More Frames

Things have been fairly busy for me over the last couple of weeks but I have managed to make some progress on my NSWGR (Z)20 class in 1:43.5. While things are moving more slowly than I’d prefer, I thought it would be worthwhile to do a blog update as I’ve now taken what I consider to be an important step. Before getting down to a detailed description I feel I should mention the range of Greg Edwards Data Sheets available to local Australian prototype modellers. Without this resource I’m not too sure such a project as my scratchbuilt 20 would be achievable. While the sheets are made available as standard in HO scale, they can be purchased in 1:43.5 if you contact Greg via the link. Buy the sheets if you’re building models and support Data Sheets. It’s an extremely worthwhile service.

This is a fairly low quality scan of the plan I'm using from the extensive Greg Edwards range of plans. I've overlaid this plan with some basic dimesions that I've used to order parts from UK suppliers to give them an idea of the spaces available.

This is a fairly low quality scan of the plan I’m using from the extensive Greg Edwards range of plans. I’ve overlaid this plan with some basic dimensions that I’ve used to order parts from UK suppliers to give them an idea of the spaces involved.

After making some slight adjustments to a slice from the above plan and using this as a cutting guide to allow me to produce the frames, I glued the appropriate part of the plan to the .7mm thick nickel silver sheet I’m using to make the frames and cut them out. I detailed most of this in my last post. I completed the cuts over a week ago and then I started doing some evaluation of things like the motor/gearbox combination I’d planned to use and what other materials I wanted to use in this part of the project. I had a Slaters motor/gearbox combination on hand but I came to this conclusion that this was too big for my 20 class. I visited the website of the UK firm ABC Gears and made contact with them to see if they could provide me with a motor and gearbox to suit my needs. I sent them the above plan with the dimensions overlaid on it and the proprietor got back to me and recommended one of their Mini-S gearboxes and I chose to go with a Maxon coreless 2.5W motor. I’ve read rave reviews of ABC’s products and the slow speed running of the Maxon motors is second to none, so I’ve heard. So I can’t wait to test these claims out and decide for myself. I’m assured that these motors are suitable for DCC. I also purchased some more NS sheet in various sizes from Eileen’s Emporium, purveyors of all things useful for the model railway hobbyist.

Over the last few days I completed the frames by drilling a series of holes where the brake hangers would be located and the Slaters plunger pickups.

This photo shows the frames separated and cleaned up: I've removed the paper plan overlay, filed off any stray solder and cleaned up the surfaces with wet and dry paper (600-1000 grit).

This photo shows the frames separated and cleaned up: I’ve removed the paper plan overlay, filed and scraped off any stray solder and cleaned up the surfaces with wet and dry paper (600-1000 grit). The large holes are for the pickups.

After some measuring and figuring I finally cut out the rectangular slots for the horn guides I plan to use. I have decided to stick with the Hobby Holidays ball race guides but found that these need a 10.5mm wide slot to allow the ball races to move up and down. This amount of gap is considerably wider than the prototype slot and in spite of being careful I seem to have miscalculated the amount of material I cut from the surrounding area of one of the slots (the one on the right in the photo). As a result one of the slots has thinner projections at the base of the slot than would be ideal. This will be behind the wheel and really won’t be apparent on the finished model, but I’d have preferred if they all looked the same.

Before separating the frames I decided to mill out the edges of the slots. All three were slightly under width (from .5mm to 1.2mm too narrow) but this was deliberate as it’s easy to remove material, much harder to add it back on after you’ve cut too deeply. I could have done this final removal and clean up with a file but it was a simple matter of attaching the frame sandwich to a block of wood using self tapping screws (utilizing the holes I’d drilled for the pickups), bolting this to my mill bed and accurately milling them out. It took all of five minutes to do this job whereas removing 1.2mm of material (about .6mm either side of the slot) from just one of the slots would have taken considerably longer.

Once I got this work completed it was finally time to separate the frames. In my last post I seem to remember saying that I’d “tack soldered” the long, straight, top edge of the two frames together. I used just a little flux and a small amount of solder. Well I also used my 80W soldering iron and I’ve discovered that solder loves NS! In past projects, after cutting out the shapes needed in the frames, I’ve been able to separate the frames using a bit of simple pressure from a Stanley knife. Not this time! The solder had migrated wonderfully well between the two halves and the only way they were coming apart was with plenty of heat, applied with the same 80W iron, and a bit of heavy pushing with the Stanley blade. In the end the halves separated but I’ll be a little more judicious with the solder next time 🙂

After applying some rivet detail to the frames the next step will be the cutting of the frame spacers out of more NS sheet. I’ll probably use some more .7mm sheet but I may decide to go with something thinner, say .55mm. This will make the bends I’ll incorporate into some of the spacers easier to make. I’ll do some testing and decide what I want to use when the time comes. I also need to check all my calculations around what width the spacers need to be before I make the cuts. At this stage my calculations say they need to be 19.2mm wide but I may vary this ever so slightly. I’ll make those checks as the time for cutting approaches, possibly over the coming weekend.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s