Electric bicycle frame impact test load with adjustable center of gravity and accurate positioning method

Abstract

The invention discloses a gravity-center-adjustable electric bicycle frame impact test load and a precise positioning method, the load comprises a weight supporting plate, a weight and two sets of supporting assemblies, one end of the weight supporting plate is provided with a first long hole, the other end of the weight supporting plate is provided with a second long hole, the weight is installed on the weight supporting plate, and the weight is installed on the weight supporting plate. The two sets of supporting assemblies support the two sides of the weight supporting plate respectively. Each supporting assembly comprises a U-shaped base, a fastening screw and a supporting column. According to the accurate positioning method, the coordinate of the center position of the surface of the saddle is accurately obtained through the three-coordinate measuring machine, then the actual barycentric coordinate of the vehicle frame impact test load is calculated through the weighted average method, finally, the barycentric correspondence is achieved through the load adjusting mechanism, and millimeter-level accurate alignment can be achieved. According to the invention, the positioning precision can be better ensured, and the test result can be better ensured.

Description

Technical Field

[0001] This invention belongs to the field of electric bicycle frame impact testing technology, specifically relating to an electric bicycle frame impact test load and precise positioning method with an adjustable center of gravity. Background Technology

[0002] Some electric bicycles have a frame without a seat tube (the seat tube is used to mount the saddle). When assembling this type of frame, the seat tube is installed first, and then the saddle is installed on top of the seat tube. However, when conducting impact strength tests on the frame of an electric bicycle without a seat tube, a 70kg weight needs to be fixed at the corresponding position on the saddle to simulate the weight of a rider. This raises the issue of how to secure the 70kg weight.

[0003] Currently, the relevant standards for testing electric bicycle frames (such as GB 17761) only specify the installation method of a 70kg weight for electric bicycle frames with a seat tube structure in the frame impact strength test, but do not specify the installation method of a 70kg weight for electric bicycle frames without a seat tube structure in the frame impact strength test.

[0004] According to research, in current frame impact strength tests, for electric bicycle frames without a saddle tube structure, a 70kg load is directly fixed to the frame by binding. The main methods used are "rope binding + buckle tightening" or "chain wrapping + bolt fixing" to install the load.

[0005] The existing technical solution for securing a 70kg load by binding has the following drawbacks:

[0006] 1. During the binding process, uneven binding force can easily cause the load to shift, and it is impossible to install the load at the actual center height of the saddle surface. This results in insufficient positioning accuracy, with the center of gravity of the load deviating from the actual center of the saddle surface by more than 10mm.

[0007] 2. Due to the elastic deformation of the ropes and chains themselves, the load is not sufficiently constrained and the stability is poor. In the impact test, the load displacement rate is >50%.

[0008] 3. The binding position needs to be repeatedly adjusted, and there is no standardized adjustment structure, resulting in low efficiency. The installation of a single frame requires two people to work together and takes more than 60 minutes. Summary of the Invention

[0009] The first objective of this invention is to provide an electric bicycle frame impact test load with an adjustable center of gravity.

[0010] The second objective of this invention is to provide a precise positioning method for mounting the impact test load of the electric bicycle frame on the frame.

[0011] The first objective of this invention is achieved through the following technical solution:

[0012] An impact test load for an electric bicycle frame with an adjustable center of gravity is characterized by comprising a weight support plate, weights, and two sets of support components. One end of the weight support plate has a first elongated hole for corresponding connection with the seat bucket mounting hole on the rear rack bracket of the frame, and the other end of the weight support plate has a second elongated hole. The length direction of the first and second elongated holes is the width direction of the frame. The weights are mounted on the weight support plate, and the mounting position of the weights can be adjusted along the length direction of the frame. The two sets of support components support the two sides of the weight support plate respectively. The support components include a U-shaped base, a fastening screw, and a support column. The U-shaped base is used to connect to the side tube of the frame, the support column is vertically mounted on the top of the U-shaped base, the fastening screw is vertically mounted on the upper end of the support column, and the end of the weight support plate is connected to the fastening screw through the second elongated hole. The mounting height of the weight support plate is adjustable.

[0013] A further technical solution of the present invention is as follows: the fastening screw passes through the second elongated hole, and at least two locking nuts are provided on the fastening screw. The weight support plate is clamped between two adjacent locking nuts. The connection position of the weight support plate on the fastening screw can be adjusted by adjusting the position of the locking nuts.

