... Then I started measuring. I was very happy with the larger parts as supplied, but the smaller end-parts seemed far too tall for my liking. ...
Ian
Ian is correct, the plastic mouldings which represent the vertical parts of the underframe trussing are too deep from top to bottom - so much so that the "L" angle has to be cut short, as noted in the instructions, to avoid fouling the bogie headstock. An improvement in the situation is possible and this post details how Peter has gone about the construction of his first EZ-build underframe.
First, an acknowledgement, there are some drawings in Mk.1 Coaches (Parkin, HMRS) and those drawings provide an indication of the length of the three middle verticals. There is a cross section which shows the outer verticals and that drawing is not dimensioned. I asked Bob Reid about this detail of the prototype and he has provided an answer for coaches with equalised brake gear... 1' 3 9/16" from the top of the underframe to the top edge of the lower horizontal, that converts to 9.08mm for 7mm scale models. Thank you Bob for the info and the drawings.
Second, a point of prototypical interest, the Mk.1 underframes have detail variations in the lower horizontal "T" section of the outer verticals - the reason for this variation is (probably) to allow for the higher position of the brake pull rod on some carriages. For Mk.1 coaches which have equalised / compensated brake gear on the bogies the "T" is as written and the top of the "T" is level with the lower edge of the "L" girder. For Mk.1 coaches which have unequalised brake gear the "T" is upside down and the lower edge of the "T" is just above the lower edge of the "L" angle.
Thirdly, a warning, the position where the "L" angle runs out with respect to the central longitudinals (part of the floor extrusion) on our model has been established by trial and error... on the prototype the outer end of the "L" angle takes a curve such that the upper edge of the "L" angle runs along the lower edge of the central longitudinal - we have not replicated this aspect of the underframe design.
So, to the result of a cut and shut exercise:-
This photo shows how the "L" angle is extended to meet the central longitudinal.
This photo shows the taper on the "L" angle to achieve the join with the central longitudinal... and the shorter outer verticals.
This photo shows how the "L" angle disappears into the gloom above the bogie... and that there is room to extend the "L" angle to and beyond the bogie transom as per the prototype.
Tight - and not touching, there is about 0.5mm clearance between the "L" angle and the top side of the bogie headstock.
Ah, yes, the important matter of dimensions.
The lower edge of the central verticals is a shade under 2' 6" from the top of the frame (read as underside of floor) - our mouldings were cut to have an overall depth of 17mm. The mouldings for the outer verticals were cut to have an overall depth of 8.5mm (for a carriage with non-equalised brake gear). The end of the "L" angle is 90mm from the end of the floor extrusion.
For this underframe the mouldings were shortened... which means that this underframe is for a carriage with unequalised brake gear and BR bogies. Maybe the next example is going to be for a carriage with Commonwealth bogies and that shall require further modification to the mouldings for the outer verticals.
regards, Graham
