The Essentials Of Maintaining Mechanical Sweepers

Ideally suited for sweeping construction debris and granular materials like millings or gravel, mechanical street sweepers are built to tackle some of the toughest road conditions. These sweepers use a mechanical device to move the street debris from the brooms into the hopper. This method of debris conveyance is what defines a mechanical street sweeper.

Currently, Elgin Sweeper uses a chain and squeegee or a conveyor belt and rollers to move the street debris from the brooms into the hopper. For example, the three-wheeled Pelican NP and NS models feature a conveyor belt and roller configuration. The conveyor belt and roller design can be configured in other Elgin Sweeper “mechanical” sweeper lines, including the chassis-mounted Eagle, Broom Bear and Road Wizard sweeper. The standard build for the Broom Bear, Road Wizard and Broom Badger (a new product recently introduced by Elgin Sweeper) is the chain and squeegee conveyor/elevator systems, but both the Broom Bear and Road Wizard sweepers can also be ordered with the belt and roller configuration to suit customer preferences.

Regardless of the conveyor configuration, there are two key areas of maintenance on a mechanical sweeper—the conveyor system and the brooms. The maintenance requirements for mechanical sweepers are greater than those for regenerative air and pure vacuum sweepers, since mechanical sweepers contain more moving parts requiring routine replacement.

Conveyor System

Prior to performing any adjustments on a mechanical sweeper’s conveyor system, all of the safety stands must be installed and the manufacturer’s recommended safety practices should be carefully followed. Please consult your sweeper’s operator and service manuals for location and proper use of safety equipment associated with your sweeper.

With the launch of the current model Pelican sweeper line in 2006, Elgin Sweeper incorporated design changes to the conveyor belt system on its mechanical sweepers. The previous belt design came in two options, single- and double-ply. Each belt option used a flat cleat and small ribs to capture the street debris being swept and flicked up onto the conveyor belt. The single-ply belt required more frequent adjustments to keep it “trained” and centered in the conveyor frame. The double-ply belt was more reliable once “trained” and would maintain its adjustment for a longer period.

The newly redesigned “Modified Chevron” changed the flat cleats to a modified “V,” or chevron, design. The modified cleat angles the outer 12 to 14 inches of the cleat to move the debris to the center of the belt as it travels up the conveyor frame. Consequently, more debris is moved into the center of the hopper for a more even distribution of the dirt in the hopper. In addition to the modified chevron cleats, more pronounced ribbing between the cleats was introduced to capture the finer dirt. This raised ribbing prevents rollover of the large debris.

The more pronounced ribs capture and hold the finer debris in place, making the whole debris conveyance more efficient. The result is a cleaner sweep, with less spillage. The rubber composition is heavier and thicker with improved textile reinforcement internally to reduce stretching. This results in fewer adjustments and truer belt tracking once trained properly. The back side of the belt was also improved. The belt back is now textured or dimpled, which eliminates sticking once the conveyor system has been washed down at the end of the sweep shift.

Belt Training

Belt training is an important adjustment for belt longevity. Allowing the belt to track to one side or the other will promote wear of the conveyor frame and can potentially cause the belt to rip or jam. Most conveyor systems have some sort of adjustment, usually at the top, where tensioning of the belt and tracking adjustments are made.

The first adjustment for belts is to establish the proper tension. If the belt is allowed to sag too much, the cleats will make contact with—in the case of the Pelican P/S sweeper—the cross member in the hopper home. If the condition is allowed to go uncorrected, the cross member will sustain wear. Left unchecked, holes will develop in the metal. The proper tension will allow the belt to travel with no contact to components in the hopper home. If the belt is tensioned too tight, the bearings that support the rollers will experience accelerated wear and, consequently, failure.

Once the correct tension has been established, the belt tracking will be the second adjustment. To get the belt to track in the center of the conveyor frame, it must be lowered into the operating position, with the sweeper pulled forward about 10 feet to allow all the components—such as dirt deflectors and dirt shoes—to assume their operating positions. The belt must be observed as it travels. If the belt starts moving to the right or left, the appropriate tensioner should be tightened.

Elgin Sweeper’s top roller uses two spiral-wound bands that cause the belt to track towards the side with the least amount of tension. When the belt starts moving in one direction, a tensioning bolt should be chosen and adjusted accordingly. If the belt is moving to the street side (left facing the front of the sweeper) the tensioning bolts on the street side need to be tightened one half-turn, observe the belt for movement. If the migration is slowed but continues to move to the street side, it should be tightened another quarter-turn, and belt movement observed again. This adjustment procedure is somewhat of a trial-and-error process, but after some practice, most technicians can have it running true in short order.

If the belt starts to move to the curb (right facing the sweeper) the adjusting nut on the left side should be backed off about half of the one quarter-turn. If the belt appears to be stationary, applying a contrasting paint from a spray can to both sides will highlight the edge of the belt and roller. If the belt continues to move, the contrasting paint will reveal the movement more easily than watching the black belt and the end of the roller.

If the belt will not train, a thorough inspection of the conveyor components must be performed. Worn bearings, broken rollers or seized components will have an adverse effect on belt training.

Chain and Squeegee Elevator Assembly

The chain and squeegee design has been used on the Road Wizard and Broom Bear sweepers for many years. This design uses rubber flights sandwiched between two strips of metal, one used to mount the assembly to the chains and the other used to secure the flights to the squeegee assembly. As with the conveyor belts, the chains need to be observed and adjusted when the chain sag allows the strands to rub together (extreme wear) or simply getting close enough to warrant an adjustment. Elgin Sweeper’s chain and squeegee-type elevator system uses two hydraulic grease cylinders to maintain and establish proper chain tension. A special grease zerk adapter is placed on the end of the grease cylinder.

