![Example of a Pole Spear [2]](https://www.researchgate.net/profile/Jesse-Spiller/publication/349350884/figure/fig1/AS:991992850952195@1613520934689/Example-of-a-Pole-Spear-2_Q320.jpg)
![An Unloaded Conventional Speargun [3]](https://www.researchgate.net/profile/Jesse-Spiller/publication/349350884/figure/fig2/AS:991992850956289@1613520934775/An-Unloaded-Conventional-Speargun-3_Q320.jpg)
![A Prong Tip [4]](https://www.researchgate.net/profile/Jesse-Spiller/publication/349350884/figure/fig3/AS:991992850952197@1613520934805/A-Prong-Tip-4_Q320.jpg)
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Modelling Speargun Dynamics
Abstract and Figures
This investigation outlines the current technical state of spearguns and key
performance concepts. Testing of natural rubber was conducted to determine
dissipation losses given an assumed 30 minute load case. This data was then
used to develop a function that determines the potential energy stored by 14, 16,
17 or 18mm natural rubber bands given any speargun geometry.
Momentum and energy balances were used to derive equations of motion for the
dynamic behaviour of conventional, roller and inverted spearguns. The system
energy from the rubber function and component masses calculated from
speargun geometry are used to solve for component velocities.
Shaft velocity at various ranges was then calculated using an estimated drag
coefficient and penetration at these ranges was calculated using an estimated
fish tissue cavity strength. COVID-19 prevented testing to empirically determine
these coefficients and increase simulator accuracy; Part 11 outlines the testing
still outstanding.
Shaft buckling and bending were compared and discussed to a limited extent.
Parts 10 & 11 summarise the findings and performance trends uncovered by the
simulation and demonstrated how the simulator could be used to improve
speargun design. Part 12 outlines three areas of research and one survey that
would further expand understanding of speargun dynamics and simulator
capability.
The simulator was published as a website running Python 3; it can be accessed
and used by anyone with a web browser at no cost. Work to complete testing and
evaluate simulator accuracy is ongoing.
Figures - uploaded by Jesse Spiller
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Natural rubbers have extraordinary physical properties, typically the ability to crystallize
under tension. Especially, they exhibit a high fatigue resistance. Furthermore,
strain-induced crystallization (SIC) is a high thermo-sensitive phenomenon. Better
understanding how SIC reinforces fatigue life and how temperature affects this property
is therefore a key point to improve the durability of rubbers. The present study
investigates temperature effects on the fatigue life reinforcement due to SIC for nonrelaxing
loadings. After a brief state of the art that highlights a lack of experimental
results in this field, a fatigue test campaign has been defined and was carried out.
Results obtained at 23°C were first described at the macroscopic scale. Both damage
modes and number of cycles at crack initiation were mapped in the Haigh diagram.
Fatigue damage mechanisms were then investigated at the microscopic scale, where
the signature of SIC reinforcement in the crack growth mechanisms has been identified.
Typically, fatigue striations,wrenchings and cones peopled the fracture surfaces
obtained under non-relaxing loading conditions. At 90°C, fatigue life reinforcement
was still observed. It is lower than at 23°C. Only one damage mode was observed
at the macroscopic scale. At the microscopic scale, fracture surfaces looked like the
ones of non-crystallizable rubbers. At 110°C, the fatigue life reinforcement totally
disappeared.
Research on rubber fatigue properties is of great significance for improving the durability of rubber products. Natural rubber is widely used in rubber products, it is very important to study the effect of temperature on its fatigue properties. Here, tensile fatigue tests of natural rubber have been carried out under different temperatures and strains for studying the influence of temperature and strain on the fatigue life. Results indicate that fatigue life decreases when test temperature increases, and it decreases obviously when temperature is higher than 75 °C; with increasement of temperature, tensile strength decreases, and the elongation at break increases; the fatigue life decreases with the increasement of strain, and the decreasement of fatigue life is more remarkable under small strain.
This project analysed the factors that affect the performance of spearguns. Experimental and theoretical analytic methods were used to quantify the performance of speargun design. This data was then used to conclude on and justify recommendations to make a more suitable/efficient speargun design.
A slow motion video analysis formed part of an experimental examination of a benchmarked speargun design. This analysis measured the initial velocity of the spear and showed other factors which affect performance.
The factors which had the largest bearing on the performance of the speargun were the stiffness of the barrel and the power of the rubber bands. These factors were evaluated and used to construct a theoretical model using engineering principles. This provided a basis to compare and create alternative designs.
