GSpeed Roll Cage Kit Development
 

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:

http://gspeed.com/wp-content/gallery...zbuild0075.jpg

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. :D

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.

Subbed!

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

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

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.

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

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. :D So he gets to make most of the "big picture" decisions in that regard. Does that make sense?

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.

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)

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.

http://gspeed.com/wp-content/gallery...zbuild0076.jpg

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:

http://gspeed.com/wp-content/gallery...zbuild0077.jpg

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.

http://gspeed.com/wp-content/gallery...zbuild0078.jpg

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.

http://gspeed.com/wp-content/gallery...zbuild0079.jpg

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?

http://gspeed.com/wp-content/gallery...zbuild0080.jpg

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

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

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

Subbed. Looking to cage the car soon, and i only live an hour away.

As usual, I just love to see the iteration in the design and finally feel that more bars is bette ;)

What about NODAL POINTS :) ?

Everybody is talking about nodal point for cages. My understanding is that it is a good thing to regroup tubes into 'nodal points':

|
---
|


instead of placing tube slightly at different places:
|
-----
|

For example bars coming from the rear suspension and going on top of the main hoop should merge on the opposite side as the bar going from main hoop to the A pilar.

Did you run some analysis on what difference it make to have one meeting 'nodal point' instead of 2 meeting points, like the one you have in your design. Not sure how you call your purple dots in your rendering ?

I would say that I have seen it both ways, and I am still unclear as to what perform better.

I would assume the force would transfer better with a point with symmetrical contacts (1 purple point), but then an asymmetric design (2 purple points) could allow some more distortion in between the 2 points and prevent tube sheer. (pure speculation on my end :)

I hope I am not confusing everybody ;)

Correct. It's more structurally efficient to bring tubes together at one node, but occasionally (like we're doing) they don't meet at the same point for fitment reasons. That corner of the cage is pushed very tightly up into the roof of the car, and the A-pillar bar has to be moved outward a little bit to allow for the A-pillar bar to clear the chassis. If they were to meet at one node, the roll bar would have to be about 1.5" lower, which would also bring the A-pillar bar closer to the driver's head. Given our larger tube size, we can handle the slight shear loading put into the roll bar at that location. This is one of those things we're only able to do because we have a 3D scan of the car.

The problem with that, is for some reason the vendors in this market seem to think the same material and labor should be worth 2-3x what they are for other vehicles.

Well sure, it's a problem of quantity. There just aren't as many interested buyers for this platform. It's a problem we all have to live with, and hopefully solve. If we can continue to push this platform as a cheap way to go fast on track, more people will buy them to modify, and prices will continue to fall.

Jake

That "some reason" is called economy of scale. Prices will go down as demand increases and parts can be made in volume. Pretty standard pattern with a new platform. I own a manufacturing business and I would be hesitant to crank out a million parts for a new market, especially when the parts would rust on the shelf. GSpeed is really doing some awesome work here and seems to have the process abilities to back it up. I'm following progress for sure.

subbed..... Definitely interested.

This is an awesome thread. Cage on.

Can you get a better picture of how you are loading the cage? I thought I understood the wording, but the picture look different than what I expected.

In that last picture, the pink dotted line? That's the axis around which the torque is applied.

My graphics card is woefully underqualified for Solidworks, and I get a lot of strange glitches. One of which is Simulation's External Load indicators showing up inconsistently, incorrectly, or not at all. Functionally, it's there correctly, but it doesn't always show the visuals right.

We're in the middle of moving our server to a new host, so our pictures will be down for a little bit. Sorry for the inconvenience.

Pictures back up! Thanks for being patient through this build, we're pushing hard on the Viper GTS build right now, and should resume work on the BRZ shortly.

Here's another update on the cage build.

The jungle gym of a rear cage:

http://i.imgur.com/xKgKAon.jpg

Here's a shot of the harness bar offset, which allows for maximum seat room.

http://i.imgur.com/t7h5GL8.jpg

Door bars:

http://i.imgur.com/tmacNLo.jpg

Although we won't be keeping them, it's possible to keep the factory glass windows installed, either for regulations or preference. We'll be removing ours, and making some brackets to fix the windows in a permanent upright position for transportation and storage.

Thanks for following this build! It's a slow winter for this car, but we're planning on doing some awesome things with this car when it warms up.

:burnrubber:

Interested
 

Subscribed

I'm going to subscribe. I'm interested in a bolt in 4 point with harness bar. Can't seem to find any decent ones.

Any update on this? I am actually interested getting welded since you guys are so close by

The paint shop has been backed up, and we've been waiting in line. It's been ready since last week, but we're just waiting on them now. Hopefully it'll get painted late this week, early next week and we'll take some glamour photos.

You're welcome to come by the shop and check things out any time you'd like. We've got some other fabrication projects in process right now.

Awesome!
Cant wait to see the photos!

Your diagonal bar / harness bar is not legal for NASA.

See page 46 and 47 of the 2016.1 CCR

15.6.22 Shoulder Harness Bar
"The bar must intersect the required diagonal
bar"

Thanks for pointing that out. We've built cages like this before with no issues, and some of us have issued NASA logbooks for similar styles before. The rule book is somewhat vague exactly what constitutes "intersecting" since a two-piece harness bar that arches behind both seats would be legal. One could argue this style is actually stronger in side load against a "pinching" force in plane with the roll hoop, which is what the rule is meant to preserve.

But since that's all interpretation, we've reached out to a regional NASA official to give a final go/no-go call on this element of the design. We'll update with what we hear.

My #1 gripe with the normal NASA book, NASA Rally allows it and so does everyone else.

Update: NASA officials have reviewed the design and accompanying analysis and approved the harness bar. We're all good.

Sweet!

Is that the smallest seat you could find? My seat nearly touches the roof!!!!

Seriously though, I'm going to send you a PM regarding a cage for my car.

That's a Racetech 4119, I believe. Sitting pretty low in that picture, I think it had been moved a little bit. I know it's not rigidly mounted.

We're going to start selling some slider-oriented seat mounts here in a little bit you might find interesting if you value headroom.

I would absolutely be interested. I have the Large Sparco Ergo and I'm currently thinking I may need to remove the slider with the cage, but I really want to avoid doing that since my wife and I both compete and we're almost a foot apart in height.