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 Process= Starting with preliminary ideas considered, the selection process and considerations, and then leading on to the final design.

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.

=Validation Plan= The focus of this design was to improve efficiency of the overall snow machine with this project trying to achieve this goal threw the implementation of a rear drive system. To validate this project is a success we must first prove that fuel economy has improved, then that handling has not been sacrificed if not improved, and lastly confirming that the durability is proven to be better if not the same. To achieve those standards we will submit our system to a series of tests. Some of these tests will show differences quickly, while some can only be proved accurate after a series of repetitive and many multiples of data sets collected. It must be understood prior to starting the validation plan that this is a three part plan. Allowing failure to show early which ultimately would mean further research and development of the system can be halted. Snowmobiling is dangerous, therefore Personal Protection Equipment must be worn</li> An Experienced rider must be used to preform all tests effectively</li> Validation Overview Sheet:

SAE J2263 Coast Down
This is very simple and fast test for a the beginning verification process showing a coast distance vs time. There must be an on average change in the coast down total distance vs. time to achieve that distance during the validation tests. Otherwise there is likely to be not a significant difference in the drive train efficiency. Which as we know, was the entire focus behind this project. Now this does not necessarily show a good or bad result, but if there would be no change in time vs distance during this testing procedure then it is likely to mean no change in efficiency.
 * Measurements: Distance and Time
 * Tools: Measuring Tape, Marker Flags, Stopwatch
 * Data Collection Sheet: [[File:Validation_Spreadsheet_Coast_Down.pdf]]
 * Procedure:
 * [1] Mark a 6’ wide gate, with marker flags
 * [2] Have the snowmobile configured in a drive mode
 * [3] Have the snowmobile a distance away from the gate, accelerate to a constant speed of 30 mph, in the direction of the gate
 * [4] When reached the gate, start recording time (from 0) and coast until vehicle stops.
 * [5] End recording time at the moment the vehicle stops
 * [6] Measure distance from gate to resting position of the end of the track
 * [7] Record the values of distance and time for each run, along with notes of snow and weather conditions.
 * [8] Repeat steps 3-7, 4 more times (5 total tests per drive mode)
 * [9] Start at step 2, with the snowmobile in different drive mode, and repeat steps 3-7 until all drive modes have been tested

What does this procedure show about the design?
 *  Overall Drive Train Efficiency Comparison Metric </li>

Instantaneous Fuel Economy
The second step in the verification stage is instantaneous fuel economy testing. This gives us some early insight of the systems change in fuel economy for steady state operations. Essentially the test will have a rider going a constant pre-set speed, for a short-pre-set distance. This will then be used to check if fuel consumptions are different between the two systems. This is not to be used to assess the systems fuel economy, instantaneous fuel economy testing should only be used to justify further research into the system.
 * Measurements: Fuel Flow
 * Tools: Fuel Flow Measurement (Digital Reading)
 * Data Collection Sheet: [[File:Validation_Spreadsheet_Instantaneous_Fuel_Economy.pdf]]
 * Procedure:
 * [1] Create 2000’ straight and flat course, minimum 6 ft wide, visibly marked at the at each quarter, in the middle, and each end
 * [2] Ride snowmobile at 35 mph, into course, keeping speed consistent through course
 * [3] Start recording fuel flow measurement through course
 * [4] Average all data recorded through the run into a single numerical metric
 * [5] Turn around and go through course the opposite direction, recording as step 3
 * [6] Repeat 3 times in each configuration

What does this procedure show about the design?
 *  Steady state fuel efficiency improvements </li>

Fuel Economy Testing
The major bit of testing takes place in this step, as it is where the most useful data comes from. This means that when preforming these tests, there needs to be an experienced rider to receive accurate results. This part in turn will take a lot of time to complete, having many miles of riding logged. The tests to be ran during this stage include fuel economy runs, while also evaluating the overall durability of the system. It is important to complete this step accurately for the critical data collected here will be the bulk of the supporting evidence. Which will be then used to make all final conclusions of the validity for the system.
 * Measurements: Distance and fuel consumption
 * Tools: Gas Cans, Scale
 * Data Collection Sheet: [[File:Validation_Spreadsheet_Fuel_Economy.pdf]]
 * Procedure:
 * [1] Weigh gas cans, record weight measurements
 * [2] Fill gas cans, recording the filled weights and fluid volumes (from pump)
 * [3] Fill snowmobile gas tank to a repeatable level (such as the top of the fill spout)
 * [4] Ride snowmobile at 45 mph average (or as maintainable) for a distance (recorded by odometer) of 50 miles
 * [a] Consistency is key. Having varying speeds in different turns is alright, if the speed is consistent between runs in those sections. Recommend a second rider assisting in keeping consistency.
 * [b] Fuel economy riding is a skill. Reducing RAVE valve high position, throwing weight in corners, avoiding the brake, and reducing high rpm while riding is something that should be practiced before collecting data.
 * [5] At end of ride, stop snowmobile, turn off engine, and fill gas tank to the original level
 * [6] Record weight of gasoline required to fill tank.
 * [7] Repeat steps 4-6 as needed for data to reach convergence. Approximately 200 miles in each configuration

