Firefighting unmanned aerial vehicle fire extinguishing experiment device

Abstract

The present application belongs to the field of fire-fighting unmanned plane fire extinguishing technology, and particularly relates to a fire-fighting unmanned plane fire extinguishing experiment device, comprising: a driving base in a water pool, a lifting driving part in the driving base, a simulated building wall above the driving base, the lifting driving part being in transmission connection with the simulated building wall, a combustion chamber being formed in the simulated building wall, a window being arranged on one side of the combustion chamber, the window being formed in the simulated building wall, a fire-fighting unmanned plane being arranged on one side of the simulated building wall, a jet pipe being fixedly connected to the fire-fighting unmanned plane, and the jet pipe facing the window. In the present application, water is supplied to the jet pipe through a water supply mechanism, and the water flow is shot to the combustion chamber through the jet pipe. In this process, the water flow and water pressure are changed through a flow control valve, the situation in the combustion chamber is observed, the current water pressure and water flow are recorded, so as to verify the influence of the water flow and water pressure on the fire extinguishing effect. At the same time, the simulated building wall is arranged in a lifting manner, so that the device can simulate the fire extinguishing situation when a fire breaks out at different height floors.

Description

Technical Field

[0001] This invention belongs to the field of firefighting drone technology, and particularly relates to a firefighting drone firefighting experimental device. Background Technology

[0002] To date, fire safety in high-rise buildings remains a major challenge worldwide, as fire extinguishing equipment and strategies are inadequate in dealing with fires in such buildings, especially those over 50 meters tall.

[0003] With the development of drone technology, it has become a reality to use drones to extinguish fires both indoors and outdoors in high-rise buildings. There are generally two types of existing fire-fighting drones: one type carries fire extinguishing bombs and extinguishes fires by dropping them, and the other type carries water pipes and extinguishes fires by using water flow.

[0004] In the process of using drones to carry water pipes to extinguish fires, the size and pressure of the water flow play a crucial role in the fire extinguishing effect. However, there is no relevant research in the existing technology, so there is an urgent need for a fire-fighting drone fire extinguishing experimental device. Summary of the Invention

[0005] The purpose of this invention is to provide a fire-fighting drone experimental device to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A fire-fighting drone fire extinguishing experimental device includes: a water tank, a drive base fixedly connected to the middle of the water tank, a lifting drive unit disposed inside the drive base, a simulated building wall disposed above the drive base, the simulated building wall being liftable, the lifting drive unit being pulsatorically connected to the simulated building wall, a combustion chamber being formed on the simulated building wall, a window being disposed on one side of the combustion chamber, the window being formed on the simulated building wall, a fire-fighting drone being disposed on one side of the simulated building wall, a jet pipe being fixedly connected to the fire-fighting drone, the jet pipe facing the window, the jet pipe being connected to a water supply mechanism, and a flow control valve being disposed between the jet pipe and the water supply mechanism.

[0008] Preferably, the water supply mechanism includes a second water supply pipe connected to the jet pipe, a water pump and a flow control valve are installed on the second water supply pipe, the flow control valve is close to the fire-fighting drone, the bottom end of the second water supply pipe is connected to the outlet of a three-way valve, the two inlets of the three-way valve are respectively connected to a fire pump and a filter, the filter is connected to a first water supply pipe, and the first water supply pipe is connected to the water tank.

[0009] Preferably, a vertically arranged lifting cylinder is fixedly connected to the top surface of the drive base, a lifting block is vertically slidably connected inside the lifting cylinder, the lifting block is connected to the lifting drive unit, and the simulated building wall is fixedly connected to the top of the lifting block.

[0010] Preferably, the lifting drive unit includes a lifting assembly and a drive assembly. The drive assembly is drivenly connected to the lifting assembly, and the lifting assembly is drivenly connected to the lifting block. The lifting assembly includes two first sleeves vertically fixed in the drive base. A lead screw is vertically rotatably connected in the first sleeve. The top end of the lead screw passes through the drive base and is threaded into a threaded hole. The threaded hole is vertically opened in the lifting block, and the top end of the lead screw is lower than the top end of the lifting sleeve.

