Wednesday, 20 July 2016

Sentinel 7109 Re-Joyced!

9th July 2016 was a day for celebration as Sentinel 7109 was officially renamed 'Joyce' by visiting Antiques Roadshow expert and railway author Paul Atterbury.

The day began with plenty of boiler pressure but nameplate obscured.
Sentinel 7109 (unnamed) raring to go (Photo Callum Willcox)
Paul Atterbury meeting with Andy Chapman & Nigel Dickinson (Photo Michelle Chapman)
7109 re-Joyced by Paul Atterbury with Nigel Dickinson and Andy Chapman (Photo Bob Edwardes)
Zomerset Zoider put to good use (Photo Michelle Chapman)
I've been asked a number of times - Why 'Joyce'?

A very long time ago, works number 7109 was originally named 'Joyce' after the daughter of Mr Sandeman, the chairman of Croydon Gas Works. In Sentinel circles, many refer to 7109 as 'Joyce' so we decided that we should rededicate her with her original name (re-Joyce!).

At the same time, we also wanted to pay homage to the two Sentinels that worked at Radstock from 1928 until ~1960. In their LMS period from about 1930 until 1948, they were painted black and numbered 7190 and 7191. 'LMS 7109' kept the same idea whilst also keeping the 7109 works number. So Sentinel 7109 now carries the Croydon and Radstock identities in her new guise.
Paul's cab ride out towards Chilcompton (Photo Bob Edwardes)
Midsomer Norton's wonderful signal box with Joyce posing in front (Photo Callum Willcox)
Despite Joyce's diminutive size, she is a lot more powerful than she looks. Draw-bar capability is 19,600 lbs according to Sentinel's marketing literature.
Joyce eases up the hill dwarfed by 70 tons of carriage & brake van (Photo Callum Willcox)
I'm indebted to Callum Willcox for shooting and composing an excellent video recording the day's events. It can be seen on YouTube by clicking here. Don't miss it.
Sentinel 7109 as LMS 7109 - Joyce
Needless to say, a great day was had by all - particularly Joyce!

Next day, the S&D's 08 diesel shunter was detached and 'Joyce' hauled the four afternoon trains...

Wednesday, 13 July 2016

Braided Flexible Hose

Leading up to the March 6th 2016 deadline for the 50th anniversary of the closure of the Somerset and Dorset Railway, I was faced with many outstanding jobs to get Sentinel 7109 in steam for the event. I knew I had eleven or so pipe runs to fabricate for carrying superheated or saturated steam as well as water and oil, all at 275psi boiler pressure.

While I could have kitted myself out with copper pipe tooling, it was going to make the job too lengthy to meet the deadline. I’d been recommended stainless steel braided hose as a possibility and after some internet searching found Guyson’s Kaptech hosing. (www.Guyson.co.uk).
Stainless Steel Braided Hose
After some discussion with Guyson’s technical department, I found that they could make to order in a fairly short time the hoses I wanted with the right lengths and connections to suit the existing fittings on 7109. In addition, each pipe run had to suit the pressure and temperature ratings required.

All hoses would have to withstand 275psi. Superheated steam hose would have to withstand the pressure at up to 380DegC, the max superheated temperature measured by Sentinel in their test department. Saturated steam would be up to 230DegC. Cylinder oil from the mechanical lubricator and water from the feed pump would be at relatively cool temperatures.

I chose all the steam hose to be 3/8” Nominal Bore (NB) annularly corrugated 321 stainless steel lined; the water feed hose to be 1” NB PTFE lined and the cylinder oil feed to be ¼” NB PTFE lined. All would need only the single outer braiding layer.

The maximum pressure and other ratings for the annularly corrugated hose are in the following table (from Guyson):
Stainless Steel Hose Ratings
Thus my 3/8” NB hose with single braiding would take 100 bar (~1500psi) at room temperature.

