Next large robot



  • DiverBobDiverBob Posts: 791
    edited 2013-03-24 - 00:26:19
    I decided to spice up the lower leg tubes today by adding a little pin-striping. I ordered some 3M vinyl tape in various widths to experiment with and took some photos of the process.


    This discussion begins with the lower leg tube being anodized, this tube is 15 inches long and 1 inch in outside diameter. It was polished to a brushed aluminum finish then cleaned and degreased. Here is the tube being anodized. Due to the size of the tube and the 5 amp maximum output of my power supply it takes 1 1/2 hours to complete the anodizing step. Throughout this process handling of the part is to be minimized and I wear latex gloves to keep finger oils off the part.


    After anodizing the lower half of the tube was inserted in 140 degree Gold dye for about 30 minutes. The length of time in the dye determines the intensity of the color. In this case I wanted the brightest color I could get so I left it soaking in the dye a long time.


    After dyeing the tube was rinsed and dried. The vinyl tape was applied and then all the edges were burnished down to prevent leakage of liquids. The unmasked dye is ready to be removed. Here the tube was only in the bleach for a few seconds which removes the majority of the color. Since the part is larger than the bleach container a small brush is used to spread the bleach where needed.


    This next step is the acid wash (15% sulfuric acid) which removes the remainder of the gold dye and opens the oxide pores for more dye. As you can see the gold dye is practically gone at this point.


    Now its ready for the Black dye at 140 degrees. The part is larger than the dye pot so I rotate it end for end every couple of minutes. It only takes a few minutes for the black dye to penetrate the pores so this step is quick.


    Out of the black dye, a quick rinse and then into the Nickel Acetate sealer at 190 degrees. I put it into the sealer for about 5 minutes at each end to start the sealing process and then remove the tube and remove the vinyl tape. The tape comes off easier when hot and leaves less tape adhesive residue. Then its back into the sealer for an additional 10-20 minutes (longer is not a problem). If there is still any tape adhesive on the part then it is scrubbed with Toluene which removes it very easily. The final results turned out quite nicely and after a little polish and buffing it will fit in nicely with the rest of the robot parts.

    Tomorrow will be spent anodizing as many parts as I can get done since I'm on night shift for the next 6 weeks and working 4-12s (long nights but I get 2 days off every 4 days). I hope you are enjoying my trials in creating this robot. I will continue to document the process so long as it seems people are interested. I'll post my progress on my next days off!

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  • garyggaryg Posts: 420
    edited 2013-03-24 - 18:24:19
    I've been reading all of your posts for this project.
    I always look forward to Diverbob updates.
    Thanks for your endurance!
  • BrainStrainBrainStrain Posts: 30
    edited 2013-03-26 - 23:18:45
    Thanks for the effort and time you are putting into sharing your build with us. I very much appreciate it!
  • DiverBobDiverBob Posts: 791
    edited 2013-03-31 - 12:38:05
    Finished up anodizing the parts for the 3rd leg, 3 more to go! Unfortunately I put a number on the 'knee' and it turned out I had the number on upside down... Now I have to strip the anodized coating off and start over on that part. Slow 2 days off, planning on starting to put together one leg next time off and verifying measurements. I still have to use the lathe to create all the cross members that provide stiffening support.

    I did re-arrange my basement workshop for a location for the new lathe which should be showing up in the next 2-3 weeks. It may take a while to get it down into the basement since it weights around 1250 lbs. I'll attempt to disassemble as much as I can first.
  • photomankcphotomankc Posts: 929
    edited 2013-03-31 - 13:45:54
    I hope you never have to move it back out of that basement. Having just hauled a 450lb lathe up this winter, I resolved that there shall be no more basements shops for this aging nerd.
  • DiverBobDiverBob Posts: 791
    edited 2013-04-05 - 00:16:26
    No pictures this time, just polished up all the anodized parts and press fit the bearings for the first leg. That went pretty well and the 14 bearing are properly seated. Next was temporarily bolting up the leg parts to verify the fit of everything and that went well also. I now have the final dimensions for all the parts that connect the two sides of each leg together. I need to start making on the lathe next. I just put in a order for various shoulder bolts from McMaster Carr, should get those Monday. I'll start work on the lathe for this first leg and anodize the lathe pieces. I may wait until the new lathe arrives, it'll be much faster than my small lathe and I can get the large parts I need to do taken care of.

