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Don Young's 'Doncaster'

Articles in ME starting 1`st Jan 2021 'Flying Scotsman 5" gauge

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Peter Seymour-Howell23/02/2021 15:38:53
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31 forum posts
5 photos

Hi everyone

This thread is really in response to another topic where it was pointed out about the lack of threads on locomotive builds and so I thought that I would do my bit for the forum in helping to add more content. However, I'm not going to start a build log here. Some may have seen or even be following my articles currently running in ME and thus don't want to take away from the editors hard work.

I did think though that what I could do is to start this thread for people who wish to know more about my quest to build a highly detailed model of 4472 or have a specific question about the build. feel free to ask ask here and get a quick and honest response directly from thehorse's mouth' so to speak. This is perhaps something a little different, whether it's of interest to other members here? well, only time will tell..

This image was taken two years ago at an event to commemorate the late Bob Todd, held at my home club track, NLSME. The model has moved on a very long way since 2018 but this was the last time that she was assembled (only for that day) and so perhaps the best picture to post to see her true form. She is being built to show her as she would have been seen in 1938 although there is a little modellers license which has already been detailed in the magazine. Everything is being built either to scale or as close as humanly possible and most parts are planned to be working. Well except for carriage heating, the gauge will work though..

48464716221_cb458e0da0_o (2).jpg

Anyway, as I say, I'll try to answer any questions that may arise during the series here asap.

Regards

Pete

Phil H123/02/2021 20:04:19
344 forum posts
40 photos

Pete,

I really nice engine. I am struggling in the lower division with the small 0-6-0 Rob Roy build so it is nice to see something substantial. I'd be very interested to know all sorts of information e.g., how long, all traditionally built or have you used laser parts. Who built that very neat boiler etc.

Phil H

Jon Lawes23/02/2021 20:28:49
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469 forum posts

The article in the Magazine is very enjoyable; well worth a read!

Beautiful engineering.

Peter Seymour-Howell23/02/2021 20:49:07
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31 forum posts
5 photos

Hi Phil

All models are just a 'sum of their parts', Rob Roy being no different, admittedly the larger the longer they take to build.

I bought the drawings in 1998, spent some time researching the subject, in fact, I still spend a few hours each week researching material for the part currently being made. I guess the true start date is 2010 and most days since I have worked on the model. There was a 2-year gap where I completed a part built Heilan Lassie and also some time taken when building my highly modified car engine. I use laser cut parts where I can, most are so cut but the traditional saw and file has been used when required. I'm not a CAD man so I get most of this done by those more experienced for which I owe them a great dept.

The boiler is very much a one-off, it was built for me by Paul Tompkins of Southern Boiler Works ltd, IMHO he is the best boilermaker today. It's not fully to the DY design, in fact, in many ways, it follows the stronger designed Australian boiler code. This has allowed the working pressure to be increased from 90 to 100 PSI. It is very much a 'scale' boiler in as far as it's profile, including a proper barrel taper with no step as normally seen and backhead layout are concerned. The main backhead difference being the water gauge mounting points which are a little further apart than 'true scale' to give a larger glass area. The manifold turret and steam valves will be true scale and still able to use the correct steam/water bore size for the required injectors. As is the Firehole door and general layout. The boiler is a mixture of tig and silver solder, the tubes are bigger than DY's too, giving a better tube to grate ratio, a live blower tube is used as per full-size practice.

Hope that helps to answer your questions, Phil.

Kind regards

Pete

Peter Seymour-Howell23/02/2021 20:50:15
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31 forum posts
5 photos
Posted by Jon Lawes on 23/02/2021 20:28:49:

The article in the Magazine is very enjoyable; well worth a read!

Beautiful engineering.

Thank you Jon, hope you find it of interest...

Kind regards

Pete

Greensands23/02/2021 20:52:54
173 forum posts
25 photos

Hi Pete - A really lovely engine and I think the early builds without the German type smoke deflectors were certainly the more attractive. I notice that you are using gunmetal cylinders which was a favourite of Don. Did you follow his method of burnishing using a moly compund to achieve the required finish?

Second question, have you fitted rings to the piston valves and if so how many and what choice of material. I shall follow your build with great interest.

