Sunday discussion time.

Well, its been a while since I've done any musing here.

First up I came across this on one of the forums I frequent (its English BTW. for some odd reason I have a soft spot for British railways, though mine tends towards Victorian railways).
Its from a company which sells aftermarket parts for 7mm scale diesels.

"We have sold about 50-55 of the complete sets for the 47 + many more cab interior sets & a few bogie sets [other than to those who have the complete works] but I've never seen any of them finished by customers - mind you we have sold 150+ of our Class 08 Sets for the Bachmann brass job - and I've only ever seen one or two of those finished! Remember that it is thought that only one in five of kits sold ever get built [even less for plastic kits] and of those, maybe one in five get built anything like correctly and you'd only be expecting to see around two Heljan 47s nicely finished with all the sets on!!!"

Now this does tend to ring true somewhat to me, and I just wondered how many Trackgang kits have been sold and completed. Likewise for the brass etch cetera diesels (I've seen maybe 5-6 Da's built and maybe 3 Dc's?).

-Secondly, as you all know I've been kicking round how to make the large stem locos that I'm going to need to do. Now, as we all know there are going to be some compromises involved with the under gubbins. for one. You struggle to stick your hand between the wheel flanges on a Ka, and scaling that down accurately is going to be a bugger. Now to counter this my plan is to shrink the wheels from 11.25mm down to 11mm and increase the wheel spacing to 12.5mm. This gives an NMRA standard flange of 0.5mm and 0.5mm between the flanges. To compensate for this there is an extra 2mm to be added in the boiler, which given that its 100mm long is only an error of 2%

Now I'll point out at this point that this sort of thing also goes on in the S scale models, and they also have problems in the cylinder department. Why? Because the wheels are wider than the prototype and so it pushes everything further out, making the loco wider than it should be. You can also see this in the commercial stuff where the valve gear sticks out a long way to get the clearances functional. theres other ways arround this, mostly involving the minimum radius

Its all really just a question of which compromises you are prepared to accept, and as long as the proportions tend to be about right, the rest teds to get hidden. To me, small wheels with too many spokes stick out like a sore thumb.