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Bicycle cargo trailer--200 lb capacity, $30 for parts

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Picture of Bicycle cargo trailer--200 lb capacity, $30 for parts
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This bicycle trailer is made from 1/2" EMT conduit that is bent and brazed into a frame. It uses scavenged bicycle wheels, has a plywood cargo bed, and can be modified for any use easily. The frame alone weighs 15lbs, and with a hitch, plywood, and wheels it weighs 25lbs or so. It carries 200 lbs safely, and it can haul up to 450 lbs carefully.
 
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Step 1: Obtain parts and tools

Picture of Obtain parts and tools
Tool list
1/2" conduit bender
hack saw
tape measure
marker
punch (or nail)
hammer
vice
1/8" bit and 3/8"
drill
half round file
oxy-acetylene torch or arc welder
plentiful brass brazing rod
brazing flux. goggles, and gloves
bricks for holding frame
framing square / "L" layout tool

Finding and Buying Parts
You can find a lot of the parts, particularly if you're near a metal dumpster or a building renovation that might be ripping out conduit. Metal shops often have scraps of flat stock that you might be able to take.

Wheels: Go with what you can find. Feel lucky if you have the option of mountain bike wheels over road bike wheels. The dimensions given here are for carts with 26", 27", or 700c wheels. If you use 24" wheels, you can reduce the cart depth by 1", and if you use 20" wheels reduce the dimensions by 3" (spine and ribs dimensions). 700c and 27" wheels work, but ther're less strong, particularly laterally, which is important when you're hauling a load around corners.

Find wheels at bike shops or in the dumpsters out back. I've had good luck asking bike shops for old wheels, and in college metal recycling dumpsters. Make sure you get 2 of the same diameter, with the diameters within 1/2" or so with the tires on. You can get tubes with small punctures behind bike shops.

Another wheel possibility: It's easiest to use 2 front wheels because they will have the same hub spacing. However, you can use a front wheel and a rear wheel if you make one of the wheel wells longer and increase the hub spacing for the rear wheel to 4 3/4", instead of 4". Or measure your wheels exactly. Hardware stores carry the EMT conduit and hardware.

You will save some money if you can find scrap 3/16" by 1" bar, plywood and 3/8" ID tubing. Try metal dumpsters, scrap bins at machine shops and mechanics' garages, etc.

In the store, hardware parts are generally less expensive in the bulk bins than in pre-packaged boxes. I can't find rod end ball joints anywhere accept mail order (I've used McMaster-Carr). The shaft should be 1 1/4" or more, and have threads that are 3/8"-24 or 3/8"-16. (The 24 and 16 refer to threads per inch.) Get a nut to match the threads. The hole through the ball should be 3/8" wide. You can order it from mcmaster.com. It is part 6072K64 for the oil-impregnated bronze race with a chrome plated steel ball and right hand threads. It costs $5.92 without shipping. I think shipping is $3 or $4. You might consider getting a welding respirator ($12) from McMaster-Carr at the same time.

For plywood, ask at a lumber yard if they have scrap wood. Building renovations and construction also generate waste plywood that will work fine.

Using the tools
To use a conduit bender, line up your bend mark with the arrow on the bender. Step on the foot plate, while pushing down and pulling sideways on the handle of the bender. Bend until the bubble level reads level with no force on the handle.

Working with metal in this project is easy, but takes some practice. To cut with a hacksaw, make sure the piece is clamped well and the cut is close to the clamp. Use the full length of the blade, pushing down hard enough to cut but not hard enough to bind the blade. Use steady, even strokes pushing forward. Don't press down hard on the return stroke. Hold both the back and front of the saw.

When using files, the cutting happens on the forward stroke. Pulling back with downward pressure on the file will only dull the file.

To cut with a tube cutter, align the mark with the cutting wheel and tighten the screw just enough to score the metal all the way around the tube. Tighten a little more and continue turning the tool, ensuring that the cut is in the original groove. Continue around the tube. This tool is useful for the conduit, but a hacksaw is more reliable.

To braze with an oxy-acetylene torch, it's a good idea to get a lesson from someone who knows how. Always set the regulator carefully and keep the tanks well secured so they could not fall. Use gloves, #5 shade eye protection, and work on non-combustible surfaces. Keep fire-extinguishing paraphernalia present. Work with good ventilation, especially with galvanized conduit.

To drill into metal, make a starting dent with a punch or nail, and drill a small hole at high speed with a sharp metal bit. To enlarge it, use a lower speed and watch out for the bit catching as it breaks through the material. Always drill into material secured in a vice or by clamps.

General safety: Wear gloves when things are hot, don't wear gloves with spinning tools. Wear safety glasses when there are chips flying (drilling, cutting). Wear long non-synthetic, non-flammable clothes when working with the torch. Wear closed-toe shoes or boots. Don't breathe fumes from cutting, heating, or painting. Have fun and take care of yourself so you can ride your bike and pull your bike cart and tell your friends how great it is to not use a car.

