According to Fig. 4, of the 86 National Assembly on rocky routes 55 (ie 64%) were in direct disruption athletes in the climbs. Now it is a major cause of fatalities on the rocks, which, however, could not be, if at the time of disruption of normal insurance is reset by the second in the bunch.
How high up with the output of the first belay safe? What burden falls on stripping the athletes, rope and belay pitons? What loads are allowed? How much rope etched with fear at stall? Unfortunately, in the national mountaineering literature on these important questions are not fully answered.
Given all of the above, in the first place, we calculated the allowable loads for domestic rope diameter of 10 mm, the most widely used. In the calculations the following assumptions:
1. Inhibition of human neglect of air, as the fall tore the maximum linear speed in most cases does not exceed 10-15 m / sec.
2. The rope is loaded evenly and does not work on a cut.
3. This refers to the new rope, and mechanical properties is shown in Fig. 8, a.
4. Estimated weight of the man — 80 kg.
5. Fall of the first in the bundle is in a direction close to the vertical.
6. Load distribution rope match worst case rigidly fixing the ropes without etching (Fig. 9). Deformation plot 0-1 ignored.
7. In the calculations assume the characteristics of the deformation of the human body in the gazebo and chest harness, as shown in Fig. 8b (R people.).
The deformation of the rope,% -? L (%) = (? L (m) / L) 100,
where? L (m) — deformation of the rope, m;
L — length of rope from the last insurance to disrupt, m
The work done by the body in free fall in kgm —
E = MH,
where m — a person's weight (80 kg);
H is the depth of the fall rip, m adopted under N = 2L.
The sequence of calculations
1. Knowing the properties of the rope P = f [? L (%)], we construct the mechanical properties of the rope P = f [? L (m)] for L = 1, 2, 3, 4, 5 m (P — pull on the rope, kg) .
2. Adding graph P = f [? L (m)] and Rchel. = [? L (m)], we obtain the mechanical characteristics of the entire human safety chain with L = 1, 2, 3, 4, 5 m (Fig. 10).
3. According to the P … P creates a function Q … Q. where Q i is the area between the horizontal line coordinates [? L (m)] and P i curve for any value of L (Q-work done on the brake rope incident athlete kgm).
4. When m = 80 kg calculate the value of E for each L.
5. Equating to £ i Q i, we find the maximum load on the schedule on the rope and tore (points on the curve AB, Fig. 10).
6. For clarity, the curve P ab = f (? L) onto a separate graph (Fig. 11, a) as a function of L.
According to Fig. 11, and we see that with a rigid static insurance even at 1 = 2 m rope load exceeds the value of 1200 kg (TU.62.3931-76).
For comparison, the calculation is repeated for a foreign type Edelrid rope diameter of 11 mm, the characteristic of which is shown in Fig. 8.
For her, the curve of maximum loads (Fig. 11, b) does not exceed 1200-1250 kg for all values, due to significantly better elastic properties of the rope, and, hence, more gentle deceleration tear when the fall. If we consider that the rope Edelrid has the load capacity for technical reasons than 2000 kg, it is the strength does not limit the climber in the rocks under all conditions of failure.
However, security is not ensured if interrupted by only one rope. Equally important are all the other links in the safety chain of man: the strength of the upper hook and the first physical ability to withstand the pressure (pv (a-b)).
Conducted in 1978-1979. Test standard domestic hooks mild steel showed the following results (Table 3).
Fig. 11. Stress on the upper hook (NQR), rope (Hs) and fear (ASTRA), depending on the value of / at a rigid insurance for domestic rope (a) and for the rope "Edelrid" (b)
In Fig. 12 shows the operation of the hook at the top fall. P1 — the force on the rope and fell through, P2 — braking power, which falls on fear. When using native rope diameter of 10 mm at an angle a = 180 °, we have P2 = 0.5 P1. Then on the upper hook has load of Pcr = 1.5 P1. In Fig. 11 the curves of the maximum upper hook for domestic ropes and rope type Edelrid. On these curves shaded area shows the load, which is digging the biggest hooks of mild steel.
This shows that with hard insurance without etching the weakest link in the safety chain specifications are hooks.
Practice climbing fully confirms this. Thus, during the study period of 25 failures, when both worked hooks and rope, in 23 cases escaped 05.01 hooks (consecutively) and only 2 — to break the rope.
The last link in the safety chain — he ripped off. If it is fastened to a rope chest belt, the maximum load that it can survive without serious consequences if interrupted, does not exceed 250 — 350 kg. When using the pectoral girdle, interlocked with a gazebo from durable nylon belt width 50 — 60 mm, the maximum load is increased to 800 — 1000 kg, which is proved by the tests on the collection of security in 1979 When the normal load of parachute systems for the person sitting in the same arbor exceeds 1000 kg.
Thus, at the rigid insurance without dressing (scheme breakdown — in Fig. 9) we have the following limitations of the hardware and the insurance of the person:
1. The weakest link are the hooks, limiting safe ascent of the first bundle to L <1 m
2. When L = 2 m efforts to rope exceeds 1300 kg, which is most likely to entail digging hooks, and in some cases — breaking rope. In the same case load frustrate reach their limit values, 1000-1300 lbs.
3. When L = 3,5 m almost there is no guarantee a successful outcome of failure, as the dynamic forces on the rope increases to 1600-2100 kg, and the top hook — significantly more than 2000 kg.
4. When working with a rope type Edelrid relatively safe way up the conditions of tear-out hooks increases to L = 1,5-2 m very same rope strength does not limit the athlete.
