1969 Triumph TR6

EXHAUST FUME SHIELD

RESTORATION PROJECT: DEC 2007

Restoration began Jan 2006

December 2007: Exhaust Fume Shield Design Drawing

I carefully measured the dimensions inside the car with the topfully closed. My concept was for a removeable Exhaust FumeShield , should maintenance be needed.

1969 TR6 RESTORATION

SAFE HARBOUR STATEMENT:This “How I installed it” essay is presented asgeneral information and has been prepared by aTriumph TR6 owner with very limited auto mechanicknowledge. The procedures shown in this documentare not professional instructions and are not intendedto be such. The EXHAUST FUME SHIELD for a1969 Triumph TR6 was successfully designed, fabri-cated and installed with these amateur proceduresand I was not injured during the process.

The following essay documents the design, fabrica-tion and installation of an exhaust fume shieldlocated behind the twin seats in the car’s cockpit. Theexhaust fume shield is nonstructural and is notintended to be a roll bar. It will offer no protection inthe event of an auto accident.

EXHAUST FUME SHIELD:

I designed this exhaust fume shield in an attempt tocreate a barrier that might help keep some of theexhaust fumes from entering the interior portion of thecar. Folks with asthma, allergies or other chronic lungconditions are sometimes bothered by the exhaustfumes which somehow seem to roll forward acrossthe trunk surface of the TR250 and TR6 models. I amone of those folks; therefore my design attempt.

Better quality air: This was my primary design crite-ria. After installation, I immediately noticed a higherair quality while driving the car. From this standpoint,my design is functional. It also seems to act as a windbarrier and the car interior is quieter and cooler onhot driving days. (Unintended bonus for sure !)

I also wanted the fume shield to compliment the sleeklines of the Triumph TR6 and not detract from theoverall “sexy/racy” appearance.

I live in an climate prone to sudden rain downpours. Iattempted to design the exhaust fume shield so as tofit beneath the convertible top when fully closed. Ialso wanted to be able to remove the shield forroutine maintenance. I accomplished both designtasks.

For the average Triumph owner with limited or nomechanical skills, such as this author, fabricating thisshield is beyond our capabilities. I gave my designdrawing to a professional, marine shop for bendingand welding.

The frame is fabricated from 1 1/2” outside diameter,marine grade, structural aluminum tube. I specifiedmill finish surface because it would be painted. I usedaluminum because it is easier to bend and less costlythan stainless steel. The fume shield is not a roll barso high strength was not an issue for the frame.

The two mounting brackets are fabricated from 1/4”thickness, marine grade, stainless steel plate with 1 1/2” inside diameter , stainless steel holders.

I specified stainless for the mounting brackets simplybecause it is stronger than aluminum. I wasconcerned about the overturning moment upon thewelds at the base of the two support legs.

The fabrication was exactly to my design drawing andI paid $250 for the finished frame.

EXHAUST FUME SHIELD

This is not a particularly difficult project since most ofthe work is performed by specific professionals.Most car owners can easily paint the frame andmounting brackets and install the Lexan window. Nospecial tools are required other than a 5/16” UNFdiameter thread tap that is readily available at storeslike Sears. An electric drill and socket set are theinstallation tools needed.

Fume Shield & Mounting Brackets:

Before I paid and left the frame fabricator, we dry fitthe fume shield frame and fully raised the convertibletop to verify clearances. My design permits shorten-ing of the two support legs if needed. My designmeasurements were correct, the fabrication was exactly as designed and no adjustments wereneeded. I was well pleased with my design shape.

Fume Shield & Mounting Brackets:

The independent supports and noncontinuous ovalShape allow for car body twisting movement.

The window material for my fume shield is fabricatedfrom 1/4” thickness, clear polycarbonate (Lexan).The Lexan material was used because it is not asprone to fracturing and cracking as some of the lessexpensive plastic sheet stock. I paid $120 for this.

I did not attempt to cut and shape the Lexan to finalshape myself. I took the aluminum frame to a customplastic fabricator for cutting. The Lexan window isexactly the same dimensions as the outside edge ofthe aluminum frame. This overlap of the tubingcenterline is what allows space for the bolts andwashers. It also makes it easier to properly centerthe Lexan on the frame for final installation.