Step 2: Cart Fabrication overview

Picture of Cart Fabrication overview
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Fabrication Breakdown(more detail in next steps)

Get 5 pieces of 1/2" EMT conduit and cut and bend in the following manner:

Piece #1:
Full length. Mark and bend at 2", 41", 61", and 100". Overlap the last 2".

Piece #2:
Cut at 59". bend 6 1/2" from each end to make a "U" (spine)
Cut at 38 1/2". bend 5 3/4" from each end to make a "U" (rib 1)

Piece #3:
Cut at 38 1/2". bend 5 3/4" from each end to make a "U" (rib 2)
Cut at 38 1/2". bend at 3/4" from each end to make a "U" (wheel well 1)
Cut at 38 1/2". bend at 3/4" from each end to make a "U" (wheel well 2)

Piece #4:
Cut at 50" and bend a 45 degree bend 10" from end (bottom pulling arm)
Cut at 51", and bend a 45 degree bend 11" from end (top pulling arm)
Cut a 15" piece (arm brace)

Piece #5:
Cut a 72" piece. Bend at 26" from each end to make a "U" (handle)
From flat stock: (1" by 3/16" thick): make (4) 1 1/2" long dropouts with a 3/8" slot.

*Miter the ends of the tubes with a file to fit as shown in the assembly diagram.

*Braze the main-frame, ribs, and spine together.

*Make a dropout jig. each set of dropouts is 4" apart, and space the sets at 22 1/2".

*Put the dropouts in the jig and support the jig level from the ground so that the wheel wells rest on the outside dropouts, and the inside dropouts contact the center rib. Braze.

*Braze the two pulling arm pieces together as shown in the assembly diagram.

*Braze the pulling arm to the front and center ribs. Add the arm-brace.

*Drill a hole in the pulling arm at the end, and attach a 2" long 3/8" bolt as shown.

*Make a hitch out of 1" by 3/16" flat stock, 1/4" rod, and a 3/8" ID tube as shown.

*Make an extended wing nut, attach 2 front bicycle wheels to the cart, paint the joints.

*Add a plywood bed made that is 19" by 38" with notches cut for the ribs and spine.

Step 3: Fabrication of the parts: Main frame

Picture of Fabrication of the parts: Main frame
From the first piece of 1/2" EMT (10' long)

*This piece will be the main frame. With all tubes, make all marks before bending.

*Mark at all the following lengths from one end before bending. Make a small star symbol at the starting end to signify start bending from this side. Mark at 2", 41", 61", and 100".

*Make a dotted line at 118". This will be the mark to which the tube overlaps when it is bent into a rectangle. Eventually, the last 2 inches will be cut off, but the tube is bent with the 2 inches to allow adjustment if the bends are uneven.

*Bend 4 bends to make rectangular shape. With each bend, make sure that the previous bend is in the same plane. Line it up by eye, and fix mistakes by hand.

*Holding the two ends of the tube in overlap of 2", measure the width of the frame at the front and back, before the bends. It should be around 22" or 22 1/2". If the front and back are unequal distances, you can cut off more or less than 2" from the end of the tube. Cut approximately 2" off the end of the tube. Bend the frame by hand so that the two mating tubes are in line with each other.

Step 4: Fabrication of the parts: Spine and one Rib

Picture of Fabrication of the parts: Spine and one Rib
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From the second piece of 1/2" EMT (10' long)

*Cut a piece 59" long, which will be the spine. Cut a piece 38 1/2" long, which will be one of the two ribs.

*Mark the spine at 6 1/2" from each end.

*Bend from each end to create a wide "U" shape, as shown.

*Mark the rib at 5 3/4" from each end.

*Bend from each end to make another "U" shape, as shown.

Step 5: Fabrication of the parts: One rib and two wheel weels

Picture of Fabrication of the parts: One rib and two wheel weels
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From the third piece of 1/2" EMT (10' long)

*Cut another piece 38 1/2" long, which will be the second rib. Mark and bend this rib like the first.

*Cut two pieces 38 1/2" long, which will be the two wheel wells.

***NOTE: If you are going to be using rear wheels for the cart, and don't want to take out the spacers (with hub adjustment), you should add 1 inch to the length of the wheel wells, and cut at 39 1/2" If you don't add length, but use the wider rear hubs, the wheel wells will have less of a slope downward and will be a little weaker. (To visualize this, think about the wheel wells as a part of a structural triangle, from the back of the bike cart looking forward.) You can use any combination of front and rear wheels as long as the diameters are within 1/2".

*Mark the wheel wells at 3/4" from each end. Bend into "U"shapes, as shown.

