Eamon Kelly - Roller Coaster Design

Discovering the Thrill of Engineering Thrills

Project Experience

Project Altius - The Pneumatic Launch Tower

Posted by Eamon Kelly on March 21, 2010 at 6:51 PM

I'd like to start my blog off by explaining a little bit about the group from Ohio State that helped me boost my drive to get into the industry.  Our group is dedicated to advancing student - professional relationships in the amusement industry, with a focus on the design/engineering side of the industry.  Our goal is to help students develop skills that manufacturers look for in potential employees.  At the same time, we look to harbour interest in the sciences and engineering by travelling to local schools and teaching younger students about the thrill of learning how thrills are made.  Our first project, a pneumatic tower, was undertaken with all of these purposes in mind.  Here's an explanation of our Tower project and how it came to be what it is:




Two years ago, our group decided that we would undertake an engineering project that Dan Linden had modeled in 3Ds max.  It was to be a pneumatically-launched tower like the ones built by S&S.  The catch?  Rotating seats.  We began the project by designing the tower structure, and even built a balsa model of it to help us visualize what we were going to do.  After that, we broke into separate teams, the Base, Tower, Launch, and Cart teams.



Each team had the responsibility of designing and modeling their portion of the tower.  I took on the role of Project Manager for the Launch team, and our group was responsible for recreating (albeit in a much simpler form) the system used by companies like S&S.  In order to do so, I contacted Tim Jacoby (an engineer at S&S) and Eric Lapp (Ride Maintenence Supervisor at Cedar Point) to learn more about the system used in Power Tower at Cedar Point and how we could model it at a smaller scale.  After garnering a basic understanding of the system, we began to think about how we were going to execute our part of the tower, arguably the most difficult and unknown, yet most crucial, portion of the entire project.



The launch design changed continually as we constructed the strcutural portion of the tower.  Dan and I spent the most time building the tower, and together we figured out how best to make the system work.  Originally we had planned on using an aluminum cyclinder to hold the plunger in the center of the tower.  From the plunger wire rope would go in both directions, up to the top of the tower and down to the bottom, to a set of pulleys.  The pulleys directed the wire rope from the inside of the tower to the outside, and then back to the cart, creating a loop so that as the plunger moves, the cart moves in the opposite direction.  After researching the aluminum pipe we wanted to use, we found that the cost would be far too much for us to have the pipe hold a constant circumference throughout the cylinder.  (The machining process used to make something like that is not a cheap one, so consequently getting a part like that made is expensive)  Upon researching alternatives, we found an unsual combination: a plunger made of delyron, a low friction plastic, and acrylic pipe.  Having the pipe be clear provided us with a huge benefit: when explaining how the tower worked, as we planned to do after it was built, the plunger would be visible and thus would allow those observing to more readily understand the system.



So with our decision to go with the plasitc parts in the launch system, we began to think about how we were going to get air into the top of the cylinder, where it would need to be in order to thrust the plunger down and the cart up.  Knowing the ease of manipulating plastic, I thought about ways to create a cap for the cylinder that had an inlet hole for the air, and two small holes to allow the wire rope to slide in and out, as it would need to.  I came up with an idea to take a PVC cap and cut it in half, and then use a bolt to secure the sides of the cap to the cylinder and to prevent the cap from shooting up when the air was shot in.  At the same time, a band would help hold the cap tight to the cylinder, in order to help minimize air leaks that would reduce the thrust of the plunger and the cart. 


The next step was to figure out how to deliver the air to the tower itself.  At an engineering meeting, we went over ideas on how to best execute the delivery of air to the cylinder.  We came to the conclusion that the best way to do what we wanted to do was to have a secondary air tank at the top of the tower, so that compressed air would only have to travel a few inches instead of the fifteen feet from the compressor on the ground below.  The less distance all of the air has to move, the less time it takes and the greater the impulse, which propels the plunger and consequently the cart.  Also, to make the air movement as quick as possible, Dan decided to use a solenoid valve that would open instantaneously, again allowing the most air to move the quickest.


