Saturday, 8 August 2015

A Terrier for Freshwater

As anyone who has seen my layout at exhibitions can tell you, so far some very unlikely motive power has been operating the Freshwater line of the Isle of Wight. I do intend to rectify this, but getting the layout operating smoothly, and scenery added were higher priority. I have acquired some Dapol A1X Terriers (one at least with the correct extended bunker) ready to be converted to 2mm finescale. Many months ago I started work on modifying the original chassis, as per an article in the 2mm Scale Association magazine. I even 3D printed some replacement gears incorporating axle muffs, to replace one of the originals that I ruined while reaming the centre hole. The hole had drifted off-centre. Just a couple of weeks ago, I had the chassis running, although its starting speed was about 40mph. I even got as far as connecting a small DCC decoder, and this actually improved it, with much better starting and stopping. However, electrical pickup was still a bit hit and miss.

Then, the long awaited replacement chassis etches appeared on the 2mm shop lists (3-661). A couple were ordered. There are no specific instructions for the Terrier chassis, just the generic build instructions, plus a couple of drawings hidden away in the 2mm VAG files area. After a couple of emails to Chris Higgs,I put together a parts list:
  • 6x crankpins and washers (3-107 & 3-109)
  • 1x 30:1 worm and gear (3-364)
  • 2x gear muffs (3-102b)
  • 2x axle muffs (3-100)
  • 1x 14 tooth M0.3 gear (3-390)
  • 1x 22 tooth M0.3 gear (3-394)
  • 6x 8mm driving wheel (3-005)
  • 8x frame bushes (3-113)
  • PCB strip (3-156)
  • Nigel Lawton 8mm dia x 16mm Midi Motor
The Terrier chassis etch has some differences from the other chassis etches:
  • There is no fold up gearbox for the worm assembly
  • There are frame reinforcers to be 'sweated' to the insides of the main frames to strengthen them.

So, for my first evening working on the chassis, I started by folding up and soldering the chassis building jig. With luck it will survive long enough to be used for the second chassis.

Then I started on the chassis frames. Unfortunately, the reinforcers are not arranged on the etch as a 'fold and align' arrangement like the coupling rods and bosses are, but need to be cut out separately before attaching to the main frames. Where the idler gear axle bush cutout is on the frame reinforcer, it dissects the top edge leaving a very thin piece of metal keeping the two ends of the reinforcer together, so must be handled with care. It might be possible to use some fine rod in the brake gear holes to align the reinforcer and the frame when soldering them together, but the rod would probably get soldered into the holes at the same time. I therefore aligned them by eye. Alignment needs to be accurate, or the frame bushes will not locate properly into the frames.after sweating them together, I inserted the frame bushes into their holes and soldered them in. The holes needed to be reamed a little to get them to fit. This requires a slightly larger reamer than found in the usual, cheap reamer sets.

The PCB tabs were then folded at right angles. The tabs with holes in, I folded along the wrong fold lines, so I will have to rectify this later. The frames were then fitted into the jig, and axle rod inserted, as shown. This completed the evening's work. Next time, the PCB spacers need to be added, then I can try it with wheels and gears, and add the coupling rods. Then I have to ponder fitting the motor and worm.