    I received the optically clear 12" acrylic sphere and a a 5" diameter clear acrylic tube to mount the sphere on. This will go on the top of the computer level and will eventually contain a pan and tilt unit with a video camera attached. This will allow remote operation of the robot without actually having to be near it. Plus I think it will look cool!
  • garyggaryg Posts: 420
    edited 2013-04-11 - 16:06:49
    I'm eagerly awaiting seeing photos of your newest assembly!
    Would you be willing to disclose your source of the Optically Clear 12" acrylic sphere?
    I'm both interested in the source and exactly the acrylic material
    If it's something propriotary, I understand.
    Just wondering.
  • DiverBobDiverBob Posts: 791
    edited 2013-04-12 - 12:53:38
    The acrylic sphere and rod are sitting in a corner of the workshop for now, haven't done anything with them yet. The rod came from McMaster Carr but I'll have to find the receipt for the sphere. I just did a Google search and located that particular item.
    Didn't do anything on the robot this last days off period, came down with something that is going around work and didn't have the energy or ambition to get downtown the shop. I did receive the shoulder bolt order so now I'm set for creating the leg cross pieces on the lathe. I also got a notice that the new lathe is in PA getting the DRO installed. Should have it freight shipped in the next couple of weeks.
    My next days off is Tuesday/Wendsday so if I'm feeling better should get much more done!
  • DiverBobDiverBob Posts: 791
    edited 2013-04-17 - 16:56:26
    Spent some time on the small lathe creating some of the cross bars. I determined that I need to add some precision spacers in a few locations since the bearings are mounted in 0.25 thick aluminum and the bearings are only 0.162 thick. This means that some of the aluminum is rubbing which kind of removes the advantages of having bearings. So back to McMaster Carr to order a variety of spacers ranging from 0.005 through 0.060 thick. I'll need these installed in order to determine the final sizes on some of the cross bars so I'm done for the night.

    I got notification that the new lathe will be shipped by the end of the week, should see it sometime next week.
  • DiverBobDiverBob Posts: 791
    edited 2013-04-21 - 13:55:05
    Got the precision spacers and finished putting the first leg together mechanically. Ran into an unexpected problem when mounting the lift motor actuator. It seems the design of the actuator changed where the wiring exits the actuator. The original actuator has the wires exiting through a flexible wire restraint and the newer actuators use a hard plastic restraint that is a different position. The problem is the new wire location is right where the main leg support struts are and I can't install the actuator to the mounting block. I took the actuator apart and I'll either have to drill a new hole for the wires in the housing somewhere else or cut off the threaded wire restraint.

    The leg mechanism moves nicely and is very sturdy with almost no 'slop' when a sideways force is applied. This is important since there will be a lot of force on the sides of the legs during normal walking motions.

    The leg looks nice, will have to get the camera down in the workshop and get some photos of the first production leg next to the test leg. I still need to find a way to shine up the gold highlights on the leg, they are in recesses so they are harder to get the polish in there and then buffed out. This may have to be done by hand only. I'm liking the look so far, only 5 more legs to go!

    I need to document the cross brace dimensions and sizes, and the spacers used in each location so I don't end up disassembling this leg multiple times and all the legs are identical. That may be tonight's project before heading into work at 10PM.

  • DiverBobDiverBob Posts: 791
    edited 2013-04-28 - 23:34:19
    Finally have all the parts for one leg completed and anodized! I put together a video showing how the parts come together and what the leg looks like.

    I have almost all the parts anodized for building two more legs and then I need to finish up anodizing the rest of the already made parts. There are still some additional items to complete such as the gear trains for the other legs, the leg down switch assembly and a limit switch setup for side to side movement. The plan is still to have all the mechanical parts done in time to take this to the Unofficial Parallax get together in Norwalk, Ohio this fall.

    The attached photos are of the 8 spacers for 2 legs and the leg pivot assemblies completed and attached to the robot base.

