GB2469674A - Steering and bottom bracket for a wooden bicycle - Google Patents

Abstract

A bicycle comprising a frame and fork 20 made of wood has a steering assembly in which standard headset bearing components 22 are inserted into grooves in the steering head area 21 of the frame and matching bearing components 22 are mounted on stubs 25 connected to the fork 20. A bottom bracket shell 31 is secured to a wooden bicycle frame utilising an adjustable clamp. The clamp is formed from a pair of angle-members 32 pivoted to the frame at a first end and secured by clamping bolts 34 at a second end. A packing block 36 may engage the bottom bracket shell 31, and the shell 31 may be further held by bracket 35 incorporating pins with locate in the shell 31 and prevent lateral or rotation movement of said shell 31.

Description

The present invention relates to new designs for bicycles. In particular, the invention concerns improved designs for bicycles made of wood.

Generally, the availability of wheeled transport in society has proved to be a significant facilitator of economic activity, which has resulted in improved standards of living in both social and health terms. The lack of wheeled transport has far-reaching consequences. In many countries in Africa, transport is expensive or not available. At a local level, food, water and materials are often transported as headloads, or on heavy carts. These methods limit what can be carried, and divert valuable time and energy away from more useful activities, such as food production, manufacturing, going to work, or simply being able to visit family and friends.

Cheaper bicycles would increase the availability of wheeled transport to people who had previously not been able to afford it, and hence gain the economic, social and health benefits from increased mobility.

Therefore, an object of the invention is to provide an appropriate and affordable technology, utilising available skills and materials, to provide more bicycles to more people, particularly in African countries. Such a bicycle would be buildable with locally available skills and materials, without the need for electricity, and encourage local manufacture instead of importing foreign bicycles.

The bicycle is by far the most common form of wheeled transport in Africa. Bicycles and bicycle spare parts are major consumer goods in Africa.

Many businesses sell and service bicycles, which are imported almost exclusively from India and China.

The bicycle, bike, or cycle is a pedal-driven, human-powered vehicle with two wheels attached to a frame, one behind the other.

The great majority of today's bicycles have a frame with upright seating which looks much like the first chain-driven bike. Such upright bicycles almost always feature the diamond frame, a truss consisting of two triangles: the front triangle and the rear triangle. The front triangle consists of the head tube, top tube, down tube and seat tube. The head tube contains the headset, the set of bearings that allows the fork to turn smoothly for steering and balance. The top tube connects the head tube to the seat tube at the top, and the down tube connects the head tube to the bottom bracket. The rear triangle consists of the seat tube and paired chain stays and seat stays. The chain stays run parallel to the chain, connecting the bottom bracket to the rear dropouts. The seat stays connect the top of the seat tube (at or near the same point as the top tube) to the rear dropouts.

The handlebars turn the fork and the front wheel via the stem, which rotates within the headset. Commonly, the handlebar is straight. This shape provides good low-speed handling. Other styles of handlebar, such as dropped, may be fitted. The wheel axles fit into dropouts in the frame and forks.

Generally, the tubes of the frame are made of steel or a steel alloy such as chromoly. These materials are strong, easy to work, and relatively inexpensive, but denser, and therefore heavier, than many other structural materials. A classic type of construction uses standard cylindrical steel tubes which are connected with lugs (fittings made of thicker pieces of steel). The tubes are fitted into the lugs, which encircle the end of the tube, and are then brazed to the lug. A more economical method of bicycle frame construction uses cylindrical steel tubing connected by tungsten inert gas (TIG) welding, which does not require lugs to hold the tubes together. Instead, frame tubes are precisely aligned into a jig and fixed in place until the welding is complete.

Butted tubing, in which the wall thickness of the tubing changes from thick at the ends (for strength) to thinner in the middle (for lighter weight), can be used to reduce weight, but increases cost. Cheaper steel bicycle frames are made of mild steel and are heavier than higher quality frames made from high strength steel alloys such as chromoly which can be made into lightweight tubing with very thin wall gauges.

The main method of low cost transport in Africa is single speed, steel framed bicycles, manufactured in China. In Tanzania, they are being sold for �100, which is not affordable for many people. A locally made bicycle would be cheaper, easier to maintain, generate employment and reduce reliance on foreign imports. However, the materials to make metal framed bicycles -metal tubes and brackets -are unavailable or too expensive in many parts of Africa and the tools and skills needed to weld and braze the parts together are lacking.

