AU623704B2 - Kart frame - Google Patents

Description

S003755 21/11/88 ~62370Lt COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 Form COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: PJ1619 21 November 1988

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Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: S .0 00 0

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00 Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: BRIAN RANKIN en-JQON-WAT-SON--BAKER- 102 Anson Street, Orange, New South Wales 2800, Australia; andarg-Rad~-age-, *New-South-Waes-2800%-A-ustraiaT-respetively- BRIAN RANKIN GRIFFITH HACK CO.

71 YORK STREET SYDNEY NSW 2000

AUSTRALIA

Complete Specification for the invention entitled: KART FRAME The following statement is a full description of this invention, including the best method of performing it known to me/us:- -0 1 1534 -21 /11 /8CC9 51 x4

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This invention relates to a kart frame and has been devised particularly though not solely to improve the handling characteristics of a kart.

Racing karts have traditionally been fabricated from frames welded up from lengths of steel tubing on which are mounted the front and rear wheels, driver's seat, engine and other basic mechanisms. It is a feature of the regulations governing the construction of racing karts in some countries that conventional suspensions of the type used in normal automobiles are forbidden and the forces from the wheels are therefore transmitted directly to the frame of the kart.

Kart frames are therefore normally constructed so as to i incorporate certain flexure characteristics to allow some degree of vertical movement of the various wheels of the 3.5 kart and to enhance the grip characteristics of the tyres by controlled flexure of the kart frame. The requirements for *such controlled flexure are however often in opposition to each other and the ultimate design of the kart frame is inevitably a compromise which results in some characteristics being enhanced at the expense of others.

Kart frames presently in use are typically formed from main S" longitudinal frame rails with various cross members and front wheel support components welded to the main frame rails so as to form a generally planar frame having the 25 desired flexure characteristics. i| Because the entire frame can flex, the total weight of all the components of the kart, and the driver, form part of i| the unsprung weight with resultant problems in the damping of vertical movement of the wheels and the restitution of a stable high grip configuration following vertical deflection of any of the wheels. This effect can be largely reduced or ameliorated if the "unsprung weight" of the kart can be kept to a minimum, allowing each wheel to rapidly return to a stable high grip configuration following vertical deflection. I The pre5fnt invention therefore provides a kart frame comprising a rear portion arranged to support at least a rear axle, engine and drive train, and a front portion 6552S/rs 2 i :n 0 00 00 0 o Go 0 0 ff BOO 0 o0 *000 ao4 o connected to and extending from the rear portion arranged to support at least a front wheel and steering assembly, the rear portion being constructed to be relatively rigid compared to the front such that in use the front portion is permitted to flex accommodating front wheel movement whereas the rear portion is restrained from flexing.

Preferably the rear portion is provided with mounting points for a seat.

Preferably the front portion includes two longitudinal rails having their rear ends anchored to the rear portion and arranged to flex in torsion upon vertical movement of the front wheels.

Preferably the rear ends of the longitudinal rails are located in longitudinal tubes rigidly mounted on the rear 15 portion and secured to these tubes by transverse bolts or pins passing through each rail and tube.

Preferably the rear portion is provided with bearing carriers for the rear axle, arranged to pivot about a longitudinal axis relative to the frame, allowing the rear axle to flex and bend in use.

Preferably the rear portion is fabricated from a plurality of tubes in a space frame configuration.

Alternatively the rear portion is fabricated as a monocoque tub.

25 Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be described by way of example only with reference to the accompanying drawings, in which:- Fig. 1 is a plan view of a kart frame according to the invention showing various additional components in broken outline; Fig. 2 is a side view of the frame shown in Fig. 1; Fig. 3 is a front view of the kart frame; Fig. 4 is a rear view of the kart frame; Fig. 5 is a plan view of the kart frame with the upper part of the rear frame omitted for clarity; Fig. 6 is a similar plan view of the upper part of the 000 o 00s 00 0 o a 0 01 Ot E

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o c 4 040411 4 4 c 004400 0 0 04 0 0 0 0 0 rear frame; and Fig. 7 is a side view of the kart frame according to the invention.

In the preferred form of the invention as shown in the accompanying drawings, the kart frame is fabricated from lengths of steel tubing welding together and formed into a front portion in front the line A-A of Fig. 1 and a rear portion behind that line. The front portion includes mounts for the front wheels and steering assembly as well as other ancillary equipment such as throttle and brake pedals etc. (not shown). The front portion is designed to be relatively flexible and incorporates two longitudinal rails at bent outward toward the forward ends to form mounts for the king pins The forward ends are in turn 15 connected by a front sway tube The longitudinal rails are connected to the rear portion of the kart frame by having their rearward ends mounted in longitudinal tubes (8) which are rigidly connected to, and form part of, the rear frame portion and are typically secured in those tubes by transverse pins or bolts.

