BICYCLE REAR WHEEL COMMON AXIS DRIVE AND DRIVEN MECHANISM FOR TANDEM BICYCLE

DESCRIPTION:

FIELD OF THE INVENTION:

The present invention relates to a tandem bicycle. More specifically it relates to a novel mechanism for driving said tandem bicycle.

BACKGROUND OF THE INVENTION:

In day to day life use of automobiles like scooters, motorcycles, three-wheeler autos to travel short distance of 3- 6 kilometres is drastically increasing consumption of fuel, like diesel petrol and electricity. Use of more fuel adds to environmental pollution. Usage of more and more plastic components to reduce the cost of automobiles, generate non-biodegradable waste.

The British inventor John Kemp Starley designed the first successful 'safety ¹ bicycle in 1885. It has all the basic features of standard modern bicycles, including chain drive, and both wheels of the same size. The introduction of the safety bicycle cycling became enormously popular, among both men and women, commonly used safety bicycle can be seen in figure 1 .

This bicycle is driven by applying force on the paddle assembled in the cranks by a rider sitting on the saddle assembled in seat tube.

The axle of the flanged rear hub is fixed in the chain stay end pieces by using nuts. A cup and cone bearing in rear hub and axel make wheel a negligible friction wheel. Chain connected to the chain wheel and free wheel provides driving power to rear wheel, to rotate it against rolling resistance on ground. Safety bicycle is convenient to drive on crowded roads, and is used past 137 years in this form as a mode of transportation. A tandem bicycle is two wheeled bicycle, driven by two riders sitting one behind another between two wheels as can be seen in figure 2. Both riders drive rear wheel simultaneously through chain wheel and freewheel, therefore the tandem receives driving power from two persons, which is utilized to achieve more speed. U.S. patent no 415072 entitled Tandem Bicycle was issued to Creators William Starley of Coventry, England, and Herbert S. Owen of Washington DC, in Nov 1889. Patent diagrams show a tandem bicycle assembly similar to tandem bikes which are still seen today.

Bicycle utilizes human energy for movement and transportation, is an economic and energy efficient solution and helps in reducing the fuel consumption. Considering its weight, the average bicycle weight is 15-17 kg which carries one rider, proves bicycle as a least weight equipment used as transportation vehicle. Considering energy utilization, Fig. 3 confirms the usefulness of the bicycle as a mode of transportation. Summarizing all above points, it is apparent that Bicycle is a compact, energy efficient, nonpolluting, biodegradable transportation vehicle with almost 95% mechanical efficiency.

Practically travelling alone on bicycle for 30 -45 minutes is a boring and tiresome, and one feels exhausted. Now a days people prefer to travel on tandem bicycles for long distance (20- 30 kms usually) on weekends and holidays. Using tandem bicycle, is a faster way to travel than single rider bicycle, as the tandem bicycle is driven by two people simultaneously therefore more input energy contributes to more output power. Scientifically as the velocity increases, the force requirement to propel the bicycle increase in proportion to the sq. of the velocity (due to head wind) and therefore power requirement increase in proportion to cube of the velocity. This input power is provided by rear rider. The rear rider who does not face the frontal wind resistance, his/ her energy is utilized, only to overcome frictional road resistance and to increase the velocity of bicycle. Tandem cycles are more energy efficient as far as the speed increasing factor is considered. In spite of having so many benefits of tandem bicycles, not too many such bicycles are used for daily commute.

Because tandems are longer than solo bikes, they require more space to turn. If you make a wrong turn down a narrow street or bike path, you can’t easily make a U-turn or lift the front wheel and pivot the bike.

The rear rider may have to get off the bike while the front rider makes a 3-point turn. In some cases, both riders have to just get off the bike, lift it up, and turn it manually. This is inconveniencing that one has to deal with once in a while.

One more problem for those who plan to tour or travel with their tandem bike is length and weight of present for tandem bicycle. They are difficult to fly with or carry on a bus or train. Some airlines, bus companies, and train lines simply prohibit luggage as large as a tandem bike. Tandems are also difficult to carry with a vehicle. They are too long to fit on a standard bike rack on top of a car. If one like to use multiple modes of transport while touring, tandem may cause some headaches. For example, one wants to take a bus or train to the next city instead of cycling, he/she has to make sure the bus or train can accommodate the large bike. Hitchhiking with a tandem will be nearly impossible as most average sized vehicles can’t accommodate a tandem. In some cases, you may have no option but to ride or hire private transport. Depending on your style of touring, this may be problematic.

Tandem are not used on crowded and smaller width roads, because reduction in tandem speed to control the turning results in traffic jams.

One more difficulty while driving tandem is balancing the bicycle. It is common experience when horizontal distance between the front rider second rider increases, riders experience difficulty in balancing.

