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Member postings for julian atkins

Here is a list of all the postings julian atkins has made in our forums. Click on a thread name to jump to the thread.

Thread: CMKeiller Boiler tubes
21/11/2017 23:48:30

Hi Duncan,

I think you need to consider the SMEE Journals. C M Keiller was a SMEE member.

He provided his formula to Martin Evans when Evans was writing his book on boiler making in the 1960s.

Jim Ewins had his own views which were also published in the SMEE journals and also the Maidstone MES newsletters which have been archived. They are also in Evans' book.

The fullsize formula is in Jos Koopmans' book 'The fire burns much brighter' available from Camden.

I have always used generous tube diameters via length for both ordinary flues and superheater flues.

Cheers,

Julian

Thread: Valve gear design
10/11/2017 21:30:07

Hi John,

There are a significant number of designs where Martin Evans made a hash of the Stephensons valve gear (and also Walschaerts). Don Young always made a number of errors on his Stephensons valve gear when using loco links as he drew the gear out incorrectly and didn't understand what he was doing. Keith Wilson was ok doing the classic Churchward GWR arrangement of Willie Pearce's gear for Stephensons which is less indifferent to scaling down, but when Keith tried other arrangements he was seriously out of his depth. I dont think that Keith ever understood valve gears properly.

LBSC made serious mistakes on all his 5"g valve gear designs except his Joy valve gear Minx and Maid of Kent.

What we know now thanks to H S Gowan and Don Ashton really only was made public from circa 1974/5 onwards.

Don't worry. What you decide to do can easily be checked on a valve gear simulator program these days before you cut metal.

I have been involved in re-designing a number of well known ME loco valve gears in recent years for various builders. John Baguley has done the same. The understanding of the niceties of Stephensons valve gear is a fascinating topic and can become an obsession. If correctly applied and understood the superlative performance on the track is well worth the time and study involved.

Cheers,

Julian

10/11/2017 19:06:01

Hi John,

We briefly discussed this earlier this year on one of your other threads.

I think the simple answer is no, you cannot scale down the fullsize Stephensons valve gear but this must be qualified as it depends on the loco and arrangement of Stephensons and much else besides.

One of the classic 'cock ups' was Keith Wilson's 5"g 'Bulldog/Dukedog' valve gear - which is also relevant because it is pretty much the same arrangement you wish to copy. Direct drive Stephensons with loco links and slide valves below the inside cylinders. No way does the gear produce enough travel for the valve events required.

So unless you are vary careful and are aware of the pitfalls you could end up in the same mess Keith Wilson landed himself in.

Neil is absolutely correct that miniature locos require or ought to have greater travel of the valve than what would be scaled down from fullsize.

You start with the cylinder block and what width the steam ports and exhaust ports will be. (Only the width of the steam port is relevant for valve travel). Then how much lap do you want on the valve? Then in fullgear (say 78 or 79% cut off for a 2 cylinder loco) you can calculate the required valve travel required.

Then you have to consider the type of expansion link employed (launch type or loco links) and within reason you can predict the eccentric throw required.

Note with slide valves (outside admission) loco links are preferred with direct drive, and launch type links with indirect drive. In each case there will be a small suspension offset and a small amount of die block slip so the eccentric throw need only be a tad more than calculated.

If you have loco links with indirect drive, or launch type links with direct drive (for outside admission/slide valve) the suspension offset will be considerable to achieve equality of valve events and there will be considerable die block slip which also requires a greater eccentric throw and larger expansion link to compensate/accomodate the excessive die block slip.

Note Martin Evans used direct drive and launch links on Princess of Wales with slide valves and specified a totally inadequate amount of suspension offset.

Fowlers Fury mentioned LBSC's Pansy. I can state quite categorically that Pansy has a very poor version of Stephensons gear, but can easily be rectified.

John, you also have to consider the expansion link suspension and whether centrally suspended or suspended by the top of the link if loco links.

Anyway the first thing is to decide on the cylinder block and whether for a 5"g loco the size of Super Claud you have say 5/32" or 3/16" steam port width.

Cheers,

Julian

Thread: Suggestions for a locomotive
02/11/2017 09:53:32

Hi Jon,

If you are interested in a narrow gauge loco...

Conway is a freelance design by Martin Evans. For a little bit more effort you could build a copy of the Hunslet 'Quarry' design. Don Young did a 3.5"g version called Hunslette. Far superior to Conway IMHO. Hunslette also has balanced slide valves (optional) which give a very free exhaust.

From memory there is a problem with Conway's valve gear as it uses launch type links with direct drive.

In the case of both Conway and Hunslette (and Juliet) the wheels can be turned from steel blanks which also provides extra adhesion compared to ordinary cast iron wheels.

Personally I would go for gunmetal cylinders despite the extra cost - though in 3.5"g you may not have a choice anyway.

