7 Super Stick
Commercial analog joysticks for the Apple and other home computers are powerful tools for directing a cursor and playing games, but for the most part they are flimsy units. They don't give the player the sensation of handling actual machine controls. Super Stick, by contrast, is a much larger device, about the size of the control stick for a high-performance aircraft. Super Stick is not quite as fast in response as the lightweight commercial units, but it has the robust feel of a controller for a real machine.
This chapter gives you construction details for two different versions of Super Stick. The machined version is the most challenging construction project in the book, and the finished device is the most elegant. It is the only design we've included that requires metal machining tools for its construction. It makes an exciting project for an experienced hobbyist or a student in an advanced metal shop class. The second version, made from sheet metal and wood, is not quite as elegant, but it can be built in the home workshop. The materials for either unit are not difficult to obtain. You should read through the instructions and decide which would be more appropriate, keeping in mind your needs and the tools you have available.
CONSTRUCTION OF THE MACHINED SUPER STICK
Figure 7-1 is a sketch of the machined version. The hardwood handle contains two pushbuttons and is supported by a double-articulated wrist that serves as the mount for the two potentiometers. The upper structure is supported by a machined base and a sheet metal saddle that straps to the leg.
Figure 7-2, in front and side views, gives many more details of the completed device. It shows the location of the pots and pushbuttons, as well as details of the pot wiring.
Figure 7-3 provides details of the component parts. The handle grip is fashioned from two pieces of 6 x 1-1/4-inch hardwood. Walnut is particularly attractive, but true mahogany also makes a striking handle. Alternatively, you could use clear pine and paint the handle jet black, to get a high-tech look.
Cut out the wood blanks with a radial arm or table saw and then contour them into shape with wood rasps and sandpaper. Counter-sink three flathead screws (1/2-inch x #4) into the wood to hold the two halves of the grip together. Then drill the holes for the bolts (1/2-inch x #2) to mount the pushbuttons and the shaft clamp for the top potentiometer.
The machining attachment for a small metal lathe was used to work the aluminum for the top clamp, wrist, and two base uprights. You can use any material that can be machined, including aluminum, brass, steel, or plastic. By starting with stock a little thicker than 1/2-inch, we were able to take a slight amount off all the surfaces, thus leaving them with a decorative pattern of machining marks.
First rough out the pieces with a band saw and machine them to slightly larger than finished dimensions. Then drill all the holes and tap the threads that are shown in figure 7-3. Choose the tap size that is appropriate for available bolts and set screws. Caphead screws set in counter-sunk holes are best for the top clamp and wrist, while panhead bolts are best for the leg mount and base.
When you complete the rough work, go back over all surfaces
with a small milling tool on a final shallow pass. This will bring the pieces
down to exact dimensions and leave the characteristic markings. On the prototype,
all edges were beveled off with a power-belt bench sander. You could also
use a fine file for this step.
The brass bushings were cut from 1/4-inch (internal diameter) hobby shop tubing, but commercial brass bushings with thicker walls would be easier to machine. You could even machine these bushings from brass stock on a lathe. The bushings should not spin, so remember to secure them in place with thread sealant.
Since you may have difficulty obtaining the thicker block needed for the one-piece wrist, figure 7-4 shows an alternate construction of the wrist using three pieces of 1/2-inch stock. To insure that the top clamp piece will move easily between the two uprights, two pieces of shim stock are required for construction.
The pots will be needed during machining to measure the exact size of their mounting bushings and shafts. Different manufacturers vary the sizes slightly. If you do not have the pot when you do the machining, leave 3/16-inch pilot holes for the time being. Trim the pot shafts to the correct length and saw screwdriver slots in their ends.
The leg mount for the prototype was cut from 1/16-inch aluminum sheet and then drilled, using the base as the pattern. Pass panhead screws up through the leg mount and base and screw them into the two base uprights. The leg mount was finished with an orbital sander to remove all tool marks and give a matte finish. You could use a small cup wire brush in a drill press to obtain the swirled finish found on the cowling of the Spirit of St. Louis.
When assembling the pot mounts, don't overtighten the set screws and clamps, since this can crush the pots and make them hard to turn. Put some sealant like Loctite on the bolt threads to insure that they don't loosen.
The wood handle requires fine sanding, staining, and finishing with two coats of polyurethane varnish. After you attach the leg mount to the base and uprights, bend it to fit your leg. Cover the inside of the leg mount with cotton felt. Attach a cloth or leather strap to the leg mount with swat rivets from a leather supply store. Sew a piece of Velcro to the free end of the strap and glue the Velcro mate to the leg mount with epoxy.
CONSTRUCTION OF THE SHEET METAL VERSION
Since not everyone has access to a machine shop, we decided to include a home workshop version of the Super Stick that can be constructed from sheet metal and wood. No unusual tools are necessary for the project. The result, shown in figure 7-5, is a solid, attractive device with good, fast action.
