This tender chassis will be built from scratch starting with a black plastic centre the ones fitted to the A4 tender are of a high melting point plastic but mine with be a lower melting point but should be ok if the temperature doesn't start to reach 212f all this plastic part does is act as a fixing point for the frames and the tender boiler and act as an insulator for the 2 frames..
There isn't much to do to the plastic insulator once its out of the printer just a clean up and check its going to work ok not to long or not to wide if a problem arises then its back to the drawing board make changes and print another one much easy than years ago, so the brass chassis plates will be the next part to have a go at.
Two brass plates are cut out roughly then soldered together this will make marking out and drilling much easier.
Once milled to the correct width as in the picture here but still left too long at this point.
Find the middle of the frames and mark out the middle axle box position.
You can see the Hornby frames in this picture and as the A3 and A4 tenders were a 8 wheel sets design the axle boxes are to close together if you compare the leaf spring and axle box assemblies with the brass frame section above.
The new frames still soldered together are at the bottom of the picture and are still to long at this stage but I need to mark the positions of the wheel centres and mill them in place. A set of Hronby tender wheels at the top of the picture will be used and at this point in time I might not re engineer them with spokes but will see maybe later.
With a thin coat of marking out ink the position can be marked out I think the slots once milled in place should be checked to see that they are all the same as to much of a venation even with the contact strip pickups might leave wheels floating in the air.
Now with the frames in the mill the milling is taking place the fixing holes will then be drilled in place and the frames could be unsoldered and the old solder cleaned off.
This is the Hornby train of Coronation Scot and coaches running on my track and very will it runs to using the old Zero One system I have a change over switch so I can run live steam or the standard 12 volt electric trains.
I will not be painting the live steam engine blue but red and the transfers have already Arrived along with the name plates.
Some 60 years ago as a boy did you build a plastic kit of a plane and in the box was the transfers so I would rush to glue the plane together just so I could put the transfers on with out painting as this would only make the application of said transfers that much longer to do and you know I still have that feeling when looking at transfers for a model.
back to the job.
Still soldered together and with the axle box milled in place, plus the fixing holes to screw the frames to the plastic insulator. The frames are almost finished they will need tapped holes in the edge to take a brass strip that will stop the wheels and axles falling out when you pick up the tender and engine. The wheel pickups will also need to be fixed in position