Torque tubes and manufacturing methods thereof

A vehicle (104) comprising:

• an apparatus (100) comprising:
• a first end fitting (110a), comprising a tube engagement portion (112), wherein:
• the tube engagement portion (112) comprises an outer coupling surface (114),
• all contours of the outer coupling surface (114) are smooth, and
• the outer coupling surface (114) comprises at least one first concavity (124) and at least one first convexity (126);
• a second end fitting (110b);
• and
• a torque tube (130), comprising a first end (131a) and a second end (131b);
• and
• wherein:
• the first end (131a) of the torque tube (130) is coupled to the first end fitting (110a);
• the second end (131b) of the torque tube (130) is coupled to the second end fitting;
• the first end (131a) of the torque tube (130) comprises an end fitting engagement portion (132);
• the end fitting engagement portion (132) comprises an inner coupling surface (134) conformed to the outer coupling surface (114) of the tube engagement portion (112) of the first end fitting (110a);
• all contours of the inner coupling surface (134) are smooth,
• the inner coupling surface (134) comprises at least one second convexity (174), complementary to the at least one first concavity (124) of the outer coupling surface (114) of the tube engagement portion (112), and
• the inner coupling surface (134) comprises at least one second concavity (170), complementary to the at least one first convexity (126) of the outer coupling surface (114) of the tube engagement portion (112);
• a drive unit (102), coupled to the first end fitting (110a);
• and
• a driven unit (103), coupled to the second end fitting.