C4 Corvette Roll Cage Design and Proposal

This is the first forum. We'll figure out if we want more.

Moderators: MostMint, wxo, Fred32v, Basement Paul, ttamrettus

Post Reply
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

C4 Corvette Roll Cage Design and Proposal

Post by MostMint »

Post #1:

Based on ChampCar rules and interest of safety, Mostmint Racing proposes a roll cage design for a C4 Corvette.

Contents:
Problem Statement
General Design Proposal
Main Hoop Proposal
Halo Hoop and Front Legs Proposal
Door Bars Proposal
Seat Configuration Proposal
Remaining Details Proposal
Reference Material
Timeline/Status
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Problem Statement

Post by MostMint »

Post #2:

The Vette cage is not going to fit the typical cage configuration described in ChampCar rules (2020 BCCR), and typical cage designs (approved by various sanctioning bodies) do not provide adequate structural integrity

1. The floor comes up directly behind the rear seat, meaning the main hoop cannot practically be full length
2. With a shorter main hoop, the door bars cannot be attached to the main hoop
3. With a flat seat slider (about 1”) and an aluminum seat my helmet clears the roof by less than 3/4”
4. My helmet is above the highest point attainable for the main hoop in the rear
5. The design of the car has the passenger compartment getting more narrow as it gets closer to the roof, which means my helmet is very close to the targa top frame on the left side of the helmet – putting the halo hoop will be in the same or closer proximity
6. The factory chassis uses a premium grade material in the rollover protection between and connecting the B pillars
7. The high point in the interior is directly behind the top of the windshield and the entire roof line slopes down from there
8. Typical designs attach door bars to the floor behind the driver seat which does not provide adequate side impact protection. Pre-fab kits attempt to fit the traditional main hoop on the flat floor surface behind the driver

<pic 1> picture of the Vette silhouette
Pic 1.gif
<pic 2> picture of the Vette blueprint structure
Pic 2.jpg
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

General Design Proposal

Post by MostMint »

Post #3:

General Design Proposal

1. The halo hoop is going to be above the main hoop
2. The factory rollover protection will not be cut to put the main hoop above the driver's head. It is considered an extension of the main hoop, and the main hoop will be within 1/4” of the rollover protection on the roofline. Top of drive helmet to be 7/8” below the top of the factory rollover protection
3. The halo hoop and top portion of the front legs are going to be outside of the original designed structure of the car
4. Where the door bars typically connect to the main hoop, they will instead attach to flat plates secured to subframe of the car
5. There will be one additional bar between the front center of the halo hoop and the center of the rear main hoop
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Main Hoop Proposal

Post by MostMint »

Post #4:

Plan A:

Put the hoop under the factory rollover protection – keep it within 1/4” along the top and attach the sides with gusset plates.
Cut through the fiberglass to get to the subframe and weld mounting plate to that

<pic 3> Vorshlag main hoop to roof bar
Pic 3.jpg
Plan B:

Put the hoop directly in front of the rollover protection
Cut through the floor in the subframe area just before the floor goes up behind the driver and put mounting plate there
Note: Based on our measurements this will not provide adequate clearance to the helmet, and if we do put it here the driver seat angle will have to change quite a bit so we are NOT going this route.
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Halo Hoop and Front Legs Proposal

Post by MostMint »


Post #5:


Eliminate the targa top mounting brace for helmet clearance on the left, and possibly for main hoop clearance
Mount the fiberglass top to the cage
Install an extra bar along the roofline in the center of the car from the halo hoop to the main hoop

Plan A:

Front legs of the cage will run outside the A pillar up to the halo hoop. Halo hoop will also be mounted out
Attach front legs to A pillar with gusset plates
Front legs to mount to subframe at top of rocker panel/kick plate area. Will have to cut through the fiberglass to reach the subframe
The halo hoop will be located above the rear main hoop and the bars will have a small bend to come down and attach to the main hoop

<pic 4> Vorshlag front leg pic / overhead view
Pic 4.jpg
<pic 5> example of XP Motorsport C5 with bars going up and center bar
Pic 5.jpg
Plan B:

We can move the seat over enough to the right to get adequate clearance and the halo hoop will run in the same location as the targa top frame. Note: With a 7" Kirkey style seat there is not enough room to move the seat to the right without hitting the tunnel or extensive modifications to make the seat smaller so we are NOT going this route

Note: could be alternatives here depending on the final decision of the main hoop.
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Door Bars Proposal

Post by MostMint »


Post #6:


Plan A

Typical installations I have seen attach these bars behind the driver seat on the angled floor plane, instead of the main hoop. The issue here is that the floor is thin metal and may crush in a side impact.

Our proposal is to cut open the floor in this area and attach to the subframe, which is much sturdier and should do a better job support the door bars in event of a side impact.

<pic 6> inadequate side door guard design *
Pic 6.JPG
<pic 7> pic of where the plates/side bars will attach to subframe (still need to cut floor and take this pic)

Plan B

If we can get adequate leg room we can put the seat further forward, use typical rear hoop and just attach to the rear hoop.
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Seat Configuration Proposal

Post by MostMint »

Post #7:

My tallest drivers are 39” tall with helmet in the seated position
We have large height variations we need to accommodate 5' 4” to 6' 3” so we will be using an adjustable seat
Current plan is to use an aluminum Kirkey 17” or similar and have drivers use inserts for adequate height, length, side support or comfort
We will fabricate adequate brackets to hold the seat in place and connect to the sliders

Current adapter slider configuration is just under 1.25” tall and fits on stock moorings. We plan to use stock mounting locations.
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Remaining Details Proposal

Post by MostMint »

Post #8:

1) The fifth belt mount will need to be fabricated as it appears the location where it would attach is fiberglass
2) The floor is fiberglass below from under the pedals to the front edge of the seat. I would think metal would provide better/extra protection
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Reference Material

Post by MostMint »

Post #9:

Sources of information

Robert Brown XP Motorsports – recommended by Jay Mauney ChampCar Technical Director
Mark McMahan rollcageguy.com – the guy for race car cages in NE Ohio
Vorshlag Motorsports – amazing detail writeup on a NASA legal Corvette build
Lots of time measuring and looking at the car
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Timeline/Status

Post by MostMint »

Post #10

Timeline/Status
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
Post Reply