Lateral location of the swinging fork is provided by the (chain-side) left-hand bearing assembly: the right-hand bearing floats in this direction. Note that about the only loads that these bearings carry, are from chain tensions (unless a sidecar is fitted).
The number of rollers in each bearing is 11, of nominal 1/4" x 3/4" dimension. (A reminder: all dimensions here are Imperial, not Metric!)
These bearings should be shown a grease gun regularly, not to prevent wear, but to provide weather-proofing.
Being a perfectionist, I departed slightly from Granshaw Bradville's original design, in that I brazed short lengths of 3/4" x 1/2" tube into the power unit rear support plates, to distribute the load to the transverse carrier-bolt a little better. Two spacer tubes were then tailored up, so as to confer optimum alignment to the rear-drive sprockets. (The third spacer, between the two support plates, doesn't affect this alignment, of course).
The total between-lugs width of my frame was 9 7/16": I needed to insert a packing washer (twixt RH bearing and frame lug) of about 1/16" thickness.
Written by Paul Button