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Sir Percivale, 3.5” gauge Maunsell King Arthur


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Station Road Steam have had some locos from the late Ian Jaycroft for sale over the last few months. One of these has been a substantially complete King Arthur. 
https://www.stationroadsteam.com/3-12-inch-gauge-southern-railway-king-arthur-4-6-0-stock-code-9711/

I have recently purchased this and it will hopefully end up looking like this:

B465677E-EA8D-4AA3-9062-0D877C946362.jpe
The loco will be called ‘Sir Percivale’ No 772. (My previous loco, an A3, ‘Hyperion’ has been sold on.)
2B904166-CF61-4429-9D80-C6037AF149BA.jpe

 

Ian Jaycroft incorporated some amazing engineering into the KA; not least a Wakefield pattern lubricator for feeding the internal bearings (KAs didn’t have these, but I’m willing to overlook that, for the practicality of it).

307B166F-783E-459D-8511-976A7A624A1C.jpe


495A9CE5-FADD-448C-8F78-1EAD363597FA.jpe

The quality of the engineering is outstanding.
73F9C515-A335-43CE-B643-00B5B3ED630D.jpe141EF53D-4E52-47B2-A8E9-F77D19849AEA.jpehttps://youtube.com/shorts/3o1bEEMdJ7s?feature=share

The video shows the drain cock mechanism at work.

 

I’ve been working on the front end of Sir Percivale today. The KAs were handsome engines when first built, especially the NBL locos: these had smooth lines and very few rivets at the front end.  Once smoke deflectors started to be fitted so did hundreds of rivets!
7D37F7AB-0BA2-4C54-8158-8FBBCD2F8C6C.jpe
I’m not sure whether Ian intended to do further work on the KA smokebox, but it wasn’t quite right - looking a bit like a Hughes L&Y engine. 
12CFD31D-F7CA-45CE-8D35-AE9385E8DCCD.jpe
A morning’s work on the lathe has made some modifications. 
A84F4226-77D1-42E8-9759-12C4A8C793D5.jpe
It’s quite tempting to make the rings more prominent, similar to the MR Deeley doors, but these Maunsell smoke box fronts are rather more subtle. I suspect that the very small inner ring is used to seal the door and it helps to visually thicken it up.
The bottom front plate of the smoke box has many surplus holes in it which will be covered by a sheet of N/S, complete with smokebox step. There are a further two steps to be made also. 

Main priority now will be to get the boiler shell tested. 


Tim

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  • CF MRC changed the title to Sir Percivale, 3.5” gauge Maunsell King Arthur
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Christmas came early for me, with a successful boiler shell test for Sir Percivale.
3DC27597-7586-4DCB-BF24-253CE3D4ED2F.jpe
It wasn’t quite straightforward as there was one internal stay that was weeping under 2x pressure and, needless to say, access was a bit tricky being slightly behind the convexity of the firebox. The original silver solder had inadequately penetrated on the far side of the stay. A couple of hours trying to swage it using a specially made tool, simply rounded off the top. The area was cleaned up using a brand-new, but 50 year-old dental handpiece powered by my equally ancient dental engine, complete with a nasty large inverted cone bur. A front-surfaced mirror, headlight and loupes aided vision. 
ABDD3A58-EBD2-45B4-8332-9EF04E0F4EEC.jpe
The whole boiler was then gently heated up on a hearth of firebricks and the gas flame concentrated on the outside of the offending stay. Once up to temperature the solder flashed nicely into the joint with plenty of flux, following the heat.
3602F497-6648-4871-88C4-9D02C9F95326.jpe
I have learnt a lot from this little exercise, with very useful advice from my friends in the North London Society of Model Engineers.

