Author Archives: timesuptim

Francis Bacon

“Whether or no any thing can be known, can be settled not by arguing, but by trying.”

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Whip It (Example) Part 3

The following is an example workshop blog posting.

This is the third post, showing the end result (for now).

Given the simple motion that was built, the next step is to make it whip. A 2.5 meter length of hemp rope was spliced into the eye bolt that was mounted at the end of the wood handle. This splicing should make the connection flexible and smooth. It was guessed that a knot might be a nonsmooth transition, which might then cause a less coherent transfer of movement from the handle to the rope / whip.

The following video was then made, with bad lighting conditions, showing the movement of the rope. The recording was made from the very beginning, to see whether any interesting motions happened then, but as there was nothing special happenning then, that part of the video was removed.

The motion that seems interesting is the looping that occurs, the swooping and then tugging the rope into a loop that then moves along the rope.

Next steps that offer themselves:

  • adapt the rope, especially in terms of tapering it, to add to the whippiness.
  • Longer rope might have more loopiness arising
  • Or will a shorter rope allow more of it to hang in the air.
  • Similarly a lighter rope.
  • Or a cracker at the end.
  • Might a stroboscope be interesting, to see the stages of the motion.

Whip It (Example) Part 2

The following is an example workshop blog posting.

This is the second post, showing the planning.

By imitating the hand movement of whip cracking, it became apparent that the motion is a cyclic motion, probably close to an oval, with acceleration around one end and side, i.e. one “corner” of the oval. Given that the easiest motion to create is a circular one from a motor, this led to a quick look at how this conversion might be made. The sketch shows the sort of motion that seems like it would come out. The arrow on the oval shows the section where the drive motor (the circle) is closest to the guides, and through the leverage, would cause the fastest motion.

Very abstract motion

Very abstract motion

Thoughts about a roller at the guide (where the lines cross in the middle) and friction come up, forces and other factors. With some sketching, it becomes clear that hanging the device so that the motor is at the top would mean a lot less effort and friction.

The motor that is available is a widscreen wiper motor, the friend of the quick hack maker. With some sketching and dimensioning, the following sketch was created:

A sketch of the whole assembly

A sketch of the whole assembly

At this stage, through various processes, the guide has been placed at the top. The motor drives a 40cm flat piece and the handle has been made into a piece of wood that should then flick the rope. To get a decent amount of flicking, the plan is to hang the piece three meters from the ground.

Astute lookers will see that there is at least two errors that have emerged in this diagram. These will become apparent in the building process.

The next step is to design the pieces that are to be cut. One flat steel piece from the motor to the handle, another to connect the motor and the guide and to be attached to a fixed point. Slowly the dimansions become apparent.

The parts

The parts

The lower sketch shows the driver: a 9mm hole for the motor attachment, 6.5mm for the bolt to attach to the wooden handle. The bolt will spin in this hole, so it is a bit larger than to really needs to be.  The upper sketch shows the two guides as steel rod welded on the side of the flat steel. Then two holes for the mounting, then the holes and cut-out for the motor. Now we know hos long the pieces need to be, so time to cut and drill.

The metal parts

The metal parts

There was some details to work out: countersinking holes to get screws and bolts out of the way, cutting the notch in the mounting steel to let the axle of the motor stick through. With a few pieces of wood we assembled it all.

The Raw Assembly.

The Raw Assembly.

Assembling everything let us see a few problems. The handle wood length is not as planned. Luckily I had cut it longer than the planned 120cm: the distance from the bottom end of the driving circle movement to the guide is not 40 (radius) + 10 (to the guide)+10(for safety) = 60cm but rather 80 (diameter) + 5 (to the guide) + something (for safety) > 85cm. Oops. So the wood was re-drilled. This should have been clear from my sketch.

This leaves only a small section of handle to attach the rope to (see eye bolt in there).

Once the driving arm had been bent to keep it clear of the structural arm and the structural section smoothed to lower friction and stop things touching, the assembly could be given a dry test.

Here we notice the second error from the sketch. Originally the guide was in the middle, now it is at the top end. So the best motion is actually happening at the top end of the device.

This ends the first section of building. Using sketches, photos and video, we can see some basic motion. Next post will look at the adaptions that can be made in response to these observations.

 

 

Whip It (Example) Part 1

The following is an example workshop blog posting.

This is the initial post, showing the inspiration.

Walking home on New Year’s Day several years ago, I came across the Aperschnalzen in front of the Landhaus in Linz. An alpine tradition, imagined by some to be an impulse to get the snow away through the cracking of whips.

A “Pass” whipping in a coordinated fashion.

Thus the idea of a coordinated set of whipping machines was planed in my head, getting rid of the knickerbockers and having a group of machines that could whipcrack. There is an international history of whipcracking, from the Jackaroos in Australia and the cowboys of north America, with a whole performance aspect that is important as well. The idea also fits in well with Gordon Monohan’s Swinging Speakers piece.

Speakers on the end of ropes. Click on image for a video.

Whips can be a complex assembly, the number of books about whipmaking using kangaroo skins and other leathers, is astounding. Discussions about tapering, different materials, diameters, plaiting, etc abound.  The Aperschnalzen whips are, luckily, a lot simpler. Essesntially a stick with a rope attached on the end. The proper ones are tapered too.

A Goassl, showing the loose connection between the stick and rope whip. The Bast or cracker is very light.

This tapering is, according to a physical analysis, not necessary. It also seems that the motion could be a lot simpler: there is a simple curved motion described in the analysis paper. This seems less complicated than this image, which I think shows a strobed whipcracker at work:

So my plan is to try and emulate this motion. I need a stick of sorts to be the handle for the whip, some assembly to make it move like a whip cracking handle and a rope to be the whip.

 

 

Meditations on explorative machine art

Please do not forget that you are not expected to make a working piece of machine art in this workshop. You are expected to make a machine that does something, perhaps what you intended, probably something different. Then take the difference and amplify it. So planning and observation are two core elements.

Some reminders, stolen from Oliver Kellow:

  •  Keep the stakes low: more small, cheap experiments instead of one big build
  •  *terative design: keep building and testing and observing and building and testing and….
  •  You are storing up observations and experience for the future
  •  There are no immediate returns
  •  Do not force things: follow the motions that your machine makes and make them more
  • Don’t forget to laugh when it goes hilariously awry

 

Interface Cultures Robotics 2012 starts tomorrow

We are looking forward to greeting the IC class tomorrow for some more robotical investigations, in the widest sense of the words.

Final Day: Presentation!

Day 4 and the weather is being nicer to us. I see some blue sky.

It is all easier, as well as harder, than it looks.

Most of the projects are moving forward nicely, however many have fallen prey to the “Waterfall” or “Ballistic” method of production: at the beginning all is planned, then it is built and at the end it should all come together. It has proven useful to many of us to “always have a running system” – part of the “Agile” framework for development.

So today we will see how the plans and sketches and building comes together. Everyone has learnt to do something that they would have otherwise been terrified of (including myself!) – so in that sense we already have a success.