There is therefore a need for an affordable, simple, reliable bicycle made primarily from locally available materials and components and capable of being constructed using commonly available skills and tools.

Accordingly, the invention provides a bicycle comprising a frame and fork made of wood.

Wood is cheaper and more readily available than metal. The use of wood as the structural material eliminates the need for welding and brazing and simplifies the construction to basic carpentry and fitting skills, similar to those already used to make furniture and wire toys. Standard components are used for the moving parts and may be simply bolted to the frame. The wooden bicycle of the invention is easy to make and to maintain/repair. It has been designed for use in Africa, but would be equally suitable for developing countries in other regions.

The suitability of a material for construction of a bicycle frame depends upon a number of its properties e.g. density (a frame of the required strength should not be so bulky as to be impracticable), stiffness (lateral stiffness is an issue because of the narrow profile of a frame: the frame should not flex unduly when ridden/pedalled), yield strength and elongation (for crash-worthiness), and fatigue and endurance limits (for durability). Wood is not generally considered a suitable material for the construction of bicycle frames such as double-triangle diamond frames because it lacks the required strength and stiffness. Bicycle forks are not made from wood for the same reasons.

The inventor has found that the perceived shortcomings of wood as a material for the construction of bicycle frames and forks can be overcome by appropriate engineering and design, as described herein. The inventor has thereby succeeded in producing wood framed bicycles whose weight and strength is comparable with that of steel framed bicycles.

Preferably, the bicycle frame and fork are made from wood which is laminated, i.e. made of two or more sheets of wood (e.g. softwood) bonded (e.g. glued) together. More preferably, the laminate comprises at least three sheets of wood. The laminated construction provides greater strength and stiffness and resists the warping that may occur in a non-laminated timber when exposed to variations in humidity.

The inventor has developed special joints which provide the required strength at the stress points of the frame, e.g. the bottom bracket and the steering head. The individual sheets of the laminated frame members are adapted to interleave at the joints between the frame members, thus providing a very strong union. In a preferred embodiment, the frame has a double triangle configuration giving a high strength, composite, laminated, triangulated structure. The design can be easily adapted for the construction of frames having different shapes and geometries.

The bicycle frame described herein can be constructed by a step-wise method that allows easy setting out of the complex geometry of a bicycle: first the main triangle, followed by the chain stays, and lastly the seat stays. The same construction provides tolerance in the manufacture of the bicycle frame i.e. inaccurate construction can be corrected as the bicycle is made.

Standard components for the moving parts are then fixed to the frame with handmade metal brackets, threaded bar, nuts, and machine screws.

Bicycle components used to be compatible with each other and easily interchangeable. It was a universal technology with common fixings and thread sizes. Today they are specialized and components have to be specifically grouped. The bicycle of the invention is capable of accepting all ranges of bicycle components from basic Chinese single speed drivetrains to the latest Shimano mountain bike groupsets.

The bicycle of the invention is suitable for rough roads using standard 700C, 27" or 26" diameter wheels.

The bicycle of the invention is readily adaptable and amenable to modification e.g. it can accommodate a variety of load-carrying frames, or be fitted with a trailer or side-car. Scrap and second hand materials may be utilised in the construction of bicycles according to the invention. The wooden frame may be readily personal ised/decorated using ordinary paints.

The bicycle of the invention can be made with different frame geometries and in different sizes (standard or made to measure).

In another embodiment, the invention provides a steering mechanism for a wooden bicycle, i.e. the joint between the front fork and frame which firmly connects the two parts while pivoting, and spreads the load stresses in the softer wood.

Accordingly, the invention provides a steering assembly for a bicycle having a wooden frame and fork, in which upper and lower cups are fitted into corresponding circular grooves on the upper and lower surfaces of the steering head of the frame, the lower race is fitted over a peg glued to the fork, the upper race is fitted over a peg glued to a movable upper plate, the fork and upper plate are clamped onto the cups on the frame and bolted together using a threaded bar on the pivot centreline and an angled bolt between the fork and upper plate. Conveniently, the pegs over which the upper and lower races are fitted are made from hardwood and the upper plate is wooden, however, other materials may be used for these parts, provided that the material has the necessary physical properties (strength, stiffness etc.) for the part to perform its function.

This assembly allows standard metal headset races to be fitted into a wooden frame, thus utilising standard moving components, fitted using carpentry skills. This arrangement allows the required cooperation between the frame and fork while providing the necessary strength and stiffness using Accordingly, the invention further provides a bicycle comprising a frame and fork made of wood, in which the frame and fork are connected by a steering assembly as described above.

