Assembly/Disassembly

                Fasteners

Connection Type Fastener Type
To/From AX-12A Servo M2
To/From MX-64T Servo M2.5
Electronics Boards to Acryllic M3
Acryllic Mounting Board to Robot ¼ – 20
4-Bar-Mechanism Joints Shoulder Bolt:
3/16” shoulder diam, .75” shoulder length, 8-32

Motor Orientation         

                It is convenient to adopt the convention of making positive servo rotations correspond with joint extension, and negative rotations result in flexion. The robot can be assembled with servos facing either direction, but it is very important to get the configuration correct. The pictures below are provided as references.

     Front Legs

The white arrows represent the direction of positive rotation, which is defined as the vector coming out of the servo front (the side with the actuated horn and model number plackard).

12

 

 

       LH and RH as seen from the back

Motor orientation can be determined by noting the presence or absence of the model plackard in the picture (it’s only on the servo front), as well as the direction of TTL plugs on the MX-64T’s (they point the same direction on both sides, and thus can be used to determine the motor orientation).

IMG_146613

 

Assembly

*****When placing horns onto the MX-64T servos, be sure that they are properly aligned. There are three dots in the shape of an isosceles triangle (or arrow) indicating the direction of the horn. This arrow should align with a notch in the output shaft of the servo. When connecting the frames, they should align with the arrow on the horn (the 3-dot arrow should point directly up at the center of the frame.

*****The same applies to the AX-12A servos. They come with horns on them already, but their horn direction is indicated with a single notched line along the width of the horn.

*****ignore the orientation of servos in the solidworks drawings, but instead refer to the pictures above.

14

Front Leg (from scratch)

***green connectors are numbered F1-F5 from most proximal to most distal

***Ensure that servo orientations match the above figures

***Ensure that the servos are wired BEFORE these attachments are made, as many of the wire terminals are no longer accessible once the leg is assembled. This is especially important for the ThC2, ThC1, ThC3, and CTr joints of this leg.

  1. All of the horns can be placed on the MX-64T servos if they are not there already
  2. Place M2 nuts in the back of an independent AX-12A frame. They should sit in snugly. If you are having trouble, tightening a screw run through them can be used to pull them tightly into their countersunk indentations.
  3. Attach this frame to the ThC2 servo
  4. Attach F1 to the ThC2 servo’s frame, ensuring that the ThC2 servo is oriented correctly.
  5. Tape M2.5 nuts into the slots of the ThC1 MX-64T servo (ensuring that you place them on the proper side so that the servo will be oriented correctly).
  6. Attach this servo to the connector to join the ThC2 and ThC1 servos.
  7. Place M2 nuts in the back of an independent AX-12A frame.
  8. Attach this frame to the ThC3 servo.
  9. Attach F3 to the frame of the ThC3 servo.
  10. Attach an MX-64T frame to F2.
  11. Attach F2 to the ThC3 servo.
  12. Connect this frame (step 10) to the ThC1 servo.
  13. Tape M2.5 nuts in the CTr servo’s slots.
  14. Connect F3 to the CTr servo.
  15. Connect F4 to an MX-64T servo frame
  16. Connect this frame to the CTr servo.
  17. Connect F4 to an the FTi servo.
  18. Connect F5 to an AX-12A frame.
  19. Attach this frame to the FTi servo.
  20. Attach the ThC2 servo to the prothorax mounting point.

15

Middle/Hind Leg (from scratch)

***green connectors are numbered H1-H5 from most proximal to most distal

***Ensure that servo orientations match the above figures

***Ensure that the servos are wired BEFORE these attachments are made, as many of the wire terminals are no longer accessible once the leg is assembled. This is especially important for the CTr, TrF, and FTi joints of this leg.

  1. All of the horns can be placed on the MX-64T servos if they are not there already
  2. Tape M2.5 nuts to the underside of H1 in their countersunk holes.
  3. Attach H1 to the ThC3 servo.
  4. Attach an MX-64T frame to H1 ***washers may be necessary to prevent bolts from contacting the surface of the ThC3 servo.
  5. Attach this frame to the ThC1 servo.
  6. Attach an MX-64T frame to H2.
  7. Connect this frame to the ThC3 servo.
  8. Tape M2.5 nuts into their slots on the CTr servo.
  9. Attach H2 to the CTr servo.
  10. Attach H3 to an MX-64T frame
  11. Attach this frame to the CTr servo.
  12. Attach H4 to the TrF servo.
  13. Attach H3 to the TrF servo.
  14. Connect H4 to the FTi mounting accessory.
  15. Tape M2.5 nuts into their slots on the FTi servo.
  16. Connect the FTi servo to the mounting accessory.
  17. Connect H5 to an MX-64T frame.
  18. Connect this frame to the FTi servo.
  19. Tape M2.5 nuts into their slots on the ThC1 servo.
  20. Attach the mounting adapter (AKA “piano”) to the ThC1 servo (not shown)
  21. Attach the mounting adapter to the thorax.

Removing Horns

Hopefully there is never need to remove the horns from the servos, as the process is difficult and hard on the servo. However, the horns should be removed before sending servos back for repair, and may need to be removed to check their alignment should the servo consistently go to seemingly incorrect locations.

The free-wheeling back-side horn can be pulled off directly. This can take some force but is not a problem. My method for removing the front (gold) horn is to slide a dime between the horn and the servo at the top. This may require some (very gentle!) taps from a hammer. Some of the dime will still stick out, which can be used to rotate the dime around, the full horn circumference. Alternatively (if the servo works), you can hold the dime in place and command the servo (via dynamanager) to spin fully around to pull all sides of the horn away from the servo. This process can then be repeated with a quarter, and then a nickel, at which point it should slide off the rest of the way without too much force.