Combines Knock in Drum on 7720

It sounds as if you've broken the weld at the center hub of one of the cylinder spiders. This can slip sideways and if one of the cylinder bars is bent a little bit, the opposing (usually) cylinder bar can contact the rear beater. It's also posible that if the machine slugged hard enough that you've put a twist in the cylinder bars, since all but 2 of the 6 spiders are floating on the shaft.

does this happen with the header off,or on.could be a broken weld on spider,bent rasp bar or bearing out,bent beater bar.lot of things can cause it. If it only does it with header on make sure elevator chain didn't jump a tooth on the sprocket. Post back with the problem when you narrow it down.Please

Found the problem. The spacer disc between the shaft and the barrell of the beater has a fracture in it at the right hand end of the beater. The pressure of the plug forced the barrell out of plumb. It means a new beater ! Thanks guys!