Shock absorber assembly for radio-controlled scale model vehicles

Abstract

A shock absorber assembly for radio controlled scale model vehicles defines a main compression chamber and a side bypass channel, fluidly connected by a series of ports along their lengths. A piston reciprocates within the main compression chamber, with fluid flowing through the ports and bypass channel as the piston moves. During compression, fluid escapes from in front of the piston head via the ports, bypasses the head through the side bypass channel, and re-enters the main compression chamber behind the piston head. The assembly provides variable damping based on the piston's position within the chamber, adapting to different levels of impact to improve vehicle stability and control.

Description

Shock Absorber Assembly for Radio-Controlled Scale ModelVehiclesField of the Invention

[0001] The invention relates generally to shock absorbers and, more particularly, to a shock absorber assembly designed for use in scale model vehicles, such as radio controlled racing cars. The invention focuses on providing a compact, efficient damping mechanism that adapts to varying levels of impact and dynamic loads encountered during high-speed or high-impact manoeuvres, thereby enhancing stability, control, and durability of the vehicle's suspension system.Background of the Invention

[0002] A shock absorber is a component in a vehicle’s suspension system, designed to manage and control the impact of road surface irregularities. It plays an essential role in enhancing ride comfort, vehicle stability, and overall safety.

[0003] The primary function of a shock absorber is to absorb and dampen the kinetic energy generated when a vehicle encounters bumps, potholes, or other road disturbances. It achieves this by converting kinetic energy into heat, which is dissipated through the shock absorber’s internal components.

[0004] Typically, a shock absorber consists of a piston that moves within a cylinder filled with hydraulic fluid. As the vehicle’s suspension compresses or extends in response to road irregularities, the piston moves through the fluid, creating resistance and controlling suspension motion. This controlled movement helps prevent excessive bouncing and ensures that the tyres maintain optimal contact with the road surface, contributing to improved handling, traction, and overall driving experience. Shock absorbers are crucial for maintaining a smooth and stable ride, and their effectiveness is essential for both driver comfort and vehicle safety.

[0005] Reduced-scale model racing cars, such as 1 / 8th scale models, also use suspension shock absorbers, typically filled with silicone fluid of a specified viscosity. However, modern miniaturised model racing cars present unique challenges due to their extreme power-to-weight ratios, especially in high-performance electric models.These miniature cars can reach speeds exceeding 80 km / h and perform jumps over 10 metres long.

[0006] Ensuring adequate shock absorption for miniaturised model racing cars is challenging due to their compact size. The difficulty lies in achieving a balance; their shock absorption may be over-damped, resulting in insufficient wheel responsiveness to road undulations, causing a loss of tyre grip, or under-damped, leading to suspension bottoming out, which causes excessive wear or potential damage to the chassis, as well as slowing the car as the chassis underside scrapes the track surface.

[0007] In miniaturised racing cars, oil-filled shock absorbers absorb kinetic energy generated by movement, converting it primarily into heat through friction as the piston moves through the silicone oil. The amount of damping, or resistance to piston movement, is determined by a combination of oil viscosity.

[0008] Some arrangements also use holes in the piston head whereby the amount of damping and resistance is controlled by the number and diameter of the holes.

[0009] Thus, more damping can be achieved by increasing the oil’s viscosity (making it thicker) or reducing the number and / or size of holes in the piston head. Conversely, less damping can be obtained by decreasing the viscosity or increasing the number and / or size of these holes.

[0010] Higher damping in compression creates greater pressure ahead of the moving piston, as oil flow is restricted through smaller or fewer holes. According to the Hagen - Poiseuille equation, halving the diameter of a piston hole results in 16 times less flow at the same pressure. Therefore, it might seem advantageous to use a piston with smaller holes and thicker oil for miniature cars subjected to large jumps, considering the impact forces at both take-off and landing. However, this approach has drawbacks. Bernoulli’s equation dictates that when fluid moves from a larger chamber into a smaller diameter hole or pipe, there is a drop in pressure and an increase in velocity. In a shock absorber, high pressure above the piston head can lead to a significant pressure drop below the piston head, potentially resulting in cavitation andvacuum effects. These phenomena severely impair the shock absorber’s effectiveness.

