Payload Analysis Flashcards
Why use skylines?
- Helicopter logging very is expensive
In typical cable logging, what level of suspension is acceptable?
Partial suspension is the status quo unless you are in a situation where you have fish streams or water intakes that could be affected by the sediment that would be associated with skidding the logs.
In skyline systems, what is another name for the mainline?
The skid line
What are the 3 classes of skyline systems?
- Standing skylines with a static skyline. Can be single or multi span. Rarely used In Canada and can only pull uphill.
- Live skylines where the skyline can be raised and lowered. Common in Canada and require at least a 2 drum yarder but line length is variable.
- Running skylines such as a grapple yarder or highlead with a slack pulling carriage where the haulback doubles as a skyline as well as providing travel. Tension is controlled with interlocking drums. Also common in BC.
When would a multi span skyline be desired and what are the limitations?
Multi span are typically used where there are cross slope roadbuilding restrictions. They give a way to increase the spacing between required roads but cannot support as high of a payload as single span.
What are the 3 main carriage types? Give details
- Clamped: Carriage clamps onto skyline to prevent travel. This decreases the turn size but offers lateral Yarding potential. The dropline is controlled by a motorized winch in the carriage.
- Unclamped: Large carriages with very limited lateral Yarding ability but high turn size.
- Clamped with active mainline: Mainline reels carriage drum in and out. Treated as an Unclamped carriage when calculating tension deduction.
What are some typical features of clamping carriages?
Usually reserved for small carriages, small timber and multi span logging. Auxiliary power in from carriage raises load while carriage clamps onto skyline. Reduces turn size since the load is concentrated on a single point while clamped, but has lateral Yarding capability.
If a carriage is clamped with an active mainline, is it treated as a clamped or an Unclamped carriage when calculating tension deduction?
Treated as Unclamped since power is coming from mainline.
What 3 things control the maximum tension that a skyline can support?
Slope of span
Weight of cable
Sheave diameter
Where is a skyline most likely to break?
At the upper end of a sloping span due to the weight of the line. It usually breaks at the sheive due to the added tension as the cable flexes to travel around it.
Why do clamped carriages cause increased tension?
How does a skidding line decrease tension?
- Because when the carriage clamps to the skyline the entire load is supported by the skyline at a single point.
- When a skidding line is used, it shares some of the load
Why don’t we just use the 6% rule for skyline deflection?
- Safety margins are closer than in highlead systems
- Cable tensions are higher
- Chance of failure due to poor design is higher
- Skyline logging is expensive so if you can optimize turn size by manipulating deflection, you should.
