Frame ID documents

[motorpickle]

Is there any documentation about the year that the side car loops forging started the welded "dimple" about 3/4" below the upper tube joint? It seems to be quite evident on the 1947 UU frames. I do not see it on the 1946 bullneck frames I have inspected. Is this dimple totally incorrect for all 1941-1945 big twin frames? Is there documentation to back this up? Is it a reason for dis-qualification according to AMCA floor judging? I am really interested in verified original condition frames(in or out of motorcycles) from the 1941-1945 era that either have the welded dimples or do not. Hard core facts are appreciated, speculation is anticipated, and BS is thoroughly unavoidable!!!! Have at it experts!!

[bmh]

The dimples you refer to are the fit up welds that were done on the assembly jig. there was about a 3/8" hole drilled through the forging so the part could be spot welded in place during assembly. The complete perimeter welds were done after the frame was removed from the assembly jig, before final alignment. You should not find them on frames that still used brazed connections at this joint. I don't believe they welded any frame components prior to WWII. Frames were totally heli-arc welded by the 48 model year. The years in between had a mix of brazed and welded construction. Steve Little most likely knows exactly what and when, if he doesn't comment here you should get in touch with him.