Freight Bike Project Scope Reluctant Macro Driver Alex Cummins Christopher Dalamagas John Donald Ozmar Estacio
CONTENTS PG. 1. BRIEFING PHASE - SCENARIO - AUSTRALIA POST MISSION STATEMENT -LIMITATIONS PG. 5. CONCEPT DESIGN PHASE - GEODESICS AND TENSEGRITY PRINCIPALS - MATERIAL CONSIDERATION PG. 8. DETAIL DESIGN PHASE PG. 9. REPORTING PHASE PG. 10. SUMMARY PG. 11. TIMELINE PG. 12. APPENDIX
Briefing Phase With the increased awareness of greenhouse gases produced by everyday living there is now a need to reduce our carbon footprint on the earth. In our project, Australia Post has had to align its practices with the Federal government enterprises and departments and reduce its carbon dependence by 50%. Australia post have already put in place environmental management systems which focus on the environmental impacts of everyday living, however, further measures need to be taken. The use of Bicycles is the best and most effective way to cut down greenhouse gases.
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Scenarios Australia Post needs a series of freight bikes that can collect and transport mail and parcels around the Melbourne CBD. Using pre-existing Postal bicycles our task is to increase the freight capacity by retrofitting separate detachable components.
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The Australia’s Post’s Mission: • • • • •
Innovative and easy to use products and services Friendly service by knowledgeable staff Consistent on-time Delivery; Value for money; and Modern, efficient networks
By looking over Australia’s Post’s Mission statement there are design requirements necessary for our project to be successful. • • •
Reliable and Strong, Our Freight bike can’t break down or in the event it does has to be easy to fix. The bike has to be comfortable and easy to ride with out upsetting the rider as releasing such a project the bike will constantly be in the public eye. The importance of maintaining efficient protocol for delivering mail.
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Project Limitations There are many limitations in our project and due to the type of scenario we have, the problems are strongly linked to cost. We are dealing with a reluctant macro driver scenario that has to be cheap, lightweight and fit to pre-existing Australia Post type bike frames without making any alteration to the frame or its riding geometry. This proposes a problem as the most efficient freight bikes don’t use normal riding geometry, this forces the freight bike to use retrofits to allow extra capacity, and this method is not ideal and is not the best for this project. The following limitations are outlined • • • • •
Bike width cannot be greater than 300mm thus leav- ing clearance 350mm on either side provided that the standard bicycles lanes remain 1000mm. Materials have to be strong and lightweight The retrofit has to be secured and cannot disrupt the riders maneuvering We cannot change the geometry of pre-existing postal bikes The bike has to be able to hold a large capacity of mail
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Concept Design Phase Due to the nature of the project we have to explore building and design methods to strengthen our freight bike. We cannot just rely on the types of materials we use, however the types of materials we do use influence the strength, stiffness and weight of the freight bike other design principles work hand in hand. By utilizing design concepts such as Geodesics and Tensegrity we can explore various methods and techniques to build an efficient working prototype. Geodesics. Whilst we aren’t going to get lost in mathematical equations over the theory of geodesics, we will however, take the basic principle and take the shortest paths between two points to triangulate and increase strength in areas where needed. This will impact our design by strength and overall appearance. By making mock-ups and test models Key stress points can be identified in the freight bike weeks before production of a 1:1 model. With the simple principles of geodesics we can test our models on small and large scales with the same principles of geodesics coming into effect. Tensegrity. Tensegrity has never really been introduced to bicycles due to the success of the diamond frame. However, in our project the diamond frame is not the best design, as we have to incorporate a load-bearing zone. Tensegrity could not work for bicycles although it is a very interesting and useful design principle that if utilized correctly can be very successful.
