The Bridge and Crane System

Intro: The Bridge and Crane System

We are team Fast & Five, freshman students from University of Michigan - Shanghai Jiao Tong University Joint Institute(UM-SJTU JI). The Joint Institute is an international institute which has the privilege that it inherits and develops both the features of Shanghai Jiao Tong University and the University of Michigan.

Course and Project Information

VG100 Introduction to Engineering is a unique course of JI emphasizing innovation by letting students design and manufacture their own works. Our first project for 2016 Summer Semester is to build a bridge-and-crane system, which consists of a bridge and a cart. The bridge is required to bear the weight of a full cup of water and the cart is required to carry a cup of water and move from one end of the bridge to its center, rotate the cup for 180◦ without spilling and return to the starting point.

The regulations and rules are:

• The final grade contains four parts

(a) Time used to achieve the required motion; time penalty (+15 seconds) if spilling happens (40%)

Score = lowest time achieved / your time ×40%

(b) Weight of the bridge structure; severe deduction of score if bridge collapsed (40%)

Score = (lowest weight achieved / your weight )^2 × 40%

(c) Best design of moving cart. (10%)

(d) Best design of Paper Bridge. (10%)

• The bridge should be built of A4 paper and white, non toxic white glues.

• No more than 2 sheets of paper is allowed to be stacked.

• The length of the bridge should be no less than 1.1 meters.

• The width of the bridge should be no more than 0.5 meter.

• The weight of the bridge should be no more than 200 grams.

• The center of the bridge should be marked.

• The cart should be controlled by an Arduino board.

• The dimension of the cart should be no more than 0.1 meter

• No more than two portable Power Supply is allowed and each battery voltage should be less than 12V.

• The motor should be less than 12V.

Our Design

We use the truss structure to build the bridge. This structure allows the bridge to disperse the pressure so that the bridge can bear a relatively bigger load. The bridge consists of two rails, which helps reduce the weight.

Our cart uses a servo to rotate the cup, which means that the cart itself does not rotate. We adjust the revolution speed of the motor so that the two rear-wheels have the same speed. This ensures that the cart will go straight without deviating from the track. We do not install any sensor on the cart. Instead, we control the direction of the revolution of the motor by coding through Arduino. Thus the cart can move forward from the starting point to the center of the bridge and then move backward to where it starts .We also stick one disc to each of the four wheels to make sure that the cart does not fall from the bridge.

Our Performance

Our bridge weighed 55.7 g and the cart spent 5.81 s to finish the competition. The bridge bears the moving cart successfully and the cart moved steadily without spilling the water.

Here is the video of our performance on the GAMEDAY: http://v.youku.com/v_show/id_XMTYxMTU2MzM3Ng==.html

STEP 1: Materials Required

Materials for Bridge

1. A4 Paper*20

2. White Wood Glue*1 ¥4.80 https://item.taobao.com/item.htm?id=45407057330

3. Round Stake (ϕ 1mm × 500mm)*1 ¥1.67 https://item.taobao.com/item.htm?id=25352060676

4. Quadrate Stake (1mm×1mm×500mm, 10 in 1 set)*1 ¥29.7 https://item.taobao.com/item.htm?id=24966484414

Materials for Cart

1. Arduino Nano 3.0*1 ¥ 12.45 https://item.taobao.com/item.htm?id=45365214068

2. TB6612FNG Motor Driver*1 ¥ 13.80 https://item.taobao.com/item.htm?id=528401378083

3. GA12-N20 Gear Motor*2 ¥ 14.33 https://item.taobao.com/item.htm?id=525167243889

4. Plastic N20 Motor Mount*2 ¥ 0.60 https://item.taobao.com/item.htm?id=525688077733

5. Tower Pro SG90 9g Servo*1 ¥ 12.00 https://item.taobao.com/item.htm?id=524783267178

6. Toothpick*2

7. AAA*3 Battery Holder*1 ¥ 0.65 https://item.taobao.com/item.htm?id=37956775836

8. 10440 Lithium Battery 3.7V*3 ¥ 10.00 https://item.taobao.com/item.htm?id=20611223196

9. 2mm Acrylic Board (15cm*15cm)*1 ¥ 6.50 https://item.taobao.com/item.htm?id=521003211385

10. Tyre*4 ¥1.25 https://item.taobao.com/item.htm?id=527429292853

11. Cup holder (3D Printed)*1

12. Axial position limiter*4 ¥ 0.10 https://item.taobao.com/item.htm?id=521116202225

13. Shaft mount*4 ¥ 0.20 https://item.taobao.com/item.htm?id=16079459076

14. Dupont Lines(F-F, 40 in 1 set)*1 ¥ 4.62 https://item.taobao.com/item.htm?id=16079459076

15. Bolts and Nuts (M2,M3)

***The link given are from Taobao, the website where we bought the materials, you can also buy these materials on Ebay or any other websites.

