The Siren Board

Hello everyone, I have recently been trying to figure out how to replace the bearings on my Federal Sign and Signal model 5. I have not been able to get at them though. I tried to take the motor apart by removing the long screws at the bottom of the siren, but it did not seem to work. The bottom motor cap only spins around but does not want to pull off. I have also tried to loosen the motor brush holder attached to the shaft. That also did not seem to work. Just wondering if anyone knows how to get to the bearings at the bottom of the motor. Thanks.