Meryl Grandy

Here is a video showing my latest installation work, Machine for Preserving the Wind. Its up till June 30th, 2011 atTruck Gallery in Calgary, Alberta, Canada.

There is also a review of the show up here at FFWD Weekly.

Oh, and Adam Savage tweeted a link to my sculpture, my inner geek is unspeakably happy.



Each of the 40 poles that make up the piece are mounted on a string pivot, allowing them to sway freely. They have a cast concrete counterweight at the bottom that balances the wooden pole so they can sway with the slightest movement. These are then connected with a series of strings that allows them to be pulled back, and released to sway freely on their own. In this way the poles are indirectly coupled to the drive mechanism, they can be pulled back, but then they are free to sway and swing on their own, resulting a much more organic and random movement than if they were directly coupled.

To drive this mechanism the poles are connected to a pair of large wooden cams. A cam is basically a wheel with an irregular shape that causes a follower on the wheel to move back and forth in a fashion reflecting these bumps. In this case each bump outward corresponds to a gust of wind, and pulls the poles backward. The two wheels turn at slightly different speeds, and the output of each is mixed and averaged, resulting in a program that takes over 14 minutes to repeat.

The cam wheels themselves are driven by a multi stage reduction drive. An electric motor, of the type usually used in a household furnace, is hooked up to a worm drive speed reducer, and then to a two stage chain drive, this setup brings the speed of the motor down from 1725rpm at the input to half of an rpm at the output, a reduction of over 3000:1, this process increases the torque from half a foot pound, to over 400 foot pounds after friction losses. This was fun to design.

This is a cable driven drawing machine I constructed for the Telus Spark Science Centre in Calgary, Alberta.

Each of the four stepper motors is connected to a pulley and string. By winding in or letting out string on each corner the computer can position the draw head anywhere in three dimensional space, or at least within its work envelope of roughly 590x590x220mm.

The machine is controlled with LinuxCNC using a custom kinematics module and python script written by Kevin Loney. Its input files are standard g-code, the same format used for controlling a CNC mill, all the weird coordinate transformation math is handled by the kinematics wrapper.

More construction info and photos after the video,



By far the hardest thing on this build was getting the machine to to home fully automatically. For those new to motion control, I am using stepper motors, these are open loop which means that I can move them incrementally, but I have no idea where they actually are. To determine their current state, I have to move them to a known position, and call that home. This is fairly easy on a traditional CNC machine where each axis is independent and on guides, but quite painful when all four are tied together and made of string.

Many ideas were floated to solve this, from IR range finders, to vision based systems with openCV and a webcam. Finally for reliability I settled on simple switches.

From here though, there are two main problems, first, how do you trip a switch with a length of string, and second how do you keep everything taught and tangle free when you haven't got a clue where the drawhead is starting from.

The switches were the easy(er) part, the first attempt used a magnetic reed switch mounted over the fairleads (cable guides), and neodynium ring magnets mounted to the draw head.  Once the magnets got close to the switch it would trip and tada! That was the theory at least, in practice they would fail to trip half the time, the magnets would stick to any ferrous metals in a 6 inch radius, and that was just the start of the problems. I got around some of the issues by using larger magnets, and brass screws, but it was really unworkable.

The final solution was to build custom rocker switches around the fairleads. They were spring loaded so that as the head was drawn into them, they would fold back and trip a small lever switch. They still had to be strong enough to keep the cable in the same position and they had to be rigid enough to not accidentally trip under normal load. Good times.

Now, to get the drawhead to trip the switch I have to have slack from the opposite side. The first thing I tried was to just spool out cable on one motor as I spooled in on the other. For a two cable machine this technique works great, once you get two more cords in the mix, and a lack of space to use gravity to keep things taught, a lot of tangles result. The solution was a bit of a hack, but one I am rather proud of. Stepper motors have no direct mechanical connection between the shaft and the body of the motor (well, other than the bearings), its the magnetic field in the coils that causes the shaft to turn. This means that stepper motors can slip without damage if the force on the shaft exceeds the holding torque of the coils. Further, the stepper motor driver I am using allows the current going into the motor to be adjusted with a resistor which then adjusts the holding torque. Yup, that's right, the motors have a tug of war. One is stronger than the others so it just reels it in with some enthusiasm, everything stays taught and you are off to the races.

This video shows the switches getting hit, I need to upload another video showing the unholy chunking and shaking that happens during the tug of war phase.



The construction of this machine was a mixture of hand machining, carpentry and a bit of laser cutting for the towers and overwrap guides. The head is replaceable, for the early tests I had a larger head that could mount a pen and do some fairly accurate drawings, only issue was that in a more resistive material like sand it tended to flop around a lot.

Free sailboat machine embroidery designs can be considered one of necessary . beneath at this point Can certainly belonging to the listing google and yahoo In an effort to deliver worthwhile material to our followers we now have experimented with to get your nearby relevance photographs all-around Free sailboat machine embroidery designs Together with at this point you might look at these days, these kinds of photos are already obtained out of your prominent powerful resource.

Many are available for save, if you need along with would like to get it simply click protect badge at the website page, along with it’ll always be instantaneously delivered electronically in your own notebook computer. Finally to be able to get innovative and even most recently released image relating to Free sailboat machine embroidery designs , make sure you adhere to all of us upon search engines in addition or even save this site, many of us effort each of our ideal to offer you day-to-day bring up to date through impressive and even innovative subject matter. Produce your own . that suits you each of our site.

Free sailboat machine embroidery designs - it has ended up created while using the expectation that'll you’re able to rejuvenate necessary just about anyone. This may well perform in the form of benchmark for all those confounded to find the most suitable help The Free sailboat machine embroidery designs items may well be your current decision to get used on the project prepare, while it includes unique system is going to come to feel extra contented Free sailboat machine embroidery designs - Very helpful for you personally hence most people attempt to obtain an honest supplier which often will let you see drive free of indecision. keep in mind to help search for this site, considering that it could be a day you require it again spine seeing that ones inspirational thoughts.