Monday, April 30, 2007

wiring design

I sat down at my PC and worked up this design using Microsoft paint.
I know for a fact that this is a fairly silly design, but I wanted to get the most out of my power sources... which is why there are 4 different power setups.
Click on the image to get a better view of the design.

The Vex is maxed on motor/servo ports in this design, so if I want to add more servos I will need another Vex controller.

No pictures of the AA frame and wires tonight. I'll try to get something different posted by the end of the week.

Sunday, April 29, 2007


I am not sure if every builder goes through this or not, but I started noticing small problems the other day, and decided to take a step back and fix them. While I was fixing those problems, I found more ... and more.. until my droid is back to the state he was about a month ago.

The only difference between now and then.. is that I know a lot more about how to put this guy together.


I will hopefully have r2 mostly back together by the end of this week, with many of the flaws fixed.

Saturday, April 28, 2007

must fix things before I go much further

OK I'm sure you guys are getting tired of seeing the same old pictures, but I had to take a step back today. While I was working on wires yesterday It occurred to me that I had several details that need to be addressed before I could really feel comfortable with R2 rolling around. So I pulled the batteries and flopped him over on his head.

One of the first things I worked on was the feet. You will notice that the wheel axle is sitting in the lowest slot.. This puts the wheel a bit lower than the ball caster which makes the foot tilt. I decided this was not what I wanted. This also impacts my leg rod setup and a cascade of other things.

so I took everything apart...
Legs, Feet, and a portion of the leg rod system all in a pile.

My A&A frame with just a few bits of wiring. I spent some time on the frame going through my threaded rod setup. There were a few places that needed to be tightened down and others rods needed some adjustments.

One thing that has been in the back of my head this past week is how cramped the space is getting inside the frame. These are my battery chargers, and I am really curious to see where I can jam these into my droid.

My plan was to have a power strip somewhere inside r2 that provides power to both of these chargers, my Vex charger, and a few AA battery chargers. That power strip would terminate to this C13 outlet. A computer cable could be used to plug him into an AC outlet.

There is some space between the center vents and the arm for the center foot, but I will need to build something to hold them in place. This also throws out the idea of having speakers sit behind these center vents... so I am still not sure about it.

more tomorrow I hope.

Friday, April 27, 2007


Did a bit of wiring tonight. This is not my strong point so this may look messy, but I am happy with my progress.

Thursday, April 26, 2007

2 legs - leg rods 95% completed

Standing on 2 legs again. No duct tape this time. Leg rods almost completed. There is still a fair amount of slop in the leg rod system at the feet and just the smallest amount of slop in the shoulder. I plan to replace the screw in the shoulder to fix that part, but the slop in the feet will need another day to think about how to solve.
Front shot.

Oh.. didn't realize you could see the electronics on the above picture. The connection bar, and the blue box are on the backside of the electronics that are shown below. I actually have the Vex power charger connected to the battery and the vex controller. The switch shown below is the toggle to put him into a charging position. Its a 3 position switch on, off, charge is the current setup.
Back shot.

Head on backwards.

This picture didn't turn out very well, but this was how I solved my rod to frame problems. I actually cut my 1/2 tube and then used 2 collars and some aluminum bars.
This gives me better access to wiring, and I can individually adjust each leg right here without having to disassemble the shoulder cam components.

While I was cutting aluminum, I cut some pieces to mount a few batteries.

And here the battery is in place.

I should be working on wiring for the next day or two. After that I will be programming my vex for several days.

Sunday, April 22, 2007

slow week again

Sorry for the delay in posting. I didn't get much time this week to work on R2.
I am still trying to solve my leg rod problem, but decided to take a break from it until I get a few other things completed.

I started to work on some electronics. In this picture I have pulled the wire through the legs. I also did this because I needed to find out if there was enough room for the legrod and the wire.

I picked up some sheet metal, and mounted several of the electronic parts. R2 is upside down.

Monday, April 16, 2007

new suspect...

I didn't get much work done on Sunday, but today I decided to take on these split clamps again. After drilling out one of the screws that had broken off in the clamp, I got everything back together and the clamps seem to be doing much better.

I was starting to get excited that I might actually make some progress. I decided I should test the system and it didn't take long to notice that the feet were moving way too much. I checked the clamps again.. and then raised the center leg and I saw my new nemesis...

My idea to use this flat bar and just a hole in the pipe is apparently not a good idea. I did my test again and the pipe was clearly moving.. not the clamps.

I pulled out the bolt and as you can see from this terrible picture.. the bolt is now bent. Its not bent by much, but its enough that the feet were flopping around a good inch or two. Any play down there at the pipe translates to a lot of movement at the feet.

I might have just used to much weight on everything, but this is actually why I was doing the tests... is this stuff going to hold up when my droid weighs ~130lbs?

I put my tools down after discovering this problem, and plan to take a day to think about how to lock the pipe to a fixed position relative to the frame.

Saturday, April 14, 2007

some progress.. new problems

Well I was pretty disappointed last night when the cams failed and R2 started to fall over.. but I gotta keep moving forward. I decided to stay away from the cams and leg rods till I made some progress on the center leg.

There is some question of how sturdy the front leg support plate is that holds the center leg motor. Andy had mentioned sending me the extra part, but not sure if that's actually going to happen, so I proceeded to make my own out of some spare PVC from the original frame.

