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November 2010 Willie's Workbench

Posted in Features on November 1, 2010 Comment (0)
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In the August 2010 issue, I covered trailer towing and hitches. I promised Part Two the following month, but it just didn't get done then. Here it is now.


Trailer Brakes: The state laws requiring trailer brakes vary widely. My feeling is that if the total load exceeds 1,500 pounds, trailer brakes are required. Most states require brakes on trailers with a total load of 3000 pounds and over. The general assumption is that most tow vehicles can safely stop up to this much additional weight. From my experiences, most trailers are under-braked. Pulling a loaded car trailer without brakes just doesn't make good sense. Sometimes, one will see a tandem-axle trailer with only brakes on one of the axles as a money-saving measure. To me, it just seems that if it takes two axles to handle the weight, it's going to take brakes on both of these axles to handle the braking needs.

Briefly, there are two types of braking systems: Electric and hydraulic surge. Electric brakes require an in-vehicle controller that's activated by the brake pedal, hydraulic pressure, or a moving pendulum that senses motion. Hydraulic surge brakes have their actuator mounted on the coupler. As the tow vehicle begins stopping, the pushing trailer activates a hydraulic plunger that sends pressure to the brakes. Both types have their advantages and disadvantages. Electric brakes offer more versatile control but require the tow vehicle to be equipped with a controller. Surge brakes allow any tow vehicle to make use of the trailer's brakes, but don't provide the range of control that electric brakes do.

Load Balance: The way the load on a trailer is carried is very important. It should be evenly distributed with the bias being toward the tongue. Without the necessary tongue weight, the trailer can, and will want to, pivot on its axis (the axles) and will whip from side to side. Depending on total trailer weight, tongue weight should vary from seven to 15 percent; 10 percent is about average. Small utility trailers have no problem with seven percent. For example, a 1,000-pound loaded trailer should have about 70 pounds of tongue weight. Remember, this is a minimum figure. As the weight and length of the trailer increase, so should the percentage of tongue weight. When tongue weight exceeds the capacity of the towing vehicle's hitch weight, special equalizing hitches that transfer weight to both the trailer's axles and the tow vehicle's front axle are necessary. When the required tongue weights can't be met, so called "sway controllers," which use friction from either a sliding bar or a stabilizer shock to resist sway, can be employed. Actually, these really do help just about any trailer, regardless of the tongue weight, to handle better.

Determining Proper Tongue Weight: There are several ways to do this. The first thing you need to know is the overall weight of the trailer when loaded. This can be calculated if you know the weight of your trailer and the weight of the load. You're better off locating a scale. The local dump is a good source for a scale, and they will usually give you a weight for free. Commercial scales at truck stops are another source.

Getting the tongue weight is a bit more difficult. While at the scale, you could unhook your trailer, leaving only the tongue on the scale, which is not particularly feasible. There are special tongue-weight scales that will give you a very accurate reading but are pretty expensive for one-shot use. Actually, coming up with the proper tongue weight is pretty easy by making use of your bathroom scale. If you know that tongue weight exceeds the scale's capacity, then use an offset lever arm. Take a quality piece of 2x4 or 2x6 and lay it across the scale on one end, and place the other end on a block of wood the same height. Position the scale and the block of wood so that they are exactly three feet apart. Now place the tongue of the trailer, at its hitch height, so that it's not centered but two feet from the scale and one foot from the block. To be even more accurate, place a piece of pipe or tubing between the scale and the board and the block and the board. Now multiply the weight shown on the scale by three to get the tongue weight.

With the tongue of the trailer on the scale, the load can be moved forward or backward until the proper percentage of tongue weight is obtained. Obviously, you don't need to do this every time you load your trailer. After the first time, you can come pretty close to estimating the proper tongue weight.

Don't overload your trailer! I used to own a tandem-axle utility trailer that had an 8x12-foot foot bed with 3-foot-high sides. I got a great deal on two cords of oak firewood. This wasn't the first time I'd hauled two cords of wood in the trailer, which had a 10,000-pound coupler and 3,500-pound-rated axles. The tires were rated at 2,200 pounds each. However, unbeknownst to me at the time, the weight of two cords of previously hauled dry pine was under 5,000 pounds, while the weight of this green oak was over 5,500 pounds per cord, for a load in the neighborhood of well over 11,000 pounds, plus the trailer weight. I was only a mere 4,000 pounds overweight! The outcome was a broken spindle on a busy freeway at rush hour, blocking all four lanes. Luckily, I hit no one and no one hit me.

Wiring: Anybody who has ever pulled a trailer has experienced wiring and light problems. The lights always seemed to work the last time you used the trailer-why don't they now? Suffice it to say that good, clean, tight connections are very important, as well as a very positive ground. Don't rely on the trailer ball for a ground. Use a separate grounding wire between the tow vehicle and the trailer, incorporated within the wiring plug. The first thing to check when lights don't work is the ground. Color coding the wiring can solve a lot of problems in the long run. SAE Standard J1239 calls for the following: white - ground; brown - tail and marker; yellow - left turn and stop; green - right turn and stop; blue - electric brakes; and orange - battery charge.

What About a Spare Tire? Nothing can more easily ruin a trip than having a flat tire on the trailer. If you don't want your cargo disappearing, you generally have to leave someone with the trailer as you drive to have the tire repaired or replaced.

Trailer wheels come in as many patterns as there are vehicles. The three most common are Ford passenger cars with five lugs on a 41/2-inch bolt circle, which is referred to as a "5 on 41/2"; Chevrolet wheels are 6 on 51/2; and the Jeep-Ford truck pattern is 5 on 51/2. To determine the bolt circle with an even number of bolts, measure from the middle of two holes directly across from each other. On a five-bolt pattern, measure from the back of a hole to the center of the second hole. If you're building a trailer, try to match up the bolt pattern with that of the tow vehicle. In most cases, an existing hub can be swapped for one of a different pattern.

Wheel Alignment: It's just as important on a trailer as it is on an automobile. Misalignment can cause unequal load distribution, handling problems, and excessive tire wear. Measurements should be taken from the center of the coupler back to each side of the axle ends. If they're not equal on both sides, it's time to find out why. The problem could be a bent axle, broken spring, improperly located spring hanger, or even a bent frame or tongue assembly.

Just for fun, to give you some idea of what things weigh that you may carry, here are the approximate weights of some common materials:

Water 8.3 lb/gal
Sand 100 lb/cu ft or
2,700 lb/cu yd
Concrete 140 to 150 lb/cu ft
Cement 94 lb/bag
Brick 6 lb
Concrete block 22 to 44 lb
Wood, green live oak 6,500 lb/cord
Wood, dry pine 2,300 lb/cord


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