DESIGN DEVELOPMENT OF AN INDIGENOUS TRICYCLE RICKSHAW
Phase 6: Planning for consumption Step 1: Design for maintenance
5.5 Design up-gradation
Table 5.5 Comparison between Interim version of Dipbahan and Traditional rickshaw.
Dipbahan interim version Traditional rickshaw Remark
Cost Rs. 8,052.00 Rs. 6,500.00 Cost of Dipbahan is 24 % higher than traditional rickshaw
Weight 80 Kg 105 Kg Dipbahan is 24 % lighter in weight
than traditional rickshaw Category A.
Standard bought out component made by bicycle Industry
Standard bought out component made by bicycle Industry
These are same for both Dipbahan and Traditional rickshaw
Category B.
Main frame, fabricated Main frame made by bicycle Industry
Dipbahan do not require diamond frame due to the space structure employed and it is easier for the puller to get on and off the seat in absence of top cross bars.
Category C.
Chassis is also made from tubular sections using arc welding
Various parts for chassis is fabricated by blacksmiths and procured from him
In Dipbahan, mainframe and chassis is integrated using a space frame structure. Process of manufacture of this structure was not used for fabrication of traditional rickshaw in the local context.
Category D.
Passengers’ seat, seat back and floor panels are made in wood using carpenters and fitted to the tubular body shell.
Floor panels are covered with aluminium sheet; seat and seat back are covered with foam, coir fibre and vinyl fabric. Back panel is made out of mild steel sheet.
The body is fabricated in wood using carpenter is integral with the passengers’ seat back and floor panels. Foot board and outer side of the wooden body is covered with aluminium sheet. Seat is made separately in wood, fitted with spring and covered with coir fibre and reskin and is removable.
In the interim version, the process of fabrication of seat, seat back, floor panel etc. are similar to traditional rickshaw to utilise the readily available large pool of skilled worker in this area.
Category E.
Materials used for fabrication
Hood cover and rain guards are made in vinyl fabrics and fixed to the tubular frame. Rain guards are foldable
Foldable canopy is made in bamboo and covered with tarpaulin and fixed to the canopy and wooden body.
Usually no rain guards are provided in traditional rickshaw.
Based on the success and feedback on interim version (1st generation) of Dipbahan the work of 2nd generation Dipbahan was started. The strategy adopted for designing 2nd generation Dipbahan was value engineering. Every aspect of the design and component was analysed. Idea was to reduce bought out parts, number of materials and processes.
The analysis in brief is given below:
Analysis of the main frame:
In order to reduce the inventory through reduction in variety of sections in mild steel and to utilize the currently used materials and processes in rickshaw industry for ease of manufacture and maintenance through available skill in this industry, the process of manufacture of Dipbahan became an amalgamation of old and new. Observations are:
• The entire body shell was made in 25 mm outer diameter MS tubes and 40 X 5 mm MS flat along with bought out items like BB socket, body and frame socket etc. The main chassis was of sandwich type, one 40 X 5 mm MS flat welded with two tubes as seen in Fig. 5.30. Making of the frame was difficult, since the flat is to be welded to pipe of circular shape as well as both being of different thickness welding was not easy. Pipe of appropriate dimension to fit the readily available body socket was not readily available in local market.
• The frame at platform level was fracture prone as shown in Fig 5.30. Failure at the platform level was due to 3 dimensional bending of this element. Normally during bending of pipe with seam joint, the bending must be done in a way such that the seam is not stressed. However in a bend like at point X1, X2, this is not possible and failure was noticed at this point. Another reason for this failure was poor quality of pipe; due to low malleability, it used to deform during bending.
• Analysis of the process showed that the making of the chassis used to contribute heavily towards cost of fabrication, because it was based on sandwich design i,e, a 40mmx5mm flat bar fixed between two circular sections to strengthen the chassis in interim version of Dipbahan. This was to reduce the variety of MS section materials to keep a low inventory. Also joining of the two circular tube was labor intensive. Thus welding used to consume more time and money.
Fig. 5.30. Chassis of interim version Fig. 5.31. Chassis modified by CRD
Based on the failure of the frame, the NGO, Centre for Rural Development changed the process of manufacture by using a ready made diamond frame (Fig. 5.31, p164) to get rid of the problem that were not perceived by them as due to lack of quality consciousness in spite of guidance provided to them and the fact that jigs and fixtures are required to obtain better quality and input material must be checked for its quality before it is used for fabrication and once quality is degraded, it is difficult to solve teething problem through remedial measure and also adds to cost. NGO changed the chassis to solid square bar of 25mm (Fig. 5.31, p 164) and used angle of 20x20x4mm for making the platform. CRD also removed the bearing blocks (Fig. 5.32) against the specified design (Fig. 5.33)
Fig. 5.32 Rear axle without bearing block Fig. 5.33 Bearing block as per specification CRD manufactured rickshaw also had orientation altered for the front member compared to specified ones for it. Also frame structure was fabricated with defects (Fig. 5.34).
