Body Team

• What paint do you use to paint the car?
• How did you guys go about designing your shell to shell attachment mechanism?
  • In general, something quick to attach/detatch
  • leaving small gaps - enough to tape over
• Any insight on how to do large-format resin infusion? Do you do yours in house?
  • Own layups using prepreg
    • Prepreg hard to source
  • Kentucky may use wet layups for the whole shell
• How do you attach your bulkheads to your car?
  • MIT has no bulkheads
• what mold release do you use?
  • frekote
  • peel ply
  • foam → fiberglass tooling → frekote, shell
• Array Attachment
  • VHB Tape between array and composite shell

Dynamics

• Frame
  • How do you simulate your frame?
  • Solid bodies/Shells?
    • If solids, do you use beams to establish displacement BCs or do you just simulate with load cases
  • Experience doing a space frame or is all frame sim on composites?
• Suspension
  
  • How do you train your members to have a good knowledge and intuition of kinematics, especially freshmen who haven't taken dynamics yet
    • 1st month is just developing skills
    • Statics FBD,CAD, Assembly, FEA,
    • New members get a subteam project
    • Brakes makes a calculation spreadsheet off of a FBD
    • Lot of shadowing upperclassmen
    • Freshmen usually don't design anything on their own
    • Take in a lot of sophomores
    • No rigid curriculum
    • If there are less upperclassmen, focus more on education
    • Recruiting
      • Open to anyone who's interested in joining
      • let people self select
      • no goal/application
  • what resources do yall use to better understand susp technical concepts
• UNSPRUNG MASS
  
  • How do you design parts that can withstand fatigue? Hand calcs? FEA? Want to design for ASC not just FSGP
    • FEA internal SF higher than regs
    • Instron testing of all welds/composites
    • Spare parts
    • Precedent on old parts
    • No specific calculations
  • Do you use topology optimization for lightning or do you do it by hand/trial and error?
    • Only brake rotors
    • Start with base design, run FEA
    • Would rather have testing time rather than design optimization
  • Do you use the Mitsuba motor? What do you aim for in your tires
    • what tires do you use?
      • Bridgestone
      • Source first since they take a while
      • 200kg with 
  • Do you use 2 motors
    • Direct drive 
    • 2 on Gemini (MOV)
    • 1 on their (SOV)
• Steering
  
  • How do you control toe on your rear wheels?
    • double wishbone on front
    • modified L arm on the back
• What is your upper level design process/design philosophy? 
  • Start by deciding steering system that you want to use
  • noralyl will compartmentalize and then ensure that each part of the system integrates onto the upright
  • look for where steering can best attach to the upright first 
  • steering angle chosen early on
• Nimbus
  • acrmin but not
• Gemini
  • achermin full on
• Make sure things are overconstarining your system and then making sure that the system no break
• what kind of testing/validation do yall do?
  • To what level do you model and characterize your car?
    • What components do you characterize(ie. shock absorber characteristics)
  • what data do you collect from onboard sensors
  • how do yall set up ur tests,
  • what are the inputs/outputs
    • Speed of Car
    • Temp of battery
    • TMPS
    • Lux measurement
    • (no IMUs just talked about it)
  • what have u learned abt how to do a test correctly/efficiently?
  • how do u calculate uncertainty in the sensors (if at all)
    • Senor uncertainty isn't really kept into account
    • good enough sensors should be close enough that you probably arent worried about it propagating out
  • How do you decide what data should be sent over telemetry during/after driving?
    • Strat team will take input from the car telemetry and a scout car that takes info at the front and then they spit out target range of speed and then stick to it
  • How do you choose what sensors to use?
    • Hall for battery 40A onboard (on PCB)
  • What is your transmission range?
    • Range for transmission
  • How did you decide on the placement of the radios/antennae (if applicable)?
    • Do you do any analysis to predict the amount of noise generated by different arrangements?
  • How do you store your telemetry data?
  • How is the data incorporated into your workflow?

