Isreali inventor Izhar Gafni has designed award winning industrial machines for peeling pomegranates and sewing shoes. He’s also a bike enthusiast who’s designed a lot of carbon fiber rigs. But one day, he’d heard about someone who’d built a cardboard canoe. The idea drilled its way into his consciousness, and ultimately, led him to create a cardboard bike called the Alfa.
The Alfa weighs 20lbs, yet supports riders up to 24 times its weight. It’s mostly cardboard and 100% recycled materials, yet uses a belt-driven pedal system that makes it maintenance free. And, maybe best of all, it’s project designed to be manufactured at about $9 to $12 per unit (and just $5 for a kids version), making it not only one of the most sustainable bikes you could imagine, but amongst the cheapest, depending on the markup.
But as the above video documents, the design process was arduous. Engineers told Gafni that his idea was impossible. Yet he realized that paper could be strong if treated properly. As in crafting origami and tearing telephone books, he explains, “[if] you fold it once, and it’s not just twice the strength, it’s three times the strength.”
The development to what you see today took three years. Two were spent just figuring out the cardboard complications--leading to several patents--and the last was spent converting a cardboard box on wheels to a relatively normal looking bike.
At the moment, Gafni is working with a company to raise the funds to finalize manufacturing processes for his adult and child bikes and then actually put them into production. And if they’re able to pull this off, and the Alfa is everything it’s promised to be, it could be an absolutely paradigm-shifting idea in the transportation industry.
Bikes are amongst the most efficient transportation systems in the planet, converting up to 99% of a person’s power into mobility that’s up to five times faster than walking. Imagine the impact for developing nations, assuming the Alfa (or a derivative) could handle itself on unpaved roads--especially when fitted with an optional small motor upgrade to enhance range--or what you could do in a small school district where every child could be given a bike in place of a few days of school-bus gas.
Then again, the best way to score yourself a recycled bike is just to go to a pawn shop and buy one used. No doubt, it’s a little less design-spectacular, but $10 sure can go a long way at a good old garage sale.
Cut the conduit to the appropriate lengths. The sides will start out at 36 inches long, and will be made from the 1/2 inch tubing. The seat stretchers will each be 24 inches long and made from the 3/4 inch tubing. Cut each piece of tubing in half, then clean the cut ends with a file.
2
Bend the conduit pieces to form the seat sides. Each side will have to be bent exactly the same way, and each bend should be made in plane. First, bend one of the 36-inch pieces 45 degrees at the end so the center of the bend is at about 4 1/2 inches. Next, bend the conduit 90 degrees in the opposite direction, with the bend centered 12 1/2 inches from the end. Then, make two 15-degree bends in the same direction as the first bend, centered at 19 1/2 and 22 1/2 inches from the end. Finally, bend 20 degrees opposite the initial bend, centered at 28 3/4 and 32 1/4 inches. Perform the same bends on the other one.
3
Bend the conduit pieces to form the seat stretchers. Bend one 3/4 inch conduit piece 60 degrees, centered 6 inches from one end. Do the same bend, in plane and in the same direction, 60 degrees and 6 inches from the other end. Perform the same two bends on the other piece to form a second seat stretcher.
4
Braze the seat together. Connect the ends of one of the seat stretchers to the seat sides, centered between the 90 degree and 45 degree bends, approximately 8 inches from the end, keeping the seat sides in plane with one another. Connect the other seat stretcher between the adjacent 15 and 20 degree bends, about 25 1/2 inches from the end. Make fish mouth cuts on the ends of the seat stretchers to fit them to the seat sides, then braze each connection.
5
Attach the fabric cover to the seat. The fabric comes 54 inches wide, so cut it in half to form two 36 inch by 27 inch pieces, one of which will be used for this seat. Center the fabric on the seat so the long dimension goes along the vertical axis of the seat. Fold the ends over the sides of the seat, cutting where the seat stretchers are so as to fold around them, then hold them in place with the straight needles. Sew, using the fishing line, keeping as close to the seat rail, and maintaining as much tension on the seat as possible.
6
Finish sewing the seat together. Cut along the seat rails to remove the excess fabric, then trim the extra fabric at the ends, leaving about 1 1/2 inches of fabric at either end. Fold each end over, and sew a seam at the top and bottom of the seat, again taking care to maintain the tension in the seat.
The seats on both Woody & TreeBike were constructed of salvaged 7/8" OD aluminum CB antenna tubing. The main tubes were cut to 35" and bent on a borrowed, hand operated tubing bender as shown in the drawing. The front edge was joined by a straight tube and the other two cross-tubes were bent to allow 2" of clearance below and on the back of the seat.The dimensions given are for Woody's seat. Sue's is similar but main tubes were bent at 3" and 13". Seat width is 1" narrower all around.