Fig. 5.34 Pipe fractured during bending
In case of seat, seat back, floor panels, wire mesh guard for luggage space and rear panel, it was observed that NGO was rampantly compromising on quality.
CRD did not wait and neither initiated the redesign of the interim version of Dipbahan to evolve next generation of it and resorted to short term measures as described above to solve the problem faced in the market, solely based on advise and feed back from users without appropriate analysis. This led to compromise on quality and design. Thus it was essential that next generation of Dipbahan must be designed to make it as fool proof as
possible so that a minimum standard and quality can be maintained. Concurrent design development of jigs and fixtures are identified as essential ingredient in this endeavour.
To start design development of next generation of Dipbahan, analysis of the process of manufacture of interim version of Dipbahan was resorted to.
Regarding the process of manufacture of interim version of Dipbahan, there are several types of processes involved along with different types of skills required even for the new design compared with traditional rickshaw manufacturing.
These are:
• Cutting mild steel sections, welding and grinding the body shell.
• Cutting of mild steel wire mesh, fabricating luggage guard at the rear and sides below the seat for luggage and fixing these to the body shell.
• Painting the body shell along with the back panel made in mild steel sheet.
• Carpentry work for seat, seat back and floor panels.
• Tailoring work for hood cover, seat cover and rain guards
• Fitting work for assembly of the bought out components, seat, seat back, floor panels, rain guards etc. to the body shell.
Thus it was essential that reduction in type of processes and variety of materials is to be achieved and requires analysis of the entire process of its fabrication. Also it is essential to improve the design based on feed back available from the field mentioned earlier.
Description of 2nd Generation Dipbahan: Dipbahan+ (Fig. 5.35 and 5.36, pp 168-169) Value analysis (Christopher, 1992; Chitale and Gupta, 1999) is a preplanned branching strategy for the designing of a product to reduce cost by finding the cheapest possible means of performing each essential function. Value analysis is also known as Value engineering. Its effect is to hasten and extend the exchange of thoughts between all persons who are in a position to discover the costs and to see ways of reducing them.
The stages involved in value analysis are:
(a) identification of elements, functions, costs, and values (b) search for alternatives at lower cost
(c) selection of functionally acceptable lower cost elements (d) presentation of selected redesign
Value engineering was used to arrived at redesigned Dipbahan+ version of the tricycle rickshaw. It was through various stages involved in value analysis that led to replacements of various components with newer alternative material components including fibre glass reinforced plastics for floor panels, side panels, rear panels etc. It also led to reduction in components for the Dipbahan+ version fabrication. Based on the Value engineering and feed back, the mainframe and chassis was made out of 50x25mm rectangular tubular mild steel sections (Fig. 5.37, p170). This could overcome all the draw backs of earlier design as well as reduced inventory and number of different
material. All bought out body, frame and seat sockets were no more required. For the entire body shell bought out part was only the BB socket.
In terms of varieties and numbers of processes involved, value analysis and resultant redesign led to increased productivity through reduction in amount of welding required for fabrication compared to interim version since sandwich type platform was no more required and parts orientation was easier compared to circular tubular section when these sections were replaced with rectangular tubular sections. Also grinding process for round tubular section could be eliminated once rectangular section was adapted. This led to lower cost of production. For the entire Dipbahan body, it was broken into sub frames. These are mainframe and chassis, seat structure, right side frame, left side frame and three numbers of cross binding members. Once all sub frames are ready, these are welded together using fixtures to fabricate the main shell of the Dipbahan (Fig.
5.38, p 170). This ensures accuracy of dimension. After the shell is ready, it is sent for spray painting using automotive paints and the process is same as in case of the interim version of Dipbahan.
For the body shell, all other aspects of design were kept similar to the interim version of Dipbahan except the radius of the rear elements were changed to reduce the curvature to accommodate advertisement space that is planner and can be screen printed.
Fig. 5.37 Mainframe and chassis Fig. 5.38 Assembly of body from sub frames The second important achievement in the second generation Dipbahan design was concurrent design of jigs and fixtures for fabrication of the Dipbahan. Details of design and development of jigs and fixtures are provided in Chapter 7 under section 7.1.2,p207.
The third important features of 2nd generation Dipbahan is introduction of Bio composites based on Jute fibre (Fig. 5.39, p 171) and Fibre glass Reinforced Plastics components.
