Tendons and replacement

From Wiki for RobotCub and Friends

1 Tendons
2 Building a tendon (replacement or spare)

Tendons

At the moment tendons can be seen as a sort of mechanical fuses: when stressed with high forces, they break so as to prevent other (more serious) damages to motors, gearboxes and other parts. You can find a list of all tendons length and details on how to replace them at the following wiki page: Assembly instructions. In the present wiki page we describe how to create new cables and suggest the proper tools to use.

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Building a tendon (replacement or spare)

There are three main types of tendons in the iCub. The first type of tendons are used in the bigger joints and are characterized by two crimps on the two ends of the cable. They are typically used in the brushless motor (shoulders, elbows, torso and legs). The second type of tendons are much smaller and characterized by the fact that they slide insdide a tube coated with teflon. They are used to actuate the hand degrees of freedom. A third type of tendon is used to actuate the wrist.

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Material for producing a brushless tendons (crimped)

Replacing a brushless tendon with a new one is not that complicated and can be done by a "non-necessrily-skilled" person. The following is needed:

a little bit of training (if you have an iCub then you have a skilled technician which has been trained at the IIT)
a press with suitable specs: oleodynamic press (15 ton. pressure)
crimps dxf_crimp1 proe_crimp2 proe_crimp3
coated steel wires:
- Producer: Carlstahl. Code: U7191215 stainless steel microcable, costr. 7x19, dia 1,2/1,5 mm PA 12 trasparent coated.
- Producer: Carlstahl. Code: U7191517 stainless steel microcable, costr. 7x19, dia 1,5/1,75 mm PA 12 trasparent coated.
a mold of matrix for pressing the crimps dxf_mold1 dxf_mold2 dxf_mold3

Unfortunately, instructions on how to replace these tendons are only in italian: italianCableManual.pdf but there are nice drawings that can be really helpful shoulderWiring.pdf.

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Material and instructions for producing hand tendons

Replacing an hand tendon is quite complicated and in order to perform a good replacement quite a lof of practice is required. The following is needed:

coated steel wires:
- Producer: Carlstahl. Code: CG077063 stainless steel microcable, costr. 0,63 mm, not coated Carlstahl
- Producer: Carlstahl. Code: U7194561 stainless steel microcable, costr. 7x19, dia 0,45/0,61 mm PA 12 trasparent coated.
teflon tube:
- Producer: Angst-pfister. Product: TEFLON_SHEATH, Sheath teflon Zeus.
tube to be used as a guide for the tendon:
- Producer: Mollifico Astigiano. SHEATH FINGERS CABLES SHEATHS

Instructions on how to replace hand tendons can be found here: tendonsHand2007.pdf

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Material and instructions for producing wirst tendons

Replacing an wrist tendon is modestly complicated. The following is needed:

coated steel wires:
- Producer: Carlstahl. Code: CG077063 stainless steel microcable, costr. 0,63 mm, not coated Carlstahl

Instructions on how to replace wrist tendons can be found here: tendonsWrist.pdf

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ICUB0 cables broken

This is the history of the cables broken while debugging the prototype robot in Genoa. It is here for the records (and affective reasons) since it is no longer updated.