Overview

The purpose of this page is to serve as a exploratory look at the advantages, disadvantages (or performance penalties) and overall purpose for a roof / solar array tilting system.

Some of the content here will be directly related from research and preliminary work done for a roof tilting mechanism on MS 14.

Purpose

It is known that solar panels are most effective at producing electrical energy when they are perpendicular to the incoming sunlight. As the sun moves over the course of the day, this means that in order to retain maximum efficiency, a solar panel would have to tilt as well to ensure it is always perpendicular to the incoming sunlight.

This is increase in effectiveness allows for batteries to be charged up closer to their maximum capacity and so extends the range of solar cars. As such, roof tilting mechanisms have been implemented on both “Challenger” and “Cruiser” Class solar vehicles.

Below are images of both a “Challenger” and “Cruiser” Class solar car with their roof tilting system engaged.

Open

Open

Advantages

The main benefits to including such a system are listed below:

• Increased energy production from solar array

  • They are operating in their most (or close to) effective state

• Simultaneously acts as a method to open panels

  • Allowing for ease of access to interior components (e.g. suspension, chassis etc.)

Disadvantages (Performance Penalties)

The main disadvantages are listed below:

• Tilting system will add additional weight to the vehicle

• Will add complexity

  • Must ensure the panel tilts properly (i.e. does not interfere with other panels when opening / closing)

  • Must ensure the tilting mechanism is designed to withstand loading due to wind forces

• Increases cost

• May impose design constraints to chassis / aerobody

  • This will be elaborated down below

• Power wiring / cable must have additional slack to account for roof tilting

System Architecture

Below will be a quick outline of different components required for such a system as well as designs other teams have used for each of these components.

The components are listed below:

• Tilting Mechanism / Hinge

  • This is the actual component that allows for the panel to tilt (but does not necessarily support it)

• Prop

  • This is the component that supports the panel and ensures it is fixed at the desired angle

• Prop to Roof Mount

  • Connects the Prop to the Roof

• Prop to Chassis Mount

  • Connects the Prop to the Chassis

Tilting Mechanism / Hinge

Below is a list of designs that could fulfill the purpose of the tilting mechanism:

• Four Bar Linkage

  • It seems that the overwhelmingly majority of solar car teams use this as their tilting mechanism

    • This is not to say we must use this design - but more of a fact that it can serve as a “tried and true” design we can fall back on if needed

  • Video showing a four bar linkage in motion: Four Bar Linkage Roof Hinge.wmv

• “Multi-Point” Hinge

  • Believe this type of hinge is sometimes on the trunk of common vehicles

    • Video: Multi-Point Hinge

Prop

The prop can fall under one of the two options:

• Fixed Length

• Variable Length

Fixed Length

If a fixed length prop is used, it must physically move (i.e. at the minimum translate along an axis) to allow for the panel to tilt at varying angles (as opposed to being constrained to a single angle)

University of Michigan’s solar car seemed to have something similar to a Linear Rail with holes (likely to interface with some sort of peg to lock in place) that their fixed length prop would then slide along. Depending on where the rod is on the linear rail the roof will either tilt more (closer to vertical) or less

Image below:

Variable Length

If a variable length prop is used then the prop can be mounted in one location and then its length can be altered to achieve the desired tilt angle of the roof.

Below are three different methods to achieve a variable length prop:

• “Snap Lock”

  • When snap lock is engaged outer rod is clamped onto inner rod

    • Force of friction prevents the two from sliding

• Spring Loaded Pin

• Internal Cam Mechanism

  • Cam is connected to lower rod - rotation of lower rod causes corresponding rotation of cam

    • Once rotated cam then pushes out on plastic / metal halves that press against inner walls of upper rod

      • Force of friction then prevents rods from sliding

Mounts

Below are some designs for mounts to attach the prop to the roof and chassis

Prop to Roof

Bracket Adhered onto Panel

This can be seen in the image below (will have to zoom in though)

The bracket itself may be a basic “L Bracket” or another type of bracket - and likewise to attach the bracket to the prop a nut and bolt can be used. That being said further concepting should be done to explore these specifics

Bracket attached to Chassis / Bulkhead

This can be seen in image below (again, will have to zoom in though)

Further concepting / research should be done to determine specifics

Considerations for MS 15

Feasibility / Value

We should look into whether or not implementing such a system is worth it both in terms of performance as well as feasibility.

While it will bring performance benefits it also has the aforementioned drawbacks - that being said given its widespread adoption among solar car teams it is safe to say that its performance benefits outweigh these drawbacks.

What should be discussed then is the value of these performance benefits in comparison to the added cost, complexity and time needed to design, manufacture and implement this system. This is a meeting that may require members of the chassis / aerobody sub-teams.

Design Constraints

If it is decided to include this system the following should be implemented to ensure the system can be integrated successfully into the vehicle

• Accommodating mounting points for the prop, tilting mechanism on the chassis

  • Could be on bulkheads or on chassis tubes themselves

• If something similar to a four bar linkage is used there will evidently be more than one attached to the tilting panel (to ensure stability)

  • These four bar linkages must be on the same level (i.e. same height from the ground) to allow for proper operation

    • I couldn’t find any source explicitly stating this but it comes from:

      • SolidWorks Motion Studies conducted (for MS 14) that showed this could only work when they were on the same level

      • Visual observation of all teams that incorporate a four bar linkage mechanism have them on the same level

    • This will impose a constraint onto the chassis / aerobody sub-teams