ErikwithAK01

It was suggested I post this here, so here it is

Like the title says, for those of you with more experience in the racing world...
-What diameter tube should I be using?*
-What wall thickness would be appropriate?*
-Should I weld in gussets common to the bolt plates at either side?*
-Any creative anti-roll modifications that can be implemented with existing hardware locations?*
-What is your suggestions for harness style/brand

Im looking to make a pretty basic bar, so will likely be using clip on harnesses for the harness bar, other than that, I am going to spend almost all my time OFF track, and under the 11.50 et for a drag race here and there, so I dont NEED anything crazy for this application, ie not 6-point harnesses. Im wondering what the best/most common parts are, specific to the C5, that make the lap and/or crotch belts mount with ease, for stock sport seats? In my research ive heard that a company makes push button clip on sub bars for harnesses, but have not seen one or know of the company. I may very well want to go back to stock with the seatbelt one day, but minor modification to panels or carpet does not concern me. Would a 4 point harness be reasonable for my application, are there products out there to supply 4 points?

Any info will be greatly appreciated*
Vette on fellow enthusiasts!

Aardwolf

I made one awhile back as a fun project. This is what I used:

http://www.aircraftspruce.com/menus/me/steel.html

03-55300 4130 SHEET 6" X 12" X .125" $8.28 end flanges
03-10800-4 4130 STEEL TUBE 2X.065 4FT $26.40

It weighs four pounds and is gas welded to federal aircraft specs.

Bill Dearborn

4 point harness will not be sufficient. The ones you see being marketed are for specific cars that have the proper belt mounts to begin with. Those types of harnesses have one shoulder belt that is designed to give before the other. This lets the body pivot forward over the lap belt similar to what a 3 point does thus preventing submarining under the lap belt. They are not designed to work in a Corvette with a harness or roll bar and if you use them they can never be installed correctly.


You need a 5 or 6 point harness. At this time 6 points are more widely accepted. The sub belts don't keep you from submarining. They are designed to counteract the pull of the shoulder belts and pull the lap belt down into its proper place across your pelvis which keeps you from submarining.


I have seen a lot of crap harness setups and mountings and they all seem to be in drag cars. Not sure what their standards are but they aren't as high as SCCA or NASA.


Bill

fatbillybob

This is what I did at home with my MIG welder. I did this when I was unsure if the Z06 was what I wanted to race. Beware building a dual use car as you propose. Often you make safety compromises that look safe but are not. The harness bar and harness anchor system pictured is untested in a crash. Does it work? Is it safe? Well not enough for me that's why I used it briefly to test the car then went all the way making my Z06 into a full gutted racecar with a full cage.

1.75" x 0.120" dom tubing
2x2"x0.120 angle iron
6 pt harness parachute style clip in pull up laps pull down shoulders

harness bar to the B piller shoulder anchors.
still have the oem shoulder belts and laps.
The bar will not rotate because of the angle of the support plates angle iron is drilled and captured by the rear seat anchors.
I figured Those bolts must be able to take the load because the lapbelt is connected to the seat.
Drill holes in the angle iron to accept the lap belts and the sub belt clip in anchors.

If you want a bit cheaper but still high quality go with simpson or schroth latch link 6pt harness instead of cam locks. Modify the Z06 seat with a pass through so the belts don't slip off your shoulders or use a sport seat with holes. If you use parachute style subs you don't need a seat cushion hole. Wrapping a 5pt sub over the front of a seat is a no-no.

This is just to give you ideas. There are many pros all around the country who can set you up. I guarantee if you just go observe a trackday you will mean someone who knows a local race car builder who can help you.

Bill32

Yep, so many people don't understand (or don't know about it) that AND most of them don't have the subs adjusted correctly.

ErikwithAK01

Which is why i ask the experts thanks for the responses guys, i really appreciate it! Ill go with either 5 or 6 point for sure then, and thanks for the pictures of your old setup fatbillybob, that will give me a starting point. Does anybody have a specific brand of harness that they prefer? And why? Also, what are your opinions on latches vs cam locks? Assume price is not a factor, what would be your ideal setup (short of a cage of course)?

Uhhtaken

I was thinking of going with a homemade setup like this but after seeing how the bar is mounted with just 2 bolts im starting to reconsider. Looks like a nice little setup but dont know how I feel about just 2 bolts.

ErikwithAK01

I will be mounting mine with a couple rods, one at either end that attach to the seatbelt assemblies bottom bolt, and have heim joints that thread into the bar so I can adjust the tension. I will also likely put an angle on the mount so that it shores up against the base material, under the interior panel. My thoughts so far

Uhhtaken

Nice when you do will you be posting a thread with pictures to show others? Might still try it.

fatbillybob

110% agree. There is nothing harder to build than a dual use car especially if you are not an engineer. A racecar is easy. To build a car you need to be a chess player. You can't think 2 dimensional checkers because crashes are multi-dimensional multiple hits odd angles with rollovers. My thinking was the only force on those bolts was my weight and now my weight is spread over 2 bolts not 1. However, connection does change the forces and a simple side impact could easily destroy belt retension. There is not simple solution only compromises.

ErikwithAK01

Just so happens that I AM an aerospace engineer for the Boeing company and have a 2,000+ square foot shop at my disposal, 14" gear head lathe, bridgeport milling machine with all the bells and whistles, 4-post lift, stick,mig,tig machines, the works. Also an avid photographer, so you WILL get a comprehensive writeup when I do this project

Uhhtaken

Well then i look forward to seeing your in-depth guide and eventually going down the same path.

c4cruiser

Sounds like you are describing a Sparco harness bar. I have one in my '87 and it's much sturdier than the old R-D Racing bar I had before.

IIRC, the Sparco bar is made of stainless (maybe chromaloy?) tube and probably .125 wall thickness x 1-1/2 OD. The bar is bent based on the vehicle to provide the correct angle for the belts to pass thru the seatback so they are horizontal to the top of the driver's shoulder or provide for no more than the maximum angle allowed by various sanctioning bodies. (+/- 20 degrees??)

moespeeds

I made one for my C5. The issue you have with the single bolt mounting is that is a hard impact the whole bar can rotate around that bolt. My very simple solution was to remove that plastic molding, and weld a heavy duty tab to the harness bar plate that butted up against the roll hoop. This would prevent any rotation is a crash. I made mine out of DOM tubing to the SCCA roll bar spec, .120 wall I believe. You could screw around and try to prettty up the install by cutting the molding so you can keep it in place, but for me safety trumped aesthetics.

ErikwithAK01

that is PRECISELY what I have planned! I took the panels apart to examine it before jumping into this, and discovered that not only would that be a feasible solution to the described problem, but it would also eliminate the need for struts (if that were my only goal for the bar) but being as I am not building this to any sanctioning bodies rules, I am designing it to stiffen the chassis as well...so struts it is...or just trussing the whole thing, mating the floor of the car (at the hump directly behind the seats), to the bar itself.