[woodcote]

Spacing the armature is a good idea to keep the brushes nicely seated and the stacks central in the magnetic field. However, you want the armature to spin perfectly freely, so it's best to check without magnets or brushes fitted.

In something like a Tyco 440X2 where the chassis / bulkheads are a bit flexible, you don't want it too tight because the bulkheads will move and the armature assembly will bind - especially as there's no separate bushing. In a higher-quality Wizard chassis, it's possible to space the whole arm so there's 0.005" or less front-to-back movement.

Wizzard produce spacers in various sizes from 0.003" up to a 0.023" brass armature spacer. I keep a stock of 0.005 and 0.010" brass, 0.020" stainless steel and 0.010" nylon - used for axle and armature spacing. I always put a nylon spacer in front of the commutator and behind the armature stacks to isolate everything nicely. Normally on a Wizzard, I'd have a 0.020" stainless steel spacer at the rear, with brass spacers front and back to adjust the position.

Hope that helps.