Using a hand grease gun, two pumps should be applied per side, alternating left and right to expand the cylinders. The chain strands will become more taught. The proper sag is 3 5/8 inches (9.22 cm) between the strands. Using a high pressure shop grease gun is not recommended as it commonly results in over-tensioning of the chains. Over-tensioning can result in bearing and/or shaft failures.

When making chain adjustments, the sag should be decreased (chains tightened) by no more than 1 inch (2.5 cm) at a time, alternating left and right until the proper sag of 3 5/8 inches (9.22 cm) is achieved. The elevator assembly must not be allowed to operate with the shafts out of parallel, as this will hasten sprocket and cog wear. As the chains stretch, taking a full link out and adding a half link may be necessary.

With the installation of the half link, the adjustment procedure starts at a renewed distance. Once the half link has been added and the adjusting cylinders have once again reached the end of their travel, the chains will require placement.

The second adjustment will be the introduction of the flight into the lower elevator pan. The flight must make contact with the lower radius of the pan in a gradual, easy landing. The lower bearing that supports the lower shaft has a radius cast into the housing that accomplishes this adjustment. The clearance of the flight will be adjusted to allow the flight assembly to make gradual contact (0.006 inch or 1.5 mm) with the elevator pan as it comes over the lower roller shaft.

The third adjustment is for the flight as it leaves the upper elevator pan. This can be compared to an airplane leaving a runway. The rubber flight has a clearance of .006 or 1.5 mm, allowing it to leave the pan without dropping off the edge. Nice and smooth at both ends of the elevator assembly. The upper shaft adjustment is made at the bearing mounted in the elevator housing. The attaching hardware should be loosened using a long pry bar to lift the upper shaft until the specification is met.

With all these adjustments made properly, the rubber flights will travel up the elevator pans in a vertical relation to the pan itself. If the rubber flight is allowed to ascend at an angle, the debris escapes and wear is accelerated on both components.

The Broom Badger sweeper uses a chain and squeegee elevator assembly similar to the Road Wizard and the Broom Bear; however, the adjustments are slightly different. The chain tension will be measured from the elevator pan to the top of the upper chain strand. The recommended tension is set at a measurement of 12 ¼ to 12 ½ inches. This measurement is established using two push bolts at the top shaft. The jam nut should be loosened and the push bolt screwed in until the measurement is attained. The jam nuts should be retightened to ensure the adjustment does not change during operation. For flight introduction, the lower elevator pan is set at 1/8 of an inch. The important thing is that the flights must contact smoothly. Repeated flight contact that is hard and rough will damage the lower pan over a period of time. The upper dimension is the same as the lower adjustment.

Broom Contact Patterns

The other important adjustments are the broom contact patterns. When set properly, broom contact patterns will increase broom life dramatically and ensure a clean, superior sweep, without any debris left behind. The side broom area of contact will display a crescent pattern on the sweeping surface that will remove debris from the curb and bring it into the path of the pickup or main broom. This is referred to as the 3 o’clock and 10 o’clock positions on the curb side.

Coning

The main broom contact pattern will exhibit a pattern that is 4 to 6 inches wide from the right side to the left side. Any variations from that would indicate a coning issue. For example, after a broom pattern was performed, if the right side measured 4 inches and the left side measured 6 inches, the main broom would be coning to the heavy, or left, side. A coned broom cannot be recovered, so replacement is recommended.

Observing the main broom’s wear closely after repairs will indicate whether the coning issue has been resolved.

The Broom Badger uses a chain and spring broom balance and float system to develop the main broom contact pattern. This procedure suspends the main broom from two chains and springs at each end of the broom. The attachment point for the chain above the broom uses a vertical support with a series of horizontal slots which the chain hooks into to establish the correct broom contact pattern and, as a result, the correct down pressure. Slot position and spring coil determines the balance of the broom. Close monitoring ensures the adjustment will extend broom life without coning and also provides the best possible sweep. Other Elgin Sweeper products use a computer-controlled hydraulic float system that allows operators to precisely control main broom down pressure from inside the cab.

Broom Down Pressure

Broom down pressure is a key component of contact patterns. Too much down pressure on the side brooms will extend the termination points of the crescents, flaying out the bristles and accelerating bristle wear. This is true for main brooms as well as side brooms. With the main broom, excessive down pressures will widen the contact pattern 8 to 10 inches in extreme cases.

Excessive down pressure effectively lays the bristle over, causing the bristle to mop the debris into the pavement, wearing the bristle at an acute angle and shortening broom life. This acute angle can be identified easily. A uniform water mark higher than 1 ½ to 2 ½ inches up the side of the bristle indicates too much down pressure.

Correct main broom down pressures allow the tips of the bristle to “flick” the debris up onto the elevator/conveyor. Bristle tip contact with the appropriate down pressure will extend the life of the broom.

Keep It Clean

As with the conveyor belts, chains and squeegees should be washed with the sweeper at the end of every shift. Daily cleaning is an integral part of any sweeper’s care and longevity. A clean sweeper is easier to work on and failures are easier to see when service is performed each day.

For more information on mechanical street sweepers available from Elgin Sweeper, please contact your local Elgin Sweeper dealer, or visit www.elginsweeper.com to find a dealer near you.

Story by Jimmy Broyles, CBT supervisor ESG University, Elgin Sweeper

If you have an idea or advice for our readers, please email Jennifer Taylor at jennifer@nasweeper.com

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