    Hope you enjoy the video, let me know if you have any questions

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  • DiverBobDiverBob Posts: 791
    edited 2013-05-05 - 16:03:31
    Continuing on with anodizing, have adjusted my technique so I can do 4 parts in 80 minutes where it was taking me 60 minutes to do 2. I'm getting more consistent results now also.

    Cut up a 1.5 by 2.5 aluminum bar in to 5 pieces needed for the 'knee' on each leg. This part is done manually on the CNC mill because each side has work done on it and the setup for each side takes a lot of time to get it right.

    Otherwise everything is going well, one leg is 95% completed with only a few remaining parts to fabricate from scratch. The leg down micro switch block on the knee is one part to create. There is also the limit switch assembly for the rotation axis that needs to be re-done, the original layout had only one switch, the new one will use 2 switches instead. There are still 38 cross ties remaining to make for the legs (8 per leg) and gear train shafts to finish up on the lathe. That's all the parts I can think of right now. Of course that doesn't include any bright ideas I might have for revisions! I'm trying to avoid revisions unless some just flat out won't work.

    Here is a photo of the completed leg, a partially done leg and the original test leg for comparison. The next shot is the body with all the pivot assemblies attached.


    The new lathe arrived a few days ago. I've been disassembling it to get it down to a weight that I can get it into the basement with the help of a few friends! It's bigger than I imagined, don't expect to outgrow this one anytime soon!


    Stand for lathe
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  • DiverBobDiverBob Posts: 791
    edited 2013-05-15 - 14:46:22
    Finally off of night shift and after 5 days I can fall asleep at night. However, my body still thinks it should be sleeping during the day so if I slow down I start to drift off. Yesterday's budget meeting was brutal!

    Otherwise I finished anodizing another 27 parts, almost done with all the machined parts so I need to start making the final parts for the legs. This weekend I won't get too much done, Saturday, several friends are coming over to assist in moving the lathe parts into the basement. I asked for strong backs and weak minds, it seems that no one who previously helped with moving the mill to the basement are available. Once the lathe is down there I need to reassemble and clean it which will take some time.

    So there isn't much to report on, I'll keep you informed!
  • photomankcphotomankc Posts: 929
    edited 2013-05-17 - 07:33:13
    Yeah, the guy that helped me move my lathe down to the basement, was quite unavailable to assist in hauling it back out of the basement! These machines burn through your moving help in a hurry. :)
  • DiverBobDiverBob Posts: 791
    edited 2013-05-27 - 07:45:04
    No, I haven't disappeared, just busy setting up the new lathe! Finally got 220v run to it last night and after a little troubleshooting its up and running. I still need to align it but today will be a chance to make some of my spacers and see how much easier this is to use.
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  • DiverBobDiverBob Posts: 791
    edited 2013-05-27 - 15:35:25
    I've been having fun in the shop with the new lathe! Huge difference in the rigidity and ease of use from the Sherline. The Sherline is a good lathe for small parts but I've been doing so many large pieces in it I've gotten used to the compromises that were necessary. This machine is large enough I can take fewer cuts to get the needed results.

    I've been making the cross over spool pieces for the legs. These are fairly simple designs and they are good practice for getting used to the lathe.
  • DiverBobDiverBob Posts: 791
    edited 2013-06-02 - 11:55:05
    Still making cross over spool pieces, just ran out of 1" aluminum rod so had to order some more. The parts that are done are being anodized today. So far 8 are done, another 8 are being dyed and 8 are anodizing right now. Then I have 4 main leg struts to anodize and that will finish up the day.

    The new lathe is excellent! It still needs to be aligned but that isn't critical for these smaller pieces. I will have most of the parts completed for 4 legs by the end of tonight. Still have to mill out the knee blocks which is a fairly slow process but progress is still being made.
  • DiverBobDiverBob Posts: 791
    edited 2013-06-09 - 18:02:53
    Continuing work on the hexapod. Now that I know the date for the next Propellor Expo in August, I have a deadline to work against. That's always good for motivation! Anyway, this week I finished polishing all the anodized parts and then press fit 56 bearings into their holes. This makes quite a big pile of finished parts on the workbench.

    I started working on assembling the 3rd leg and decided I really needed to get working on the knee housings. With only one knee completed I have 5 more to go. Unfortunately these parts would be best done on a CNC lathe but the mill works OK, its just slower. The photos show the partially assembled leg and what the finished knee looks like.

