Thanks to Dick Smith for contributing the following memories of how the North London banking was built in the 1960s.  

It was the intention to do fancy things with the wood like steaming it or cutting slots in the back. People who saw the track will remember it was more than 180 degrees so the straights leading up to it converged rather than ran parallel, so it was cut and routed flat with the straights parallel. We also attached as much straight as possible to it, about 6-8ft, before we tried to bend it. The bend was cut out of one piece of chipboard and I expect we made it as big as possible. If it was cut out of a piece of 6x8 the radius of the outside edge would have been 36" which gives an inside radius (3.5" lane centres) of about 22". From memory and looking at the photo this seems about right and seems bigger than the example in your article (Jim Schnider's track).

The plan was to bend it and screw the ends of the straights flat to a solid batten glued with copious amounts of Cascomite wood glue, of which we seemed to use copious amounts in the tracks construction. Incidentally this is why the R shaped bend before the drivers rostrum was called  "Cascodes" a typical Tony/Dick corruption based on full sized racing (Cascades at Oulton Park) and shared mad experience.

When the night came to bend the banking we did have a sort of Spanish windlass rigged up, but it the end I think we just decided to see what happened if we tried it without any fancy treatment and just pushed it, lined it up with the other sections and flattened the ends of the straights and screwed them down. I remember we were all somewhat surprised how easy it was. It was then just sat on its supports and allowed to settle.

It was never a flat out banking of course and there was a record for how high up the wall after launching, but I can't remember it causing  huge problems. I think it was built in about 1967 and I last raced on it at an open meeting in about 1980 and it didn't seem to have warped at all. The Church Farm clubroom was dry and heated so it was not exposed to damp or large variations in temperature.

Dick Smith

See also The Story of the North London tracks - the banked bend can be seen in the photo of the 1967 track, unfortunately the degree of banking isn't that obvious from where the photo was taken.