Recommended tools and consumables: D4 rated exterior wood glue/marine epoxy, yacht varnish, metal paint, panel saw for cutting wood, saw for cutting metal, plane or surform plane, sandpaper (coarse and fine), metal file, wood rasp, cutting fluid for drilling, 32mm drill bit for wood, HSS or cobalt metal bits: 10, 8, 6 & 4mm, center punch, set square, measuring tape, side cutter pliers, pair of adjustable wrenches, drill, clamps with at least 80mm reach, mallet and hammer.
Tools for the project starting from the top, going left to right: D4 rated wood glue, yacht varnish, paint for protecting metal, panel saw, hacksaw with 24tpi blades, surform plane (cheap tool for 'grating' down wood surfaces), sandpaper (P60 and P150 grit), metal file, half round wood rasp, cutting fluid (for using when drilling metal, cools down and prevents drill bits from wearing out when drilling metal), drill bits: 32mm flat bit for wood, 10, 8, 6, 3mm bits for metal (use cobalt bits if you have the option), centre punch (for marking holes), tape measure, side cutting pliers (for cutting and installing shifter and brake cables), 2 adjustable wrenches (going up to 17mm, or a set of spanners: 8,9,10,13, 15 and 17mm), drill, a set of clamps (or an improvised clamp from wood with two bolts), plastic or leather mallet and a hammer.
Parts and hardware for the bike: Two 20" wheels with 36 spokes and 10mm axles, a fork from a children's bicycle with 1" steerer tube (The unthreaded section in the steerer tube should be no longer than 100mm, or alternatively the height of the wooden beam) and a full set of fitting headset bearings. Hardware: Three M6 x 70 bolts with two washers and a nylock nut each Twelve M8 x 60 bolts with two washers and a nylock nut each Four M10 x 100 bolts with two washers and a nylock nut each Two M10 x 150 bolts with two washers an a nylock nut each Stem that fits in the steerer tube of the fork. (the angle must be 90 degrees or less) Two rear-length (approximately 1,2m long) shifter cables and housings Two thumb shifters: front and rear shifter (if the project bicycle does not come with them) Top clamp from a kickstand Two front long reach calliper brakes (the bolt must be longer 30mm) Two rear-length brake cables and housings (approximately 1,2m long) Two wide riser handlebars (and brake levers for one)
There are two options for the wooden frame. One is just to use a good quality slowly grown timber beam, in size 3" x 4" or similar with minimum dimensions of 75mm width, 80mm height and 1200mm length. The second option is to glue laminate the beam using layers of good quality timber on the surfaces with a core of lighter, poorer quality timber. Such glue laminated beam will produce a stiffer and stronger frame that weighs less than the first option. Skip the next four steps if you are not glue laminating. Glue laminating considerations: placing the boards in a stack should produce a profile at least 80mm high, so choose the height of the core board accordingly. Example: the floorboards are 20mm each, and the core 40, which yields the required result. The width of the beam should be no less than 80mm. All pieces should be cut to a length of 1200 mm. For glue laminating, sand or plane the joining surfaces even to prepare for gluing.
Use strong, preferably D4 rated waterproof wood glue.
With a brush, spread glue evenly to all surfaces that are joined.
If you don't have clamps, you can improvise some using scrap pieces of wood that clamp together with 150mm long bolts.
Clamp the pieces together, applying pressure evenly. The more clamps, the better the result. Recommended minimum is 6.
Strip a complete donor bicycle down. Both front and rear derailleur can remain attached. The crankset can be left on if the extractor tool is not available, but removing it makes the building process a bit easier. Clean the frame and the components of dirt and grease to prevent it from contaminating wood.
Mark and cut the the tubes as shown here, leaving approximately 100mm stumps in the top and bottom tube, and splitting the head tube as close to the top tube as possible.
Flatten the bottom tube stump against a wooden surface with a mallet, bending it parallel to the chainstays.
Drill a 10mm hole in the middle of the flattened stump. It is good to file the end round like shown. File off anything that protrudes from the bottom bracket shell and the chainstays. This includes cable guides and the corners of the kickstand mount which are often folded down. The bottom of the frame should be as smooth as shown in the picture.
Taper down a 300mm section of both sides in the end of the beam, narrowing it down to 60mm to facilitate crank clearance. If the beam has been glue laminated, scrape off the extra glue and trim all surfaces even.
Mark the outline for a round groove that is approximately 40mm wide and 15mm deep. Leave a distance of 100mm from the middle of the groove to the end of the frame. An indent will be made here to sink the protruding bottom bracket shell into the frame.
To make the groove, a rough 'v' cut can be made with a panel saw, and then ground round with a semi circular wood rasp or coarse sandpaper around a piece of dowel or pipe. Once the frame can be sat flush against the beam, project down the holes for the rear (where the kickstand mount hole is, or approximately 20mm from the end) and down directly from the flattened stump. It is harder to mark the hole for the stump, so use an engineer's square (anything square will do) to check that the alignment of the marking is right. Use the square to project the holes to the opposing side and make sure they align, too.
Drill one surface at a time, halfway through. When you drill the opposing side, the holes will join. It will help in aligning the drilled hole. First pilot drill with 6mm, and afterwards go through with a 10mm bit.
