I'd never seen a method of support so I had to make it up.
Long studs and cross member
Where I had made and fitted a 'hoop' bracket for the central steam feed pipe, there were two 1/2" BSW mounting holes in the underside of the water tank.

I made two elongated studs threaded with 1/2" BSW at one end and M12 at the other (Metric is cheaper). These were able to fix in place the 'hoop' bracket whilst allowing the cross member's height to be independently varied to suit where the pipes need to be in the cab.

In the picture, I didn't know what height was needed so both lock nuts are below the cross member. I'd planned to have one above and one below but may not have got it quite right. Obviously I did the nuts up a little too tight at one point as the no-longer-nicely-rounded 'hoop' shows!
Related Posts Plugin for WordPress, Blogger...