Welcome to Part 2. Frame Assembly
Recently I have assembled the frames. Frame spacers were cut to a width of 46.5mm from 28thou nickel silver. I made the decision to incorporate the motor with the flywheel towards the rear on the rear axle. The reason for this was to keep the space under the boiler free from intrusion and the motor covered up in case of using the model in the rain. It also left the motor terminals closest to the control system (yet to be chosen but will be radio control/batteries). The difficulty here was that where the motor was to go would be inside the firebox but in this same location the frames are cut out. I worked it out that the boiler would be something like 1mm on each side set back from the inside of the frames, the ash pan would be 4mm as ash pans sides usually line up with the inner firebox sheet (firebox sheet - water space - outside boiler plate - boiler cladding/sheeting). I therefore cut the stretcher with a 5mm [ shape on each side, the same dimension as the opening in the frames. The frame stretcher that is horizontal along the top of the frame is cut to the same width 46.5mm and I make sure that the end of this stretcher is right angle as I will use this when assembling the frames to ensure squareness. The stretcher at the front end/cylinder end is bent to L shape. I lay 2 pieces of thin timber on a flat surface. This is due to the raised portion on the rear frame stretcher. I use small metal blocks/weights to hold the side frame and the stretcher in place which is followed up by a quick tacking with the soldering iron to hold in place. I do this for all the stretchers and then run solder along the seams to ensure strength. The frames should look like my photo.
In the following photo you can see the frame assembled and the openings just mentioned and the round opening for the motor to slot through to stop the motor rotating round the axle when under load. The brass rod centrally in the frame is the reverser rod that lifts or lowers the stephenson link motion for the real inside valve motion and I have used this rod to hold the frames to the correct spacing over frames. I could have used the motion bracket (support for slidebars on the outside motion) to keep the frames apart but I have chosen to have the cylinders and motion bracket to come out as one for ease of painting later on.
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Axleboxes
On 3 different sheets of metal (brass or/and nickel silver) I mark out the first line, then mark off another 10.5mm away (dimension of hornguides) then scribe out into box shape, 10.5mm square. I find the centre and centre pop it for drilling.
Here I am using 3 different pieces of metal and thickness. You can see in the photo what the thickness is and that on the thin sheet there are 8 squares. This is to be soldered on the front of the axlebox to keep the ball racer bearings in place and from the other side to insert them (I think the thin pieces attached to the inside of the axlebox is over kill). Drill all holes out to 5mm. Place the thin sheet to the side as it doesn't need more drilling. Drill out the other remaining holes to 6mm. I then cut the parts out of the metal and using the drill bit to hold them to the correct position I put the ensemble into the vice, clamping it off then removing the drill bit. I then solder the top edge together, then flipping it over and soldering the other end (holding it in the vice to use it as a handy heat sink to stop it falling apart when the heat transmits through). Once all 4 axleboxes have got this far I then run a 1/4" hand reamer through the hole to open it out to correct size. It isn't the easiest part but it helps if it is held in the vice. Once the hole is 1/4" dia I then solder the thin sheet on the face that would be on the outside facing the public so that when I put the ball race bearings in they don't just slide straight out (I made a mistake on the first run, soldered it to the wrong side so I had to solder the ball race in place, didn't want to have to do that). The axleboxes are held away from the wheels by using brass tubing with an internal dia of 1/8" to fit the slaters wheels and is cut to length.
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Here is the axleboxes when installed in the frames for the first time, notice the soldered bearings!
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Click to see full size image
Gearbox
I made a new gearbox frame as the one that came with the gears couldn't take a 1/2" ball race bearing, so I made my own replacement frame from 28thou nickel silver. I could tell you how to make this gearbox frame but I think it isn't for a beginner!
Here are the photos of the finished item.
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Click to see full size image
Click to see full size image
Click to see full size image
Part 3 to follow soon
