Loading ...
Sorry, an error occurred while loading the content.

Re: [SeattleRobotics] Looking to share an order of Polymorph (Polycaprolactone/ShapeLock/themo set plastic/low melting-temperat

Expand Messages
  • don clay
    Kevin, I really hope that your fiance pulls through and that the rest of you are comfortable & recovering quickly. You can get the shapelock at
    Message 1 of 24 , Mar 1, 2010
    View Source
    • 0 Attachment
      Kevin,

      I really hope that your fiance pulls through and that the rest of you are
      comfortable & recovering quickly.

      You can get the shapelock at www.shapelock.com



      From: Kevin Impson


      > Hello,
      >
      > Who is the person to communicate with about the origibak email for
      > ordering this stuff.
      >
      > Is it you Peter or John Palmisano?
      >
      > I would like to get the material, it is perfect for a project I've
      > wanted to do for a while.
      >
    • don clay
      Kevin, I really hope that your fiancee pulls through and that the rest of you are comfortable & recovering quickly. You can get the shapelock at
      Message 2 of 24 , Mar 1, 2010
      View Source
      • 0 Attachment
        Kevin,

        I really hope that your fiancee pulls through and that the rest of you are
        comfortable & recovering quickly.

        You can get the shapelock at www.shapelock.com



        From: Kevin Impson


        > Hello,
        >
        > Who is the person to communicate with about the origibak email for
        > ordering this stuff.
        >
        > Is it you Peter or John Palmisano?
        >
        > I would like to get the material, it is perfect for a project I've
        > wanted to do for a while.
        >
      • Peter Balch
        Kevin, ... It s John. I d love to split an order but I live in Scotland. So unless you re just round the corner ... Peter
        Message 3 of 24 , Mar 1, 2010
        View Source
        • 0 Attachment
          Kevin,

          > Who is the person to communicate with about the origibak email for
          > ordering this stuff.
          > Is it you Peter or John Palmisano?

          It's John.

          I'd love to split an order but I live in Scotland. So unless you're just
          round the corner ...

          Peter
        • Peter Balch
          David Thank you for all those figures. 10-15km is 2-3 million steps. That requires resonably good engineering. 10 hrs for Wild-Eagle is maybe 20,000 steps. I m
          Message 4 of 24 , Mar 1, 2010
          View Source
          • 0 Attachment
            David

            Thank you for all those figures.

            10-15km is 2-3 million steps. That requires resonably good engineering. 10
            hrs for Wild-Eagle is maybe 20,000 steps. I'm sure polymorph would have no
            problems with that.

            To me, I think it depends on why you're building the robot. I suppose most
            people's anwer would be to learn - for their own interest or to advance
            robotics research. So the robots that you've had on display are retired.
            They may be working harder than they did when they had a job but they are no
            longer active for your learning. (Of course, if you build a robot for, say,
            a museum display then its job is to move all day, every day and it must be
            built to do that. But only one in a thousand home-brew or university robots
            has that sort of life.)

            So my guess is still that polymorph hinges are perfectly good for 99.9% of
            (non-industrial) robots.

            > A pertinant question is how much energy does it take to flex a polymorph
            > hinge?

            Energy or torque? The hinge is springy so any energy you put into it to flex
            it is recovered when it straightens. I kept feeling the hinge while it was
            being flexed for its 10,000 trials and it didn't get warm so I guess that it
            wastes little energy.

            A friend suggested that if it begins to fail, it will be self-healing.
            Cracks can't propagate because the extra energy loss at the crack tip will
            raise the temperature and soften the polymorph, hence healing it. It's a
            nice idea if it's true.

            Of course, the next question is, how do you recover the stored energy? How
            do you make use of the springyness? If the hinge is connected to a servo
            (via a typical model-aircraft style wire con-rod) then the servo will
            probably be unable to make use of that stored energy. I guess it will depend
            on the design.

