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06-18-2022, 01:58 AM
(This post was last modified: 06-18-2022, 12:27 PM by Dyne.
Edit Reason: Add some comments about the head leaning slightly back.
)
Though things are going a little slower than I would like (mostly due to my focus slipping every so often), I'm continuing to make steady progress, so I don't feel like I'm falling behind. The head portion is starting to come together, and I still have nearly two weeks to deal with the other challenging bit (the treads).
This is the setup for the portion of the droid above the base, as it exists currently:
![[Image: 20220618-LDF1-01.png]](http://www.niflheim.net/droidbuilding/images/LD-F1/20220618-LDF1-01.png)
The green model is my interpretation of the externally visible neck structure of the droid. Though it appears to be two independent "stalks", it's really just one part (though I plan to split it into left and right halves for printing). As I mentioned before, I decided against making the droid able to lean it's neck forward and back, at least in version 1, so having these as one part is perfectly fine. Still, I put a fake "pivot" at the bottom of the rear stalk.
The stalk model is essentially a printed shell around the primary structural elements of the neck: a pair of 5/16 inch threaded rods. You can see in the cross section below that the rear rod runs all the way into the head (it's the rotation axis of the droid's head mechanism, and it's 5/16 inch because that's what works with the 608ZZ skate bearings I use). The forward rod is simply there for strengthening that part; nothing actually rotates around it. For proper strength I'd really need to have these rods threaded into metal bars connecting them top and bottom, but that's unlikely with what I have access to.
Using the rear rod this way does somewhat limit my options. I believe that on the image of the droid in the lowered position, the exterior neck leans backwards by something like 5-10 degrees. This adds a little more of a raked feel to the droid, and would probably slightly improve the weight distribution. I could redesign the green Stalk part to do this, but doing that would mean I'd have to abandon using the rear rod as the droid's head rotation axis ... it would require a bend in the opposite direction for the head portion, otherwise the plane of the head rotation would no longer be level with the ground.
![[Image: 20220618-LDF1-02.png]](http://www.niflheim.net/droidbuilding/images/LD-F1/20220618-LDF1-02.png)
The "Rotation Platform" (yellow part at the top) is fixed to the stalks via M3 screws and is the attachment for the rotation servo on the upper right, as well as having recesses for the locknuts that keep the rods in place.
The skate bearings that I mentioned above are nestled in the top and bottom of the orange part (the "Neck Core"), which is the part that the rotation servo drives (by gearing). You may notice that I have combined the head pitch axle bracket (the green part that was in a screenshot in the previous post) with the Orange part. It simplifies the design, eliminates some fasteners, and allows me to make the arms thicker since I don't need to fit screws between them and the gear.
I have changed the front servo brackets (red parts) to extend over the two tilt/nod servos rather than under them. The front rod's locknut will protrude slightly into the area these would rotate through and I didn't want them colliding. The tilt/nod servo horns may end up pointed in the opposite direction (backwards) either for room or to put them closer to the pivot point for the head.
The lower yellow parts are just the outer portion of pivot point A (according to the labels in my diagram from a few posts back). These outer sections will be part of the AD arms of the parallelogram mechanism for the neck lift.
You can see that pivot point B is modeled into the bottom far right of the green part. Pivot A will use another pair of 608 bearings, which pivot point B uses a pair of tiny 623ZZ bearings (which are also what I'm using for the pitch and bank axis in the head) because I wanted something a little less blatant than another skate bearing tucked under the forward edge of the rear body shell.
Finally, below is an image of this assembly in the context of the droid, with the upper box representing the head as before, and the circles representing the rollers of the droid's tracks (left is forward). The construction lines coming off the rear roller are for positioning Pivot D of the parallelogram (C is the axis of the rear roller). I will likely have to add a bit of weight to the rear of the droid to offset the entire mass of the head being near the forward roller to prevent it faceplanting when coming to a stop.
![[Image: 20220618-LDF1-03.png]](http://www.niflheim.net/droidbuilding/images/LD-F1/20220618-LDF1-03.png)
Because I know I'm going to need to print large pieces for this droid soon, I had to address a few small areas of my print bed that weren't adhering very well (instead of just avoiding them). So today, I spent a little time re-leveling the printer (it's been moved around a few times since I last did it). So far it seems to have paid off.
This is the setup for the portion of the droid above the base, as it exists currently:
The green model is my interpretation of the externally visible neck structure of the droid. Though it appears to be two independent "stalks", it's really just one part (though I plan to split it into left and right halves for printing). As I mentioned before, I decided against making the droid able to lean it's neck forward and back, at least in version 1, so having these as one part is perfectly fine. Still, I put a fake "pivot" at the bottom of the rear stalk.
The stalk model is essentially a printed shell around the primary structural elements of the neck: a pair of 5/16 inch threaded rods. You can see in the cross section below that the rear rod runs all the way into the head (it's the rotation axis of the droid's head mechanism, and it's 5/16 inch because that's what works with the 608ZZ skate bearings I use). The forward rod is simply there for strengthening that part; nothing actually rotates around it. For proper strength I'd really need to have these rods threaded into metal bars connecting them top and bottom, but that's unlikely with what I have access to.
Using the rear rod this way does somewhat limit my options. I believe that on the image of the droid in the lowered position, the exterior neck leans backwards by something like 5-10 degrees. This adds a little more of a raked feel to the droid, and would probably slightly improve the weight distribution. I could redesign the green Stalk part to do this, but doing that would mean I'd have to abandon using the rear rod as the droid's head rotation axis ... it would require a bend in the opposite direction for the head portion, otherwise the plane of the head rotation would no longer be level with the ground.
The "Rotation Platform" (yellow part at the top) is fixed to the stalks via M3 screws and is the attachment for the rotation servo on the upper right, as well as having recesses for the locknuts that keep the rods in place.
The skate bearings that I mentioned above are nestled in the top and bottom of the orange part (the "Neck Core"), which is the part that the rotation servo drives (by gearing). You may notice that I have combined the head pitch axle bracket (the green part that was in a screenshot in the previous post) with the Orange part. It simplifies the design, eliminates some fasteners, and allows me to make the arms thicker since I don't need to fit screws between them and the gear.
I have changed the front servo brackets (red parts) to extend over the two tilt/nod servos rather than under them. The front rod's locknut will protrude slightly into the area these would rotate through and I didn't want them colliding. The tilt/nod servo horns may end up pointed in the opposite direction (backwards) either for room or to put them closer to the pivot point for the head.
The lower yellow parts are just the outer portion of pivot point A (according to the labels in my diagram from a few posts back). These outer sections will be part of the AD arms of the parallelogram mechanism for the neck lift.
You can see that pivot point B is modeled into the bottom far right of the green part. Pivot A will use another pair of 608 bearings, which pivot point B uses a pair of tiny 623ZZ bearings (which are also what I'm using for the pitch and bank axis in the head) because I wanted something a little less blatant than another skate bearing tucked under the forward edge of the rear body shell.
Finally, below is an image of this assembly in the context of the droid, with the upper box representing the head as before, and the circles representing the rollers of the droid's tracks (left is forward). The construction lines coming off the rear roller are for positioning Pivot D of the parallelogram (C is the axis of the rear roller). I will likely have to add a bit of weight to the rear of the droid to offset the entire mass of the head being near the forward roller to prevent it faceplanting when coming to a stop.
Because I know I'm going to need to print large pieces for this droid soon, I had to address a few small areas of my print bed that weren't adhering very well (instead of just avoiding them). So today, I spent a little time re-leveling the printer (it's been moved around a few times since I last did it). So far it seems to have paid off.