The construction of the sheet metal Super Stick is similar to that of the Sketch Pad (see chapter 4). For the metal work, only a drill, sheet metal shears, file, and pop rivet gun are necessary. Either hand or power saws can be used for the wood work.
The metal should be stiff, but thin enough to cut with hand shears; aluminum or galvanized steel will do nicely. Cut out the six metal pieces, then round and smooth all edges with a file. Make the two cuts for the pot mount with a hacksaw.
Hold the metal pieces with vise grips or in a bench vise while drilling them. To start each hole, strike a point with a center punch, then drill a pilot hole of about 1/8-inch. Don't drill the pop rivet holes in the pot mount until you are ready to install the rivets. The two holes in the pot mount for the spin prevention tabs must be custom fitted to the pots you choose.
You can make the bends in the sheet metal with a sheetmetal brake, a vise, or vise grip pliers. Only one of the top clamps needs to have the large side tabs shown in figure 7-5. The only bends that are difficult to form are those for the pot shaft clamps in the base and for the top clamp. Pop rivet the pieces together, then bend open the two pieces and form the clamp around a 1/4-inch bolt. Using washers on the pop rivets keeps the sheet metal from bending in the wrong places. The two sheet metal ends of the clamp should be about 1/8-inch apart with the shaft installed.
Don't worry if you fail in your first attempt to make the sheet metal parts. Sheet metal is cheap, so discard the piece and start over. Bend the pot mount in the direction shown in the front view (figure 75). Clamp the predrilled brace in place with vise grips and drill the first pop rivet hole. Install the rivet, then drill the holes and install the other three rivets in turn.
Now cut off the pot shafts and saw screwdriver slots into their ends. Apply Loctite to the pot mounting threads after you complete the final adjustments.
The handle grips on the prototype were cut from hardwood scrap with a radial arm saw and then shaped with wood rasps and sandpaper. The bottom of the handle at the lower end where the top clamp is attached is a little different than that of the machined version. The notch on the sheet metal unit cuts both pieces, but the top clamp is screwed to only one piece of the handle. You can make the inside wire groove and switch cutouts with a saw or wood chisels.
The leg board and spacer are cut from tempered masonite. You can make the base upright from any available wood or plywood. The base should be held together with screws and glue, but the handle is held together with counter-sunk screws only, since you have to open it up again to wire the switches. Sand all wood parts and finish them with two coats of polyurethane varnish.
The wiring for this project is not difficult since Super Stick is simply a two-pot joystick with one or two pushbuttons. The pots should be mechanically superior and long shafted. You will have to cut the shafts to length and add screwdriver slots, as noted previously. The pots in these units do not travel through their full 300 degree turn. You can use pots with values larger than standard for your computer, or you can work with easier-to-obtain pots with values of 100K and add correction caps as described in chapter 1. (The standard pot value for the Apple is 150K; for this prototype we used 250K pots.) You can mount the correction caps on a small piece of PCB in the cable about a foot from the plug and encase them in foam packing material.
For pushbuttons you can purchase any normally-open, momentary-contact switches that can be mounted easily on the handle. We used subminiature lever switches mounted with #2 nuts and bolts. The switches and bolts came from Radio Shack.
If you choose to install only one switch you will need only four wires in the cable. The telephone cable noted in the parts list is adequate. For two switches a 5-wire cable is necessary, and this is harder to find. You can substitute two runs of the 4-wire telephone cable, which gives you extra wires to double up the +5 and ground if you use correction caps.
The best plug for Super Stick is the plug/socket described in chapter 3. The pull-down resistors R1 and R2 (figure 7-6) can be mounted inside the plug. If you look carefully at the pots in figure 7-2 you can see which outside terminal is connected to the center terminal with a loop of wire, as indicated in the schematic (figure 7-6).
TESTING AND ALIGNMENT
When you are through with the wiring, check your work against figure 7-6. Then turn off the computer, plug in your new joystick, and turn on the computer again. If startup does not proceed exactly as usual, turn the computer off immediately and recheck your work.
Now run the Controller Checkout program and check the pushbuttons and pot readings. Adjust the pots by loosening the clamping bolts and turning the shafts with a screwdriver until you get readings of 128 for both GC0 and GC1 with the handle straight up. Then retighten the bolts and move the stick all around. You should be able to get full range readings (0 to 255) in both axes.
If either axis works backwards to the way you intended, trade the wires on the outside terminals of that pot and realign the unit. Now you are ready to run one of your favorite games to test the action of your new Super Stick. We think you will find game playing a lot more exciting with a solid controller to grasp.
You can lock all the clamp bolts with Loctite or nail polish. The cables should be securely tied to the pot terminals with dental floss; coat the terminals with silicone sealant. A dab of sealant on the pushbutton hinges will help to strengthen them. Secure the cable to the base with a plastic wire tie.
The leg mount and strap cannot easily be adjusted down to fit a child's leg. If you prefer, you can mount the machined Super Stick on a leg board like the one the sheet metal version is mounted on.
Return to Table of Contents | Previous Chapter | Next Chapter