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Chopping up a Bicycle FrameRecycle and reuse are the name of this game, especially when you are creating a rolling work of art from the ground up. Practically every single part of a standard bicycle frame can be recycled, and many of the parts are key components in any frame such as the head tube and bottom bracket. Every scrap frame you can find will have some good reusable parts, even one that has been run over by a bulldozer, so never turn down any free bicycle junk! Let's cut up an old frame into its individual tubing components and see what we get.
Figure 1 - The sacrificial lamb Every steel bicycle frame can be butchered up into reusable tubing for your projects. Aluminum and carbon fibre frames are not very useful to the garage hacker, so don't bother trying to recycle them for your projects. Carbon fibre is obvious by visual inspection, but aluminum can be tricky to distinguish from steel when it is painted. A quick test is to place a magnet on the frame. A magnet will not stick to aluminum, so that will tell you right away if the tubing will be of any use. Also, aluminum will not throw sparks when using a grinder, but at that point, it may be too late! The typical upright bicycle frame shown in Figure 1 was salvaged from the local dump and is awaiting a new life as some radical new recumbent bike or trike. 
Figure 2 -Lugged frames should be avoided In addition to an aluminum or carbon fibre frame, there is one other type that should be avoided if you have enough scrap to choose from - a lugged frame. A lugged frame will often show up in the form of an old "granny bike" or 1970s single speed cruiser. Although these frames are steel and can be welded, the bottom bracket and head tube will not be reusable due to the lugged construction of the frame. Lugged frames have inserts for the frame tubing as can be seen in Figure 2 of the bottom bracket. If you cut the bottom bracket or head tube from a lugged frame, there will be massive holes in the parts, making them very difficult to reuse. Any frame that has the tubing welded directly to the bottom bracket and head tube will be fine, but try to avoid lugged frames if you can. 
Figure 3 - Types of grinder discs Although you can do most of your frame butchering using only a hacksaw and a hand file, an angle grinder will certainly make the job much easier. The three different grinder discs shown in Figure 3 from left to right are: flap disc (sanding disc), zip disc (cut-off disc) and a standard grinding disc. The zip disc will rip though a bicycle tube like a hot knife through butter, and a single disc will probably be able to chop up 10 or more frames. The larger grinder disc is good for removing the leftover tubing on the bottom bracket and head tube as well as cleaning or fish-mouthing up the ends of tubes for welding. The flap disc is like a finishing disc, able to clean up paint and small amounts of leftover weld metal, bringing the surface to a like-new condition. If you plan to dig deep into this hobby, it's a good idea to have a good collection of each of the three disc types in your toolkit. 
Figure 4 - Making the first cut The first cut you make into a triangular frame will be the one that will cause you the most problems. Because of the stresses put on the frame during the welding process, it will tend to collapse onto itself as the first cut is made through the tube. When using a zip disc, you have to be aware of this and make sure you have a really good grip on the grinder, or stop short of the end and simply make the last bit of the cut with a hacksaw. When cutting frames, I either have them in a vice as shown in Figure 4, or place them on the floor and stand on the frame to keep it from moving. It does not matter where you start cutting, and it really depends on how you plan to use the frame. Just remember that any triangular shape is going to want to grab your zip disc at the end of the cut, so be prepared! 
Figure 5 - Avoiding a grinder disc snag Figure 5 shows how the joint can collapse on itself after the first cut has been made. The top of the joint has a gap made by the zip disc, but the bottom of the joint has closed up, causing the grinder disc to jam. Usually, this is not a problem as long as you are holding on, but I usually complete the first cut with a hacksaw just in case. A jammed disc could fracture, especially the very thin zip discs. 
Figure 6 - The front triangle removed Figure 6 shows the front triangle cut from the frame. The top tube and down tube are now held in place by the head tube, and since the triangular structure has been opened, the head tube joint can be easily cut without any grinder disc jamming issues. 
Figure 7 - Cuts are very close to the tubing joint When cutting up a frame, try to get the cut as close to the joint as possible without causing damage to any of the neighboring tubing. If your grinder skills are a bit out of practice, then a hacksaw may be a better option if you are trying to cut as much tubing as possible without waste. The cuts shown in Figure 7 were done with a grinder, and are only 1/8 inch away from the other tubing, so very little tubing was lost. Cutting close to the joint also saves you time later, especially when trying to salvage a head tube or bottom bracket for use in another project. 
Figure 8 - Removal of the head tube The head tube is removed by cutting along the joint as close to the surface as possible without damaging the tubing as shown in Figure 8. On some bicycle frames that use larger diameter tubing, the top tube and down tube may be joined together, as shown in the cross section after cutting. All cuts in this section were made using a zip disc and a hand held angle grinder. 