Tim

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I have started to work on the rear end of Sir Percivale (so to speak) and dismantled the RHS injector. This is more complete than the LHS, including the steam cone. D9B3E5D1-E48D-426F-91AA-68926D6178BB.jpeAs for the LHS, there is a delivery cone, seen here with a view from the top.1674DD00-2ADF-40D1-B52A-C7EEC19C774A.jpe

There is clearly the central combining cone missing, whilst the relative positions of the other cones can be seen in this ventral view. F5F8BCF1-E2AC-40B8-A232-6FDB00FFD574.jpe

The steam cone finishes ahead of the water inlet opening  (there is a fine spacing washer next to the mating surface with the injector body) whilst the bell opening of the delivery cone can be seen ahead of the overflow.


It would be good to get one of the Ian Jaycroft injectors  working. It will need the combining cone reverse engineering and a ball and plug for the valve on top.
 

The questions then arising, are:

Any idea how to calculate what overall length / taper proportions the combining cone should have?
How would the combining cone be stabilised in the middle of the injector body?

What size ball for the valve - the hole is 3/32” diameter?
How much lift?


Maybe I’m expecting a bit much of this: I will definitely use a small Chiverton injector on the other side, when I can source one.

Tim

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Currently settling in the boiler: but these Kelloggs cornflakes boilers will probably not catch on.

2A92B417-9181-4F7B-BBAE-389F7D9C3360.jpe

I have also been working out the plumbing and fittings at the back head: just loosely in place at present.

FAD2B0C1-967C-418C-9562-44319934F32D.jpe

Trying to work out what goes where is quite tricky, but it’s all beginning to make sense.

EB53EC75-4081-4C4C-B0EA-F26A82214BF4.jpe

 

Tim

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I have fettled the boiler cladding into place this morning. I don’t think that has been done before, as it was catching on the firebox retaining slides. The boiler bands will pull the tapered front sheet into shape.

64504726-2FF9-4F68-AD0A-C24CEC60EDF7.jpe

As one would expect, there is a beautifully finished corner beading for the firebox in the cab. Again this needed quite a bit of trimming, but will be a good basis for the false back head that I will make.

1AD39123-5CD6-4D20-890B-F17193ACDDA3.jpe

 

Tim

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The loco obviously splits into major components which can be sprayed individually. I’m not sure about the boiler: it might be best to take it out for painting with the cladding on: it could then be rotated as it is painted. I would imagine that painting the cladding and then fitting it to the boiler would almost certainly end up damaging the paintwork. The boiler is a good ‘plug fit’ in the smoke box and is removed easily from the frames. The cab spectacle plate is currently far too tight a fit on the cladding and will need easing. There are numerous components that will need to be removed and re-fitted around the cab. 
 

I have a small Kite spray gun and used it to re spray the previous A3, Hyperion, and of course the 4” Showman’s RL, Frederick. Lining out will be done directly with a lining pen. 
 

Tim

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33 minutes ago, CF MRC said:

The loco obviously splits into major components which can be sprayed individually.

 

It may be obvious to you Tim, but with all those complicated pipes and fittings, seemingly permanently fixed, it looked like it might be awkward.

 

It's certainly interesting to get a view of a totally different aspect of railway modelling.

 

Guten Rutsch! (as they say over here),

David

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I have been trial fitting the cab sides & spectacle plate. 
CEDE7042-764E-45FC-8E6E-CF76EFE5C7C4.jpe

I will have to roll the cab roof, which will be made of steel. For ease of driving, part of the roof will need to be removable. The fixed front section might go as far as the rear of the firebox. The removable section will be retained by a row of rare earth magnets let into the brass. However, I am a bit concerned that the rear ends of the cab roof will be quite vulnerable as they are unsupported. Tying them together with a cross bar might defeat the object of a removable cab roof, but there is a prototypical bar in that area.
 

Any thoughts?

 

Tim

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Just like Goldilocks. The first cab stanchion was too thin at the top. The second one two thin at the bottom. The third, just right! (Only 0.1mm difference between them.)

 

1C7F6F48-8654-4F6B-A2E2-3395E2E40B6D.jpe

 

Tim

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I returned to the front end yesterday. The smokebox door dogs were originally rectangular in shape whereas they should be more trapezoid in shape. 

