Build-It: Bicycle Hacksaw
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This document provides instructions for building a bicycle hacksaw. The goals are for participants to learn basic tool use and welding skills. The project involves using a hacksaw, drill, files and other hand tools to cut and shape bicycle parts into a functional hacksaw frame. Key steps include cutting a bicycle handlebar to form the hacksaw body, attaching tensioning systems made from bicycle caliper arms, and drilling/welding everything together. With about 1.5 hours of work, participants will construct a working hacksaw they can take home while gaining practical workshop experience.
Build-It: Bicycle Hacksaw
- 1. IDIN Build-it: Bicycle Hacksaw GOALS: o Participants will have used a hacksaw, a drill and several hand tools, including a file, and hammer, and a punch. Participants will also learn some basic welding. o Participants will know how to properly use and tension a hacksaw o Participants have made a working hacksaw TIME: 1.5 hours PREPARATION: Collect materials and tools Make sure to have enough materials and tools for your demonstration Review and/or print Build-It instructions Make a hacksaw yourself to discover what participants might find difficult Organize the tools into sets to be distributed during the introduction ROOM SET-UP: This should be done in a workshop that is equipped with table space, vices, and welding equipment. It would be useful to also have an open space where the instructor can demonstrate steps to participants.
- 2. TOOLS MATERIALS Item Amount Cost Hacksaw Bicycle handlebar 1 $5 Vice Bicycle caliper 1 $3 Marker pen A large hex nut 1 minimal Hand files round and flat) Threaded rod and its hex nut (between 2mm and 6mm wide) 150 mm long $1 2 pairs of pliers Hacksaw blade 1 $1 Spanners for brake hardware Total Cost $10 Hammer and anvil Punch Welding machine Drill and bits
- 3. 1. What is a Build-It? (5 min) A Build-It is a lesson where people make a small technology and learn some workshop skills. Everyone will build together, step by step. As you build the technology, you will learn good techniques for handling metal and wood. Each member will have an opportunity to learn these hands-on skills by using some tools and materials. At the end of the Build-It, you will have had some practice using tools and also have a technology for you to take home. 2. What is a bicycle hacksaw? (10 min) Hacksaws are an important tool in any workshop. Today, you are not only going to use a hacksaw, but you will build one. This project is building a hacksaw frame out of parts from a bicycle handlebar and a bicycle caliper. It is made of two welded pieces from the metal handlebars, two sections from a bicycle caliper, a threaded rod, a hacksaw blade, and some nuts and bolts. Review how the technology works by explaining how to use it and what the major parts are. 3. Setting up the Build-It (5 min) ENCOURAGE PARTICIPANTS TO ENGAGE FULLY • Ask, “Why?” “Where?” “What?” “How?” at any time during the session • Engage everyone in the building activities and be sure that each person in the group can both observe and participate in learning and doing all of the different techniques (IF WORKING IN PAIRS/TEAMS OR STATIONS) DIVIDE INTO PAIRS AND/OR INTRODUCE THE STATIONS If working in teams, single-gender pairings often work best for allowing all members of the group to participate evenly. Explain which tools need to be shared by the larger group, and where they will be located.
- 4. 2014-04-7 4 4. Preparing the hacksaw body (10 min) Start with a bicycle handlebar. The hacksaw must be bent in only one plane, so the handlebar must be cut so that it can be welded as a flat piece. Tools Materials Steps 1. Mark the handlebar before the curve of the handle (as shown in the photo). The long piece should only curve downwards, in one direction. 2. Put the handlebar in a vice and cut the handlebar in the desired places using a hacksaw. Be careful not to tighten the vise too tight or you risk deforming the tube. You now have three metal tubes. The long metal tube will be the body of the hacksaw and one of the shorter tubes will be used as the hacksaw handle. The second shorter tube is not required to build the hacksaw. However, it is useful to keep hold of it so that if the first tube is damaged, you still have a spare to work with. It also can be used to extend the body of the hacksaw if that variant of the hacksaw is built. 3. Shorten the short tube to create the handle. The cut must be made so that the tube is the correct length to allow the handle to lie perpendicular to the alignment of the hacksaw blade (see the picture in Step 5 to see what you are making).