[0011] A mounting shell is fixedly connected to the middle of the first sleeve. A worm gear is vertically rotatably connected inside the mounting shell. The worm gear is coaxially fixed to the lead screw. The worm gear meshes with a worm. The worm passes through the mounting shell and is connected to the drive assembly for transmission.

[0012] Preferably, the drive assembly includes a transmission box fixedly connected to the drive base, a first transmission rod rotatably connected to the transmission box via two first bearing seats, a second bevel gear coaxially fixedly connected to the first transmission rod, the second bevel gear being located inside the transmission box, the second bevel gear meshing with a third bevel gear, and the third bevel gear being fixedly connected to the output shaft of the first motor;

[0013] Both ends of the first transmission rod extend out of the transmission box and are coaxially fixed to a fourth bevel gear. The fourth bevel gear meshes with a first bevel gear, and the first bevel gear is coaxially fixed to one end of the worm gear that extends out of the mounting housing.

[0014] Preferably, two bearings are coaxially fixed to the inner wall of the mounting housing, the two bearings are respectively located at both ends of the mounting housing, a rotating cylinder is coaxially fixed to the inner edge of the bearing, and the worm gear is fixed between the two rotating cylinders.

[0015] Preferably, a fire source is provided on the bottom wall of the combustion chamber, and a shielding mechanism is provided on the side wall of the combustion chamber, with the shielding mechanism corresponding to the window.

[0016] Preferably, the shielding mechanism includes a horizontal shielding component and a vertical shielding component. The horizontal shielding component includes a second motor fixedly connected to the inner side wall of the combustion chamber. The second motor is disposed on the same side as the window. A first bidirectional threaded rod is fixedly connected to the output shaft of the second motor. The first bidirectional threaded rod is rotatably connected to the inner side wall of the combustion chamber through two second bearing seats. Both ends of the first bidirectional threaded rod are threadedly connected to a first connecting rod. A first shielding plate is fixedly connected to the end of the first connecting rod away from the first bidirectional threaded rod. The first shielding plate is disposed corresponding to the window. A first slider is fixedly connected to the end of the first connecting rod away from the first shielding plate. The first slider is slidably connected in a first sliding groove. The first sliding groove is fixedly connected to the inner side wall of the combustion chamber.

[0017] Preferably, the vertical shielding assembly includes a third motor fixed to the inner side wall of the combustion chamber, the third motor being disposed on the same side as the window, a second bidirectional threaded rod being coaxially fixed to the output shaft of the third motor, the second bidirectional threaded rod being rotatably connected to the inner side wall of the combustion chamber through a third bearing seat, both ends of the second bidirectional threaded rod being threadedly connected to a second connecting rod, one end of the second connecting rod being fixedly connected to a second shielding plate, the second shielding plate being disposed corresponding to the window, the second shielding plate being in slidable contact with the first shielding plate, and the end of the second connecting rod away from the second shielding plate being fixedly connected to a second slider, both of the second sliders being slidably connected in a second sliding groove, the second sliding groove being fixedly connected to the inner side wall of the combustion chamber.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] In this invention, water is supplied to the jet pipe through a water supply mechanism, and the water is jetted into the combustion chamber through the jet pipe. During this process, the water flow and water pressure are changed by a flow control valve, the situation inside the combustion chamber is observed, and the current water pressure and water flow rate are recorded, thereby simulating the effect of different water flow rates and water pressures on the fire extinguishing effect. At the same time, the simulated building wall can be raised and lowered, so that this device can simulate the fire extinguishing situation when a fire starts at a different floor height. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2This is a schematic diagram of the overall structure of the simulated building wall in this invention;

[0023] Figure 3 for Figure 2 A magnified view of a section at point A in the middle;

[0024] Figure 4 for Figure 2 A magnified view of a section at point B in the middle;

