As seniors, we were faced with the decision of what we wanted to do for our capstone design class.  We were given choices ranging from research based projects like designing and creating solar energy availability software and non-point source polluting lawn mowers to design based projects like the human powered submarine and the clean snowmobile.  We all decided that we were more interested in doing a design project than a research project and really liked the idea of being able to put our ideas to the test by competing against other schools from all over the United States.  This left the clean snowmobile project.     
    Once the project was chosen, we decided to take on the task of noise, vibration and harshness.  In the past, this has been an area where we have not well at in competition.  This year however, the noise test was modified to follow an SAE standard, making it a much more reliable and repeatable test.  With this knowledge we started our research.  Once we had a copy of the standard, we were able to design our testing to mimic that of competition.  We found where on the sled the noise was the loudest and focused on those areas.  
    A couple of the areas of loud noise were from under the cowling and around the clutch.  We were able to get samples of material to test and using sound testing equipment we were able to find which materials would best suit our needs for those areas of concern.  
    Another area of a lot of noise was the track.  There was a lot of friction noise between the track and the runners and there was also some noise from track slap.  In order to fix this, we decided to add a couple more rows of idler wheels.  To find where the best places were to install the added wheels, we painted the runners and ran the sled around the yard and the inspected the runners to see where the paint had rubbed off the most.  Adding additional idler wheels would lift the track off the runners in those areas.
    After another round of testing we found that we were successful in reducing the amount of noise that was coming from the snowmobile.  Infact, we were able to reduce the noise by 8.2 decibels.     
    We placed 5th at competition, 103 points behind 1st place.  However, we were not able to finish the endurance run due to sled cooling problems.  In our week long investigation into the cooling problem, several de-modifications were made to the snowmobile slightly degrading the sled’s noise performance; however the snowmobile was able to make it through all of the events.  The clutch fan worked as designed, keeping the clutch compartment at a reasonable temperature and the modifications to the track and suspension were several of the most talked about features at the competition.  As far as the key performance events were concerned, we finished 2nd in noise only 0.3 dB louder than the leader.  We also received the award for most practical design. 
    We have enjoyed working on this project and hope that next years group is able to take over from where we left off and improve on the noise reduction even more.