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Materials Stiffness Stiffness affects the riding qualities of a bike frame, since a frame suffers no permanent deformation in normal riding. Stiffness is determined by a property of the material called “elastic modulus” Elastic modulus is essentially independent of the quality or alloying elements in a given metal. All kinds of steel, for instance have basically the same elastic modulus. Strength Strength relates to the crash-worthiness or general durability of a frame, but has no effect on the riding properties. Strength is determined by a property of the material called “yield strength.”Yield strength is very much affected by the quality, heat treatment and alloying elements used in a particular brand/model of tubing. Weight In addition to the strength and stiffness, there’s also the question of how heavy a given volume of the material is. This is called “specific gravity.”Like stiffness, the specific gravity of a given metal is not significantly affected by the addition of different alloying elements.
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Materials (continued) One should take the nature of the material into account in selecting the diameter and wall-thickness of each piece of tubing that goes to make up the frame. Stiffness is mainly related to the tubing diameter. Strength is mainly related to the wall thickness, though diameter also enters into it. Weight is affected both by diameter and wall thickness. Possible Materials • • • • • •
Titanium , is very strong and lightweight (metal) Aluminum alloys, lightweight but not as strong (metal) Steel, very strong but heavy (metal) Rubber, soft and flexible (plastic) Polystyrene, strong rigid plastic(plastic) Nylon Fabric
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Detail Design Phase Once a direction has been established, further considereation to design will begin. We will begin to develop initial concepts to a point where it may be produced/manufactured using all relevant research found through the briefing and concept design phases - including experimentation through geodesic and tensegrity structures. This will include fully developed and resolved manufacturing drawings, prototypes, and visualisations
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Reporting Phase This is where we will present our final report on the design and point the way forward for future iterations and developments. This will involve a thorough evaluation of the design - identifying strengths and weeknesses and possible improvements that can be made, how things could have been done differently and what we possibly should have done.
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Summary In geometry, there’s nothing as strong as a triangle. Diamond-frame bikes consist basically of two triangles. The elegance and simplicity of this design is very hard to improve upon. Billions of diamond-frame bikes have been made from tubing for over a century, and during that time, hundreds of thousands of very smart people have spent billions of hours riding along and thinking about ways to fine-tune the performance of their bikes. The tubular diamond frame has been fine tuned by an evolutionary process to the point where it is very close to perfection, given the basic design and materials.
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Timeline Week 1 - 3 - project scope document - 9x9 photo matrix - precedents - scenarios and stories Week 4 - 8 Design and technical resolution stage - manufacturing drawing sets - presentation illustrations - 1:4 scale model Week 8 - 14 re-visioning and reporting
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APPENDIX - materials research - cargo - bicycle lanes - 9x9 photo matrix
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MATERIALS Stiffness, Strength and Weight Strength and stiffness are different properties that are often confused with one another. It is important to understand the difference, if you want to understand differences in frame materials. Imagine you clamp one end of a metal bar in a vise, and you hang a weight on the free end, causing the bar to flex temporarily. When you remove the weight, the bar snaps back to its original shape. Different materials will flex different amounts for the same amount of force applied. This is stiffness. Now imagine hanging a heavier weight on the bar, so heavy that it becomes permanently deformed. When you remove this weight, the bar does not snap back all the way to its original shape, but remains bent to some extent. When the metal changes shape permanently, it is said to “yield.” Different materials can withstand different amounts of force before yielding. This property is strength. Stiffness Stiffness affects the riding qualities of a bike frame, since a frame suffers no permanent deformation in normal riding. Stiffness is determined by a property of the material called “elastic modulus” Elastic modulus is essentially independent of the quality or alloying elements in a given metal. All kinds of steel, for instance have basically the same elastic modulus. Strength Strength relates to the crash-worthiness or general durability of a frame, but has no effect on the riding properties. Strength is determined by a property of the material called “yield strength.”Yield strength is very much affected by the quality, heat treatment and alloying elements used in a particular brand/model of tubing. Weight In addition to the strength and stiffness, there’s also the question of how heavy a given volume of the material is. This is called “specific gravity.”Like stiffness, the specific gravity of a given metal is not significantly affected by the addition of different alloying elements. Here are some properties of the three common frame metals: Material Modulus Aluminum 10-11 Steel 30 Titanium 15-16.5
