Tractor Repair: 1920 ford, clutch disk, center hub

Question
I have a 1920 ford tractor,it has shuttle shift,when I start the tractor put in gear let out partially on the clutch the pto works but when I let out all the way on the clutch the tractor does not move.I can while the tractor is running and clutch is out can move the gear shifter to any position with no gear grinding at all.I checked the axle speed lever and made sure that it wasn't in neutral also.is there any safety feature on it that could cause this.
Thanks

Answer
  Hello,

  No, there is no safety feature that that would cause it not to move.  If you can move the shift lever with the clutch pedal released, and the gears don't grind, the transmission is not turning at all.  If you've already verified the range lever is in gear, make sure you have a small amount of clutch pedal free travel so the pedal has to be pushed 1/2 inch or so before it feels like it's doing anything.  If you don't have free travel, adjust the pedal linkage so you get it.  If that doesn't solve the problem, it's possible the splines in the center hub of the clutch disk are  stripped or the rivets are sheared off, or the input shaft is stripped or broken.

                        Arnie