Figure 9 - Separating the top tube and down tube The oversized down tube was removed from the top tube by cutting along its seam as shown in Figure 9. The cut could have also been made ahead of the weld, but I usually try to salvage the longest length possible, as it becomes highly annoying to grab a tube for a project only to find out it may be half an inch too short! The leftover weld metal can always be ground away later of necessary. 
Figure 10 - The seat tube and bottom bracket The seat tube, bottom bracket, chain stays, and seat stays will form the rear triangle. Actually, there are two triangles if you consider all four stays, so remember to take care when cutting the first joint that may release the tension of the structure onto your grinder disc. Figure 10 shows the stays separated from the seat tube after cutting close to each joint. If you have a difficult time convincing your grinder into the top corners, a hacksaw can always be used to complete the first cuts. 
Figure 11 - Removal of the bottom bracket The bottom bracket is one of those magical parts that will be included in every human powered vehicle you will build, no matter how unorthodox it may be. Bottom brackets and head tubes are probably the most used parts of the frame for my projects as I often use new tubing for the frame. Depending on your frame design, you may want to leave the bottom bracket attached to the seat tube, as many designs require the seat tube to allow a place for the front derailleur to mount. I always cut then reweld, but if you want to save some extra effort, consider leaving the seat tube and bottom bracket together. 
Figure 12 - The stays and rear droputs The rear dropouts and stays are more parts of a frame you may want to leave together, depending on the type of project you may want to build. A complete rear triangle can be used at the back of a tadpole trike or lowracer, so having a few that are still in one piece may be useful. I usually keep a few entire bikes together then cut the frames completely up. Having easy access to the metal scrap pile at the city dump means that I will never suffer a shortage of bicycle frames and scrap. 
Figure 13 - Separation of the chain stays Going even further into the rear triangle, there will often be a small tube of flat steel plate holding the chain stays together as shown in Figure 13. A quick run across the joint with the grinder disc and the plate can easily be broken away from the tubing. This plate has no real function on a bicycle that does not include a rear fender or kickstand, so you can omit it in your projects. 
Figure 14 - Separation of the seat stays The seat stays can also be separated by cutting the small round tube that joins them together as shown in Figure 14. This small tube offers a bit of extra support to the rear of a frame and offers a place to mount both a side pull style rear brake and a rear fender if necessary. 
Figure 15 - Removing the cantilever brake studs Cantilever brakes mount to the seat stays on these small studs, which are shown cut from the stays in Figure 15. These studs are very easy to transplant if you cut them right along the joint so that they still conform to the small round tubing. On some projects, it may be necessary to move the studs to make proper contact with the rim after modifying the rear of a frame. 
Figure 16 - All of the frame tubing cut Figure 16 shows a complete frame after butchering all of the tubes with a zip disc. This is how 90% of the frames that enter my garage end up, as they are very easy to store and organize this way. A giant pile of 40 scrap bicycle frames is a nightmare to sort through, so the frame chopping system makes the most sense when storing indoors. 
Figure 17 - Head tube and bottom bracket To recycle a head tube and bottom bracket, the leftover weld metal and paint must be removed so you can weld your new tubing. This job requires the other two discs shown back in Figure 3, the heavy grinder disc and the flap disc (sanding disc). You could actually just get away with the heavy grinder disc, but the surface will not be smooth like new metal, showing marks and lines even after you paint. A single flap disc will last for a long time, so they are certainly worth the investment, especially when it comes to taking off paint on metal that needs to be welded. 
Figure 18 - Cleaning the leftover frame tubing Start by securing the tube in your vice with one of the joints facing up as shown in Figure 18. If you are a grinder Jedi, you may just want to hold the part with your work gloves, but be mindful of that disc spinning at 10,000 rpm! 
Figure 19 - After grinding with the large disc The heavy grinder disc will easily take off most of the weld metal as shown in Figure 19, but avoid digging too deep into the tubing surface. Grind until there is just a small lump over the joint area and then switch to the flap disc to clean up the rest of the tubing. If the weld area has a gold color, this will be brazing and needs to be cleaned off before you weld the new tubing to the recycled parts. 
Figure 20 - Head tube and bottom bracket ground clean The bottom bracket and head tube are shown like new after a few minutes of working on them with the flap disc. Having the paint gone and surface smooth makes welding much easier and now primer and paint will stick to the surface without leaving any lines or scratches. Chop up a few old bicycle frames and you will have all of the building blocks you need to turn your drawings into real human powered works of art. Get the word out to friends and family that you won't turn down any metal scraps or bicycle parts, no matter how damaged they may be. A true garage hacker can turn everyday scrap into something unique! Brad (RadBrad) and Kathy (KoolKat) McGowan. 
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