    I cut out the 5 blocks of aluminum, these are 1.5 x 2.0 x 4, fairly nice sized blanks. All 5 blanks were machined to the required dimensions. I finished the initial screw and alignment holes are drilled on 3 of the blanks. On 2 of these I then cut off a 0.5 slice that is used as a centering device for the lower leg.

    I'll have to wait for the next weekend to do any more as I'll be away in training for my real job that pays for all my toys...

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  • DiverBobDiverBob Posts: 791
    edited 2013-06-24 - 16:48:45
    Almost done with the remaining 5 knee sections. Only have 40 more holes to hand tap until full completion! I did find a minor flaw in the new knee design that will require me to design a o-ring retainer. I should be able to make it out of thin sheet aluminum. It is needed to keep the lower centering oring in the correct position as the leg moves up and down.

    I got the warranty replacement cutting tools so I can get back on the new lathe and finish cutting out the few remaining spacers and shafts for the gearing assembly. That pretty much finishes up the metal cutting work, just a few pieces to complete anodizing and then ready to put it all together!
  • msrobotsmsrobots Posts: 3,185
    edited 2013-06-25 - 22:39:13
    I am following your progress for a while now. And I am really impressed. - Enjoy! - Mike
  • DiverBobDiverBob Posts: 791
    edited 2013-06-26 - 05:05:42
    I'm starting to look forward towards designing the controllers for the legs now. I'm planning on using the Parallax Propellor chip as the basis for the controllers. I enjoy programming them and there is a wealth of pre-made modules that can be easily plugged in for a variety of tasks. I haven't found any boards out there that have all the features I need so I will probably design my own board with the IO capabilities I want. I'm surprised how few boards have limited A/D capability, I need 8 channels for each leg and a lot of digital IO pins available for leg control and sensors. Any board I make up will be fully SMT, 4 layer as I like to make as compact a system as possible, that maximizes the design opportunities when I'm not constrained to building specific sized enclosures.

    Each leg will have its own controller, each controller will be networked together. A seperate onboard computer will be used for overall controll/coordination and process any incoming external commands from myself. Another controller will be used for general body sensors (such as tilt, GPS, troubleshooting system, etc). It will be pretty loaded computer wise when it's done!

    I'm using a Kickstarter project 32 channel digital radio system for external control. This is a pretty sweet radio that uses the propellor chip and a XM radio module, 4 potentiometers and several configurable switches. This will be the primary means of sending commands to the main controller.

    I still have to build and program all this but that will be my fall and winter project once the mechanical parts are done. Of course it won't ever really be done but this will be a fun platform to experiment with and add new sensors and capabilities over time.

  • mindrobotsmindrobots Posts: 6,506
    edited 2013-06-26 - 08:20:40
    This looks great, Bob!

    As big as it's getting, I'm almost getting afraid to go to the Expo! :lol: Should we bring Arduino boards to feed it in case it gets hungry?
  • PublisonPublison Posts: 11,507
    edited 2013-06-26 - 08:59:33
    DiverBob wrote: »

    I'm using a Kickstarter project 32 channel digital radio system for external control. This is a pretty sweet radio that uses the propellor chip and a XM radio module, 4 potentiometers and several configurable switches. This will be the primary means of sending commands to the main controller.

    I still have to build and program all this but that will be my fall and winter project once the mechanical parts are done. Of course it won't ever really be done but this will be a fun platform to experiment with and add new sensors and capabilities over time.



    Are you using this controller? It looks sweet:

    (You said XM, think you meant Xbee. Well.. a robot playing music is nice, but we want it to walk) :)

    When it comes time for modules and programming, I'm sure there will be a LOT of help from the forums. We all want to say "It's alive!"
  • DiverBobDiverBob Posts: 791
    edited 2013-06-26 - 12:06:49
    Publison wrote: »

    Are you using this controller? It looks sweet:

    (You said XM, think you meant Xbee. Well.. a robot playing music is nice, but we want it to walk) :)

    When it comes time for modules and programming, I'm sure there will be a LOT of help from the forums. We all want to say "It's alive!"

    That's the Controller - I realized I typed in Xbee wrong but forgot to go back and make a correction. Music is nice but unnecessary for this situation!

