I need help in making a bridge with wooden sticks.?

Question

I have to go on a field trip tomorrow, and primary part of the trip is to construct a wooden bridge. The bad part is that they are not going to be popsickle sticks (which are nice and flat, and easy to work with) but long ROUND wooden sticks. It is nearly impossible to glue those sticks together without changing the straightness and distribution I am trying to achieve. Another negative feature is that I do not have control over the gluing process. A teacher is responsible for the "crazy glue" and will only glue it FOR YOU ( I dont have a choice) when the bridge is finally ready to be glued to its final position. The bridge will be tested for strength by being put under stress from numerous TEXTBOOKS. I do have ONE partner I can work with, so I am asking if anyone can give me good tips to make a strong bridge and possibly give me step-by-step directions.

Thanx SOOOOOOOOOOOOOOOO much to all who contribute.

Answer 1

Build a wide flange I - beam.  Divide the sticks in to 3 piles 3/8, 3/8, 1/4.  

Lay the 2 - 3/8 piles in to  2- single layers, trim to the sticks so that you have enough pieces to make a continuous "sheet" of sticks just barely long enough to span the distance.  You want the widest possible sheets with no holes.

Divide cut the 1/4 pile in to short sticks whose length is roughly 1/2  the width of one of the sheets.

Divide the length of one of the sheets by the number of short sticks you have.  Divide that number by 2.

Come in 1/3 the width of one of  the sheets on each side and look for a joint where 2 long sticks come together. Carefully push the joint open and put a short stick in it vertically.  Roughly the same number of evenly spaced verticals down each side.  Cut extra joints if needed.

Ask your teacher to glue all the sticks in that sheet together, putting super glue down the entire length of each stick and into every joint.  Let it set..

Turn it over and do the same to the other sheet. working the short sticks vertically into the second sheet.  Cut joints if necessary to glue the verticals.

Tell your teacher that you want glue in absolutely every joint and crack.

Answer 2

Cut the sticks to be used as top chords and bottom chords of the trusses to the exact length needed for your bridge.

Cut the pieces that will be used as studs (vertical truss members) and diagonals of the trusses to fit snugly on the pieces where they will be glued on. This is done by first cutting a V notch at teach end then whittle the ends with a sharp knife until it fits the curve of the piece where it will be glued. Be careful to maintain the correct length of the piece between the notches.

If you are allowed to use sand paper then smoothen the ends and remove any loose material from the ends and the surfaces where the piece will be glued on, before gluing. For the parts (beams) where you will lay the runners (the pieces where you will walk on if it were a real bridge), cut them so that they will  at least be longer than the center- to- center distance of the trusses by at least 4 times the diameter of the bottom chords. Mark the mid-length of each beam and measure half the center-to- center distance of the trusses from each side of the mid-length mark. Cut shallow notches at these points (about 1/4 the diameter of the beam) then whittle on the notches to fit snugly on the bottom chords of the trusses. Again, remove all loose materials from the surfaces to be glued before gluing. Assemble the trusses first in the following sequence:

(1).Lay the top chord and bottom chord of each truss on a flat surface.

(2). Place the middle stud first and tuck glue it to the bottom and top chords.

(3). Proceed to install the other studs in pairs, one on each side of the middle stud, from innermost to outwardmost pairs.

(4). After placing all the studs, install the diagonals also in pairs, starting from the innermost pair to the outwardmost pair.

(5). After the assembly of the first truss, assemble the second truss over the first one to ensure that they are identical. After assembly, ask the teacher to complete the gluing of the joints of the truss parts, one truss after the other.

Now to assemble the bridge:

(1). Stand the trusses on flat ground and tie temporary stick bracings across the top chords and across the bottom chord to maintain the required distance between the trusses.Provide some temporary diagonal bracings to maintain the alignment of the trusses.

(2).Tuck glue the beams to the bottom chords. Install diagonal sticks in between the beam spaces connecting the bottom chords. (These diagonals should also be prepared in the manner similar to that of the beams).

(3). Ask the teacher to complete the gluing of the beams and diagonals.

(4). Lay the runners on the bridge beams and diagonals, and glue to the beams and diagonals.

(4). Allow the glue to completely harden before doing the strength test.