andrewnummelin

I'll be interested to follow this topic as I'm building in 4mm scale steam rail motors from the Alexandra Docks which had motor units identical to the later LSWR ones. I believe the motion of the lovely original was essentially the same as the later ones - a real modelling challenge. With the discussion about the crosshead and slide tube I thought some of my ponderings could be relevant. The parts are small! The slide tube is a challenge - enough of the side has to be cut away for the droplink, but if too much is cut away the crosshead won't be properly supported. The only thing preventing rotation of the crosshead is the fork in the connecting rod and the fit of the crankpin. Engineering the clearances will become more and more of a challenge as ones goes to smaller scales. The droplink will need to be fitted to the crosshead after the connecting rod has been fixed to the crosshead and this inserted into the slide cylinder. I've yet to work out how to do this in 4mm - the valve gear etch I had made by PPD will be going to Missenden in the autumn where I hope to get help putting it together. In addition to the drawings in the books on the LSWR, you may be interested to know that the NRM has a complete set of blueprints for the underframe and motor unit of the second ADR railcar so there's no real excuse for not getting all the tiny bits correct! A small clip showing the crosshead is attached.

I'd suggest that in 7mm a pair of excellent books are those by Geoff Holt "Locomotive Modelling from scratch and etched kits - a personal approach" published by Wild Swan. Thinking of the GWR/WR, for a first scratch built loco I'd go for something without a taper boiler or belpaire firebox so 1915 offers rather more possibilities: still you did say you like a challenge! As for livery, going back a bit before 1915 would give something much more elegant than BR green. Still for something a little different, why not think about GWR 196-201? I believe they were very similar to "de Bril" so you can go and look at this for details not shown on many drawings? https://nl.wikipedia.org/wiki/NS_700_(stoomlocomotief). Beste wensen.

I like the look of the SECR loco - should be a fun build! Looking at the sizes of the springs it may be seen that the rear one has more plates than the centre one: this is common and came from having the inside frames terminating before the firebox so the rear one carries the full load, the centre driven axle had bearings & springs fitted to both inside and outside frames so the springs have fewer plates than those of the rear wheels. The front axle probably carried less weight than the driven ones and probably only had the visible spring that looks as though it may have been intermediate in size between the those on the driven axles. See https://www.scalefour.org/forum/viewtopic.php?f=19&t=7927#p88936 for a discussion on the topic.

If you come across a problem like this, always double check whether the (jig) axle is oversize or the hole in the bearing undersize. I suspect the latter is more likely - I’ve often found that bearings need to be reamed out to get a running fit.

Great to something from a company that is less often modelled: well done. Anyone interested in a bit more background should take a look at the Welsh Railways Research Circle https://wrrc.org.uk/ptrrc.php The PTR’s unique steam rail motor would be a fascinating modelling project.

Extensive details including drawings of the TVR coaches may be found in John Lewis's "Great Western Auto Trailers - Part Two Post Grouping and Absorbed Vehicles", Wild Swan 1995 ISBN 1874103259. I've always thought these were attractive looking vehicles. Have fun modelling the TVR control gear! Anyone interested in these should really join the Welsh Railways Research Circle... https://wrrc.org.uk/index.php Regards, Andrew Nummelin (WRRC Secretary)

Great to see this model. I bet there aren't many of these around. My own efforts may be seen on the Scalefour Society Forum at: https://www.scalefour.org/forum/viewtopic.php?f=100&t=2568&hilit=pc%26nr#p27782 If anyone else should like to have a go it should be noted that the HMRS can supply a copy of the general arrangement drawing of the loco as supplied to the Mersey Railway: https://hmrs.org.uk/drawings/0-6-4t-4ft-7ins-driving-wheels.html It's a great shame I hadn't discovered this when I started my model - I could have avoided several errors! You mention the problem of the underhung springs: the visible ones were fixed to the outside, not inside, frames. Note the different hangers and sizes. (The GA shows the springs for the inner bearings of the driving axel to be above the axel.) I've discussed the problems of underhung springs with a number of modellers more experienced than myself, and have been given the advice that the best option is to fix the spring to the bearing but have it loose in guides on the frame. But one still has to think about the strap under the axelbox! I'd add another couple of references that I found very useful: Maund, T.B.; The Steam Era on the Mersey Railway 1886-1903; Railway Archive No. 2 Nov. 2002 p. 3 Parkhouse, Neil & Watson, E.J.; The History of the Steam Locomotives of the Mersey and Mersey Electric Railways; Railway Archive No. 5 Nov. 2003 p. 27

Gents, I'd also guess at the parapet being cast: if it were built later I'd have guessed at welded wrought iron for the attractive supports with the top rail being cast but welding was not common at the time and there was a foundry on site. I suspect Alistair Warrington might be the person to approach for further details. For modelling I suspect any approach is going to be quite a challenge. Etching would have to be multi-layer to give the right profile of the supports, 3D resin printing would give a product that would not be as satisfying as a metal unit (and also probable very fragile), and lost wax casting (possibly from a 3D print wax) would be expensive! Just as much of a challenge would be the railings of the walkway under the main deck - simple tube but very complex posts! Detail from "A26/B" from the old OPC photo collection. I'd not looked closely at the curved part of the viaduct before, but my impression from a bit of the ".../6257418/details/504" image (below) is that the main support structures are straight (cyan) but that the top is curved (orange). More modelling fun! Must get on and build a new chassis for my NA&HR loco...

I'll be using the frames from the Angenoria kit with pcb spacers, HighLevel hornblocks and CSB springing. I've yet to order a new motor and gearbox to replace the one taken out after my first disaster...

The two sides are very similar but there are detail differences (tool box, lamp irons, brake system, cab side rivets and I suspect piping). I thought I'd taken enough photos but I can now see that I've missed some that I should have taken. Will have to go back and have another go once the current work has been completed - will show all the mistakes that I'll have made with my model (I ruined the first chassis and set of wheels so will have to start again.)

Careful with the firebox - it may be too tall. You may find detail photos of Trojan of use in identifying/placing small parts. http://www.andrew.nummelin.me.uk/ADR/Trojan/index.php

I guess you are referring to "Trojan". Are you sure about it being Center Models? Could it be the CSP/Angenoria one? If so there are differences between the 4mm and 7mm versions. You may find this thread useful https://www.scalefour.org/forum/viewtopic.php?f=20&t=6700#p71469

You may get some hints from my contribution to Scaleforum with the useful comments from other people. https://www.scalefour.org/forum/viewtopic.php?f=100&t=6798#p72845 Have you seen the Binnie drawing? http://www.colinbinnie.com/pdf/taff_vale_railway_locomotive_267.pdf (Also in Model Railways May 1972) Note the length of the connecting rod - it should miss the crank pin.

If you do what I did and use Loctite, be VERY careful. It wicks so easily that some got into the axel bearings of one of my locos and I didn't notice until smoke came out of it as the chip fried (on it's first test run in public...). As someone else advised, drill and pin (or even bolt) is the most secure method.

I should have added the point that John mentioned regarding space between frames in OO sometimes being a restriction, however I'd assumed that as your model is to have outside frames you would put the bearings in those, so leaving room for any gearbox.