            The torque needed to bend the hinge is very roughly 0.15kg.cm/radian. The
            hinge region is 0.65mm thick less than 1mm long and 10mm wide. I suppose it
            all scales roughly linearly. (Or will it go up as the square of the
            thickness? - it's a long time since I learned about bending beams.)

            If a hinge typically bends 1rad during a stride then 0.15kg.cm is about a
            twentieth of the torque of a standard servo. If you've designed the leg
            properly then maybe that 0.15kg.cm can be used to partially support the
            weight of the robot.

            > It may be desirable in say a foot which needs to deform to absorb footdown
            > loads, but otherwise?

            Otherwise? You mean why bother with a polymorph design rather than the
            standard hexapod legs where the servos act as the joints? Standard hexapod
            legs may be the best design but I feel too few robots explore other
            possibilities. Standard hexapods are a cliche. Cliches aren't neccessarily
            wrong but it's always good to question them. Homebrew and university robots
            are for learning and you don't learn much about the physical design of a
            robot from Yet Another Standard Hexapod.

            If you're using polymorph then (I think) you have to use model-aircraft
            style con-rods. They don't have to be wire con-rods; they could be part of
            the single piece polymorph leg. So the new design has two independent
            features:

            (1) it uses con-rods
            (2) it's made of polymorph

            Con-rods have certain advantages. You can put the servos in the body - not
            on the joints. You can use the full rotation of the servo: if a typical
            servo can manage almost 180deg but the leg only swings 60deg then the
            con-rod can give you almost a 3:1 mechanical advantage. You can arrange the
            servos to give "unusual" motions to the leg. (I find it hard to design
            linkages like that from scratch so I've written a two-servo linkage
            editor/simulator. I'll upload it if people are interested.)

            Is polymorph worth using? I don't have any experience. As I've often said
            here before, robots are for learning. If you're learning then you don't know
            what you're doing; possibly no-one knows. Engineering is for when you do
            know what you're doing. Therefore 99.9% of robots should *not* be
            engineered. They should have a design life of hours, not years. Robots
            should be made of popsicle sticks and hot-glue. Polymorph *may* be a good
            material for lash-ups. If you don't like the design, it's cheap and easy to
            soften the polymorph and change it. How often have you thought "well, the
            design looked good on paper but I wish I'd made that part 1cm longer and now
            it's too much trouble to change it"?

            (I know that a lot of people like standing at their milling machine making
            beautifully crafted/engineered designs. I enjoy it too - it's a form of
            zen-like meditative relaxation. But that's a separate issue from making
            robots.)

            Personally, I spent many years working with crabs and thinking what
            fantastic robots they are. The few polymorph robots on the web have a
            wonderful organic look. It's probably a great material for making robot
            crabs.

            As I asked before:
            > If you were making a
            > 3 DOF one-piece polymorph leg, what sort of design would you choose?

            The answer is not obvious to me.

            Peter
          • David Buckley
            Hi Peter I agree with everything you said although the Amblers and TecFoots are all under development - still. Just bought some mid range Sharp IR rangers to
            Message 5 of 24 , Mar 1, 2010
            View Source
            • 0 Attachment
              Hi Peter
              I agree with everything you said although the Amblers and TecFoots are all under development - still. Just bought some mid range Sharp IR rangers to put on TF-Condor, one to add to the object detection and more importanly so it doesn't walk off a table when I forget and turn round. Fortunately because of the 4mm Birch Ply repair was easy. Although the 'Ironware' is more or less fixed the software and hardware are still changing.
               
              For the record Simplhex's legs were aluminium (hand filed) with a joggle in them to reduce the axial torque loads on the servos, would I do it that way again - no, plywood is so much easier even though for me they took very little time..
               
              The standard Hexapod design and in fact the standard robot design of attaching the limb to the servo is reaching a dead end even though that is the way Industry does it. Passive compliance will make everything work better providing standard IK techniques are abandoned.
               
              I do have a tub of Polymorph and some sheets of similar material used in ct-scan support courtesy of Roger and have been thinking it would make good dragon(dinosaur)  feet which are passively compliant. Could probably make pockets for QTpills!
               
