Miniature Bike

I saw some movies on Youtube of other people making a bike.

For example this chopper from nuts and bolts by "jagz TE". What I like about this bike is that it is easy to make and the result looks good. But I think it is quite fragile and could easily get damaged and it is not so clear what the sizes are.

I was really impressed by the bike made by "Hoo's mini world". He (or she) made a very realistic looking motorbike with a 3D pen, but that takes so much time and patience to build, that I think only a few people would be patient enough to make that.

I did not see any movie with drawings or measurements, so what I want to improve is to get measurements of every step of what I did, so that it is relatively easy for you to make my bike. Also I wanted my bike to be strong, to look good, and to be made only of materials that are widely available and that the build could be done in just a few days, because that gives us time for many other fun projects.

It took me three days to make this bike, but that was including taking notes and figuring out how to make the bike, so probably you can make the bike in just two days if you use my drawings. I have added the drawings to this Instructable.

I made the bike only from parts that are usually very easy to get. Most pieces I already had in my garage and the few parts I had to buy were less than 10 dollars in total. I used metal and welded most of the bike, because I wanted it to be strong and not fall apart. I you do not have welding machine or you cannot weld, you can still use the dimensions from my drawings and I think you can get quite far by using wood and glue.

If you are good with electronics, you could upgrade the bike by making an engine with pistons that are driven by a little motor and you could add some lights to the bike. I would be very interested in your result.

Materials:

(I did use a mix of carbon steel and stainless steel parts, but I did not use any steel that is galvanized, because that would give toxic fumes while welding.)

The list below indicates which materials I used. If you cannot get these sizes, you could use other sizes that come close. In this Instructable I mention sizes in the metric system. If you prefer working in inches, I converted the sizes in the list of materials here below. (1 inch is 25 mm, 1 meter is 40 inches, one centimeter is 10 mm.)

• steel rod 6 mm thick, 2 meters (1/4" , 7 feet)
• steel rod 12 mm thick, 25 cm (1/2", 10 inch)
• steel sheet 2 mm thick, 30x30 cm or similar surface area. (5/65" thick,1' x 1')
• spoons, 4 pieces (see drawings for size)
• shoehorn, 1 piece (see drawings for size)
• M8 nut (stainless steel), 5 pieces (5/16")
• M8 washer (stainless steel), 3 pieces (5/16")
• M5 nut (stainless steel), 20 pieces (3/16")
• M5x40 bolt, 2 pieces (3/16" , 9/16" long)
• TIG Welding rod 3.2 mm, 50 cm (for spokes) (1/8", 20 inches)
• MIG welding wire 1.0 mm, 50 cm (for cabling) (1/32", 20 inches)
• Copper wire 1.5 mm2 with black insulation, 15 meters (for tires, springs and handles) 15 yards
• Spray paint, primer for metal.
• Spray paint, black.
• Paint copper colour.

Tools:

• TIG welding machine
• Grinder
• Vise
• Hammer
• Screw driver
• Spanner 8 mm
• Drill with 3.5 and 5 mm drillbit
• Clamps
• Sand paper

I have made 5 drawings and I attached them both as photo and as PDF file. It is best to use the PDF file for printing. I used a A4 size piece of paper to make the drawings on a 1:1 scale. As printers can sometimes decide to scale the drawing to make it fit the size of paper you are using, I added lines on each drawing of 100 mm long (almost 4 inch) in both vertical and horizontal direction. Please check if the lines are indeed this lenght on your print, so that you can use the drawings as templates.

I just traced each part that I made with a pencil on a piece of paper. To get the most accurate result, you should remove the line while cutting, so that each part will fit within the lines. If needed you can trim your parts a little bit where needed.

There are two ways to make the rims:

If you have a piece of pipe with the desired diameter (roughly DN50 or 2"), you can just cut two rings one 20 mm wide and the other 25 mm wide and use them as rims.

As you can see on the photos I did have a piece of pipe, but I decided to make the rims from a sheet metal, so you do not have to buy a piece of pipe for just two small rings and this size of pipe is not sold in most shops for DIY materials.

So if you do not have the pipe, use a steel sheet of 2 mm thick and clamp it to your workbench. If you use thinner sheet metal, the bending is easier but the welding will be more difficult. If you use thicker sheet metal, the bending will become much more difficult.

