Seattle University 2008-2009 HPVC Entry: Optimus'
During the 2008-2009 school year I had the pleasure of working with a great team of engineering classmates and friends to build a bicycle to compete in the Human Powered Vehicle Challenge. I led the team together with Adrianne Beach. Below is a picture of the team with the bike sans roll bar and saddle bags.
The members are, from left to right: Adrianne Beach, Kevin Manalo, Jessica Gunderson, Sam Simon, Peter Medina, Mike Sullivan, Dr. Frank Shih (hiding), Matt Lollini, Charlie Bourain, Me- Brian De Vitis, Adam Bornemann, Brian Kunimoto, Moussa Niang, Nick Spada, and Mark Toma. Ryan Shepard was on the team but was unable to make the trip so he is not in the picture.
To give you some background about the competition here is a link to the ASME website, HPVC. There are three main events; sprint, endurance, and utility. The sprint and endurance races are pretty self explanatory. The Utility competition is a bit different. Teams must pick up or drop off groceries on every lap to demonstrate the utility of the vehicle. Our team chose to concentrate on participating in the utility event, hence the saddle bags for the groceries in later pictures. Rules for the competition state that roll bars are necessary on all vehicles. If your team does not have a roll bar you will get docked major points.
Teams have to submit a report on their bike in advance to the competition. These reports are heavily weighted when deciding the winners of the competition. Here is a link to the report we wrote on our bike: 2009-SeattleU-HPVC-Report.pdf. It includes finite element analysis of different components, ergonomics, modeling, and much, much, more.
As team leaders Adrianne and I wanted to design something unique. Year after year it seems like the bikes all start to look the same. Sure its a learning experience for everyone, but why does it always have to be the same designs? Well, we aimed to be different. At first we thought a bike that could fold up to a very compact form would be cool, we even did a basic CAD model. Still unsatisfied and looking, the previous years team leader, Graham, suggested we design a shape shifting bike. We were pretty much sold after seeing the YouTube video of a transforming bike. We were only able to find two models online none of which were commercially available. The design was possible, very few people have done it, and so we had our idea. We were to build a shape shifting bike that would allow the user to ride in either recumbent mode or upright mode as they please.
Implementing the idea was going to be hard. The report in the link above goes through some of our thought process. At first we wanted to have something use stored power to actuate the change in the bikes geometry, after some thought we realized how impractical that would be. Everything would be too heavy and complicated. So we decided on a pair of gas springs to help change the geometry. The bike was a great success and the team went on to win 2nd in utility design and 3rd overall in utility. We placed sixth in the actual race, but after adding it to our design score we placed 3rd overall. The Human Powered Vehicle Challenge places a lot of emphasis on the report. They want to ensure that teams understand the engineering behind the bicycles they build. To get an idea of who we competed with click HERE to see some photos.
The picture below shows Sam riding the bike in recumbent mode in one of the parking lots where the competition was held. The next picture shows Sam, without having stopped from the first picture, riding in upright mode. The bike could be shifted back and forth while riding simply by shifting the riders weight. That is why we called the bike Optimus' (read Optimus Prime). More weight on the pedals would bring the rider to upright mode with assistance from the gas springs. More weight on the seat would overcome the gas springs and let the rider ride in recumbent mode.
Because our bike could transform we decided to name it Optimus' Hawkenheimer (the last name has been kept through the years). Below is a great artistic rendition of Optimus Prime riding our bike. It was drawn by our advisor and professor Dr. Frank Shih. We used it as the cover page for our report and as the design for our team shirts.
The building process was a long one. Our advisor Dr. Shih and machinist Jeff Wilhite helped the team build the bike. Without them this project would not have been possible. Of course the student team put in a lot of effort as well, and they too were very important.
Neither Adrianne nor I had much experience managing an engineering team. Figuring out how to delegate tasks and which parts to build in what order was difficult. In the end I think it went very well. I'm proud to say that this year had a very large turnout of people participating in building the bike. It would not have been the same if the team was smaller.
We ended up giving different parts of the bikes to smaller teams of students. For example, the roll bar and saddle bags were designed and built by two separate groups of students. To make sure everything would come together we established a set of constraints that the parts had to be designed to. The rest was then up to the individual group.
The next set of pictures are of some of the many different parts that we built for the bike. The picture below is of the bottom linkage for the chassis transformation mechanism. It is a hollow aluminum tube with two aluminum hinge parts welded into the ends. The aluminum ends were CNC milled from 1.5 inch square aluminum rod and are press fit into the tube and welded for a strong linkage bar.
The next picture shows one of the side plates that is centered around the main pivot point of the transformation mechanism. The hole patterns in both ends are for the bolts that keep everything together. The center part with the gear is the main rotation joint. Power from the pedals needed to be transferred through this joint while maintaining its ability to rotate with the chassis. To achieve this there are bearings press fitted into an aluminum sleeve with needle bearings on the outside of this sleeve. The sleeve is then fixed to the chassis. The gear rotates through the center of the sleeve while the chassis transforms on the outside of the sleeve. The gold colored bearing on the right is where the bottom linkage bar from above connects to this part.
This is the same part as above, but without the gear and center aluminum sleeve. This is to show you the other side of the part. The part started out as a 1/2 inch thick sheet of aluminum. Most of the area was milled down to 1/4 inch except for where the needle bearing is, that maintains the original 1/2 inch thickness.
Below is the main anchor of the bike so to speak. It is not complete in this picture but it gives you an idea of how much milling this part took. It started as one large aluminum block. The large hole on the left is where the aluminum sleeve mentioned above is mounted. The aluminum sleeve is fixed relative to this part.
