Auger Gearbox Service
Failure Analysis
There are some misconceptions regarding these gearboxes that result in incorrectly identifying the causes of failure.
The square cut ring on the impeller shaft is not really a seal. It is a wiper ring that has a tendency to pull down to the shaft when the shaft begins to turn. The bushing next to the ring really deflects most of the oil that is thrown towards that area. The loose fit provides a vent for the case (Figure 27). Occasionally a drop or two of oil will get between the bushing and ring. When the auger drive is disengaged, the ring will relax and that oil might drip into the auger housing. At this rate, the machine can be used for several years without any significant oil loss. The yearly oil level check is more than adequate to compensate for this.
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Figure 27 | ||
1. Wiper ring
If there is a significant amount of oil coming out of this area, it would indicate that the gearbox has been at a severe operating angle or the bushing is badly worn.
Oil on the bottom of the gearbox can result from a leak at any part of the case. As there is no internal pressure, any leaking oil runs down the side of the case and collects on the bottom until there is enough to drip off. The source of the oil leak oil can be difficult to see. Sprinkling some powder on the outside of the gearbox will usually show the oil trail. The type of powder used is not important. Just something that will stick to the oil.
When you open a gearbox that has had the gears fail, the remaining oil will likely appear as a small puddle of very thick grease in the bottom. Worm gears normally create a large amount of friction due to the sliding action. When something goes wrong, not enough oil, poor quality oil, a problem with the gears, or just a gear or bearing wearing out, the friction becomes abnormally high. The remaining oil is cooked down to a very thick residue. This can be the result of failures, not the cause.
GEARBOX ASSEMBLY
1.Use a wire brush or sandpaper to clean the auger shaft. A clean, smooth shaft will help avoid damage when installing new bushings and seals. Clean the old gasket material from the case mating surfaces (Figure 28).
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Figure 28 |
2.If new bushings are to be installed in the gear case halves, now is the time. Apply a thin coat of Loctite™ Blue #242 or equivalent to the OUTSIDE of the bushing and press in flush with the INSIDE of the case (Figure 29). This will allow space for the seal on the outside. Wipe up any Loctite™ that is visible. The Loctite™ must not get into the gear or seal area.
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Figure 29 |
1. Flush
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