WORKING DIFFICULT MATERIALS

Special operating techniques are required when performing scraper operations in difficult materials, such as wet or sticky material, loose sand or gravel, and large objects.

Wet and Sticky Materials

When unloading wet and sticky material, do not try to spread the material too thin. Always keep the bowl high enough to allow the material to flow back under the scraper. Open the apron wide enough to allow an easy flow out of the bowl, Bring the ejector forward with short, snappy movements of the ejector control lever to shake the material loose from it. Allow a little time between each ejector movement to avoid compacting the material between the apron and ejector. In some cases, shifting the ejector between forward and reverse gives the material that has been brought forward a chance to fall out the apron opening.

NOTE: When the material is spread too thin or the bowl is too low, the material will pack against the scraper cutting edge inside the bowl and will not eject.

Loose Sand and Gravel

Sand is a free-flowing material that tends to float ahead of the scraper cutting edges when being loaded. To obtain a heap scraper load when loading and to avoid being bogged down by the sand, use the technique called pump loading. To pump load, enter the cut with the apron open about 3 feet and the scraper cutting edges lowered into the sand. Continue through the cut until the engine(s) starts to lug down. Then lower the apron into the sand that has piled up in front of the scraper cutting edges, and raise the bowl 2 or 3 inches at a time. Do not completely close the apron or drop the bowl so deep that the engine stalls. This pump loading technique will ordinarily allow the scraper to get a full load.

When spreading sand, always spread it as thin as possible, and keep the scraper moving in the fill. A thin spread allows better compaction and makes it easier to travel over the fall.

To obtain a full load when loading gravel, you may have to pump load as performed with sand. The apron may be hard to close due to stones getting caught between the apron and cutting edges. A technique used to avoid the stones is to backup a few inches with the blade still in the ground while closing the apron. This should force the stones out and allow the apron to close all the way.

Large Objects

Scrapers are not designed to dig or transport large objects; however, they may be used for this purpose when more suitable equipment is not available.

Approach the object with the apron and scraper bowl fully raised. When the object is too large to clear underneath the tractor, bring the tractor past the object until the drive wheels are a few inches beyond it. Pivot the tractor sharply towards the object to allow the tractor to bypass the object, and bring the cutting edge into position for loading (fig. 10-43).

When the tractor reaches its sharpest angle of the turn, bring the scraper cutting edges within a few inches of the object. Lower the bowl, apply down pressure, and ^{move forward.} When the cutting edge hooks underneath the object, lift the bowl while inching forward. When the object slips off the cutting edge, back up and try again. You may have to approach the object from a different direction to get a grip to load the object.

To shove the object around, keep the ejector in the full forward position. When the object is to be picked up and carried, place the ejector in the normal fullback position. To close the apron completely after the object

Figure 10-43.-Scraper maneuver to load large object.

has been loaded, scrape up a little dirt that will push the object back further into the bowl.

To unload the object, shift the ejector from forward to reverse several times to move the object around so it will fall out. After the object has been unloaded, turn the tractor sharply so the scraper clears the unloaded object.

NOTE: Use extreme care when handling large objects. Oversize objects, such as large rocks, can cause damage by denting, bending, or straining parts. Damage may also be done by accidental collision with large rocks during ordinary digging.