This led to elimination of seat and seat back earlier fabricated using wood, foam, coir and covered with synthetic foam leather or rexin and floor boards fabricated using wood and covered with aluminum sheet. The rear panel and rear mudguards earlier fabricated in mild steel sheet were eliminated. Initial set of mild steel mudguards used in 1st version of the Dipbahan shown in Fig. 5.28 and 5.29 (p162) were out sourced from the parts available from tricycle and bicycle industry. In conventional rickshaws the rear mudguards due to its narrow width and position for fixing with body and details for the same were not suitable and used to throw mud and muck on the users. In case of 1st version of Dipbahan, mudguards were retained but their effectiveness increased through proper fixing and location. However due to small width these were found to be still impractical. Redesign of 1st version of Dipbahan provided the scope for entirely designing these to go with FRP based items and also to provide really effective set of mudguards in the rear. These are wider and non-rusting and hence fully met the objectives. These mudguard clad Dipbahan+ is shown in Fig. 5.35, 5.36, pp168-169.
Sides below the seat and lower part of the rear panel below the mild steel sheet fabricated out of wire mesh was also replaced with closed side covers and a larger rear panel. The wire mesh cover was ineffective in terms of protecting the luggage space from mud and slush getting spread by the rear wheels. Hood in the interim version was in synthetic foam leather / vinyl / rexin. All the above items were replaced with new and appropriately designed Jute based bio-composites. These are 10 in numbers 1 for seat, 1 for the seat back (Fig. 5.40, p 171), floor panels in two parts, side panels 2 numbers- for left and right, mud guards – 2 numbers for left and right, rear panel and the hood (Chapter 4, Table 4.2, p 142). All these were introduced after value engineering. Seat and seat back were integrated later to a single piece (Fig. 5.41, p 171).
Fig. 5.39 Jute based Bio-composite Fig. 5.40 Seat in two piece Fig.5.41 Integrated single seat The design development of the 2nd generation of Dipbahan was sponsored by M/s. Tim Steel Innovatives, Guwahati a SME specializing in fabrication business using iron, steel etc. Another SME, M/s. National Associates, Guwahati, a manufacturer of FRP products associated in development of composite components for the Dipbahan+. In addition Indian Jute Industries’ Research Association (IJIRA), Kolkata, under Ministry of Textiles, Government of India sponsored the design development of Jute Composite based components used in the Dipbahan+.
Thus the initial version of the Dipbahan continued to be manufactured by NGO, Centre for Rural Development, Guwahati and manufacturing of 2nd generation Dipbahan+ was started by M/s Timsteel Innovatives, Guwahati. This manufacturer tied up with M/s.
National Associates, Guwahati, for regular supply of FRP components to the former.
Thus there was no impact on manufacturability due to the introduction of FRP components for local producers except creating avenues for more business in their own area of specialization.
Since, the appropriate work was allotted to relevant concerns with their expertise, there was no fresh capital outlay required in order to produce these specific components and nobody had to learn new skills.
The fourth important feature is introduction of reduced gear ratio. One important observation during initial study of tricycle rickshaw was that, the gear ratio of the drive train is very high for the rickshaw to go up an inclination like a culvert that are very common in city like Guwahati. This compelled the rickshaw puller to get down from his seat and drag the rickshaw and this is very dehumanizing. Also due to longer length of the chain, it used to come off the sprocket frequently after some use. In the interim version of Dipbahan, this issue of gear system was not attended to due to the constraint of meeting targeted simplicity desired for ease of maintenance in commonly available rickshaw and cycle repairing shop and cost of manufacturing. This issue was addressed in the next version of the Dipbahan as a redesign exercise. One option was to fit the rickshaw with commercially available derailleur gear mechanism. However, these are not manufactured to take heavier load as required for rickshaw and also difficult to maintain.
Thus simple mechanism to reduce the gear ratio was attempted. Thus gear ratio was reduced with introduction of an intermediate shaft and two additional sprockets. The Table 5.6, p 172 and Fig. 5.42, p 172 provides the details of the same.
Fig. 5.42 Schematic diagram of layout of gears and pinions for gear reduction Table 5.6 Possible gear ratio with and without intermediate shaft
Number of full pedaling
Teeth on crank wheel
Teeth on rear axle free wheel
Intermediate shaft
Gear Ratio
Distance covered in meters
Pedaling per minute to cover 1 Km
Pedaling per minute at 10 Km per hour
Teeth on driver wheel
Teeth on driven wheel
1 48 18 - - 2.667 5.96 168 28
1 48 20 - - 2.4 5.36 187 31
1 48 22 - - 2.182 4.88 205 34
1 48 27 - - 1.777 3.97 252 42
1 48 27 27 22 2.182 # 4.88 205 34
1 48 22 27 22 2.68 5.97 168 28
1 48 27 22 27 1.45 3.23 310 52
1 48 22 22 27 1.777# 3.97 252 42
# Strikes through figures are the same ones possible through intermediate shaft but are directly available even without the intermediate shaft.
