The AP was fortunate that Teletype changed the design of the M15 mainshaft sometime

in the 1930s.  The original design of the mainshaft had the speed change gear between

the two support ball bearings.  This meant that the mainshaft had to be removed in order

to replace the speed change gear.  Removing a M15 mainshaft is not a DIY kind of job.

Pictures of the early design and late design mainshafts are attached.  Note the location

of the speed change gear on the early design mainshaft.  The later design mainshaft

swapped the locations of the big bearing and the speed change gear. 

     Jerry Murphy