International Conference KNOWLEDGE-BAED ORGANIZATION Vol. XXIII No 3 2017 METHOD FOR DETERMINATION OF THE PARAMETER OF A MACHINE GUN UPENION MOUNTED ON AN ARMOURED VEHICLE vilen PIRDONOV, vilen TEFANOV Vasil Levsi National Military University, Velio Tarnovo, Bulgaria saspironov@nvu.bg Abstract: The following report shows methos for etermination of the coefficients of stiffness an amping, for softening the vibrations, which ensue in an armoure vehicle s suspension from the shooting of a mounte machine-gun. The methos are base on a moel of the movement smoothness, in which is aitionally inclue the signal of the machine gun's recoil. Keywors: shooting, machine gun suspension, stiffness, amping 1. Introuction The process of shooting from armoure vehicles has a frequency character an uner certain conitions, it may cause resonance in the vehicle s suspension. For analysis of these processes in [1] is evelope a ynamical moel of the machine with seven egrees of freeom (DOF) figure 1. Z' O X' Z Y' L z3 W c2 c2 z2 2 2 β zm2 q2 X 1 C c3 z1 c3 c1 zm1 3 zm3 3 α q3 Y 4 4 z4 c4 c4 zm4 q4 1 c1 q1 Figure 1: Dynamical moel of the machine with seven DOF For the basis of the moel is use Mercees G270 CDI, which is equippe with 7,62 mm Kalashniov s machine gun an 12,7 mm NVT machine gun. The moel [2] allows a research on vibrations, which ensue in the vehicle s suspension from the shooting of ifferent types of mounte machine-guns by introucing energy of recoil. Base on experiments mae in [2] an [3], it is unerstoo that when the shooting is at place the maximum mean square angular isplacement of the barrel is DOI: 10.1515/bo-2017-0186 2017. This wor is license uner the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License. 262 Unauthenticate Downloa Date 12/6/17 3:59 AM
32,4722 thousanths, an when the shooting is in movement on macaam 44,4433 thousanths. We now that one-thousanths mean square angular eviation of the barrel on thousan meters gives eviation of one meter in vertical. Therefore the vertical eviation of shooting is forty-four meter. If we want to reuce the angular isplacement, we have to esign а amper in the gun-carriage. 2. Introucing energy of recoil Classical amper in passive type [4] has two components. First - which collects energy, an secon - which absorbs energy of recoil. Figure 2 shows funamental schema of that mechanism with spring an amper. K C o β gun-carriage boy Figure 2: Funamental schema of an elastic suspension In that case, the machine gun an the elastic suspension have one egree of freeom movement on axis X. On that base is erive a ifferential equation of the machine gun s motion, which is: m.x +.x + c.x = F (1) отк. where: - m machine gun s mass, g; - coefficient of amping, N.s/m; - c coefficient of stiffness, N/m; - F rcl. force of recoil, N; - x movement on axis X. From the ifferential equations is erive the transmission function of the motion. W = 1 2 m.p +.p + c (2) It is nown from the mechanics, that in such case the force transmits trough the spring. Then value of the force F in the point of attaching is: F = c. x (3) F value of the force in the point of attaching. If we accept, that x = 0 when the machine gun is in front position without shooting, then x = x. In that case the transmission function between the recoil s force an the force in the point of attaching is: W F = = (4) 2 Fотк m.p +.p + c The spectral ensity in the force of the point of attaching is: c = W. ( jω ) (5) F Fотк. The ecomposition of that force on the axes of the coorinate system, connecte with the vehicle s boy, may be also consiere as a transmission function. In that case: Fz M x M y = F = = W. F F W. W. z ( jω ); x y z ( jω ); x ( jω ), y (6) 263 Unauthenticate Downloa Date 12/6/17 3:59 AM
where: - Wz = sin β ; - Wx = (cos β.sinα ).zt (sin β ). yt ; - Wy = (cos β.cosα ).zt + (sin β ). xt The spectral ensities from the example (6) are use as inputs in the matrix of the spectral ensities, which are escribe in [1]. 3. Determination of the coefficients of the elastic suspension A ey step in the synthesis of the elastic suspension is the etermination of the stiffness coefficient С, N/m an the amping coefficient К, N.s/m. Figure 3 shows mean square angular eviations of the bore line of the machine gun s barrel, in ifferent values of these parameters. The ata is for shooting at place, with a position of the machine gun in horizontal plane at 90 angle an 0 in vertical plane. Figure 3 shows, that the function oes not have an extremum, which means that there is no optimal solution. Therefore, for the project of the elastic suspension we nee to choose a value of one of the parameters С or К an the permissible eviation an to eterminate the value of the other parameter from the scheme. If we accept that the permissible mistae is 2 thousanths, the stiffness coefficient С is 8 N/m, then the value of the amping coefficient turns out 300 N.s/m. Figure 3: Mean square angular eviations of the bore line of 12,7 mm NVT machine gun s barrel in ifferent values of the coefficients С an К of the elastic suspension in thousans The great value of the amping coefficient К an the little value of the stiffness coefficient С show, that the suspension has to be a recoil system, not a classical elastic suspension. 