SHJ: I may be wrong, but the Shack at the GAM did not look, to me at least, when I visited there in May 2011, like it was capable of running any of its engines.
PAXboy: a former crew member on the Coventry Shack (which recently taxied under its own power) explained it to me like this; the only way the designers could harness the tremendous power of the Griffons(?) fitted to the Shackletons, was to use two (necessarily contra-rotating) propellors. He said that if a single prop had been used, it would have had to be so large that its blades would have fouled the ground, without absurdly extending the undercarriage.
I repeat the above however, as definitely a non-engineer; and on another forum, where I put up this explanation, someone asked how then did Corsairs and Mustang harness 3000 bhp in the Reno races, using a single prop? I just had to say I didn't know.
ie could someone with engineering expertise please definitively (if possible) explain?
MTIA