Roll Bar survey

[gjh2007]

Morning all:

Well as my diff project finally is coming to a close I will be attending to re-assembling my interior; remember this all started with installing seat belts in a car with no mounting points!

As part of my interior assembly I plan on installing the roll bar I have been dragging around the east coast for almost 30 yrs. I never installed it in my 1st 250 because it caused seat travel issues. Now I plan on sawz alling the rear support & readjusting the angle to allow my seat to slide back. I have noticed two variations in bars, but many seem to have all 4 legs on the parcel shelf. What I would like to get are the final dimensions; length of legs & angle of rear support so I can adjust mine.

I guess I could always modify mine to sit on the parcel shelf.

Any help would be appreciated.

p.s it's getting cold in my gar gage 40 all day yesterday, even with the sun shining in! /ubbthreads/images/graemlins/frown.gif

 

[Tinster]

It really depends on whether you want the
roll bar structural or cosmetic.

Tac-weld to the shelf would be easiest
but offers no protection in a roll-over.

Cooling down here in the Crypt as well.
Only made it up to 87* yesterday with
puffy white clouds drifting over the azure
blue ocean.

A bone chilling 84* predicted for today. Looks
like it will be long pants and socks for the
next 5 months. Beach bunnies switching over from
bikini to coverall one piece. Blargh!!


dale

 

[TheAssociate]

Well, measuring does not really matter in my case because we have different cars. But I can tell you that putting all four legs up on the shelf is the way to go.
I had another rollbar for my previous Spitfires, and it had two legs on the floor, and two legs on the parcel tray. The design I have now(which is also chrome - YEAH!)has two legs on the parcel shelf and the other two legs bolted to the inner fenderwells.
Being 6' the first rollbar made the car almost unbearable. The second(that I am currently using) is useable, and doesn't impede my driving too much. And as far as I can tell, this rollbar would definately work in a crash. To me, there is no point to having a "cosmetic" rollbar.

Hope the descriptions help a little.

Adam H.
____________________________________________________________
1972 Triumph Spitfire.

 

[Brosky]

Here is mine, bolted into the floor:

From above, probably the same unit you have:

 

[Alan_Myers]

Hi Gary,

What you describe is a "street" roll bar. It's certainly better than nothing, but wouldn't pass safety inspection for most racing. Race sanctioning bodies usually require the roll bar be mounted to the frame and look for 2" clearance above the top of the driver's helmet, among other things like the thickness and type of the steel (usually .090" tubewall, mild steel) diameter of the bends, location of supportive strut joints and the way it's assembled (welded and bolted), all with an eye toward safety. As a side benefit (to adding all the weight of a roll cage to a car that is trying to be lightened) is that a true cage offers a lot of added rigidity to the chassis and can improve handling.

Of course, that often means with a true race-quality bar that the convertible top can't be put up and down, so the car becomes strictly open cockpit (or strictly enclosed). Lowering the seat and changing the driver's layback position are other possible options to get the required clearances, and is not uncommon.

"Street" bars - which some consider mostly cosmetic but I'd say offer a bit more protection than no roll bar what-so-ever - are popular. They look cool and still allow the top to be raised and lowered. But, they should never be confused with a true roll bar or, better, roll cage. A "street" bar simply can't offer a great deal of rollover protection and won't improve structural integrity or rigidity of the car, the way a true racing cage will.

I can't really help you with dimensions, but putting a little more rearward rake (i.e., cutting the support struts) you have to watch carefully that the rear window of the top and the top bows themselves will still clear. The "street" bar that was in my TR4 offered just about the most possible height, but still allowed the top to just barely pass over it (with the bows in the "raised" or taut position). Perfect! Until I put a factory hardtop on the car. Now it interferes with the backlight or rear window. That's why I'm selling it and will need to install a custom built roll bar/cage.

As to mounting, you need large, heavy backup plates at each foot of the roll bar, that go under the sheet metal and "sandwich" it for the best security. The bar's integrity is still limited by the strength of the sheet metal it's sitting on, but the bigger the feet and backup plates, the more stresses will be distributed. By the way, I used one of the mounting bolts fo the roll bar for a seat belt anchor, too (seat belt anchor points should also use heavy mounting plates, approx. 1/8" thick steel).

P.S. Oh, and I strongly suggest you avoid any sort of bolts or whatever protruding from the roll bar near or behind the drivers head, and consider installing padding on the bar. I've gotten head insuries from the roll bar in my car in an accident, which is sort of the exact opposite of it's purpose, even if just a "street" bar!

/ubbthreads/images/graemlins/cheers.gif

 

[Brosky]

Amen to everything that Alan just said!

 

[gjh2007]

All points taken, I was never intending this bar to be race worthy, just a little something extra. Also very clear on the padding on the bar, unfortuneately when I got the bar back in 76 it had a nice foam padding & a vinyl zip on cover, but I can't find it, so will probably have to get something from Jegs. I doubt I will ever be able to find a nice vinyl zip on unless I have one made at a boat canvas shop, maybe out of black codura?

I guess I don't have much to lose by cutting off the rear legs & checking the bar for fit on the floor & with top up to determine the length & angle of the rear legs...

 

[trfourtune]

alan,
great comments again. one point that i would like to suggest to all is, with the straight axle cars we can add a steel bracket or frame up from the frame to the underside of the parcel shelf to reinforce those "street" bars. watch out for the bolts that hold the shocks though.
rob