• Overall Concept Selected: Add on Roof Prop System

Main Reasons:

1. Weight

2. Size / Volume

3. Loading Conditions

Overview

As the Hinge-less Roof Prop System would be mounted onto the B Panel Bulkhead, the prop itself would need to be quite long to:

• Reach the roof panel itself

• Be long enough to angle the roof to the desired position

This would lead to an increase in both weight as well as overall size / volume.

With regards to the size / volume, it would also be taking up a significant amount of space within the interior of the car. Given that the interior space of the car was already tight, this would only make matters worse

Finally, while the “hinge replacement” roof prop in the Hinge-less Roof Prop System would undergo compression (which most materials are fairly strong in), the other one would be undergoing bending as well. Due to their very long and thin nature of the rods, this may require rods made of high(er) strength materials which may drive up costs and/or weight

Selected Components of Add-on Roof Prop System

This section will now cover which components of the system architecture for the Add-on Roof Prop System were chosen.

Hinge Mounting: Supplementary Panel and Direct Attachment

For the rear hinge (behind the C Panel Bulkhead) the direct attachment method was the most straight forward, with little to no additional hardware required. This would reduce both manufacturing time and cost.

For the front hinge (behind the B Panel Bulkhead) the supplementary panel was chosen as it achieves the same functionality (providing a mounting area for hinges) as the Weld Tab while retaining more flexibility in how it is mounted (can be adhered, fastened or welded). This allows for more flexibility in the manufacturing and design process.

Roof Hinge: Four Bar Hinge

This was the simplest, smallest and most feasible hinge design option. This reduces risk, while also reducing design and manufacturing time and cost. In addition, its usage by other solar car teams is a vote of confidence that this mechanism is well suited for use as a hinge for tilting roof mechanisms.

Roof Prop: Snap Lock

Among the considered concepts this was the safest (can have multiple snap locks along the prop), most robust (if a lock fails can easily reinstall a new one as they only interact with the outside of the outer tube), and simplest. This reduces risk and is a solution that is appropriate to the rigorous nature of our application.

Prop Mounting - to Roof: Eye Bolt

Based on the concepts for Prop Mounting to the Roof, the Eye Bolt was the safest, most reliable and most feasible concept. Its straightforward construction and operation reduce risk and reduce manufacturing and design time. That being said, it isn’t as user friendly as other options since the user has to screw / unscrew the shoulder bolt but this also makes it the safest option.

Prop Mounting - to Chassis

Compressed Air Strut with Mounting Brackets

Two compressed air struts will be mounted on either side of the trunk to keep the trunk supported when it is in the open position. The potential location of these mounting brackets is highlighted by the red circles in the images below

Mounting Brackets:

As the most suitable compressed air struts (McMaster-Carr ones) have a M8 thread on their ball studs, M8 threaded nuts will be used to secure the struts to the bracket.

Note that due to the ball end, the strut and ball stud can rotate independently of one another. Therefore even though the ball stud is fixed and cannot rotate (due to the nut), the strut can still rotate about the ball end. (See picture below)

In the picture above, an L-bracket is utilized as the mounting bracket of choice. For mounting to the trunk and in configuration 3, this is appropriate as the contact area of between the bracket and the mount is relatively flat.

However, in configuration 1 and 2, as there would be no perpendicular surface for the mount to be placed on, similar designs to those discussed in the Chassis Mount of the Roof Prop will need to be used.

In addition, the side/bottom mounting area has a curvature that must be taken into account. Here the following options can be pursued:

• Manufacture the bracket such that the contact area has the same curvature as the panel

  • This will almost certainly require CNC machining and does not seem like the best allocation of time on a CNC machine

• Manufacture the bracket such that the contact area has an angled cut that approximates the curvature at the panel

  • Then use a more flexible material as an “intermediate”

    • Need to research feasibility of this