Elbow Gear Ratio/Design

[wilton-lee]

ELBOW
Required Torque: 32 N-m
Desired Gear Ratio: 5:1

• Input Pulley: HTD5M-16T-15W-10BD (15mm width, 10mm bore, 4mm keyway)

• Output Pulley: HTD5M-80T-15W-10BD (15mm width, bore N/A)

• Belt - length TBD

Pricing:
Input Pulley : $6.99
Output Pulley : $37.19

[kammce]

Looks good to me. I'm wondering what we can do to mount the driven pulley to the arm's elbow? Do we do something like drill 4 holes into it so we can screw it into the elbow?

[wilton-lee]

Yeah that was our plan, which is why I wasnt worried about the bore hole for the larger pulley.

…

On Tue, Dec 1, 2020, 9:10 AM Khalil Estell ***@***.***> wrote: Looks good to me. I'm wondering what we can do to mount the driven pulley to the arm's elbow? Do we do something like drill 4 holes into it so we can screw it into the elbow? — You are receiving this because you were assigned. Reply to this email directly, view it on GitHub <#141 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AF7AWV6UT2OMJDEB6F6BPADSSUPQPANCNFSM4UIOG7GQ> .

[kammce]

Awesome, sounds good to me then.

[wilton-lee]

With the reduced torque requirement if we lift the 5kg at an optimal trajectory, we could theoretically use a smaller pulley on the elbow too. Having an 80T gear on the elbow is kinda bulky if we don't need that gear ratio.

[kammce]

With the reduced torque requirement if we lift the 5kg at an optimal trajectory, we could theoretically use a smaller pulley on the elbow too. Having an 80T gear on the elbow is kinda bulky if we don't need that gear ratio.

True, but then we would add another component to our BOM count. I think it is totally responsible and correct to reduce the gear size for elbow in general because we don't need the added torque. But, if the design looks a bit clunky you can UN-clunk-it aesthetic wise by simply making the elbow joint metal area as wide as the gear. Then you have it taper down to the wrist required lengths as it is now. You could do a similiar thing with the shoulder too, but I don't think it looks too bad. Widening up the elbow area may be required anyway because the wrist RMD-X7 motors are going to be moved closer to the elbow area and drive the diff gearbox using pulleys, to bring the CG back towards the base of the arm.