Coxa length = distance in mm from the coxa servo horn center to the femur (horizontal) servo horn center.
min/max = Looking at servo horn from the top:
Min = counter clockwise rotation
Max = clockwise rotation
Perfect, this is exactly what I was looking for. Thanks!
The cHexInits are correct as well?
I could be completely out to lunch, but I think, the
Coxa length is not the diagonal length between the two servos, but instead just the horizontal delta between the two servos. Also the initY is probably based more on they Y position of the lower servo, ie the delta from the center of it to the bottom of the robot. As for the InitXZ, that is the position that best makes your Hex walk… It does not necessarily have to be at the 90 degree angle… On some robots we found that a single XZ was not optimal for different heights, so I added code that adjusts it depending on what height you wish the robot to be at…
Again take this with a grain of salt.
Kurt
Thanks for weighing in Kurt. On my robot, with what you are describing, initY would be almost nothing, probably less than 10mm. Does that sound right?
And initXZ is still measured from the center of the coax servo to the tip of the foot, irrespective of angle?
As for InitY, I think it is often a little more than the actual minimum. For example if I measure a Phoenix, I think the minimum would be something like 23.5mm and it’s CFG is 25…
As for XZ, Zenta knows this much much better than I do. What I typically try is to sit the robot on the ground, and move the legs in the closest I can where the feet are on the ground and measure that and add a little fudge to it and try to experiment with it there. The one position works well for some robot leg designs, but on others with legs say long tibias, you find that once the robot is a bit more off the ground, that one position is not ideal and the legs look bowed out… So I added the ability to add more XZ values depending on what Y we are asking the robot to be at. I did not do this overly Scientifically, but would maybe put a book under the body and again move the legs to where they could hit the ground at that height and measure again…
Kurt
This is good info guys, thanks. I am thinking of making an info graphic to make this clearer for people designing custom hexapods, but really, how many are there?
Beautiful…
Very nice look.
Perhaps this will help a bit with the theory:
robotshop.com/robot-leg-tutorial.html
The length (L3) which is included in the torque calculation is indeed the horizontal component of the length of the coxa, and is normally quite small.
Thanks for that link Coleman, the images there seem to imply that the L3 is calculated from the center of the bot, rather than from the horizontal hip to the vertical hip servo centers.
Is that the case?
I agree, it really is elegant! 
Thanks guys 
I worked long and hard on the design, pretty happy with the way it turned out. I can’t wait to see it live again!
Update: I got my 645s in the mail today, just pondering the easiest way to put them on…
Yes… not having enough money for 645 is what break me from making an HEX… 
No kidding, Eric. I’ve got 6x645s which I plan to use for the coxas, I hope that will be strong enough. I think my robot is about 4lbs, so from the torque calculations I’ve done quickly in my head it should work ok (I think).
I don’t think the coxa is the most demanding of the 3. In fact i would say it’s the less.
All the weight is on the Femur i think.
Maybe someone can confirm or infirm me here…
Perhaps I have them misnamed. I mean the vertical hip joint. (not sure which of the two hip servos is considered the coxa).
Yep - I think you got it… It took me awhile to get used to those names. I preferred Hip Horizontal, Hip Vertical and Knee and some of the code/comments probably still have that.
Kurt