              David
               
               
               
               
              ----- Original Message -----
              Sent: Monday, March 01, 2010 1:15 PM
              Subject: Re: [SeattleRobotics] Looking to share an order of Polymorph (Polycaprolactone/ShapeLock/themo set plastic/low melting-temperature polymer)

               

              David

              Thank you for all those figures.

              10-15km is 2-3 million steps. That requires resonably good engineering. 10
              hrs for Wild-Eagle is maybe 20,000 steps. I'm sure polymorph would have no
              problems with that.

              To me, I think it depends on why you're building the robot. I suppose most
              people's anwer would be to learn - for their own interest or to advance
              robotics research. So the robots that you've had on display are retired.
              They may be working harder than they did when they had a job but they are no
              longer active for your learning. (Of course, if you build a robot for, say,
              a museum display then its job is to move all day, every day and it must be
              built to do that. But only one in a thousand home-brew or university robots
              has that sort of life.)

              So my guess is still that polymorph hinges are perfectly good for 99.9% of
              (non-industrial) robots.

              > A pertinant question is how much energy does it take to flex a polymorph
              > hinge?

              Energy or torque? The hinge is springy so any energy you put into it to flex
              it is recovered when it straightens. I kept feeling the hinge while it was
              being flexed for its 10,000 trials and it didn't get warm so I guess that it
              wastes little energy.

              A friend suggested that if it begins to fail, it will be self-healing.
              Cracks can't propagate because the extra energy loss at the crack tip will
              raise the temperature and soften the polymorph, hence healing it. It's a
              nice idea if it's true.

              Of course, the next question is, how do you recover the stored energy? How
              do you make use of the springyness? If the hinge is connected to a servo
              (via a typical model-aircraft style wire con-rod) then the servo will
              probably be unable to make use of that stored energy. I guess it will depend
              on the design.

              The torque needed to bend the hinge is very roughly 0.15kg.cm/radian. The
              hinge region is 0.65mm thick less than 1mm long and 10mm wide. I suppose it
              all scales roughly linearly. (Or will it go up as the square of the
              thickness? - it's a long time since I learned about bending beams.)

              If a hinge typically bends 1rad during a stride then 0.15kg.cm is about a
              twentieth of the torque of a standard servo. If you've designed the leg
              properly then maybe that 0.15kg.cm can be used to partially support the
              weight of the robot.

              > It may be desirable in say a foot which needs to deform to absorb footdown
              > loads, but otherwise?

              Otherwise? You mean why bother with a polymorph design rather than the
              standard hexapod legs where the servos act as the joints? Standard hexapod
              legs may be the best design but I feel too few robots explore other
              possibilities. Standard hexapods are a cliche. Cliches aren't neccessarily
              wrong but it's always good to question them. Homebrew and university robots
              are for learning and you don't learn much about the physical design of a
              robot from Yet Another Standard Hexapod.

              If you're using polymorph then (I think) you have to use model-aircraft
              style con-rods. They don't have to be wire con-rods; they could be part of
              the single piece polymorph leg. So the new design has two independent
              features:

              (1) it uses con-rods
              (2) it's made of polymorph

              Con-rods have certain advantages. You can put the servos in the body - not
              on the joints. You can use the full rotation of the servo: if a typical
              servo can manage almost 180deg but the leg only swings 60deg then the
              con-rod can give you almost a 3:1 mechanical advantage. You can arrange the
              servos to give "unusual" motions to the leg. (I find it hard to design
              linkages like that from scratch so I've written a two-servo linkage
              editor/simulator. I'll upload it if people are interested.)

              Is polymorph worth using? I don't have any experience. As I've often said
              here before, robots are for learning. If you're learning then you don't know
              what you're doing; possibly no-one knows. Engineering is for when you do
              know what you're doing. Therefore 99.9% of robots should *not* be
              engineered. They should have a design life of hours, not years. Robots
              should be made of popsicle sticks and hot-glue. Polymorph *may* be a good
              material for lash-ups. If you don't like the design, it's cheap and easy to
              soften the polymorph and change it. How often have you thought "well, the
              design looked good on paper but I wish I'd made that part 1cm longer and now
              it's too much trouble to change it"?