When the first was held in conjunction the first intermediate coupling, the reliability of its hold on stripping increases. Scheme breakdown is shown in Fig. 13. We illustrate this case, when the friction of rope on the rock, as in the previous example, is missing. Let the distance between the hooks 1 and 2 (see Figure 13.) Is 2 m, and the failure occurred at L = 2 m after the hook 2. Insurance tough. Then the cushioning effect of rope is made up of its deformation in the area under a force 2.3 PB and the area under a force 2.1 0.5 PB. As a result, the maximum force on the rope is reduced.
For this example (the length of the site is 1.2 m 2), the load on the rope and hooks is reduced by 20-25%, but safe way of growing up to 1-1.5 m If the rope on the section 2.1 rubs against the rock This advantage is reduced.
Hence the following general conclusions.
1. In the case of a rigid (no dressing) insurance existing facilities (the rope and hooks) can not ensure the safety of the athlete fall.
2. Avoid tear-out hammered hooks or broken cords can only rope in the etching time of failure.
What should be the dressing? Given the above, it is easy to understand that the maximum force etching is chosen from reliable operation of the weakest link of the safety chain ripped off, ie hooks. According to Fig. 11 and Table. 4, the force on the hook should not be more than 450 kg. Then taking into account the distribution of forces on the rifle (see Fig. 12) PB <300 kg, and the force of the belayer etching P2 <150 kg. Diagram of the rope in this limiting case, the output of the first bundle of 5 m above the last hook is shown in Fig. 14 (PB-mechanical properties of the rope 5 m with the strain of the human body (RF); Q5 — braking energy to disrupt the rope equal to the area of the shaded surface OABV, kgm).
The work force of gravity when falling runaway depth H = 2L = 10 m is expressed as E5 = m * N = 80X10 == 800 kgm. Equating to Q5 E5 find deformation rope? L / (m) = 0.85 m, the length of dressing? Ltr = 2.25 m and the coefficient of dressing:
Repeating the calculation for different etching efforts rope (Rv.tr), we obtain the dependence of CTE Rv.tr shown in Fig. 15. Curve 3 shows at L = 1 m, the deformation trim and body comparable to the deformation of the rope. Curve 2 corresponds to L = 2 m 1 is a curve for the case L> 2, when the effect of deformation of the human body in the overall safety chain effect is negligible.
Experimental check showed very good agreement between the calculated and experimental loads.
When CTE> 0.45 force to rip and rope will be less than 300 kg, but the length of dressing (? Ltr), and hence the actual fall of man on the rocks will be more, which is always desirable. Therefore, the optimal etching zone lies within:
0.45 <CTE <0.7
with 300 kg> Rv.tr> 200 kg,
150 kg> P2> 100 kg,
where P2 — Load fear (second in the bundle);
Rv.tr — the load on the rope and lead (foiled). It must be remembered that the number of intermediate friction rope hooks and loops in carbines strongly increases and to maintain the optimal values of CTE and Rv.tr have to lower pressure (P2) from the belayer.
In practice, it is difficult to take into account, so that, in general, failure insuring better not to target a specific force retention (P2), and the required rate of etching (CTE). Knowing her, not seeking an experienced athlete instantly caught in full force at the end of a safety rope fall. His first effort does not exceed 10-30 kg, and only when the rope begins etches a carbine, it brakes have with great effort. Mastering this technique requires a lot of practical training at the belay stand.
However, the whole complex skill becomes useless if the lead in the group applies the brakes automatically tuned to the dressing rope under a force of 250-300 kg. Stock rope for etching is stored in a pocket or on the body of the first bunch.
Construction of such brakes are shown in Fig. 16 (call them brakes 1st kind).
Brakes and Abalakova Kashevnik known for several years and passed a series of tests in practice. Adapting Saratovkin appeared only in 1978 Fig. 16 shows how to lay the main rope rings. Every two rings are held together by conventional cotton herringbone tape in two turns. By pulling the main rope breaking force herringbone tape is 200 — 220 kg. When the snatch rope rings tear tape series and the main rope, straightening of the coils is extended, so the dynamic damping the spurt. Sweety Saratovkin meter device provides when straightening 4m additional pickling ropes, allowing safely go up to 6-8 m plumb Disruption will not disrupt the load of more than 250 kg, and a hook-a 370-400 kg, which is quite acceptable.
Another problem solve brake 2nd kind (Fig. 17). It was previously shown that the failure of one interim and hook on fear comes the greatest burden, which at different CTE can range from 40 to 300 kg. Such efforts to disrupt the belayer places pressed to the first hook, and he may lose control of the rope.
To facilitate the work of fear and applies the brakes of the 2nd kind, which redistribute the load with fear at first a safety hook. In this case, the man himself fall braking 10 — 40 kg (see Fig. 17, a, b, c).
In case of fixing the brakes of the 2nd kind on the rib trim insuring its direction a safety loop should coincide with the direction of the expected impact force (see Fig. 17 g). The figure shows the most reliable system of insurance of 3 hooks (or projections). In particular, less preferred, and insurance cases loop lanyard can be attached to one hook (projection). He must be absolutely reliable.
Brakes 2nd kind simplify the work of fear, but they should be used with caution and only after insuring accumulation of practical experience with them on a training stand. Indeed, if this method of Fear will keep the rope firmly 60-100 kg (which is available for the average person, and in a moment of danger), then the puck Shtihta load increases up to 300-500 kg and a top hook — 600-1500 kg , which will inevitably lead to his snatching.
The same happens if the belayer holds the rope through the washer Shtihta UIAA or node with a normal force of 10-40 kg, but the lead in combination, for various reasons, could not raspolozhit rope in a straight line, and it goes through the excesses of the rocks (Fig. 18a ) or winds between 3-4 hooks (Fig. 18b), that is working with a much larger friction. So inexperienced or emotionally unstable athlete prone to feverish fastening ropes at breakdown, the brakes of the 2nd kind is better not to use it.