GSpeed Roll Cage Kit Development

[GSpeed]

Ever since we bought our BRZ last June, we've been planning on making roll cage kits for mass production. We'd like to start the discussion with this community to ensure everyone is aware of what we're designing, and why.

As a matter of company policy, we don't do "cheap." We always strive to provide a great value, but we also provide the best quality we can. This will not be the cheapest option out there. (There's always Autopower to take those honors.) At the same time, we recognize the price must be low enough for it to be a viable option for the weekend racer. We realize the "typical" 86 owner and racing enthusiast is not a professional team. This mindset will drive several decisions through this design process.

At present time, here's the current state of the design:



Obviously not complete, and this post will be updated as the design progresses.

Goal- Mass produced, affordable, quality roll cage kits for BRZ/FR-S/GT86 legal for SCCA and NASA competition.
Material- 1.75" x 0.095" DOM Mild Steel

It will be manufactured by extremely repeatable processes, including CNC bending and laser coping. The goal is to make this the easiest, fastest cage to install on the market.

In order to keep costs down, we will be offering a "base" 6-point cage design similar to what's shown above as a starting point. From there, customers will be able to add things like NASCAR door bars, firewall bars, etc.

A few options we're considering:

-Removable (bolt-in) knee bar for HVAC access after the cage has been installed.
-NASCAR door bars
-Chassis tie-in plates for series that don't limit the cage to 8 points
-Integrated electric power steering mounts

As we finalize the design and get production quotes, we'll have some more information on pricing. Speculation is not unwelcome, however.

[philooo]

Originally Posted by GSpeed

A few options we're considering:

-Removable (bolt-in) knee bar for HVAC access after the cage has been installed.
-NASCAR door bars
-Chassis tie-in plates for series that don't limit the cage to 8 points
-Integrated electric power steering mounts

yummi ! These options are really spot on.

I really like the idea of having mounting point for the power steering. Even though removing the dash bar would make the dash installation impossible and make the car interior fugly

I think the big difference with this product is the 3D Engineering.

One thing I am curious is how you will be mounting the Fuse box and power steering box. Because once you put the cage, you don't have any good clean place to mount these. I ended up zip tie mine to death. It works but not ideal.
I think there is also an ECU box on the passenger side that I had a hard time to secure.

[kanundrum]

Subbed!

[mrk1]

Cool, your calling it a kit, does that mean someone can order the pieces or whats the plan?

[GSpeed]

Originally Posted by philooo

yummi ! These options are really spot on.

I really like the idea of having mounting point for the power steering. Even though removing the dash bar would make the dash installation impossible and make the car interior fugly

I think the big difference with this product is the 3D Engineering.

One thing I am curious is how you will be mounting the Fuse box and power steering box. Because once you put the cage, you don't have any good clean place to mount these. I ended up zip tie mine to death. It works but not ideal.
I think there is also an ECU box on the passenger side that I had a hard time to secure.

Current plan is to mount those to the dash bar with laser cut brackets.

Originally Posted by mrk1

Cool, your calling it a kit, does that mean someone can order the pieces or whats the plan?

The plan is to sell complete kits. If you want to shoot me a message directly I'd be happy to discuss specifics with you. I've seen your work before, and I'd love to hear your thoughts.

[redlined600]

Are you still intending on offer a half cage (roll-bar) as an option?

[kster1]

Are there any plans to build a 4 point roll bar? (which sits behind the front seats)

EDIT: just saw the same question posted simultaneously by @redlined600

[GSpeed]

Originally Posted by redlined600

Are you still intending on offer a half cage (roll-bar) as an option?

Originally Posted by kster1

Are there any plans to build a 4 point roll bar? (which sits behind the front seats)

EDIT: just saw the same question posted simultaneously by @redlined600

Yes, we plan to offer one eventually. Right now, though, we've got more customers interested in fully caging their car so that's first on the list. "Our" BRZ in our build thread is actually a customer car (long story), and that customer wants to go racing. So he gets to make most of the "big picture" decisions in that regard. Does that make sense?

[OkieSnuffBox]

I think a reasonably priced, bolt-in 4 pt (in double shear mounting), is the best bet.

Regardless of how spot on the kits are, a local assembler will still need to make adjustments to notching, plinth boxes, etc, so I don't see it saving that much money.

I know some will say here what they think a cage should cost, but you can buy a NASA/SCCA/FIA custom built cage for less than $3k in nearly every part of the country.

[GSpeed]

Originally Posted by OkieSnuffBox

I think a reasonably priced, bolt-in 4 pt (in double shear mounting), is the best bet.

Regardless of how spot on the kits are, a local assembler will still need to make adjustments to notching, plinth boxes, etc, so I don't see it saving that much money.