Even after 137 years after the invention of the bicycle, it is used only as a weekend journey recreation/sports bicycle for two people riding, because of its longer wheel base and length. Even after considering the usefulness of the tandem bicycles, we don’t see increasing number of users, because of its larger turning radius and difficulty in balancing, due length required to build the Tandem cycles.

Therefore there is a long standing need of a shorter wheel base tandem.

The current invention satisfies this need by providing a shorter wheel base tandem which is comparable to single rider bicycle, suitable for two riders, with a suitable mechanism to transmit the power of rear rider to rear wheel.

SUMMARY OF THE INVENTION:

In first and principal aspect the invention provides a tandem bicycle comprising a) a hub assembly (1 ) having

- a rotatable central shaft (2.1 ) housed inside and surrounding by a flanged housing (1 .3);

- one or more bearing (1.1/1 .2) press fitted within the space between said rotatable central shaft (2.1 ) and said flanged housing (1.3) with its inner race (1 B) in contact with said rotatable central shaft (2.1 ) and outer race (1 B) in contact with said flanged housing (1 .3);

- spokes (11 ) engaged between said flanged housing (1 .3) and the rim (12) holding a rear wheel (13); and

- a freewheel (1.6) fitted on said flanged housing (1.3) connected to the front rider’s first chain wheel and crank assembly(8.1 ) through a chain (10), b) left and right side cranks (2.2, 2.3) fitted at the ends of said rotatable central shaft (2.1 ), c) left and right side bearing housings (3.1 ) connected to chain stay end pieces (3.3) housed with bearings (3.4) with its inner race (3.4B) in contact with said rotatable central shaft (2.1 ) and outer race (3.4A) in contact with said bearing housings (3.1 ), d) a hub (7.2) arrested on said rotatable central shaft (2.1 ) and fitted with chain wheel (7.1 ) connected to the front rider’s second chain wheel and crank assembly (8.2) through a chain (9), and e) a rear saddle located upon said rear wheel (13).

BRIEF DESCRIPTION OF THE DRAWINGS:

The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which the reference numerals indicate:

FIGURE 1 illustrates the commonly used safety bicycle (prior art);

FIGURE 2 illustrates the generally known designs of tandem bicycle (prior art);

FIGURE 3 illustrates the energy utilization chart for various transport mediums;

FIGURE 4 illustrates the tandem bicycle and its photograph according to one of the embodiments of the current invention;

FIGURE 5 illustrates the tandem bicycle according to another embodiment of the current invention;

FIGURE 6 illustrates the hub assembly (1 ) for the tandem bicycle according to the one of the embodiments of the current invention;

FIGURES 7, 8 and 9 illustrate the elements, components and features of tandem bicycle according to the preferred embodiment of the current invention;

FIGURES 10 and 11 illustrate the cross-sectional views of the tandem bicycle according to the one of the embodiments of the current invention; and

FIGURES 12 and 13 illustrate the working of the tandem bicycle of current invention (as manufactured in example 1 ) in example 2;

FIGURE 14 illustrates the length comparison amongst the monocycle A, tandem B and the tandem bicycle C of current invention;

FIGURE 15 illustrates of the turning radius calculation for the bicycles; and FIGURES 16 and 17 show the photographs taken during the turning trial of Tandem B and tandem bicycle C of current invention respectively.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As mentioned, there remained a long felt need to provide a shorter wheel base tandem. The present embodiment tries to address this long felt need.

Present invention provides a shorter wheel base tandem which is comparable to single rider bicycle, suitable for two riders, with a suitable mechanism to transmit the power of rear rider to rear wheel. This mechanism is located at the centre of the rear wheel. The mechanism construction is such that it can be driven from the central axis of the mechanism by a rotatable shaft assembly shaft 2, that drives the rear wheel fixed on the same axis, by sitting on the saddle provided above rear wheel.

Referring now to the figures, where similar reference characters denote corresponding features consistently throughout the figures, preferred embodiments are shown.

Mainly referring to Figures 6 to 11 , the construction of the current inventive tandem bicycle according to one of the exemplary embodiments of the invention is illustrated.