***Note again. If you added an inch to the wheel wells above, mark the wheel wells 1 1/4" from each end.

Step 6: Fabrication of the parts: Pulling arm

Picture of Fabrication of the parts: Pulling arm
From the fourth piece of 1/2" EMT (10' long)

*Cut a piece 50" long. This will be the bottom arm. Mark and bend a 45-degree bend at 10" from one end.

*Cut a piece 51" long. This will be the top arm. Mark and bend a 45-degree bend at 11" from one end.

*Cut a piece 15" long. This will be the arm brace, and will be cut down more once the arm is on the cart.

Step 7: Fabrication of the parts: Handle and third rib

Picture of Fabrication of the parts: Handle and third rib
From an optional fifth piece of 1/2" EMT

If you don't want a handle, you can save some time and money by skipping the fifth piece which makes an optional third rib and the handle. The handle adds quite a bit of versatility and usability to the cart.

*Cut a third rib that is 38 1/2" long. This is a nice piece for easy attachment of the bed, but is not necessary structurally. Bend at 5 3/4" from each end. Position it where it fits at the back of the cart, mitered where it connects to the main frame and in contact with the spine.

*Cut a piece 72" long. This will be the handle. Mark and bend the handle 26" from each end into a "U" shape. Make sure that the angles are 90 degrees at each bend, or the cart will have a visibly crooked handle.

Step 8: Fabrication of the parts: Wheel Dropouts

Picture of Fabrication of the parts: Wheel Dropouts
From the 3/16" X 1" flat stock

*Cut four pieces 1 1/2" long.

*With a nail or a punch and hammer, make a small dent in the middle of the material (3/4" and 1/2" from the edges). Put the piece in a vice, or clamp it really well. Drill a 1/8" pilot hole, and then enlarge to 3/8".

*Using a hacksaw, cut in from the end to meet the hole. The slot should be 3/8" wide. Make sure your wheel axles fit in the slots. Finish the slot with a file.

*File off the sharp edges.

*Repeat, to make a total of 4 dropouts.

Step 9: Miter the tubes to fit together for brazing/welding

Picture of Miter the tubes to fit together for brazing/welding
Mitering fits the end of one tube with the side of another, to make brazing strong and easy. Miter with half round file or hole saw that makes a 3/4" miter. File the tube end until there is a good fit between the miter and another piece of tubing.

Note: make sure the miters go the right direction and are in parallel or perpendicular planes to the rest of the tube. Each miter should only take about a minute. If it takes longer, use stronger strokes (pushing forward only). To determine which direction to miter, refer to the image of the assembled cart, or below.

*Miter the wheel wells, cutting parallel to the bottom of the "U".

*Miter the ribs cutting perpendicular to the tube (opposite from wheel wells).

*Miter the ends of the spine, cutting perpendicular to the tube.

*Miter one end of the arm brace. The other end will be cut straight at an angle later.

*Miter the handle, cutting parallel to the bottom of the "U".

Step 10: Aligning the frame for brazing/welding

Picture of Aligning the frame for brazing/welding
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The first brazes attach the ribs and spine to the main frame. The cart is upside down for this part.

*Place the main frame on a flat fire-proof surface. Paint flux on the ends of the tubes and inside of the coupling, and slip the two tubes inside the coupling as far as they will go, ensuring that there is flux at the edge of the joint. If the tubes spring back out, bend them in.

*Measure 19" from the back end of the main frame. Use a square to get even measures on each side of the frame. Mark on the side of the tube, so the mark is visible when a tube is placed on top.

*Place one of the ribs between the two marks. Check to see if the miters fit well. If the tube does not fit, bend by hand until it does. Support this rib with bricks, magnets, or other metal scraps, but not right in the center, where the spine will be.

*Mark for the front rib 16 1/2" in front of the marks for the center rib. This positioning is not exact, but should be right where the bends start on the main frame. The front rib needs to stay out of the way of the wheel well. Adjust to fit, and support this rib as well. Do the same for the back rib.

*Mark the center of the front and back ends of the main frame by marking half-way points on the table where the sides are parallel, then by drawing a line through those points to the main frame end pieces. Lay the spine over the ribs.

*Once the pieces are centered, vertical, aligned, plumb, flush, or otherwise how you want them to be, take them all off and coat each surface that will be brazed with flux. Replace all the pieces.

*Read the brazing information on the following pages. Braze the frame together, starting with the ribs. If the spine does not sit perfectly on the ribs, tilt the ribs towards the curve of the spine until there is contact, or bend the spine down to make contact.

Creating the dropout jig
Note: These measurements assume that you are using 2 front wheels from bikes, with 4" distance between the outside surfaces of the locknuts. If you are using rear hubs or hubs with a different spacing make an appropriate adjustment in the jig.

