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Discussion in 'Area 51' started by Dave Holt, 18 July 2020.
Mmmm. Wonder what this might be in aid of?
Just loosely assembled at the moment.
Hmm, my notes aren't immediately available, but I think that's a Gresley pattern crank axle...
I'm going to make a small leap of faith and assume it has some connection with your avatar...?
Good suggestions and I do have a rebuilt Bulleid West Country with an inside crank and valve gear, but actually, it's for a rebuilt Royal Scot.
Interesting. I freely admit I don't know much about LMS prototypes, but I had no idea they had balanced crank axles; I was under impression they were much less common than is apparently the case.
I look forward to seeing the build
Hi Dave............. "Rebuilt Royal Scot" and my radar went in to overdrive.
Who's kit, and 4 or 7mm?
I look forward to seeing the build, although mine will be plain vanilla without the inside valve gear.
Balanced crank a hang over from Mr.Webb 30 years previously?
The inside cylinder 0-6-0s did not have balanced webs so perhaps ideas at Derby had started to change or there was some North British influence? I believe the Derby design office also had access to the Southern Lord Nelson drawings, which might also have influenced the design. Anyway, the drawings (Wild Swan Scot profile books) for both the original and rebuilt locos clearly show balanced crank webs of the shape modelled.
The loco is another 4 mm scale Brassmasters product which will be to P4 standards.
The kit makes no provision for inside valve gear, so it's going to be a bit of a challenge. Don't expect any action for a while, this is still very much at the planning and accumulating bits stage, although I have had the Gibson driving wheels machined to reduce the flange and centre boss to the scale dimensions. This is to try to avoid the clearance problems that can occur with this kit.
The LYR also had balanced crank axle designs going back to the 1900's for a variety of locomotives, so it would not be too much of a stretch for Horwich/Crewe influences to still be evident during the Fowler/Midlandised era of the LMS, especially as Fowler trained under Aspinall with Hughes and Gresley.
Going back to the Royal Scot:
Derby drawing, 180D 27 10838 Crank axle in the NRM catalogue.
I'm going to watch your thread with great interest! I have 2 Brassmasters Scot kits - almost untouched - and I have built the running plate and cab plus chassis for another - but certainly not with any inside motion. My one abiding memory was trying to figure out the nickel silver 'origami' in the frontal 3 dimensional space in the region of the buffer beam/middle cylinder covering/front running plate. I did complete it BUT the difficulty I had convinced me that I had not approached it correctly. I'm therefore really looking forward to finding out if you have any difficulties in that space when you get there. If you don't, I might as well sell my kits, and give up on 4mm, but if you do, I'll be ready to drool over how you handle it!
Please don't hold you breath - it could be some time before the Scot makes any physical progress.
Currently, I'm still scheming out what extra parts are required and what modifications to the kit spacers and valve gear support frame will be required.
Although I haven't built one of these Scot kits before, I did try to sort out a part built example for a friend. One of the issues was that the driving wheels tended to touch inside the splashers if any side play was allowed on the centre axle.
I haven't really studied the front frame origami but I expect it to be along similar lines to the Black 5, which wasn't too bad. We'll see in due course.
Hi Dave, I have some photos of the inside of the frames that Pete Waterman took in Crewe, I can send them to you if you are interested in them.
That would be good if you could, Len.
Hi Dave PM your email address and I will send you the copies.
Still at the plotting and scheming stage. As part of this process, I've marked out some key reference points for the inside valve gear on the main frames. A friend turned some centre locating buttons, which a a good push fit into the etched axle bush holes in the frames, to enable the axle centres to be accurately located. The inside of the RH frame has been marked with the inside cylinder centre line (at 1 in 50 slope), front and back faces of the cylinder and the centres of the expansion link pivot and the inside reverser shaft. The two latter have been drilled with a 0.5 mm pilot hole.
Marked out frame
and a rather cruel close-up
The double lines for the expansion link are due to a better dimension from the axle centre was derived after the initial position had been scribed. This had be based on scaling from published drawings - not the ideal process, but often necessary. The centre for the reverser shaft unfortunately coincided with edge of a half etched recess on the opposite side of the frame, which caused the centre of the hole to drift off slightly. I can live with this as the mechanism isn't functional and the error small.
I've just re-read your comment about modifying the Gibson wheels - and it has triggered my memory about struggling with clearances. It was a good few years ago and my memory isn't clear but I seem to remember concluding that the Ultrascale drivers were also over scale on one of the dimensions. I'd better check thoroughly before I think of proceeding! I could well have been the culprit for the struggle you inherited!
The first component for the inside valve gear has been produced. But what is it?
Well, it's the support bracket which carries the inside gear reverser wey-shaft and the lifting arms. Here it is roughly (very) placed against the main frames. It will be attached to a narrow frame space which locates in the short vertical slot.
The inside motion plate has been modified to drop it lower, such that the opening for the slide bar ends and con-rod coincides with the centre line of the piston rod. The main opening still needs to be modified to support the rear end of the inside slide bars.
The inside crosshead, complete with the drop link has now been made.
It is based on a Brassmasters brass casting from the Fowler 4F kit, modified to provide the drop link necessary of the Scot inside motion. The resultant item is not strictly a scale replica of the actual part, but is an approximation which will fit the etched slide bars (from the same kit) and provides an attachment for the anchor link that is in the correct relationship with the gudgeon pin hole in the crosshead. The drop link is a loose item, attached to the modified crosshead by a 14 BA screw and a locating dowel, the idea being that the drop link can be attached to the anchor link, off the job, and than attached to the crosshead on final assembly within the frames.
Here are the component parts, with the cast crosshead modified by soldering a 1.5 mm thick spacer to the lower face and the cast piston rod replaced by an over-length piece of 1 mm N/S rod, the drop link made from 0.5 mm thick brass sheet and the 14 BA fixing screw.
and here is the complete assembly.
Some progress over the past few days since the drop in temperature has made the modelling room more habitable.
The support bracket for the expansion link has been made and is seen here loosely placed in position on the motion bracket. It's dimensionally right but only representative in detail.
The inside cylinder has also been fabricated, complete with the unusually long rear valve chest. Where possible, I'm using commercially available bit and spare parts, so the valve spindle guides and cylinder covers are from the Comet standard LMS/BR etch. Not strictly prototypical and some spare, unwanted holes, but it saves scratch building. The front and back cylinder relief valves are just the mounting tube at present and there's the drain cocks to do.
Here is the cylinder assembly.
And here, loosely placed in position on the RH mainframe.
Slide bars and then valve gear rods next, I suppose.
A start has been made on the inside valve gear with the production of some of the rods and assembly of the front portion of the gear. The anchor link is from a spare Brassmasters Black 5 etch and the combination lever and radius rod are from the same source, but modified by cutting the laminations to produce shorter items.
Here, the front part of the gear is temporarily assembled to the cylinder and cross head.
Some of the other components - shortened radius rod, slide bars from 1 mm sq brass rod, front and rear slide bar mounting plates (modified from a Brassmasters Fowler 4F etch) and the motion plate, now modified to allow the cross head/con rod assembly to pass through and with a bottom flange added. On assembly, the rear slide bar mounting will be soldered to the front face of the motion plate to locate the back end of the slide bars.
Mighty fine modelling that Dave,
Enjoying the photo stages showing how you went about it.