Sunday, November 16, 2008

The Long-Lost Tilt-O-Rama Construction Details!

In a previous post I promised to find some more of the construction details of the "Tilt-O-Rama" rework. After scouring some old computer drives, I finally came across the rascals:

Prototyping the "Crow's Nest": The design of what we were delivered was a clunky device that would only accommodate the most average of passengers. If I was to improve upon it, I needed to make sure that it would fit most (if not every) person that approached it. I did not want to see another show where the presenter was a lousy judge of height or girth and had to send the volunteer back to the audience when they didn't fit.

To be fair- being a huckster is a high pressure business, and mistakes can easily be made in the heat of the moment. It is not really the presenter's fault, but that of poor design.

To facilitate the design process, I devised a prototype "nest" whose configuration could easily be adjusted. It was a dog's breakfast of clamps, unistrut, MDF, and a sawhorse - but it allowed me to take our largest and smallest employees and perform a "fitting."

After I was satisfied that the contraption would safely hold the entire human bell curve, I used the prototype as a template to render the final product in steel. The slanting hand-holds provided a comfortable grip-distance for large and small, while the "bail" would entirely encompass the passenger such that they could not fall forward. Unlike the original, the participant could now "throw their weight around" as there was great freedom of movement of the person's center of mass.

The "bail" could be quickly closed and secured by employing a device constructed from coil threaded rod and a giant wing-nut. This is used in make molds for contrete, as the threads are not easily fouled because of their loose tolerances. To make the latch, I made a length-wise split slightly past the center of the rod's axis. This allows the wing-nut to travel the entire length of the rod without binding - even if the bail is not closed. Powder coating had no effect on the operation of the threads.

To use, the presenter closes both halves of the bail (the small pin in the center provides registration - a bit of over-kill there) and gives a wing of the nut a sharp smack. The nut spins easily down the halves securely joining them. The wing-nut is trapped by a steel disc on the end of the rod - there is nothing to lose.

Here is a better detail of the ankle-cuff system before it was placed on the "Tilt-O-Rama." You can now see how the Suspa cylinder advances the racks to simultaneously rotate the cuffs. The Suspa system is normally used for raising and lowering workbenches and depends on the weight of the bench for the system to be lowered. Since gravity was not helping me here, I had to place a pair of large constant-force springs on each of the cylinders to give them the needed assist when cranking them back open. Somewhere I am hoping to find some grainy video I took with my Palm of the mechanism in action.

My Museum Clan

Our museum's director took another position this Fall, and the staff put together a web-published book for her as a parting gift. I had my department stage this photo in front of our cave exhibit as our contribution to the project. Yours truly on the left. The Education department kindly loaned us the skins.

The guy standing in the middle is our cabinetmaker. His image looks a little off as he had to be photo shopped in afterward. He was insistent on getting a haircut before the shoot (apparently unclear on the concept of "look like cavemen") and didn't make it back in time. The shoot had to happen before the public came at 10 am and he didn't make it back.

All in all we think it turned out OK.

Wednesday, June 11, 2008

Witness the Tilt-O-Rama!

This unit for The DSC was used to demonstrate center of mass, rotational inertia, periodic motion, and to generally scare the living crap out of it's passenger. It was not for their entertainment, but for the rest of the audience (family, friends, spouse, students) when they saw the expressions of shock and horror.

It was built from my design by a Canadian company that shall remain nameless. (In fact, I believe that they are either out of business or operating under a different name.) Like most things built by this firm it needed extensive rework for safety and decreased maintenance.

In this case the entire passenger restraint system had to be redesigned and rebuilt. Also added: A bumper system to the central column, a system that held the payload at-rest during loading/off-loading, and air-pads on the feet that allowed us to move this massive device anywhere on the floor with remarkable ease.

Originally the "Crow's Nest" featured a bastardized fall-safety harness. This took too much time to properly fasten during a demonstration, and was usually done half-heartedly. Also, it did not provide enough freedom of movement for the participant to shift their center of mass around to get the Tilt-O-Rama a rockin'.

