Stewart Sound Chassis
Installation in Athearn Genesis and Athearn RTR F units

F-3, F-7, F-9 Sound Chassis

With Black Side frames & Lok Sound Installed
#691-1201 F-A Unit Dummy
#691-1202 F-B Unit Dummy
#691-1203 F-A Unit Powered
With Silver Side frames & Lok Sound Installed
#691-1205 F-A Unit Dummy
#691-1206 F-B Unit Dummy
#691-1207 F-A Unit Powered
#691-1208 F-B Unit Powered

Athearn Genesis and Athearn RTR F Units - installation notes
Genesis: Remove the inside windows, carve a little plastic for the
coupler box clearance (rear) and cut off the Stewart brake shoe on the front truck.
RTR: Carve a little plastic for coupler box clearance (rear)

Both: The body will rest on the mechanism. I have not found any method
to use the Genesis inside windows to hold the mechanism.
The RTR version does not snap on either.
See pictures below.

Photo below shows the front brake shoe trimmed away Athearn Genesis only

Carve plastic under the door to clear the Stewart coupler pocket

Photo below shows the plastic carved away.

Photo below is with the Stewart chassis in a Genesis Body Shell

Photo of Athearn RTR body - carve our for coupler pocket

Photo of Athearn RTR with the Stewart mechanism installed