• 2 BAR LINKAGE SYSTEM

  • 

    Link to a gif showing a similar system: https://gifs.com/gif/r83AgW

  • Pros:

    • Relatively simple mechanism

      • Two rods connected by an internal pin. At the end points are mounted to external pins

      • To lock the two linkages a variety of systems may be used:

Name	Image/GIF/Link to Video	Description / Notes
“Bird’s mouth” Lock	https://youtu.be/NPNMDxLSKo8?t=37	When opening, will have to raise the roof then slightly lower it to engage the “Bird’s mouth” lock When closing will have to raise the roof slightly to disengage the lock before being able to close it Machining the linkages to have the flanges needed for the lock may be difficult Welding on flanges may be a possibility But must consider strength of weld
Spring Loaded Latch		In some versions of this type of mechanism it is quite difficult to get the pin past the spring loaded latch Integrating the pin may be difficult Will have to correctly spec out / design spring loaded latch Note: A video of a similar mechanism is linked to in the “Sliding Bar Mechanism” section
Physical Latch		Integrating pin/dowel may be difficult Will need to design / spec out a latch that can withstand necessary force
ARCHIVE - Intermediate brace		To lock it in place an intermediate brace piece can sit under the internal pin connection (as shown in sketch below)

• Less mounting space required compared to other concepts

  • Only need two mounting areas for the external pin connection (one on the trunk, the other on the side panel)

• Cons:

  • Can only lock at one height

  • Will need additional components to have a supported closing of the trunk

    • i.e. in its current form you must manually close the trunk to prevent it from slamming

• SINGLE SLIDING BAR MECHANISM

  • A single bar is mounted to two external mounting pins

    • One is on the trunk

    • The other is mounted to a shaft that it can slide along or may be a pin restricted in its motion by a slide opening

      • 

      • If a pin and slide opening is used, the following mechanism could be used to lock the mechanism

        • Link: https://youtu.be/5JQkzjj_cxs?t=65 (watch until 1:34)

        • Notes:

          • In some versions of this type of mechanism it is quite difficult to get the pin past the spring loaded latch

          • This mechanism will require additional mounting space and hardware

          • Integrating the pin may be difficult

          • Will have to correctly spec out / design spring loaded latch

  • Pros:

    • Relatively simple in nature

      • Only requires shaft, single linkage and external pin mounts

    • Allows for locking at variable heights

    • Could (relatively) easily integrate a supported closing mechanism

      • At the very end of the shaft would need something to slow the velocity of the bottom mount

    • Adaptable

      • Allows for the ability to become a motorized system

      • Can just as easily work as a manual system

  • Cons:

    • Will need lots of longitudinal room for the shaft

    • May weigh more than other designs due to the shaft

• COMPRESSED AIR SUPPORT STRUT

  • Similar mechanism to conventional cars

  • Will work in a similar manner

    • Two attachment points, one on the trunk another on the side

    • When opening the piston will extend

      • At apex the compressed air supports the piston, preventing it from contracting and the trunk closing

    • When closing, the force you exert will be greater than what the compressed air within can resist

      • Causing the piston to contract and the trunk to close

  • Pros:

    • Allows for supported closing of the trunk

    • May be more lightweight compared to other solutions

  • Cons:

    • Probably will need to purchase this

      • May be hard to find one that has the exact specifications we need

      • If we get ones that are too highly overspecced, it will take a higher than normal amount of force to close the trunk

    • May be hard to integrate these factory components (which are designed for specific makes and models of production cars) into our custom car

      • Mounting may be an issue

• ARCHIVE - SCISSOR JACK MECHANISM

  • Top of scissor jack will mount to roof, bottom of scissor jack will mount to side panel

  • Will work as conventional scissor jacks do

    • Threaded bar is spun

      • Clockwise or counterclockwise spin will cause jack to raise or lower

  • Pros:

    • Can have automatic opening and closing of trunk (if a motor is used)

      • Users do not need to physically open the trunk

    • Can support the roof at a variable angle

  • Cons:

    • If a motor is used, this is another element that will draw power from the battery box

      • Also will add additional weight (on top of the scissor jack itself)

