GB2030527A

GB2030527A - Go-kart chassis

Info

Publication number: GB2030527A
Application number: GB7930123A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-05-30
Filing date: 1979-08-30
Publication date: 1980-04-10
Also published as: GB2030527B

Abstract

A go-kart chassis is described having front and rear sub-frames joined by at least one link member (46, 48) having a first degree of stiffness when bent in a plane containing the two central axes of the two tubes (46, 48) and a second lower degree of stiffness when bent in a plane perpendicular to the first. The members (46, 48) are terminated in cylindrical ends for fitting into sleeves (20, 22 and 44) of the respective subframes. Adjustment of the stiffness is effected by twisting the link (46, 48) until the required stiffness is obtained. If after 90 DEG of twist insufficient change in stiffness has been achieved, the struts can be replaced with others having more or less stiffness. <IMAGE>

Description

SPECIFICATION Go-kart chassis Field of invention This invention concerns go-karts and in particular an improved form of chassis for go-karts.

Background to the invention The regulations concerning the construction of go-kart chassis stipulate that there must not be any form of suspension between the wheels and the chassis and reliance must be placed on the natural resilience of the chassis members to provide a given degree of suspension or springing as between at least the front and rear wheels.

With this in mind go-karts have been constructed with particular circuits and tracks in mind since certain tracks will allow a higher degree of resilient deformabilitythan others. Howeverthis means that a go-kart driver must have a variety of go-karts available to him if he wishes to optimise his performance on different tracks and even to optimise on different conditions obtaining on a single track. This considerably increases the cost of go-kart racing and it is with this in mind that the present invention proposes an improved form of go-kart chassis construction which conforms to the regulations of the sport but allows the driver or his team to adjust the chassis response as required.

The invention According to the present invention a go-kart chassis comprises a rear sub-frame, front sub-frame and at least one replaceable or adjustable member joining the front sub-frame to the rear sub-frame.

In practice it is envisaged that two identical struts will join the front and rear sub-frames together, the two replaceable struts being located on opposite sides of the chassis. Preferably a range of pairs of replaleable struts are provided each pair having a unique degree of stiffness so that different pairs can be selected to produce different degrees of stiffness forthe overall chassis thereby allowing a skilled driver or team to optimise the response of the chassis to any particular track or track condition.

Alternatively and preferably each replaceable strut has one degree of stiffness in a second transverse axis and means is provided for adjusting the orientation of each of the struts so that the predominant stiffness of each of the struts is either one or the other or a combination of the two degrees of stiffness possessed by the strut.

Whilst it is conceivable that under some circumstances one of the struts may be adjusted so as to exhibit a different degree of stiffness from the other it is normally envisaged that both of the struts will be adjusted so as to exhibit identical degrees of stiffness.

Preferably the opposite ends of each of the replaceable struts fit into recesses in the front and rear sub-frames and to allow the orientation of the replaceable strut to be selected and maintained, preferably at least one end of the strut is splined and the recess into which it fits is correspondingly splined. Preferably both ends of each strut are splined and both of the recesses into which the two ends of the strut fit are splined as well.

Alternatively the replaceable strut may be in the form of a hollow tube and the front and rear sub-frames include protruding spigots which fit into the ends of the strut and at least one end of the strut and one of the spigots and preferably both ends and both spigots are splined to allow the orientation of the strut to be selected and maintained.

Alternatively one end of each strut may be adapted to receive a spigot and the other end is adapted to be fitted into a recess and appropriate spigots and recesses are provided on the front and rear sub-frames or vice versa so as to receive the ends of the strut accordingly. As before either one or both of the inter-engagements between a strut and a sub-frame is a splined joint and preferably the inter-engagement of both ends constitutes a splined joint.

In an alternative arrangement a castellated sleeve may be provided on each of the sub-frames and the ends of the replaceable strut are adapted to be fitted into the castellated sleeve and secured in position by means of bolts which cannot pass through the sleeve and which are received in appropriately screw-threaded bores in opposite ends of thereby placeable strut. By providing the castellations at the end of the sleeve into which the strut is fitted and by providing at least one radial protrusion and preferably two diametrically opposite radial protrusions from the surface of the sleeve which when the latter is tightened home into the sleeve must occupy one or one pair of the castellations, so any particular chosen orientation of the strut can be maintained.

