Silva Fennica

Fig. 1. The studied harwarder consisting of a Ponsse Buffalo Dual forwarder and the Moipu 300 F1 harwarder head. The harvesting of brushwood was based on the dual purpose machine system.

Fig. 2. JAK SP-180 spiral cutter was attached to the boom tip of wheeled Neuson 6503 WD mini-excavator. The clearing of brushwood was done with the spiral cutter in the study.

Table 1. The statistical characteristics of tree species specific regression models for height and DBH in which the stump diameter (x₁, x₂, x₃ and x₄ for the stump diameters of birch, spruce, pine and other broadleaves in respective order) is the independent variable.
Tree model	Dependent variable	R²	F-test		N	Term	Constant/Coefficient		t-test
			F-value	p			Estimate	Std. error	t-value	p
DBH	DBH_Birch	0.946	521.531	<0.001	31	Constant	–1.268	4.359	–0.291	0.773
						x₁	0.830	0.036	22.837	<0.001
	DBH_Spruce	0.936	824.357	<0.001	57	Constant	–5.009	2.404	–2.083	0.042
						x₂	0.897	0.031	28.712	<0.001
	DBH_Pine	0.965	2029.299	<0.001	75	Constant	–3.075	1.923	–1.599	0.114
						x₃	0.875	0.019	45.048	<0.001
	DBH_{Other broadleaf}	0.989	3342.685	<0.001	39	Constant	–5.847	1.289	–4.536	<0.001
						x₄	0.933	0.016	57.816	<0.001
Height of the tree	Height_Birch	0.764	97.260	<0.001	31	Constant	2.432	0.746	3.261	0.003
						x₁	0.061	0.006	9.862	<0.001
	Height_Spruce	0.827	263.788	<0.001	57	Constant	0.159	0.279	0.571	0.570
						x₂	0.061	0.004	16.242	<0.001
	Height_Pine	0.965	196.838	<0.001	75	Constant	2.083	0.324	14.030	<0.001
						x₃	0.046	0.003	6.419	<0.001
	Height_{Other broadleaf}	0.911	391.037	<0.001	39	Constant	1.751	0.253	19.775	<0.001
						x₄	0.063	0.003	6.922	<0.001

Table 2. Work elements with detailed definitions in harvesting roadside brushwood with the harwarder.
Work element	Definition of the work element
Moving between the working locations	Begins when the harwarder starts to move (wheels are turning) and ends when the harwarder stops moving to perform another activity at the working location, e.g. positioning to cut.
Positioning to cut	Begins when the boom starts to swing towards the first tree and ends when the empty harwarder head is resting on the tree before the felling cut at stump height begins. With tall trees (higher than 8 m), the harwarder head is first placed halfway along the tree to be felled.
Accumulating the felling	Begins when the felling cut starts (either at the stump height or halfway of the tree) and ends when the accumulated tree bunch starts moving to the load space of the harwarder. With tall trees the top is cut first, after which the harwarder head is moved vertically downward and the tree is cut again at the stump height. The number of trees in each harwarder head bunch is observed and recorded.
Loading	The harwarder loads directly felled trees to the load space of the harwarder. Begins when the accumulated tree bunch starts moving to the load space of the harwarder and ends when the empty harwarder head start positioning to cut, the load is full or harwarder starts to move to the next working location.
Driving loaded or unloaded	Driving with load begins when the brushwood is harvested from the time study plot (harwarder head is positioned for driving loaded and wheels are turning) and ends when the harwarder stops to begin unloading at the landing area. Driving unloaded begins when the load is empty, the harwarder head is positioned for driving unloaded and its wheels are turning. Driving unloaded ends when the harwarder stops at the working location and positioning to cut starts.
Sorting of trees placed in the load space of the harwarder	Sorting of trees placed in the load space of the harwarder before the final grip for unloading.
Unloading	Starts when the harwarder stops at the landing for unloading and ends when the load is empty and harwarder head is positioned for driving unloaded. The number of harwarder head loads during unloading is recorded.

