Introduction: Cheap Short Wheelbase Wood Conversion Recumbent Bike
Or CSWWCRB, for short.
Perhaps you've seen one or two in your hometown, or not at all. Recumbent bikes tend to have a (lets say) "mature" following as compared to it's traditional bike counterpart. Perhaps that's because 'bents are more expensive due to their comparatively low production volume. For this reason, you'll find a lot of people making home built 'bent frames and fairings.
For this project, I'm making a short wheelbase (SWB) 'bent on a very small budget and recycling components from other bikes in addition to a frame. I call it
The WidowMaker
I should mention, WoodenBikes.com is an awesome site worth checking out ;) If it wasn't for encouraging words from the site (and meeting/talking with the man behind the site at Maker Faire) - I would have been weary about mounting a crank in wood :p
One day, I want to build an awesome 4x4 tandem battering ram :D
Step 1: Materials and Tools Used
Materials
1 Womens Beach Cruiser frame with rear wheel and coaster brake
Some pine 2x4
5 Bolts/nuts
18 washers
1 rear derailleur
Scrap .5" PVC and cement
Extra chain
20" wheel from a children's bike (optional)
1 piece crank from another donor bike (which also gave up chain and derailleur)
Tools
2 C Clamps
Adjustable Wrench
Saw
Drill and bits
Hole Saw
Chain Tool
Screwdriver
Hammer (for removing BB cups)
Measuring tape (for measuring X-seam etc.)
Something straight and long (measuring tape works)
Optional
Crank puller (or go to your local bike shop and have them pull your crank - for the non 1 piece crank guys)
There won't be any hack sawing, welding or irreversible changes made to the frame to be converted ;)
Step 2: Measurements
First, measure your X-seam size. X-seam is the distance from your back to your feet in a recumbent (sitting) position. The best way to do this is to sit upright against a wall with your feet outstretched and measure the distance from the wall to your feet.
Alternativly, you can use two chairs. Sit upright in one chair and place your feet on the seat of another chair. Have an assistant push the second chair until your feet reach them. Then measure the distance between the seat backs.
This measurement simulates the distance between your seat and the furthest point on the crank.
Step 3: Harvesting
You'll need:
1 piece crank and BB cups. You'll find these on most cheap American bikes.
Hanger mount derailleur (likely found on a bike with a 1 piece crank)
Chain How to Use a Chain Tool
Disassembling a 1 piece Crank
1. Remove the left pedal (left being the side without the chain rings - clockwise to unscrew)
2. Unscrew Nut on BB (the big one)
3. Remove keyed washer - it must be pulled straight out
4. Unscrew cone bearing race - note the two radial notches. Insert a screw driver and tap the retainer in a clockwise direction to unscrew.
5. Remove bearing retainer (use a screw driver to retrieve it if necessary - it will be greasy)
6. Pull the crank out (slightly) from the right side.
7. Pull right side bearing retainer out of bearing cup (to prevent damage)
8. Pull rotate crank downward so the chain rings go under the BB
9. Remove crank
Removing Cups
Take your screw driver and place it behind the cup, inside the BB (so to remove the right side, place the screw driver through the left side). Tap with a hammer - moving the screwdriver to different portions of the cup (top/bottom works well). The cup should wiggle and pop out.
Repeat for other side.
Rusty Chains
So you have a donor chain that's rusty - perhaps even really stiff? No problem :)
First - break the chain with your chain tool. Pre-soaking the link you'll be breaking with a little penetrating oil is a good idea. The link should also be able to move (even only slightly). Once you've got your chain, take it to the sink and wash any surface rust with soapy water and a scrubby. While washing, work the chain loose if excessive rust has seized the chain. when done, apply a light oil to protect from additional rust. You're not going to get all the rust off - but you'll have a free chain that works ;)
While using rusty chain isn't as reliable as new chain, it's free. I ride on once rusty seized chain - and have only had 1 chain break on me due to sub par chain assembly (I was excited and rushed and said it was "good enough"). But, if you want to go for "new" chain, you'll probably need about 3.5 of them (cheap chain will run you about $25-$35).
Step 4: Bottom Bracket
Start off by attaching a 10" piece of 2X4 to another 2x4. This is best done with bolts as bolts mean adjust ability. To ensure there's no chain ring path conflicts, trace the diameter of the inner two chain rings on your 10" piece of 2x4 (I got by, barely, with shear dumb luck) - also mark the center.
Clamp the smaller 2x4 to the longer one and drill three holes (that match your bolts) - do all holes at the same time. Then bolt together (don't forget washers).
You want the smaller 2x4 on the chain ring side
Now, drill a pilot hole through the marked center for the BB. Be as parallel as possible. Next, use a 2" hole saw (make sure this fits your BB cup) and cut a 1/2 inch deep hole. Don't remove any material yet (just drill the circle). Repeat on the opposite side.
Now, use a 3/4" hole saw and make two cuts to allow reassembly of the 1 piece crank. You need to be able to pass the crank/axle through the wood on that funny angle you used for disassembly. So make the cuts on "top" of each other.
Finally, chip away the 2" recess. Use a chisel, or a screwdriver ;)
Your cups should now press into the wood (perhaps slightly loose). Assemble the cups and reassemble the crank. You may find that the screw no longer fits with the keyed washer in place. I removed the keyed washer (which will require occasional tightness checks later). Re attach the let pedal.
Laugh at the hilarity of a bike crank assembled into some 2x4's.
Step 5: Conversion Frame
Start by attaching two long 2x4's to either side of the frame. They should run from the seat tube, through the headset and at least as long as the front wheel (we'll be trimming later). Fasten with a C clamp.
Now take your crank arm (boom) and slide in between the two long 2x4's in front of the front wheel. Gently fasten with a C clamp.
Using measuring tape, measure the distance from the seat tube to the furthest point on the crank and adjust until it matches your x-seam. Make additional adjustments to allow the crank to clear the front wheel - always making sure you don't go beyond your x-seam measurement (otherwise, you wont be able to reach the crank). Don't forget that you can swing the boom out in an arc and/or move the boom up/down. Don't worry about chain clearance just yet...
Once you've found a position you like. Take your drill and make three pilot holes. Two through the boom/outer wood bits and one though the long 2x4's near the seat tube. Drill your bolt holes and attach your bolts, tightly. Compression is what holds this frame in place.
As a tip, it can be useful to sit in the frame and gently rest your feet on the crank - to ensure your xseam measurements are correct and adjust if necessary ;)
Step 6: Chain and Trim
Now it's time to add your chain. You'll need to chain up your bike with some long chain you've put together - but don't close the ends just yet.
If the chain crosses the path of a turning front wheel, that could be bad. I'm using a derailleur as a chain guide. Simply add a bolt where you want to hand your chain guide from and string your chain through the derailleur as shown.
You can adjust chain alignment using the derailleur's shift adjustment screws.
Step 7: Final Notes
Despite it's problems (mostly fixable - see below), I can do nothing buy smile while riding... And it is ridable :) My father, who has really never ridden a recumbent, got right on and was precariously pedaling away without falling :)
