Wednesday, 21 February 2018

Exploring New Territory

1st Steam Loco on this part of the S&D in over 50 years.
My apologies for being quiet for so long; it's been a very busy time hauling Christmas specials in December and doing annual repairs, maintenance and some enhancements this year. Rest assured that there will be more to follow.

In the meantime, here's a video clip of Joyce exploring some new territory at Midsomer Norton after passing her annual boiler inspection on February 20th.

Wednesday, 11 October 2017

Not Butting Pony Tails

Following on from my brief R&D activity to prevent Gland packing turning into a pony tail, I bought a 35mm diameter wooden dowel from B&Q. The gods must have been on my side - how often can you go to a DIY store and actually buy what you want in exactly the right size? 35mm is the same diameter as Sentinel 7109's piston rod.

Wood is a good material for winding the packing around as it grips the packing surface just the right amount without abrasion. I first drew a line along the dowel so I could see the angle of rotation. Then I pinned the end of the packing to the dowel.

I rotated the dowel to pull the packing rope around the dowel and pinned each turn either side of the line to allow me to cut one ring at a time without the remaining packing unwinding.

One end of the dowel was held in a vice to make it easier to hammer in the pins.
Packing rolled on to the dowel
Along the line drawn on the dowel, I painted some Heldite around the outer surface and sides of the packing (but not the inside surface).
Packing pinned in place
I took the dowel and its turns of packing to site for fitting into Joyce's rear left piston rod stuffing box. By taking it on the dowel, I was able to cut one packing ring at a time and fit it straight away (soaked in warm cylinder oil). This minimised the time the packing might have to become a pair of pony tail ends and it proved very effective.

Next task is to light the fire and blow out the two old right hand piston gland packings and run-in this one.

Sunday, 1 October 2017

Butting Pony Tails

Recently, I wrote about Sentinel 7109's piston rod gland packing challenges but didn't have a photo to illustrate. Also I've now found a way to reduce the challenge to a reasonable level.

The photo below shows an experimental sample of the Pilotpack 4010 1/2" square section material.
Pilotpack 4010
To the right is the 'pony tail' created by cutting the 4010 without any means of holding the fibres together. (It is not quite this bad in practice but it does emphasise what happens if the end is left to its own devices). Butting this against another such end is not easy!

At the left hand end, I'd painted some Heldite around the outer surface and sides of the of the 4010 at the cutting point. To avoid any risking of the 4010 sticking to the rod, I left the inside rubbing surface clean.

I considered Heldite as opposed to Evo-stik because it is good at withstanding high temperatures and oil (used to assist pushing it home in the stuffing box). Although it takes a while to dry, it soaks into the 4010 like a glue and holds the fibres together.

As the photo shows, at the left end where the 4010 has been cut, the Heldite seems have held the fibres together effectively. Now to do it for real...

Sunday, 27 August 2017

A Nut Case

Sentinel clearly built their engines to be mounted horizontally. This I found to my expletive cost while examining piston rod steam glands.

What do you think this is for?
Pipe Dream
There's clue in the orientation of the photo.

There's another clue in this photo showing the upper gland tightening nuts removed and not in sight.
Nuts not tight and out of sight
If you have a horizontal engine, the gland space looks like this:
Nuts still not tight and out of sight
In the horizontal engine, if you remove the gland nuts, the nuts fall to the bottom and you can pick them out with your fingers.

In the vertical engine, the nuts tend to fall in behind the lower gland where your fingers really cannot get. A magnet on the end of a telescopic stick also cannot get there; neither can a magnet dangling on the end of a length of wire (because it sticks to everything else before it gets anywhere near the fallen nuts).

So the top photo has the answer. The copper pipe has a cylindrical magnet clamped in the short end that can be fed in behind the lower gland without sticking to the sides. As a result, it can get to the out-of-reach nuts which inevitably hide in the most awkward corners.

Unless you can stop the nuts falling in behind the glands (some hope), this is the tool for any budding gland worker with a vertical Sentinel engine.

Saturday, 19 August 2017

Operating Experience (3) Has Beans?

Sentinel 7109 has been back in operation for over a year. At first, it was a matter of getting Joyce working; now I'm becoming aware of oddities that aren't working quite as well as they should.

One of these is a jet of steam below the front engine when working hard uphill. This indicates steam leaking through a piston rod gland in the front engine.
Arrowed jet of steam (Photo: Sean Dudden)
Looking underneath, there are four copper drain pipes pointing downwards immediately to the rear of the front engine.
Four drain pipes
In the photo above, the left end one drains leaks from the front engine's water pump; the second and fourth ones are drains for the four automatic cylinder drain cocks; the third one drains the two piston rod glands. This third one has been getting hot at its tip whereas the others just look a bit oily.

Having been aware of this leak for some time, I made preparations for repacking the left hand steam gland of the front engine. I needed to order the packing material but did not know the size so I loosened the nuts holding the gland packing in place to enable me to gain access to measure the size of the gap to be filled. I was not prepared for what I found.
Look closely at the dead centre of the photo. Instead of old packing, I found what looked like a bunch of dark grey baked beans! These I removed for examination.
Beans, Beans
The beans looked to be rolled graphite, the remains of the original packing. It is possible to write with them, hence graphite.

Clearly, I couldn't simply put them back to be ready for the next public steaming, six days away.

Sentinel used to produce packing rings with a part number for ordering. This luxury is not available nowadays so I had to find a current substitute. Stuart Gray (Heritage Steam Supplies (HSS)) advised me that the material needed was Pilotpack 4010.
Empty packing space (rough piston rod surface)
I found it very difficult to measure the distance between the piston rod and the surface of the packing space, known as a stuffing box. However, there is a gland bush which holds the packing in place. This is a close fit in the stuffing box so I measured the thickness of the bush instead.

It measured almost exactly 1/2". Thus 1/2" x 1/2" square section Pilotpack 4010 was what was required. About a yard is required to make the five rings of packing for a 1.35" diameter piston rod.

HSS were out of stock so I had to go directly to the manufacturer, Beldam Crossley, to get it in time. Beldams were more than helpful and sent me eight metres of 4010 next day. Beldams were cheaper than HSS but I had to order eight times as much as was needed immediately. (There are four piston rods in all so it's not that excessive!).

Following instructions provided by HSS, I prepared the required five rings by wrapping and clamping the length of 4010 around a mandrel (piece of plastic pipe the same diameter as the piston rod) then cutting to make each ring using a Stanley knife. The instructions say that each ring should be inserted into the stuffing box so that the ends 'butt' together. Clearly the writer of the instructions has not worked with 4010 as, when cut, the ends splay out like a pony tail. Butting pony tails is not really what is required but for this attempt that is exactly what I had to do.

For the initial attempt at fitting, I could only get four rings into the stuffing box.
Four rings fitted (they were soaked in SCO1000CTRO+ cylinder oil)
I screwed the clamping nuts tight to push the packing home and then slackened them off a turn or so to leave the packing uncompressed. As the piston rod surface is pitted, over-tightening the packing will just lead to it being abraded and failing.

There is some steam leakage as a result but it is better than the stuffing box being left full of beans again!

After the first day running with the new packing, the four rings had survived but were more compacted than when fitted. A gap was thus left so I could fit the fifth ring. Again, I tightened the nuts to push the packing home and then slackened them off a turn or so. Some tweaking will be needed during the next steaming.
Five rings fitted
Working on the packing is not easy physically with everything in situ. However, erecting a seat did make things a little easier.
'In sit you'
Only three more steam glands to go, the right front one could still be guilty...
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