•It is very difficult to change any of these after construction, but it is also difficult to change
the centres of the holes in the coupling rods. You can make the holes bigger but this
introduces slop into the system.
Slide the Mock Axles into the support blocks with the spigot outermost so that they protrude by
the spigot only and lightly clamp using the Hex Allen key in the screws on the top.
Overtightening any of the screws will damage the jig.
Start with the coupling rods. Starting from the fixed centre mock axle, adjust the horizontal
position of the mock axles so the coupling rods fit onto the spigots on the end. (These are
machined to 2.40mm for 7mm scale, 1.50mm for 4mm ). Open out the holes in the coupling rods
to fit the spigot if necessary with either a drill or a tapered Reamer/Broach. Once you have a
coupling rod that fits neatly, use the Allen key to lightly tighten the screws front and back to lock
the position of the sliders. Label one end of the jig ‘FRONT’ and always work with that end as the
front of your loco. Note - The first coupling rod should be assembled face out (Fluted side if
Fluted) and oil boxes uppermost. The second coupling rod should be assembled face in with oil
boxes lowermost on the same settings.
Undo the screws clamping the mock axles and slide them out to about (1 ¼” or 32mm for 7mm)
(For 4mm turn the pin around so that the 1/8th diameter section protrudes by 7/8ths or 22mm)
and re-clamp. Slide 1 set of bearings supplied with your kit over the mock axles then 1 side of the
chassis. Note – The wheelbase between the 1st and 2nd axles may not be the same a between the
2nd and 3rd Etc. So it is important to get the chassis the right way round to suit the way the jig
was set using the coupling rods. Note – The mock axles are a precision ground bar the same
diameter as Slater’s and most other companies axles
•‘7mm’ Scale – 3/16”
•‘4mm’ Scale – 1/8”
If your bearings don’t fit over the mock axles, they won’t fit over the real axles.
File or drill the axle holes on one side of the chassis until they slip over the bearings on the jig
without any force required. Whilst still in place, repeat with the other side of the chassis (chassis
first, bearings second), again opening out the holes so that they slip over the bearings without
force. Using the frame spacers provided with your kit, screw or solder to the chassis. If screwed,
fix to one side first and check the hole at the other side is in alignment before fixing.
I would suggest you now solder the bearings to the built up chassis, taking care not to solder to
the mock axles of the jig (hence the oil or Vaseline). You may need a large soldering iron as the
mock axles will soak up a lot of the heat.
If using Hornblocks, make the slots 0.5mm larger than required to allow the jig to position
them correctly.
Remove the chassis from the jig by sliding it off the mock axles, this may be difficult but move it a
bit at a time on each axles, or release the mock axles from the jig. Do not use a hammer or metal
jaw pliers as you may cause small burrs and hence create bigger problems.
Drill or open out the holes in the coupling rods a little for clearance (I used a 2.50mm drill for
7mm and 1.6mm for 4mm). Follow your kits instructions to fit axles, wheels and motor/gearbox
to the chassis, attach coupling rods.
Testing the Chassis
Undo and remove the front screws clamping the sliders. Release the screws holding the mock
axles and slide them back until only ½” or 12mm is showing. Loosely re-tighten the screws. Slide
over them, one of the rolling road units, and using the front clamping screws to fix in place.
Proprietors P & J Atkinson. The Spinney, Low St, Beckingham, Doncaster, S Yorks. DN10 4PW