As seen in the above table, commonly used gear ratio in a traditional rickshaw is 1.777
However a higher gear ratio of 2.182 is also found in some cases.
To lower effort at starting, Dipbahan+ uses a still lower gear ratio of 1.45 possible through introduction of an intermediate shaft.
Information in Table 5.6 is based on following calculations.
Calculations:
For single stage gear reduction
Number of revolution of crank wheel given by n1
Number of revolution of sprocket wheel fixed to rear axle given by n2
Number of teeth of crank wheel given by T1 = 48T
Number of teeth of sprocket wheel at rear axle given by T2 = 22T Then n1/ n2= T2/ T1
Since n1 is 1, n2= T1/ T2 = 48/22 = 2.18 i.e. for every rotation of the pedal by the rider, the rear wheel will rotate by 2.18 turns. Here gear ratio is T1/ T2 = 48/22 = 2.18
Considering the diameter (d) of the rear wheel as 71 cm (28”), in one pedaling, the tricycle will travel a distance of n2 π d = 2.18 x 3.14 x 71 = 487 cm (rounded off) or 4.87 meters.
To travel one Kilometer, numbers of pedaling required will be = 1000/4.87 = 205 times.
Considering a speed of 10 Km per hour, number of pedaling per minute (ppm) to cover 1 km will be 205/6 = 34 ppm
For two stage gear reduction through introduction of intermediate shaft Number of revolution of crank wheel given by n1
Number of revolution of sprocket wheel fixed to intermediate shaft given by n2
Number of teeth of crank wheel given by T1 = 48T
Number of teeth of driven sprocket wheel at intermediate shaft given by T2 = 27T Number of teeth of driver sprocket wheel at intermediate shaft given by T3 = 22T Number of revolution of sprocket wheel fixed to rear axle given by n3
Number of teeth of sprocket wheel at rear axle given by T4 = 27T Then n1/ n2= T2/ T1
Since n1 is 1, n2= T1/ T2 = 48/27 = 1.78 (rounded off two 2 decimal point) Again,
n2/n3= T4/ T3 or n3 = n2 x T3/ T4 = n3= T1/ T2 xT3/ T4 (replacing n2 with T1/ T2) n3 = 48/27x 22/27 = 1.45 (rounded off two 2 decimal point)
For every rotation of the pedal by the rider, the rear wheel will rotate by 1.45 turns. Here gear ratio is T1/ T2 xT3/ T4 = 48/27x 22/27 = 1.45
Considering the diameter (d) of the rear wheel as 71 cm (28”), in one pedaling, the tricycle will travel a distance of n2 π d = 1.45 x 3.14 x 71 = 323 cm (rounded off) or 3.23 metres.
To travel one Kilometre, numbers of pedaling required will be = 1000/3.23 = 310 times.
Considering a speed of 10 Km per hour, number of pedaling per minute (ppm) to cover 1 km will be 310/6 = 52 ppm (rounded off to nearest integer)
Thus it is seen that for traveling same distance with higher gear ratio will require more less number of pedaling per minute against lower gear ratio requiring more numbers of pedaling per minute.
However considering torque applied by the human being as same, he will required to apply less torque per pedaling with a low gear ratio compared to higher gear ratio. Thus there is a trade off between the two. High gear ratio is advantages for continuous operation in speed and lower gear ratio is advantageous in interrupted operation like in congested city, where stopping and starting is frequent.
The introduction of the reduced gear ratio made the rickshaw riding easier even with higher load and going up a slope, but it reduced the speed and distance covered by the rickshaw for a fixed number of pedaling by the rickshaw puller. On busy roads, it was not evident but in an empty road, this was not preferred by the rickshaw pullers and a shifting gear mechanism was designed for the Dipbahan+. The final design of Dipbahan+
is presented in Fig. 5.35 and 5.36 in pp 168-169.
Impact of incorporating the gear mechanism in the 2nd generation Dipbahan+ on overall design was:
Weight of the geared tricycle rickshaw increased by 8 Kgs compared to ungeared one.
Performance of the rickshaw improved during initial start up i.e. starting from stand still required less effort compared to ones without gear mechanism. However on long run, where the rickshaw can go faster, it suffered since lower gear reduced its speed and less effort to run the rickshaw did not compensate for speed reduction, since rickshaw pullers wanted to go faster too, after initial effortless start.
In terms of price, it increased the cost of the rickshaw by Rs. 750.00 due to incorporation of the additional components and processes during manufacturing.