The Lexan comes with a thin plastic protection sheeton both sides. I left the plastic in-place in order toscribe the location of the bolt holes I needed to drilland to help prevent splitting. I used the verticalsurface of a coffee mug to ensure the Lexan andframe were properly lined up. Lexan WILL split if youattempt to drill a large hole. I began with a 1/8” pilot.

P 3

EXHAUST FUME SHIELD

Temporary Placement Studs:

I had the Lexan cut to the exact footprint of theoutside edge of the 1 1/2” OD tubular frame. I figuredthat would make it easier to set the Lexan window inan exactly centered position. Also, I anticipated Imight have difficulty determining the exact centerlineof the tubing when it came time to drill the bolt pilotholes. The footprint concept worked very well.

As seen in the photo above, a coffee cup easilyprovides the proper vertical stop for the horizontalpositioning of the Lexan.

I marked off a points 3/4” in from the outside edgeand equidistance from the window centerline. Islowly drilled a 1/8” pilot hole thru the Lexan andaluminum tubing frame, as shown above. I thenunchucked the bit and left it in the hole.

I purchased a 6-pack of 1/8” spiral bits to use themas placement studs. I slowly pulled the drill bit out ofthe first pilot hole, while holding the Lexan tightlyagainst the frame. Then I inserted the spiral stud anddrilled the remaining pilot holes in the same manner.

The Lexan fabricator instructed me to leave theplastic protection sheet in-place while drilling orcutting. None of my holes split the Lexan, so that wassound advice.

After the 1/8” pilot holes were drilled it was time topaint the frame and mounting brackets. Primer, threecoats of car body red and two clear coats.

Enlarge Pilot Holes

My design detail specified 5/16” UNF bolts. My nextstep was to enlarge the holes in the Lexan and alumi-num frame to 1/4” diameter. I unchucked the first 1/4”bit and left it in-place as a placement stud. I enlargedthe remaining four holes for a total of five holes in theupper half of the frame.

EXHAUST FUME SHIELD

Tap Threads into Bolt Holes:

I tapped 5/16” UNF threads into the 1/4” pilot holesbecause I wanted to attempt to attach the Lexanwindow without thru-bolting it. I thought thru-boltswould detract from the clean lines of the frame whenviewed from the front side of the car.

Even with the sturdy marine grade aluminum tubing,fine threads with steel bolts provide minimal pulloutresistance. I figured if the wind caused the Lexanpiece to pull out, I could always go back and thru boltthe exhaust fume frame.

Finally, I enlarged the pilot holes in the Lexanwindow to matching 5/16”. Lexan is brittle and proneto stress cracking radiating from holes drilled thru it.To lessen this possibility, I hand cut 3/4” , fabricreinforced rubber washers to act as shock absorbersbetween the Lexan and the metal frame. It is difficultto see the black rubber washer so I have highlightedit in blue. You get the idea.

Fasten Lexan to Frame:

I fastened the Lexan window piece to the frame using5/16 UNF bolts and 3/4” diameter steel washers. I had previously spray painted the bolts and washersflat black. I finger tightened the bolts until all fivebegan to compress the reinforced rubber washers.Then I used a 9/16” open end wrench to slightlytighten the bolts a bit more; to maybe 2 pounds. I didnot want to risk cracking the Lexan this close toproject completion.

The bottom portion of the aluminum frame touchesthe soft top cover. I did not install steel bolts at thesetwo location because I did not want vibration to rubtwin holes in the material. I inserted rubber shims,which work just fine.

P 5

EXHAUST FUME SHIELD

I attached the exhaust fume shield to the car by thru-bolting 3/8” UNF bolts with nyloks and washers onthe underside. The frame is centered on the shelfbehind the two seats. I placed the car on jack standsfor safety. Installing these thru bolts requires twopeople.One person keeping the bolt head from moving whilethe person under the car tightens to nylok. I now musttrim the carpet.

I call this project a success. Exhaust fumes no longerbother my lungs, the car interior is quieter and cooleron hot driving days. Also, I think the frame designlooks appealing to the eye. My total cost for thisproject was right at $400.

EXHAUST FUME SHIELD

BCF Pennsylvania member Frank A. test drivesthe car with the new Exhaust Fume Shield. Nofumes enter the passenger seat either.