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Triumph TR6 - Roll Bar Question

When I bought my 75 Tr6 it came with a homemade roll bar.This roll bar was bolted to the rear inner fender wells in 2 places, where the upper seat anchor bolt is and through another hole drilled through the inner fender well.

Last winter I ran a 2 diagionals across the hoop for strength and also added a piece of bar between the
lower ends of hoop. (this bar sits on the rear parcel shelf/deck and is now also bolted to the frame bolts that are found there)

But (the plot thickens............ ) this has resulted a uncomfortable ride for my 6ft 2in body as the back of the seat movement is now restricted.

So, I'm currently thinking of either nuking the rollbar completely or making my own 4 pt bar that sits far enough back so it will not restrict my seat movement

my questions are:

1. Do I really need a roll bar for my street driving?
(it is occasionally a bit spirited!)

2. On a 4 pt roll bar, where & how do the 4 pts connect?

3. How far back can my roll bar be mounted? I recognize that the height of the bar would have to be reduced to clear the top. Therefore how effective is the bar if my head is 2-3 inches about it?


Thanks for your help !!


Aivars Berzins


ps I did notice that my roll bar when installed seemed to give the car a more solid feel - I guess less body flex?
A. Berzins

1) If you are running a harness that goes over both shoulders, you need an effective roll bar or a at least a roof over your head. Standard single shoulder belts and lap belts provide you with more flexibility since they would allow you to drop down in the event of a rollover incident. Still not a really good solution, but better than being held up by shoulder harnesses with nothing above your head. Since "spirited" driving leaves much open to interpretation, only you know how close to the edge you are pushing the car's limitations along with your own limitations. Let you conscience be your guide on this part of the equation.

2) I am not following you completely on the 4 point, but the SCCA General Competiton Rules requires one diagonal from the top section to the opposing side section and one horizontal below the main hoop. If you are refering to the 4 points as the mount points to the body, then where you have it is pretty much as good as it gets for a street roll bar while maintaining room. The diagonal and the cross piece sound like the root of your interference. They may need to go or be redesigned to have seat clearance curves (not unheard of in race cars) if you want to keep the bar.

3) If you head is within 2-3" of the bar, you need to make sure that it is least padded. The GCR requirement is 6" of separation and this with a helmet. If this is a typo and should be "head is 2-3" ABOVE it," you do not have an effective bar. If you decide to sacrifice some of the top down aspect of things, one of the factory hard tops will give you a little more room to play with regarding bar dimensions and placement. You can always unbolt and remove the hardtop if the weather permits, it just cuts down on the spontaneity of open car driving. Another aspect of the hard top is that it too reduces body flex since it provides additional support around that big hole in the middle.
SteveP

Hi Steve,
Just some clarification on my sort of vague thread.
(the coming blizzard seems to have numbed my brain cells)

1. I am currently running just lap belts. Shoulder belts were removed by PO

2. What I meant by 4 pt mounting is that the roll bars I've seen have 4 legs/mounting pts. Usually 1 mt pt at the end or bottom of each end of the hoop , then 2 "legs" running out 45 degrees rearward from the vertical of the hoop. (basically running downward toward the trunk area)
I was wondering where/how these pts are connected? The only frame bolts I can recall, are the onesthat I'm currently using. Does that mean that the 2 rearward running "legs" are just welded to the body?


My concern with my current design is how effective are my mounting pts that go thorough the rear inner fender walls? (I know these inner wells are just sheet metal)

Also, you are correct, the diagionals I have installed in my hoop for strength are the culprits regarding my seat movement problems.

3.Hence, I thought by moving the whole roll bar back - I could fix the seat problems. But, by doing so the height of the roll bar would be reduced and restricted by the top. Therefore my head probably be above the height of the roll bar - cancelling any rollover benefits - I guess I can always duck?


Or maybe, I'm just making a big deal out of this? I just thought either I would have a roll bar that works or not one at all.

Thanks

Aivars

Aivars Berzins

Aivars,
I'm at the same point right now trying to design and
build a roll bar that works but doesn't screw up the interior. The 2 legs running rearward at 45 degrees should squeeze between the gas tank and the fender,
actualy go through the sheet metal of the trunk shelf and butt up to the frame underneath with a 5"x5" plate
welded to that leg and just sitting on top of the frame. Then another plate on the under side of the frame is bolted with 4 bolts to the plate welded to the leg sandwiching the frame in between. This how I've
seen it done on some dedicated TR6 vintage race cars.
If the roll bar is bolted to sheet metal only I can't see it doing much to help in a real roll over situation. The racing TR's don't care about convertible
tops so they go head and make the roll bar as tall as
they like. No good for us street boys. I have seen one TR with a collapsible roll bar, that is it took the shape of a roll hoop just protecting the driver. When the top is down the top of the hoop can telescope up
on both up rights and be secured with two half inch
pins that insert through both sleeves. This method would be good for someone tall like yourself but I'm
not sure any race sanctioning bodies would consider
it a safe roll bar. The botom of the two up rights
wether it is a roll bar or hoop must bolt into the
diff arch that is directly under the shelf behind the seats. It's a big job, still not convinced I need it except I would like to take the car out on the track
at some point and I know they are not going to let me with a proper roll bar.
Chris
Christopher Trace

Hi Chris, Thanks for your reply and help. Right now I'm leaning towards just removing my roll bar and forgetting about it. To make and install a roll bar that would be effective and still not hinder my seat movement seems to be elusive. (Or at least an big issue to install) I can't see the point of just having a "pretty" roll bar that really doesn't do anything and possibly could be a cause of injury - rather than preventing it.

Realistically, what are the odds of rolling my Tr6 with "normal" street driving?

I guess I better start practising my ducking techniques!

Aivars Berzins
A.Berzins

Hi Aivars,
I have a roll bar in my TR4a which was built to CASC standards by Canadian Stock Cars in Newmarket. They mostly supply equipment and parts for the race community but will custom fabricate as well.
The bar just fits under the softtop, and is about an inch or two above my head (I am about 6 feet tall.)
I assume your head does not contact the softtop although in my Spitfire things are close if I sit up straight!
As Chris and Steve have pointed out, there is little protection if the bar is not above your head, although it should stiffen the car and give some additional protection in a side impact.
I am not sure from your description how the bar interferes with the rearward movement of the seat, I visualise the legs of the rollbar being on the flat ledge behind the seat.
Anyway, you need at least one diagonal brace to prevent it folding, and two rear braces at least 30 degrees from vertical. As Chris mentions, the feet should be big, and throughbolted to an equal size plate the other side. The radius of curvature should not be tighter than 3.5 times the outside diameter of the tubing, and mandrel bent. The tubing should be seamless mild steel of 1.75 in diameter and .125 inch wall thickness or slightly smaller chromemoly. Welding should not be Mig, but must penetrate completely. If you want to use a 4 point harness you need a horizontal bar to anchor the shoulder straps and the downward angle of the straps should not exceed 45 degrees.
Don't know if all this is practical for you for a street car but I can send photos of mine if it will help you decide.
Simon.
Simon Rasmussen

This thread was discussed between 22/01/2005 and 24/01/2005

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