      • Will require power and control wire connections

      • Would be hard to integrate a manual operation of the scissor jack

        • Physically moving the motor’s axle may cause grinding of internal motor gears

    • If no motor is used (manual operation only) this would be physically strenuous

    • Will need longitudinal space for the threaded bar to extend into

• SINGLE SLIDING BAR MECHANISM

  • Similar to the one described for the Trunk

    • However could use the existing chassis tubes as the shaft

    • University of Michigan’s roof tilting mechanism is similar to this

      • 

        • Link: https://www.flickr.com/photos/umsolar/36503620964/

• 2 BAR LINKAGE SYSTEM

  • Similar to one described for the Trunk

    • Could have second mounting point on the existing chassis tubes

2 Bar Linkage Mechanism with “Bird’s Mouth” Lock

• Bird’s Mouth Lock system shown in research section above can be simplified down

  • Simplified version utilizes only a flange to keep the two bars from rotating (thus locking them in place and propping the trunk)

    • 

    • Above image shows an exploded view of the simplified mechanism

    • Below is a video of the theoretical motion of the system

      • NOTE: GRAVITY IS NOT SIMULATED IN THE VIDEO SHOWN - THIS MAY AFFECT THE FINAL MOTION OF THE SYSTEM

      • 2 Bar Linkage with Bird's Mouth Lock Motion (3).wmv

        • Considerations:

          • When locking (i.e. pushing down on the top linkage to engage with the flange), steps must be taken so the linkage translates diagonally down (as opposed to rotating about its mounting point) so that it properly engages the flange

          • To do so: the rotation point could be tightly secured

          • When closing, the two linkages should fold into each other, we are assuming gravity will pull the bottom linkage down and thus provide this motion but this is an assumption

Compressed Air Support Strut

• Considerations

  • Generally support struts are used in pairs

    • This will result in even distribution of force (as both sides of whatever item is being supported are receiving the force exerted by the support struts)

  • When the trunk is in the open position, the compressed air struts will be exerting a force greater than the force from the mass of the trunk

    • Must consider if this will potentially damage solar cells

      • We know pressure should not be exerted onto the solar cells from the top - but could pressure from the bottom be an issue?

• Preliminary Motion Analysis

  • Conducted using McMaster-Carr gas strut (12.2” extended length, 8.26” compressed length), with placeholder trunk and side panels

  • Note: This initial test was done with a flat trunk panel placeholder, the actual trunk panel is not flat

  • Early results:

    • Gas struts can be mounted within our vehicle architecture and still produce desired results

      • Compressed Air Strut Motion.wmv

        • Note: The compressed air strut should be PARALLEL to the trunk in the closed position. This should be done so that when the trunk is unlocked it does not immediately open (because force of the strut will be acting parallel to the trunk)

          • This will avoid any potential accidents where the trunk is unlocked while there is an obstruction above the trunk and hits it while opening - which would result in serious damage to the solar cells

• Unconventional Mounting (if needed)

  • If the the mounting point of the trunk is not in line with the rotation point of the trunk (unlike how it is in the test above) the strut must be slightly extended when the trunk is closed

    • This will allow for the necessary slight compression of the strut when the trunk first opens up

    • 

      • The circle represents the path of the mounting point. When the trunk first opens up, it will travel up and away from the pivot point, thus requiring the strut to compress

      • Also note how the strut is slightly extended when the trunk is in its closed position (as described previously)

The Google Doc linked below contains all the following content for this section. This was done as doing it within Confluence’s built-in word processing was getting messy and unorganized.

• Selected concept based on further research and feasibility analysis: Compressed air struts

Main reasons:

1. Ease of use

2. Ease of implementation

3. Manufacturing time

Ease of Use (1)

Ease of Implementation (2)

Manufacturing Time (3)

• 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

• Configuration 3 for the Trunk Prop was chosen due to its manufacturability and ease of assembly

Important to note is that due to design changes to the chassis, chassis tubes extending to the trunk area were included and these will be used as a mounting area for the brackets

Regular L brackets can be used in the mounting of the compressed air strut as Configuration 3 was chosen