STEP 2: Making Paper Rolls and Paper Rods

Paper Rolls

• Take 10 pieces of A4 paper. Cut each pieces of A4 paper into 3 pieces, each of which is 65mm in width and 297mm in length.
  Tips: Cut every piece of paper with paper knife patiently and DO NOT HURT YOURSELF.

• Fix the round stake (10mm in diameter) by the length side of the paper (297mm), and roll it up.

• Apply a coat of clear glue on the edge of paper after rolling for a round and a half.
  Tips: The glued edge of the paper should be parallel to the length side of the paper.

• Roll it to the end to make a two-layer round paper roll. Repeat the procedures 30 times and get 30 round paper rolls.
  Tips: The round rolls should be completely dried up before being used in the following steps. The strength of the round paper roll will be harmed if the roll is bent before dried up. Move the completed paper rolls gently in order to maintain paper roll’s shape before the glue dries.

Paper Rods

• Use the quadrate stake (10mm in length) and by the length side of the paper (297mm), and roll it up by one round and a quarter.
• Apply a coat of clear glue of 10mm width to the edge of the paper.
• Roll it up with a quarter round and makes a one-and-a-half-layer paper rod.
• Cut the edge of the paper roll with the paper knife and get the paper rod. (Be careful with the knife!!!)
  Tips: Another person can pull the opposite side of the paper to make it attached more closely to the stake so that the roll will be more durable.
• Repeat the procedures 10 times and get 10 paper rods.
  Tips: The quadrate rods should be completely dried before being taken in the following steps. The strength of the quadrate paper rod will be harmed if the roll is bent before being dried. Move the completed paper rods gently in order to maintain paper roll’s shape before the glue dries.

The previous steps may take about one hour to complete. We now have 30 round paper rolls and 10 paper rods.

STEP 3: Making Tracks

• Obtain one dried round paper roll and two dried quadrate paper rods.
• Mark the middle point of the paper roll with the pen.
• Apply a coat of clear glue to the whole outer surface of the paper roll.
  Tips: The glue should be applied evenly to avoid fragility of the structure.
• Plug the paper roll into the paper rod until it reaches the marked middle point.
  Tips: Use one hand to compress the paper roll in diameter for about 0.5mm so that it can be plugged into the paper rod.
• Quickly plug in another rod from the other side and pull it to the middle point to make a long stick.
• Glue another roll and plug it into the long stick rod with half of the length inside and half remaining outside.
  Tips: The signs of half the length are marked with the pen, and make sure your measurement is as accurate as possible.
• Repeat steps for 3 times and get the long stick of length 1188mm, which makes a track.
  Tips: Plug in the round paper roll with glue quickly into the quadrate rod before the glue dries.
• Repeat all the above steps again and make another track of the same size.

The previous steps may take about half an hour to complete. We now have two tracks (Figure 3.7)made by paper rolls and paper rods.

STEP 4: Reinforce the Bridge

• Obtain three round paper rolls and cut one of them rolls by 50mm with the scissors.
  Tips: Be careful with the scissors.
• Attach a coat of glue on the middle point (594mm) of the track by one side.
• Glue the shortened roll vertically on the middle point of the bridge and wait it to dry.
  Tips: The area of the contact surface between the glued roll and the track is quite small, so you should fix the vertical roll when it is being dried.
• Attach a coat of glue 100mm left from the middle point and on the endpoint of the vertical paper roll.
• Attach a roll of original length one side on the glued point and another side on the glued endpoint.
  Tips: Do it before the glue in above step dries. Be careful and make sure you don’t break the vertical roll while doing 5. Two people cooperate to finish this step is recommended.
• Do as the above right from the middle point.
  Tips: Every step should be operated after the glue applied in the previous step is completely dried.
• Obtain three round paper rolls. Cut one of them by 100mm with the scissors.
  Tips: Be careful with the scissors.
• Attach a coat of glue on one of the quarter points (at 297mm) of the track by one side (same side as the previous step).
• Attach the shortened paper roll vertically on this point and wait it to dry.
  Tips: The area of the contact surface between the glued roll and the track is quite small, so you should fix the vertical roll when it is being dried.
• Attach a coat of glue on the left side 197mm away from the quartered distance point and on the endpoint of the vertical paper roll.
• Attach a roll of original length one side on the point and another side on the endpoint of the vertical paper roll.
  Tips: Do it before the glue in above step dries. Be careful and make sure you don’t break the vertical roll while doing Two people cooperate to finish this step is recommended.
• Do as the above right from the quarter point.
  Tips: Every step should be operated after the glue applied in the previous step is completely dried.
• Do the same steps on the other quarter point (at 891mm) of the track.
• Repeat the whole procedures on the other track.