Use a 150mm M10 bolt and the top clamp of a kickstand to fasten the frame down against the beam in the back. The front requires a spacer block as shown. Find a suitable height piece of wood, cut it and drill through with a 10mm bit. Fasten the flattened tube down, bolting through the spacer block and the beam. Make sure the frame sits straight on the beam. When the rear of the frame is aligned and fastened, slot the cut bottom tube over the top tube stump as shown. Rest the tube on the side of the frame and trace its middle across the top face. Make another line parallel to the beam its middle. Making these lines will assist in maintaining the alignment in the hole to be drilled for the strut. Start by drilling a 6mm pilot hole following the direction carefully. Next drill with a 32mm bit, starting with a slightly milder angle as shown to cut into the wood, and then slowly align it to the marks.
If the angle turns out squint, you can use a round wood rasp to adjust and open up the hole a bit, so that the frame sits as straight as possible. Disassemble the frame.
Measure 200mm from the end of the frame and mark a hole to be drilled as shown. Project it to the other side again, making sure the markings are aligned. Pilot drill halfway through with a 6mm bit, one side at a time, making sure the drilled holes align. Afterwards drill halfway through with a 32mm bit, again one side at a time.
Finish the wooden beam by sanding the all the surfaces smooth to prepare it for varnishing. Round off sharp corners (except for the drilled hole edges) A minimum of 3 coats of yacht varnish will give an adequate protection for the wooden frame when the bicycle is stored outdoors throughout the year.
This drawing shows the placement of the holes. It is a top view, meaning the holes marked with dashed lines are to be drilled through from the side and the holes marked with dots are to be drilled from the top. The dashed lines are all drilled 10mm. The dots are drilled 8mm, exept for the ones marked at 75 and 725: these holes are for mounting the calliper brakes. The measuring line on the top is for the two long tubing sections and the measuring line on the side is for the four short sections.
Even furniture grade (at least 1.5mm wall thickness) 25mm tubing is sufficient for this construction. Metal table frames are often a good source for such material. Source and cut the necessary lengths: four 600mm, and two 800mm sections. Each tube should have one perfectly square end. Use a metal file to square them off. For accuracy, all the measurements should be done from the square end, so mark it well in each tube.
Mark the tubing as indicated by the measuring lines. Do this identically on the facing sides of the tubing. Also remembering to take measurements from the same end. Be careful in getting the marks exactly in the center of the tubing. Indent the marks with a center punch. It helps to align the drill bit exactly, without it slipping off. Drill the holes, starting with 4mm and drilling larger 2mm at a time. Leave the indicated 10mm holes drilled to 8mm. They will be drilled larger later. Drill one face at a time (facing sides should be marked identically), not all the way through to ensure that holes do not go crooked. Take care not to drill the brake mounting holes larger than 6mm.
Enlargin the 8mm hole, drill the marked 10mm holes in the four short tubes that only have a single hole in the middle. The short tubes with three 10mm holes each will be drilled later.
Mark a line through the middle of the fork crown brake hole, ensuring it is perpendicular to the steerer tube. Do this identically on the opposing faces of the fork.
Cut the fork legs off approximately 20mm below this line.
Drilling into a curved surface is a bit tricky. Center punch the marked holes carefully. Align the drill bit against the surface as indicated top right. Drill first on face at a time, and then afterwards once through the whole tube. Drill these holes on the sides to 8mm, and the middle hole to 10mm.
Drill the middle holes of the two short pieces marked with a group of three holes from 8 to 10mm. You will use three of the M10 x 100 bolts for this.
Clamp the fork between the two tubes, align the steerer tube exactly perpendicular to the tubing, and fastening the 10mm bolt tight.
Next drill once through the 8mm holes in the whole assembly, going through both of the tubes and the fork. This ensures the alignment is right. Make sure that the steerer tube does not change alignment. Drill through the assembly with a 10mm bit next, and bolt the sides.
Assemble the tubing as indicated, but do not bolt yet.
Drill through the pairs of overlapping tubes once to correct any misalignment in holes. Bolt the prepared tubing together, only lightly tightening and leaving two corners still unbolted as indicated in the next step.
Mount the wheel axles through the 10mm holes in the middle. Clamp the wheels by bolting the corners together. Tighten all bolts lightly.
Square off the assembly by measuring the diagonal length between corner bolts as indicated. Tilt the assembly to correct the alignment, until both measurements are identical.
Press the headset bearing cups into the 32mm hole in the frame. The order of the bearings is changed in this case, so the bottom part of the headset will now be on the top surface (right) of the wooden beam.
Attach the bicycle frame onto the wooden beam again and mount the front cart on to the frame.
Tighten the bearings and trim off any extra length in steerer tube to fit on the locknut.
Use a stem to make the mount for a stabilising strut underneath the cart. Shorten the stem shaft as shown. There are two ways to make it. Use a cut shaft as shown on the left to bolt the strut onto, or the stem itself with a shortened shaft to hold the strut in place.
A large riser handlebar is good for making the stabilising strut. Cut it to match the width of the cart as shown.
In this example the strut is bolted onto the mount. Align the strut and mark holes to be drilled in the ends. Drill matching 6mm holes in the cart frame.
Use the M6 x 70 bolts to secure the strut ends.
The box can basically be anything that is sturdy enough and you can attach some sort of a handlebar to. An easy way is just to bolt a high riser handlebar off a bmx bike or similar with 3 M6 bolts as shown. Both brake handles will operate the two front brakes independently. Altough it takes a bit of getting used to, so that the bike doesn't steer too much when braking, it is an easy to build solution. Dual cable brake levers and other mechanisms for splitting one brake lever to control two brakes simultaneously are possible. Gear shifters can be mounted in several places, like the seatpost or the frame, but attaching them to the box may place the cables a bit in the way of steering. The rest is just sorting out the brakes and gears, which is pretty much straightforward bike mehcanics. Enjoy!