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Step 12Creating the pulling arm
*Line up the top and bottom arms together on a flat surface with the longer piece, with the hole in it, on the top. Make sure the pieces line up on the long straight side and at the bend. If they don't, bend them until they do. The arm should look like a backwards "L".
*Coat 2" sections of the tubes with flux at 8" intervals (or so) and braze the tubes together. Make it strong enough to be stiff but not overkill. Braze on both sides of the tubes.
*Let arm cool or dip in water. Place the cart on a flat surface with blocks under the ribs to keep them parallel to the ground. (The same position for brazing the wheel wells and dropouts.)
*Support the arm with three piles of bricks/scrap metal so that the top of it is 1" below the bottom of the dropout on the center rib. This should be about 4 1/2" down from the main frame tube. If you are not using 26", 700c, or 27" wheels for the trailer, or if you are not going to make the trailer for a bike with a rear wheel of those sizes, you will want to adjust this dimension. The goal is to have this arm be parallel to the ground and meet the bike 2 inches under the rear axle. The bottom of the trailer should be at least 4" above the ground.
*Flux and braze the arm to the front and center ribs at the same height. This braze needs to be very strong.
*Measure the distance from the point just before the bend in the arm to the front of the spine at the same height. Cut the arm brace to fit here, ensuring that it intersects the arm at least 14 inches from the hole in the arm, and that the angled cut is aligned so that the mitered side fits the spine, and the angle has a decent fit with the arm. Again, accuracy is not that crucial. It just needs to be strong.
*Coat 2" sections of the tubes with flux at 8" intervals (or so) and braze the tubes together. Make it strong enough to be stiff but not overkill. Braze on both sides of the tubes.
*Let arm cool or dip in water. Place the cart on a flat surface with blocks under the ribs to keep them parallel to the ground. (The same position for brazing the wheel wells and dropouts.)
*Support the arm with three piles of bricks/scrap metal so that the top of it is 1" below the bottom of the dropout on the center rib. This should be about 4 1/2" down from the main frame tube. If you are not using 26", 700c, or 27" wheels for the trailer, or if you are not going to make the trailer for a bike with a rear wheel of those sizes, you will want to adjust this dimension. The goal is to have this arm be parallel to the ground and meet the bike 2 inches under the rear axle. The bottom of the trailer should be at least 4" above the ground.
*Flux and braze the arm to the front and center ribs at the same height. This braze needs to be very strong.
*Measure the distance from the point just before the bend in the arm to the front of the spine at the same height. Cut the arm brace to fit here, ensuring that it intersects the arm at least 14 inches from the hole in the arm, and that the angled cut is aligned so that the mitered side fits the spine, and the angle has a decent fit with the arm. Again, accuracy is not that crucial. It just needs to be strong.
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