*If you are lucky enough to find 20" wheels, measure the axle width, adjust the dropout jig, make the wheel wells shorter by 6 inches or so, and take off 3 inches off of each side of the ribs and spine to keep the same clearance. (Axle height on a 26" wheel is 13", and on a 20" wheel it's 10".) If your wheels are strong, the cart with 20" wheels should be more stable and stronger than a cart with larger wheels. Move the wheel wells and center rib back by 6 inches to stabilize the cart. If you are going to be making several trailers, I suggest using nylon nuts for this jig. If you are making just one trailer, you could make a cheaper jig from wood or metal rod. As an alternative to nylon nuts, use 2 regular nuts tightened together.

*Measure the width of the center rib from the outside of the one mitered end to the outside of the other end. Center to center will be about 22, and outside to outside will be about 22 3/4". Take your measurement, and subtract 1/4" (to allow the dropouts to sit well against the tube). It will be about 22 1/2".

*Thread on a wing nut on each side, with the flat side of the nut facing out. Slide on two 3/8" washers on each side.

*Thread 2 nylon nuts onto the threaded rod, one from each end. (The side without the nylon has to go on first.) To hold the rod while threading, you can thread two regular nuts onto the opposite end of the rod and tighten them together. Hold this end in a vice or another wrench.

*Thread the first nylon nut 6" onto the end of the rod. Thread the other nylon nut on the other far enough so the distance from the outside of the two washers is the same as the distance measured along the center rib, minus 1/4" (see above, probably 22 1/2" or so).

*Thread another nylon nut onto each side, so that the distance between the two nylon nuts and two of the washers is the same as the spacing for your wheels. For 26" mountain bike wheels, this distance is 4". For road bike wheels, the distance may be less, down to 3 7/8". If you're using rear wheels, it might be 4 3/4" or more.

*Slide on two more washers on each side. Thread on one more wing nut.

Adding wheel wells and dropouts
*Turn the frame right side up. It will rest on just the spine. Place 4 bricks under the front and back ribs to make the main frame parallel to the ground.

*Place a dropout between each set of washers on the dropout jig(4 sets). Align them on a flat surface with all the slots in the same direction. Tighten the wing nuts.

*Use 4 rubber bands or string to get the wheel wells snug against the main frame.

*Find and mark the centers of the wheel wells (about 16" from each side).

*Place the dropout jig with dropouts on bricks/metal scraps, etc, just behind the center rib. It should be at such a height so that when the wheel wells come down to rest on the outside dropouts, the inside edge of the tube rests
with the dropouts. Note: if the dropouts are centered on the tubes, or too far from the wheel-side of the tube, there could be clearance issues with the spokes hitting the tubes, especially on 700c and 27" wheels. See diagrams.

*When everything is aligned nicely, apply flux, and braze the wheel wells onto the main frame.

*Make a small tack braze on each dropout. Remove the jig before brazing the dropouts completely, or the nylon in the washers will melt or the nuts could get brazed to the dropouts. Brazing the dropouts to the rib will require much more heat than brazing two tubes together because of the wall thickness. To keep from burning through the tubes, aim the flame mostly at the dropout.each side, so that the flat sides of the nuts are facing the washers.

Step 11: Safety considerations

Picture of Safety considerations
Safety Considerations:
Ventilation
Respiratory protection
Eye Protection
Heat Protection

Danger of welding galvanized metal (from cutting, welding, and brazing) You are heating galvanized metal, which is coated in zinc. The zinc will burn off and oxidize in the air, creating zinc oxide. Breathing zinc oxide can cause Metal Fume Fever. According to the American Welding Society, Metal Fume Fever causes flu-like symptoms including headache, fever, chills, muscle aches, thirst, nausea, vomiting, chest soreness, fatigue, gastrointestinal pain, weakness, and tiredness. Symptoms start several hours after exposure and last 6 to 24 hours. The American Welding Society claims that there are no known long-term affects from Metal Fume Fever.

Ventilation:
*Braze outside. Portability is one nice thing about oxy-acetylene torches.
*Keep air moving across the work, with a fan or align yourself with wind so that the smoke blows sideways. (If your back is to the wind, your body will stop the airflow in front of your face.)
*Don't breathe the smoke plume.
*Keep your head back from and never above the area that you are brazing.
*Watch the ends of tubes, because fumes will escape from them.

In the process of designing and learning to build bike trailers with galvanized conduit, I got metal fume fever twice, through carelessness. You should be careful, and I think it is possible to braze EMT conduit safely. The sickness felt like the head and body ache that are symptoms of influenza. I felt dehydrated and tired. I felt fine the next morning.

Respiratory Protection:
If you cannot ensure adequate ventilation, wear an N95 (or higher) type respirator. You can buy a N99 filter respirator from McMaster-Carr for $11.09 (Part #53565T2). The instructions say it;s good for 8 hours of breathing through, or until it gets hard to breathe through. 2 replacement filters are $5.61. I don;t like buying from large mail-order corporations, but if the tradeoff is getting sick or not building a bike cart, I will do it.