Cheers,

Julian

Thread: How to square a piece of stock metal
01/11/2017 22:51:39

Hi Jared,

A long straight edge, vice, set square, and files and some decent light.

I have never milled any loco frames, though some have been of quite complicated shapes plus all the cut outs in the frames and lightening holes/openings, plus of course the openings for the horncheeks which must be done very accurately.

I rivet the 2 frames together before commencing any of this .

When I use the long straight edge (for many years a long builders level owned by my Dad), chalk marks were put on the frames that needed attention.

Cheers,

Julian

Thread: Suggestions for a locomotive
30/10/2017 23:52:25

Hi Phil,

Thanks for that link! I had quite forgotten about it!

I would add as an aside that after constructing my own Railmotor I later re-built Don Young's original Railmotor for it's new owner after Don's death. I lifted it out (on my own) from the boot of my old Vauxhall Chevette Saloon circa 1996 to display at an IMWES monthly meeting.

The following day my back completely seized up and required treatment. I have suffered from back problems ever since.

So I would not suggest a 5"g Railmotor is a one person lift.

I think the HSE guidance is 25kg for lifting and 15kg for carrying or perhaps it is the otherway round.

In any event all 5"g locos are over 25kg, and most 3.5"g locos too.

I cannot lift my own unfinished 5"g Stepney (my own version of a 5"g Terrier ala Martin Evans' Boxhill) unless the boiler is off the chassis.

If lifting a loco is a consideration then 2 persons for the lift are required.

Jon - I don't think I would want to attempt to build a miniature loco on an old Myford ML4, but in the 40s and 50s many did!

I think a 3.5"g LBSC Juliet should suit your bill with full valve gear. I would regard this as a much better proposition than 'Tich' if you plan to run it. The construction series is in ME and all castings etc are available and the boiler is a piece of cake to make yourself.

Cheers,

Julian

Edited By julian atkins on 30/10/2017 23:54:41

Thread: First steaming of my Springbok
29/10/2017 23:49:31

Hi Simon,

You have done extremely well there and I very much enjoyed watching the youtube clip.

There have been many Springboks built to Martin Evans' 5"g design, which was a very early design of his circa 1960, and you deserve considerable praise for having noticed fundamental errors in the design/drawings and resolving them.

I remember one particular Springbok built by the late John deBank of the IWMES on it's first few steamings on the track and it seized up solid.

On the other hand I remember driving Alan Killick's Springbok at Beech Hurst (SMLS) and you could drive it on the reverser with an open regulator - a rare treat. Alan's example was not built to the drawings I gathered!

With a Jos Koopmans draughting and Don Ashton input into the valve gear you have something quite special there plus your excellent workmanship!

Cheers,

Julian

Thread: John Stevenson
20/10/2017 01:08:56

I am grateful to Ketan's post.

I have crossed swords with John on many occasions in quite forthright PMs and on here on occasions.

All good wishes and prayers.

Cheers,

Julian

Thread: Clarkson 5" Stirling Single
13/10/2017 22:31:58

The OP is referring to the Clarkson drawings not anything else!

My 3.5"g GWR King is built to Jackson/Clarkson drawings. The drawings are very difficult and a great deal of knowledge of the fullsize locos is required to interpret same.

I think any Clarkson drawings are really only for the experienced model engineer with a detailed knowledge of the fullsize loco in question.

Not sure if this helps.

Cheers,

Julian

Thread: Firebox Side Stay and Boiler Bush Material
12/10/2017 20:41:47

Hi Howard,

There is some disagreement over the following but for boiler bushes such as dome and regulator bushes (large bushes) , and for that matter any smaller bushes, do not use leaded phos bronze. Although some suppliers state their leaded phos bronze is ok to silver solder (eg Colphos) silver soldering a boiler involves long heat ups, and I have heard of all sorts of disaster stories of leaded phos bronze bushes. I have never used leaded bronze and to avoid any confusion have never acquired any.

I have also never used gunmetal castings for bushes.

If you go to a dedicated non ferrous supplier they will cut you off accurate slices of cored phos bronze which saves an enormous amount of machining and cost. I have used C Rees of Cardiff for the last 16 years (which is local to me and I can pop in and select what I want from the racks and shelving) usual disclaimer.

Cheers,

Julian

Thread: 5" gauge loco
08/10/2017 10:07:30

Hi Peter,

Generally wheel balancing on a 5"g loco is ignored. If your wheel castings have balance weights cast on them leave them as that.

The Metro boiler is a smallish 5"g boiler though the belpaire firebox makes it more complicated. There is no reason why it should not be built single handed.

Cheers,

Julian

07/10/2017 20:50:13

Hi Peter,

The crank pin on the wheel should be 180 degrees out of phase to the position of the crank axle pin nearest that wheel.

(If the on the same phase you have what is known as Stroudley balancing which is quite rare and in fullsize required excessive balance weights on the wheels).

