Pencil Bike

What could be more practical than a bicycle that doubles as a pencil?!  It is surprisingly easy to make this fun and functional 'riding implement' out of an old kid's bike and a 4" x 4" wooden beam. 

See Woodenbikes' genius "CAD" instructions to create a cardboard cutout of your body, so you can figure out proper positioning of wheels/seat/handlebars/etc.  As he says...

"Using a sophisticated 2D CAD system (Cardboard Aided Design) life size cutout of your foot/leg thigh/back and arm, pivoting on brads at the joints, you can design the bike on the ground to explore sizing and clearance issues.  My CAD system sometimes has a Gooey interface if I spill something on it while designing :-)
More seriously, like other CAD systems it has a GUI (Graspable User interface).

Make a cardboard cutout of your lower leg (with foot and pedal), thigh, torso, and straight arm (to a distance 2" back from your wrist). Use it to look for good riding position and clearances for knees to bars, heels to wheels etc. Use the CAD system to layout the riding position, cranks, wheels etc with attention for locating your hands, shoulder, seat-back angle, butt, knees and feet.

For detailed instruction on 12 Steps to designing a sweet handling recumbent, visit Bikesmith Design at  http://bikesmithdesign.com/Design/12Steps.html 
 

This is the 4x4 beam and the kid bike we used.  The kid bike has 16" wheels and a coaster (back pedal) brake for simplicity. 

Disassemble the donor bike paying attention to how the wheels attach to the frame, how the stem attaches to the steerer tube (in the fork), and how the pedals detach from the cranks (hint: they unscrew in the direction they would unscrew if you were pedaling forward and they "locked up".  (e.g. Rt foot pedal unscrews normally, and Left foot pedal unscrews strangely).  Remove the bottom bracket* lock ring (also reverse threaded) and remove the BB cone and ball bearing race (the set of metal balls held together (hopefully) by a clip).  Keep all these crank and BB parts together in a box since you will reassemble and disassemble them several times as the project progresses.


* The bottom bracket (BB) is the main crank axle bearing

With the head angle figured out to give proper trail ( the link is to a description of bike steering geometry and "trail" https://www.instructables.com/id/Mountain-Bike-Scooter/#step1 )  Mark the headset (HS) center point on the top of the beam and use a carpenters square to mark the position out to the side and to mark it at the head angle to indicate where the bottom HS hole will be centered on the underside of the beam. 

Use a hole saw (cylindrical toothed drill bit) to drill the larger outer hole first that will support the outermost diameter of the HS cup.   Drill it to a depth you want to set the cup, preferably just deep enough to surround all of the cup.  (If you drill too deep and mount the cups too close together there is excessive leverage of the steerer tube on the two cups.)  Repeat for the top HS cup.

Use a smaller diameter hole saw that matches the extended cylinder of the HS (where it was pressed in the metal bike's head tube) to drill the next hole deep enough to allow the HS cup to be pressed firmly into the beam.  Repeat for the top HS cup.

Now drill the approximately 1 1/8" steerer tube hole in from the top and in from the bottom until the holes meet in the middle of the beam.  It's OK if they don't align perfectly.  you can use a rasp to smooth the transition between them.   Gently use a chisel to chisel out the remaining cylinders of wood left between the cylindrical holes cut by the hole saws.   Be careful to leave a smooth floor of wood to support the flared out floor of the bearing cups.

Now the bearing cups should be able to be fit in the holes and be seated on wood (not floating).

We drew pencil lines to mark the center point locations for both sides of the BB holes.
Drill the largest diameter holes first (While you have good solid wood to hold the hole saw's stabilizing center bit).  First drill all the holes and then come back to chisel wood out of the cylindrical cuts of the hole-sawed holes.  (This leaves maximum wood to support the drilling operation.)
Using a hole saw selected to match the outer cylinder diameter of the bearing cup for a fairly tight fit.  On the bike's right side (where the chain ring will be) drill/saw only as deep as needed to set the bearing cup in up to its protruding lip.  Stopping at that level maximizes the supporting wood left in place as a "floor" to the hole.  That floor helps support the cup.

From the left side of the bike Drill/saw the large hole to a depth that would have the bearing cups' outer protruding lips about 2 7/8" apart.  That will about match the donor bike's original BB width (cup face to cup face).  e.g. our inset depth was 5/8" below the surface (3 1/2" inch "4x4" minus 2 7/8").  This means the left cup would be about 5/8" inset into the 3.5" thick wood.   Or you could slice about 5/8" off of the left face of the beam (so it's 2 7/8" wide) and mount the cup in to its lip depth just like the right side.  We chose not to slice, but to drill deeper to preserve structural and artistic integrity (this time).

Drill 3 holes a little bigger than the BB axle (about 5/8") to form a slot in a direction that will accommodate threading the crank through the slot. 

We let the top and bottom planes of the 4x4 remain intact (but narrowed) and cut slanted strips off the two side faces of the 4x4 with a table saw to make a hexagon cross section.  In the area where the BB and head-set* would be drilled through the wood, we left the 4x4 uncut to leave maximum wood for support of the holes and bearing cups.  A draw knife is a fun way to shape the transition and to shape the point.


* Head-set is the main steering bearing in a bike frame that connects the fork to the rest of the frame.  The Head-set has bearing cups and cones that thread onto the fork's steerer tube.

We actually did wear eye protection while building the bike.  I (WB) have had a piece of rusty steel cut out of my cornea by an eye surgeon after my ophthalmologist looked at it, got very quiet, and had to leave the room.  I can still use that eye for eyeballing measurements, but everything is off about 1/4 of an inch :-).  So always, eat your veggies and wear your goggles.

The handlebar stem is cut carefully with a Sawzall ("cut carefully with a Sawzall" is an oxymoron, but we do the best we can) in a plane that anticipates the welding of a piece of square steel tubing in between the two offset pieces of the cut stem creating a very tall stem.  (It has to be tall for knee clearance under the handlebars while pedaling.)  Use the CAD system with the knee up to see how high the bars have to be to clear the knee.

There are different ways to do this.  After much hemming and hawing, with considerable chin scratching we welded a piece of steel to the cut ends of the seat stays and then drilled holes  through the steel and attached it to the beam with stout wood screws.  We drilled holes through the remaining half of the BB shell and screwed it to the 4x4 with stout wood screws also.  

The seat is made from a chair back.

4 inch diameter aluminum flex duct is used to connect some used polyethylene packing foam to the pencil wood, mimicking the band that is used to do the same on regular pencils.  The foam was easy to cut into an eraser shape and was painted eraser pink.  It has a great texture.

Ellen assembled the long chain out of regular bike chains following this handy instructable about using a chain tool.  https://www.instructables.com/id/Using-a-Bike-Chain-Tool/    After  the chain was attached, it was tightened by simply positioning a chain tension roller wheel from a ten speed derailleur somewhere along the beam where it would both lift the chain above the front wheel and snug up all the slack in the chain. 

So many ideas.  So little storage space.

Hopefully you will be inspired to make your own fun bikes!

Happy Trails!