Yield Point Specific Gravity 11-59 (4-22 annealed.) 168.5 46-162 490 40-120 280
Note that the modulus (stiffness) and specific gravity (weight) are pretty much independent of the quality, heat treatment, or alloying agents of the materials. For instance, all steels, from the “gas-pipe” used in department-store bikes to the exotic alloys used in multi-thousand dollar bikes have a modulus of 30, and a specific gravity of 490. There are, however, real differences in yield strength among different qualities of tubing. This modulus value shows that if you were to build identical frames from the 3 materials, using the same tubing diameters and wall thicknesses, the aluminum frame would be only 1/3 as stiff as a steel one, and the titanium frame only half as stiff. The yield values show that the aluminum frame would be very much weaker, in the sense of being more easily damaged than either the steel or titanium frames. The specific gravity values show that the aluminum frame would only weigh 1/3 what the steel frame weighs, while the titanium frame would be roughly half the weight of the steel one. One should take the nature of the material into account in selecting the diameter and wall-thickness of each piece of tubing that goes to make up the frame. Stiffness is mainly related to the tubing diameter. Strength is mainly related to the wall thickness, though diameter also enters into it. Weight is affected both by diameter and wall thickness. A frame manufacturer can make trade-offs by selecting different tube diameters/wall thicknesses, allowing a frame to be made stiffer, or stronger, or lighter. Steel vs. Titanium Identical steel vs. titanium frames would be about equal in strength, but the titanium frame would be about half the weight and half the stiffness. Such a frame would likely have a whippy feel due to the reduced stiffness, especially in loaded touring applications. To compensate, builders of titanium frames use somewhat larger diameter tubes to bring the stiffness more into line with what riders like. This tends to increase the weight a bit, but by making the walls of the larger tubes a bit thinner, they can compensate to some extent, and come up with a frame that is still lighter than a normal steel frame. Steel vs. Aluminum The situation with aluminum is even more pronounced. The “identical” aluminum frame would be 1/3 as stiff as steel, roughly half as strong, and 1/3 the weight. Such a frame would be quite unsatisfactory. That’s why aluminum frames generally have noticeably larger tubing diameters and thickerwalled tubing. This generally results with frames of quite adequate stiffness, still lighter than comparable steel ones. Large diameter thin-wall tubing. The advantages of larger tubing diameter can, theoretically be applied to steel construction, but there’s a practical limit. You could build a steel frame with 2 inch diameter tubing, and it would be stiffer than anything available – stiffer than anybody needs. By making the walls of the tubes thin enough, you could make it very, very light as well. Why don’t manufacturers do this? Two reasons: The thinner the walls of the tubing, the harder it is to make a good joint. This is the reason for butted tubing, where the walls get thicker near the ends, where the tubes come together with other tubes. In addition, if the walls get too thin, the tubes become too easy to dent, and connection points for bottle cages, cable stops, shifter bosses and the like have inadequate support. Stiffness and ride quality Frame stiffness (or the lack of it) doesn’t have as much effect on ride quality as many people would lead you to believe. Let’s look at it from a couple of different directions: Torsional/lateral stiffness This is mainly related to the stresses generated by the forces you create from pedaling. Any frame will flex around the bottom bracket a bit in response to pedaling loads. This flex can be felt, and many riders assume that it is consuming (wasting) pedaling effort. Actually, that’s not the case, because the metals used in bicycle frames are very efficient springs, and the energy gets returned at the end of the power stroke, so little or nothing is actually lost. While there is no actual loss of efficiency from a “flexy” frame, most cyclists find the sensation unpleasant, and prefer a frame that is fairly stiff in the drive-train area. This is more of a concern for larger, heavier riders, and for those who make a habit of standing up to pedal. Another area where lateral stiffness can be an issue particularly to the touring cyclist is the rear triangle, when there’s a touring load on the rear rack. A frame that is too flexi in this area will feel “whippy” and may be prone to dangerous oscillations at high speeds. Most of this flex is usually in the luggage rack itself, but there can be enough flex in the seat stays to aggravate this condition.
