Rear Driven Snowmobile for CSC

The goal of the project is to design an effective and fully functional rear driven track for the Clean Snowmobile Challenge Team. This design is to be implemented on the snowmobile for use during the 2020 SAE Clean Snowmobile Competition.



=Problem Definition= Conventional snowmobiles have tracks that are driven from the front causing the top of the tack to be pulled in tension and the bottom of the track to be pushed in compression. The portion of the track in contact with the snow, being in compression, causes losses in efficiency and decreased handling. The clean snowmobile team anticipates to see drastic improvements in the following competition events: Acceleration, handling, and endurance.

Background
Currently, there are not any rear driven snowmobiles on the market. This is mainly due to manufacturers wanting to reduce sled weight and simplify designs. Aftermarket rear driven snowmobile prototypes have been made in the past, however, their application is mainly for drag racing snowmobiles. The past CSC projects that have attempted this type of design are detailed below.

2011-2012 This Senior Design Project was the first attempt by the UICSC team at implementing a rear drive snowmobile skid. The design this team created involved a gear and chain system that ran down the center of the tunnel. Having the chain in this configuration meant the team had to redesign the suspension, and complete a finite element analysis. Once the system was fabricated and testing could be done, the team found that their chain would brake too often/quickly; they concluded that they were lacking a chain tensioner.



2014-2015 During this school year another senior design team took a second crack at tackling the rear driven snowmobile. Following findings by the previous group, and adapting the built skid from the 2011 project they added a chain tensioner. However, due to part received delays the system was not completed not implemented on the sled for competition.

Due to a change in SAE competition rules a chain and gear system would need to be fully shielded and an oil bath and lubrication system would need to be implemented. The amount of modification and weight adage to do this leads our team to explore other avenues of research.

2015 A masters student, Matthew Kologi, looked into this design problem as a part of completing his masters degree. He performed conceptual and ideological experiments in detail to explore the theoretical efficiencies that could be gained from implementing a rear driven skid. In his analysis, he explored a drive shaft and pinion gear system. In his road load models he found that once a cruise speed is reached there is little resistance to maintain the cruise speed. Being a conceptual design exploration there isn't any information detailing how such a system would fair on snow.



Deliverables
Our team's goal is to design, fabricate, and test a rear driven snowmobile. The implementation of this system is hoped to improve competition activities where handling, fuel efficiency, and overall sled performance is necessary. The system should maintain the full functionality of a stock snowmobile. Minimal weight addition is desirable. Any designs involving the electronic transmission of power from the engine, clutch, and/or crankshaft must be submitted to the SAE competition proprietors prior to the competition for approval. Other deliverables include:

* Two people should be able to swap out stock and designed skids with relative ease. * Detailed 3D model & engineering drawing package. * Must withstand the power (120hp), torque (100ft-lbs), and track speed (100mph) of the UICSC snowmobile * In-depth Engineering Analysis for the re-designed suspension system.

Specifications

 * SAE Clean Snowmobile Challenge Requirements

Meet sound requirements for National Parks

=Design Considerations= Preliminary Designs:


 * Hydro-static power transmission implemented motorcycles
 * Pump 
 * Motor 
 * Dimensional Drawing 
 * Synchronous Belts and Pulleys
 * McMaster
 * Pulleys 
 * Belts 
 * BB Man
 * BB Man - Belt Drive Calculator 
 * AutomationDirect
 * Electronic Power Transference Components
 * Alternator 
 * Power Bank
 * Speed Controller </li>
 * Motors</li>
 * DC/Sservo </li>
 * Induction Motor </li>

=Final Design=
 * Final CAD Model Designs by Sub-Assembly:


 * Final CAD Model Designs of Driving Axle's:


 * Full Assembly: without the tunnel Displayed on our final design of the Rear Driven Snowmobile.


 * Full Assembly: with the tunnel Displayed on our final design of the Rear Driven Snowmobile.

=Manufacturing Still Needed= This is some items that will need to be finished do to the COVID-19 Pandemic, which shut the campus down preventing the team from finishing up the manufacturing.

=Future Recommendations= For future recommendations we have divide this section up by three parts. Based on our individual experiences, we each had personal recommendations for the next generation participating on this project. Then together as a team we had some larger ideas equally shared amongst the three of us for the next generation of the project. And for the third and final part, we gave some direct technical design recommendations for the hopeful continuation of this project. As there are many recommendations we will gloss over these slides and let you read the rest while discussing a few of the major points.

Personal Recommendations
Thomas Entwit: If I could do it again, I would only worry about rear drive first, forward drive second. I would recommend to take accurate measurements and follow the design guides from the OEM. ie: don’t make a 8mm bolt a 3/8” bolt for no reason. I would also hold off ordering bolts/hardware until everything is made, so that you don’t have to waste time ordering these components on geometry thats not finalized and manufactured which is likely to change in that process. I would also try a 3-D scan of stock parts you are going to use during the design stage after you order the components you know you need to modify. This creates less inaccuracies when measuring caused by human error.