[0011] Cavitation can cause lag or reduced damping, while the vacuum effect may draw in air and debris, compromising the integrity of the shock shaft seals. The ingress of air thins the oil, reducing effective friction and causing fade or diminished damping. Furthermore, most suspension oils, including those used in full-sized vehicles, can contain up to 20% air by volume due to processing and transport. While full-sized shock absorbers can mitigate cavitation and vacuum effects through pressurisation and specialised seals, such solutions are not economically feasible for miniature racing, necessitating alternative approaches.

[0012] The present invention aims to provide a shock absorber for miniaturised racing cars that addresses or substantially ameliorates at least some of the deficiencies of the prior art, or at least offers an alternative solution.

[0013] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.Summary of the Disclosure

[0014] The described shock absorber assembly provides a compact and efficient damping mechanism suitable for miniaturised model vehicles. The assembly includes a main compression chamber and a side bypass channel, fluidly connected by a series of ports distributed along their lengths. A piston reciprocates within the main compression chamber, with a piston head configured to enable fluid flow through the ports during compression and extension cycles.

[0015] In operation, fluid flows from in front of the piston head to the bypass channel and back into the main compression chamber behind the piston head, with the number of active ports varying according to the piston’s position. This arrangement modulates the damping effect dynamically, providing varied resistance in response to different levels of compression.

[0016] The assembly may include an internal dividing wall that separates the main compression chamber from the bypass channel, with ports distributed along thedividing wall to facilitate controlled fluid flow. The shock absorber may include an insert tube that defines the internal dividing wall and enables integration with existing cylinders.

[0017] The shock absorber's ports define multiple damping zones along the length of the compression chamber which may include a ride zone, an expanded compression zone, and a retracted compression zone. Each zone influences the damping characteristics based on the number and arrangement of ports in front of and behind the piston head.

[0018] Flow control mechanisms are preferably positioned between adjacent ports to refine the damping characteristics by selectively adjusting fluid flow. These mechanisms may include variable-thickness inserts within the bypass channel, which modify the flow rate according to the thickness of the inserts. This configuration enables the shock absorber to provide effective damping across a wide range of operating conditions, enhancing stability and responsiveness in high-performance applications.

[0019] According to one aspect, there is provided a shock absorber defining a main compression chamber and a side bypass channel, fluidly connected by a plurality of ports along their lengths and comprising a piston reciprocating within the main compression chamber, wherein fluid flows through the bypass channel in response to the piston’s position, providing variable damping based on compression or extension. This configuration enhances control over suspension response by modulating fluid flow as the piston moves, allowing improved stability and handling.

[0020] In an embodiment, the shock absorber comprises an internal dividing wall that separates the main compression chamber from the side bypass channel, with ports defined through the dividing wall, and a piston head with a non-circular cross-section configured to fit against the dividing wall, thereby maximising the cross-sectional area of the piston head within the confines of a cylindrical shock absorber.

[0021] The shock absorber may include an insert tube configured to fit within an external cylinder, where the insert tube defines both the ports and the internal dividingwall. This design offers compatibility with existing shock absorber structures, allowing for retrofitting and ease of assembly.

[0022] The ports define multiple zones along the compression chamber’s length which may include a ride zone where fluid flow is balanced, a retracted compression zone where damping is increased, and an expanded compression zone providing heightened resistance during extension. This zoned configuration enables adaptive damping depending on the compression state of the shock absorber.

[0023] In an embodiment, the shock absorber includes four ports defining the zones, allowing for precise control over fluid dynamics at each position of the piston head. This arrangement offers a finely tuned damping response that can adapt at both noncompressed and compressed suspension positions.