What does this procedure show about the design?
 *  Overall Fuel Efficiency </li>

Durability Testing
This is meant to be assessed in cohesion with the complete Fuel Economy Testing, but should not only be assessed during this stage. As it also includes a separate testing procedure that should only have some of the cumulative miles logged from fuel economy distance runs while others are logged during normal operating conditions of recreational snowmobile use. This is assessed by a red-yellow-green test meaning: broken, some damage but still ride-able, and fine/fully operational without damage. Recreational riding means powder and trail riding, with the intent to have "fun". Riding edges, hills, minor jumps, and other conditions that require the rider to operate from a standing position. Not intended to assess accurately if the rider "sends it" off a 10 [ft] jump, as this would be "extenuating" riding maneuvers, outside the average recreational rider.
 * Measurements: If it breaks or doesn’t
 * Tools: Secondary Snowmobile, Tow Rope
 * Data Collection Sheet: [[File:Validation_Spreadsheet_Durability.pdf]]
 * Procedure:
 * [1] Ride Snowmobile On/Off Trail Riding
 * [2] Regular Sled Riding cumulative 500 miles
 * [a] Going over some minor jumps 2 to 3 ft. air
 * [b] Going up side-walls of trails
 * [c] Full speed
 * [3] Failure?
 * [a] If minor failure occurs, persist riding
 * [b] If moderate failure occurs, tow back, repair, and persist riding
 * [c] If complete failure occurs, design is failed, tow back and redesign

What does this procedure show about the design?
 *  Tells us overall if our design works or doesn’t </li>

Braking
This is a simple metric, but a difficult test to repeat. There are many runs that are required for this test. All pre-assumed judgments must be thrown out as "bad data" for the final data reporting.
 * Measurements: Distance and Time
 * Tools: Measuring Tape, Marker Flags, Stopwatch
 * Data Collection Sheet: [[File:Validation_Spreadsheet_Braking.pdf]]
 * Procedure:
 * [1] Mark a 6’ wide gate, with marker flags
 * [2] Have the snowmobile configured in a drive mode
 * [3] Have the snowmobile a distance away from the gate, accelerate to a constant speed of 30 mph, in the direction of the gate
 * [4] When reached the gate, start recording time (from 0) and apply brake until vehicle stops.
 * [5] End recording time at the moment the vehicle stops
 * [6] Measure distance from gate to resting position of the end of the track
 * [7] Record the values of distance and time for each run, along with notes of snow and weather conditions.
 * [8] Repeat steps 3-7, 4 more times(5 total tests per drive mode)
 * [9] Start at step 2, with the snowmobile in different drive mode, and repeat steps 3-7 until all drive modes have been tested

What does this procedure show about the design?
 *  Overall braking perfomance when making a complete stop from a given acceleration. </li>

Acceleration
This is a difficult, skill required, repetitive test again. The value drift must be considered during data analysis. The testing surface must be prepared properly for acceleration runs. And if you have to abandon the data due to outside factors, which may occur with this test, that is completely the experienced riders judgment call.
 * Measurements: Time
 * Tools: Measuring Tape, Marker Flags, Stopwatch
 * Data Collection Sheet: [[File:Validation_Spreadsheet_Acceleration.pdf]]
 * Procedure:
 * [1] Mark two gates, 6’ wide and 500’ apart.
 * [2] Have the snowmobile configured in a drive mode
 * [3] Have the snowmobile with the front of the skis at start of one gate, and in the direction of the other.
 * [4] Start Accelerating at max throttle, and start recording time (from 0)
 * [5] Stop recording time and stop accelerating when the snowmobile reaches the second gate.
 * [6] Record the value of time for each run, along with notes of snow and weather conditions.
 * [7] Repeat steps 3-6, 4 more times (5 total tests per drive mode)
 * [8] Start at step 2, with the snowmobile in different drive mode, and repeat steps 3-7 until all drive modes have been tested

What does this procedure show about the design?
 *  Overall acceleration performance from a complete stop. </li>

=Future Recommendations= Here we give some direct team recommendations for extensive projects such as this one was:

*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> <li>Hardware should be a separate sub-assembly in cad, so that design changes are not a hassle </li> <li>Suspension is more relevant than the driveline, and that should be priority to investigate.</li>
 * More to this point:
 * <li>Do not waste time investigating drive technologies that no-one is familiar with</li>
 * <li>Perhaps start with a c-motion suspension or similar which would have more room</li>

=Team Members=

=Additional Documentation=

Final Design Report

 * Summer-Fall'19: [[File:Design_Report-SuFa.pdf]]

Meeting Minutes

 * Summer 2019: [[File:Summer19MeetingMinutes.pdf]]
 * Fall 2019:[[File:Fall19MeetingMinutes.pdf]]
 * Spring 2020:[[File:Spring20MeetingMinutes.pdf]]

Exta Info/ Worksheets
Stock Sled Parts