Prototype CNC Design
Chopper's Right & Left Legs are derived from Cleofett's .dwg drawing files. See the Legs page for an interference problem between the Leg and the Foot shell and the solution that I have adopted here.
|At first glance, Left and Right Legs look like they might require two different designs. The Legs, however, share a lot of details in common. The most obvious parts that are different are the top portion of the two legs and the detail attachments that mount on the front surfaces.|
Left Leg - common Leg Frame with a casting for the curved upper portion
Right Leg - common Leg Frame with a non structural CNC assembly for the upper portion
|The remaining drawings link to 3D.pdf files that can be rotated to be viewed from any angle.
Leg Frame design is a structural component common to both legs. In this image it's wrapped with .040 skins (2 layers on the curved top portion).
Here we have peeled off the .040 skins. The blue color components are .125 thick non-structural parts of the design. The balance of the parts are all .1875
For strength, the leg has 3 layers of .1875 styrene, with an additional layer in the area where the leg bolts to the body. As a result of the change in thickness of the leg where it is mounted to the foot, there are 2 layers in the top inner section and 2 layers in the bottom outer section of the leg.
With the outer layer peeled off you can see the box beam ribs that run top to bottom as well as radiate around the area where the leg bolts to the body. The center channel between the shoulder and the foot is unobstructed for wiring between the body and the foot. Not shown is the hole at the bottom of the legs for the wires to exit. It's location is dependent on which side of the body the leg is built for.
|Aside from the leg struts, and their attachment points, there are two other components that are needed for the leg design. One is the Shoulder Cover that hides the access point for the bolts that attach the leg to the body and that allows you to run wires from the body down to the feet. The other is the Shoulder Mounting Hub that goes between the leg and the Body. Both are shown in profile view below.|
shoulder designs shown above have been modified to provide a pair of
tabs that accept 1/4-20 bolts that are used as magnetic attachment
points for the shoulder cover shown below.|
The Shoulder hubs have been modified to have recessed holes for hex nuts. That allows you to bolt the hub to the leg. That means there are only 2 parts to be held in place while you are mounting the legs to the body.
In the images of the Shoulder Cover and the Shoulder Hub are linked to 3D.pdf files.
|What's still to be done:
Design 'cleanup' - the bevel edges on most of the parts that have them are cut to the angles dictated by the design. Bevel cutters are restricted to the available set of 15,30,45 degree angles. The bevels will be modified so that the edges meet where needed.
I'm thinking that a row of magnets would work for the detail attachment for the right leg. That's the same method I'm using to hold the battery boxes to the foot shell. It's not needed for the left leg since the detail part there does not cover the shoulder hub/cap and does not need to be removed.
Please ask questions, make comments & suggestions that you think might improve the design.
Contact me using: fpirz (at) media (dash) conversions (dot) net
Chopper Home Page