Another part of the frame that must be able to withstand significant stresses is the site where the bottom bracket is fixed to the frame. The bottom bracket contains a spindle, to which the crankset is attached, and bearings that allow the spindle and cranks to rotate. The bottom bracket must be securely fixed to the frame so that, when the bicycle is pedalled, the pedalling force is transmitted through the chainset to drive the bicycle, rather than acting to twist the bottom bracket relative to the frame, resulting in inefficiency and possibly damage to the frame. A possible arrangement is to have a threaded barrel that is precisely fitted into the wooden body of the bicycle frame, into which the crankset cups are screwed. However, to make the precise interference fit of the barrel requires engineering tools, jigs and skilled craftsmanship which are not available in some areas of the world. In addition, it is not possible to maintain a tight fit in wood that is expanding and contracting in a humid climate. These problems could be avoided by bolting a threaded metal barrel -to which the crankset is fitted -to the wooden frame.

However, it remains a problem to devise a fixing that is sufficiently strong and secure to withstand the large forces to which it is subjected while pedalling.

Accordingly, in a bicycle according to the invention, the barrel housing the bottom bracket is secured to the frame at the angle formed between the seat frame element and the chain stays by an adjustable clamp. Preferably, the clamp comprises a pair of metal angles pivotably mounted on the frame at one end and adapted to be adjustably secured against the frame at the other end. Conveniently, the means for adjustably securing the ends of the metal angles is a pair of pinch bolts. The assembly clamps the barrel into the V of the bottom frame joint in a scissor action.

Ideally, the bicycle further comprises means to prevent lateral or rotational movement of the barrel. For example, the barrel may be located onto two pins cut from a metal angle, thus preventing the bottom bracket from moving laterally or rotating.

Precise fit, and hence more secure retention of the barrel, can be achieved with a sliding, profiled wooden packing block.

Widely spaced fixing points spread loads into the wooden frame. Use and operation are as for a conventional steel bicycle frame, with standard cranksets and pedals.

This assembly provides strong attachment for the bottom bracket to the wooden bicycle frame, that spreads the load stresses in what is a soft material. The adjustable fixing provides tolerance and allows the use of a wide variety of standard cranksets. The pinch bolts can be adjusted over time to compensate for movement of the timber.

The invention further provides a method for securing a bottom bracket to a wooden bicycle frame, said method comprising clamping the barrel housing the bottom bracket in the angle formed between the seat frame element and the chain stays using a pair of metal angles pivotably mounted on the frame at one end and adapted to be adjustably secured against the frame at the other end.

The skills required to manufacture the wooden bicycle are basic, common sense carpentry, using ordinary hand tools. Specialist equipment and workshops are not required, so the capital investment for each bike is low.

While the design could be mass produced, it is also economical for small scale production.

The materials can conveniently be cut and assembled using full size paper drawings as templates, with instructions that can be diagrammatic rather than written. The design incorporates large tolerances, thus allowing for inaccurate construction to be corrected as the bicycle is made.

The wooden bicycle provides opportunities for the creation and growth of small business enterprises e.g. the possibility for small furniture and bicycle workshops to manufacture their own bicycles. It would be possible to use unskilled labour for constructing the frame. Bicycle construction would provide opportunities for training individuals in carpentry and metalwork skills.

As a start up business, wooden bicycle construction would provide an introduction to production processes, management, organisation, stock control and small scale mass production. There would be opportunities to start associated businesses, ranging from the supply of bike components, through manufacturing small components like the bottom bracket, to the repair and maintenance of the bicycles by existing bicycle shops.

Such opportunities promote independence from large commercial companies and governments who can control and exploit markets. In addition, locally made products reduce the need for importing bicycles and thus conserve valuable foreign exchange. Wooden bicycle production could be a stepping stone to more complex manufacturing: most vehicle manufacturers in the world started with bicycles before moving on to motorbikes, cars and buses.

Preferred features of different embodiments of the invention are as to each other mutatis mutandis.

The invention is illustrated by the following non-limiting example with reference to the appended figures, of which:-Figure 1 is a drawing showing a side elevation of a wooden framed bicycle according to the invention.

Figure 2 is a drawing showing a perspective view of a wooden bicycle frame according to the invention.

Figure 3 is a drawing showing an exploded view of a wooden steering assembly according to the invention.

Figure 4 shows the clamp for securing the barrel housing the bottom bracket to the frame.