[0024] Preferably, flow control mechanisms are positioned between adjacent ports. Each mechanism may comprise variable-thickness inserts that are insertable along the bypass channel to adjust the flow rate. This feature allows for tailored damping characteristics at each zone. Each insert may include a central variable-thickness portion and side portions, with side connectors in the bypass channel configured to engage the side portions.

[0025] Preferably, at least some of the ports are elongate and oriented across the main compression chamber, allowing for immediate fluid flow adjustment as the piston head passes each port. This positioning enables faster response times in damping, providing smoother handling. However, at least one port may be angled non- orthogonally with respect to the longitudinal axis of the main compression chamber, allowing for a graduated fluid flow effect. This angled configuration helps to avoid sudden changes in damping force, contributing to a smoother transition between compression and extension movements, especially for compression at the distal end of the main compression chamber.

[0026] In embodiments, the shock absorber may comprise a speed sensitive insert which varies damping characteristics depending on the speed of the piston.

[0027] Other aspects of the invention are also disclosed.Brief Description of the Drawings

[0028] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0029] Figure 1 shows an internal side view of the shock absorber 100, illustrating the main compression chamber 101 , the side bypass channel 102, and the reciprocating piston 104.

[0030] Figure 2 shows a schematic view of the shock absorber 100 under extended compression, detailing fluid flow through the main compression chamber 101 , side bypass channel 102, and ports 103 relative to the piston head 106.

[0031] Figure 3 shows the shock absorber 100 with the piston head 106 positioned within the ride zone 1 12B, demonstrating fluid flow through the ports 103 in balanced conditions.

[0032] Figure 4 shows an embodiment of the piston head 106 with a generally kidneyshaped cross-section, configured to fit against the internal dividing wall 1 10.

[0033] Figure 5 shows an exploded view of the shock absorber 100, including the external cylinder 109 and the insert tube 1 1 1 , which defines the internal dividing wall 1 10 and ports 103.

[0034] Figure 6 shows the assembled shock absorber 100, with the insert tube 1 1 1 positioned within the external cylinder 109.

[0035] Figure 7 shows a disassembled view of the shock absorber 100.

[0036] Figure 8 shows a magnified view of a speed sensitive insert 124 of the shock absorber 100 in accordance with an embodiment.Description of Embodiments

[0037] Figure 1 shows an internal side view of a shock absorber 100. The shock absorber 100 is generally elongate, defining a distal end 107 and a proximal end 108. With reference to Figure 2, the shock absorber includes a main compression chamber 101 and a side bypass channel 102 along its length. A plurality of ports 103 fluidly connect the main compression chamber 101 and the side bypass channel 102 along their lengths.

[0038] The shock absorber 100 has a piston 104 that reciprocates within the main compression chamber 101 . The piston 104 includes a compression rod 105 acting on a piston head 106. As shown in Figure 1 , the proximal end of the compression rod105 may be threaded for direct attachment to a threaded socket of a suspension assembly in a scaled-down radio controlled vehicle.

[0039] As illustrated in Figure 2, as the piston head 106 moves towards the distal end 107 fluid 121 escapes via ports 103 located in front of the piston head 106, bypasses the piston head 106 through the side bypass channel 102, and returns to the main compression chamber 101 via ports 103 positioned behind the piston head 106.

[0040] As the piston head 106 advances towards the distal end 107, the number of ports 103 in front of the piston head 106 decreases, while the number of ports 103 behind the piston head 106 increases, thereby dynamically affecting the damping effect of the shock absorber 100 depending on the piston head's 106 relative position along the main compression chamber 101.

[0041] The fluid may be an oil-based substance, such as silicon-based oil, and the shock absorber 100 may be evacuated of air.