Vertical stiffness Bumps are transmitted from the rear tire patch, through the tire, the wheel, the seat stays, the seat post, the saddle frame, and the saddle top. All these parts deflect to a greater or lesser extent when you hit a bump, but not to an equal extent. The greatest degree of flex is in the tire; probably the second greatest is the saddle itself. If you have a lot of seat post sticking out of a small frame, there’s noticeable flex in the seat post. The shock absorbent qualities of good quality wheels are negligible...and now we get to the seat stays. The seat stays (the only part of this system that is actually part of the frame) are loaded in pure, in-line compression. In this direction, they are so stiff, even the lightest and thinnest ones, that they can contribute nothing worth mentioning to shock absorbency. The only place that frame flex can be reasonably supposed to contribute anything at all to “suspension” is that, if you have a long exposed seat post that doesn’t run too deep into the seat tube, the bottom end of the seat post may cause the top of the seat tube to bow very slightly. Even this compliance is only a fraction of the flex of the exposed length of the seat post. The frame feature that does have some effect on road shock at the rump is the design of the rear triangle. This is one of the reasons that touring bikes tend to have long chain stays--it puts the rider forward of the rear wheel. Short chain stays give a harsh ride for the same reason that you bounce more in the back of a bus than in the middle...if you’re right on top of the wheel; the entire jolt goes straight up. Where Comfort Comes From If you’re looking for a comfortable ride, it is a mistake to focus on the particular material used to build the frame. There are differences in comfort among different bikes, but they are mainly caused by: Tire choice. Wider, softer tires make more difference to ride comfort than anything to do with the frame. Unfortunately, many newer sport bikes are poorly designed when it comes to tire clearance. For the last decade or more there has been a fad to build frames with very tight tire clearance, although there is no performance advantage whatsoever to such a design. Such bikes cannot accept anything but super skinny tires, and, as a result, there’s no way they can ever be really comfortable. Frame geometry. Generally, frames with longer chain stays, and less vertical seat-tube and head-tube angles are more comfortable. This doesn’t make them any slower, but may reduce maneuverability (also known as twitchiness.) Carbon Fiber Carbon fiber is an increasingly popular frame material, but it is fundamentally different from metal tubing as a way to construct frames. Because of the fibrous nature of this material, it has a much more pronounced, “grain” than metal does. A well-designed carbon fiber frame can have the fabric aligned in such a way as to provide maximum strength in the directions of maximum stress. Unfortunately, in bicycle applications, carbon fiber is not a fully mature technology, as tubular-construction metal frames are. Bicycles are subjected to a very wide range of different stresses from many different directions. Even with computer modeling, the loads can’t be entirely predicted. Carbon fiber has great potential, but contemporary carbon fiber frames have not demonstrated the level of reliability and durability that are desired for heavy-duty touring use. In particular, a weak point tends to be the areas where metal fitments, such as fork ends, bottom bracket shells, headsets, etc connect to the carbon frame. These areas can be weakened by corrosion over time, and lead to failure. In geometry, there’s nothing as strong as a triangle. Diamond-frame bikes consist basically of two triangles. The elegance and simplicity of this design is very hard to improve upon. Billions of diamond-frame bikes have been made from tubing for over a century, and during that time, hundreds of thousands of very smart people have spent billions of hours riding along and thinking about ways to fine-tune the performance of their bikes. The tubular diamond frame has been fine tuned by an evolutionary process to the point where it is very close to perfection, given the basic design and materials. If there is to be any major improvement in frame design, it must come either from a completely different type of construction process, such as carbon fiber, or cast magnesium; or a completely different type of design, such as a recumbent.
