User manual

Barrett Technology, Inc.

BA4-310 System User Manual Version 1.1

[ ] 9.

Finally, tension the cable circuit by adding a pre-tension slightly less than ½ the 1

stage cable’s breaking strength. This is accomplished by applying 0.68 N-m [96 oz-in]

to the lubricated pre-tensioning set screw using the torque driver provided with your

system, running the joint through its full range of motion, applying the specified torque

again to remove the new cable slack, and repeating this process until moving the joint

no longer reduces the tension in the cables (

i.e.

the full pre-tension has been propagated

throughout the cable circuit).

5.4 Differential Output (J2 & J3)

The differential output circuit consists of four cables riding on four different diameter steps

coupling the large input pulleys to the smaller output pulley. The four cables make up two

circuits, each of which is tensioned with a worm tensioner integrated into the input pulley set.

[ ] 1.

Begin with the Level #1 differential cable. Insert one end of the cable into the

termination in the smallest diameter step of the output pulley. Bring the cable around ½

a turn, then transition onto the smallest step of the left input pulley which lies in a plane

90° to the mating output pulley. This will require you to move the output pulley against

one of its motion stops and thread the cable between the input and output pulleys using

a termination to pass the lug through the narrow gap.

TIP: Wait until all 4 cables are attached to the output pulley before inserting lugs into the input pulley terminations. This allows

free rotation of the output pulley when passing termination lugs through the narrow gaps at the input and output pulley tangent

point.

[ ] 2.

Put one end of the Level #4 cable into the termination hole in the largest step of the

output pulley. Go around the step and the wrap onto the left input pulley’s largest step

(this pulley “step” or surface will carry this output cable as well as a stage 2 input

cable).

[ ] 3.

Repeat steps 2 and 3 for the Level #2 and Level #3 cables on their corresponding input

and output steps on the right side of the differential.

[ ] 4.

Rotate the input pulleys as necessary to secure the free end of each cable in the

termination for its input pulley step. Temporarily tape the differential cables in place to

ease pre-tensioning.

NOTE: Each input pulley is made up of two concentric parts coupled only by the pre-tensioner. The two pulley parts can be

counter-rotated to change the distance between terminations and later, to add pre-tension to the differential output circuits.

[ ] 5.

Insert the pre-tensioner worm into each input pulley and tighten with a 3/32” hex

wrench until proper pre-tension is added to the differential output cable circuits. The

cables should be difficult to pry off of the input pulley steps even when a wedge is used

as an aid (approximately 208 kgf (450 lbf) of tension in each cable).