[0025] The components include: 1. Water tank; 2. First water supply pipe; 3. Filter; 4. Three-way valve; 5. Fire pump; 6. Water pump; 7. Second water supply pipe; 8. Flow control valve; 9. Firefighting drone; 10. Jet pipe; 11. Drive base; 12. Lifting cylinder; 13. Lifting block; 14. Imitation building wall; 15. Combustion chamber; 16. Lead screw; 17. Threaded hole; 18. First sleeve; 19. Bearing; 20. Worm gear; 21. Worm; 22. Mounting housing; 23. First bevel gear; 24. First transmission rod; 25. Second bevel gear. 26. Wheel; 27. Third bevel gear; 28. First bearing housing; 29. ​​Transmission box; 30. Rotary drum; 31. Second motor; 32. Second bearing housing; 33. First slide groove; 34. First bidirectional threaded rod; 35. First connecting rod; 36. First baffle plate; 37. Window; 38. Second baffle plate; 39. Fire source; 40. Third motor; 41. Second slide groove; 42. Second slide groove; 43. Second bidirectional threaded rod; 44. Third bearing housing; 45. Second connecting rod; 46. Fourth bevel gear. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1

[0029] Reference Figures 1 to 4This embodiment discloses a fire-fighting drone fire extinguishing experimental device, including: a water tank 1, a drive base 11 fixedly connected to the middle of the interior of the water tank 1, a lifting drive unit provided inside the drive base 11, a simulated building wall 14 provided above the drive base 11, the simulated building wall 14 being liftable, the lifting drive unit being connected to the simulated building wall 14, a combustion chamber 15 provided on the simulated building wall 14, a window 37 provided on one side of the combustion chamber 15, the window 37 being opened on the simulated building wall 14, a fire-fighting drone 9 provided on one side of the simulated building wall 14, a jet pipe 10 fixedly connected to the fire-fighting drone 9, the jet pipe 10 facing the window 37, the jet pipe 10 being connected to a water supply mechanism, and a flow control valve 8 being provided between the jet pipe 10 and the water supply mechanism.

[0030] In this embodiment, water is supplied to the jet pipe 10 through the water supply mechanism, and the water is jetted into the combustion chamber 15 through the jet pipe 10. During this process, the water flow and water pressure are changed by the flow control valve 8, the situation inside the combustion chamber 15 is observed, and the current water pressure and water flow rate are recorded, thereby verifying the influence of water flow rate and water pressure on the fire extinguishing effect. At the same time, the simulated building wall 14 can be raised and lowered, so that this device can simulate the fire extinguishing situation when a fire starts at a different height.

[0031] The scheme is further optimized. The water supply mechanism includes a second water supply pipe 7 connected to the jet pipe 10. A water pump 6 and a flow control valve 8 are installed on the second water supply pipe 7. The flow control valve 8 is close to the fire-fighting drone 9. The bottom end of the second water supply pipe 7 is connected to the outlet of a three-way valve 4. The two inlets of the three-way valve 4 are respectively connected to the fire pump 5 and the filter 3. The filter 3 is connected to the first water supply pipe 2. The first water supply pipe 2 is connected to the water tank 1.

[0032] Initially, water from fire pump 5 is pumped into jet pipe 10 via second water supply pipe 7 by water pump 6. The flow rate is controlled by flow control valve 8. A water pressure monitoring sensor is installed on second water supply pipe 7 to test the current water pressure. Once the water in water tank 1 has accumulated to a certain level, the three-way valve 4 is opened and closed, and water pump 6 pumps water from water tank 1 into jet pipe 10 via second water supply pipe 7.

[0033] In a further optimized design, a vertically mounted lifting cylinder 12 is fixedly attached to the top surface of the drive base 11. A lifting block 13 is vertically slidably connected inside the lifting cylinder 12. The lifting block 13 is connected to the lifting drive unit for transmission. The simulated building wall 14 is fixedly attached to the top of the lifting block 13.

[0034] The lifting block 13 is driven to rise and fall by the lifting drive unit, which in turn drives the simulated building wall 14 to rise and fall.