I replaced their kludge with a system that allowed quick and safe operation. While one operator was closing a guard that completely encircles the passenger, another at the ground level was turning a crank that hydraulically advanced "hand-cuffs" around their ankles. Now the visitor could shift their mass over a foot in 360 degrees, while the ankle restraints prevented them from stepping off the platform

Here is a detail of the hydraulic system that advanced the 'cuffs.

Here is another that shows one of the slave cylinders. When the crank is reversed the two large constant-force springs draw the cylinder back to it's original position. Hidden from view is the rack and pinion that provides the rotary motion to the 'cuffs.

If I can find more detail photos of the mechanisms, I'll add them to this post.

Wednesday, May 28, 2008

Riding on a Thin Film of Air...

When I was hired as an exhibit designer at the Detroit Science Center in 2000, the then president Mel Drumm said "Build me an air car." I wish he asked me to produce a jet-pack, but what the hey. We were on such a short time-line (the Center's renovation/expansion project had been pushed up for the city's Tricentennial in 2001 - less than a year away with nothing yet planned) that much of our work had to be subcontracted. This was the one project I set aside for myself to execute from start to finish.

The unit was to be used in hourly presentations on our "Science Stage," a 250-seat theater that was the heart of the new addition. Among other things, it would be used to demonstrate weightlessness in two dimensions. An important part of the car that never seems to be talked about - the floor. Our was a terrazzo that was flat to +/- 3/32" over 32'. The story of it's design and installation will have to wait for another post.

For the grand opening the car was a simple triangular platform of aluminum extrusions supported by three air pads that was shoved around the floor. Soon after opening, I began on the next iteration: directional jets.

As luck would have it, there was a group of gents from a local company that produced air-logic systems that were wanting to have some fun. They graciously contributed materials and expertise and time to develop a control system for the jets. Moving the joystick would apply thrust in X and Y directions, while the thumb knob would provide positive or negative rotation. Sorry - no Z.

In way of thanks, for the final installation I had a photo-anodized plaque made of their friend and company founder, Bill Carls. We placed it right on the control panel that housed the air-powered brains.

How well did it work? We were all pretty happy with the speeds achieved and the response, but if you really leaned on the jets it ate up the air faster than we would have liked. That was the limiting factor - how big of a compressor can I fit down this hole cut in the floor before it gets bricked up like a cask of Amontillado? The compressor was located in a mechanical room a couple of hundred feet way - even further as it was piped. We eliminated as many transitions in the pipe as we could to better the efficiency and installed a 200 gallon receiver tank about 50' from the car, but we could only do so much. As for the car itself, lightness was sacrificed for ruggedness. I am sure that I could have reduced the mass of the car by a third or more.

Future plans that I didn't get to before I left for Oklahoma:

Crash Land on Mars - The car would "orbit" via a tethering cable connected to a rotating hub in the center of the floor. The passenger would detach the car in an attempt to hit a foam rubber faux Mars via a tangential path. Hit = Victory! Miss = certain death.

Conservation of Angular Momentum - Using the same tether system mentioned above, the passenger would crank in the cable with a hand winch. Think ice-skater spinning and pulling in their arms. Great branding opportunity on the air-sickness bags.

I have some more images of the car and its control system. I'll add them to the post when I run across them.

Giant Engine at Detroit Science Center

For some disturbing detail images from my ground-up rebuild, visit my album.

Wednesday, May 14, 2008

Highlights from the Centennial exhibit at the Sam Noble Museum Oklahoma Museum of Natural History

Elasmosaur - Casework undulates to mimic animal's posture while providing multiple viewing levels for a variety of audiences. Mural by Debbie Kaspari. (I will do another post on the process involved in the production of the life-sized mural.)

Miocene camel: Leg bones are mounted directly over life-size mural by Debbi Kaspari.

Fossil of largest crinoid stem found in the state. Mounted directly over mural by Debbie Kaspari.