Cheers,

Julian

Thread: Question about clock dial
01/10/2017 23:43:04

I have restored a number of English dials.

I dont think your original is beyond hope or needs replacement. To retain the original dial restored would be the ultimate aim I would suggest.

I dont think this is very difficult.

You just have to understand how these dials were made originally.

Cheers,

Julian

Thread: LMS 2F Experiences
21/09/2017 22:14:19

Hi Bryan,

I doubt the boiler would be built to the original design as it was seriously flawed and quickly altered.

Externally and superficially it is a nice compact loco.

But it is an old design by a long forgotten model engineer, and the construction series was not a great success.

GLR/Kennions continue to market it because it shares the same castings as their 'Butch'.

If the loco you intend to purchase is 'in ticket' then have a drive of same before purchase. Or else get someone experienced to have a drive while you watch on behind on the driving trolley.

If it doesnt have a current boiler ticket and paper trail of previous tickets then that opens a different can of worms.

Cheers,

Julian

21/09/2017 20:00:25

Hi Bryan,

Designed by Jack Austen Walton from the late 1940s over a very extended period described in ME. The boiler designed by Jack was a very poor dangerous design. Lots of features departed from LBSC standards just for the sake of it apparently, and you have already noted the problem with the grate and ashpan over the rear axle.

If made to drawings (the boiler design was quickly altered) I would give it a miss. If the builder has made substantial improvements then it might be worth a punt.

The Kennions/GLR 'Butch' is very very similar and there is one in my workshop at the moment for repair and is perhaps the most badly designed miniature loco I have ever encountered.

I have seen lots of 'Twin Sisters' over the years on display but never one running. I dont ever recall the design being held in high regard.

I have always taken the view that what is in essence a shunting loco is unsuitable for passenger hauling in miniature simply due to the boiler proportions (small grate area) and you end up having to force the firebed resulting in clinkering etc.

Just my personal opinion of course.

Cheers,

Julian

Thread: BR Std vacuum ejector exhaust
09/09/2017 22:03:37

Hi Howard,

If the ejector pipe went just into the smokebox it would destroy the smokebox vacuum.

It must go up the chimney without affecting the smokebox vacuum or the smokebox draughting and as Bob states there are various ways to achieve this.

It would be interesting to know whether your loco is the double chimney or single chimney type that Bob hints at.

The double chimney type is far better.

Cheers,

Julian

Edited By julian atkins on 09/09/2017 22:04:13

Thread: Don Young's 0-4-0 dockyard tank 'Tug' (7.25"gauge)
09/09/2017 21:02:16

Sorry to hear the builder used steel.

After alum the 4BA threads should be ok, and ok for new 4BA fitted bolts made of non magnetic stainless. I make up all my own bolts out of stainless for boiler fittings, a job I hate but short cuts only lead to problems later on.

I have used hard drawn phos bronze bolts in the past but it isnt as tough as stainless.

Commercial bolts are often undersize plus are threaded up to the bolt head whereas a plain unthreaded portion through the removable dome is desirable.

Cheers,

Julian

Edited By julian atkins on 09/09/2017 21:57:42

Thread: Flared Tender Sides
31/08/2017 11:22:20

Hi Clive,

Yes, the offset is the 3/64" you refer to. It was a guess by Martin Evans. He never understood the niceties of Stephensons valve gear. The correct figure for the suspension offset is 0.223".

This much larger amount is due to using launch type expansion links with direct drive and outside admission.

Don't follow Martin Evans' description of how to set the valve gear. You will need negative lead in full gear so that the lead is not excessive when the gear is notched up.

Cheers,

Julian

30/08/2017 22:04:42

Hi Phil,

I know exactly what you mean.

Just a bit of extra dressing required with my Thor hammer using the copper face on the ends.

Cheers,

Julian

30/08/2017 11:34:01

Hi Clive,

Do not under any circumstances anneal the brass sheet.

I would suggest making up an internal former out of standard kitchen work top with a radiused edge. The brass is then sandwiched between this and another piece of kitchen top or steel which is then clamped on top but exposing the length to be shaped over the lower kitchen top.

The brass must be very securely fixed so that it cannot slip.

The exposed brass is then slowly beaten to shape.

This is the set up I have used which is rather Heath Robinson-ish. I ought to have added something better to secure the brass as it did slip. However this really is my kitchen work top and drilling it was out of the question!

dsc01202.jpg

I have used the same sort of set up for GWR tender bodies and bunkers and pannier tanks. There is something to be said for having material greater than the height of the tender sides as the bend is more easily formed. Then trim back to the required height.

I presume you know there are 2 types of tender drawing for PoW ? Do you have copies of ME for 1971?

When you get to the valve gear it can be significantly improved by increasing the suspension offset on the expansion links.

Cheers,

Julian

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