I used a 7/8" Milwaukee hole saw to cut the ends of the tubing to nice tight fitting joints.
If I were to do the job over again I would take the seat parts, assembled in a jig, to someone who does a good job welding aluminum. What I did was solder all of the joints into massive globs and then endlessly grind the mess down toa reasonably smooth joint. There is a fine line between smooth, good looking joints and weak, useless joints. The solder I used is MG Welding Products' 'MG 470", described as a 'Maximum strength self fluxing solder for joining, build-up and hardfacing aluminum'. I believe that the 1/8" diameter rods cost around $35 for two pounds.
I added a couple of aluminum tubing braces after the first test ride. The seat reclined more with each hard pedal stroke due to the weakness of the main tubing. The braces are pop-riveted on and covered with shrink-wrap. As it turns out they give a more secure feeling by providing some lateral support and are not a problem when getting on and off the bike.
Seat supports were made by sewing loops in each end of lengths of 1" nylon webbing as shown above. These straps were then wrapped around the frame and secured with heavy-duty plastic wire ties. You can adjust the amount of support by repositioning the straps or adjusting the tension on the ties. More or fewer support straps can be used as needed.
The seat material is nylon mesh and Cordura nylon fabric purchased from an upholstery/tent & awning shop. The mesh was cut to fit inside the frame with 1" space all around. Then 3-1/2" strips of Cordura were folded over the edges of the mesh and sewn on as edge reinforcement. Using a piece of 1/4" steel rod and a propane torch, I heated the rod and melted holes at 2" intervals along both sides. This creates holes that are self-finished and very strong. Finally, 1/4" brass gromets were installed in the holes for further reinforcement. The seat was laced into the frame using some approx. 1/8" diameter shiny polyester cording purchased from a fabric shop.
The seat mounts to the frame with two pieces of aluminum angle which run between the front and bottom cross-tubes. I cut out a lot of the angle material to reduce weight.
Speaking of weight, this seat, complete with mounting as shown and with fabric and lacing weighed in at less than 3 1/2 lbs.
Three of the four open ends of tubing were finished by epoxying in short lengths of 3/4" wood dowel then rounding the ends. This was done as a safety measure. While testing Woody I tipped over while hardly moving and 'apple cored' my ankle. Not a pretty sight even today.
At left you can see how the top left tube was finished. A longer dowel was first drilled to the size of a light-weight fiberglass sectional tent pole, then glued into the tube like the others. A little sewing of some bright yellow ripstop material and the safety flag was done. These bikes are low and don't present a very large or recognizable picture to car drivers. The flags are something drivers are used to associating with bikes ... and they make me feel a bit more visible.
Total cost per seat, not counting labor, was less than $35. I hope this information helps you construct your own recumbent bike seat - or decide not to, as the case may be. These seats have worked well for us. If you have any questions or comments please contact me.
Tips & Warnings
When bending the conduit for the seat rails, make the corresponding bend on each piece before moving on to the next bend. This way, you can make sure that the bends all line up when it is easier to fix, before all the bends are made.
Aufhauser Oxyacetylene Braze Welding copper alloy filler rods and fluxes enable the joining of many base metals. They are especially useful on steel and cast iron.
Braze welding is similar to torch brazing, except that joint openings may be wider and the distribution of filler metal takes place by deposition rather than by capillary flow. Equipment and some filler metals used in braze welding are the same as those used in torch brazing.
In braze welding of ferrous metals, the base metal is not melted. The filler-to-base-metal bond is the same as in torch brazing. Flux is applied to the joint surfaces, which, together with the surrounding area, are preheated to the point where the filler metal will wet or "tin" these surfaces. During welding, tinning precedes the weld puddle.
Aufhauser Braze welding products
Produce groove, fillet, plug or slot welds in metal ranging from thin sheet to heavy castings
Allow for build up, as in gas welding
Offer a low temperature substitute for gas welding
Are a low-cost substitute for brazing with silver alloys
Braze welding resembles brazing in two respects: (a) nonferrous filler metals are used, and (b) bonding is achieved without melting the base metal. On the other hand, braze welding resembles welding because it can be used for filling grooves and for building up fillets as may be required.
Major advantages
Joints are made at lower temperature than in gas or arc welding
Minimizing thermal stress and distortion
Less susceptibility to cracking
Soft and ductile weld deposits
Easy machinability
Low residual stress
High strength fillets
Simple, mobile equipment is simple for on-site repair
Drawbacks of the braze welding process include :(a) weld and base-metal colors do not match; (b) weld strength, while usually adequate, is limited by the strength of the copper alloy used, and thus to service below 500 F; (c) joints are subject to galvanic corrosion and to differential chemical attack. (Many of these disadvantages are overcome in the silver brazing of these alloys).
