steep slopes

Working steep slopes with excavators see photo 6

Excavators were not designed specifically for forest use. They are designed for civil work mainly as a digging machine. For the Forest Industry they are modified, guarded and generally have to endure abuse of design to the maximum limits.

Slopes less than 40%

Normally slopes are worked up and down staying at right angles to the contour. Final drives of the excavator are positioned down the hill to the lowest point of the excavator. Working parallel to the contour can be done but is generally avoided due to the increased "instability" and "excessive" ground pressure on the lower track. "Footing" and Stability is critical. Hard dry ground provides easier access for machines but can limit ease of cultivation. The optimum window for plantation ground preparation is concurrent with the removal of the felled trees.

Slopes greater than 40% see photo 16

Working slopes greater than 40% is a questionable "safety" issue. Never exceed manufacturers recommendations or safety regulations. When working towards the limit of any machine safety become paramount. Good operators are hard to find.

When working slopes over 40% a decrease in productivity can be expected. Distance between spots increases with slope allowance. If on flat ground, the target spacing was a row of 6 spots wide, then on steeper slopes this mathematically is reduced to a row 5 spots wide that can be reached with a 20 Tonne excavator.

Furthermore stability on steep slopes decreases and mechanically you may only be able to reach 4 spots wide. To get the same number of hectares/acres done you must travel over the site more often. In addition the excavator may lack the track power and may have to be pulled hydraulically by the mechanical arm up the slope. This again requires more time.

Selecting work zones

Operators generally will selective more uniform zones of the cut over areas of uneven terrain. This will form a wedge shaped mosaic of different areas worked allowing refueling and operability ease.

On sever slopes, travelling downhill may be the only option while preparing spots behind the machine. Occasionally the excavator may have to travel while not preparing spots along a road or trail back to the top of the hill to recommence treatment. This method is often referred to as "dead heading" and should be avoided whenever possible. Often the designing of work zones will allow working down the steepest slope then working a more modest slope, then working back up a modest slope back to the point of commencement. Careful selection of work zones and long runs for the excavator greatly increases productivity.

The steeper the slope the faster the VH Mulcher works

Less time per spot is required to make a terrace on slopes when gravity works in your favor. Centrifugal action with rotation rapidly builds a planting spot to the down side when the VH Mulcher is used vertically with up and down motion.

Working steep slopes with the Timbco (and similar) Feller Bunchers

The main difference between the Timbco and excavators is that its performance is superior on slopes greater than 40%. see photo 1 and 16

Advantages:

1. increased engine horsepower, track power and stability

2. increased ground clearance and hydraulic supply

3. increased traction and operator performance (leveling cab)

4. no tail swing or counter weight

5. purpose built for logging industry

6. increases slope operability range (over excavators) by 15%

7. can work both up and down slopes

Disadvantages:

1. availability: machines are rare and usually busy in harvesting activities

2. higher purchase cost: nearly double that of an excavator

3. market: the forest harvesting market is much larger than the planting spot preparation market and encouraging new investment is difficult.

4. higher hourly rate: machines in high demand can and do charge more; excavator planting spot preparation is already the most expensive treatment and the Timbcos can add to this; as availability increases this situation will change and the TImbco and similar machines should be more effective on slopes in excess of 40%.