Mount Head
In this step we will mount the pan / tilt head to the rover main assembly.
Required Parts:
1x Pan Head Lower Metal Frame
1x Long Servo Horn (in the small bag with each servo)
1x Servo Mounting Screw (in the small bag with each servo)
2x Tapping Screws (these are NOT the screws in the bag with each servo)
2x M2 6mm Screws (these are the slightly larger diameter screws)
2x M2 ('larger') Nuts
Begin by mounting the servo horn to the lower metal frame. Note the servo horn goes in from the top and the screws go in from the bottom.
When completed it should look like this.
Install the lower metal frame onto the servo on the main assembly. The screw attaching the servo horn to the servo is optional. If you do use a screw, the correct screw to use is the smaller of the three screws included in the small bag with each servo.
IMPORTANT NOTES:
Notice there is a slight cutout on the front side of the metal frame. This cutout needs to be toward the front of the robot.
If you want, you can leave out the screw that attaches the servo horn to the servo. Note that if the robot ever falls or is grabbed by the head unit, all the stress will be placed on this connection to the servo. This is the most delicate part of the head assembly. If you leave off the screw, any stress to the head will simply pop it off the servo. It can be easily set back on the servo and will likely be okay. However, if the screw is in place, damage may be done in such an event.
Adding the screw will make the head more stable, and you will have less play in the mechanism and thus the head will be more secure when moving around. This will tend to reduce jitter from frame to frame when viewing images through the Raspberry Pi camera.
The screw can be added after the head is complete and the robot is fully assembled, though it is more difficult to access this area once the robot is complete. If you do add it after completion, power off the robot before adding the screw so the servo is not energized. This will reduce stress on the servo gears when tightening the screw.
Plug in the LED board cable to the socket on the Spirit Main Board labeled "EYES LIGHTS".
IMPORTANT NOTE:
When preparing to mount the upper metal frame onto the lower metal frame, take note of how the ultrasonic cable and eyes LED cable are routed. The cables should not loop out to the side of the rover. Twist the head so the cables naturally want to coil up behind the head. After mounting the head, this will keep the cables naturally coiled above the top of the robot and not hanging off the side.
Connect the upper metal head frame to the lower metal frame with the two screws and nuts highlighted above. This area can be challenging to access. We suggest using thin pliers or tweezers to hold the nut in place while using a screwdriver from the side to thread into the nut.
VERY IMPORTANT NOTES. PLEASE READ COMPLETELY BEFORE YOU CONTINUE:
The lower metal frame should fit on the OUTSIDE of the upper metal frame that holds the ultrasonic.
It may be necessary to carefully straighten the ends of the lower metal frame or the tabs on the upper metal frame where the two mate together. Perfect alignment isn't necessary, but smoother alignment will result in cleaner movement of the head.
As we tighten the nut onto the screw, we want to hold the frame upper and frame lower closely together, but they still need to be loose enough for smooth movement.
To set how tight the nut fits, we suggest you tighten until the nut is snug on both sides, then rock the head front and back a couple of times. This will cause the nut to back off slightly. After rocking, leave the head pointed upward for the next step. You only need to rock a couple of times until you feel the resistance drop. Rocking too many times will result in the nut backing off too far and the head assembly being sloppy. You can re-tighten and try this a few times until you achieve a fit you feel is correct.
To lock the nuts in the correct location on the screws, we will use a small amount of white glue. Standard white craft glue, Elmer's glue, or similar works well. You could also use rubber cement or similar. HAVING A TOOL TO CAREFULLY AND ACCURATELY APPLY THE GLUE IN THIS STEP IS VERY IMPORTANT.
Apply the glue as follows:
Carefully study the picture above inside the red circles. We are attempting to put glue on the screw shaft that extends beyond the nuts. This glue, when dry, will "lock" the nuts in place and prevent them from becoming loose during operation.
IT IS EXTREMELY IMPORTANT TO AVOID GETTING GLUE ON THE OPPOSITE SIDE OF THE SCREW AS IT WILL GLUE THE JOINT TOGETHER. WE DO NOT WANT TO GLUE THE JOINT TOGETHER. Also note you only need a very small amount of glue. We just want some resistance in the threads so the nut won't back off. You probably won't ever remove these screws, but if you need to in the future, having too much glue will make it more difficult.
Put some glue on a temporary surface like your desk or a plate, then use the tip of a thin tool to dip into the glue. Use the tip of a screwdriver, a bit of wire, a toothpick, or similar.
Apply the glue to the threads of the screw up to the nut. It is okay to get glue on the nut, just be careful it doesn't glob over the top of the nut and get into the joint.
Once both screws and glue look similar to the image above, set the assembly aside and DO NOT TOUCH IT for at least an hour. This will allow the glue to dry completely without being disturbed. You will have best results if you leave the assembly completely untouched during the drying time of the glue.
If you use a screwdriver to apply the glue, clean it off before it dries. If you put the glue on your working surface, be sure to clean it before it dries.
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