[0035] The scheme is further optimized. The lifting drive unit includes a lifting component and a drive component. The drive component is connected to the lifting component in a transmission manner. The lifting component is connected to the lifting block 13 in a transmission manner. The lifting component includes two first sleeves 18 that are vertically fixed in the drive base 11. A lead screw 16 is vertically rotatably connected in the first sleeve 18. The top end of the lead screw 16 passes through the drive base 11 and is threaded into a threaded hole 17. The threaded hole 17 is vertically opened in the lifting block 13. The top end of the lead screw 16 is lower than the top end of the lifting cylinder 12.

[0036] A mounting shell 22 is fixedly connected to the middle of the first sleeve 18. A worm gear 20 is vertically rotatably connected inside the mounting shell 22. The worm gear 20 is coaxially fixedly connected to the lead screw 16. The worm gear 20 meshes with a worm 21. The worm 21 passes through the mounting shell 22 and is connected to the drive assembly for transmission.

[0037] The worm 21 is driven to rotate by the drive assembly. The worm 21 drives the worm wheel 20 to rotate in the vertical direction, which in turn drives the lead screw 16 to rotate. The rotation of the lead screw 16 drives the lifting block 13 to rise or fall.

[0038] The scheme is further optimized. The drive component includes a transmission box 28 fixed in the drive base 11. A first transmission rod 24 is rotatably connected in the transmission box 28 through two first bearing seats 27. A second bevel gear 25 is coaxially fixed on the first transmission rod 24. The second bevel gear 25 is located in the transmission box 28. The second bevel gear 25 meshes with a third bevel gear 26. The third bevel gear 26 is fixed to the output shaft of the first motor.

[0039] Both ends of the first transmission rod 24 extend out of the transmission box 28 and are coaxially fixed to the fourth bevel gear 46. The fourth bevel gear 46 meshes with the first bevel gear 23, which is coaxially fixed to one end of the worm gear 21 that extends out of the mounting housing 22.

[0040] The first motor (not shown in the figure) drives the third bevel gear 26 to rotate. The third bevel gear 26 drives the first transmission rod 24 to rotate through the second bevel gear 25 meshing with it. The first transmission rod 24 drives the fourth bevel gear 46 to rotate, and then drives the worm gear 21 to rotate through the first bevel gear 23.

[0041] In a further optimized design, two bearings 19 are coaxially fixed to the inner wall of the mounting shell 22. The two bearings 19 are located at both ends of the mounting shell 22, and a rotating cylinder 29 is coaxially fixed to the inner edge of the bearings 19. A worm gear 20 is fixed between the two rotating cylinders 29.

[0042] This design is intended to make the worm gear 20 rotate more smoothly and stably within the mounting housing 22.

[0043] To further optimize the design, a fire source 39 is installed on the bottom wall of the combustion chamber 15, and a shielding mechanism is installed on the side wall of the combustion chamber 15, with the shielding mechanism corresponding to the window 37.

[0044] The size of window 37 can be changed using the obscuring mechanism.

[0045] Further optimization of the scheme: the shielding mechanism includes a horizontal shielding component and a vertical shielding component. The horizontal shielding component includes a second motor 30 fixedly connected to the inner wall of the combustion chamber 15. The second motor 30 is located on the same side as the window 37. A first bidirectional threaded rod 34 is fixedly connected to the output shaft of the second motor 30. The first bidirectional threaded rod 34 is rotatably connected to the inner wall of the combustion chamber 15 through two second bearing seats 31. Both ends of the first bidirectional threaded rod 34 are threadedly connected to a first connecting rod 35. A first shielding plate 36 is fixedly connected to the end of the first connecting rod 35 away from the first bidirectional threaded rod 34. The first shielding plate 36 is correspondingly located to the window 37. A first slider 33 is fixedly connected to the end of the first connecting rod 35 away from the first shielding plate 36. The first slider 33 is slidably connected in a first sliding groove 32. The first sliding groove 32 is fixedly connected to the inner wall of the combustion chamber 15.