[0014] A further technical solution of the present invention is as follows: the U-shaped base is provided with a U-shaped groove with the opening facing downward, and connection holes are provided on both sides of the U-shaped groove. When connected to the side tube of the frame, the side tube is located in the U-shaped groove of the U-shaped base and is connected by connecting bolts passing through the connection holes.

[0015] A further technical solution of the present invention is as follows: a row of more than one row of weight fixing holes is provided on the weight support plate between the first elongated hole and the second elongated hole, and the weight is located on the weight support plate and fixed through the weight fixing holes.

[0016] A further technical solution of the present invention is as follows: the upper part of the U-shaped base is provided with a welding connection hole, and the lower end of the support column is provided with a lower welding rod, which is inserted into the welding connection hole and welded together.

[0017] A further technical solution of the present invention is as follows: the upper end of the support column is provided with a top threaded hole, and the lower end of the fastening screw is threadedly connected to the top threaded hole.

[0018] The second objective of this invention is achieved through the following technical solution:

[0019] A precise positioning method for mounting the impact test load on the frame of an electric bicycle as described above, characterized by comprising the following steps:

[0020] S1. Fix the complete electric bicycle with the frame to be tested onto the coordinate measuring machine. Obtain the center position coordinates Xs, Ys, and Zs of the saddle surface of the electric bicycle through the coordinate measuring machine. Project the center position coordinates of the saddle surface onto the frame using a laser line projector and mark the installation reference point at the corresponding position on the frame.

[0021] S2, obtain the mass a of the weight support plate, the mass b of the weight, the mass c of the first set of support components and the mass d of the second set of support components, establish a coordinate system with the center of the surface of the weight support plate as the origin, and calculate the center of gravity coordinates Xw, Yw and Zw of the frame impact test load by weighted average method;

[0022] S3, Fix the frame, pre-install the frame impact test load onto the frame, and ensure that the levelness of the weight support plate of the frame impact test load is ≤0.5°;

[0023] S4. Based on the mounting reference point on the frame, adjust the mounting height of the weight support plate so that Zw corresponds to Zs; adjust the connection position between the first elongated hole and the seat mounting hole and the connection position between the second elongated hole and the fastening screw so that Yw corresponds to Ys; adjust the mounting position of the weight along the length of the frame so that Xw corresponds to Xs; finally, make the center of gravity coordinate position of the frame impact test load correspond to the center position coordinate of the saddle surface, and then tighten all the connection parts of the frame impact test load.

[0024] A further technical solution of the present invention is as follows: In step S4, the final adjustment is made so that the deviations of the center of gravity coordinates of the frame impact test load from the center position coordinates of the saddle surface in the X, Y, and Z directions are all ≤5mm.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This invention can adjust the installation height of the weight support plate, the connection position between the first elongated hole and the seat mounting hole, the connection position between the second elongated hole and the fastening screw, and the installation position of the weight along the length of the frame, so that the center of gravity coordinate position of the impact test load of the frame corresponds to the center position coordinate position of the saddle surface, thereby better ensuring the positioning accuracy and the test results.

[0027] 2. When the impact test load of the electric bicycle frame of the present invention is connected to the frame, it is connected to the seat bucket mounting hole on the rear rack bracket of the frame through the first elongated hole, and the U-shaped base is connected to the side tube of the frame. This achieves all-round rigid constraint of the impact test load, which is no longer the existing binding fixation. It eliminates the problem of elastic deformation of ropes / chains when the existing binding fixation is used, and ensures that there is no relative displacement between the load and the frame during the test. The effect is significant.

[0028] 3. The precise positioning method of this invention uses a coordinate measuring machine to accurately obtain the center coordinates of the saddle surface, and uses a laser line projector to mark the corresponding installation reference point on the frame, thus achieving objectification of the positioning reference. Then, the actual center of gravity coordinates of the frame impact test load are calculated using a weighted average method, eliminating uncertainty in the center of gravity position. Finally, the adjustment mechanism of the frame impact test load of this invention is used to ensure that the center of gravity coordinates of the frame impact test load correspond to the center coordinates of the saddle surface, achieving millimeter-level precise alignment. This invention essentially eliminates human error and solves the industry pain point of "excessive deviation between the installation position of the heavy object and the actual center of the saddle surface." Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the electric bicycle frame impact test load without weights installed according to an embodiment of the present invention;

[0030] Figure 2 This is a cross-sectional view of the support component in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of an electric bicycle frame impact test load installed on the frame, according to an embodiment of the present invention.