Eye protection:
Use #5 shade eye protection. If you look at the flame for a second, you;re not going to lose your sight, but it;s bright and bad for your eyes, a bit worst than looking at the sun. I've heard that you're eyes are safe 10 feet back from the flame.

Heat Protection:
Use gloves to touch the metal that you are working on. The brazing rod will get hot close to the end.

Metal Fume Fever Information

According to the American Welding Society, Metal Fume Fever is an illness caused by exposure to zinc oxide, a chemical present in fumes from welding and brazing galvanized metal. The symptoms of metal fume fever are flu-like, including headache, nausea, fever, fatigue, and chills. Symptoms start several hours after exposure and last 6 to 24 hours, although total recovery might not be for 48 hours. High levels of exposure may cause metallic taste in mouth, dry and irritated throat, and coughing. Several hours after exposure, you may have a fever (lower than 102 degrees F, then chills before returning to normal). The OSHA standard for zinc oxide exposure is 5 miligrams per cubic meter of air averaged over an 8 hour work shift. NIOSH uses the same 5 mg per m3 (cubic meter), but suggests that it is permissible for 10 hours per day, or 40 hours per week. They further permit a STEL (short term exposure limit) of 10 mg/m3 averaged over a 15 minute period. There is no published information about long term effects of zinc oxide exposure. (American Welding Society. Safety and Health Fact Sheet No. 25) Even though there are no known long term effects, it doesn't make sense to expose yourself to zinc oxide and potentially suffer from Metal Fume Fever, because it's easy to prevent exposure. Brazing, as opposed to welding, produces fewer fumes because of the lower temperatures.

Step 12: Creating the pulling arm

Picture of Creating the pulling arm
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*Line up the top and bottom arms together on a flat surface with the longer piece, with the hole in it, on the top. Make sure the pieces line up on the long straight side and at the bend. If they don't, bend them until they do. The arm should look like a backwards "L".

*Coat 2" sections of the tubes with flux at 8" intervals (or so) and braze the tubes together. Make it strong enough to be stiff but not overkill. Braze on both sides of the tubes.

*Let arm cool or dip in water. Place the cart on a flat surface with blocks under the ribs to keep them parallel to the ground. (The same position for brazing the wheel wells and dropouts.)

*Support the arm with three piles of bricks/scrap metal so that the top of it is 1" below the bottom of the dropout on the center rib. This should be about 4 1/2" down from the main frame tube. If you are not using 26", 700c, or 27" wheels for the trailer, or if you are not going to make the trailer for a bike with a rear wheel of those sizes, you will want to adjust this dimension. The goal is to have this arm be parallel to the ground and meet the bike 2 inches under the rear axle. The bottom of the trailer should be at least 4" above the ground.

*Flux and braze the arm to the front and center ribs at the same height. This braze needs to be very strong.

*Measure the distance from the point just before the bend in the arm to the front of the spine at the same height. Cut the arm brace to fit here, ensuring that it intersects the arm at least 14 inches from the hole in the arm, and that the angled cut is aligned so that the mitered side fits the spine, and the angle has a decent fit with the arm. Again, accuracy is not that crucial. It just needs to be strong.

Step 13: Hitch creation

Picture of Hitch creation
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The hitch is made from flat stock, a short tube, a rod, a ball joint, and a nut. It clamps onto the left side of the rear axle. There is a slot cut for the wheel's axle, a tube or drilled-out female coupler to allow the ball joint to pivot, and a rod that is braced against the chainstay to keep the hitch from twisting around the axle.

*Start with a piece of the 1" X 3/16" flat stock that you used for the dropout jigs. This will be the hitch plate.

*Cut a piece 3" long.

*Drill a 3/8" hole for the axle 1/2" from the end and 1/2" from each side.

*From one side of the hitch plate, cut towards the hole so that there are 2 parallel cuts 3/8" apart that meet the hole at the widest part.

*Cut the other end at a 30 degree angle. Make the cut so that the shortest side is the side that has the slot cut into it. Make two more cuts to create a place for the ball joint nut to freely spin, as pictured.

*Clamp the slotted end of the piece in a vice at a 30 degree angle from vertical. Clamp it so that the slot is hidden in the vice by 1/2" and so that the end of the piece is parallel to the ground.

*Look at the hitch plate from the side so that the metal angles upward from the vice to the right. Hit the piece with a hammer away from your point of view to make a bend in the hitch plate away from the bike. The end of the piece should be bent until it is about 1/2" away from vertical. The purpose of this bend is to get the ball joint far enough away from the wheel that there are no clearance issues.

*Get a 3/8" threaded female coupler from a hardware store. It will probably be 1 3/4" long. Holding it firmly in a vice, drill out the threads with a 3/8" drill bit. If you have bits close in size to 3/8", start smaller and increase the dimension. If you don't, be really careful doing this part because the bit can grab the metal and twist the drill forcefully. Cut its length in half with a hacksaw. File smooth. This tube will hold the ball joint loosely so it can turn freely. Alternative: cut a 7/8" long piece of tubing that has a 3/8" ID.