Power Generation 

• Do you use commercial MPPTs, if so which ones?
  • Port in from 170v mppt 3 of them
    • Battery 115V
    • Old car used drive tech MPPTs but they don't produce them anymore
  • https://www.tpee.nl/home/products/
• Which solar cells do you use, do you manufacture the panels in-house or buy them completed?
  • Buy maxeon gen3 & gen7
    • Direct contact with maxeon Elizabeth Chong 
    • Start early
    • gen7s are only for solar cars?
    • have to get them approved by fsgp/asc, not yet on the approved list but hasn't updated since 2021
  • encapsulated outsourced
  • SunCat  
    • Didn't use this year due to time one and coms issue
  • Mito Solar( Netherlands)
    • Known for doing wsc teams solar cells
    • super cool
  • module layout 9 5x4, 8 4x4, 14 individual
    • In series, bypass diode every 4 cells
• How do you mount your modules/array to the top shell?
  • Shell attachment process
    • Layout with tape
    • vhb tape on back surface of modules
    • epoxy edges
  • Prevent shorting to the shell
    • silicone to plug holes around wires
    • good pete coating
    • Plastic on the back, capton tape to insulate from shell
  • Paint
    • Outsourced - can check for us
      • weather resistant
• Do you have a Power Generation team? And if so, what is the scope of their work?
  • don't think so, array/battery team
• From Matthew: (Only if MIT makes them in house)
  • What's your typical PPE and SOP for working with the array & HV electronics

  • If you're making your own converters, which topology? Llc resonant converters? What simulation work do you do? Any thoughts on adding an inverter stage and charging the car through a wall outlet

  • Does MIT faculty and admin aid the org (IE with facilities/labs etc) 
  • What is target mppt power density and cost?
  • How do you feel about pcb magnetics (inductors, transformers)

  • How do you feel about high voltage clearance and creepage

  • Anderson power poles or xt60s

  • Mcu family of choice? What rtos if any? How developed is your sw stack?
  • What is passive power consumption of the MPPT?
  • Is mppt running off power from array or vehicle bus (12v, 48v)
  • High voltage low current or high current low voltage?
    Are you madlads and just go ac with string inverters instead of mppts

  • Anyone ever find that Tesla 48v wire harness guide? Cause I'm at Tesla and I can't lmao

Notes

• Composites with Instron testing

• Find internal resistance of battery, finds power output. does CFD, cutouts are on the side near the wheel wells
• Battery box is made out of 2 layers of kevlar and then foam core, this time using nomex core
• Putting it together they epoxy the panels together, do a wet layup
• MPPTs they are housing in acrylic or polycarb

Next Gen

Body

• How do you attach the array to the shell of the car?

Dynamics

• Frame
  • thoughts on a 3-layer space frame or a space frame catamaran?
• Suspension
  • What software do you use to design the suspension geometry? VSUSP? Lotus? Own kinematics software/calculator?
  • What suspension properties do you optimize for? (how would u if ZERO prevdata) what were the main design factors? (i think spring rates, roll, pitch, bump str, hardpoint sensitivity, CG bias)
    • IMPORTANT what weights did yall end up assigning to each major factor and can u give a quick rundown of why
  • what is the very first thing u did when u began design? what is the second thing u did?
    ^ again but if u didn't have a previous car to work off of (zero data) 
  • how did u do top op? (what tool, is it straightforward or anything gotta watch out for) 
  • did yall use lapsim? if so what inputs/outputs did u use? 
  • What did u use besides spring/damper rate & tire compliance to calculate effective spring rate?
  • how did u do the math on most of these things? Make ur own excel calculators?
• Unsprung
  • How do you go about preventing uprights from being excessively large? How do you decide the shape of your uprights?
  • Do you use metal 3D printing?
• Steering
  • How do you approach steering optimization?
    • Do you have a program that calculates steering metrics? what metrics go in and out?
    • Do you take tire slip angle into account for the optimization? if so, where do you get your tire performance data?
  • How closely does your steering team work with suspension to handle things like steering wheel torque as a relationship between scrub radius/mechanical advantage of steering wheel?
  • How do you decide lock to lock steering wheel angle?
  • have you ever experimented with alternate steering designs(not a tierod based 3 bar mechanism)

Electro-Mechanical

• How do you assemble your battery box to keep it electrically issolated?
• Do you cool your batter box? If so how did you go about calculating the necessary air flow?
  • hand calcs, see Jacob Yan message i cooling
• How do you split up all of your electrical enclosures within your car? Like do you have an enclosure of high voltage lines and low voltage lines?
  • most PCBs uncovered
• What materials do you use to make your battery box and other enclosures?
  • Same as us

Ergo

• How do you calculate/verify that your brakes can actually stop the car?
• What do you do, if anything to keep the driver cool?
• what specific materials did you make the pedal box out of (pedal base, any mounting points/holes, arms)?

Data Acq

• Data to collect
  • State of charge
  • Speed
  • Battery Temperature
• TPMS
• Uncertainty?
  • Know uncertainty/characteristics from experince with he sensor
  • Excercise human judgement 
• Data to share real time
  • not sure but can ask their data acq
• Also collect data from a scout car
• How to choose sensors
  • Battery - hald()halt? sensors
    • on pcb/off pcb
• sometimes an issue to get data to the pits at FSGP, have a large antenna, can find range
• antenna by driver so signal escapes out of windshield

Powergen