Keep up the great work

Peter Seymour-Howell23/02/2021 21:23:48
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31 forum posts
5 photos
Posted by Greensands on 23/02/2021 20:52:54:

Hi Pete - A really lovely engine and I think the early builds without the German type smoke deflectors were certainly the more attractive. I notice that you are using gunmetal cylinders which was a favourite of Don. Did you follow his method of burnishing using a moly compund to achieve the required finish?

Second question, have you fitted rings to the piston valves and if so how many and what choice of material. I shall follow your build with great interest.

Keep up the great work

Good questions Greensands and yes I agree fully about the smoke deflectors although I wouldn't take away anything from those who love FS no matter from which era. For me, a Gresley A1 is/was the most beautiful steam locomotive ever built, more so than the A3 or A4, the form just has everything that I think makes a fine-looking locomotive.

To answer your questions, I have used an industry trick for burnishing the cylinder bores which involved the final cut in reverse using a bit that was shaped to burnish the bore on it's return stroke. It worked very well, in fact I couldn't ask for better, this will all be covered in detail.

For the piston valves, I am using bobbins following Jim Erwin's adjustable design with a few changes. These have a floating bobbin on a central bolt. The material for the seal is fluorosint, each being machined to match don's original solid bronze dimensions. Fluorosint has a similar expansion rate to bronze and higher temp range than other Glass reinforced PTFE materials.

Thanks for the kind words

Pete

Greensands23/02/2021 22:16:08
173 forum posts
25 photos

Hi Pete - Your method for providing a burnished finish somehow reminds me of the technique used by Bristols during WW2 for achieving perfectly fitting sleeve valves in their range of aero engines a la Roy Feddon! In their case I think the answer was to use a blunt edge tool for the final pass. I always thought that Don's method of burnishing was very much hit and miss.

As a matter of interest where did you source your fluorosint used to make up the piston rings?

For what it is worth I do have a complete set of LLAS minus Issue One. Do let me know if you require any supporting information from the LLAS articles.

Peter Seymour-Howell23/02/2021 22:30:13
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31 forum posts
5 photos
Posted by Greensands on 23/02/2021 22:16:08:

Hi Pete - Your method for providing a burnished finish somehow reminds me of the technique used by Bristols during WW2 for achieving perfectly fitting sleeve valves in their range of aero engines a la Roy Feddon! In their case I think the answer was to use a blunt edge tool for the final pass. I always thought that Don's method of burnishing was very much hit and miss.

As a matter of interest where did you source your fluorosint used to make up the piston rings?

For what it is worth I do have a complete set of LLAS minus Issue One. Do let me know if you require any supporting information from the LLAS articles.

Yes, that is basically what I used, the front edge was sharp for the entering pass and for the return the power was reversed and the blunt rear face of the cutter did its work. I amazed myself by how well this worked, Doncaster's cylinders are blind bores too as with full size, just to add a little complication to the setup.

Thanks for the offer of info from other LLAS issues, so far I have been able to find what I need, Don has a bad habit of saying, 'do this bit as I did on 'so and so' loco'. To be honest, I rarely read Don's notes now, I usually go my own way although did follow him religiously during the first few years of the build. I have built up a number of very full files on the subject matter with countless photos and works drawings thrown in.

I get my fluorosint from m-machine metals, as I do most of my materials, very well priced and have a good stock of material and sizes. They will also cut to size if required, IIRC the fluorosint cost me £10 per inch, so not cheap but at least you can buy what you need.

Regards

Pete

Peter Seymour-Howell25/02/2021 19:18:42
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31 forum posts
5 photos

Evening all

A few of the more interesting parts made which will be covered in the mag in due course...

Gresley's 2:1 conjugated lever

Gresley 2:1 conjugated lever

Piston valve bobbins (adjustable)

piston valve bobbins

L/H crosshead and drop link ( i have since found a closer to scale copper pipe which will replace the one seen here, the smaller pipe also allows me to make the two missing brass elbows close to scale too)

The crosshead is to the LNER 1934 pattern with the latter fitted copper gudgeon pin feed pipe which afaik was fitted after 1936, not sure of the exact date but it is seen in 1938 photos of 4472.

BTW, making the crossheads (from solid), drop links and their mounting plates took 5 weeks of hard labour..

crosshead

Regards

Pete.

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