Home #Makerspace: #DIY Rebuild a Kids BMX Bike with #Maker Tools
Every few years, I find an excuse to engage in one of my favorite old-school projects, rebuilding and repainting a kids bicycle.
Let’s paint some flames.
I mean, dragons. We will paint dragons.
This project is approachable for middle-school and high-schoolers. High-interest elementary school kids can definitely accomplish parts of this project with help from an involved adult. This project does involve dangerous fumes, so great ventilation and respiratory masks are a must. Be prepared to give over your work space for a three days to a week and a half to this project.
This project teaches basic competencies in graphics software, cutter plotter use, mechanic’s tool usage – wrenches, ratchets, etc., and paint prep and execution. These skills are directly transferable to manufacturing, automotive and graphic arts fields (for my fellow CTE/Shop teachers out there). Bike mechanics earn about $12 per hour nationally, offering a student an entry point into the skilled trades.
In school, I began with donations from student families. I then taught my students how to use tools and the basics of gears, force, torque and work. We fix’m up and get the bikes running. At the end of the experiment, we would give the bikes away to kids who need them. Workshop Houston began with a similar model and Cycle of Houston has given away 100,000 bikes in just over ten years of existence. Bikes can and do change a child’s world by offering opportunities to develop balance, judgement and freedom in the wider community.
Update: I’ve since found my write up from 2011. This is my second or third version of this project.
How To Rebuild A Kids Bike with #Maker Tools
This is a project can involve a ton of materials and tools, but in reality, it has three basic steps: the breakdown, painting the parts, then rebuilding the bike. You can simplify this project greatly by not stripping the paint, not using stencils and spray-painting the frame, forks, handlebars and cranks assembled on the frame. Feel free to adjust the steps as necessary to fit your abilities, tools and space needs.
- Donor Bicycle. Check craigslist, yard sales, pawn and thrift shops for great steals. Make sure the wheels spin straight and free. Watch out for cracks and signs of major rust in the frame (the main body of the bicycle). Buy a machine that looks beat-up and used, but not majorly neglected.
- Enamel Spray Paint. I used Rustoleum brand because it’s widely available. Automotive paint suppliers, hobby stores and art supply houses all have different brands at different performance and price levels. Shop around to find your sweet spot. I used 2 cans of primer, 1 can per color used and 1 can of clear coat. So for a 2-color paint job, I bought 2 cans of primer, 1 cans of color and 1 can of clear coat.
- Replacement Parts. Common parts which need replacement after years of abuse: seats, brakes, brake levers, cables and grips. I ordered replacements from Amazon, averaging about $40 per bike.
- White Vinegar & Small Tub.
- WD-40 or Machine Oil
- Steel Wool
- Paint Stripper. The eco-version works in perfect conditions. For anytime else, use this stuff with safety precautions.
- Small Paint Brush.
- Nail Polish Remover. A thinned version of acetone for cleaning.
- High-Grit (320+) Sandpaper
- Heavy Grease/Lube. Axle grease, Parker’s Polylube and white lithium grease work great for bearings.
- Chain lube.
- Vinyl for stickers or stencils.
- Transfer paper.
- Plastic Drop Cloth for spray booth
- Hex wrenches
- Small adjustable wrench
- Chain breaker tool.
- Large tongue & groove wrench
- Set of thin cone wrenches, such as the Park wrenches. While not a necessity, definitely a great luxury which allow you to repack the wheel bearings.
- Bike stand, again a luxury item, but by golly, is it nice to have.
- Nitrile gloves.
- Heavy rubber & cloth gloves if you decide to strip the to the frame.
- Rotary tool with wire brush
- Silhouette Cameo or other vinyl plotter cutter and accessories.
Breakdown the Bike
Strip the donor bike down to it’s various sub-assemblies. Your sub-assemblies are:
I’ve linked to a number of resources to help your breakdown. I store small loose parts, such as nuts, bolts, pegs, etc. in individual bags labeled with the corresponding sub-assembly.
Clean, Reuse or Replace
- Greasy parts, such as the crankcase or wheel bearings & axles, are scrubbed with acetone. Low-strength acetone formulation in nail polish remover works perfectly. Make sure you work in a well-ventilated area, such as outdoors, or wear a respirator for this step.
- Clean any dirty and rust parts. I soak rusty parts in vinegar, scrub clean with the steel wool, dry with paper towels, then coat with WD-40 or a dry lube for protection.
- Determine if any bike parts need replacing, then order/buy parts. I needed a new gyro & front & rear brake lines, new grips, brake levers and chain for this particular rebuild.
1. Remove the decals. I used a heat gun and acetone to remove the decal and goo.
Now choose your path!
Low Dust, Low VOC, Low Cost, Low Effectiveness:
2. Scuff the frame with 320+ sandpaper. No need to go through the paint, the goal is to create a surface with a little tooth. Clean with a towel dipped in acetone. Skip to the painting stage!