Table 3. Work elements with detailed definitions in roadside brushwood clearing with the spiral cutter.
Work element	Definition of the work element
Continuous clearing of brushwood	The mini-excavator is driving forward at a steady pace, brushwood is fed continuously to the blades by rotating spirals, brushwood is cut down in a desirable direction (backwards) and the work is not interrupted
Slow down clearing of brushwood	The mini-excavator has to slow down the driving speed or stop because brushwood is cut down slowly, improperly or fell in an undesirable direction (towards mini-excavator). The clearing work is partly interrupted, but the spirals continue to rotate either forward or backwards

Table 4. Regression model statistics for harvesting with the harwarder (x₁ = number of harvested trees per hectare, x₂ = the average volume of the harvested trees (dm³), x₃ = grapple load size during loading (m³), x₄ = grapple load size during unloading (m³), x₅ = forwarding distance (m)).
Work phase model	Dependent variable	R²	F-test		N	Term	Constant/Coefficient		t-test
			F-value	p			Estimate	Std. error	t-value	p
Moving	T_Moving	0.881	576.779	<0.001	80	Constant	0.168	0.045	3.721	<0.001
						1/x₁	4351.5	181.2	24.016	<0.001
Cutting	T_Cutting	0.724	204.102	<0.001	80	Constant	–4.571	0.680	–6.719	<0.001
						ln(x₂)	3.400	0.238	14.286	<0.001
Loading	T_Loading	0.848	434.187	<0.001	80	Constant	–8.222	5.176	–1.588	0.116
						1/x₃	7.237	0.347	20.837	<0.001
Number of trees in the grapple	N_{Number of trees}	0.487	73.960	<0.001	80	Constant	1.163	0.411	2.830	0.006
						1/x₂	53.675	6.241	8.600	<0.001
Unloading	T_Unloading	0.203	19.919	<0.001	80	Constant	99.030	8.259	11.990	<0.001
						x₄	–140.211	31.416	–4.463	<0.001
Forwarding	T_Forwarding	0.900	757.519	<0.001	85	Constant	24.154	3.688	6.549	<0.001
						x₅	0.691	0.025	27.523	<0.001

Fig. 3. Average proportion of various working elements in the harwarder harvesting of roadside brushwood.

Fig. 4. The time consumption of moving between work locations as a function of trees harvested per ha in the harwarder harvesting of roadside brushwood.

Fig. 5. Time consumption of loading as a function of grapple load size in the harwarder harvesting of roadside brushwood.

Fig. 6. Time consumption of driving loaded and driving unloaded as a function of forwarding distance (m) in the harwarder harvesting of roadside brushwood.

Fig. 7. The harvesting productivity of roadside brushwood with the harwarder as a function of forwarding distance and average volume of harvested brushwood trees. The harwarder’s payload was 7.1 m³ and the number of harvested trees per ha was 6000.

Fig. 8. The clearing productivity of roadside brushwood with the harwarder as a function of forwarding distance and average volume of harvested brushwood trees. The harwarder’s payload was 7.1 m³ and the number of harvested trees per ha was 6000.

Fig. 9. The time study plot-wise clearing productivity (ha per PMh) of the JAK SP-180 spiral cutter as a function of average stump diameter of brushwood trees, mm.

Fig. 10. The clearing speed (m per s) and the max. brushwood stump diameter (mm) by the study plot of the JAK SP-180 spiral cutter.

Fig. 11. The time study plot-wise roadside brushwood clearing productivity (ha per PMh) of the JAK SP-180 spiral cutter as a function of stump density per ha.

Fig. 12. The time consumption (seconds per time study plot) of continuous clearing and slowed down clearing working elements in brushwood clearing and estimated brushwood height by the time study plots of JAK SP-180 spiral cutter.

Fig. 13. The time study plot-wise clearing productivity (ha per PMh) of the JAK SP-180 spiral cutter as a function of cross-sectional area of stump diameters (m² per ha) by the time study plot.