4. Research on the eviations in the machine gun s bore line in shooting at place with an elastic suspension There were hel a numerical experiments for etermination of the mean square angular eviations of the amplitue s oscillations rising in the boy an the suspension of the vehicle, in shooting at place with 12,7 mm NVT machine gun with an elastic suspension. Comparing the results with these at [2], shows that in the worst position of shooting - horizontal angel 90, vertical angel 0 - the roll ecreases 16 times. In the most favorable position of shooting - 0 horizontal angel an 0 vertical angel - all eviations, ecrease 14 times. If we use an elastic suspension with this value of the amping 264 Unauthenticate Downloa Date 12/6/17 3:59 AM
an stiffness coefficients, the mean square angular eviations in the vehicle s suspension ecrease from 26 mm to 1,6 mm. In these results, we may raw a conclusion, that the elastic suspension will raise the efficiency of shooting 10 times. In aition, the chance of occurrence of amage in the vehicle s boy an suspension is brought to zero. 5. Research on the eviations in the machine gun s bore line in shooting in movement with an elastic suspension eries of numerical experiments were hel for the etermination of the elastic suspension s influence for the eviation of the bore line of the machine gun s barrel. The experiments were carrie out in ifferent types of roas an ifferent positions of the machine gun. Input ata: - type of the roa asphalt (1), pavement (2), macaam (3); - horizontal angel of the machine gun - 0 an 90 ; - vertical angel of the machine gun - 0 ; - spee 0 90 m/h. Figure 4, 5 an 6 show the mean square angular eviations of the bore line of the machine gun s barrel with an without amper. Figure 4: Mean square angular eviations of the bore line of the machine gun s barrel in shooting in movement on asphalt Figure 5: Mean square angular eviations of the bore line of the machine gun s barrel in shooting in movement on pavement 265 Unauthenticate Downloa Date 12/6/17 3:59 AM
Figure 6: Mean square angular eviations of the bore line of the machine gun s barrel in shooting in movement on macaam This figure shows that the elastic suspension influences a lot in 90 horizontal position an less in 0 horizontal position. This elastic suspension exclues influence of horizontal position of the machine gun lie essential factor of istraction of shooting at motion. Basic interference is roa roughness. In this elastic suspension, we cannot ecrease the influence of the roa, but we can reuce the issipation of the shooting an the influence on the vehicle s suspension. 6. Conclusions 1. The spectral ensities receive on the exit of the elastic suspension are entrance for the vehicle s boy en suspension. The ecomposition of that force of recoil is a system of transfer functions an the moel is simplifie. 2. The eviations of the barrel in function of amping an stiffness coefficient o not have an extremum. Therefore, for the project of the elastic suspension we nee to choose a value of one of the parameters С or К an the permissible eviation an to eterminate the value of the other parameter from the figure 3. The little value of the stiffness coefficient С shows, that the suspension has to be a recoil system. 3. In shooting at place with an elastic suspension in the worst position the roll ecreases 16 times. This increases the efficiency of shooting an reuces the issipation. 4. An elastic suspension in passive type cannot ecrease the influence of the roa, but it can reuce the issipation of the shooting an the influence on the vehicle s suspension. References [1] pironov., Metho of approach for using the basic equation of statistical ynamics for analyzing the frequency response of the boy of an armoure vehicle, Proceeings of 2n International cientific Conference TECHNIC. TECHNOLOGIE. EDUCATION. AFETY, pp. 1310-3946, Velio Tarnovo, Bulgaria, May, 2014. [2] pironov., tefanov., Yotov T., Research on the vibro-ynamical processes, which ensue in an armoure vehicle suspension from the shooting of mounte machine-guns at place, Proceeings of Annual University cience Conference of National Military University Vasil Levsi, pp. 1314-1937, Velio Tarnovo, Bulgaria, July, 2014. 266 Unauthenticate Downloa Date 12/6/17 3:59 AM
[3] pironov., Lilov I., Georgiev I., Research on the iffusion in vertical irection uring shooting with a weapon mounte on an armoure vehicle uner ifferent movement regimen, Proceeings of Annual University cience Conference of National Military University Vasil Levsi, pp. 1314-1937, Velio Tarnovo, Bulgaria, July, 2014. [4] pironov., Research on the efficiency of the armoure vehicles uring peaceeeping operations, Dissertation, Velio Tarnovo, National Military University Vasil Levsi, 2014, 234 p. 267 Unauthenticate Downloa Date 12/6/17 3:59 AM