              (I know that a lot of people like standing at their milling machine making
              beautifully crafted/engineered designs. I enjoy it too - it's a form of
              zen-like meditative relaxation. But that's a separate issue from making
              robots.)

              Personally, I spent many years working with crabs and thinking what
              fantastic robots they are. The few polymorph robots on the web have a
              wonderful organic look. It's probably a great material for making robot
              crabs.

              As I asked before:
              > If you were making a
              > 3 DOF one-piece polymorph leg, what sort of design would you choose?

              The answer is not obvious to me.

              Peter

            • David Buckley
              Just a little thought on Polymorph. It is an interesting low friction material and capable as is Acetal (Delrin) of forming both halves of a bearing, unlike
              Message 6 of 24 , Mar 1, 2010
              View Source
              • 0 Attachment
                Just a little thought on Polymorph.
                 
                It is an interesting low friction material and capable as is Acetal (Delrin) of forming both halves of a bearing, unlike nylon, and as you have shown it makes acceptable hinges.
                 
                The Crabfu and Heart-project creations do have a biological look to them.
                However they knew what they were making before they started.
                 
                It is no good having warmed Polymorph and pushing it this way and that expecting, miraculously, a robot will rise up like the T2000 morphing from the floor to a cop.
                 
                I know there are those who think they can create their robots as a CAD model, however this doesn't seem to work otherwise we would be awash with neat robots. There is always something missing in a CAD model, generally gravity.
                 
                I find it is much simpler to stack up the servos, battery boxes, circuit boards etc on cups, erasers, bits of wood, etc, in the general desired configuration and then it is easy to take measurements.
                 
                You have got to know what you are building before you start. The CAD program isn't going to do it for you and neither is Polymorph.
                 
                David
                 
                 
                 
              • Peter Balch
                David ... Do you mean this: http://www.heartrobot.org.uk/ I hadn t seen that one. I was thinking more of the LetsMakeRobots finger/hand and:
                Message 7 of 24 , Mar 1, 2010
                View Source
                • 0 Attachment
                  David

                  > Heart-project creations do have a biological look to them.

                  Do you mean this:
                  http://www.heartrobot.org.uk/

                  I hadn't seen that one. I was thinking more of the LetsMakeRobots
                  finger/hand and:
                  http://www.xrobots.co.uk/android10part2/
                  http://expo21xx.com/automation21xx/17887_st3_university/default.htm

                  and, to a lesser extent, these
                  http://www.youtube.com/watch?v=dqXTluYT8xU
                  http://www.youtube.com/watch?v=dVbD9Ga0_Js

                  The ECCCEROBOT looks amazingly cool. I have real doubts that it could ever
                  walk but, when it looks that cool, who cares.

                  Peter
                • David Buckley
                  Hi Peter Yes I did mean Heartpupet ECCCER may look cool (lots of bits) but it is safe only because it is hardly strong enough to lift its limbs. ECCCER is
                  Message 8 of 24 , Mar 1, 2010
                  View Source
                  • 0 Attachment
                    Hi Peter
                    Yes I did mean Heartpupet
                    ECCCER may look cool (lots of bits) but it is safe only because it is hardly strong enough to lift its limbs. ECCCER is actually Chronos-2. I don't know who is actually making ECCCER or how it got to Zurich but Owen Holland must have thought he had hit paydirt, somebody who can fabricate something so they can take publicity videos.
                     
                    When you said about it walking you did mean the Xrobots android didn't you
                     
                    I am not impressed with either since they are just not powerful enough to do much let alone walk.
                    I am impressed though with Xrobots' enthusiasm and perseverance especially after his house burned down destroying his earlier bipeds.
                     