Adjustment of the orientation and therefore the stiffness of the strut is simply effected by slackening off the retaining bolt or other retaining device and adjusting the orientation of the strut and reassembling so that the splines interfit differently or different castellations or pairs of castellations are engaged by the radial protrusion or protrusions.

Preferably the replaceable strut comprises an oval cross-section tube.

Alternatively a rectangular cross-section tube may be used.

An alternative form of construction for a replaceable strut in accordance with the invention comprises a pair of tubes arranged with their axes parallel and welded along the line of touching between the two tubes. Either a continuous weld or a plurality or separate discrete welds may be used. It is merely necessary to hold the two tubes together.

In this alternative form of construction, the ends are preferably retained in circular section bushes having an internal diameter sufficient to accept the maximum diameter of the two sde by side tubes and which include the end joining sections of the strut to allow the strut to be secured to the front and rear sub-frames.

A further alternative form of construction comprises a circular section tube having integrally formed therewith or welded thereto one or more radial fins, the stiffness of the composite strut being dependent on whether the fin is parallel or perpendicular to the plane of bending.

In a preferred form of this said further alternative form of construction, a circular section tube is cut in half on a diameter of its cross-section and the two halves are welded on opposite sides of a plate so as to reconstitute a generally circular cross-section tube having two radially opposed fins at opposite ends of a diametrically extending plate.

Whatever form of construction is employed, the replaceable member may be formed from mild steel but is preferably formed from a good quality high tensile chromium molybdenum alloy steel or from titanium.

Where high tensile steels are used, preferably an argon gas shield is used around all joints which are electrically welded.

Alternatively a spring steel may be used to British Specification EN45. If such a material s used then it is envisaged that bolted connections would be required between the ends of the strut and the front and rear sub-frames instead of welded butts.

Where two circular section tubes are welded together and retained in circular end bushes which are adapted to be joined to the front and rear sub-frames the tubes are preferably formed from a steel to Specfication SAE4130. Alternatively from a steel under the designation T45.

Where the opposite ends of the strut are received in tubular members of sleeves the latter are preferably formed from a steel similarto British Standard EN19.

The invention has so far been described with reference to replaceable struts which have to be dismantled or partially dismantled from their mountings on the front and rear sub-frames to allow a change in orientation to be effected thereby to alter the stiffness thereof. However it is to be understood that the invention is not limited to such struts and includes within its ambit struts having the stiffness characteristics required by the invention which are rotatable about their elongate axes relative to the front and rear sub-frames whilst located in position and joining the front and rear sub-frames together so that no dismantling or partial dismantling of the chassis has to occurto allow adjustment to be effected.In order to avoid tampering with the settings, preferably the end of each strut includes a recess into which a special tool can be inserted to allow the strut to be rotated. The tool may be carried on the chassis in which case provision must be made for retaining the tool thereon or the tool can be retained in the pits or by the team or by the driver so as to be readily available should it become necessark to change the stiffness characteristics of the chassis at short notice.

Although it is obviously desirable that the orientation of the struts should be adjustable both quickly and easily, it is also important that the orientation does not alter whilst the go-kart is in use and with this in mind positive locking means is a preferred feature even where means is provided for turning the strut so as to alter its stiffness characteristics without any dismantling or partial dismantling of the joints between the strut and the rear and sub-frames.

A positive lock may for example be provided by means of an axially slideable sleeve having a plurality of slots therearound into which a radial protrusion on the strut can fit and which is resiliently urged axially in a direction to cause the said radial protrusion to enter a slot and thereby prevent rotation of the strut relative to the sleeve. The necessary restraint is then obtained by non-rotatably mounting the sleeve relative to the sub-frame.

The invention will now be described by way of example with reference to the accompanying drawings.

