Posted by Jon on May 03, 2006 at 15:31:16 from 199.159.117.62 user Jon.
In Reply to: Re: Valve Gear was Thorpe Station - engine changing posted by Owen Roberts on May 03, 2006 at 13:41:57:
Presumably as the centre driving wheel has to handle the direct load from the piston driver rod and transfer it on to the outer wheels. The centre one is thus under more stress than either of the outer two, thus needs to be more robust. Making the outer wheels spoked reduces the burden they put on the centre wheel, and the greater mass of the centre wheel also adds to its inertia.