Cargo During Our project there will be considerable attention to the Cargo our freight bike has to carry. The type of mail and parcels that will be collected from post boxes vary in size and weight thus putting more stress on our design as it needs to be able to hold heavy, lightweight and irregular shaped parcels and letters. The following section runs through the dimensions of Standard mail distributed by Australian Post. - Mail (envelope sizes and weights) - Packages (tubes and boxes, sizes and weights) - How the mail is collected from the Post Box - Post Box Dimensions - Sack size Mail Envelopes (Name, Size, Suitable For) - DL, 110 x 220mm, 1/3 A4 - C7/C6, 81 x 162, 1/3 A5 - C6, 114 x 162, A6 - C6/C5, 114 x 229, 1/3 A4 - C5, 162 x 229, A5 - C4, 229 x 324, A4 - C3, 324 x 458, A3 - B6, 125 x 176, C6 - B5, 176 x 250, C5 - B4, 250 x 353, C4 - E3, 280 x 400, B4 - 11B, 90 x 145 - B13, 120 x 235, 1/3 A4 Packages Padded Bags - Size 0, 127 x 178mm - Size 1, 151 x 229mm - Size 2, 215 x 280mm - Size 5, 266 x 381mm - Size 7, 361 x 483mm Tough Bags - Size B2, 216 x 275mm - Size B4, 241 x 338mm - Size B5, 266 x 376mm - Size B6, 304 x 435mm Expandable Tough Bags - Size GC, 75mm gusset, 370 x 405mm - Size GL, 115mm gusset, 670 x 405mm Mailing Boxes - Size A5 BC, 220 x 160 x 77mm - Size A4 BM, (minimum deemed weight 2kg) 310 x 225 x 102mm - Size BP, (minimum deemed weight 4kg) 400 x 200 x 180mm - Size A3 BT, (Minimum deemed weight 5kg) 430 x 305 x 140mm - Mailing/Storage Box BW (Minimum deemed weight 8kg) 405 x 300 x 255mm - Video Cassette/DVD Box VCB, 220 x 145 x 35mm TOUGHpak A4 - TOUGHpak A4, (Minimum deemed weight 2kg) 363 x 212 x 65mm Mailing Tubes - 60/420, 60 x 420mm long - 60/660, 60 x 660mm long - 90/850, 90 x 850mm long Special Purpose Products - Diskette and Photo Mailer DP, 150 x 200mm - CD Mailer CD, 145 x 127 x 10mm WINEpak - WINEpak single WP, (Minimum deemed weight 2kg) - WINEpak twin pack WP2, (Minimum deemed weight 4kg)
How the mail is collected from the Post Box Each Post Box is fitted with a mail sack. The sack hangs from hooks inside the box, ready to catch mail. This means, in order to empty the Post Box, one simply opens it up, and takes out the sack of mail. The sack is then stored in a Post van and eventually taken back to the distributor. An empty sack is then fitted to the Post Box, ready to go. Post Box Dimensions The Post Box is a standard size across the Melbourne CBD, which is the area under focus. Its dimensions are as follows: W – 585mm H – 1500mm D – 435mm Although the boxes are uniform in size, there are often multiple boxes next to each other at busy locations. Therefore, collecting from a specific location could result in 2 or 3 times more volume/weight of mail than another location. Sack Size As the mail sack sits inside the Post Box, obviously its dimensions must be approximately equal to that of the box. The only exception is the height of the sack, as it can’t be hanging from higher than the slot/drawer of the box. Therefore its dimensions are approximately as follows: W – 585mm H – 1200mm D – 435mm Without having any access to a full sack of mail, only estimates for one’s weight could be obtained. According to a local Post Office worker, a sack of mail will weigh anywhere from 0-20kg upon collection.
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The problem of narrow “bike lanes” : the case of “shared parking lanes”. Cyclists require an operational space of minimum width 1000mm with 300-500mm or more clearance on both sides, depending on the circumstances. This is a design fundamental. Often facilities appear to be, or might be assumed to be, safe yet they do not meet these minimum “operational” requirements. The “BIKE LANE” in fig 1 is an example from Brisbane (Australia) where there is inadequate space, thus creating a real risk for unsuspecting or novice cyclists, especially if a car door is opened suddenly. Should this occur, the cyclist may react by turning away, or be deflected away, in both cases, into and in front of fast moving vehicular traffic.