[0032] Meaning of the labels in the attached diagram:

[0033] 1-Weight support plate; 1.1-First elongated hole; 1.2-Second elongated hole; 1.3-Weight fixing hole; 2-Support column; 2.1-Top threaded hole; 2.2-Lower welding rod; 3-U-shaped base; 3.1-Connecting hole; 3.2-U-shaped groove; 4-Connecting bolt; 5-Fastening screw; 6-Frame; 6.1-Side tube; 6.2-Rear rack bracket; 6.3-Rear swingarm assembly; 6.4-Seat mounting hole; 6.5-Rear swingarm assembly mounting hole; 6.6-Electric bicycle bottom bracket mounting hole; 6.7-Side support mounting welding point; 6.8-Steering column insertion hole; 7-Locking nut. Detailed Implementation

[0034] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0035] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0036] In the description of this invention, unless otherwise explicitly defined, terms such as "setting," "installing," and "connecting" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0037] The present invention will be further described below with reference to embodiments.

[0038] Example:

[0039] The adjustable center of gravity electric bicycle frame impact test load of this embodiment can be used in the impact strength test of electric bicycle frames without a seat tube structure, such as... Figure 1 and Figure 2 The impact test load for the electric bicycle frame in this embodiment includes a weight support plate 1, weights, and two sets of support components. Figures 1 to 3 (The weights are not shown in the diagram), and the support components include a U-shaped base 3, a fastening screw 5, and a support column 2.

[0040] The weight support plate 1 is a rectangular flat plate with a first elongated hole 1.1 at one end. During installation, a bolt passes through the first elongated hole 1.1 and connects to the corresponding seat bucket mounting hole 6.4 on the rear rack bracket 6.2 of the frame 6. A flat washer can be placed on the bolt, positioned between the bottom of the first elongated hole 1.1 and the top of the rear rack bracket 6.2. The installation height of this end of the weight support plate 1 can be adjusted by adding or removing the flat washer between the bottom of the first elongated hole 1.1 and the rear rack bracket 6.2. The other end of the weight support plate 1 has three second elongated holes 1.2. When installed on the frame, the length direction of the first elongated hole 1.1 and the second elongated hole 1.2 is the width direction of the frame, which is also the width direction of the weight support plate 1. The three second elongated holes 1.2 are spaced apart along the length direction of the weight support plate 1. Three rows of weight fixing holes 1.3 are provided on the weight support plate 1 between the first elongated hole 1.1 and the second elongated hole 1.2. The weight fixing holes 1.3 are round holes. In this embodiment, all three rows of weight fixing holes 1.3 are close to the end where the second elongated hole 1.2 is located. The weight fixing holes 1.3 are used to fix the weights. The weights are of a regular shape, specifically a cuboid shape. The weights are provided with corresponding connecting holes. When fixing, the connecting holes on the weights are aligned with the weight fixing holes 1.3, and then fixed by bolts.

[0041] The support components in this embodiment are used to support the two ends of the weight support plate 1.

[0042] In this embodiment, a top threaded hole 2.1 is provided at the upper end of the support column 2. The lower end of the fastening screw 5 is threaded into the top threaded hole 2.1. The height of the fastening screw 5 can be adjusted by rotating it. During connection, at least one locking nut 7 is first connected to the fastening screw 5, and then it passes through the second elongated hole 1.2. The end of the weight support plate 1 will be supported on the locking nut 7 below it. Then, another locking nut 7 is connected to the upper end of the fastening screw 5 and tightened, thereby clamping the end of the weight support plate 1 between the two adjacent locking nuts 7, completing the fixation. During use, the height of the weight support plate 1 can be adjusted by adjusting the height of the fastening screw 5 itself, or by adjusting the connection height of the locking nut 7 on the fastening screw 5, and by adjusting the number of shims between the lower part of the first elongated hole 1.1 and the back hanger bracket 6.2. Of course, the weight support plate 1 should at least be in contact with the upper part of the back hanger bracket 6.2. During use, the fastening screws 5 on the support column 2 can be connected to different second elongated holes 1.2 according to the specific connection position of the support column 2, so as to adapt to different frames 6.

