When I’m working with small mechanical pieces - be it for kit assembly, or disassembly of something I want to put back together properly again, I haul out my workshop ice cube trays, a pen, and some paper.
In the case of building kits, each type of fastener and small part goes into a ice cube cup. If there are enough different types and sizes that it’s difficult to tell at a glance just what they are (1/4" versus 3/8" 4-40 screws, for example), they also get a slip of paper in each cup, or a bit of tape on the side of it, telling me what’s where. It takes a small amount of time in preparation before you get down to the actual building, but the time spent pre-sorting and labeling far outweighs the time and effort involved in measuring everything during the build process, and possibly having to back screws out to replace them with the proper piece later.
When disassembling for reassembly, the parts removed in each distinct step get a new cup from the others, along with a slip of paper letting me know where they came from. This may seem like overkill, but it comes in handy when you’re disassembling a notebook computer to get to a slot on the bottom of the motherboard that needs fixing, and the only way to get there is to disassemble the entire machine from the top to get there. Otherwise, it gets difficult to tell a 2x4mm drive cage screw from a 2x6mm case screw, in an application where using a screw that’s too long can potentially cause a catastrophic short and kill the computer outright.
(okay, sometimes I use little plastic sample cups, too - but ice cube trays are harder to knock over)
The 7.2vdc motors and batteries are on the way out. We used them out of necessity at first. But that was back in the day when you really had no options for motor controllers. You just used RC car controllers. Nowadays we are using Dimension Engineering controllers which work better at 12vdc anyway. Besides there are a lot more motor options at 12vdc.
Does that go for the GHM-04 motors too? I guess with the new 12V GHM-15 motors with encoders, I could see the GHM-04’s going away too, but some robots are small enough to not be able to handle the longer motors, and the GHM-04 is a nice fit (like on WALTER’s current body, for instance). If you only keep ONE 7.2V motor, PLEASE let it be the GHM-04 and QME-01 encoders. Otherwise I might have to buy some more (with encoders) before they go out of stock. I just don’t think a longer motor would be good on other wheeled robots I want to build.
Here are some pictures of additions I’ve made to my Johnny 5:
The first photo shows a wire travel limiter I added to the front and back of the robot. It prevents the torso from falling back when the robot power is turned off. This prevents the spring from over stretching. A similar limiter is added to the back of the robot in order to prevent the torso from falling forward on power down. Made with fishing wire and crimp on sleeves. It is attached to the same points as the spring ends are. As can be appreciated the servos can still work to move the torso, but they will be somewhat limited in their maximum travel. This is OK, because (in my case) if the servos travel all the way forward or backward, the torso cannot recover back to standing straight up.:
This next photo shows the left side of the backpack I made to hold the wireless transmitter and its antenna (Bluetooth Modem - BlueSMiRF RP-SMA). The interesting thing is that this part was made with two left over parts included with the robot. (I used one flat long servo bracket and one regular servo bracket.) Note that I put heat shrink tubing around the radio circuit board, and a little rectangle of inner tube between the radio and the servo bracket. It is held on by zip ties as can be seen.:
This next photo shows the right side of the backpack I made to hold de wireless transmitter and its antenna. I had to drill four holes for the zip tie to wrap around the transmitter module. Note that the bracket also serves to hold the wire bundle.:
I have the standard servos as came in the kit for the waist:
HS-645MG in position 1 (bottom)
HS-645MG in position 2 (top)
(Not as strong as I would have liked, but with my “patch” it won’t be a problem.
As for the transmitter, Yes it’s Sparkfun’s Blue SMiRF.
I was going to take it farther, but my laptop crashed and it’s taking zillions of years to reboot, so I might have to restore it from a backup tomorrow. I plan to give Johnny voice as well. -Migs
Migs, I hope you don’t mind, but I would like to add to your line of tips by adding an image of the bit that I used to assemble the SES brackets for my BRAT.
The right tool makes a big difference in assembly. The Driver I used has a built in magnet that made it a breez with assembly. The magenet holds the screws very well and if you slip, the screw tends to stay on the bit rather than fall on the floor.
The bit is about 20 years old but I think I got it at Sears. It was a Craftsman driver bit set that came with a bunch of hex bits in a nice molded plastic case.