At this point, we assembled what we had and began preliminary tests of the cart's movement.  The big problem we ended up having was that, when tensioned with turnbuckles, the wire rope would lock up the pulleys and make any cart movement difficult.  We decided that we needed to find an alternate for the wire rope, and set out to try both fishing line and regular rope.  The fishing line proved to be too stretchy, and the inability of it to hold to a consistent length nixed it from our list of possibilities.  The regular rope proved to work pretty well, with the exception of being a little loose looking, even when tensioned.  We decided to use it, however, and were ready to begin testing the launch.


Earlier, during the design process, we had done calculations to try and figure out how much air pressure we would need to move the cart.  Our initial findings were around 5 psi, so we decided to start the testing there.  While excited that we heard the solenoid valve release the air that had been held in the secondary, that was pretty much all there was to be excited about.  The impulse was not nearly enough to move the cart up the tower, so we bumped up the pressure to 10.  There wasn't much change, so we continually increased the pressure and retested.  At 40 psi, we got the cart to go about halfway up the tower.  After a few more tests, we found that 65-70 psi was the right amount to get the cart to launch up to the top of the tower, where it would freefall back down. 


At this point, we were all thrilled.  We had spent a year and a half designing and building this model, and it was a major milestone for the group as a whole.  This tower signified the growth of our group from its infant stages.  First, this project solidified the use of 'engineering' in our group name.  Second, we proved to ourselves that we were capable of undertaking a design project entirely from scratch and with little help from those more experienced.  Third, it showed our financial sponsor, Honda, that we could reliably build a project for purposes in line with what they wanted to see, consequently building a positive relationship with them for future projects.  Fourth, we finally had something physical to display, whose primary goal was to be education of area students.  Finally, we had developed a promotional tool for our group to professionals in the industry, showing we were capable of executing a project in a similar way to those undertaken in the real industry.


As it stands now, the tower performs its primary function of launching the cart up to the top consistently.  There is still plenty of work to be done, and certain aspects of it have changed through the course of its life.  One major change came with the base of the tower.  Originally, there was going to be a concrete base that supported the tower up.  During construction, we made a temporary base that was just long pieces of steel angle out in all four directions to stabilize movement.  After making the temporary base, we found it sufficient in holding the tower steady and preferable due to its ability to be taken apart.  Consequently, the temporary base became the permanent base.  Another change occurred with the wheels that are on the cart.  Some of the guys in the group installed a sturdier and more permanent wheel system than what was there before.  Even with these changes, however, there is much to be done.  We have yet to finish the seats on the cart, and hope to be able to finish them with the original idea in tact: rotation.  Also, we would like to add asthetic theming to the ride before we take it to schools.  Hopefully we can see these changes occur later this year, when I'll be back in Columbus to help out.


Well, that's it for my synopsis of the TPEG Tower project.  Check back here for more updates on it, and also for updates on my coaster project.




Categories: TPEG - Pneumatic Tower

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Reply Nick
7:37 PM on March 22, 2010 
Hey, really nice article! Sounds like a fascinating project. Did you model the complete tower in 3D before you built it and if so what CAD software did you use?

Also, I am an administrator and writer over at Coaster101 and I think it would be really cool if we could interview you or use something along the lines of what you've written as a feature? What do you think?
Reply Eamon Kelly
9:50 PM on March 22, 2010 
Hey Nick,

Thanks for the comment! We modeled the frame of the tower, the frame of the cart, the pulley mounts and pulleys, the base, and the cylinder and plunger. Everything else was made 'on-the-fly' as we were building the structural parts. We are looking into modeling the seats so that we can rapid-prototype them through our school, so those may end up getting modeled.

Our school provided us engineers with Autodesk Inventor (which is now free for any student), so everything we did then was in it. I'm looking at doing my stuff in it too, so I can put it into 3Ds Max to try making animations.

The interview sounds like a great idea! Just shoot me an email at [email protected] and let me know what you're thinking, and we can set something up.
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