...The ‘sludge trap’ we speak of was not designed to collect sludge, as some appear to think. It is simply the hole created by the need to drill the crank to get a feed to the big ends, and just happens to get bunged up when using the non-detergent oils...
I can imagine that trapping muck in that drilling was not an original design, but was discovered to be rather good at the job. Later on BSA fitted a removable tube gizmo, which presumably was designed to aid removal of the crap in there.
Anyway, it doesn't matter what we call em, as long as we keep em clean, eh?
It’s the same with ‘freeze plugs’. That one really gets me. They are ‘core’ or ‘welch’ plugs. Manufacturers certainly do not fit them to save owners from their failure to protect against frost. The plugs are there to blank off holes left by the casting process, where sand cores had to be supported in order to create the water jacket.
I've always called them 'Core Plugs', without really thinking about it. Again, the engine makers have exploited an accidental benefit and use soft metal rather than a threaded plug so they do a good job of relieving pressure from ice inside the casting.