[0043] In this embodiment, the top of the U-shaped base 3 is a flat surface, and a welding connection hole is provided on the top of the U-shaped base 3. The lower end of the support column 2 is provided with a protruding lower welding rod 2.2. The lower welding rod 2.2 is inserted into the welding connection hole and welded together, thereby stably connecting the U-shaped base 3 and the support column 2 into one unit.

[0044] The U-shaped base 3 has a downward-facing U-shaped groove 3.2, the width of which is greater than the width of the side tube 6.1 of the frame 6. In use, the U-shaped base 3 is positioned downwards and snapped onto the side tube 6.1 of the frame 6. Connecting holes 3.1 are provided on both sides of the U-shaped groove 3.2. These connecting holes 3.1 are vertical, slotted holes. During connection, the connecting bolt 4 is inserted into the connecting hole 3.1, and then a lock nut is attached to the end of the connecting bolt 4 and tightened, thereby connecting the U-shaped base 3 to the side tube 6.1 of the frame 6.

[0045] The precise positioning method for mounting the impact test load on the electric bicycle frame in this embodiment includes the following steps:

[0046] S1. Fix the complete electric bicycle with the frame to be tested onto the coordinate measuring machine (CMM). The electric bicycle is in a stable state to avoid affecting the measurement accuracy due to shaking. Measure the surface of the electric bicycle's saddle using a contact or non-contact probe on the CMM to obtain the center position coordinates Xs, Ys, and Zs of the saddle surface. The origin of the coordinates for measuring the center position coordinates of the electric bicycle's saddle surface is selected from characteristic points on the frame 6, such as: the center of the seat bucket mounting hole 6.4 on the rear rack bracket 6.2 of the frame 6, the center of the rear swingarm assembly mounting hole 6.5, the center of the bottom bracket mounting hole 6.6, the side support mounting welding point 6.7, and the center of the steering column insertion hole 6.8, etc.

[0047] Then, the coordinates of the center position of the saddle surface are projected onto the frame 6 using a laser line projector, and the corresponding installation reference points are marked on the frame 6. The X, Y, and Z axes coordinates of the center position of the saddle surface are marked respectively, for example, clear marking points and positioning lines are drawn at the designated positions on the frame 6.

[0048] S2, obtain the mass a of the weight support plate 1, the mass b of the weight, the mass c of the first set of support components, and the mass d of the second set of support components. The total mass of a+b+c+d should be equal to the standard requirement of 70kg. Establish a coordinate system with the center of the surface of the weight support plate 1 as the origin, and calculate the center of gravity coordinates Xw, Yw, and Zw of the frame impact test load using the weighted average method.

[0049] The specific process of calculating the center of gravity coordinates of the chassis impact test load using the weighted average method is as follows:

[0050] With the center of the surface of the weight support plate 1 as the origin of the coordinate system, the length direction of the weight support plate 1 is the X direction of the coordinate system, the width direction of the weight support plate 1 is the Y direction of the coordinate system, and the direction perpendicular to the surface of the weight support plate 1 is the Z direction of the coordinate system.

[0051] The dimensions of the weight support plate 1 are x1mm×y1mm×z1mm, and the dimensions of the weight are x2mm×y2mm×z2mm. When the weight is mounted on the weight support plate 1, the position of the center of gravity of the weight projected onto the surface of the weight support plate 1 is x. b y b The dimensions of the first set of support components are x3mm×y3mm×z3mm. The position of the center of gravity of the first set of support components projected onto the surface of the weight support plate 1 is x. c y c The dimensions of the second set of support components are x4mm×y4mm×z4mm, and the position of the center of gravity of the second set of support components projected onto the surface of the weight support plate 1 is x. d y d .

[0052] Determine the coordinates of the center of gravity of each component:

[0053] a. The coordinate of the center of gravity of the weight support plate 1 is x. a y a z a ;

[0054] b. The coordinates of the center of gravity of the weight are x b y b , Since the weights are mounted on the weight support plate 1, their center of gravity height is... ;

[0055] c. The two sets of support components are irregularly shaped. The x and y axes of the center of gravity of the support components are measured using a weighing method, and the z axis is measured using a suspension method. After measurement, the center of gravity of the first set of support components is obtained by taking the center of the surface of the weight support plate 1 as the origin of the coordinate system. c y c z c and the centroid coordinates x of the second set of support components d y d z d .

