A recent thread on the Scalefour Society Forum has reminded me that there is a much easier solution to the ‘side-play on the middle wheel’ problem. On the original full sized coaches the springs for the centre axle were supported in long j-hangers with either with links or rods and rubber secondary springs. The axleboxes were modified so they and the axle could move axially in the w-irons. We can’t actually make the axleboxes move like this on models but we can get very close to it. This is how:-
A pair of wheels, almost any make will do.
A length of brass tube 2 mm OD x 1 mm ID x 22 mm long, for P4 or EM, or 20 mm long for OO
One ExactoScale pin-point axle 1mm diameter
Cut the tube to length and make sure that both the outer an inner edges are well de-burred.
Remove the wheels from their axle and mount them on the brass tube. Check and adjust the back-to-back.
Slip the mounted wheels onto the 1mm axle and mount the combined axle in the sprung w-iron in the usual way.
There you have it. Quick, simple and without the usual contraptions or inside bearings. THis method will give enough side-play for your six-wheeler to go round any curve which doesn’t produce buffer locking.