Uses
in production joining applications
for repairing broken or defective steel and cast iron parts
for repairing cast iron castings in the foundry (with color mismatch)
in machine shops, for correcting machining errors or modifying in-process parts
in maintenance departments and tool rooms for repairing tools and equipment
in mobile repair units (grain-harvesting crews, ship repairs)
Flame Adjustment
For carbon steels, the oxyacetylene flame for braze welding is adjusted to the neutral condition. For cast irons, the flame is adjusted to a slightly oxidizing condition by increasing oxygen or decreasing acetylene flow, which reduces the telltale acetylene "feather". When the feather disappears and the inner cone becomes slightly necked, the flame is oxidizing. This type of flame removes the graphite from surfaces of cast iron.
Air is not used as the combustion agent in braze welding, because it results in slow heating.
Aufhauser Braze Welding Filler Metals
All-weld-metal tensile strengths of these alloys range from approximately 50,000 to 70,000 psi. Melting temperatures of these alloys range from about 1600 to 1800 F.
Aufhauser Low Fuming Bronze (RCuZn-C) rods are also low-fuming bronze rods, and are of the same composition as Aufhauser LFB_B (RCuZn-B) except they do not contain nickel. RCuZn-C rods provide as-welded mechanical properties that are higher than those obtained with RBCuZn-A, and are widely used as general-purpose rods for braze welding of both steel and cast iron.
Aufhauser Nickel Silver (RBCuZn-D) rods have lower copper and higher nickel contents than those of the three other filler metals. Because of this difference in composition, the deposit from an RBCuZn-D rod is whiter and is thus used for braze welding when closer color match is important. RBCuZn-D provides the highest as-welded strength of the four braze welding filler-metal alloys that are discussed here.
Aufhauser Naval Brass (RBCuZn-A): contains up to 1% tin, which improves strength and corrosion resistance. These filler-metal rods are especially suited for use with oxyacetylene, and are considered as general-purpose rods for braze welding of steel and the various grades of graphitic cast iron.
Joint Properties.
Joints braze welded with one of the RCuZn filler metals have tensile strength at room temperature that usually ranges from 40,000 to 60,000 psi, depending on the filler metal used. The strength of the joint drops off very quickly at temperatures above 500 F. Color match with the base metal is not usually obtained, but where color is important the RBCuZn-D (nickel silver) rod is used. The bimetallic joint is subject to galvanic corrosion and is less resistant to alkaline solutions than the ferrous base metal.
Aufhauser Nickel Silver (RBCuZn-D) is often the superior choice because:
The filler metal is less susceptible to attack during cleaning; voids and roughness are reduced; cleaning time is less critical, giving the operator more latitude in removing smut; the filler metal is harder and less likely to feather during grinding; the roughness resulting from buildup of nickel is greatly reduced; color match is improved, making the joint less noticeable. In addition, the joint strength is higher.
Fluxes
Fluxes for braze welding are not the same as those used for capillary brazing. Because the temperatures used in braze welding (often higher than 1800 F) are higher than those used in most capillary brazing, and because the time of exposure to elevated temperature is longer in braze welding, the flux used must have a higher melting point and be able to withstand sustained exposure at the higher temperatures.
Three types of flux are in general use:
1) A basic type of flux, which simply facilitates braze welding by cleaning the base metals and aiding in the tinning operation.
2) A flux, available in paste form, that performs the functions of the basic flux described above and, in addition, suppresses the formation of zinc oxide fumes from the filler metal.
3) A flux, sometimes called a tinning flux, that is formulated expressly for use in braze welding of gray or ductile iron.
The first two of the above-listed fluxes are generally satisfactory for braze welding of steel and malleable iron. The second type is sometimes used with copper-zinc filler metals in capillary brazing. The third type contains iron oxide or manganese dioxide, either of which combines with the surface carbon of the gray and ductile irons; consequently, this type of flux, is preferred for braze welding these cast irons.
Application of flux is done in any of four ways: (a) dipping the heated filler-metal rod in the flux, (b) brushing flux on the joint before brazing, (c) using flux-coated filler-metal rods, or (d) fluxing through the gas flame.
The use of flux-coated filler rods or gas fluxing eliminates the fluxing operation and ensures uniform application. Gas fluxing is used chiefly on steel in production.
Joint Preparation
In base metals thicker than about 2 inches, the edges of butt joints for braze welding are prepared with a 90° or a 120° V-groove, to provide a wide bonding area. Fillet, plug and slot welds present naturally open faces. Edge preparation in base metals less than about 2 inches thick can be optional; either a square groove with a root opening comparable to the thickness may be used, or a V-groove may be cut. The V-groove makes it possible for the braze welding operator to see whether the joint is properly filled; this is not always possible in torch brazing.