The pressure derating table for temperature is below.
Pressure derating for temperature
At 380DegC, the pressure rating would still be around 74% of 100bar, i.e. ~1100psi. This is a very high specification indeed with plenty in hand for a Sentinel. The PTFE lined hose was not so highly specified for temperature but not a weakling by any means.
PTFE Lining rating
The ¼” NB cylinder oil hose would thus handle 240 bar (~3600psi) and the 1” water feed hose 55 bar (~825psi).

In order to purchase the various hoses, I prepared a spreadsheet table with the following information (two examples shown).
Information to specify a hose
I sent this to Guyson who responded with their own internal manufacturing version for me to check. After a few iterations, we settled on a final spec for manufacture and I placed the order. It all arrived in a few weeks.

The following photos show how the hose was used.
3/8" hose as part of the blower supply
These short sections of hose were later connected to a ‘T’ piece leading back to the blower valve. Despite ordering a 6” length, I found that the flexible part was much shorter than 6” due to the end fittings. Thus the curve radius had to be tighter than I wanted and the final appearance not ideal.

This was not the only time I found the fitting length getting in the way of a tight bend.
3/8” hose from the feed pump regulating valve
The connection to the feed pump valve required a hex nipple to fit a female hose end fitting. These fittings are a hydraulic type but similar in many ways to the original for copper pipe. Hydraulic fittings generally use a cone seat rather than flat face with copper washer to seal so I had to use a lathe to convert the nipple cone into a flat face.
3/8” elbow fitting at feed pump
Elbow fittings can make life simpler but need to be thought out carefully before ordering. Again I found I needed a parallel thread hex nipple and copper washer to fit the pump. Being superheated steam, I was not happy with a tapered thread fitting here.
3/8” in and out feeds for steam brake valve
The pressure capability of the flexible hose is provided by the outer braiding with an annularly corrugated inside tube providing the flexibility. As such, the failure of flexible hose is down to abrasion of the braiding. Where the hose had to pass through a hole and could chafe the sides, I wrapped silicone fire sleeve (silicone coated glass fibre) around as protection. While the hose can move about, it is now well protected from chafing. For hose such as the steam brake supply, pressure is applied and released. The hose hardly moves with the changes in pressure.
3/8” whistle and pressure gauge feeds, the latter incorporates the loop
For the boiler pressure gauge feed, I was able to wrap the hose into a loop to keep the steam out of the gauge.

The whistle has been supplied by flexible hose too; however, this may be the cause of the whistle seeming to be choked with condensation unless used frequently. Despite using various sizes of orifice to regulate the steam flow rate to the whistle, it always has to ‘clear its throat’ before coming on tune. I suspect that condensation accumulates in the inner tube corrugations with the hose not being lagged so further investigation is required. Suggestions?
1” PTFE water feed hose from feed pump to single check valve
With the pulsing of the Worthington Simpson pump, the 1” PTFE hose moves about quite a bit. I’d be better off with an anti-shock bulb at the pump end to smooth out the pulses.
¼” PTFE hose, 11 feet long section in the cylinder oil feed
The cylinder oil feed takes a tortuous route around the pipe work underneath and then circumvents the boiler. There was an eleven feet gap in the original pipe to the regulator assembly. The ¼” PTFE hose filled this gap very elegantly. I used ‘nutserts’ to attach the hose to the boiler cladding.

In summary, I would say that flexible hose is an elegant alternative to copper tubing; however, there are various factors to be borne in mind.

1. It lacks the authentic appeal of copper piping.
2. It can be ordered ready to fit (provided you get your specification right – not trivial and prone to mistakes).
3. The hose is flexible but cannot twist and can thus be awkward to fit at times.
4. The length of the fittings may get in the way. Consider an elbow fitting if a right angle exit is needed.
5. For short hose lengths, take great care about the minimum bend radius specification.
6. For joins in the flexible hose such as a ‘T’ joint, the standard hydraulic cone fitting can be retained. They work very well between themselves but won’t mate with the original copper washer fittings.
7. Any type and size of fitting can be ordered for any diameter of hose. This could give some pretty bizarre assemblies but technically it is possible.
8. Lengths have to be thought out carefully. It is tempting to think that a bit extra will make life easier. In fact the extra can get in the way and it’s ‘return to factory’ if it needs shortening.
9. Chafing must be prevented. An annual inspection of the braiding should be performed – no different to any other pressure tubing.
10. If vibration is likely, make sure the hose is secured in place as with any other tubing.
11. Stainless steel fittings are the norm. There is little saving to be had with none stainless types.
12. Copper washers are needed for flat face parallel thread fittings (same as with copper tubing fittings). I also used Steamseal to make sure.
13. The PTFE inner lining can kink if twisted.

