Need input on modifying rollbar

[vanwyk4257]

I was trying to come up with some ideas because the existing crossbar on my rollbar was way too low to mount the shoulder straps. I have a harness bar for the car, but it mounts to the C-pillar and is too high.

It dawned on me tonight that the crossbar is just bolted to a couple tabs welded to the hoop. Is there any reason you engineers/safety scrutineers can see that I shouldn't just be able to have a competent shop weld new tabs up higher and remount the crossbar?

Here are some pics for reference, let me know what you guys think.

[jester911]

Just have a bar totally welded in place where you need it. Don't bother with the old bar.

[Cory M]

If you weld in tabs that are of the same thickness, material, shape, orientation, and weld quality as the original tabs it should be fine. If you want to improve the design without building a whole new rollbar you could have a new piece of tubing notched, and welded in the optimal place by a good cage fabricator - it wouldn't cost too much and would make it a more robust design.

[barney911rs]

I would get the bars welded in unless you need to be able to pull them out for some reason. It looks like a dedicated track car, so I would consider adding a diagonal cross brace then then fit the horizontal bar in on both sides of that. This would make that roll bar MUCH stronger. If you plan to start racing, putting in a full cage is the best solution.

[vanwyk4257]

Thanks for the suggestions guys. I will probably just have a bar welded in for now. John, I definitely intend to have a full custom cage built if/when I start racing with the car.

[dfink]

Why do you say the bar is too low for the harness it look like when you bolt it in it will rotate at least 4" higher than shown. As long as it does not have more than a 30* angle down it should be OK. Or just get a harness that attaches to the rear seatbelt mount.

[vanwyk4257]

dfink, the bar won't rotate when it's bolted in and it's about 6" below the bottom of the shoulder harness openings in my seat. I have it raised up ni some of the pictures, I don't know if that's what was throwing you off a bit. The other problem is because I'm 6'4" I have the seat back quite a ways, making the angle down more of an issue.
It should be relatively simple to either weld on some tabs or have someone weld in a new bar higher up to solve the problem. I did purchase a set of 6-point camlock harnesses from Moto-Delta, I'll work on installing them once I get the bar setup.

[Jim2]

vanwyk, are you tracking your car? Are there any rules which require you to have a diagonal within the main hoop?

I just helped a friend put a bolt-in bar in his 911 and the only reason I can see your belt bar being removable is for potential rear passengers, otherwise if the cross brace is welded in it won't hinder removeal of the bar.

I built a similar belt bar for a customer and charged him 1.5 hrs plus material, a little over $100. Try and find a cage fabricator or off road truck builder if you don't allready have someone lined up.

You might also consider belt retainers welded onto the bar especially since the drivers left belt will be located near or on the bend towards the drivers side b-pillar.

[vanwyk4257]

Thanks for the input Jim. This will be a DE and Autocross car for now, so there shouldn't be any rules requirement for a diagonal as far as I know. I think I'm going to do what you suggested and find a ship to have them weld in a straight bar instead of the curved one so the harnesses will stay put better. I'll probably also have them weld in loops to retain the harnesses in place better.

If/when this becomes an actual race car my intentions are to ditch the rollbar and commission a full custom cage so the rollbar is a temporary solution for DE's.

[BoxsterGT]

Don't just take it to a local welder, find a fellow who does cages for a living.

The cross bar is there for a reason, and must be the correct height for you & your shoulder straps.

More importantly, some sort of adjustable head rest behind the seat is needed.

Safety is the first consideration.

Len

[175K911]

Personally, I'd want to go a bit higher. You're positioning it based on the slots in the seat, but where are your shoulders? If you're going to be wearing a HANS (which is a very good idea) the new school of thought is that the shoulder belts should be parallel to the ground, at a height equal to the top point of the HANS as it sits on your shoulders in the seat.

[Cory M]

this thread is from 3 years ago