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chip updates: initial leg designs for cable drive test [updates]

So as we mentioned before, we'll likely build one leg or part of one leg and then move onto other parts of the design. On the train we kinda figured out the whole cable drive situation and we were moving onto CAD'ing the whole design. It took some time to CAD the design b/c it was a little harder to figure out where to put things and how to orient them than we though, but here's an initial design in CAD.


There are some key features in this design to point out. First, is the location of the bearings on the lower leg which are pushed inwards more than the ones on the upper leg. This is to minimize the distance between the upper and lower leg in the folded position.


Also note the extensive use of lightening holes on all parts of the design. The goal is to keep the design very light but also provide flexibility for Churro mounting locations as those may change depending on where we feel support is needed during assembly.

We're using gold color Churros, and brass washers to maintain a somewhat aluminum and gold color scheme that's similar to what is used on NASA robots.


Then I think the last thing to note would be the new Manfrotto carbon fiber legs which are stronger but lighter and slightly shorter than the previous legs. The shorter legs allows the leg to unfold a little more naturally. The previous lower leg was too long and this caused issues in the kinematics when raising and lowering the platform.



** UPDATE ** Maybe we will test with the current CF leg to save ~ 25 dollars and if that's too long we will move to the Manfrotto leg b/c that saves us ~ 3 inches. 


The plan is essentially to build a single one of the above (this is 1DOF) and then deal with the ab-ad joint later if this works well. If it doesn't we won't have wasted much money or time.



Things we need:


(3x) pack of deep-groove bearings (https://www.amazon.com/gp/product/B012KKTBRU/ref=ox_sc_act_title_2?smid=A1HTURR3TNQJ53&psc=1)


(1x) pack of flanged bearings (https://www.amazon.com/gp/product/B07Z3F68H4/ref=ox_sc_act_title_1?smid=A1THAZDOWP300U&psc=1)


(1x) Manfrotto tripod leg (https://www.amazon.com/Manfrotto-Extension-Professional-Mirrorless-Photographers/dp/B08SMQ37LF/ref=sr_1_10?dchild=1&keywords=carbon%2Bfiber%2Bextension%2Bpole%2B10%2Bin&qid=1622817217&sr=8-10&th=1)


(1x) pack of M4 brass washes (https://www.mcmaster.com/98691A114)


(1x) pack of M8 brass washers (https://www.mcmaster.com/98691A117)


(4x) #10-23 1 1/4" stainless-steel standoffs (https://www.mcmaster.com/91075A024)


(1x) AndyMark Gold Churro 36 in (https://www.andymark.com/products/1-2-in-churro-different-length?quantity=1&Color=Gold&Length=36%20in.)


(1x) 24" x 24" x 1/8" 5052 Al stock for water jetting, sandblasting, bending


(1x) 3D printed pulley (still need to design)


(1x) pack of string for the joint motions (still need to find the cable we want to use!!!)


We'll start ordering this stuff this weekend so we may be able to assemble within the next few weeks.


#updates #omgrobots #yay #built_by_nerds

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