I wonder if the shaft and the crank arms are not fitting properly. I retained the previous Raleigh shaft when I put on the Rudge crank arms, and there may be a small difference in diameter. I may end up swapping the shafts between the Raleigh Super Course and the Armstrong today. At any rate, I'm planning on removing the bottom bracket for an inspection. Hopefully it's just a bad ball bearing. I won't figure it out by speculating though. Time to break out the spanner wrench.