Model Mechanics - 'Eagle' drawings

[bambuko]

Well, they have been built in G1 so there should be no problem at all in G3?

[John Baguley]

The well known C M Keiller built a 1/2" scale Midland compound which he described in ME Vol. 77 Issues 1906 and 1907 and which won a silver medal in the 1937 Model Engineer exhibition.

The HP cylinder was 5/8" bore and the LP cylinders were 11/16" bore, all being 1" stroke. Three sets of Stephenson valve gear were fitted. The boiler was designed for a WP of 150psi but was run at 135psi as this gave all the power that could be used. A simpling valve was fitted for starting purposes.

The loco was built very close to 'scale' and looking at the photos in the articles was a beautiful piece of work, well deserving it's silver medal. I wonder where it is today?

John

[MikeWilliams]

Thanks Baggo.

I'd better build a simple before trying a compound, but I just find them fascinating.  There are of course several preserved, working boats with compound engines but the nearest I've come in model railways is driving Dave Roberts's superb Webb Teutonic in 5in gauge.  This has two outside high pressure cylinders and a single huge inside low pressure cylinder.  As described by contemporary authors, the exhaust is so soft that it can hardly be seen or heard and although with uncoupled drivers starting requires care and practice, when it gets going its 7ft 1in drivers and low friction make it scarily fast!

I guess I'd better get back to the Cauliflower before even thinking about a Teutonic.

Mike

[IanT]

A quick note with regards to the posting below with the VS drawing attached.

Chris has informed us that this GA was sourced from the 2-volume "Locomotives; their Construction, Maintenance and Operation" by A. Morton Bell and published by Virtue & Company Ltd (7th Edition 1949).

Whilst the Author is undoubtedly deceased and I cannot find any current reference to Virtue & Co. I have to assume that this material is still copyright. In this particular instance, after discussion, I have decided to leave the posting "as is" (unless we are asked to remove it) as hopefully it is causing no substansive damage to the IP 'owners'.

However - please note that had this posting contained an item (drawing/article) 'owned' by a more identifiable (contactable) entity - such as Model Engineer for instance - it would have been removed immediately untill/unless such time as a written consent had been obtained to publish the item.

We understand that some sites do have a policy of allowing postings containing copyright materials - provided - that the source of the material is acknowledged. However, please note that this is not the policy of this Forum.

Regards,

Ian Turner
Moderator

[Alan]

Hi all.

Post number 1. It was only by chance that I came across this forum and jumped at when I did.

All this talk about The Eagle by Martin Evans. Marvellous. I started building one, as my first loco, when the articles first started appearing and after I found a night school that had ME facilities. Since then I moved to West Wales and there is nothing similar her so the project ground to a halt. I am now lest with a rusting set of frames and a complete set of castings and boiler material (from Dave Goodwin). There is a chance though, that I might be getting a lathe in the next 12 months or so. At least then I will be able to restart after a break of around 15 years or probably more.

I have one question though. As obviously some of you have actually built one of these can you help with springing. It is not mentioned in Martins 'words and music' other than where to put the coil springs. What strength springs and how do you balance the load evenly between the drivers and the leading truck?

Cheers

Alan

[cabbage]

Welcome!

The strength of a coil spring is dependant on three things.

The thickness of the wire.
The number of turns.
The temper of the steel.

The hard part is working out what the load is on each axle -this is "O" level stuff, (things were so easy when I was 15!) According to theory you need the most weight on your drivers and the Centre of Gravity needs to be between your driving wheels. You would need to split your weights at 1/6th 1/6th 1/3 1/3. The method I used for my 2-C0-2 locomotive was to weigh each axle set with a set of kitchen scales -then do the maths... The eventual position and weights were set by sticking pieces of Osmium shot (fishing weights) to the chassis with epoxy.

regards

ralph

[Alan]

WOW!

Thanks for that Ralph. I take it that means that springing is more or less the last thing to do. i.e. frames and running gear completed plus boiler completed, erected and filled. then the same for the tender. No wonder Martin didn't mention it. I am not sure about the kitchen scales though. When the time comes I will have to work out how to weigh one axle set on the scales without having the adjacent set on them as well.  Nothing is impossible though. Just, for me, a bit of a long way off yet.

Cheers

Alan

[cabbage]

Well, build a straddle that holds one set of wheels and then couple the top to a spring balance. Pull on the spring balance until the wheel leaves the floor. This will give you the weight on one axle. That's the easy bit done...

Here is a place that I shop at: http://www.ashfield-springs.com/compression-springs-list.php

If you need to paint them then stick to std carbon steel. The others will require "special metals primer" to get anything to stick!

regards

ralph

[Alan]

Hi again

Yes, I was thinking along those lines but thank you for pointing it out. Also thank you for the link. As I said, this all started a long time ago and I have been out of the mindset. So much has changed since then. Cleaning up and getting the frames painted is number 1 priority at present. Then sort out a workshop and acquiring a lathe. Then I can start cutting metal again. I had not realised how much I missed it.

Now this is shown on the forum I can return to it if need be. Plus I have bookmarked the link.

