Redesign Notes - Summer 2024

Motor Assembly (Dynamics)

Issue: Motor upright is intersecting with wires protruding from the motor.

Option 1 - Create a spacer for the circular pocket with a thickness that will allow upright to rise just above the wires. Either create new mount and offset the mount by the thickness of the spacer or shave off the amount on current spacer (need to sim)

Pros: preserves rigidity of the upright body
Cons: increases the lever arm of the M8 bolts

Option 2 - Mill a circular groove for the wires to fit under. Everything else remains unchanged

Pros: Simple solution
Cons: More difficult to manufacture, will create stress concentration

Decision: Option 1

Dependencies: None

Next Steps:

Simulate upright with offset mount and with a mount that has a step shaved down
CAD a design for the spacer and evaluate manufacturing options
Manufacture spacer
Modify caliper mount (waterjet a new mount if needed)
Increase size of motor mounting holes

Steering (Dynamics)

Issue: With the current design, the top u joint is forced to have too great of an angle. Also, both u joints assume different angles, which reduces the power transmission from the steering wheel to the rack.

Option 1 - Use a double u joint to increase the allowable angle and help achieve the desired angle. Need a support to constrain the steering column from moving

Pros: simplest solution
Cons: Need extra support which will need additional mounting tabs on frame

Option 2 - Move the steering rack to the top of the frame and angle the rack to match the angle of the steering wheel. Need to create new steering arm on the upright

Pros: increase legroom for driver (makes egress easier), eliminates need for joints and gears
Cons: alters steering geometry by increasing bump steer, necessitates new steering arm to protrude above and to the side of upright

Option 3 - Use a 120 degree bevel gear enclosed in a gearbox which is mounted to the frame. Depending on bevel gear position, one or two u joints can be used

Pros: reduces angle needed for both u joints/eliminates need for two u joints
Cons: bevel gear can be tricky to keep meshing, bevel gear with correct dimensions may be difficult to obtain

Decision:

Dependencies: Pedal box location

Notes:

Steering rack NEEDS to be extended to reduce the length of the tie rods
How are we going to positively lock the steering extender (since the rack has a blind hole)
Bolt the clevis into the steering extender (need to safety wire the bolt onto the clevis) and have the adjustable tie rod with heim joints and jam nuts at both ends
Include linear bearings mounted to the frame tubes for support at both ends and implement steering stop at ends of the extenders (as a step in the shaft) to make contact with linear bearing housings at full turn

Next Steps:

Pedal Box (Ergo)

Issue: Current position of box is too far for the driver to reach, pedals are too close together, no adjustability for different driver sizes, current mounting plan (to belly pan) is not structurally rigid enough, material of belly pan (steel) is too heavy and not needed

Brake Balance (Ergo)

Issue (#120 from VDR): Prove that your rear brakes won't lock up before the front brakes. So according to the text the front and rear uses the same calipers and master cylinders (motor brake disk differs from rear brake disk). So to calculate if the front or rear will lock up first I'd like to know what the weight distribution is and the relative rotor size between the front and rear. At what force on the brake pedal will you achieve 4.72 m/s^2 of deceleration, which is the average deceleration required to pass dynamics?

Solution: For the breaks for 120 you can bias using the balance bar to have more go to the front first (that is why in 121 they are asking about lateral loading and ensuring there is a pivot. https://www.buybrakes.com/help/what-is-brake-bias/#:~:text=Brake%20bias%2C%20or%20brake%20balance,70%2D80%25%20brake%20bias. is a link to a document kinda going over it. For the rear, make sure you are keeping in account the fact that you have two different size rotors. Like cezar has said we can add left right bias using some proportioning valves. Also in case you didn't know our Weight distribution estimate is 61.86% towards the back of our wheelbase last i checked it