- 5. 2014-04-7 5 4. Using a hand file, smooth the sharp edges of the cut tubes and shape the end you just cut so that it fits with minimal gaps. 5. You can now lay out the pieces to see the hacksaw taking shape. The spaces above the blade is where sections of the caliper arm will go to tension it. 5. Preparing the blade tensioner (20 min) Tools Materials Steps Disassemble the caliper 1. Remove the nuts and bolts from the caliper using a spanner. 2. Pull off the spring from the caliper using pliers. You should now be able to take the caliper apart. Preparing the front end tensioner 3. Take the Y-shaped caliper arm and align it with the hacksaw handle. Once it’s in place, draw a line about ½ to 1 inch above the tip of the hacksaw frame so that you know where to cut the caliper. The caliper arm should be aligned so that it matches the curve of the main bar. The brake caliper and its components The two caliper arms and the spring
- 6. 2014-04-7 6 4. Put the caliper arm in a vice and use a hacksaw to cut it. It may be easier to cut if it is positioned vertically. 5. Flatten the end of the frame bar so that the stirrup section can fit closely into the bar, and be easily welded later. You can flatten the end of the bar using either a hammer or by squeezing the bar gently using a vise. 6. Cut down the edges of the caliper arm so that it can fit into the flattened tube. Hacksaw the pointed sections off, and then file until it fits closely in the bar. Continuously check the fit between each hacksawing and filing. These two parts will be welded later. The caliper arm section in the flattened bar (after hacksawing and filing the edges of the arm section)
- 7. 2014-04-7 7 There are a few variations of how to make a rear tensioner, each using different parts of the bike. Caliper version Brake handle version (This Build-It) (another version) Preparing the back end tensioner 7. Take the U-shaped caliper arm to make the holder for the other end of the blade. The section of the arm with the two holes will be used to create a pivoting arm that can hold the blade in place and be used to keep the blade under tension. 8. First, flatten the end of the arm with a hammer and an anvil. 9. Next, saw off the end of the arm which is not required. Tensioning system, as shown in this Build-It using a caliper arm Tensioning system, not shown in this Build- It using a brake handle. This tensioning system, discovered later, seems to be a more robust design. The threaded rod screws onto this nut The threaded rod does NOT screw into this large nut. The rod pushes against this nut welded on the caliper, which tensions the blade This is pinned so the arm can pivot The threaded rod screws onto this nut The threaded rod pushes against the handle, which tensions the blade. This is pinned so the arm can pivot The parts in position so far
- 8. 2014-04-7 8 10. Finally, use a file to smooth the edges of the arm section so that it will be able to move around smoothly inside the bar. This will be done most easily if the arm is held in a vise. 11. Like previously, you need to flatten the other end of the main arm so that the caliper arm section can fit inside the arm and pivot freely. Once the arm is flattened, check that the caliper section fits, and file it more if required. 6. Assembling the frame and tensioning system (20 min) Tools Materials Attaching the front end tensioner 1. Use a grinder or a file to grind the bar’s chrome coating away in the areas where you want to weld You want to remove the chrome as it gives off unpleasant gases if heated. 2. Weld the front caliper arm onto the main bar Tack in one place first, then check to ensure it is in one plane 3. Weld the handle onto the main bar. Again, tack it first, and keep checking the alignment while you weld
- 9. 2014-04-7 9 Fastening the blade 4. To fasten the blade, cut the two rings from the spring using a hacksaw. Put the put the spring in a vice, and spread the spring open slightly to give space to cut (however be careful as the metal is a fairly high strength and would be easy to break or deform). Attaching the back end tensioner 5. Drill into the end of the main bar for a bolt to attach the caliper arm and allow it to pivot. Work out where the hole should be and use a punch to create an indentation in the correct position. This indentation helps to position the drill in the correct position. 6. Take the long screw from the section of caliper parts and cut it in half to create the pivot screw. First, screw two bolts onto its middle. Separate them slightly to expose the middle of the bolt. Cut between the nuts with a hacksaw to cut the bolt in half. Having the nuts help guide the hacksaw will prevent the bolt threads from getting damaged. Using the punch (note the position of the hole in the main bar)
- 10. 2014-04-7 10 7. Use a file to smooth the top of the cut screw 7. Making the tensioning arm (20 min) Tools Materials Drill two holes in the hacksaw body to allow the tensioning rod to pass through. This needs to be done very carefully. 1. Line up the filed rod with the hacksaw body and mark the position of the holes 2. Mark the top hole with a punch, and then drill it to ¼ inch. 3. Tilt the drill to make the hole oval, so that the rod can slide through the hole at the necessary angle. 4. Remove the blade and mark the position of bottom hole with the punch.
- 11. 2014-04-7 11 5. Like before, drill the hole with the ¼ inch bit, and then tilt drill to make it oval. 6. Enlarge the top hole to ½ inch by repeating the process with a ½ inch bit. 7. Put the small nut onto the threaded rod and put the rod through the holes. It should be placed where it will finally be. 8. Tack the small nut onto the main frame of the hacksaw, by the bottom hole. Once it is tacked, remove the threaded rod and continue welding. 9. Put the threaded rod back on and weld the large nut onto the caliper arm so that the threaded rod rests inside. If you would like, weld a washer onto the threaded rod to make it easier to tension the hacksaw. Build-Its are published by IDIN. The International Development Innovation Network (IDIN) is a consortium funded through USAID’s Higher Education Solutions Network (HESN) that supports leading universities to catalyze the development and application of innovative science, technology, and engineering approaches and tools to solve some of the world’s most challenging development problems. The bicycle hacksaw featured here was designed created by Bernard Kiwia, an appropriate technology teacher in Tanzania. The document was created by Benji Moncivaiz in collaboration with IDIN representatives at UC-Davis and Olin College. The two holes – note how the top hole is larger than the bottom hole.