The darker part below the aluminum part was the original anchor. It was made of construction grade steel and was ridiculously heavy. It was welded to the main chassis tube and the tube was accidentally buckled late one night in the work shop. It was probably for the better though, the aluminum anchor saved a ton of weight and it looked a lot better thanks to Dr. Shih's machining skills.
This is the center gear that transfers power at the aluminum sleeve. The axel is made of chromoly steel, the axel and the part with the bolt pattern are the same piece of steel. This part started out as a steel rod the same diameter as the outside diameter of the bolt pattern. It took a lot of time to make and it is very impractical but it is also a very strong and precisely built part which is what we needed.
This is the most complicated section of the bike. It is where power is transferred from the pedals to the wheels and where the bulk of the structure for the transformation capability is housed.
To get as many points on the bikes design as possible in the competition we decided we needed to build a roll bar. The roll bar was heat formed using acrylic tubing and then three layers of carbon fiber were applied for strength. The actual carbon fiber material used came pre woven into a sleeve form.
The picture below shows one layer being applied. To keep the epoxy on the carbon fiber even and smooth, electrical tape was wound around the carbon fiber as it dried. To let out any excess epoxy, holes were predrilled into the roll of tape. The holes allowed the excess epoxy to seep out where needed without making sanding difficult later. Electrical tape is also easy to peal off of dry epoxy. So once the mold was dry, unwrapping was easy.
Below is what the roll bar looked like while the epoxy was curing. It was hung from the ceiling using string and as you can see it is semi-shiny because it is wrapped in electrical tape.
This picture shows a number of the parts for the bike. The main parts to notice are the two sides for the rear wheel fork. 3/8 inch thick aluminum "L" channel was used to build the fork. we did this to increase horizontal stiffness when going through corners or taking any other horizontal forces. Eight bolts secure each side of the fork to the chassis for a very strong mounting. One more thing to notice in this picture is the original steel anchor at the middle left. The area where the beam buckled can be seen on the far left side of it.
The chassis beam, shown below, like the main anchor was also rebuilt using aluminum to save weight. The beam is in the mills vice to drill holes for the rear fork shown above. The left of the beam in this photo is where the front of the bike would be once constructed.
The next picture is of the completed bike in Seattle University's machine shop. For the competition we had to keep it locked in recumbent mode because that was the only mode where the roll bar was actually effective. If you look closely at the area right behind the pedals you will notice a bar with a couple of black parts on either end. This bar kept the bike locked in recumbent mode during the races.
For the report and to score higher in the competition we needed to force test the roll bar. This picture shows students setting up the testing apparatus. The roll bar was tested without most of the bike put together to make mounting it easier. We stacked 460 lbs of metal vertically on the roll bar to get 2 points. To get 3 points 600 lbs needed to be applied. It was a rather nerve wracking experience to bring it to 460 lbs. The acrylic tube inside the carbon fiber made very loud noises as it cracked from the large amount of the deflection.
Here is the picture showing that we got 460 lbs on the roll bar. Each plate is 20 pounds. The roll bar was designed to withstand more than six hundred pounds. However, since this was our only roll bar and we did not have material to make a second one we wanted to play it safe and so we did not go to 600 lbs.
To get more points we also had to test the side loading of the roll bar. Mounting the roll bar was harder here than it was for the vertical setup. The person sitting on the top is there to act as a counterweight to keep things from falling. Thankfully we did not have to test to anywhere near the same weight as the vertical test.
Our primary event was the utility race. It took place on the first day of races along with the sprint race. Adrianne, the other team leader was our first rider for our main race, below is a picture of her riding the bike. As an avid bicyclist, she was also one of our top riders.
During her part of the race it began to rain something serious. The picture below shows just how bad it was.
We had a lot of issues with the gear set on the rear wheel. We had forgotten to tighten it to the wheel before the race. Twice during the race it became loose and twice we had to do a ten to fifteen minute repair to fix it. This put us in second to last place during the race. Besides that the bike worked well and everyone who rode in the race did a great job of working to make up for the problem.
Probably one of the most exciting moments of the race came less than 100 yards before the finish line on our last lap. We were set to be the second to last team to finish the race, Sam was riding, and all of a sudden the bike stopped with less than 100 yards to go. The last place team was approaching and we had no chance to fix the bike in time. Thinking like a boss, Sam picked up the bike over his shoulder and finished the race Cool Running's style. And he finished just in the knick of time, the team in last place finished only seconds later.
It turns out that what stopped the bike was actually pretty serious. Basically the kickstand became loose from its mounting and turned into the spokes of the rear wheel. This caused about half of the spokes on one side of the wheel to be ripped in half. The picture of the after math is shown below. Luckily we were able to find a single rear wheel for sale at a bike shop nearby and we were able to replace it in time for the endurance race the next day.
This is a picture of Adrianne and me fixing the rear wheel that broke during the race. Most of our work was done in the hotel room out of respect for the neighbors. It would have been too noisy had we worked in the parking lot.
The next day we raced at a more leisurely pace. The endurance race is not our competition. Not because we couldn't build a competitive bike, but because the top schools that win this event have actual competitive cyclists on their teams. The picture below shows Matt riding the bike during the endurance race.
This is Charlie taking some laps in the endurance race.
This is our team photo after our utility race. We finished during a nice sunny afternoon and with lots of good memories.
As a final thought, I want to say that the bike project was one of my favorite memories of my undergraduate degree. I got to know my classmates better than ever before. Working with a team helps develop people skills and it can create a great community of friends at the same time. Our team set out to have fun first and win second. I think that that mentality really allowed us to enjoy the experience so much more.
I feel that everyone in engineering should work on a similar, if not the same, project. Lectures can only offer so much, nothing beats hands on experience and working with a team.
Copyright, Brian De Vitis, 2013 Contact Me at firstname.lastname@example.org