*Place the hitch plate on a flat surface so that the end with the slot is sticking up.

*Line up the tube along the angle of the hitch plate, so that the ball joint sticking out of the end could rotate freely. Make sure that there is enough room for a 3/8" nut (which has a 1/2" head) to spin freely at the end of the tube. This needs to be very strong.

*Cut a piece of 1/4" or 5/16" rod that is 8 inches long. Bend the end in the shape shown in the diagrams (a hook to go around the chainstay).

*Braze the rod onto the opposite side of the hitch plate, so that the straight end runs at the same angle as the cut, making sure that it does not hang over the edge of the cut. See diagram for details.

*Put the hitch on a bike through the left side axle. Loosely tighten the axle nut. With a vice, hammer, pliers, or your hands, bend the rod until it fits well on the chainstay and meets the rest of the hitch. The 3/8" ID tube needs to be parallel to the ground and the hooked arm should rest on the chainstay without interfering with the spokes of the wheel.

*File everything smooth. Paint the hitch. Once dry, attach the rod end ball joint through the tube, and secure it with a nylon lock-nut. Make sure the ball joint can spin freely without play.

Step 14: Finishing the cart

Picture of Finishing the cart
*Drill a 1/8" starter hole 1/2" from the end of the pulling arm, and enlarge to 3/8". This hole should be as close to vertical as possible.

*Crush the end of the pulling arm slightly around the bolt hole so a 3/8" nut just slides inside. Slide a 2" long 3/8" bolt through the arm, from the top to the bottom, threaded through the bolt inside the arm. Slip a 3/8" split-ring lock washer on, and then thread another 3/8" nut onto the end of the bolt and tighten it until the tube is crushed around the interior nut. Thread one more 3/8" nut onto the bolt. Make it tight. Option: Braze the nuts and bolt together, and to the arm.

*Take a 3/8" wing nut and braze a 2" long piece of scrap metal onto the two wings. Use some of the rod from the hitch, or whatever you find. This will be the nut that attaches the cart to the bike, and the wing nut extension allows removal without tools. (Alternative: use a 3/8" nut with a wrench.)

*Attach the wheels to the cart. If there are quick release skewers, put the levers on the outside of the cart.

*Paint the joints of the cart with an outdoor metal paint and/or primer. You don't need spray paint. Any anti-rust brush-on paint works. Paint the hitch too, but not the inside of the nuts (clamp hitch). Remove the ball joint before painting the hitch.

*Add a bed. Use 1/2" plywood that is 19" by 38". Use any kind of clamp to attach the bed to the ribs. Plumbing or conduit clamps work. Sheet metal strips with punched holes are cheaper but more work. You could try plumbers' tape, screwing through the holes into the plywood. Cut slots in the plywood to fit the tubes where they curve. This part can be any kind of creative expression. Metal, driftwood, plastic, canvas, plywood, rope, glass--some ideas are better suited to certain applications.

*Make tie-down straps out of old bicycle tubes, with the valve cut off. Use bowline knots to attach them to the main frame.

*A nice option: Add something unique and special to the cart. My personal favorite is a pole with space for art and signs.
"One less car"
"Yes, I'm moving by bike"
"One less car; make it two?"

Step 15: Possibilities

There are many variations on carts using these fabrication techniques and design principles. Please post or send me your photos and comments!

Step 16: Buying and Selling carts

Picture of Buying and Selling carts
I have been working on this design since the spring of 2004. I'm hoping people will be excited about making carts for themselves, but I know some people would rather buy them. If you need a cart and can't build it, email me, and I'll try to connect you with people making carts or build you one. They should cost $100 to $150, for parts and time. So far, carts might be available around Northampton, MA, San Francisco, CA, and San Diego, CA.

If you want make these carts to sell, go ahead, but please include a link to the Instructables page or a copy of the fabrication manual from bikecart.pedalpeople.com My goals are to increase car independence and empower people through fabrication in their communities. Let me know if you sell these carts, and what you think about this project. If you build a cart for yourself, let me know how it goes because I'm continuously working on the design and feedback is useful.

One of the more time consuming parts of cart fabrication is finding wheels and tires and making the plywood bed. One way to spread these bike carts might be to build and sell just the cart body, and let the user find and mount wheels and plywood.

