The reason for the unusual noise from the B-36 was that the propellers were naturally set at right angles to the fuselage but the wing trailing edges had a small amount of sweep, this caused interference between the wing wash and the propeller rotation. It caused a lot of problems during development and early service and also led to the replacement of the original hollow prop blades with solid blades to alleviate the many cracked blade roots that were suffered.
The prototype aircraft did not use a bogie undercarriage, instead there was a single 110" diameter main wheel, the runway loading meant that there were originally only 3 runways in the US that could take the loading applied by this large wheel. That was the reason why production aircraft switched to a bogie undercarriage so that the runway loading was reduced.
I have a book about the P&W R-4360, it is absolutely fascinating and stands as a testament to these last developments in radial piston engines. There are some interesting stories in it, but the thing that amused me is the comment from someone who used to work in the maintenance side of an airline that used the Boeing Stratocruiser about the way that an engine could be in perfect condition on shut down and then be broken when it became time to restart it. A very complex beast.