In first aspect of the invention, a tandem bicycle mainly comprises a) a hub assembly (1 ) having

- a rotatable central shaft (2.1 ) housed inside and surrounding by a flanged housing (1 .3);

- one or more bearing (1.1/1 .2) press fitted within the space between said rotatable central shaft (2.1 ) and said flanged housing (1.3) with its inner race (1 B) in contact with said rotatable central shaft (2.1 ) and outer race (1 B) in contact with said flanged housing (1 .3);

- spokes (11 ) engaged between said flanged housing (1 .3) and the rim (12) holding a rear wheel (13); and - a freewheel (1.6) fitted on said flanged housing (1.3) connected to the front rider’s first chain wheel and crank assembly(8.1 ) through a chain (10), b) left and right side cranks (2.2, 2.3) fitted at the ends of said rotatable central shaft (2.1 ), c) left and right side bearing housings (3.1 ) connected to chain stay end pieces (3.3) housed with bearings (3.4) with its inner race (3.4B) in contact with said rotatable central shaft (2.1 ) and outer race (3.4A) in contact with said bearing housings (3.1 ), d) a hub (7.2) arrested on said rotatable central shaft (2.1 ) and fitted with chain wheel (7.1 ) connected to the front rider’s second chain wheel and crank assembly (8.2) through a chain (9), and e) a rear saddle located upon said rear wheel (13).

In one of the preferred embodiments, in a) said one or more bearing (1.1/1 .2) are retained within the space between said rotatable central shaft (2.1 ) and said flanged housing (1.3) by the retainers (1.4, 1.5) and spacers (6) arresting the lateral movements of the bearing (1.1/1 .2). Said retainers (1 .4, 1 .5) and spacers (6) are the circular holders touching the lateral surfaces of the outer and inner race of bearing (1.1/1 .2). In a suitable embodiment, said retainers (1.4, 1.5) are fixed within said flanged housing (1.3) with the threading. Preferably, the outer race (1.1 ) of bearings are press fitted in the designated spaces in the housing (1 .3) and inner race (1.2) press fitted on the shaft (2.1 ).

In another preferred embodiment, in c) said bearings (3.4) are retained within bearing housings (3.1 ) by the retainers (3.2), spacers (6) and locking nuts (4) with locking washer (5) arresting the lateral movements of the said bearings (3.4). Suitably, said retainers (3.2) are the circular holders touching the lateral surfaces of the outer race of said bearings (3.4). Preferably, said spacers (6) and locking nuts (4) with locking washer (5) are the circular holders touching the lateral surfaces of the inner race of said bearings (3.4). In yet another preferred embodiment, in d) said hub (7.2) is fitted with said chain wheel (7.1 ) by bolted arrangement or by welding or is casted as a single component. Preferably, said hub (7.2) is arrested on said rotatable central shaft (2.1 ) using one or more key (7.3) or by splines or is casted as a single component.

In yet another preferred embodiment, in e) said rear saddle is located upon said rear wheel (13) within the seat tube angle range of 63° to 80°. Said rear saddle is connected to said chain stay end pieces (3.3) or to the horizontal frame of said tandem bicycle.

In another aspect of the invention, a tandem bicycle comprising a) a hub assembly (1 ) having

- a rotatable central shaft (2.1 ) housed inside and surrounding by a flanged housing (1 .3);

- one or more bearing (1.1/1 .2) press fitted within the space between said rotatable central shaft (2.1 ) and said flanged housing (1.3) by the retainer (1.4, 1.5) and spacers (6) arresting the lateral movements of the said bearing (1.1/1 .2)

- said bearing (1.1/1 .2) has its inner race (1 B) in contact with said rotatable central shaft (2.1 ) and outer race (1 B) in contact with said flanged housing (1.3);

- spokes (11 ) engaged between said flanged housing (1 .3) and the rim (12) holding a rear wheel (13); and

- a freewheel (1.6) fitted on one of retainers (1.4, 1.5) connected to the front rider’s first chain wheel and crank assembly (8.1 ) through a chain (10), b) left and right side cranks (2.2, 2.3) fitted at the ends of said rotatable central shaft (2.1 ), c) left and right side bearing housings (3.1 ) connected to chain stay end pieces (3.3) housed with bearings (3.4) with its inner race (3.4B) in contact with said rotatable central shaft (2.1 ) and outer race (3.4A) in contact with said bearing housings (3.1 ), d) a hub (7.2) arrested on said rotatable central shaft (2.1 ) and fitted with chain wheel (7.1 ) connected to the front rider’s second chain wheel and crank assembly (8.2) through a chain (9), and e) a rear saddle connected to said chain stay end pieces (3.3) by a forked connection and located upon said rear wheel (13).

In both the aspects of the invention, preferably the front rider’s first chain wheel and crank assembly (8.1 ) and front rider’s second chain wheel and crank assembly (8.2) are selected from left and right side chain wheel and crank assembly provided both are not at the same side. And also, preferably both the chain wheels i.e. chain wheel (7.1 ) and the chain wheel in front rider’s second chain wheel and crank assembly (8.2) have equal number of teeth.