If you want to make a bike cart but can't make a hitch, I will send you one for the cost of parts, postage, and the time for making it (cost is $20 in 2006. $6 for the hitch, $2 for metal stock, for $4 for postage, and the rest for time and gas). I want to increase the accessibility of this project. For more information, contact me at bikecart@riseup.net. These hitches are compatible with Bikes At Work trailers.
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CateC2 months ago

Anyone in NYC available to help me build one of these for an awesome Food Rescue Non Profit?! :) rescuingleftovercuisine.org -- expanding into Brooklyn and want to utilize a bike trailer!

gmichaelt8 years ago
All very useful info, and I've sent reference to the ALLSTEPS to a number of people already. Kudos to the OP and to everyone contributing, whatever the angle; a great resource for velorutionaries. A few questions remain... What's the consensus on the use of muriatic acid - or similar - to make the welding of this conduit less noxious/toxic? Would the use of star-nuts and appropriate bolts and other findings make it possible to build the frame, complete with mitred joins, without welding? If not, could start-nuts and bolts be used contribute to/make for better/stronger joins for the welding? What is the practical limit of the radius of the curve for a given tube - e.g. the conduit referenced here - and how is that limit determined (other than via testing-to-disaster)? In other words, what's the smallest safe radius of a curve to give to conduit using the pipe-bending rig mentioned here? (The questions above are probing in the direction of bending and otherwise securing the longest-possible sections of the conduit so as to minimise the need for welding...) Where can information/discussion on camber be found? In particular, how to determine what limits there are for the degree of camber (positive or negative) when using spoked wheels in this application? And, on a related note, given that the trailer wheels don't take much side-loading, is more-than-moderate dishing of the trailer wheels worth the effort for the modest volumetric gains?
prodnet gmichaelt10 months ago

Muriatic acid works. Heres some demos of getting it out of the inside and the outside.

http://hackaday.com/2013/08/19/on-not-getting-metal-fume-fever-with-galvanized-conduit/

I made this trailer and used 10 inch hand truck wheels so only needed 4- 10' 1/2inch conduit and I welded it all together with a flux core welder

jsadler11 year ago

Material availability is more and more of an issue in the US as well. Metal electrical conduit is about the only reasonably priced metal tubing in many areas. The prices in Home Depot for a common galvanized, steel pipe make me feel like I am buying gold. Copper and brass are off the charts and aluminum is as well. We are not even seeing hardwoods in Florida at sane prices. As less people are "makers" now than in years gone by the industry is not supplying components the way they once did.

farbs8 years ago
Hi! Im 13, and I desperately want to build a trailer. The problem is, I dont own a welding gun (Mainly because im 13) but my moms boyfriend is a carpenter, and I could probably convince him he could use one. If im lucky,he might get one by christmas. Then I could get the parts and make it by Febuary. way too much work. I dont think he would let me use it anyway and its not the same watching someone else build it. So even before I saw this, I decided that I would build a cheap, no-weld trailer. Any suggestions or tips?
aaron (author)  farbs8 years ago
Yeah, check out the plans for the "bamboo trailer" from carryfreedom.com/bamboo.html You'll have to email Nick for the plans. It's a lovely design, and fairly simple. You can build it from conduit, bamboo, wood sticks or poles, (i wouldn't recommend PVC)... Good luck.
Kevvixx aaron7 years ago
If I were to use bamboo, where could I get it?

In many places watch Craig's List under free stuff. Many areas have bamboo in excess and home owners will be thrilled to have you cut down bamboo for free. In Florida I even see the huge timber type of bamboo offered for free. That stuff can be better than five inches in diameter and up to 90 feet tall. In the eastern nations they build large buildings out of structural bamboo. You can also use bamboo covered with fiberglass or epoxy glass for even greater strength and super long life.

Kevvixx aaron7 years ago
what is a good cheap material that I could use since you said that PVC was not a good recommendation?
camb00 Kevvixx7 years ago
copper pipe no welding just soldering but its very expensive now but would be easy to use
This is a good suggestion for ease of costruction, though it would have to be for farely light loads, copper is rather soft. PVC is very sensitive to sunlight, it will scorch and become even more brittle than it already is. Aaron's right, it's a bad choice. Threaded piping/tubing is a good idea. Preferrably aluminum, though steal would work, it'd be very heavy.
I'd say fiberglass tubing would be a good substitute for bamboo. It comes in round and square.


Better yet a person can make their own fiberglass tubes easily with either glass and polyester resin or glass and epoxy resin. Cut your shape in polystyrene insulation, which cuts easily. If using resin you must coast the polystyrene with paper as resin will melt the foam. If using epoxy simply apply the glass and work in the epoxy. Any size, shape, weight or strength can be created. If you do use epoxy you want only white paint as summer heat can turn epoxy a bit soft if painted other colors.

