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ArduTank
04-14-2019, 10:22 PM
So, just got myself a 3d printer and decided to have another go at a mech.

Here's some teaser pics of the new legs:

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These are renders, as I'm waiting for the 20+ hr printing process for each tibia.

Yeah, a MP Select Mini isn't very fast. (But it's cheap!)

Will update as I get more done.

Gertlex
04-16-2019, 11:56 PM
Great to see you still have the itch! For the sake of your servos, I would suggest you do some torque calculations to see the loads on your servos with that leg design.

The key number is going to be to minimize the torque around the first servo (femur servo?) after the coax. The peak static torque is going to be (assuming you walk with two legs off the ground at a time) roughly half your mech weight times the distance between the servo's axis and the contact patch (e.g. 66.67 mm in the sketch below). If I want my legs' feet further out from the robot, my best bet will be to increase the distance between coax servo and the femur servo (52 mm below).

As a comparison point, see the compact leg geometry of my in-progress mech:
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While it doesn't reduce the key distance much compared with my first mech, it does reduce the weight of the legs by a servo, and lowers the body height (stability)...
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ArduTank
04-17-2019, 12:05 AM
The intent is to have the femurs sit with the tibia servo flat to the ground, which will adjust the loading angle on the servo you mention to be more of an inline pull and less of a twisting torque. Also to lower the body to adjust for the roughly 180mm long tibias.

cire
04-17-2019, 02:29 AM
Cool, I recently have enjoyed the fun of 3d printing a new mech. So much easier then cutting stuff by hand! Looking forward to seeing it develop.

ArduTank
04-18-2019, 10:04 PM
Well guys. I'm at an impasse. Do I print it in the bright blue, coffee, or yellow gold PLA? Thinking a mix of coffee and gold, but not quite sure.