In applications involving thin joints with parallel-side joint surfaces and relatively close clearances, it is sometimes difficult to determine whether the joining process qualifies as brazing or braze welding, because there is some capillary action.
Cleaning Before Braze Welding
For satisfactory results in braze welding, joint edges must be as clean as possible before the operation begins. In order to obtain maximum bond strength, the joint surfaces must be bright and free of oil, rust or other foreign matter. Also, the metal surrounding the joint edges must be cleaned, both on bottom and on top.
The use of a salt bath is best for cleaning any of the cast irons prior to braze welding, just as it is for brazing. If a salt bath is not available, however, following procedure is reasonably satisfactory.
If the surface of cast iron has been ground, the graphitic smear can be removed by quickly heating the surface until it is dull red in color and, after cooling, going over the surface with a wire brush. If greasy or oily cast iron is ground, some of the grease or oil may penetrate the surface. If this occurs, the resulting film should be removed by painting the surface with chemically pure hydrochloric acid. After 15 minutes, the surface must be scrubbed with a wire brush and cold clean water.
Pre-heating and Post-heating
Although it is not always necessary, iron castings may be preheated before being braze welded, to ensure success of the operation. The preheating may be local or general, depending on the size of the casting. Large castings require extensive preheating. A black preheat, or a low red heat visible in darkness (obtained at approximately advantageous in some applications to preheat to as high as 1650 F, but temperatures above 1000 F may have an adverse effect on the wetting action of the filler metal, because of oxidation of the surfaces before braze welding.
No post-heating is necessary after braze welding of cast iron. However, cooling of the braze welded assemblies is preferably retarded by wrapping them with asbestos or by the use of similarly effective methods.
Braze Welding of Steel
Braze welding of steel is faster than gas welding, because braze welding requires less heat. Overheating of the base metal must be avoided, to prevent the filler metal from failing to wet the joint surfaces. Low-carbon steels are heated no higher than 1350 F before the filler metal is deposited. Although the filler-metal alloys used in braze welding melt at temperatures between 1600 and 1800 F, the only rise in the temperature of the base metal is that incidental to deposition.
The low peak temperatures in braze welding reduce the probability of distortion and avoid the problem of melt-through in thin metals.
Production braze welding of metal furniture and similar products that are to be plated requires joints that are free of surface oxidation, overheated flux and smut film. In addition to pickling, it may be necessary to grind, brush, buff and polish the joint for satisfactory plating. These problems may be largely avoided by using Aufhauser Speed Flux (gas flux).
Braze Welding of Iron Castings
Unlike other welding processes, braze welding with Aufhauser copper alloy filler metals is effective on any type of cast iron. Peak temperatures of the base metal in braze welding can be low enough to avoid, or at least to cause very little, transformation during the heating cycle. Brittle transformation products in the heat-affected zone of the joint, therefore, can be largely prevented. The weld-metal strength is in the strength range of the gray irons, the ferritic malleable irons and the lower-strength ferritic ductile irons. Tension tests of braze welded joints have sometimes shown a disturbingly frequent occurrence of parting at the bond line, but this is generally attributed to improper cleaning, fluxing or tinning, and it emphasizes the need for care and skill.
The low temperature requirements of braze welding make the process particularly suitable for joining malleable iron. Cast iron base metal rarely needs to be preheated to more than 1000 F, and lower temperatures are often used. In fact, the base metal itself determines the correct preheating temperature; if too hot or too cold, the filler metal will not wet (or "tin") the joint. The heat added during braze welding is normally of short duration.
The principal drawbacks of braze welding as applied to cast iron are: a)the color of the copper alloy filler metal does not match that of the iron; b)the corrosion resistance of the weld metal differs from that of the base metal, being particularly low when the weld metal is exposed to strong alkalis; c) galvanic corrosion, due to dissimilar metals, may be a problem; and (d) the strength of a braze weld falls off rapidly with increasing temperature, so that the service temperature of the casting is limited to 500 F max.
Braze welding is used to join cast iron to itself or to other metals for production assemblies, and for repairing worn or broken castings.
Chief advantages over gas welding with cast iron rods:
Lower cost
Low thermal stresses minimize the possibility of cracking in the cast iron, which is a brittle material
Low peak temperatures avoid the formation of brittle transformation products encountered with other joining processes.
The copper alloy weld metal is sufficiently ductile to absorb most shrink age stresses without cracking or parting at the bond.
M. Steel Cycles Tandem Bicycle to Tandem Trike Convertible
A Newton tandem tricycle conversion, but that's not all....
This was a job undertaken for one of our customers who wanted a little more stability. As the tandem already had S&S couplings it seemed logical to utilize them to fasten the tricycle conversion on. This was certainly one of the more 'interesting' jobs we have tackled.
The tricycle front end is held on with S&S couplings. This allows the normal front end to be replaced should the customer require it.
.
.