In the drawings Figure 1 is a plan view of a rear sub-frame for a go-kart chassis, Figure2 is a third angle projection side elevation of the sub-frame of Figure 1, Figure 3 is a third angle projection of the other side elevation of the rear sub-frame, Figure 4 is a plan view of one half of a front sub-frame adapted to be fitted to the rear sub-frame in accordance with the invention but which is drawn to an enlarged scale, Figure 5is a side elevation of the front sub-frame shown in Figure 4, Figure 6 is a side view of one of the two side struts which serve to join the front and rear sub-frames together, Figure 7 is a cross-section on the line A-A of Figure 6, Figure 8 is an end view of one of the bushes which are welded to opposite ends of the strut, and Figure 9 is a cross-section through the end bush shown in Figure 8.

Detailed description of the drawings The general form of a go-kart chassis constructed from front and rear sub-frames is shown in Figures 1 to 5 inclusive. In Figures 1 to 3, the rear sub-frame is shown formed from a single length of tube 10 which is curved around in the form of a U to define the rear and side struts of the rear sub-frame. The two limbs of the U-shape are bent inwardly at 12 and 14 and are curved at their remote ends at 16 and 18 respectively at which point they are welded to a pair of tubular bushes 20 and 22 respectively. A transverse tube 24 is similarly welded to the two bushes 20 and 22 and extends therebetween to close off the front of the rear sub-frame.

A strengthening transverse strut 26 extends between the two opposite sides of the sub-frame and an engine mounting strut 28 extends in a generally front to back direction between the reinforcing transverse strut 26 and the rear section of the U frame 10.

Mounting brackets denoted by 30 and 32 respectively in Figures 2 and 3 are welded or otherwise secured to the two limbs of the U-shaped tubular member 10 to which the rear axle and engine drive etc. are attached.

The front sub-frame comprises a generally Ushaped tube 34 only one half of which is shown in Figure 4. The other half is symmetrical to that shown.

The forward end of the front su b-frame is formed by the crown of the generally U-shaped member 34 and the rearwardly extending limbs, one of which is shown in Figure 4 and is denoted by reference numeral 36, constitutes supports for steerable wheel mountings.

As best seen in FigureS, a second similar U-frame is spaced from the frame 34 and as shown in Figure 5 is denoted by reference numeral 38. It is secured to the U-shaped frame 34 by means of a spacer strut 40 and the rearward ends of the second U-shaped frame 38 provide upper supports at 42 for the steerablewheel mountings.

The front sub-frame is securable to the rear sub-frame by means of two struts one of which is shown in Figure 6 which extend between the tubular bushes 20 and 22 of the rear sub-frame and two similar tubular bushes carried by the front sub-frame and two similar tubular bushes carried by the front sub-frame one of which is shown in Figure 4 and is denoted by reference numeral 44. The two bushes carried by the front sub-frame are located at the ends of two rearwardly extending parallel struts one of which is shown in Figure 4 at 46.

As shown in Figures 6 and 7, the strut which joins the front and rear sub-frames together is in fact formed from two circular cross-section tubes 46 and 48 which are welded at intervals along their joining line at 50, 52 and 54. This prevents the two tubes from moving relative to one another and the strut possesses a first degree of stiffness when bent in a plane containing the two central axes ofthe two tubes and a second much lower stiffness when bent in a plane perpendicular to the first.

The two ends of the tubes 46 and 48 are held captive in cylindrical bosses 54 and 56 respectively and are welded therein.

The construction of the bosses 54 and 56 is similar and that of boss 54 is shown in more detail in Figures 8and9.

The boss includes two circular recesses in the form of a figure 8 marked 56 and 58 respectively, the diameters of which are just sifficient to allow the ends of the tubes 46 and 48 to be pushed thereinto and welded in position.

The end of the bush beyond the two cylindrical recesses 56 and 58 includes a central screw-threaded bore 60 and a transverse bore 62. To facilitate securing in position, the leading edge of the boss is chamfered as at 64 and is formed with a reduced diameter section at 66 relative to the larger diameter section of the region containing the two cylindrical recesses 56 and 58.

Referring back to Figure 1,the boss 54 is adapted to be fitted into one of the tubular bushes 20 and 22, the diameter of the reduced diameter section 66 conforming to the internal diameter of the bush 20 or 22 and the shoulder between the reduced diameter section 66 and the remainder of the boss 54 preventing the boss from being pushed completely through the boss 20 or 22.

