Triumph Sports Cars

I noticed that in most of the swaps a lot of the guys are not running full or partial cages. I was concerned about frame flex by the added torque and HP of an engine swap. Is this not really a big issue? I will be running about 320 HP 300 TQ. It will be a driver to take into the twisties and will not see any real drag or racing use.

Thanks

I think it's a big issue! I have a full cage inside my MGB-GT, which was of course a unit-body car with a steel roof to begin with. The before/after roll-cage comparison was pretty dramatic. I love what the added rigidity did for the feel of my car.

Even a four point roll bar will help.

Then again what you think you see is not necessarily what you are really seeing. Take Ted's TR6, for example. It may not have a roll bar, but that's not a stock Triumph frame underneath, either.

[www.britishv8.org]

Thanks for the responses. I forgot to add that it is for a TR6, I like the idea of a roll cage, but now it is just a matter of making it fit. I am a fairly big guy and my shoulders already touch the doors and my seat is back further than the seat track normally allows (I am 6'3, 180lbs) so adding more bars into the already tight cabin seems a little daunting and may make that car less comfortable. Ideally I want the car safe and stiff, so I will see what type of room I have to work with once the interior is back in.

I am 5'11" and about 200 lbs and I can get in and out of my Gt6 with a 6 point cage. It's not the easiest thing to do but it never really was, a removable steering wheel would help out a bit. I don't have my car on the road yet but the cage and bars I have added have stiffened up the frame remarkably, just testing with my body weight. I am aiming for about 400 hp and ? torque so i wanted the frame as stiff as feasible, the frame rails are so close together in the middle I think you could do some damage if you get your power hooked up well enough.

Besides the flex and need for styiffness the general week points are the lower A arms mounting points and the diff. upper mounting points the crack and brake on the early ones more than the lateer ones
Mark

I am thinking that a good frame to use would be the tr 4 to the tr 6 irs frame It is a much stronger frame and should fit with out too much moddifyng.
Mark

Usually the weakest point of a frame in regards to torsional strength is the narrowest point. On the TR6 frame that's between the rear body mount and the rear suspension spring perches. If you can fit a bar with rear supports that mount on those points you'll do the most to stiffen the chassis and it shouldn't intrude on the passenger compartment too much.

Ryan,

As you know I fab'd a 6-pt cage for my TR6/M3. I drove it quite a bit without the panels on it prior to cage installation and again after cage installation still without the panels. Even though I strengthened/beefed up the stock frame it was quite apparent how much it improved the stiffness. This is obviously a good thing but still amazed me how much easier it was to get the car into a drift as it was already pretty scary. I made a hoop under the dash up front that mounts to the body attach points and a four point in the rear that mounts to the body attach points behind the seat then the rear supports travel through the bulkhead and down to the rear frame where they bolt to an attach plate I welded on. The side protection bars were made removable and I honestly couldn't feel a difference with them installed or out. I also made a removable diaganol brace from the rear hoop to the front center body mount by the tranny but didn't test any with it installed. My guess is that with the 1000lbs of body panels bolted back on they may become a more significant piece but I'm still waiting for its return from the body shop so I can't tell quite yet.

I also incorporated a harness bar on the rear section and made it to fit under the TR4 top bows I'm using on my project. I have to say it does take away some useable floor space and limits the seat travel. I had tried just about every seat possibility with the exception of an aluminum racing bucket and eventually found that after modifying the typical Miata reclining mechanism I could get it far enough back for suitable comfort. I also made brackets lower than the standard ones so I could suck it a little closer to the floor to keep me from splitting my melon on the top hoop. In retrospect or possibly in the future I may re-fab the rear section and give it a little more rear cant which would provide me additional room.

I'm not racing this outside of an occasional track day so it was built strictly for stiffening purposes and street safety. It does not meet the height above helmet requirements.

Bottom line, it made a very noticeable difference.

