Overview of tailbox construction process

Keeping the tailbox contents dry, long term durability and low materials
cost are the primary objectives.  Thus, actual labor time to build the
tailbox tends to be long.  The tail box described below took 20-30 hours
to complete.  Final materials include: Coroplast (4 mm thickness),
silicon window sealent, nylon bolts, washers and nuts (1/8 in. OD, 1 in.
length) and standard rear bike rack.  Temporary materials include:
cardboard, duct tape and sheet metal screws (1/8 in. OD, 3/4 in. length).

The construction process has 3 phases: 1) cardboard mock-up, 2)
preliminary assembly, 3) final assembly.  The mock up phase involves
cutting cardboard and taping the pieces together on the rear bike rack. 
When working with cardboard and duct tape it is easy to see what works
and fits, then make the needed adjustments.  Next I examine the mock tail
box and decide where the seams and folds will be.  Using a knife I first
cut all the seams that will join two pieces of Coroplast.  For all of my
tail boxes this has meant 4 pieces: lid, left side-back-right side, front
(ie the piece immediately behind the seat back) and the bottom-inside
(covers the rear rack).  Next I decide how to make the folds.  Most tend
to be simple 90 degree (or other appropriate angle) folds, however the
bottom inside piece has a number of complex folds because I want to
minimize seams to improve weather proofing. These four cardboard pieces
are now cut at the "folds" in order form a pattern which can placed flat
on the Coroplast sheet.

With the cardboard patterns in hand it is easier to make optimal use of
the Coroplast.  The most recent tailbox for my Touyr Easy was made from 
a single 4X8 ft sheet.  The larger tail boxes made for the Linear tandems
used 3 sheets for two tail boxes.  Also, arrange to Coroplast "flutes" to
provide maximum strength for the large unsupported areas (like the
sides).  Once the pattern placement on the sheet is determined tape them
in place and trace them.  Use a straight edge to correct imperfections in
your pattern as needed.  I typically use the patterns to locate the
corners, mark them with dots and then use a straight edge to connect the
dots since my patterns tend to have wavey edges. I also mark the places
that will eventually become folds.  Next the Coroplast pieces are cut
using the straight edge and knife.  Be sure not to cut on the fold marks.
 

Using a heat gun and paint scraper blade I make all the folds.  First I
heat each fold and press the scraper blade along the line marking the
fold.  This compresses the Coroplast flutes.  Several heating and
pressing cycles are usually necessary for each fold.  To complete the
fold I heat the entire length of the fold, on the inside of the fold,
then fold the parts of the Coroplast farther than will be needed (it will
unfold partially).  Hold in place until the plastic cools.  The
bottom-inside piece has many folds and is quite time consuming and
tedious but the reward is minimal places for leaks to occur.

Now that all the pieces are cut and folded it is time for preliminary
assembly.  Place the bottom-inside on the rear rack.  Tape in place so
the sides won't pop out and look like wings.  Tape the side-back-side
piece in place.  Use the sheet metal screws to fasten the two pieces
together.  Place the screws at the same locations that the nylon bolts
will be in for final assembly.  Repeat the sheet metal screw assembly
with the front piece as well.  Install the lid as well.  At this point
you have the tailbox as it will look after final assembly.  If you want
to make changes this is the time to do it.

On the Linear tail boxes I have left the top 8 inches of each seam
between the front and sides unbolted so I can slide the seat support rods
through.  Then the seam is taped closed so the tailbox is removable.

Remove the tail box from the bike.  Unscrew the lid and remove.  Unscrew
the front and remove.  Take out a few screws from the side and bottom
seam.  Squirt  sealant into the seam and put the nylon bolts, washers and
nuts into the holes.  Work your way around replacing screws with bolts. 
Once this is complete fasten the front piece in a similar manner and
later the lid.  Let the sealant dry over night and the tail box is
complete. I've added Coroplast pieces to hold tail lights in all cases.

Below are the picture titles and captions. Click on picture for larger image.

1 TE mock-up - bottom
Mock-up of the bottom-inside.

2 te mock-up - sides
Mock-up of the left side-back-right side.

3 TE cardboard mock up - top
Complete mock-up viewed from the top with the lid open.

4 TE cardboard mock up - top 2
Complete mock-up view of the inside.

5 TE carboard mock up - front
Front view of the mock-up.  This is the side that will be against the
seat back.

6 TE cardboard mock up - bottom
Underside view of the mock-up held by helper Sharon.

7 TE folded bottom - back
Coroplast bottom-inside with folds.  Viewed from the back.

8 TE folded outside - front
Coroplast left side-back-right side with folds.  Viewed from the front.

9 TE tailbox complete - rear
Finished tail box on the bike.  Viewed from the back.  Bright spots are either tail lights or reflective tape.

10 TE complete- inside from top
Finished tail box.  Lid open.

11 TE tailbox - complete - side
Finished tail box.  Left side.  Black strap on upper left corner has
plastic buckle to keep lid closed.

12 TE tailbox- inside lock down
The top of the rear rack extends through the inside.  A piece of foam and stiff black plastic is wedges under the "hoop" to hold the tail box down on the rack.  This is not needed on the Linear tail boxes because the seat support rods fasten to the frame and hold the tail      box down.

13 CP1 tail box - top
Coroplast tail box used on Linear co-pilot tandem #1.  Internal volume is much larger than the Tour Easy tail box.

Mark Bruce
adlc@jbic.com

Mark Bruce

"A gentle answer turns away wrath,    
but a harsh word stirs up anger."         @   
Proverbs 15:1                            _\\/_/\-%