Construction and working of the invention: Example 1 : Construction

The tandem bicycle was constructed according to the current invention. The components actually used and also their alternatives, if any that can be used are mentioned below:

The photograph of the manufactured tandem bicycle can be seen in Figure 4. The seat can also be placed on extended top tube as shown in Figure 5 without using forked arrangement connected to the chain stay as shown in Figure 4. The tandem bicycle manufactured is of reduced length than the conventional tandem bicycle and enables in-tandem force transmission and motion of the riders. The wheel diameter is 660mm (26”) and wheels centre distance is 1350 mm. Example 2: Working

The tandem bicycle of current invention as manufactured in example 1 was driven by two riders. Following course of action occurs while driving this tandem bicycle: 1. Referring to figure 12, the front rider applies peddling force on the right hand side chain wheel & crank (8.1 ) and left hand side chain wheel & crank (8.2), assembled on rotating bottom bracket axle (8.3).

2. Referring to figure 13, rear rider rotates the shaft assembly (2) by applying leg force through right (2.3) and left cranks (2.2) with pedal.

3. Torque of the shaft (2.1 ) is transferred to left hand side chain wheel (7.1 ) through keys (7.3) assembled on this shaft.

4. Torque of this rear chain wheel (7.1 ) is transferred to left hand side chain wheel & crank (8.2) assembled on front rotating axle (8.3), assembled in bottom bracket assembly (8), on left side through chain (9).

5. The torque received from both riders is transferred to rear wheel from right hand side chain wheel & crank (8.1 ) to free wheel (1.6) (assembled on rear wheel hub assembly) through a chain (10).

6. Torque received by free wheel rotates rear wheel on the ground.

7. As the rear chain wheel (7.1 ) and left hand chain wheel & crank (8.2) have the same no of teeth rotate at the same speed. The right hand side chain wheel crank (8.1 ) also rotates at the same RPM.

8. Ratio of number of teeth on right hand side chain wheel and crank to number of teeth on free wheel, decide the RPM of rear wheel.

Considering rear shaft RPM as 50 the front axle rotates at 50 RPM, and considering 48 teeth on right hand side chain wheel and 18 teeth on freewheel the wheel rotates at 48/18 *50 =2.66*50=133.33 RPM.

The linear speed of the bicycles with 0.660m dia wheel equates to 133.33*0.660*TT*60 minutes =16589.34 meters. =16.59 km/hr

Example 3: Comparison with prior art bicycles

A comparison of overall length of mono single rider cycle, existing tandem cycle, and new mechanism included tandem bicycle showed that, the new tandem with invented mechanism has drastic reduction in overall length.

The reduction in size brings down the weight of the bicycle.

The reduction of length in current invention incorporated tandem, makes it easier for transportation and parking. Refer to Figure 14.

Increase in turning radius of wheels of bicycle is directly proportional to the wheel base. Therefore, reduced wheel base in current invention tandem brought down the turning radius of front and rear wheels also. This is apparent from the following:

The turning radius formula given below indicates that to reduce the turning radius of the wheels, wheel base should be as small as possible and turning radius angle should be as large as possible.

Refer to Figure 15, in which,

W= wheel base; R= the turning radius of the front wheel; r = the turning radius of the rear wheel; a = turning angle of the front wheel

When bicycle is turned wheel direction is perpendicular to its respective turning radii at all times.

Now considering turning angle 35°, and wheel diameter 660 mm,

It is evident from the formula that smaller is the value of W (wheel base) smaller is the turning radius. The cycles were practically driven and turned to check the least turning radius for them. Figure 16 shows the photographs taken during the turning trial of Tandem B whereas Figure 17 shows the photographs taken during the turning trial of tandem bicycle C of current invention. The results are reported below which prove in reduction of turning radius for the current invention tandem bicycle C compared to conventional tandem cycle B.

Applicant believes that the foregoing description explains the invention fully and particularly and also describes its operation, use and method by which it is to be performed. The embodiments shall not be construed to be limiting the scope of invention. The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope. This invention enables use of two riders energy easily in day to day life due to reduced wheel base and shorter wheel base. The use of these bicycles in day-to-day life even for shorter rides (2-20 km/day), will result in less consumption of petrol, diesel, and other energy.

Below are the prominent features and advantages achieved by the current inventions:

1. Reduced wheel base of tandem bicycle (wheel centre distance) reduces the turning radius. Therefore, is suitable to drive on same width of roads on which normal bicycles are driven.

2. Accommodating second rider close to first reduces overall length of the tandem bicycle and makes bicycle easy for balancing.

3. The overall weight of the tandem bicycles also comes down as the design of the frame allows smaller diameter tubes and hence the reduction of weight of tandem bicycle.

4. Tandem bicycle of current invention is transportable like normal bicycles.

5. The reductions in length of the tandem bicycle of current invention enable its parking in a smaller place also.

6. Overall reduction in weight of the tandem bicycle of current invention provide a great economic as well as utility wise benefit.