The 7mm instructions are included with the 3mm kit. This kit is very similar to the U and the supplementary etch and castings for the U are also appropriate to this kit. Therefore we have not assembled the test etch but we have checked the parts against the U. The construction of the N in 3mm scale is very similar to the U as described in: Building the SR/BR U Class 2-6-0
We would welcome constructive suggestions for improvements to this kit both with respect to its accuracy and ease of assembly, preferably by emailing me as below.
We would like to thank David Andrews for providing us with the opportunity to use his 7mm kit as the basis for this development.
John Bateman and John Walker
15 October 2008
The David Andrews etched parts are described in his instructions.
David has modified his etches for the 3500 gallon tender since the 7mm instructions were written. Parts A and B have been improved so that parts 60 and 61 are not required. Also the brake hangers and rods have been included on the thicker etch so that parts 62 and the laminations for parts 65 and 66 are not required. Note that parts J, K and L are not used.
The 3mm N kit includes parts R and S for the 4000 gallon tender. These parts are not required for the 3500 gallon tender.
Additional versions of the following parts are included for 12mm gauge:
Locomotive
C. Spacer, cylinders
D. Spacer, rear
E. Spacer, pony pivot
F. Spacer, horizontal
G. Spacer, vertical
H. Spacer, front
WW. Spacer, plain
P1. Pony truck frame
P7. Truck front plate
77. Cylinder frame
Parts C and D in the original frets are wider than the other 12mm gauge spacers. Replacement parts are included in a separate etch with part P7. Please email me as below if you are working to 12mm gauge and you have not received the new parts.
The cylinder frame (77) for 12mm gauge is too wide at the top. A replacement part is included in a separate etch. Please email me as below if you are working to 12mm gauge and you have not received this new part.
Tender
C. Spacer, rear
D. Spacer, front
E. Spacer, centre
In addition to the David Andrews etches the 3mm kit includes a Supplementary Etch in 0.010" nickel silver and white metal castings.
In my notes I have appended an S to the part numbers on the Supplementary Etch. Parts referenced in parentheses are not numbered on the etch. I hope you can spot them!
S1 Lower slidebar (top and bottom laminates)
S2 Lower slidebar centre laminate (slot to front)
S3 Slidebar spacers (3 each end)
S4 Upper slidebar (top and bottom laminates)
S5 Crosshead top (left and right)
S6 Crosshead spacers (8), not symmetrical, holes slightly nearer top
S7 Valve guide, not symmetrical, hole at rear towards bottom (2)
S8 Combination lever, not symmetrical, oil filler towards rear (left and right)
S9 Combination lever washers
S10 Crosshead bottom (2)
S11 Valve connector, extension to inside top (left and right)
S12 Valve guide front plates - (2 x 2 alternatives)
S13 Valve guide front plate spacer (2)
S14 Crosshead link (2)
S15 Connecting link washers (full and half etched)
S16 Cylinder face drilling jig
(S17) Motion bracket centre laminate (2)
S18 Firehole door mechanism for whitemetal backhead
(S19) Cab seat (2)
S20 Gauges, layer 4
S21 Gauges, layer 3
S22 Gauges, layer 5 - front
S23 Gauges, layer 2 - back
S24 Gauges, layer 1 - spacer
S25 Plate for firebox washout plugs (RHS)
S25a Alternative plate for firebox washout plugs (RHS)
S26 Plate for firebox washout plugs (LHS)
S26a Alternative plate for firebox washout plugs (LHS)
S27 Jig for bending wires for washout plug plates
S28 Plates for optional boiler washout plugs (front left and front right)
S28a Alternate plates for boiler washout plugs
(S29) Coupling hooks. My thanks to Andrew Thomas for letting me use his artwork for the coupling hooks.
Front rods (U and N) - LHS outer
Front rods (U and N) - LHS inner
Front rods (U and N) - RHS inner
Front rods (U and N) - RHS outer
Rear rods (N) - LHS inner
Rear rods (N) - LHS outer
Rear rods (N) - RHS outer
Rear rods (N) - RHS inner
Rear rods (U) - LHS inner
Rear rods (U) - LHS outer
Rear rods (U) - RHS outer
Rear rods (U) - RHS inner
Crankpin washers
Boiler and cab (14 parts)
Cylinders (18 parts)
Footplate and chassis (14 parts)
3500 Gallon Tender (15 parts)
Note that for the N, David Andrews has opened up the holes and half etch recesses to accommodate 12BA nuts and bolts.
Peter Bossom has completed the N in 12mm gauge with some help with the chassis from Mick Rawlings. Mick is planning to build his N for the Irish Broad Gauge to run on Ballyconnell Road. Our thanks go to Peter and Mick for the following comments.
"For 12mm gauge, there are discrepancies in the width of the spacers. If you use the wider end spacers and adapt the others from the 14.2 versions then Branchlines bearings are definitely required and there is very little clearance over the rims.
If you use Bruce Hoyle (or similar) jigs then the central upstand on all the springs needs to be reduced in height before they are fitted.
Brake cross beams are too wide, but 0.45mm wire can be substituted.
Motor / gearbox choice in 12mm is restricted and I have installed a Highlevel Slimliner + three stage box as it is the only one I have that sets the motor high enough to clear the frames. However the final drive on this box is to one side and fouled the cast brake cylinders. These needed a flat filing on one side so that they fitted properly but they are off now and not likely to go back.
There is no provision made for fitting wiper type pickups. It is either plungers, or use the American method. This applies to either gauge.
The cab floor tongue (part 21) and the fold down tabs on the footplate (part 2) foul the chassis sideframes when using the 12mm chassis spacing. I cured this by reducing the height of the rear frame by about 1.5mm deep and some 6mm long. This is really best carried out before the wheels are fitted as it gets very close to the rear wheel flange !
The front buffer mounting spigots foul the upper half of parts 80/81. Cure by removing the spigot or the top half of the chassis parts as thought fit. This also applies in 14.2mm gauge.
Motor clearances are tight and it is important that the Safety valve mounting spigot does not protrude into the firebox. I have used a Finney & Smith 14.5mm motor mounted vertically and it just fits.
There is very little room on the rear spacer for the tender drawbar bolt plus the body fixing bolts so I removed the latter nuts and mounted the nut for the former on the body under the cab floor (before the rest of the floor was fitted !!)
The locating marks on the tender drag beam are misaligned. Check the alignment of the tender chassis / floor mounting points before soldering the nuts in place. I found mine to be misaligned.
Not an issue but worth pointing out - if you are using the 3 toolbox config for the tender the centre tool box door is smaller than the other two. Not by much, but enough and the instructions do not mention this. I got mine right more by luck than anything else !
If you are building a scale kit in 12mm gauge, then some compromises are necessary and the instructions need to be interpreted to suit !"
Peter also noted that a 12mm version of the spacer P7 for the pony truck has not been included. The 14.2 version could be adapted and the length of the brake cross beams could be reduced to suit 12mm gauge.
We would be interested to know if Peter's choice of motor/gearbox will also suit the U in 12mm gauge.
Mick's made the following comments on completing the 12mm chassis.
"My normal test is to roll the chassis backwards and forwards across a sheet of glass. I use an old picture off the wall. It ran perfectly without the connecting rods but when the connecting rods were fitted to one side it would roll half a turn of the wheels then lock up. This was the same for each side. When both sides were fitted it was a "pig".