[0056] The weighing method involves placing the support assembly on four pressure sensors and recording the forces F1, F2, F3, and F4 applied to each sensor; the total weight of the object G = F1 + F2 + F3 + F4; and its center of gravity coordinates satisfying the following: , L and M are the array sizes of the sensors.

[0057] The suspension method involves suspending the support components from different positions and determining the center of gravity height z by the intersection of gravity lines.

[0058] Finally, the center of gravity coordinate x of the impact test load on the electric bicycle frame was determined. W y W z W for:

[0059]

[0060]

[0061]

[0062] The total mass M = a + b + c + d.

[0063] S3. Secure the frame, then pre-install the impact test load onto frame 6. Before installation, prepare the necessary tools: adjustable wrench, screwdriver, Allen wrench, etc., ensuring the tool specifications and models match the installation requirements and that the tools are intact and usable. Frame 6 should be fully assembled, including the front and rear shock absorption systems and the rear swingarm assembly 6.3. Conduct a comprehensive inspection of all connections on frame 6, paying particular attention to the shock absorption mechanisms and the connections on the rear swingarm assembly 6.3, ensuring reliable connections and normal movement. Frame 6 is for a seatless frame design.

[0064] The specific operating steps are as follows:

[0065] 1. Pre-installation of U-shaped bases 3: Insert the U-shaped grooves 3.2 of the two U-shaped bases 3 into the side tubes 6.1 on both sides of the frame 6, ensuring that the U-shaped grooves 3.2 fit snugly against the side tubes 6.1. Apply pre-tightening force using the connecting bolts 4 connected to the U-shaped bases 3 to ensure that there is no relative slippage between the U-shaped bases 3 and the side tubes 6.1 of the frame 6. At this time, keep the U-shaped bases 3 adjustable in the width direction of the frame 6, and do not fully lock them.

[0066] 2. Installation of weight support plate 1: Align the first elongated hole 1.1 of weight support plate 1 with the mounting hole 6.4 of the seat barrel, insert bolts and connect spring washers and flat washers to form a fixed support point for weight support plate 1.

[0067] 3. Installation of fastening screws 5 and support column 2: The support column 2 is connected to the U-shaped base 3. Two fastening screws 5 are passed through the second long hole 1.2 of the weight support plate 1. Locking nuts 7 are connected to the fastening screws 5. The lower end of the fastening screws 5 is screwed into the upper end of the support column 2. The height of the weight support plate 1 is initially adjusted by rotating the locking nut 7 so that the weight support plate 1 is in a roughly horizontal state.

[0068] 4. Installation and Leveling of the Weights: Fix the weights to the upper surface of the weight support plate 1 with bolts. The bolts for fixing the weights are installed in conjunction with spring washers and flat washers. Place a precision level on the upper surface of the weight support plate 1, and adjust the locking nuts 7 on the two fastening screws 5 to ensure that the levelness of the weight support plate 1 is ≤0.5°.

[0069] S4, Adjust the center of gravity of the impact test load on the electric bicycle frame according to the mounting reference point on frame 6:

[0070] 1. Z-axis (height) adjustment: Simultaneously rotate the locking nuts 7 on the two fastening screws 5, and the flat washer between the bottom of the first long hole 1.1 and the rear hanger bracket 6.2, to adjust the installation height of the weight support plate 1, so that the center of gravity coordinate Zw of the impact test load on the frame is basically aligned with the installation reference point on the frame 6 corresponding to Zs. The height deviation should be ≤5mm. Verify the adjustment accuracy using a laser height measuring instrument or a height vernier caliper. [Note: (The moving distance (L) can be calculated based on the thread pitch (P) and the selected number of turns (N). The calculation formula is: L = P × n.]

[0071] 2. Y-axis (longitudinal) adjustment: Loosen the locking nut 7 on the weight support plate 1 and the bolt connecting it to the mounting hole 6.4 in the seat bucket. Slide the weight support plate 1 along the width direction to adjust its position so that the center of gravity coordinate Yw of the impact test load on the frame is basically aligned with the mounting reference point corresponding to Ys on the frame 6, with a longitudinal deviation ≤5mm. The alignment is verified by emitting a reference line parallel to the longitudinal axis of the frame using a laser locator.

