Rolled Flat Head Skins

& Chopper's Head 

Update 05/15/18 - Version 1.0 of Chopper's Head Design has been released. Published Assembly drawings and pictures.
Update 11/05/17 - made corrections to drawings of the flat skin sections - now marked v0.1 to reflect changes
Update 10/31/17 - 3D design work on the first prototype of a head design for Chopper is complete.
Update 7/23/17 - The 3D solid version of the head has been updated to follow Cleofett's drawing more closely. 
Original Post 07/02/17 - Chopper's Head is derived from Cleofett's .dwg drawing files with details added from TinyP's 3D printed parts.

Chopper's Rolled Flat Head Skins
This version of the rolled flat skin was done using Alibre Design (Formerly Geomagic Design) and is the latest of several attempts at getting some usable results. AD sheet metal design does not permit engraved lines. If you download the 3D model you will note that the panel lines are cut all the way thru the .080 skin (you'll see the red bottom plate thru what should be only panel lines). On manufactured skin panels the cuts would only be .040 deep. In addition to the front and rear skins for the head there are also skins for the Lower Tapered section and the bearing section. Each of those sections has been cut in half just to make the parts easier to handle.


See below for links to downloadable documentation. The Rolled Flat Head Skins have not changed with the release of the Head Design.

Chopper's Head Design




Images above are linked to 3D.pdf files so you can rotate/zoom in to see details.

The Head has two sub-assemblies: The Arm Boxes and the Head Top. After those are assembled they are integrated with the remaining ribs and rings to make up the Head Skeleton.  Finally, the skins are applied to the Head Skeleton to complete the Head assembly. Before beginning the assembly please download the v1.0 document set and study the drawings and then look at the 3d.pdf files and study how the parts fit together. As usual, a dry fit of the parts is required before beginning glue-up.
We will be using a combination of CAD drawings and Photos to illustrate the assembly process. Note that the pictures, kindly provided by Paul G, are from the assembly of the Version 0 Prototype. Please see the Change Log to see what was added in the Version 1 Release. Those items will be missing from the photos and illustrated using the CAD drawings. Thanks for your understanding.

VXB Bearing for Head Rotation
Before we plunge into the assembly, we need to discuss the bearing used to rotate Chopper's Head. I followed Patrick Stefanski's (PatchBOTS) lead (see his #2 video) where he sets up a VXB bearing for head rotation. The bearing is a VXB 392mm (15.44") lazy susan bearing Product Code: KIT11281. You can buy it directly from VXB  or from eBay sources [pick the one with lower cost shipping :-) ]. Documentation provided by VXB is included with the document package, but it's incomplete and not very helpful. On top of that, for reasons I cannot understand, the mounting holes are not drilled on a concentric circle.


Above: This is a VXB website picture of the bearing. It's misleading, there are actually 6 holes in the inner ring. Some are blind holes.

Left: I got ahead of myself and didn't take pix of the "before" version (similar to above). This is the disassembled bearing. I drilled out the holes for #10 screws and then countersunk them. Note the Markings. I added more. To re-assemble, and for alignment later on, Before You Disassemble mark inner & outer bearing races with Top & Bottom and then number the holes. From experience with R2's Rockler Bearing plan on disassembling the bearing. It's almost impossible to prevent aluminum shavings from getting into the bearing race. 

You may also want to replace the balls with Acetal ones for a smoother ride.The balls from the bearing measure 3.93mm or .1545in in diameter. You should be able to get acetal balls from McMaster Carr.

Example 1: this hole is drilled close to the outer edge

Example 2: this hole is drilled close to the inner edge

this is the Head Bottom ring I've installed 6 6-32 x 1 screws into the holes - they will cut their own threads in the plastic - no need to tap

The hole indicated by the green arrow is the "front of droid" marker hole. The short slot is the one for the index rib (more later on)

My bearing was a tight fit onto the #6 screws - meaning that the mounting circle drilled in the plastic does not match the actual holes in the bearing.

this screw, like the others, is tight against the inside of the hole.
So here is one 'plan' to get alignment with the mounting holes.

First, verify that the bearing is centered on the ring. measure the tooth edge to the inside of the inner race and verify that it's the same all around. You can do the same for the outer bearing to the outside edge, just put tape on the bearing to hold it in place.

Then remove just one of the #6 screws. Use the bearing as a guide and drill out the hole in the Head Bottom ring to fit #10 (Use an undersized drill with tape on it to avoid creating aluminum shavings that might get into the bearing! - remove the bearing and complete enlarging the hole to #10 clearance). Then replace the bearing on the ring, use a #10 screw in the enlarged hole. Repeat the process with the #6 screw that is on the opposite side of the circle. Then so the same for the other sets of holes.

Your Mileage may Vary. This 'process' is not tested (yet). If anyone has suggestions on a better process please let me know!

Link to Chopper Head Assembly - Step by Step instructions

Links to Downloadable items
I've created a .zip file with all of the documentation - click here to download.
It includes: Cleofett's head drawing with added information in both .dwg and .pdf format. A Chopper Parts Drawing set in both .pdf format (1 file with multiple pages) and in autocad .dwg format, a copy of the change log, and a copy of the VXB bearing documentation. Study the .pdf files - part names are on the drawings. I will use those names in the descriptions.

Chopper Home Page