[0042] The shock absorber 100 may include an internal dividing wall 110 that separates the main compression chamber 101 from the side bypass channel 102 and defines the ports 103. As shown in Figure 6, the piston head 106 may have a noncircular cross-section to fit against the internal dividing wall 1 10. In the embodiment shown in Figure 4, the piston head 106 is generally kidney-shaped. Preferably, the shock absorber 100 comprises only one side bypass channel 102. Figure 7 shows an exploded representation of the shock absorber 100 illustrating the generally kidney - shaped cross-section of the piston head 106. The piston head 106 may define a socket 107 for the engagement of the threaded compression rod 105. In the embodiment shown, the piston head 106 may comprise a plurality of relief apertures 122 therethrough to fluid to pass through the piston head 106 to influence damping characteristics. Specifically, the relief apertures 122 would create an additional pathway for fluid movement, effectively reducing the resistance to the piston head’s106 motion and resulting in a softer or lower damping force.

[0043] In certain embodiments, the shock absorber 100 may be assembled from an external cylinder 109 and an insert tube 1 1 1 that fits within the cylinder 109, as shown in Figure 5, to form the assembled shock absorber 100 depicted in Figure 6. The insert tube 1 1 1 defines the internal dividing wall 1 10 with the ports 103. The insert tube 1 1 1 can be retrofitted into cylinders 109 of existing shock absorbers 100.

[0044] The ports 103 may form various zones 1 12 between them. In the embodiment shown, the shock absorber 100 includes four ports 103: a proximal end port 103A and an intermediate proximal port 103B that define an expanded compression zone 1 12A between them; an intermediate distal port 103C that defines a ride zone 1 12B between it and the intermediate proximal port 103B; and a distal end port 103D that defines a retracted compression zone 1 12C between it and the intermediate distal port 103C.

[0045] In the ride zone 1 12B, fluid flow restriction either side of the piston head 106 is substantially equal or balanced. However, in the compressed zones 1 12A and 1 12C, fluid flow restriction either side of the piston head is unequal or unbalanced. Specifically, when the piston head 106 is within the ride zone 1 12B, as shown in Figure 3, there may be an equal number of ports 103 in front of and behind it (or at least ports 103 defining substantially equal cross sections in front and behind the piston head 106). In this position, fluid can flow substantially equally through the two ports 103 in front of and the two ports behind the piston head.

[0046] When the suspension assembly 100 is compressed, and the piston head 106 is in the retracted compression zone 1 12C, fluid flow is restricted as only the distal end port 103D is in front of the piston head 106, increasing the damping effect in this zone. Similarly, when the piston head 106 is in the expanded compression zone 1 12A, there is only the proximal end port 103A behind the piston head 106, restricting fluid flow and thereby increasing the damping effect.

[0047] Accordingly, the damping effect is reduced within the ride zone 1 12B and increased in the adjacent retracted compression zone 1 12C and expanded compression zone 1 12A due to fluid flow restrictions.

[0048] As shown in Figure 1 , the shock absorber may include flow control mechanisms 1 13 between adjacent ports 103. In the embodiment illustrated, the flow control mechanisms 1 13 include a proximal flow control mechanism 1 13A between the end proximal port 103A and the intermediate proximal port 103B, an intermediate flow control mechanism 1 13B between the intermediate proximal port 103B and the intermediate distal port 103C, and a distal flow control mechanism 1 13C between the intermediate distal port 103C and the end distal port 103D.

[0049] These flow control mechanisms 1 13 regulate fluid flow between the ports 103, thereby adjusting the operational characteristics of the shock absorber 100.

[0050] In the embodiment shown, the flow control mechanisms 1 13 consist of variable-thickness inserts 1 14 placed along the bypass chamber, where the thickness of each insert 1 14 affects the flow rate. Each insert 1 14 may include a central variable-thickness portion 1 15 and side portions 1 16. The bypass channel 102 may feature side connectors 1 17 designed to engage the side portions 1 16, positioning the variable-thickness portions 1 15 between them to control fluid flow. In the assembly depicted in Figure 5, where the shock absorber 100 includes the insert tube 1 1 1 , the insert tube 1 1 1 may have side connectors 1 17 that engage the respective side portions 1 16 of the inserts 1 14. The insert 1 14 may take the form of shaped plastic buttons that fit between the side connectors 1 17. These inserts 1 14, with a variable-thickness central portion 1 15, create a constriction along the bypass channel 102 depending on their thickness, thereby impacting fluid flow through the channel 102.