Mark a piece of 20 mm wide (for the front wheel) and another piece of 25 mm wide (for the rear wheel). I recommend to cut a lenght of 250-300 mm. That is longer than you really need, but it makes it easier to bend the metal sheet. Use a grinder to cut the sheet metal along the line. Use some sandpaper to debur the strip you just cut and wrap it around something round which has the size you need. I used a piece of pipe, but you can also use a round piece of wood or a glass. You probably cannot bend the sheet enough to make a full circle immediately, so cut off the short straight part and continue bending. With 2 mm thick sheet metal you can bend it manually without additional tools, but you can also use a hammer to finetune it a bit. Check on the drawing if you have the right size and weld the two ends together to make a full circle. Use the vise or a hammer to correct the shape if you got an oval instead of a circle.

I used 3.2 mm TIG welding rod for the spokes and therefore I used a 3.5 mm drill bit to drill holes in the rim. If you use another size for the spokes, you should use a drill bit just a little bit wider than the size of your spokes. I decided to use 6 spokes per wheel, so I marked 6 points on the rim that are evenly divided. You can see the markings indicated on the drawing.

Cut all spokes and make them longer than required so you can hold the end that is outside of the rim, while you weld them. I used a M8 stainless steel washer as brake disk and as centre to attach the spokes to. Place the washer in the centre of the rim and push all spokes through the rim in place. Support the washer to keep it at the desired height before welding the first spoke. Just use the spoke as welding rod and leave it to freeze in the welding puddle. After the first spoke, weld the one which is directly opposite, so after welding these two you can still move the washer a bit. Check if the washer is in the centre and weld the remaining spokes. Probably your washer has tilted from the heat of welding. Correct that by hitting it with a hammer. Then weld three M5 nuts together to form an axis. Use a drill to remove the thread in the nuts, so the wheel will be able to turn. (If you would like the wheel to turn very smoothly, you could decide to use a bearing instead of the M5 nuts.)

Also add spokes to the second wheel.

I used electric wire to make the tyres. If you do not like that, you can use something else like foam or rubber to make tyres in another manner.

My rear wheel is wider than the front wheel, so I also made the tire for the rear wheel a bit wider. The photos are from the front wheel.

Cut a piece of wire of approximately 6 meters for the front tyre and approximately 9 meters for the rear tyre. Start by winding the wire aproximately 5 times next to eachother for the front tyre. For the rear tyre use a few additional windings to make it wider. The diameter of the circle you made should be larger than your rim and you should leave enough space between your first circles of your tyre and the rim for the wire to wrap it around the bundle.

Then wrap the wire about 8 times around the bundle you made and make sure these 8 turns are evenly spaced over the circle of your tire. Check if it will fit around your rim. If not, you might have to unwind the 8 turns and make your circles larger or smaller.

When you confirmed the size is OK, keep following your previous winding until you have wrapped the entire circle. This means you have to pull the end of the wire many times trough the circle. Cut of the excess lenght of the wire and keep it as you need it later for the springs and handles.

Check again if your tires fits your rims. I then placed the tires aside until I would be ready with painting the rims which I did completely at the end.

On the drawing with the wheels I also show the shape of the front fork. I started with a steel rod of 6 mm thick and bent it around a round pipe. Start with a piece that is too long and when you are happy with the shape, cut off the excess part. Make sure you get two pieces that are almost identical. I used clamps to clamp the parts to my welding table before I welded them. Make sure both sides are symmetrical before welding.

I used two pieces of 30 mm long to connect both sides. The position is indicated on the drawing.

I made the frame, front fork and the fuel tank simultaneously because they determine the shape of the bike. I describe this as three separate steps, but on the photos steps are a bit mixed.

For the frame I also started with the steel rod of 6 mm thick. I cut two pieces of 250 mm and bent them in the vise 100 mm from one end. You can see the shape on the drawing. Then I cut two pieces of 30 mm long and used them to connect the two halves of the frame. Their position is also indicated on the drawing.

Where both ends of the frame meet I welded one M8 nut (stainless steel). I used a clamp and a short piece of 6 mm rod to keep the nut in place. One nut is not sufficient because the front fork can then move also sideways. You can already add a second nut now, but then it is hard to see if the angle of the front fork is correct.

I cut a piece of 6 mm rod, placed it in the hole of the bolt and then welded the the front fork to this piece.

I cut one side out of a M8 nut and welded that to the other M8 nut on the frame. That keeps the front fork better supported so it cannot move sideways. The distance between the axis of the front wheel and the rear wheel should be 290 mm. On the photo it is 270 mm, but I later adjusted the angle of the M8 nut so the distance became 290 mm.

The front fork can still move up and down, so place it in the position you like and then weld a small dot on the front fork above and below the M8 nuts so the front fork can still rotate but not really move up and down anymore. (You can also do this a bit later, when the bike is finished further because then you can better see which position is best. I added a photo where you can see where I added these 2 dots, but on that photo the bike is already almost finished.)