    The programming part will be interesting. I'll be using inverse kinematics to prevent the leg tips from sliding on the ground. I've found several examples of how to use IK using servos, those will have to be reworked to run with DC motors with analog feedback from potentiometers. I'm using a lot more IO than the Hexapods I've seen that use IK which is why I'm going with one controller per leg. It would be nice to be able to do it all with a single propellor board but that much IO would just be a bit too much for it to handle.

    I'm sure I'll be visiting the propellor forum a lot once I start programming to ask questions. I'm sure I will be asking for advise and help from whomever wants to get involved. It could be a fun group programming effort!

  • Ken GraceyKen Gracey Posts: 6,803
    edited 2013-06-26 - 21:06:52
    @DiverBob and Publison, our FAE Daniel Harris helped Quantum Robotics on the code for that controller. Daniel wrote some really functional, simple Spin/ASM transmitter code. I'll get him to post a copy on this thread.
  • DiverBobDiverBob Posts: 791
    edited 2013-06-27 - 03:21:07
    Ken Gracey wrote: »
    @DiverBob and Publison, our FAE Daniel Harris helped Quantum Robotics on the code for that controller. Daniel wrote some really functional, simple Spin/ASM transmitter code. I'll get him to post a copy on this thread.

    I've got the transmitter from the Kickstarter project, now I have to put it together. They have a very nice on-line guide for its assembly with lots of pictures.

    Quantum robotics also did a very nice implementation of IK in a hexapod and he shared his spin code with me to use as a starting place. There will have to be a lot of changes since he uses a single prop chip and servos and I'll have multiple props running DC motors through HB-25's using feedback for positional control. I want to utilize the existing Prop library of objects as much as possible to cut down on the programming time. There will have to be a lot of experimenting to get everything to work together smoothly. I would someday like to also implement behaviors aka Rodney Brooks style into the robot to give it a more independent existence.

    If I tried to do all this on my own it could take years to get it implemented, I'm hopeful there might be some folks out there that might be interested in a collaborative effort and see what kind of a cool monster it could be!

  • Daniel HarrisDaniel Harris Posts: 207
    edited 2013-06-27 - 10:27:52
    Hi guys,

    As per Ken's request, here is the code I wrote for the 2-gimbal Quantum Transmitter. I also wrote the mating receiver code. Note that your XBees need to be configured to serially communicate at 115,200 baud, instead of the standard 9600 baud. This is because so much data is being sent, the XBees need to be able to chuck it in/out quickly. Each packet is verified with a CRC32, and discarded if the data is invalid.

  • DiverBobDiverBob Posts: 791
    edited 2013-06-27 - 17:02:29
    Thanks for the info. I really need to assemble my transmitter and start checking it out!
  • DiverBobDiverBob Posts: 791
    edited 2013-06-30 - 10:42:10
    I'm taking a break while the next set of parts is anodizing. I can do 2 knee pieces in 72 minutes as I'm limited by the size of my power supply. That leaves one more knee and 3 lower leg sections to go! Of course there is dyeing and sealing stages to go also which will take the rest of the day.

    Very late night finishing work on the spacers. Also finished hand tapping all the 6-32 holes in the knee blocks. Then it was time to start anodizing. Only have a few pieces to finish up today but should be ready to start assembly of the remaining legs. I'm thinking I might have all the legs together by the end of next weekend! I still have to assemble the gear reduction units for 5 legs but that should go by quickly.

    I did a late night mistake on the knees, I put the numbers on upside down again! I think the robot is trying to tell me something so I'll leave it like that and just have to have a good explanation when people see it. Photos will be posted latter.

  • BrainStrainBrainStrain Posts: 30
    edited 2013-06-30 - 12:12:18
    Grins or grimace, upside down numbers are now part of the tale. My current project has seen a couple of new parts due to fabrication mistakes, but the worst mistake I ever made was 15 years ago on a wood-working project. I was making a two-drawer lo-boy dresser. The front legs had 5 mortises and a taper. The outside edges had to be rounded over on the router table, so I picked one up and promptly rounded over the wrong edge. That was a 10-hour mistake. I hope not to set a new mistake record in the future!
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