Most rotating electrical equipment (AC/DC motors, generators, alternators) have a fairly healthy short term overload capacity. This is mostly determined by the thermal mass of the windings and the motor case. IIRC the GG1's could run at about 150% overload for several minutes while accelerating a train out of a station. This is one of the advantages of "electric automobiles", you can accelerate to beat the band for a short time and then let the ample cooling air get the temperatures back to comfortable levels.

Bearings should not be an issue by themselves, if someone had a poorly maintained dynamo with shaft misalignment, seal leakage (spurting steam/water into the bearings) a dynamo may fail early just because it get's more long term accumulated load from a radio.

As long as the radio has a duty cycle of about 5 minutes per hour (5/60 = 8%) you should be fine. In the off case where the dynamo can't keep up you may have to turn off some other loads (gauge lights, etc.). Or add a battery (with associated charging electronics). The dynamo is not the problem.

Good Luck, Kevin

I don't know. I tried to look at that web page but it was about the clunkiest I've ever seen and I had doubts whether it was legitimate. Yesterday I looked at the our receipt from 3 or 4 years ago and there was no mailing address, web address, or email, just the company name. We bought 10 of each at about $14 for the 3 watt bulbs and $17 for the 5 watt bulbs. A word to the wise, don't connect them to a 110v socket. Don't ask how we know this.