Dad,
Q1 won't follow the same pattern. It's not completely obvious, but the wheels are actually very different. On a Q1 they were designed to be fabricated, based around welding sections into a pressing that could be produced using equipment the loco works had in their boiler shops (they were an austerity design after all). It appears that some/many/all later received cast wheels (i.e. genuine Bulleid-Firth-Brown, where Firth-Brown was the casting foundry). But this is why the wheel face is proud of the rim/tyre, not behind it. So, the Q1 has largeish sections welded into the lightening holes in the wheels with lead poured in, rather than what's been shown above.
The balance weights in BB/WC and MNs are far from universal. What's illustrated here is the result of trials and the decision to add dynamic balancing (for the coupling rods) - one assumes to reduce hammer blow on Eastern Section bridges! The connecting rods and lack of return cranks/eccentrics with chain-driven valve gear statically balance as they're 3-cylinder locos. All the holes would have been there as the wheels were cast, otherwise the cores needed to produce the hollow sections in the wheel would have been unsupported when casting.
Steph