[0046] The second motor 30 drives the first bidirectional threaded rod 34 to rotate, which in turn causes the two first baffles 36 to move away from or closer to each other, thereby changing the size of the window 37. The function of the first groove 32 is to prevent the first baffles 36 from rotating with the first bidirectional threaded rod 34.

[0047] Further optimization of the scheme: the vertical shielding assembly includes a third motor 40 fixedly connected to the inner wall of the combustion chamber 15. The third motor 40 is located on the same side as the window 37. A second bidirectional threaded rod 43 is coaxially fixedly connected to the output shaft of the third motor 40. The second bidirectional threaded rod 43 is rotatably connected to the inner wall of the combustion chamber 15 through a third bearing seat 44. Both ends of the second bidirectional threaded rod 43 are threadedly connected to a second connecting rod 45. A second shielding plate 38 is fixedly connected to one end of the second connecting rod 45. The second shielding plate 38 is correspondingly located to the window 37. The second shielding plate 38 is in sliding contact with the first shielding plate 36. A second slider 42 is fixedly connected to the end of the second connecting rod 45 away from the second shielding plate 38. Both second sliders 42 are slidably connected in a second sliding groove 41. The second sliding groove 41 is fixedly connected to the inner wall of the combustion chamber 15.

[0048] The third motor 40 drives the second bidirectional threaded rod 43 to rotate. The rotation of the second bidirectional threaded rod 43 causes the two second baffles 38 to move away from or closer to each other, thereby cooperating with the two first baffles 36 to change the size of the window 37.

[0049] By changing the size of window 37, the impact of different window 37 sizes on firefighting drones is simulated.

[0050] Example 2

[0051] The difference from Embodiment 1 is that, in this embodiment, a tracer particle delivery pipe is connected to the side wall of the second water supply pipe 7. The tracer particles are delivered into the second water supply pipe 7 through the tracer particle delivery pipe and mixed with the water flow. The movement of the tracer particles during fire extinguishing is observed, thereby determining the fire extinguishing status.

[0052] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0053] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A fire-fighting drone experimental device, characterized in that, include: A water tank (1) is fixedly connected to a drive base (11) in the middle of its interior. A lifting drive unit is provided inside the drive base (11). A simulated building wall (14) is provided above the drive base (11). The simulated building wall (14) can be lifted and lowered. The lifting drive unit is connected to the simulated building wall (14) in a transmission connection. A combustion chamber (15) is provided on the simulated building wall (14). A window (37) is provided on one side of the combustion chamber (15). The window (37) is opened on the simulated building wall (14). A fire-fighting drone (9) is provided on one side of the simulated building wall (14). A jet pipe (10) is fixedly connected to the fire-fighting drone (9). The jet pipe (10) faces the window (37). The jet pipe (10) is connected to a water supply mechanism. A flow control valve (8) is provided between the jet pipe (10) and the water supply mechanism. The water supply mechanism includes a second water supply pipe (7) connected to the jet pipe (10). A water pump (6) and a flow control valve (8) are installed on the second water supply pipe (7). The flow control valve (8) is close to the fire-fighting drone (9). The bottom end of the second water supply pipe (7) is connected to the outlet of a three-way valve (4). The two inlets of the three-way valve (4) are respectively connected to a fire pump (5) and a filter (3). The filter (3) is connected to a first water supply pipe (2). The first water supply pipe (2) is connected to the water tank (1). A vertically arranged lifting cylinder (12) is fixedly connected to the top surface of the drive base (11). A lifting block (13) is vertically slidably connected inside the lifting cylinder (12). The lifting block (13) is connected to the lifting drive unit. The simulated building wall (14) is fixedly connected to the top of the lifting block (13). A fire source (39) is provided on the bottom wall of the combustion chamber (15), and a shielding mechanism is provided on the side wall of the combustion chamber (15). The shielding mechanism is provided in correspondence with the window (37). The shielding mechanism includes a horizontal shielding component and a vertical shielding component. The horizontal shielding component includes a second motor (30) fixed to the inner wall of the combustion chamber (15). The second motor (30) is arranged on the same side as the window (37). A first bidirectional threaded rod (34) is fixed to the output shaft of the second motor (30). The first bidirectional threaded rod (34) is rotatably connected to the inner wall of the combustion chamber (15) through two second bearing seats (31). Both ends of the first bidirectional threaded rod (34) are threaded with a first connecting rod (35). A first shielding plate (36) is fixed to the end of the first connecting rod (35) away from the first bidirectional threaded rod (34). The first shielding plate (36) is arranged correspondingly to the window (37). A first slider (33) is fixed to the end of the first connecting rod (35) away from the first shielding plate (36). The first slider (33) is slidably connected in a first sliding groove (32). The first sliding groove (32) is fixed to the inner wall of the combustion chamber (15). The vertical shielding assembly includes a third motor (40) fixed to the inner wall of the combustion chamber (15). The third motor (40) is located on the same side as the window (37). A second bidirectional threaded rod (43) is coaxially fixed to the output shaft of the third motor (40). The second bidirectional threaded rod (43) is rotatably connected to the inner wall of the combustion chamber (15) through a third bearing seat (44). Both ends of the second bidirectional threaded rod (43) are threaded with a second connecting rod (45). One end of the second connecting rod (45) is fixed with a second shielding plate (38). The second shielding plate (38) is correspondingly located to the window (37). The second shielding plate (38) is in sliding contact with the first shielding plate (36). The end of the second connecting rod (45) away from the second shielding plate (38) is fixed with a second slider (42). Both second sliders (42) are slidably connected in a second sliding groove (41). The second sliding groove (41) is fixed to the inner wall of the combustion chamber (15).