This technique relies on a clean, unchipped original paint coat. If your donor bike shows some surface imperfections, you might try the other technique.
Higher Cost, High VOC, No Dust, High Effectiveness:
2. Bring on the paint stripper. Both the eco and regular version work in warm conditions. I repainted in temperatures below 65 degrees, so I went with liquid death.
3. Wearing heavy-duty rubber gloves and a respirator, spread the paint stripper on the bike frame with a small paintbrush. Wait for115 to 30 minutes, then scrape the stuff off with steel wool. Repeat applications as necessary. Let the brush and wool dry out overnight on the grass or bare ground. Don’t throw away immediately or allow to sit on
4. Clean off remaining paint with a rotary tool with wire brush attachment.
Tips for Successful Spray-Painting:
Spray-paint is sensitive to three elemental conditions: moisture, temperature, and wind. If moisture is present in the air or on the frame, the paint will bubble or slough off. If the frame is too hot, the paint will bubble. Too cold, the paint won’t stick. Finally, too much wind and the paint results become unpredictable and uneven. Spray painting is best done on a dry, clear, still day at a tempature between 65 and 85 degrees Farenheit. A great project for mid-spring and early summer, or late fall.
Since I refurbished this bike in the winter, I used drop cloths to create a semi-indoor spray booth. I hung the drop cloths from the ceiling to protect my tools and bench. I sprayed, then opened the garage to let out the fumes. A respirator is a must for this set up.
Using some scraps of wood & 3/8 inch dowels, I created a trio of paint stands. This helped hold up and steady the frame, fork and handlebars.
1. Use blue tape to mask off interior spaces in the frame, such as the crankcase and stem, especially any space that will touch a bearing when reconstructed.
2. Clean the frame and parts with acetone. Wear gloves from now on when handling bare metal, as the oils from your hand will impair paint adhesion and promote rust.
3. Put the frame on the stands, or carefully balance on your work surface. Do the same for any other parts you will paint.
4. Shake the primer can until you hear the rattle sound. The rattle sound indicates the paint and propellants have mixed. Wearing a respirator, spray the primer coat in long, even strokes. Keep the nozzle 12 to 16 inches from the frame. The goal is to drop a light, even coat which doesn’t run. Let the first coat dry for 12 to 24 hours.
5. Sand the primer coat lightly with the 320+ grit sandpaper.
6. Using a respirator, spray a second coat. Let this coat dry.
7. Reposition the frame and parts to paint the entirety of the project.
Pro-Tip: Don’t rush this stage. It takes oil-based enamel paints roughly 24 hour to harden for sanding. The smoother your primer coats, the better looking the final result. Try not touch your frame with metal tools, or touch or poke the paint right now. Oil-based enamel paints take weeks (yes, weeks) to harden so they don’t show cracks and scrapes. Professionals and factories bake the enamel in large ovens – this project compensates with sunlight and time. Also, a great primer coat is crucial for spray-painting plastics. In the image below, you see the results of a bad primer coat.
If you want to use a stencil to create a design, read this section. If you don’t, skip to the Base Coat.
- In the Silhouette Studio, open the image of your stencil.
- Use the Trace tool to create a cut outline of the image. Delete your image, and prepare your stencil to be cut.
- Remember to mirror any stencils which appear on opposite sides of the frame.
- Cut your image from vinyl using the appropriate settings.
- Remove the waste vinyl.
- Use transfer paper to pick up your stencil.
Stencil Under Coat:
- Using the final color for your stencil, spray two light coats where you will place your stencil.
Apply the Stencil:
- Carefully place your vinyl stencil on your bike.
- Smooth out any air pockets.
- Slowly peel away the transfer paper.
Next, we spray the base coat.
- Shake the primer can until you hear the rattle sound. The rattle sound indicates the paint and propellants have mixed. Wearing a respirator, spray the primer coat in long, even strokes. Keep the nozzle 12 to 16 inches from the frame. The goal is to drop a light, even coat which doesn’t run. Let the first coat dry for 6 to 8 hours. I averaged 2 coats a day.
- Sand the primer coat lightly with the 320+ grit sandpaper.
- Using a respirator, spray a second coat. Let this coat dry.
- Reposition the frame and parts to paint the entirety of the project.
Remove the Stencil:
- Once the base coat has been applied, remove the stencil, revealing the image underneath.
Next, spray two light clear coats. The clear coat acts as a final protective jacket for the metal parts. You do not need to sand in between coats.
Clear coats come in three different sheens. Matte finishes don’t reflect light well so the surface looks dull. Satin has some shine to it, while glossy sheens really reflect light well. Make sure your clear coat reflects the sheen you want, as glossy colors turn matte under a matte coat or vice versa.
Now, rebuild the mechanicals of the bicycle and install and fit any new parts. Cover bolts with cloth to minimize scraps during installation.
Use the heavy grease to repack any bearings.
Use a dry lube to lubricate the chain.
Thank you for your continued support.
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