Aref Hakami: I would recommend team members must know how to manufacture components, prior to taking on such a manufacturing intensive project, if they desire to do such a project like we did. This sets a domino effect if there is a huge learning curve in this critical step of manufacturing, if there isn't that prior knowledge. Many of our experienced team members took time out of manufacturing just to teach other team members how to manufacture the simpler components when that time really could have been better spent else wise. Lastly, don't, let teammates fall behind because they arrived later in the project. Often designs are pitched, but there are not enough people to do the desired project. The people that the Capstone committee assigns to the project must be brought up too speed early, I think in the design stage.

Brannon Hudson: Avoid welding things that are too much for the Mechanical Engineering shop to handle, look for alternative ways to complete this process or design around the shop constraints in equipment. Be knowledgeable of the tools, machines, welding equipment, and tooling that is available before the design decisions are made. In our project there was a lack of and there for I recommend future generations to research alot more into the understanding of the suspension before making changes to this, as well as a decent understanding of the OEM Design and its inner workings. Lastly to help with the manufacture process use real metrology tools. Calipers, micrometers, laser, 3-D scans, CMM, ferule arms, etc. DON’T USE TAPE MEASURES AS PRECISION INSTRUMENTS. Anything that goes in CAD and is important needs precision dimensions down to at least 0.01”, if not 0.001”.

Team Recommendations
For some overall, whole team composed thoughts and recommendations we have coame u with the following. Starting with a piece of advice for the immediate next group to pick this project, should it be finished, that while making their budget and when preparing for purchases, assemble quotes from 2 or 3 sources at a minimum. Wile this takes some extra time it’s it very beneficial on the team pocketbook, but when gathering these quotes, if a company, specifically we found when dealing with UI facilities, don’t even bother writing the quote down for materials or parts they don’t have in. The quote is most likely to be wrong by the time you end up purchasing. Next, we found while beneficial as it was having full teams as we made this proposal as 4 UICSC team members, which were split down the middle for expected graduation, it would have been a lot better to keep it as only sled members. Then we would have all been on the same page from the start and a lot more work, could have been completed with less explanation needed for the new members. Third, do not use Pre-made CAD. In our case we had some old designs from previous iterations of this project on the shared drive. And while that help get the first group a head start on CAD Work, it severely hurt us in the long run, down the road having multiple errors needing to be fixed during the manufacturing stage of our project. Causing more time destroyed then it saved. Next its best to stick to what you know; we had a lot of time wasted on predesign work investigating designs that were excessively out of our teams knowledge box. For instance, no one should have went down the road of hydraulic motorized systems, or electric motor systems when it wasn’t anything any one of us knew much about and we had much work still ahead of us, putting us in a bad spot for future competition goals. Leading us now to our next point, Capstone, the class, has a lot of mile steps, and so does the CSC team, it would have helped us a lot more to investigate the classes goals prior to aim to complete them closer in step with the CSC teams objectives. Last The future testing on this project we recommend is to be preformed on our 2017 Skidoo Chassis, known as “spectre”, as this is the machine we designed it for and the future of our team will be moving onto a new although probably similar, it won’t be the exact same chassis. Some additional points include: *The CAD models are never perfect. The poor metrology of the skid rails are still there from the previous team, and we still have them in our model. *Future manufacturing: use all the shop and CSC material before buying. *DON’T BUY FULL SHEETS FROM FACILITIES they will rip you off if it is not already stocked *Work together. Manage week by week, Do not stretch out deadlines. CAD is best done with everyone present. *Have an open schedule, this is a lot more work than the average capstone. It requires far more attention to detail. *Without a ‘real’ sponsor, you must be self-driven and hold yourself accountable. You will need to secure sponsorship and other funding. Be bold and be ambitious. “Ask high and ye shall receive something reasonable” *Two-part teams are dangerous. Stick to a single senior year team, if possible. Otherwise one team loses design control while the other dumps their work on to you. Especially if they do not meet the pre-assigned goals and deadlines. *Assign a team manager. If you have a 2-part team, have one manager who is there/present for all three semesters. Loss of consistency destroys productivity of large groups. *Maybe a future CSC project could be a cruise control to help for testing the rear drive.

Technical Recommendations
If there was to be a redesign: Find a way to have the front belt center to center length be the same length as the swingarm pivot length, so as huge a dynamic tensioner is not needed. </li> Find a way to machine the hubs as a solid piece, instead of welding </li> Find a way to clock the key and bolt circle angles, so that they are consistently made </li> Use commercial bearing retainer tech (like pillow blocks) </li> Hardware should be a separate sub-assembly in cad, so that design changes are not a hassle </li> Suspension is more relevant than the driveline, and that should be priority to investigate.</li> More to this point: Do not waste time investigating drive technologies that no-one is familiar with</li> Perhaps start with a c-motion suspension or similar which would have more room</li>

=Team Members=

=Additional Documentation=

Team Contract

Product Requirements Document

Project Schedule

Project Budget

Calculation Spreadsheet

Meeting Minutes





Exta Info/ Worksheets

Stock Sled Parts