I know some will say here what they think a cage should cost, but you can buy a NASA/SCCA/FIA custom built cage for less than $3k in nearly every part of the country.

Don't worry, we're still planning on making bolt-in cages. Not going to lie, though, people will expect prices to be much cheaper than it'll wind up costing us. It happens in every corner of this industry, everyone wants parts that say, "Made in USA!" but they don't want to pay what it costs to make quality parts in low enough quantities to fill these niche markets. This (tracking 86/FRS/BRZs) is definitely a niche market.

[ka-t_240]

What would your estimated pricing be on a bolt in 4 point option? Im one who ussually swaps cars back to stock before selling, so a welded in cage isn't in my thoughts at the moment. I'm budgeting for a roll bar, seat, harness, and hans atm.




I've looked at some, and i don't feel they are worth even looking at further. lol(autopower)

[GSpeed]

Alright, let's do some analysis here. First off, let's get one big thing out of the way.

This is not a quantitative stiffness analysis.

We do not know enough about the torsional behavior of the vehicle to get a hard, reliable number for the torsional loads a vehicle experiences on track. So we're going to pick a reasonable number, and hold it constant through multiple tests and see how the results compare.

What this means is the numbers do not match up to the real world. They are only useful for comparing between tests.

First off, we'll apply 1000 ft-lbs to the rear four mounting points of the cage. These loads are evenly distributed between the points, but the points are not constrained to each other. They can move around naturally.

The front two mounting points will be fixed. We will measure displacement of the lower left roll cage mounting plate, and use that to calculate an angular deflection, which we can use to compare different configurations.



The first test is a simple 6-point cage with a crossed main hoop brace, a double crossed main hoop, and full length harness bar. This is the lightest, simplest cage design, and will be the starting point for this study.

Deflection- 2.49°
Stiffness- 402 lb-ft/deg
Weight- 99.5 lbs

Next, let's add FIA style door bars:



Wow. Okay, door bars really help torsional stiffness across the car.

Deflection- 0.47°
Stiffness- 2146.6 lb-ft/deg
Weight- 125.6 lbs

That's an improvement of over 400%. So we're definitely adding door bars. Now, let's add some beams between the bottom of the rear hoop and the rear shock mounts. These types of bars are common on flexy unibody cars.



Deflection- 0.43°
Stiffness- 2321.9 lb-ft/deg
Weight- 134.05

So for an additional 8.5 lbs we pick up another 8% stiffness. Not bad.

Many series allow two additional chassis points on the firewall to protect the driver's compartment from wheel intrusion in accidents. Let's add those and see how much stiffness they add.



Deflection- 0.36°
Stiffness- 2758.1 lb-ft/deg
Weight- 135.52 lbs

An extra 1.5 lbs (neglecting landing plates, of course), and we gain another 18%. Pretty good for the negligible weight, and considering they're really there for safety.

Now, what about the different between FIA bars and NASCAR bars? Everyone knows NASCAR bars are better at protecting the driver in broadside impacts since they arc out away from the driver, but how do they affect torsional stiffness?



Deflection- 0.30°
Stiffness- 3297.7lb-ft/deg
Weight- 145.02

So they weigh an extra ten pounds more than FIA bars, but they add almost 20% more torsional stiffness! Sounds like a good deal.

This sort of iterative analysis is a bit of insight into how we design. Torsional stiffness is just one of many things to consider when designing a cage, but you can see here why certain things are the way they are.

Jake

[GSpeed]

Originally Posted by ka-t_240

What would your estimated pricing be on a bolt in 4 point option? Im one who ussually swaps cars back to stock before selling, so a welded in cage isn't in my thoughts at the moment. I'm budgeting for a roll bar, seat, harness, and hans atm.




I've looked at some, and i don't feel they are worth even looking at further. lol(autopower)

I know this isn't an answer you want to hear, but I really can't speculate yet. I'd have to get a better idea of what it's going to cost us and how complicated it will be to make. We'll be posting up here with what we're looking at before we commit, and might do a Group Buy.

Jake

[VerusEric]

Originally Posted by GSpeed

Alright, let's do some analysis here. First off, let's get one big thing out of the way.

This is not a quantitative stiffness analysis.

We do not know enough about the torsional behavior of the vehicle to get a hard, reliable number for the torsional loads a vehicle experiences on track. So we're going to pick a reasonable number, and hold it constant through multiple tests and see how the results compare.

What this means is the numbers do not match up to the real world. They are only useful for comparing between tests.

This sort of iterative analysis is a bit of insight into how we design. Torsional stiffness is just one of many things to consider when designing a cage, but you can see here why certain things are the way they are.

Jake

Phenomenal description of computer generated testing performed and how it can relate to real world results. Thanks for sharing Jake.