[0072] 3. X-axis (lateral) fine adjustment: If the lateral deviation is >5mm, adjust it in the following way: loosen the bolts that fix the weight, select different positions of the weight fixing holes 1.3 on the weight support plate 1 to re-fix the weight, so that the center of gravity coordinate Xw of the impact test load of the frame is basically aligned with the installation reference point corresponding to Xs on the frame 6, and the lateral deviation is ≤5mm.

[0073] Finally, a laser locator was used to perform a three-dimensional spatial verification of the center of gravity coordinates Xw, Yw, Zw of the impact test load on the frame and the center position coordinates Xs, Ys, Zs of the saddle surface. After confirming that the deviations in the X, Y, and Z directions were all ≤5mm, all connecting parts were then fully locked.

[0074] After installation, shake the electric bicycle frame vigorously to test the impact load and ensure that all connection points are secure. Use a level to confirm that the levelness of the weight support plate is ≤0.5°. Use a laser locator to recheck the three-dimensional positioning error to ≤5mm. Record all adjustment parameters (height of the fastening screw, position of the U-shaped base, and position of the weight fixing holes) for future reference during repeated installations.

[0075] After adopting the technical solution of the present invention, the positioning accuracy of the load center of gravity in the impact test of electric bicycle frame can reach ≤5mm, and the load displacement rate during the impact test can reach ≤5% (the comprehensive displacement amount ≤5mm can be regarded as no displacement phenomenon).

[0076] The technical solution of this invention achieves significantly higher positioning accuracy of the load center of gravity and lower load displacement rate compared to existing methods of fixing the load by binding with ropes and tightening with buckles. To this end, we conducted the following experiments:

[0077] 1. Comparative test on positioning accuracy:

[0078] Experimental method: Ten electric bicycle frames without saddle tubes were selected. The coordinates (Xs, Ys, Zs) of the center position of the saddle surface were measured using a coordinate measuring machine. A 70kg load was installed in three different ways, and the coordinates (Xw, Yw, Zw) of the center of gravity of the load were measured. The three-dimensional positioning deviation was calculated.

[0079] Table 1. Experimental data on positioning and installation accuracy (unit: mm)

[0080] Note: The values ​​in Table 1 represent the overall positioning deviation. ΔX is the deviation in the X direction, ΔY is the deviation in the Y direction, and ΔZ is the deviation in the Z direction.

[0081] Positioning accuracy conclusion:

[0082] Existing rope binding and buckle tightening technology has an average deviation of 35.7mm.

[0083] The existing chain winding + bolt fixing solution has an average deviation of 29.7mm.

[0084] The technical solution of this invention: average deviation 4.8mm

[0085] Analysis of experimental data shows that the positioning accuracy of the present invention is improved by 83.8%-86.6% compared with the prior art.

[0086] 2. Installation stability comparison experiment:

[0087] Experimental method: In accordance with the requirements of GB 17761 standard, an impact test was conducted on the frame, and the three-dimensional displacement of the load of 70kg before and after the test was observed.

[0088] Table 2: Impact test displacement data under 70kg load (unit: mm)

[0089] Note: The values ​​in Table 2 are the combined displacement values. X is the displacement in the X direction, Y is the displacement in the Y direction, and Z is the displacement in the Z direction.

[0090] Installation stability conclusion:

[0091] The existing rope binding and buckle tightening technology has an average displacement of 38.0 mm and a displacement rate of 100%.

[0092] The existing chain winding + bolt fixing technical solution has an average displacement of 20.8mm and a displacement rate of 100%.

[0093] The technical solution of this invention is: average displacement of 1.9 mm and displacement rate of 0%.

[0094] Analysis of the experimental data shows that the displacement of the technical solution of the present invention is reduced by 91% to 95%, and the displacement rate is reduced from 100% to 0%.

[0095] The overall technical effects obtained from the above experiments are compared in Table 3 below:

[0096] Table 3: Comparison of Overall Technical Effects

[0097]

[0098] The conclusion of the above experiment is:

[0099] 1. Breakthrough in positioning accuracy: This invention improves the positioning accuracy from >10mm (measured 29.7mm~35.7mm) to ≤5mm (measured 4.8mm), achieving a 100% compliance rate.

[0100] 2. Significantly improved stability: This invention reduces the displacement rate from 100% to 0%, and the impact displacement is only 5% to 9% of the existing technology.

[0101] 3. Conclusive technical results: Experimental data fully demonstrate that the present invention has achieved breakthrough improvements in positioning accuracy and installation stability, and has significant technical progress.