! Fig 1: BIKE LANE with inadequate space for cyclists
The “problem” with narrow “bike lanes” is therefore that they potentially convey a false sense of safety. However, the “problem” also includes regulatory obligations eg a cyclist leaving the “bike lane” is changing lanes and therefore must not change lanes unless safe to do so. That is, the “bike lane” creates a legal obligation and responsibility on the cyclist leaving the “bike lane”, irrespective of the circumstances. This is not only important in the case of avoiding car doors or walk-out pedestrians or indeed debris on the “bike lane”, it is also important if attempting to turn right when leaving the “bike lane”. A further “problem” is the motorists expectation that cyclists will in fact stay, and are expected to stay, in the “bike lane” thus creating a potentially false sense of a reduced need for motorists to be concerned about the cyclists. As one of a number of trials of various infrastructural facilities for cyclists in Brisbane (Australia), a section of “shared parking” “bike lane” was constructed to the minimum operational requirements. The following photographs illustrate the major operational dimensions. The width provided for car parking should be minimised, however, the space should also allow for some latitude.
As can be seen in Fig 2, there is adequate space for the cyclist. In Figs 2 and 3, the marked car bay is 2100 wide while the tape measure is set at 2000.
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Fig 2 shows car bay widths and cyclist
Fig 3 shows detail of car bay widths
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The space between the car and the edge line (and adjacent traffic) should be maximised. In this case, the total width from kerb face to edge line is in excess of 4000 while the tape measure is set at 3500.
Fig 4 shows total “bike lane� width
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The next photo (Fig 5) shows the same situation but with the car door on “hold open” which is not fully open. As can be clearly seen in this photo, there is adequate space for the cyclist with clearances from both the car door and the edge line in this example but not with the 3500 width.2000.
Fig 5 shows car door at the “hold open” position
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The next photo (Fig 6) shows a more distant view. In Fig 7, the photo includes the standard nominal width 1100 BIKE symbol indicating that this is a “bike lane”. As this BIKE symbol is also the same width as the operational space for a cyclist, it can be seen how the 3500 measurement would result in the BIKE symbol being located adjacent to the car bay with the majority of the BIKE symbol covered by the swept path of the opened car door and little if any clearance to adjoining traffic.
! Fig 6 shows a more distant view including a standard 1100 wide BIKE symbol
The use of a 3500 wide shared parking lane raises extremely serious issues in regard to compromising the safety of cyclists given that a “bike lane” implies safe space on the road. This is especially the case where it might be assumed the facility is “safe”. This situation is further compromised if the adjoining lane widths are also minimal width. As can be seen in the final photo (Fig 7), while the space provided in this trial looks to be quite large and perhaps even excessive, in fact, this is the appropriate width to maintain the operational clearances.
In this photo, the tape measure is set at 4000 for comparison with the location of the BIKE symbol marking the “bike lane”.
! Fig 7 shows the actual space required for “safe” cycling in a “shared parking lane”.
In this trial of the required space on a typical urban road in Brisbane, it is clear that rather than compromise the safety of cyclists, the compromise was to remove parking on one side of the road in order to provide an adequate (but arguably minimum width) “bike lane” on both sides of the road while maintaining adequate traffic lanes on a 60km/h arterial road. Arguably, “safe” facilities should always be provided where, as in this case and in general in urban areas, a diversity of cyclist types and competencies is to be expected. In other trials in Brisbane where parking has been considered necessary on both sides of the road, the more recent use of the yellow BIKE symbol to indicate how to “share the road” provides a better compromise than a “narrow bike lane” in that it allows the operational space for the cyclists (represented in each case by the location and width of the 1100 nominal width of the BIKE symbol) to be located further from the cars. Because the yellow BIKE symbol is not enclosed by an edge line, cyclists are not required (or expected) to travel within their “lane” but rather may choose to “share the road”, and therefore are treated as any other vehicle because bicycles are “vehicles” under the road regulations. Reference: http://www.yeatesit.biz/transfiles/problem_narrow_bike_lanes.htm
PHOTO MATRIX
Australia Post John, Alex, Ozmar, Chris