The previous steps may take about forty minutes to complete. We now have two bridge tracks with piers on its upper side.

STEP 5: Add Belt and Finish the Bridge

• Obtain two pieces of A4 paper and cut according to its longer edge into 7 pieces, with each of the paper 30mm in width and 297mm in length.
• Attach glue on the surface of one piece and attach another piece onto it to form a two-layer paper belt. Notice to make alternate permutation of the two layers.
• Repeat the step 5 times to get a long belt.
• Repeat the steps to make another long belt.
• Attach a coat of glue on the ends of the three vertical paper rolls and both ends of the track.
• Glue the paper belt on the track and cut the surplus part of the belt. Wait it to be dried.
  Tips: The belt should be glued with tension on the paper in order to strength the structure.
• Repeat the step to attach another paper belt on another track.
• Obtain four round paper rolls. Cut all of them with 129mm length remaining with the scissors.
  Tips: Be careful with the scissors.
• Mark the two quarter points and the middle point of the track on their adjacent side with the pen.
  Tips: When you use pen to mark on the bridge, mind the force you apply on the bridge in order not to hurt the structure of the paper track.
• Attach a coat of glue on these points.
• Connect the two bodies of bridge with the three shortened rolls at these points. Wait it to dry.
  Tips: Be sure to keep the two body bridge parallel as long as the glue is still wet so that the distance of the two bodies would remain 129mm between the two sides of the bridge.
• Attach a coat of glue on the endpoint of the longest vertical rolls on both tracks. Connect them with a shortened roll of length 129mm at these two points. Wait it to dry.

The previous steps may take about twenty minutes to complete. We now have the completed paper bridge.

STEP 6: Components Preparation for Cart

• Cut one piece of acrylic board as the drawing. Note that some of the holes may be slightly changed according to the materials you have.
• 3D-print a cup holder that well fits the disposable cup (or you can also use another disposable cup to be the cup holder).
• Take two toothpicks, cut each to be 4cm long using scissors. Note that both sharp ends should be cut. Take four disposable cups. Cut each cup so that only the bottom part remains. Then dig a hole which is sightly smaller than the tyre on the bottom.
• Solder the female Dupont lines to 4 pins of gear motors.
• Cut the origin Dupont pin and solder the female Dupont lines to each wire.

STEP 7: Components Assembling

• Install the pair of motor mount and gear motor onto the acrylic board.
• Use glue to fix the tyres to the axis of the gear motor. Note that you can start the gear motor after the process to avoid the gear set being sticked. Repeat steps on the other side of the board.
• Put the servo right into the rectangular hole on the board from the lower side. Fix it with screw bolts.
• Fix the battery holder on the lower side of the acrylic board.
• Stick the shaft mounts onto the acrylic board in the corresponding place (or use the screw bolts to fix them).
• Wrap one end of the toothpick with electrical insulation tape so that the tyre can be fixed on the toothpick. Repeat the step on another toothpick and tyre.
• Install the sets of shaft and tyre onto the shaft mount. Use axial position limiter to fix the position of tyres. Note that the front tyre and the rear one on every side should be on the same plane.
• Stick the bottoms of the disposable cups prepared before onto the tyres.
• Fix the Arduino Nano and Motor Driver on the rear of the cart.

STEP 8: Connection and Programming

Connect the components by following the connection diagram given.

For this cart, our goal is to 1) Rotate the cup, i.e. rotate the servo; 2) Make the cart move forward for 50cm, and then move the cart reversely to the start line. The program should include both functions.

For more details about how to program with Arduino, please refer to https://www.arduino.cc/en/Guide/HomePage.

Now we finish the cart

STEP 9: Overview of the Whole System

Comments

[DIY Hacks and How Tos]

Cool project. The bridge project was my favorite project as a freshman.