Building the Top Structure

STEP 2 - TOP STRUCTURE

Cut two lengths of spaghetti to 200mm long and tape to the work surface exactly like in step 1 for the bottom structure.

Cut two main support pieces to 200mm long and tape to work surface

Cut five cross braces to 50mm long and place between the two long support pieces so they form four squares 50mm a side. Glue up exactly like in step 1.

Apply cross pieces to form 50mm squares

Apply the diagonal cross pieces exactly like in step 1 and glue up. The finished part will look like the picture below.

Add the diagonal cross braces and glue up

To add strength, add two long pieces of spaghetti in parallel to the assembly, the same as for the bottom piece.

Add strengthening pieces parallel to the length of the assembly

Run glue in the centre of the pieces along the full length.

Glue up the assembly where possible avoiding any blu-tac or tape.

Allow part to dry.

Finished bottom piece glued on one side

Once dry, flip over and glue up the bottom face.

Flip over and glue up bottom face.

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Continue to Part 4

Building the individual elements of the bridge

Basic elements of an Engineered Truss Bridge :

The spaghetti bridge is made up of the basic geometric shapes ...squares and triangles. If you look around you , these can be seen in many places.

Example of a Truss Bridge

The Bridge is made up of 4 elements
1   Bottom Structure
2   Top Structure
3   Left Side
4   Right side

STEP 1 - BOTTOM STRUCTURE

Cut two lengths of spaghetti to 250mm long and tape down to work surface with a 50mm spacing between them.

Main supports for Bottom Structure

Cut six pieces 50mm long to act as cross braces.

Six cross braces, each 50mm long

Align the cross braces starting at one end so they form five squares 50mm a side each.

Cross braces positioned roughly in place.

Once the position is OK, tape the cross braces to the work surface so they stay in place during the gluing operation.


Cross braces taped in position ready for gluing

Ensure the cross braces touch the 250mm long support pieces so that the glue joint can be tight.

Close up of cross braces touching the outer supports.

Pour some glue from the bottle into a small receptacle....an art pallet or old yogurt pot works well.

Pour some glue into a small tray for ease of application

A small amount of glue goes a long way so don't overfill the art pallet.

A small amount of glue is enough to go a loong way.

The glue can be applied by using a small paintbrush. Use an old one as it cannot be used for paint again after being used for glue. A small cocktail stick works just as well.

Apply the glue using an old paint brush...the smaller the better.

A small dap of glue should be applied to each joint.Let the glue seep into the joint. Run the brush down the sides a little but do not allow glue to stick the structure to the mat.

A small amount of glue at each joint will hold the assembly together.

If the sticky tape does not hold the spaghetti pieces well enough , additional support can be provided by using small blobs of blu-tac. Put it where-ever needed but not near a glue joint where it will get stuck to the assembly.

For additional support a small blob of blu-tac can be used.

Once the glue has dried a little and the joint has taken some strength, approx 1 hour, the diagonal braces can be added. Cut a length of spaghetti long enough to span the diagonal in the 50mm square...this will be about 71mm long.

Diagonal pieces add strength but need to be fitted into the corners well.

The ends of the piece should be shaped into an arrow point so they fit right into the corners of the square. This can be done with a sharp knife, a scalpel, a craft knife, etc.The better the fit into the corners of the square, the stronger the glue joint will be.

Continue through the squares with the end point of one diagonal being the start point of the next diagonal.Each diagonal piece needs to be a snug fit and should stay in the square even without glue. when all the diagonal braces are in place, the joints should be glued up as before.



Ensure diagonals are a tight fit and glue up.

Once the diagonals have dried a bit and the glue joints attained some strength, add the final diagonal in two short lengths. Each length going into the remaining corner and touching the existing diagonal at the centre point.

Apply the first half of the final diagonal so it touches in the centre of the existing diagonal

Adjust the second diagonal piece so it makes a straight line from corner to corner.

Complete the final diagonal and glue up.

When completed there will be a full set of five squares with full corner to corner diagonal bracing. The strength of the bracing will come from a tight fit for all pieces.

Full corner to corner diagonal bracing for maximum strength

Once the full assembly is dry overnight, remove all the tape and blu-tac and flip the assembly over. Apply glue to all joints from the unglued side and allow to dry.

Completed Bottom Structure...250mm long

Once the basic structure is dry it is a good idea to strengthen the main supports. This will add strength but also allow a better platform for attaching the side pieces. Cut two lengths of spaghetti the same length as the base piece. Place the lengths alongside the assembled unit so it lies parallel to the long support element.

Add two lengths in parallel to the long edges of the assembly

Position the additional lengths in place and hold in place with small pieces of blu-tac. stick the assembly to the cutting mat with tape to hold it flat.

Hold additional support elements in place with blu-tac pieces.

Put enough blu-tac blobs along the length so the pieces are in close contact along the full length. This will aid gluing and ensure a strong bond.

Push the additional pieces into close contact with the assembly.

 Run a string of glue all along the parts where possible , avoiding getting glue on the blu-tac.

Run glue along the centre contact area of the two long spaghetti pieces.

Allow to dry, then flip over and apply glue to the bottom side. Any spots where the glue was missed can be covered at this stage.

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Continue to Part 3



Spaghetti bridge

To make a spaghetti bridge you will need the following materials :

Some sort of cutting surface to protect the work area. I use a rubber self healing cutting mat that has the added benefit of having measurement grids marked on it.



cutting mat to protect work surfaces

To make a spaghetti bridge you need ...........we'll..duh.........spaghetti.....the long string kind.

Use the long string spaghetti..the cheapest brand you can buy.

To ensure it is possible to glue the spaghetti together it will be necessary to stick the spaghetti to a flat surface while the glue dries. I use sticky tape and bits of blu-tac. Small pieces are best so they don't get in the way of any gluing later on.

Use any type of tape but make sure it comes of easily or else the spaghetti will snap.

To cut the spaghetti to length I have found the best way is to score it slightly with a sharp scalpel or knife and then to snap it by hand..it breaks really easily. 

Use a sharp craft knife, scalpel or blade to gently score the speghetti then snap by hand.

While the whole idea of a spaghetti bridge is that it is fun, it is also an engineering project so you need to be somewhat accurate. Therefore a ruler is a great idea so you can have all the bits the same size. Usually it is better to slightly oversize your pieces and then they can be shaved to size as required.

a small steel ruler is ideal for sizing your spaghetti pieces.

To glue the spaghetti pieces together I use a PVA glue. This sticks well and dries clear so you cannot really see the glue joints. Note that any glue is going to soak into your spaghetti causing it to swell and distort so make the glue joints as small as possible. To make the glue handling easier I pour a smll amount into a plastic tray.....and old yogurt pot works just as well.

Use a PVA glue to stick the spaghetti together

In order to get the glue in the right spot I use a small old paintbrush with a fine tip. Dip the paintbrush into the PVA glue and position it where required on the spaghetti joint. A toothpick or small needle would work just as well. Note you cannot use the paintbrush for painting again so make sure it is an old one you have no further use for. Keep it for applying glue only.



Use a fine paintbrush (old one) to position the glue exactly where you want it.

Continue to Part 2