Dave

Ted Lathrop's TR6 frame:

It hasn't come up yet in this thread... but a new RATCO TR6 frame would be significantly stronger than an original (stock) frame... especially if the original frame has suffered corrosion, normal metal fatigue, or collision repair.

RATCO is one of British V8's vendor sponsors, and I've really enjoyed getting to know the proprietor, Tony Vigliotti. He's a very helpful and sharp guy, and he's enthusiastic about hot-rodding old Triumphs. (His company was born out of a TR6-V8 project with a 6" widened body and a Rover V8.) I'd certainly give him a call!



Also, there's a LOT of valuable information in this brochure from Tony's website:
RATCO Frame Informational Booklet (26 page PDF - with great photos!)

V6 Midget Wrote:
-------------------------------------------------------
> Usually the weakest point of a frame in regards to
> torsional strength is the narrowest point. On the
> TR6 frame that's between the rear body mount and
> the rear suspension spring perches. If you can fit
> a bar with rear supports that mount on those
> points you'll do the most to stiffen the chassis
> and it shouldn't intrude on the passenger
> compartment too much.
>

Bill,

Thanks for this input, I braced this area as much as possible during my frame off, but a cage that hits the points you mention might be an adequate compromise.

Dave,

You always tell me things I know but don't want confirmed, not because you are incorrect, but it takes more time and money, and I want (and so does my wife) this thing on the road. But your before and after differences with and w/o cage is what I feared. As it sits it is prepped for a cage with reinforced attachment points, I will try and get it on the road and add some sort of cage this winter probably.

Curtis,

I think a Ratco frame may have been the way to go and if I were starting over I would go that route after all the repair and strengthening I put into the original frame. But I am well past that point now.

Hey Ryan

Picking up on Bill's input, I think the key to frame stiffness is to employ the idea of triangulation. The frame on the TR6 is a basically flat platform- not a great concept for a structure that has twisting moments inputed by your foot on the gas of your M3, or uneven terrain on the road. The greatest gains will be made by building up in the middle, and back down to the ends- like a common truss. I have two roadster hoops just behind the seats which go down to the spring tower section of the rear frame. Just below the body line I have tubing that begins at the forward body-mount point in the floor pan, angles up as it goes back, attaches to the hoops, just under the rear valance and then start their decent into the trunk area where they tie into the floor pan at the most rearward frame/body attachment point. I've created a truss system, in effect. The points of the truss are as far away from each other as the confines of the car allow. As you may have seen, I'm using this TR6 frame under my widened TR3 project, but the Ideas could be used with the TR6 body I'm sure. The side bars make entry and exist more effort, but it's kind of comforting to see those bars between you and the SUV's in intersections. paint them the color of the car and they integrate nicely into the over-all design. Oh, I also weld in a dash bar that runs between the upper door hinge points just under the dash. The bar connects to the body at mid-span. Again this adds to the 'crashability' factor, but also deals with the TR3 body's tendency to twist through the front cowl section.

Here's another thing I found. My TR6 frame was a very rust-free example from California taken from a late TR6. I had the frame sand-blasted and found nearly EVERY weld to be of poor quality. I'd describe them as 'cold'. I have a '57 TR3 as well and the difference in welding is like day and night. The late '70's was not a good time in England, and the quality of work coming out was often compromised. I ground down and re-welded over EVERY weld on my frame before it went to powder-coat.

In conclusion, having raced in vintage class, I can say we all build bars and cages for two reasons. The first is safety, but the second is to stiffen the whole car. I remember racing my TR3 that had a roll bar with a removable diagonal brace down to the passenger foot-well. On cornering you could hear the bar rattle at the bolted top mount. Remember that the suspension is designed to handle the car and the frame should not be part of the suspension!... unless you're driving a go-kart, in which case the frame itself becomes a tuneable component of the system.

Hope this gives you some motivation to consider a bar/cage set-up

Randy