Figure 5 is a series of photographs of a bicycle according to the invention: 1. Bicycle right hand side. 2. Bicycle left hand side. 3. Handle bars and front forks. 4. Bottom bracket.

Figure 6 is a drawing showing a side elevation of a bicycle according to a further embodiment of the invention.

Examples

An example of a wooden framed bicycle according to the invention is shown in Figure 1. The frame, steering assembly and bottom bracket attachment are shown in more detail in Figures 2 to 4, respectively.

The frame illustrated in Figure 2 has a double triangle configuration reminiscent of those known from conventional steel tube frames. The different frame elements or members are conveniently named after the corresponding tubes in a conventional frame: top frame element (1), down frame element (2), seat frame element (3) and paired chain stays (4) and seat stays (5). The tn-laminate construction of the top, down and seat frame elements is apparent. The junction of the top and down frame elements is adapted for attachment of the steering assembly which connects the front fork to the frame. This junction therefore performs the function done by the head tube on a conventional steel tube frame and may be referred to herein as the steering head. For simplicity, the attachments for the saddle and bottom bracket have been omitted from Figure 2.

Figure 3 illustrates a steering assembly according to the invention by which the fork (20) is attached to the steering head (21) of the frame. Upper and lower cups (22 & 23) are fitted into corresponding circular grooves on the upper (24) and lower (not visible) surfaces of the head element of the frame, the lower race is fitted over a peg (25) glued to the fork, the upper race is fitted over a peg glued to a movable upper plate (26), the fork and upper plate are clamped onto the cups on the frame and bolted together using a threaded bar (27) on the pivot centreline and an angled bolt (28) between the fork and upper plate. A handlebar (29), such as a round wooden dowel, is fixed to the forks with a pair of U bolts bent from threaded bar (30).

Figure 4 illustrates the adjustable clamp of the invention for securing the barrel (31) housing the bottom bracket to the frame at the angle formed between the seat frame element and the chain stays. The clamp comprises a pair of metal angles (32) pivotably mounted on the frame at one end by means of a threaded bar (33). The metal angles are adjustably secured against the frame at their other end by a pair of pinch bolts (34). The barrel is prevented from moving laterally or rotationally by being located onto two pins cut from a metal angle (35). A sliding, profiled, wooden packing block (36) provides a precise fit, and therefore a secure location of the barrel.

A complete bicycle comprising a wooden frame and fork and incorporating the steering assembly and bottom bracket attachment described herein is shown in Figure 1.

A working prototype wooden bicycle according to the invention is illustrated in Figure 4.

Figure 5 shows another embodiment of the invention wherein the seat stays are formed as a continuation of the top frame element. The structural advantages of the double triangle and configuration are maintained while providing a lower step-over height permitting the bicycle to be used more easily by smaller individuals, including children. An exemplary load or passenger carrier is shown with dotted lines.

Claims (9)

1. CLAIMS1. A bicycle comprising a frame and fork made of wood.
2. 2. A bicycle according to claim 1, in which the wood is laminated.
3. 3. A bicycle according to claim 1 or claim 2, in which the frame has a double triangle configuration.
4. 4. A steering assembly for a bicycle having a wooden frame and fork, in which upper and lower cups are fitted into corresponding circular grooves on the upper and lower surfaces of the steering head of the frame, the lower race is fitted over a peg glued to the fork, the upper race is fitted over a peg glued to a movable upper plate, the fork and upper plate are clamped onto the cups on the frame and bolted together using a threaded bar on the pivot centreline and an angled bolt between the fork and upper plate.
5. 5. A bicycle according to any of claims 1 to 3, in which the frame and fork are connected by a steering assembly according to claim 4.
6. 6. A bicycle according to any preceding claim, further comprising a barrel housing the bottom bracket, said barrel being secured to the frame at the angle formed between the seat frame element and the chain stays by an adjustable clamp.
7. 7. A bicycle according to claim 6, in which the clamp comprises a pair of metal angles pivotably mounted on the frame at one end and adapted to be adjustably secured against the frame at the other end.
8. 8. A bicycle according to claim 6 or claim 7, further comprising means to prevent lateral or rotational movement of the barrel.
9. 9. A method for securing a bottom bracket to a wooden bicycle frame, said method comprising clamping the barrel housing the bottom bracket in the angle formed between the seat frame element and the chain stays using a pair of metal angles pivotably mounted on the frame at one end and adapted to be adjustably secured against the frame at the other end.