The boss 54 is held in position in the bush 20 or 22 by means of a bolt (not shown) the head of which cannot pass through the central hole through the bush 20 or 22 and which is screwed into the threaded interior 60 of the boss 54.

The transverse bore 62 allows a pin to be pushed therethrough to register with the castellations 68 formed in the end of the bush 20 or 22 and by selecting the length of the reduced diameter section 66 between the shoulder and the leading end of the boss 54 so the latter can be securely fastened in position by tightening the bolt.

By appropriate orientation of the strut formed by the two cylindrical tubes 46 and 48, so just the required degree of stiffness can be imparted between the front and rear sub-frames to allow the chassis to optimise the track or track conditions on which it is to be raced.

Claims

1. A go-kart chassis comprising a rear sub-frame, front sub-frame and at least one replaceable or adjustable strut member joining the front sub-frame to the rearsub-frame.

2. A chassis as claimed in claim 1 wherein two identical struts join the front and rear sub-frames together, the two struts comprising the strut members and being located on opposite sides of the chassis.

3. A chassis as claimed in claim 1 or 2 wherein each replaceable strut has one degree of stiffness in one transverse axis and a second degree of stiffness in a second transverse axis and means is provided for adjusting the orientation of each of the struts so that the predominant stiffness of each of the struts is either one or the other or a combination of the two degrees of stiffness possessed by the strut.

4. A chassis as claimed in claim 1 or 2 or 3 in which the opposite ends of each of the replaceable struts fit into recesses in the front and rear subframes and to allow the orientation of the replaceable strut to be selected and maintained, the struts and recesses are splined.

5. A chassis as claimed in claim 1 or 2 or 3 in which each replaceable strut is in the form of a hollow tube and the front and rear subframes include protruding spigots which fit into the ends of the strut and at least one end of the strut and one of the spigots is splined to allow the orientation of the strut to be selected and maintained.

6. A chassis as claimed in claims 1 to 3 wherein one end of each strut is adapted to receive a spigot and the other end is adapted to be fitted into a recess and appropriate spigots and recesses are provided on the front and rear sub-frames or vice versa so as to receive the ends of the strut accordingly.

7. A chassis as claimed in claims 1 to 3 wherein a castellated sleeve is provided on each of the subframes and the ends of the replaceable strut are adapted to be fitted into the castellated sleeve and secured in position by means of bolts which cannot pass through the sleeve and which are received in appropriately screw-threaded bores in opposite ends of the replaceable strut.

8. A chassis as claimed in any of claims 1 to 7 in which the strut is of oval or rectangular crosssection.

9. A chassis as claimed in claims 1 to 7 wherein the strut is a pair of tubes arranged with their axes parallel and welded along the line of touching between the two tubes.

10. A chassis as claimed in claim 9 wherein the strut ends are retained in circular section bushes having an internal diameter sufficient to accept the maximum diameter of the two side by side tubes and which include the end joining sections of the strut to allow the strut to be secured to the front and rear sub-frames.

11. A chassis as claimed in any of claims 1 to 7 wherein the strut is a circular section tube having integrally formed therewith or welded thereto one or more radial fins, the stiffness of the composite strut being dependent on whether the fin is parallel or perpendicular to the plane of bending.

12. A chassis as claimed in claim 11 wherein the strut is a circular section tube which is cut in half on a diameter of its cross-section and the two halves are welded on opposite sides of a plate so as to reconstitute a generally circular cross-section tube having two radially opposed fins at opposite ends of a diametrically extending plate.

13. A chassis as claimed in any of the preceding claims in which the strut is formed from mild steel or high tensile chromium molybdenum alloy steel or titanium, or spring steel.

14. A chassis as claimed in any of the preceding claims in which the struts are rotatable about their elongate axes relative to the sub-frames to allow for stiffness adjustment.

15. A chassis as claimed in any of the preceding claims further comprising a positive lock to prevent adjustment of the orientation of a strut after setting up, otherwise than after the lock has been undone.

16. A go-kart chassis as claimed in claim 1 constructed and arranged substantially as herein described with reference to and as illustrated in the accompanying drawings.