From this study it was found that the theoretical model created was suitable for predicting how a speargun would perform. This model was then used to show that an improved barrel profile featuring integrated rails would make the barrel stiffer, and that by using a roller power system, the barrel flex could be reduced. This system also had the potential for delivering more energy to the spear, resulting in a greater initial velocity. Because of this increased power, the length of the speargun could be reduced without compromising on range.
Roller guns provide more opportunities for adjustment than traditional spearguns and, because of this versatility, a single model of a roller speargun can be adjusted to suit the power requirements and strength of the individual who uses it. The results of this study also show the correct setup of this system in order to achieve the maximum performance capability.
Fatigue properties of filled natural rubber in seawater environment are investigated by uniaxial fatigue and crack propagation experiments, and the damage is analyzed by scanning electron microscopy. The behavior under relaxing and non-relaxing loading conditions is studied and the results are compared to those obtained in air environment. For relaxing loading conditions, fatigue behavior is the same in both environments. Under non-relaxing conditions at large strain levels, for which the influence of strain-induced crystallization is important, fatigue life is longer in seawater. Such behavior could be explained by increased internal temperatures of specimens tested in air due to lower heat conductivity of air as compared to seawater. Such conclusion is also supported by the damage mechanisms observed under non-relaxing loading conditions.
Strain induced crystallization (SIC) of natural rubber (NR) has been studied in a large range of strain rate (from 5.6 Â 10 À5 s À1 to 2.8 Â 10 1 s À1) and temperature (from À40 °C to 80 °C) combining mechanical and thermal analysis. Both methods are used to extend the study of SIC from slow strain rates – performed with in situ wide angle X-rays scattering (WAXS) – to high strain rates. Whatever the temperature tested, the stretching ratio at crystallization onset (k c) increases when the strain rate increases. This strain rate effect is strong at low tem-perature (close to T g) and weak at high temperature (much higher than T g). A theoretical approach derived from the Hoffman–Lauritzen equation has been developed and provides a good qualitative description of the experimental results. At low temperature, the strong increase of k c with strain rate is explained by a too long diffusion time compared to the exper-imental time. At high temperature, SIC kinetics is rather controlled by the nucleation barrier which mainly depends on the strain energy. When the stretching ratio increases, this nucle-ation barrier strongly decreases, allowing crystallization even for short experimental time.
For competitors in the shooting sports, gun recoil can affect performance and create discomfort. An objective method of measuring felt recoil forces would be useful to evaluate methods of recoil reduction. An experimental test apparatus was developed to measure recoil forces of sporting rifles and shotguns. No modifications to the firearms themselves were necessary to make the measurements. Through both inertial and dissipative restraint mechanisms, the apparatus reproduced gun movement that was representative of that experienced by a particular shooter. This should result in measured recoil forces similar to those experienced by the shooter. The apparatus measures the horizontal shoulder force and the vertical force component exerted at the stock comb.The recoil event was found to be quite short, having duration on the order of 10 ms. Peak recoil forces for common shotgun target loads were in the range of 1.6–2.2 kN (360–494 lbf). The apparatus was found sensitive enough to measure recoil force differences among different factory loaded ammunition, and differences in recoil force imparted by different firearms shooting the same ammunition.The apparatus should prove useful for quantifying differences in felt recoil as affected by ammunition type, gunstock geometry, barrel porting, recoil reduction devices, and gun weight, among other factors.
The advantages of using a hierarchical analysis approach to calculate the buckling load of an axially compressed composite cylindrical shell is demonstrated using an example taken from a recent experimental program. The Delft Interactive Shell DEsign COde (DISDECO) shell design code is used for this hierarchical analysis approach to provide an accurate prediction of the critical buckling load of the actual shell structure. DISDECO includes the influence of the boundary conditions, initial geometric imperfections, the effects of stiffener and load eccentricities, and the effects of prebuckling deformations caused by edge constraints in the analysis. It is shown that the use of DISDECO makes it relatively simple to proceed step by step from simple to more complex models and solution procedures. As a final step in the hierarchical analysis approach, the critical buckling load and the estimated imperfection sensitivity of the shell are verified by conducting an analysis of a large finite element model with one of the current generation two-dimensional shell analysis codes with advanced capabilities needed to represent both geometric and material nonlinearities.
- Ebay
Ebay. Pole Spear Image. Available at: https://www.ebay.co.uk/itm/JBL-Shaka-Carbon-Fiber-Travel-Pole-Spear-/162905318973 (Accessed: 20
July 2020)
3.
Nootica.
Speargun
Image.
Available
at:
https://www.nootica.com/speargun-riffe-mahogany-competitor-3-130-cm.html (Accessed: 20 June 2020)