5F03EB59-FDE0-4BF3-B490-7EC37C17CB03.jpe

The fixing bolts are 10BA with 12BA heads. Two are long enough with a decent shoulder, but four are too short, so it’s not a matter of if they’re lost but when. I have some 12BA steel hex stock of the right size on order so that will rectify that problem. I can’t think of any clever way to make the bolts captive…

The hinge support base also needs re-engineering, but again currently waiting for a tap & due set. 

The straps themselves are not quite the right shape on the ends, so I will punch out the copper rivets, remove the straps, refinish the ends and polish the steel - but use steel bolts / rivets to re-fix them. 

 

Tim

 

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The straps have now been screwed / riveted with steel bolts, the ends curved and the finish improved. 

401DDFA5-A0D9-428D-A1A1-EF37F79CA7B1.jpe

I have also modified a couple of the (longer) bolt heads with a representation of the nut and bolt. I think the use of a long shouldered bolt will suffice, with this minor visual modification. The two brass handrail knobs will need to be replaced with steel, as these will be in a bright finish. 

 

Tim

 

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Following from yesterday’s post I have now re-made the front handrail and stanchions on Sir Percivale. The handrail is straight (it’s pivot steel) and slightly longer, whilst the stanchions are more understated.

AF6B3D33-83B9-49E1-B03C-A7198D105724.jpe

3D3A3C88-629B-4781-A36F-D19BEB2E42FB.jpe

2483BEE3-9FB5-4621-840A-391B237316D4.jpe

 

They’re about right now. 

 

Tim

 

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I had a very productive day in the garret (small scale) workshop yesterday, but worked far too late into the night. The spectacle plate on Sir Percivale was made from relatively thin brass and so wasn’t very rigid. 
A9ECF87D-1FA9-40FA-86B1-A828550EB135.jpe
As suggested by a clever chap on another forum, I therefore soldered together two pieces of 4mm right angle brass section and bent them into the correct curve between fingers and thumbs: Yuri Geller eat your heart out!
4290C572-926A-44F8-AE0F-58D1A1A75BCB.jpe
These were tinned, 12BA-bolted together with the spectacle plate and soldered to the top with a whiff of heat from a blow torch. 
8BD91029-84EC-458A-8D05-8D84B93BC137.jpe
The whole front end is much more sturdy now. The next job will be to roll the roof from steel with the front section bolted to the T section with probably a string of 16BA bolts. The rear section will be removable for hand access to the controls. 

Tim

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It is very satisfying when you have the correct instrument for the job. The flexibility of my John Stevens watchmakers mill / drill really is invaluable for this sort of work: drilling 1mm diameter for 12BA. 

5A0565E7-01A6-4A1A-A957-0DC866462456.jpe

The front of the cab roof is held in place with 3x 12BA and 2x 10BA bolts. The 12BA are countersunk and blackened so should hide quite well behind the rain strip. This bit of roof has to be removable when required for maintenance, the rear portion will slide in and out for driving. 

C254BAD1-1FC7-48E7-A228-63B68F250A1C.jpe

The roof has a passive fit and so fixings can be quite minimal (no need for multiple 16BAs) 

 

Tim

 

 

 

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The cab roof on Sir Percivale has made some progress over the last two days. It is held by a tab at the front and the rear beam, as well as some 2mm diameter 1mm thick rare earth magnets. I may add a few more as they work quite well. The fit will improve when the rear beam is soft soldered to the roof and stiffens the corners where it engages.

1BE54BA1-3DB4-4FE2-9F0C-D8017027B454.jpe

 

FD63FB8F-E05D-48CB-9234-57DB45A001F8.jpe

 

The rear section slides out and is held by the magnets whilst doing so. 

B64E66CC-238E-426F-9DAA-DEA03AF1DEDD.jpe

 

The rear beam has some brass brackets silver soldered to it to allow it to be bolted to the roof. I’ll soft solder it on when I’ve made the rain strips. I have some brass right angle strip but I think it’s too small. 

3AECD098-FE16-4CD0-8BD0-F28A019023F8.jpe

It begins to look like a Maunsell cab now and should transform the appearance of the engine when re-assembled.

 

Tim

 

 

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