PVC can break with no warning at all. Sunlight is one PVC killer. Accumulated stress is another. Common PVC is not structural PVC. You may discover that the price of structural PVC is a bit outrageous. Simply never trust PVC.

jsadler1 farbs1 year ago

A good way to start is by using nut and bolt construction. If the trailer works well and you are satisfied tow it to a shop that has a good welder and pay him a few bucks to weld it together or simply keep an eye on your nuts and bolts as that method can make a long lasting and very repairable trailer that can be superior to welder units simply due to it being so very easy to change a worn or damaged piece.

zach911 farbs7 years ago
if you were to weld make your sure you were a helmet. the bright light could burn your retina in 15 nanoseconds. thus causing you to lose ability to see.
bumpus zach9117 years ago
"Wear" not "were" "god ppl learn English"
zach911 bumpus7 years ago
Dude its people not ppl
bumpus zach9117 years ago
Aluminum is great. I had a friend in high school who's grandpa built him a trailer using the the 'L' shaped aluminum rod(angle iron). We used it for our surf boards for years. You can use screws to bolt it together. Be sure to use lock washers/bolts. You might also consider looking at reclaiming used material, such as rods from an old patio umbrella, lounge chair, etc. Good Luck and don't stop until you've got it!
You could probably build this same trailer using brackets and pipe fittings instead of welds. Though it may not be quite as strong, it should still be rather structurally sound.
Jkeen1982 years ago
Thanks for great instructions, photos, sketches, and ideas. Just finished trailer using your plans with a few variations and it works great!
Stick welded instead of brazed, used threaded tube, lubed and backed off one turn for swivel connection to tie rod end, and 20" tires. Have less than $18.00 invested!
Thanks again!
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st_indigo3 years ago
Hey Aaron, great instructible, and good job with the documentation of the build.

I ordered a couple 14" wheels from Surplus Center with the intention of making a bike trailer and wanted to pass along the link. They have over 2000 in stock, and they are cheap, durable, and non-pnuematic.

https://www.surpluscenter.com/item.asp?item=1-2770&catname=wheels

The only issue is that they are hub-less, and would need a well-greased axle (9/16", I believe), though long bolts would probably work just fine. The design of the cart also would need to be modified for the smaller wheels.
olmon3 years ago
The neatest hitch idea I have seen yet is at this one - - http://www.instructables.com/id/Welded-bike-trailer/
These Trailers are amazing to look and very useful
co2wms7whcc5 years ago
Really, MIG welding is fairly easy to learn. Especially if you braze, because you will already have practice watching the bead.
Crashbox6 years ago
Here's a cart that started as a trash find. It was an InStep bike trailer I found in a neighbors trash. I welded in a couple of frame supports, changed the hitch, welded up the 3/4 emt tubing, added lights, works great. Crashbox. dog.house9@verizon.net
DSCI1380.jpgDSCI1379.jpg
Crashbox, I am interested to know how you built the axle assembly for this trailer. It looks awesome! I have been creating plans for a trailer like the Y-frame that Carry Freedom builds but I can't seem to figure out how best to mount the wheels without building a 'wheel well'. I like the clean looks of yours.
Eric, Attached are pictures of the wheel mounts.
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bikerusl5 years ago
I would caution people about brazing the coated or galvinized metal. That stuff is extremely toxic, you don't want to breath any chrome! Other than that this is the most professional seeming DIY trailer I've seen. Good job. I build trailers with CrMo bicyclefamily.ca
hackin5hit5 years ago
Thanks for some inspiration!!! Because of this Instructable, I made my own trailer, viewable at

http://undefined-macrolife.blogspot.com/



Thanks again, I will be making one from your design this week. I weld them, and am very much a beginner welder so the welds are ugly (getting better fast though). Anyone in the Olympia, WA area wanting one of these contact me through here or the link, I'll help you build one, it is fun.

So glad that you have this posted on instructables. I was going to make this cart a while ago and lost track of the instructions. It was the first thing that popped up when I googled EMT Bike Trailer. Thanks!

What a great project! I've just cobbled together my first trailer from bits and pieces, it pales in comparison to your professionalism.
Here are some photos. It was the hitch that flummoxed me the most.
http://picasaweb.google.co.uk/clockworkdoorbell/Trailer#
cavegit5 years ago
How do I convert my salvaged rims that I have to bolt on one-side, instead of having to bolt them on both sides of the rim? Almost completed my 2 carts with a 225lb. each weight limit. I used a frame from 2 fold out lawn chairs that I had gotten from CVS for 90% marked down price :)
cavegit cavegit5 years ago
I dont wanna spend $35 per rim for these and i need 4 total :( http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200331764_200331764
goodgnus6 years ago
Almost finished, just need a plywood bed and add some nylon washers to the hitch to stop a little rattle.
trailer.jpgtrailer7.jpg
i think there is buffer between, just steel pin contact is very hard, not comfortable with bike rider
SureShot6 years ago
This is great, thanks for an awesome instructable!!!
this is fantastic! thank you! i've been playing around with trailers for some time. i've got a shabby wooden one right now that squeaks like an old rocking chair. i haven't really tried to max it out. . . it's still needs some finishing touches. this is a great instructable! i love the pictures too! - doug from somerville
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