                    To put things into perspective, the main engineer at Shadow is Hugo who is in charge of all the mechanics and electronics and sadly only the low level software.
                    Back in the late 80s when he was only 16 he started to come to the Shadow Group weekly meetings. He didn't talk to anyone but started to build a pneumatic articulated hand/arm/shoulder using air muscles and a wooden skeleton. It was much smoother and stronger than that in the  ECCCER videos and was the same size as a human arm, ie it would fit in a normal jacket sleeve. Hugo went to take a degree then returned to work at Shadow.
                     
                    The thing is that it is hard enough to make robots that work without getting beguiled by those that look cool but don't work, you know the type, the big forest fire fighting robot designs which are like two fused candlesticks with no chance of being able to lift a foot from the ground without falling over. Or KW's biped on my walking mechanisms page which must have caused disappointment at DPRG because it may just walk if the engineering is really really sloppy.
                     
                    The problem with Polymorph is that it is not cheap, unless you are a university. So we should use more appropriate materials for skeletons and frames. Balsa is strong, easily glued with Cyano and can be carved as you wish, Teal (1955) is balsa, a lot of Kunibert (1965) is balsa.
                    Use Polymorph for the bits where otherwise you would need a machine shop.
                     
                    David
                     
                     
                    ----- Original Message -----
                    Sent: Monday, March 01, 2010 10:20 PM
                    Subject: Re: [SeattleRobotics] Looking to share an order of Polymorph (Polycaprolactone/ShapeLock/themo set plastic/low melting-temperature polymer)

                     

                    David

                    > Heart-project creations do have a biological look to them.

                    Do you mean this:
                    http://www.heartrob ot.org.uk/

                    I hadn't seen that one. I was thinking more of the LetsMakeRobots
                    finger/hand and:
                    http://www.xrobots. co.uk/android10p art2/
                    http://expo21xx. com/automation21 xx/17887_ st3_university/ default.htm

                    and, to a lesser extent, these
                    http://www.youtube. com/watch? v=dqXTluYT8xU
                    http://www.youtube. com/watch? v=dVbD9Ga0_ Js

                    The ECCCEROBOT looks amazingly cool. I have real doubts that it could ever
                    walk but, when it looks that cool, who cares.

                    Peter

                  • Peter Balch
                    David ... What s TF-Condor? How is it different? ... Where do you get the ply cut for kits? It doesn t seem to be as straightforward or competitive as getting
                    Message 9 of 24 , Mar 2, 2010
                    View Source
                    • 0 Attachment
                      David

                      > Just bought some mid range Sharp IR rangers to put on TF-Condor,

                      What's TF-Condor? How is it different?

                      > Fortunately because of the 4mm Birch Ply repair was easy.

                      Where do you get the ply cut for kits? It doesn't seem to be as
                      straightforward or competitive as getting pcbs made. Most kits seem to be
                      stamped, not laser-cut.

                      > When you said about it walking you did mean the Xrobots android didn't you

                      Yes, you're right. I was confused by all that polymorph.

                      > The standard Hexapod design and in fact the standard robot design of
                      > attaching the
                      > limb to the servo is reaching a dead end

                      I was googling photos of as many quads and hexes as I could find (homebrew
                      and uni) and there seemed to be none that didn't either have the servos as
                      the joints or have 2 out of 3 servos as the joints and the third one had a
                      parallel linkage to the joint. It's really dull. Not neccessarily bad but
                      definitely unimaginative. I don't believe that many (any?) other
                      configurations have been investigated.

                      I've just uploaded ServoLinks.zip which allows you to edit linkage
                      mechanisms and "run" them. There are some fairly obvious designs (e.g. 1)
                      and some wacky ones (e.g. 11, 12 and 4). It can tell you useful things about
                      the mechanisms. How high can the front of the foot step to get over
                      obstacles? Are there any "near-singularities" where the conrod/axle becomes
                      too straight and the joint might bend the wrong way? If the 'X's in the path
                      of the foot too far apart - that (maybe?) indicates poor mechanical
                      advantage.

                      Peter
                    Your message has been successfully submitted and would be delivered to recipients shortly.