Cheers

Alan

[stoomraider]

Hi All,

I started an 'Eagle in 1980, and have nearly completed it. The paint did not stick. I also redesigned the tender to look like the correct GNR(I) one, had it laser cut from 1/16th" brass sheet - nearly complete.

But, with the internet I have discovered just what an inaccurate example of the class the model is. However, I would like to change that. The fullsize surviving of the 'V' class loco 'Merlin' No 85, and part of the RPSI (Ireland) is having a new boiler made (by Harland and Wolff) and should be back in steam. This loco by the way is the last surviving operational compound loco remaining in the British Isles, (so I have read).

Kind of begs for a rework, does it not. Unfortunately, the RPSI do not have many drawings in good order, so I propose to work from a brass kit from Studio Scale Models. I have no access to 'Merlin', as I live in South Africa.

See Model Railway Journal No 148 for an article of this kit as 'Eagle'. - This loco just grows on one.

Having done some research on CM Keiller, and his models, there is no excuse in not making it a compound either, in all the useful gauges too.

As a member of the N25GA, I hope to work with their castings, if  suitable.
I am awaiting delivery of the 'Kit' . If anyone knows any more information on the class, please let me know.

Regards
Errol

[MikeWilliams]

Great idea Errol.  Its certainly a good looking engine.  I'm sure compounds have been made in Gauge 3, but don't think I've ever seen one, so that will be fascinating too.  I have driven a 5in Gauge 3-cylinder compound and it was a great experience.  Please keep us informed.

Mike

[John Baguley]

I have also got a part built Eagle stashed away which hopefully will get finished one day! It was one of my better Ebay purchases a few years ago and the work so far is not bad.

Like Errol, I did some searching on the Net and found some good photos on the RPSI website. One of the glaringly obvious 'mistakes' in Martin's design is that the connecting rods should be INSIDE the coupling rods, not outside. I've no doubt Martin did this on purpose to simplify the design as it was meant as a simple beginners loco.

I have toyed with the idea of making it as a true compound but will probably finish it 'as designed'. I've too many other projects on the drawing board besides this one!

With regard to 'scale' models, I am firmly of the belief that it is just as easy to build an accurate model as a grossly inaccurate one. I don't think it is necessary nowadays to follow the LBSC practice of fitting huge boilers onto over cylindered chassis. With proper valve gear design to use the steam efficiently it's possible to produce more than enough steam from a 'scale' boiler, provided the grate area matches the size of the cylinders and wheels.

John

[IanT]

By a strange coincidence (I was looking for something else entirely) last week I came across an article about the Irish compounds and was diverted for five minutes or so at the time. I've just gone and dug it out again. It's in ME No. 3345 (17th May 1968 for those who have it) entitled "Irish Three-Cylinder Compound Locomotives" by C.P.Atkins.

There's no drawing or too much technical info but it's an interesting essay on the thirteen Irish locos.

There are photos of No 87 (Kestrel) and No 206 (Liffey) although they are not really that great for our purposes. So, as these were Beyer Peacock engines, I've just gone and looked in "B-P Locomotive builders to the world" by Hills & Patrick to see if there were any better photos there. There is quite a good one of No 85 (Merlin) undergoing refurb at Harland & Wolff's shipyard in 1977. They've dropped the wheels and motion off but there is some quite nice detail shown of the smokebox and front buffer etc that a 'V' modeler might find useful.

Errol, as you are not exactly local (& for your personal use only) copies could be provided if you thought they would be useful in your "Eagle" endevours. Please e-mail me if so and best wishes for the build.

Regards,

Ian T 

[andrewfoster]

Just looked at this thread for the first time, and will take up the Scottish cause... The Highland Railway had many magnificent outside cylinder 4-4-0 tender locomotives, mostly with the Alexander Allan style of outside framing and inside valve gear, built by David Jones (and just two later ones with outside gear). The early ones would make beautiful large scale models. The Highland's old enemy, the Great North of Scotland had some very attractive outside cylinder 4-4-0s too.

I would add a little to Ralph's note on spring design. Another essential factor in calculating the stiffness of a helical spring is its diameter - too small, and you will have problems with non-linearity and stress concentration, leading to fractures. In practice, there are many other factors that go into spring design, and predicting performance with tolerable accuracy is difficult. I've rarely designed springs except in cases of dire necessity, and have almost always found a stock item somewhere. Ralph's suggestion was good, and I'd add Associated Spring (http://www.assocspring.co.uk/) as a well known supplier (they are the successors to the old Herbert Terry company). If you can use a standard part, the engineering has been done for you. If you do it yourself, a spring design manual is a good investment.

Andrew

[IanT]

If you don't want to make your own springs - Bruce Engineering (Polly) sell the more usual sizes for ME use - and they also give the diameter, coils per inch, pounds per inch deflection etc for their various sizes stocked. So you can fairly easily work out what you need from that.

Their catalogue is downloadable from here:

http://www.pollymodelengineering.co.uk/sections/bruce-engineering/price-list.asp

The springs they stock are on page 65. As you may have gathered from previous posts of mine, I have used them from time to time for things "steam related" and have been very satisfied with the prices, service, delivery etc. They don't seem to mind small orders either - although I'm sure they would prefer larger ones! I have no other connection with them.

Regards,

Ian T