I placed this panel over the top of the front leg support plate and ran a few screws through it. I wanted to make sure that this thing was secured to the right and left mid plates (review the A&A frame documentation to identify the mid plates)

lets see.. Electronics. I started wiring a few things together to get the shoulder motors and center leg motor working. Its a mess but everything seems to be working.

I used alligator clips to connect the motors temporarily since I need a way to quickly connect and disconnect.

hmm... that was actually pretty easy. Everything went together on this without too many issues. Watch the Video!

Well.. after all that I decided to go back to the cams and the tilt rods. No new insight. I managed to break a few screws trying to tighten stuff down. Those will pose a serious challenge to remove or repair. But when I put my tools down for the day I had managed a new milestone. R2 is on 3 legs. Doesn't appear to be the correct angles.. but he isn't falling over.

Friday, April 13, 2007

1 step forward - 3 steps back

After spending alot of time doing math... I put my pencil down and decided to just hack off enough of the rod to put the parts together and see what was going on inside the foot.

I cut off about 5 inches on each flat bar, which puts them around 24" long. My math had told me to cut it to 22" but I was still not sure if that was right so I left myself some room.

Here is the first attempt. This was actually last night, and the feet are moved to the correct position. This gave me a good indication about how much more of the rod needed to be trimmed and where to drill the hole.

It was about this time that I threw away the paper that had all my math on it and started to eyeball this thing a bit closer..

This shot shows how the rod enters the foot. The red circle is the legrod.

and then... well I didn't get pictures but bad stuff happened.
This picture just shows you that I did get the distance, and the holes drilled.. but what it doesn't' show is that I had everything assembled and got my wife to help me stand him up.

At first he was OK.. and then he started to lean back on those leg rods.. and he kept leaning back.. and back.. until the foot was touching the leg. I thought something was bending but it turns out. The split clamps were failing.

I pulled everything apart and tried my best to get these as tight as possible, but no luck. They just wont tighten down enough on the rod. I must have taken off too much metal when I was sanding.

solution.. I'm going to try and key the rod and the clamp. Ill use a screw to lock the clamp to a specific location. If that doesn't work.. I have a few more clamps on the way... and the hunt for another rod begins tomorrow.

Wednesday, April 11, 2007


no pictures today, but trust that I am working on my robot.

I have crunched a bunch of numbers and came up with some min/max values for rod length and min/max distance for leg rod to ankle from ankle bolt.

at this point the minimum length (from bolt to bolt) that my rod can be is 22.055 and the max is 22.0625... not much variance there so I am getting very close on the length.

the distance from the ankle bolt to connect the rod is (again bolt to bolt) .. min .5 and max 1.625 so about an inch of play there. I would really like to nail this space down to less than .25 of an inch so still a bit more math to do.

I did figure out that the cam I took the measurements from is sitting at 109 degrees which is why its looks like its pointing to somewhere just before 4 o'clock in the shoulder.

(btw, I wouldn't use these numbers on your robot until I provide the proof. Because of the length of the rod, and the very tiny angles.. a miscalculation will cause your droid to fall over.)

OK more soon

Monday, April 9, 2007

feet motor mounts

When I got home from work today, there was a USPS box waiting for me. I still have a handful of parts that I am waiting on, so I wasn't sure what was in the box until I picked it up and I heard the loose pieces of PVC sloshing around.

It didn't take long to dry fit the parts together, figure out how many threaded rods, and bolts were needed.. and once that was done.. I jammed the motors and wheels in.

The center foot needs some work but I am pleased that I was able to get this stuff put together very quickly.

and another shot from the bottom.

tomorrow I would like to try and get the length of my leg rod figured out. Not much information coming from the builders group on the length needed.. so I will be doing the geometry. Ill try to do a quick writeup on how I calculate the length and the location of the hole that needs to be drilled in the motor mount this week.

Sunday, April 8, 2007

Return of the builder

The next post may be called revenge of the hacksaw since mine decided to take a chunk of flesh off my thumb. Every builder apparently suffers some damage while building. I guess that means my robot is not going to live by the Asimov laws.

moving on... There isn't too much here, but this is the little bits of stuff I have managed to work on over the past week. I hope to get back to posting regular updates now that my yard project has the major bits completed.

Paint tests. terrible picture. The white is over exposed, and the blue didn't like its picture being taken either. I think these came out alright. I actually did this work a week ago. I have been doing scratch tests to see how it is holding up. Definitely takes a week for this stuff to really harden up good.

OK 2-3-2 stuff.

This first shot shows the cam, pipe, and leg rod all assembled in the 2 leg position. (everything is upside down.) I have the cam just a bit lower than 3 o'clock right now and this may need to be adjusted more.

The pipe is secured to the frame using a flat bar that I bent and tapped a few holes. This is the inside of the A&A frame to the left of the center leg motor mount.

I haven't trimmed the bottom of my leg rods, because I am waiting on feet motor mounts. There is a red line right at the base of the leg on the rod.

Here the legs are rotated to the 3 leg position. Notice the cam stays in the same position relative to the frame.

Last.. the rods sticking out of the legs at the 3 leg position. Again notice the red line. (sorry this picture is terrible) It appears that the rod moves almost exactly 1.25 inches. I have no clue if this is good or bad right now. I am hoping that it is good.