The entire set of flexible hoses was in the region of £1000. Would I recommend this approach? Certainly!

Wednesday, 11 May 2016

Glandular Replacement(1)

My Glandular Diversion article showed a temporary measure to reduce the water ingress into the crankcases from the engine water pumps. Now the proper job has to be done to stop the water leaking in the first place by renewing the gland packing.

This instrument of torture is used to remove the old packing.
It can probably also pull corks too!
The shaft is flexible and cleverly made so that it does not twist as might be expected. It is screwed into the old packing; the packing can then be pulled out layer by layer, five layers in this case.

The drawing below shows the gland arrangement.
Gland construction
(this is actually an engine piston rod gland but very similar)
First the packing tightening nuts have to be removed. These are conical nuts which are designed to be difficult to over tighten.
Compression fitting released
Then the packing collar is dropped down to show the packing material.
Old packing showing
The torture tool removes a layer at a time.
Two packing layers removed
I was surprised to find that the old packings were made from layers of leather stitched together.
Extracted packing layers
The layers can just about be seen in the enlarged photo below.
Leather goods
Repacking to follow.

Friday, 29 April 2016

Glandular Diversion

My recent article, 'Glandular Fervour', showed the gland packing replacement task ahead. However, prior to that, I had a little idea to temporarily prevent the leaked water ending up in the crankcase.
Grommet
By wiring a grommet around the pump shaft to just the right tightness, hopefully, with the shaft well greased, any leakage should be diverted away from the lower gland and out to the drain.

Fingers crossed!

Post script:
The grommet idea worked quite well particularly when the grommet was well above the lower gland.

Thursday, 28 April 2016

Being a Dipstick

In an August 2013 article, I was left with a mystery. Why did the rear engine require so much less crankcase oil than the front engine to reach the dipstick half-full mark?

At the time, I'd assumed there was something lodged in the rear crankcase but didn't investigate further. Some three years or so later, while preparing to clean out the rear engine's oil sump, the actual reason has become apparent.

Take a look at the following photo with the two dipstick heads highlighted.
A new slant on dipsticks
Although the photo is taken from slightly above the level of the dipstick heads, it is clear that the far one is not only at an angle but considerably lower than the nearer one, about 3" in fact. I'd not taken any notice of this before and assumed that the dipsticks told the truth. When I checked the two dipsticks together, I found they were identical in length and markings. Thus the lower one dipped 3" further into its oil bath registering full rather in advance of actual fullness!

This answers the mystery of the differing oil requirements for each engine. What worries me is how long has it been like this and why are the two engines different?

Of course, the rear engine will have been running with two fewer gallons of crankcase oil than the front one. Hmm...

At some time in the future, the rear dipstick will need fixing. In the meantime, yet another mystery has also been solved.

In this photo, there is a drain cock to let water out of the sump and another highlighted in the top right.
Extra drain cock, top right
I'd wondered what this extra drain cock was for but now I know. Examining the front engine's dipstick for where the oil level would actually be in the sump, it is clear that this drain cock would let out any oil above the full dipstick level. Thus it is an alternative way of checking for sufficient oil without a dipstick.

The rear engine had a blanking plug instead of a drain cock so I swapped the two. The rear engine oil level can now be checked using the drain cock while the front engine's dipstick can still be relied upon.

The mystery has been solved but why the two engines are not identical remains an unknown.
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