"The Gas Pipe System"
The first step was to mount the legs to the frame which involved using a system developed by Mike Senna. This system is a tried and proven method which uses gas pipes that act as a support system much like the axle of a car, except that it is not subject to constant rotation. It's rather a clever and simple concept where gas pipes run horizontally through holes on both right and left uprights of the frame and the ends of each pipe are attached to the hubs of each leg using a pipe flange. To prevent the pipes from rotating, a U-bolt with a round bend is used to clamp it down. The U-bolt is mounted on a heavy duty steel angle bar that runs vertically with the frame. The bottom end of this bar is anchored to another angle bar used to hold the center ankle to the base plate of the frame. Pretty simple right?
From what I have figured, droids with wooden frames utilizing this clever design have three significant advantages over those droids with its legs bolted directly to the frame:
1. Reduces the stresses from locomotion. For a droids with their legs bolted to the frame, when propelled forwards or backwards, and being that the motors used for locomotion are at the bottom of the legs, the torque will produce a large amount of stress on the hub-to-body joint. While I cannot speak for those who have their legs bolted directly to the frame, whether there has been a history of weakened or damaged frames or not, I will just er on the side of caution and use the gas pipe system.
2. Acts as a frame within a frame. Rather than have the wooden frame act as the main support structure of the entire droid, the legs-gas pipe-ankle combination, acts together to forms an internal frame, independent of the wooden frame. This means that as more and more stuff is added to the droid, the added weight will bear stress on the gas pipe system (which now serves as the main support structure), and not on the wooden frame. This system also forms strong foundation to keep the legs perfectly parallel with the body and there is zero or minimal inward or outward flex in the lateral direction.
3. Can be used as a safety lift point during transport. Most fully completed droids with wooden frames and have basic functions will weigh over 100 pounds. A fully assembled droid with the dome off, can be safely lifted without the risk of damaging costly parts, especially the greeblies, when you use the gas pipe as a lifting point.
The gas pipe system utilizes two black gas pipes (one 1" and one 3/4".) and two electrical conduit flanges (one 1" and one 3.4").
Finding a pair of gas pipes where the smaller one would fit inside the bigger one was a REAL CHALLENGE. Not all pipes are made the same because the manufacturing process produces a thin internal bead, that runs across its entire length, that can vary in size. The bigger the bead size the more obtrusive it is, preventing the smaller pipe from sliding into it. I remember having gone thru the supplies of one Lowe's and two Home Depot stores until I found the perfect 1" pipe with a less obtrusive bead (at the Home Depot). I can recall a few instances where customers would give me a funny "what the hell are you doing?" look while I exhausted an entire shelf of dirty black gas pipes, trying to fit one into another.
Here's how the gas pipes look with the smaller one inserted into the larger one. You can see from the pic below how it resembles an axle for an automobile.
In order to slip the pipes thru the frame, holes big enough for the 1" pipe had to be drilled on each side of the frame, more particularly, the lateral plates. But before that was even possible, the skins had to be attached, which will allow the the hubs to be aligned correctly so that a mark can be made to cut the holes.
The skins were temporarily attached using masking tape and then marks were made which aligned with the dead center of the "leg sockets" of the skins.
The skins were temporarily attached using masking tape and then marks were made which aligned with the dead center of the "leg sockets" of the skins.
The pipe was fitted and checked for squareness against the frame. So far, so good...
The center ankle angle bar mounts also make part of the gas pipe system. A heavy duty steel angle, also purchased from the Home Depot, was cut to size, and two mounting holes were drilled. The wooden center ankle was then bolted to it and as one unit, it was then aligned and finally bolted to the base plate.
The 1" flange was permanently fixed on the left leg, and the 3/4" flange fixed on right. The pipes were temporarily screwed on tightly to the flanges. I sat Artoo's body on top and between two milk crates which allowed the center ankle to clear the floor. With the skins still taped to the frame, the left leg (1" pipe) was inserted thru the hole of the left plate and out thru the hole on the right. The right leg (3/4" pipe) was then inserted 1" pipe thru the right side.
Studying reference movie stills of A New Hope, I chose to have a shoulder-to-body gap of 1/8", which of course, is my guesstimate. To help with alignment, I wedged a spacer ( a piece of scrap 0.125" styrene) between the shoulders and the body of both sides. Each pipe was then checked for the correct length, which only had to be long enough to clear both holes, but not so long that it would cause the other leg to protrude too far out.
Studying reference movie stills of A New Hope, I chose to have a shoulder-to-body gap of 1/8", which of course, is my guesstimate. To help with alignment, I wedged a spacer ( a piece of scrap 0.125" styrene) between the shoulders and the body of both sides. Each pipe was then checked for the correct length, which only had to be long enough to clear both holes, but not so long that it would cause the other leg to protrude too far out.