[0051] For increased damping effect, a thicker insert 1 14 may be selected to decrease the cross-sectional area of the bypass channel 102 between adjacent ports 103, reducing fluid flow.

[0052] To enhance damping at the extreme retracted and expanded positions of the shock absorber 100, thicker inserts 1 14 may be used for the proximal flow control mechanism 1 13A and distal flow control mechanism 1 13C, while a thinner insert 1 14 may be used for the intermediate flow control mechanism 1 13B for faster response rate control.

[0053] It should be noted that the insert 114 may restrict the side bypass channel 102 cross-section in other ways other than via thickness, such as by a variable number of ports or channels or configured ports or channels.

[0054] The ports 103 may be elongated and oriented across the chamber 101 and channel 102 so that their function takes effect immediately as the piston head 106 passes each port.

[0055] However, one or more ports 103 may also be arranged at an angle for a more graduated response. In this configuration, the end distal port 103D is angled (i.e., non-orthogonal to the longitudinal axis of the main compression chamber), allowing a graduated fluid flow effect, particularly at the distal end of the main compression chamber 101 where no further ports 103 exist and considering the incompressible nature of the fluid.

[0056] An end cap 1 18 may enclose the distal end 107 of the cylinder 109, providing a connection aperture 119 for attaching to the suspension assembly of the scaled- down radio controlled vehicle. A backplate 120 may enclose the proximal end 108 of the cylinder 109.

[0057] Figures 7 and 8 show wherein the shock absorber 100 is speed sensitive wherein the damping characteristics thereof depend on the speed of the piston head 106. Specifically, Figure 8 shows the inclusion of a speed sensitive insert 124 which may comprise a baseplate 125 supported between side portions 127 that fit within the side connectors 117 and from which a plurality of flexible fingers 126 (such as of rubber or silicon fingers 126) extend into the pathway defined between the side connectors 1 17. Fluid flowing across the fingers 126 causes them to deflect, thereby reducing the constriction and resistance to fluid flow.

[0058] As such, during high-speed movements of the piston head 106, consequential high fluid flow rate across the fingers 126 causes them to flex and thereby reduce their effective cross-section and fluid flow resistance, thereby allowing for faster responses. However, during slow speed movements, the fluid flow would be insufficient to deflect the fingers 126 substantially, thereby increasing fluid flow resistance and resulting in slower responses.

[0059] In an exemplary method of use, the shock absorber 100 may be installed within a suspension assembly of a scaled-down radio controlled vehicle. To illustrate, the following steps describe how the shock absorber 100 operates during dynamic conditions encountered by the vehicle.

[0060] Initially, the shock absorber 100 is positioned such that the piston head 106 is in the ride zone 1 12B, where an equal number of ports 103 are located in front of and behind the piston head 106. In this position, as shown in Figure 3, fluid flow is balanced across both sides of the piston head 106, allowing for a smooth, moderate damping effect suitable for typical driving conditions and minor surface irregularities.

[0061] As the vehicle encounters a larger obstacle, the suspension compresses, driving the piston head 106 further towards the retracted compression zone 1 12C. In this zone, only a single distal end port 103D remains in front of the piston head 106, while multiple ports 103 are located behind it. This arrangement restricts fluid flow, increasing the damping effect as the shock absorber 100 resists the rapid compression, thereby preventing the suspension from bottoming out.

[0062] Conversely, when the vehicle bounces up or becomes airborne, the piston head 106 may advance into the expanded compression zone 1 12A. In this position, only the proximal end port 103A remains behind the piston head 106, restricting fluid flow from behind. This setup also increases the damping effect during extension, reducing oscillations and enhancing vehicle stability.

