Many thanks Mike. I spotted a reply from you on a build thread on the Scalefour Forum, where you mentioned that you were waiting to receive an order for the 4mm scale version. Have you built it yet and if so, how did it turn out? I note in the images that were posted in the thread, that the etchings included the correct U shaped frame for the rear pony truck, so I assume Mike Edge modified the fret before releasing it for sale. The 7mm fret had two A frames for the trucks and I had to scratch up the rear one. I see the boiler barrel etching is also included whereas I had to cut the part from NS sheet using a paper template provided by Mike Edge. U frame and boiler barrel circled.
Back on the big one I made and fitted the pick ups yesterday. Wipers from phosphor bronze wire acting on the edge of the flanges are my preferred option. These are the mounting plates ready for fitting. The long one is for the front wheels and the shorter one for the middle and rear ones
Here's where the front one is fixed.
And for the middle and rear wheels, one either side in between. Note the curve in the spacer that I made with a sanding wheel to allow the motor barrel to fit parallel to the frames. Remember this when you see all the dust from this on the spoke of the rear wheel in a later image.
Here are the wipers for the front wheels being soldered to the copper clad circuit board. I make a right angle bend at one end, then bend again and trim to give a small V shape that will act on the rim. To keep the alignment of the V relative to the copper clad when soldering, I put the sheet under the end so I can align the wiper then press and hold to solder.
Here's the front set up.
The middle.
And on the same mouting, the rear. Excuse the particles on the wheel from sanding down the spacer mentioned above.
Heres a view from above. The middle wheels have some side play on the axles to allow movement on the curves, so the wipers are cranked to ensure they don't rub on the back of the flange, increasing friction. The edge of the flanges will be polished on final assembly to ensure smooth running.
To gain clearance for the front pick ups, I had to cut some spaces in the boiler and running plate. The gap further out was to give clearance to the return cranks which were catching the underside of the running plate at the top of the stroke. I wonder if that occurred on the 4mm version?
Wiring it up will be next, the I can give it a test run.
Cheers,
Pete