2. The fire-fighting drone fire-extinguishing experimental device according to claim 1, characterized in that: The lifting drive unit includes a lifting assembly and a drive assembly. The drive assembly is connected to the lifting assembly in a transmission manner. The lifting assembly is connected to the lifting block (13) in a transmission manner. The lifting assembly includes two first sleeves (18) that are vertically fixed in the drive base (11). A lead screw (16) is vertically rotatably connected in the first sleeve (18). The top end of the lead screw (16) passes through the drive base (11) and is threaded into a threaded hole (17). The threaded hole (17) is vertically opened in the lifting block (13). The top end of the lead screw (16) is lower than the top end of the lifting cylinder (12). A mounting shell (22) is fixedly connected to the middle of the first sleeve (18). A worm wheel (20) is vertically rotatably connected inside the mounting shell (22). The worm wheel (20) is coaxially fixedly connected to the lead screw (16). The worm wheel (20) meshes with a worm (21). The worm (21) passes through the mounting shell (22) and is connected to the drive assembly for transmission.

3. The fire-fighting drone fire-extinguishing experimental device according to claim 2, characterized in that: The drive assembly includes a transmission box (28) fixedly connected to the drive base (11). A first transmission rod (24) is rotatably connected to the transmission box (28) via two first bearing seats (27). A second bevel gear (25) is coaxially fixedly connected to the first transmission rod (24). The second bevel gear (25) is located inside the transmission box (28). The second bevel gear (25) meshes with a third bevel gear (26). The third bevel gear (26) is fixedly connected to the output shaft of the first motor. Both ends of the first transmission rod (24) extend out of the transmission box (28) and are coaxially fixed to a fourth bevel gear (46). The fourth bevel gear (46) meshes with a first bevel gear (23). The first bevel gear (23) is coaxially fixed to one end of the worm gear (21) that extends out of the mounting shell (22).

4. The fire-fighting drone fire-extinguishing experimental device according to claim 3, characterized in that: Two bearings (19) are coaxially fixed to the inner wall of the mounting shell (22). The two bearings (19) are located at the two ends of the mounting shell (22). A rotating cylinder (29) is coaxially fixed to the inner edge of the bearing (19). The worm gear (20) is fixed between the two rotating cylinders (29).

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