In use of the kart frame, the rails are designed to flex in torsion upon vertical movement of the front wheels providing an elastic restoring force to the wheels to return the wheels to their desired positions.

25 By way of contrast the rear portion is constructed to be relatively rigid compared to the front portion and to this end is formed in a space frame configuration by a plurality of tubes welded together to form a rigid frame.

The frame incorporates mounts for a seat an engine (10) and a rear axle (11) on which are mounted the rear wheels The rear axle (11) is mounted in the frame by way of hangers (13) which preferably incorporate bearing carriers for the rear axle, arranged to pivot about a longitudinal axis relative to the frame, allowing the rear axle to flex and bend in use as will be described further later.

The rear portion of the frame also incorporates mounts

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cc( for other conventional components such as a disc brake, chain drive train, exhaust and other kart components.

The rear portion of the kart frame may be arranged in any convenient format but typically incorporates main frame rails (14) (Fig. an engine mount rail and a transverse tube all located in the base plane as can be seen in Fig. 7. To "triangulate" the rear portion of the frame and provide the desired rigidity, additional frame rails (17) and (18) extend rearwardly from a main cross tube (19) to elevated points (20) and (21) respectively and are in turn connected by further tubes (22) and (23) to complete a triangulated rigid frame for the mounting of the rear axle hangers (13).

In this manner a relatively rigid rear frame portion is 15 provided to mount the rear axle hangers (13) relative to the seat and engine and also relative to the main cross tube (19) which then forms the mounting point for the relatively flexible front frame portion via the tubes The rear one-piece axle (11) is preferably relatively flexible and mounted in bearings arranged to pivot about a longitudinal axis as previously described. Because of the flexible nature of the axle and the bearings, the entire axle can flex under vertical load from the rear wheels (12) thus providing a degree of quasi suspension movement without 25 imparting that movement by way of flexure into the rear portion of the kart frame. Because the rear portion of the kart frame supports the major weight components (the engine seat and drive) and because all of these components are then held rigidly relative to the movement of the rear wheels, these major weight components do not form part of the unsprung weight of the kart which is therefore significantly reduced compared to conventional kart frames. This reduction in unsprung weight significantly improves the handling characteristics of the kart and enables the tyres to develop considerably more grip as they are held in closer contact to the track surface during operation.

Although the rear portion of the kart frame has been 4444 o 4 4: 9 4 4.

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i r 1 I i, i 1:, :i 6552S/rs 5 described as being formed from a plurality of tubes welded together in a space frame configuration in order to achieve a rigid rear frame portion, this is only one possible way of forming the rear kart frame. Present racing regulations call for all kart frames to be formed from metal tube and therefore this configuration is presently adopted. Should the regulations be relaxed, the invention could equally well be put into effect, by forming the rear portion of the kart frame in other configurations such as a monocoque tub either fabricated from metal panels or moulded from carbon fibre or other suitable materials.

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Claims (8)

1. A kart frame comprising a rear portion arranged to support at least a rear axle, engine and drive train, and a front portion connected to and extending from the rear portion arranged to support at least a front wheel and steerir.g assembly, the rear portion being constructed to be relatively rigid compared to the front such that in use the front portion is permitted to flex accommodating front wheel movement whereas the rear portion is restrained from flexing.

2. A kart frame as claimed in claim 1 wherein the rear portion is provided with mounting points for a seat.

3. A kart frame as claimed in either claim 1 or claim 2 wherein the front portion includes two longitudinal rails having their rear ends anchored to the rear portion and arranged to flex in torsion upon vertical movement of the front wheels.

4. A kart frame as claimed in claim 3 wherein the rear ends of the longitudinal rails are located in longitudinal tubes rigidly mounted on the rear portion and secured to these tubes by transverse bolts or pins passing through each rail and tube.

5. A kart frame as claimed in any one of the preceding claims wherein the rear portion is provided with bearing carriers for the rear axle, arranged to pivot about a longitudinal axis relative to the frame, allowing the rear axle to flex and bend in use.

6. A kart frame as claimed in any one of the preceding claims wherein the rear portion is fabricated from a plurality of tubes in a space frame configuration.

7. A kart frame as claimed in any one of claims 1 to wherein the rear portion is fabricated as a monocoque tub.

8. A kart frame substantially as described herein with reference to the accompanying drawings. SC C (C t C (L t CC CCf DATED this 21st day of NOVEMBER 1989 BRIAN RANKIN ~nd-JOHWN-WA-TSON-BAKER-- By his Patent Attorneys GRIFFITH HACK CO. i i e i i i -i I; is a 6552S/rs 7 ii L