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Reece posted an update 3 years, 3 months ago
In lockdown (again) so am returning to this project (again). Been working on my two actuator neck mechanism. Installed continuous rotation servos (forgetting how they operate and tested. Result, broken neck.
Reece posted a new activity comment 6 years ago
Hi CArLa, This is definitely not a project for a beginner!
Hi Nabeel, To get CAD files you pretty much have to reverse engineer them for your self. I\’ve been working on mine (on and off) over the last three years (using Onshape).
Reece posted a new activity comment 8 years, 10 months ago
Nice, nylon for the gears and splines should work a treat.
Good initiative, nylon printing is very good for all the gears and wormgears. I tested some Nylon printed piston in the bicep for a while and it was pretty smooth and strong.
Not just the screw but the little thickness of the plastic horn under the head of the screw also.
Until now, 3 years of demos, I didn’t see issues with the horn part at screw level. Because I printed my parts in ABS with a 3 shell perimeter I never broke any of my bicep parts besides the early pistons which had a smaller diameter. So I’m guessing this beefier remix is ready for combat! 🙂
Has anyone considered how much weight is being carried by the tiny little screw down the centre of the servo drive shaft that holds the horn onto the shaft? How big is on those servos, 1.5-2mm, 3 maybe?
Ya know, it’s an interesting question, and I don’t know what shear point is for the 2.5mm machine screw used. But in all cases where I’ve broken something, the plastic snaps well before the screw does. I’ve never had a problem with the servo horn set screw.
Hi Gael, I made some test dove tails and they went together very nicely. I did find that there was some flexing/distortion so I\’m adjusting. Was there an engineering reason for that style of dove tail?
I think that a function called “loft” would be the tool for the task. It would involve sketching the profiles at various points along the arm then lofting through them. I have been using the plates from the torso as templates to “extrude” new parts. This has then allowed me to align the various openings and made these uniform in size.…[Read more]
That\’s great, It was something that started bothering me the more I thought about it. I expect that for the service duty this is being put to that these are not a concern. I expect I\’ve been among big machinery too long and with the self teaching over the years I\’ve probably over analyzed this.
Reece posted an update 8 years, 10 months ago
I’ve been working on truing up the Torso plates to get them to align better using a parametric modeler. Hopefully that will make adjustments easier and accuate. Here’s where I am so far. I’m trying to keep the parts as close to the originals as I can for this exercise. Here I’ve relieved the corners and standardized the dovetails. A 0.3mm gap…[Read more]
Hello Reece, Very clean remodeling! Did you try to print them to see how the parts fit and hold together, once the the 0,3mm gap is added?
Hi Gael, I made some test dove tails and they went together very nicely. I did find that there was some flexing/distortion so I’m adjusting. Was there an engineering reason for that style of dove tail?
This looks great and seems to run really well. I\’ve become concerned about the application of servos this way. Have any had the drive shaft get pulled out of the servo in these linear actuator applications? What about the place where the little screw holds the servo horn onto the splined shaft, any failed there?
@Reece, mine has been running for nearly three years now and the servos are still doing fine. The only thing that happens sometimes, the small screw that holds the horn wheel to the servo shaft gets loose, I bet using some blue Loctite component would solve the problem, but I never bought some to test.
That’s great, It was something that started bothering me the more I thought about it. I expect that for the service duty this is being put to that these are not a concern. I expect I’ve been among big machinery too long and with the self teaching over the years I’ve probably over analyzed this.
Mr. Gael sorry for late answer but first my school and then my inmoov, as my daddy said. The mods need to change some pieces. My dad make new stls and i print them. I will post photos of them.
I’ve been working on truing up the Torso plates to get them to align better using a parametric modeler. Hopefully that will make adjustments easier and actuate. Here’s where I am so far. I’m trying to keep the parts as close to the originals as I can for this exercise.
It seems very good Reece! I wonder if OnShape can open the more sculptured shapes like the for arms cover?
I think that a function called “loft” would be the tool for the task. It would involve sketching the profiles at various points along the arm then lofting through them. I have been using the plates from the torso as templates to “extrude” new parts. This has then allowed me to align the various openings and made these uniform in size. With…[Read more]