I welded 4 M5 nuts to the frame to make the holes for the axis of the wheels. I drilled the thread out of these nuts because getting them properly alligned is very hard. Originally I placed these nuts on the M5 bolts and then welded them to the frame, but the welding distortion then makes it impossible to remove the bolt again, so I had to use the grinder to remove the bolt.

I used 4 spoons to make the top part of the tank because I wanted a curved surface. You could also use another piece of sheet metal and use a hammer to get a curved shape. I welded the four pieces together and cut off the part at the side where it would be too wide.

I traced the size of each spoon and the size of the 4 spoons combined on the drawing. I made the rest of the tank after making the top, but you can consider to make the bottom part of the tank first.

I first made the top, then the side and finally the bottom, so I could make a paper template to get the shape of the bottom. Trace the shape of the paper and cut the steel. You find the template on the drawing of the tank. I also traced the part that I used to make the side of the tank, so you can start with that template too. Bend the piece for the side of the tank to the shape indicated on the drawing. I used two short pieces of 12 mm rod welded to a bar to help me bend the plate. I only tag welded the bottom plate. As you can see I bend the bottom plate also a bit. I first just welded one side and used a hammer to make it fit at the other side and then welded that too.

At the top side of the tank I grinded the welds away and added one dot as fuel cap.

Add the part of the frame which will be under the fuel tank. The position is indicated on the drawing.

Then bend and cut the pieces that connect the rear axis with the top part of the frame. They are again made of the 6 mm rod and the shape is shown on the drawing. It is best first to bend and then to cut the pieces because you can use the rest of the rod as lever for bending. I used the vise to hold the pieces in place while bending them. Then place them so they are 30 mm apart at one side and touch at the other side and weld them first together and then to the frame.

I used a shoe horn as seat. Later I decided to cut part of the shoe horn off and place it upright, but by first using the shoe horn completely you can better see what the best place is to cut it.

I only used some tag welds to connect the tank and seat to the frame.

I also cut a short piece of 6 mm rod to use as side stand. You can see the size I used on the drawing. After I welded it in place I realized that when the tires are in place, the side stand will be too short. You can therefore decide to make the side stand a bit longer. But I solved it later by placing a small rubber cap on the end of the side stand. That makes it just long enough and also prevents that the steel from the side stand will scratch your furniture.

I made the head light from 2 M8 nuts and a M8 washer and welded them to the front fork.

Then I cut 2 fenders. You can see the details on the drawing. Check that you have enough space for your tire before you weld the fenders in place.

I also cut a part to fill the gap between the seat and the rear fender. That part is also present as template on the drawing.

I used a M8 nut for the rear light and added that later.

On the drawing you see the shape of the engine and the sides. I cut them and also made some skratches with the grinder. On the photo both sides look like they are different in size, but that is just caused by the angle of the photo. The parts are the same size. I bent part of the side slightly inward (with a hammer and the vise) because the frame at the back below the seat was a bit more narrow.

When I welded the engine in place I also added some extra welds so simulate other parts of the engine.

I made the exhaust pipes from two parts of 12 mm rod and from 2 parts of 6 mm rod. I first bent the 6 mm rod in the vise. I welded both parts of the exhaust together and then welded them to the frame.

I did not like the shoehorn as it was, so I cut it and turned the end upright and welded it in place, so the end of the upright part and the end of the rear fender are vertically in line.

I used a 3.2 mm TIG rod and welded it to the frame and then cut it off, so they become footrests.

Then I took a piece of 1 mm MIG wire and welded that to suggest the brake and clutch cable. The MIG wire melts really fast, so you have to feed some length to make it stick. Start with wire that is a bit too long and when one side is welded you can trim it to the right length.

I first spray painted all the parts with a primer for metal. When that was dry I sprayed everything with black paint.

After drying, I used a copper coloured paint and a brush to paint some details in a copper colour. If you like the silver of most bikes better, you can also use silver colour. I painted the head light, tail light, spokes, sides of the rims and the engine with the copper coloured paint. Around the engine I also added some paint, to suggest some other parts in the engine area.

I stripped some electric cable with a knife so only the copper remained. I wrapped that copper around the back and the handles to form springs and handles. Be careful that you do not damage the paint while doing this.

You also have to install the wheels. I used a M5 bolt and several nuts, so there is a nut to keep the bolt connected to the frame and there are two nuts to keep the wheel in the middle. Do not tighten too much so the wheel can still rotate.

Of course the key is not needed to start the bike. It is just there as reference about the size of the bike.