[0102] The above embodiments of the present invention are not intended to limit the scope of protection of the present invention. The implementation of the present invention is not limited thereto. All other modifications, substitutions or alterations made to the above structure of the present invention based on the above content of the present invention, in accordance with ordinary technical knowledge and common practice in the field, without departing from the basic technical idea of ​​the present invention, shall fall within the scope of protection of the present invention.

Claims

1. An impact test load for an electric bicycle frame with an adjustable center of gravity, characterized in that: The system includes a weight support plate, weights, and two sets of support assemblies. One end of the weight support plate has a first elongated hole for connecting to the seat bucket mounting hole on the rear rack bracket of the vehicle frame, and the other end of the weight support plate has a second elongated hole. The length direction of the first and second elongated holes is the width direction of the vehicle frame. The weights are mounted on the weight support plate, and the mounting position of the weights can be adjusted along the length direction of the vehicle frame. The two sets of support assemblies support both sides of the weight support plate, and each support assembly includes a U-shaped base, a fastening screw, and a support column. The U-shaped base is used to connect to the side tube of the vehicle frame, the support column is vertically mounted on the top of the U-shaped base, the fastening screw is vertically mounted on the upper end of the support column, and the end of the weight support plate is connected to the fastening screw through the second elongated hole. The mounting height of the weight support plate is adjustable.

2. The electric bicycle frame impact test load with adjustable center of gravity according to claim 1, characterized in that: The fastening screw passes through the second elongated hole and is provided with at least two locking nuts. The weight support plate is clamped between two adjacent locking nuts. The connection position of the weight support plate on the fastening screw can be adjusted by adjusting the position of the locking nuts.

3. The electric bicycle frame impact test load with adjustable center of gravity according to claim 1, characterized in that: The U-shaped base has a U-shaped groove with the opening facing downwards. There are connection holes on both sides of the U-shaped groove. When connected to the side tube of the frame, the side tube is located in the U-shaped groove of the U-shaped base and is connected by connecting bolts passing through the connection holes.

4. The electric bicycle frame impact test load with adjustable center of gravity according to claim 1, characterized in that: The weight support plate has a row of more than one row of weight fixing holes between the first long hole and the second long hole, and the weight is located on the weight support plate and fixed through the weight fixing holes.

5. The electric bicycle frame impact test load with adjustable center of gravity according to claim 1, characterized in that: The U-shaped base has a welding connection hole on its upper part, and the lower end of the support column has a lower welding rod. The lower welding rod is inserted into the welding connection hole and welded together.

6. The electric bicycle frame impact test load with adjustable center of gravity according to claim 1, characterized in that: The upper end of the support column is provided with a top threaded hole, and the lower end of the fastening screw is threaded into the top threaded hole.

7. A precise positioning method for mounting the impact test load on the frame of an electric bicycle as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Fix the complete electric bicycle with the frame to be tested onto the coordinate measuring machine. Obtain the center position coordinates Xs, Ys, and Zs of the saddle surface of the electric bicycle through the coordinate measuring machine. Project the center position coordinates of the saddle surface onto the frame using a laser line projector and mark the installation reference point at the corresponding position on the frame. S2, obtain the mass a of the weight support plate, the mass b of the weight, the mass c of the first set of support components and the mass d of the second set of support components, establish a coordinate system with the center of the surface of the weight support plate as the origin, and calculate the center of gravity coordinates Xw, Yw and Zw of the frame impact test load by weighted average method; S3, Fix the frame, pre-install the frame impact test load onto the frame, and ensure that the levelness of the weight support plate of the frame impact test load is ≤0.5°; S4. Based on the mounting reference point on the frame, adjust the mounting height of the weight support plate so that Zw corresponds to Zs; adjust the connection position between the first elongated hole and the seat mounting hole and the connection position between the second elongated hole and the fastening screw so that Yw corresponds to Ys; adjust the mounting position of the weight along the length of the frame so that Xw corresponds to Xs; finally, make the center of gravity coordinate position of the frame impact test load correspond to the center position coordinate of the saddle surface, and then tighten all the connection parts of the frame impact test load.

8. The precise positioning method according to claim 7, characterized in that: In step S4, the final adjustment is made so that the deviations of the center of gravity coordinates of the frame impact test load from the center position coordinates of the saddle surface in the X, Y, and Z directions are all ≤5mm.

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