DEC RD53 hard drive

I pulled out my DEC RD53 for testing the archiver and surprise the heads were stuck. I opened it and freed them but wasn't able to find the bumper that is the cause of the problem. I put pictures here. http://www.pdp8online.com/rd53/rd53.shtml Does anyone on the list know where the bumper is and can say in relation to my pictures? The first drive hasn't restuck so far but I have another to do. Also does anyone know the data format for the stuff the RQDX3 puts on the first few tracks? I think its the sparing information and other disk organization information. If it wasn't too hard I was going to see if I can convert my extracted data to an image usable under SIMH. The low level format is strange. The first 3 sectors on track 0 are in one format then 3 track worth of sectors with a different CRC code which is where I suspect the controller is storing its stuff. Also some funny stuff at the end of the disk.