[0063] The flow control mechanisms 1 13 situated between adjacent ports 103 may be used to regulate fluid flow by selectively restricting or allowing passage based on the configuration of the variable-thickness inserts 1 14. For example, as the piston head 106 moves through different zones, the central variable-thickness portions 1 15 of the inserts 1 14 create controlled constrictions along the side bypass channel 102, thereby modulating the overall damping response.

[0064] In cases where the shock absorber 100 operates under extreme conditions, such as high jumps or rapid manoeuvres, the damping can be adjusted by selecting inserts 1 14 of varying thicknesses for the proximal flow control mechanism 1 13A, the intermediate flow control mechanism 1 13B, and the distal flow control mechanism113C. For higher damping during severe compression, a thicker insert 114 may be positioned at the proximal or distal flow control mechanisms, as required.

[0065] This exemplary method of use demonstrates how the shock absorber 100 adapts to varying driving conditions by modulating fluid flow through the main compression chamber 101 and side bypass channel 102. The strategic configuration of ports 103 and flow control mechanisms 1 13 ensures that the shock absorber 100 provides optimised damping performance across a range of vehicle applications, contributing to improved handling, stability, and durability.

[0066] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practise the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed as obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.

Claims

Claims1 . A shock absorber defining a main compression chamber, a side bypass channel and a series of ports fluidly connecting the main compression chamber and the side bypass channel along their lengths and comprising a piston head reciprocating within the main compression chamber, wherein, as the piston head moves along the main compression chamber, fluid escapes via a subset of the ports in front of the piston head, bypasses the piston head via the side bypass channel, and returns to the main compression chamber via a subset of the ports behind the piston head.

2. The shock absorber of claim 1 , wherein the shock absorber further comprises an internal dividing wall separating the main compression chamber and the side bypass channel, the internal dividing wall having the ports therethrough, and wherein the piston head defines a non-circular cross-section configured to fit against the internal dividing wall.

3. The shock absorber of claim 1 , further comprising an insert tube configured to fit within a cylinder and defining the ports and the internal dividing wall.

4. The shock absorber of claim 1 , wherein the ports define zones along the length of the main compression chamber, the zones comprising a ride zone wherein fluid flow restriction either side of the piston head is substantially balanced and compressed zones wherein fluid flow restriction either side of the piston head is unbalanced.

5. The shock absorber of claim 4, wherein the shock absorber comprises four ports defining the zones between them.

6. The shock absorber of claim 1 , wherein the shock absorber comprises flow control mechanisms between adjacent ports.

7. The shock absorber of claim 6, wherein each flow control mechanism comprises a variable-thickness insert insertable along the bypass channel, the thickness of the insert affecting the flow rate.

8. The shock absorber of claim 7, wherein each insert defines a central variablethickness portion and side portions, and wherein the bypass channel comprises side connectors configured to engage the respective side portions.

9. The shock absorber of claim 8, further comprising an insert tube configured to fit within a cylinder and defining the ports and the internal dividing wall wherein the internal dividing wall comprises the side connectors.

10. The shock absorber of claim 1 , wherein at least a subset of the ports are elongate and oriented across the main compression chamber.1 1 . The shock absorber of claim 10, wherein at least one port is elongate and oriented non-orthogonally with respect to a longitudinal axis defined by the main compression chamber.

12. The shock absorber of claim 1 , further comprising a speed sensitive insert in the bypass channel comprising a plurality of flexible fingers which deflect under fluid flow effect through the bypass channel.

13. A method of operating a shock absorber according to claim 1 , the method comprising: positioning the shock absorber within a suspension assembly; and controlling fluid flow between the main compression chamber and the side bypass channel to modulate damping in response to the piston’s position along the main compression chamber.

14. The method of claim 13, wherein the fluid flow control further includes using flow control mechanisms positioned between adjacent ports to adjust the damping characteristics by varying the flow rate through the bypass channel.

15. The method of claim 14, wherein each flow control mechanism comprises a variable-thickness insert that modulates fluid flow based on the thickness of the insert positioned along the bypass channel.

Images