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After determining the height and mount locations for the finished roll bar, fabricator Mike Minette cut a length of 1.75-inch, .120 wall steel tubing with some extra length to fine trim when finished. Do not cut to exact length since it is easy to miss on the allowance for the bends. Then he chucks the tubing in his mandrel bender to get ready for the first bend.
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The first angle is bent into the tube. This requires a gentle touch on the power control.
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Minette uses an adjustable angle finder to make sure the bend is exactly 90 degrees.
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The bar is now laid on the floor while Minette finds the exact center. This is critical to make sure the bar fits correctly.
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Once the center has been marked, Minette marks the tubing for the location of the second bend.
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The second bend is made on the tube bender.
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The bar is laid on a flat surface and checked for square from top to bottom.
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A second check on a flat table is done to make sure the legs are not twisted in relation to each other. If they are, they can be fine-tuned with a long piece of tubing.
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After checking the position of the bar, Minette locates a solid place on the frame to mount the sleeves that the bar will slide into. The sleeves should be mounted to a major frame member and the brace should feed the potential load of the car into the frame. This steel plate will be welded to the rear suspension pickup towers.
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The sleeves are cut from tubing just slightly larger inside than the outer diameter of the roll bar tubing so they will have a snug fit. We are using this method of attachment so the bar can be removed though the body.
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Minette made the sleeves from two sizes of tubing to get a wider base to weld into the chassis, yet keeping a snug fit on the bar. Here he TIG welds the sleeves together.
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The bar is dummied into place and checked to make sure it is square. Then everything is tack welded together. When everything is finished the welds will be completed.
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Once installed the sleeves are drilled for two Grade 8 or NAS bolts that will hold the bar in place. This drilling jig keeps the bolts at right angles to the bar. The bar bottoms in the sleeves and the bolts keep the bar from falling out. Minette welds retaining nuts to the backside of the sleeve to make removal easier.
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Here we add a rear brace. Minette uses welding wire to check his angles before cutting steel. Cut a longer piece than needed and trim to length after bending.
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A tubing notcher cuts a curve into the top of the brace tubing so that it will fit tightly around the roll bar.
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A grinder is used to fine-tune the notch. A close fit is essential.
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A hole is drilled in the bottom of the brace for a short length of spacer tubing that will prevent the tube from collapsing when it is tightened.
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Here is the bottom of the brace with its thick flanges tacked into place.
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The brace is welded to the top of the roll bar.
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Checking the bar height shows plenty of helmet clearance under the bar. Success!
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Roll bars not only provide protection, they add a "racey" look to any car.
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