sam lindop l018852a transport technology technical report

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    ContentsAbstract ................................................................................................................................................... 2

    Introduction ............................................................................................................................................ 4

    Testing ..................................................................................................................................................... 5

    Design development ............................................................................................................................... 6

    Results ..................................................................................................................................................... 8

    Conclusion ............................................................................................................................................. 12

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    Abstract

    A chassis is the internal framework that holds together the external body parts of the car, and all the

    working mechanisms in the car. Our task was to test three types of chassis that were pre-made and

    make two more chassis of our own. The first one had to be made of card and we could strengthen it

    anyway we wanted without exceeding a weight limit of 53g or impede the door or internal space

    and allowed there to be room for transition tunnel. The other could be made any material but have

    the same rules as the first chassis. It was our target to get within 75% of the torsional rigidity of the

    full chassis. To test them we used a pre-made rig that has poles going through the back and front of

    the car and hold them in place, the front however has an extended pole where you can apply

    weights and was on a pivot, the more the bar moves then the weaker the chassis. The results for the

    first chassis we made an improvement of 5.75mm however still only had the torsional rigidity of

    0.058, and for the unlimited chassis it was 8.21mm improvement and the torsional rigidity of 0.092.

    However with these results there still wasnt enough to reach the 75% target which was 1.162. Afterthe tests we concluded that the best place to improve was the transmission tunnel and bulkheads.

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    IntroductionA Chassis is an internal framework in the car the holds together the external body parts and internal

    mechanisms of the car. It also aids in safety because it acts as a protective shell to protect the

    passengers inside. The chassis also affects the ride and handling of the car because a chassis that is

    too flimsy will not be able to deal with the torque produced from the engine so wont be able tokeep the contact patches of the wheels on the road and they will not be very safe in crashes. This is

    the same if the chassis is too rigid, as it goes around a corner it wont be able to deal w ith the g-

    forces so you will get unnecessary body roll and therefore not be able to keep the wheels in contact

    with the road. One of the places engineers and designers try and improve the most is the rigidity of

    the chassis on road cars. Most modern convertibles chassis are based on the hard top versions of

    the car. These hard top versions use the windscreen and roof to improve the rigidity, therefore when

    the roof is taken off the chassis is a lot less rigid and the designers need to find ways to compensate

    for the loss.

    The chassis we will be given to test will be made of card and super glue and our task is to use theseas base models to design our chassis around and think of ways to improve the convertible chassis.

    Possible ways to this is by using triangulation and box section to improve the weaker parts. These

    will be beneficial to the chassis made of card. We also have to make a chassis made of any materials

    we want, however it has to be in the weight limit of the regulations. This was not to exceed 115% of

    that of the weight of the full chassis, this gave us a limit of 53 grams.

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    TestingTo test the chassis we were split up into groups of four so that we could work together. To test the

    chassis we had to place them on a pre-built rig which holds the rear in place and the front on a pivot.

    From one side you apply the weight and the other you measure how much the bar moves using a

    digital vernier calliper. The more the bar moves the weaker the chassis is. We will apply weights with

    increments of 20g from 20g to 200g for the chassis with a roof and to 100g for the convertible

    chassis. This is because the convertible chassis are not as rigid as the hard tops therefore we could

    risk causing permanent damage to them which would give other groups a disadvantage.

    The reason why we are testing two types of hard top is so that with the results we gain, we will be

    able to see that how much effect the windscreen has on the overall rigidity of the chassis. The

    windscreen holds in the two pillars that connect the front bulk head to the roof, therefore there is

    rigidity to be gained in that area when designing a hard top. However we focused on the results of

    the convertible chassis so that we could see where the flexing occurs and the areas of where we can

    make the most improvements to the chassis.

    Figure 1- The Rig side view

    This is the side view of the rig. We can see that

    the back is back is unable to move and the front

    is on the pivot.

    This is where the weights are

    added.

    Figure 2-The Rig front view

    From the front view we can see wherethe measurements are taken from. To

    get the measurement of deflection first

    we need to measure the height the bar

    is from the table before any weight is

    added. We then zero the vernier

    calliper and every time weight is added

    record the measurement that is given.

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    Weight (g) Height (mm) Change in distance Degrees Torque

    0 46.73 0.00 0

    20 47.23 0.50 0.29 0.04

    40 47.54 0.81 0.46 0.08

    60 48.18 1.45 0.83 0.12

    80 48.58 1.85 1.06 0.16

    100 49.12 2.39 1.37 0.20

    120 49.33 2.60 1.49 0.24

    140 49.64 2.91 1.67 0.27

    160 49.99 3.26 1.87 0.31

    180 50.07 3.34 1.91 0.35

    200 50.62 3.89 2.23 0.39

    0.168Torsional Rigidity

    Weight (g) Height (mm) Change in distance Degrees Torque

    0 46.80 0 0

    20 47.29 0.49 0.28 0.04

    40 48.14 1.34 0.77 0.08

    60 48.79 1.99 1.14 0.12

    80 49.29 2.49 1.43 0.16

    100 49.96 3.16 1.81 0.20

    120 50.64 3.84 2.20 0.24

    140 51.63 4.83 2.77 0.27

    160 52.03 5.23 2.99 0.31

    180 52.56 5.76 3.30 0.35

    200 52.99 6.19 3.54 0.39

    0.106703Average Torsional Rigidity

    ResultsOnce we had made all of the improvements to the car we had to test them on the rig. And with

    these results we put them into a graph and from this we can work out the torsional rigidity. The

    equation to work out torque is:

    Where M is the mass of the load, G is acceleration due to gravity and R is the radius of the load arm

    and the radius of the measurement arm.

    To work out the degrees the equation is:

    We then make a graph with these figures. Torque is along thex-axis, and degrees along the y-axis

    The results are as follows:

    Table 2

    Table 1

    Table 1 is the full chassis.

    Table 2 is the windowless chassis.

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    Table 3

    Table 4

    Weight (g) Height (mm) Change in distance Degrees Torque

    0 48.38 0 0

    20 51.21 2.83 1.62 0.04

    40 53.71 5.33 3.05 0.0860 56.28 7.90 4.52 0.12

    80 57.99 9.61 5.49 0.16

    100 60.18 11.80 6.73 0.20

    0.028073Average Torsional Rigidity

    Weight (g) Height (mm) Change in distance Degrees Torque

    0 42.2 0 0

    20 43.52 1.32 0.76 0.04

    30 44.2 2 1.15 0.06

    40 44.61 2.41 1.38 0.08

    50 44.85 2.65 1.52 0.10

    60 45.36 3.16 1.81 0.12

    70 46.14 3.94 2.26 0.14

    80 47.02 4.82 2.76 0.16

    90 47.78 5.58 3.19 0.18

    100 48.25 6.05 3.46 0.20

    0.057884Average Torsional Rigidity

    Table 3 is the convertible chassis

    Table 4 is the groups chassis.

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    Table 5

    Weight (g) Height (mm) Change in distance Degrees Torque

    0 49.42 0 0

    20 49.68 0.26 0.15 0.04

    30 50.05 0.63 0.36 0.0640 50.22 0.8 0.46 0.08

    50 50.6 1.18 0.68 0.10

    60 50.85 1.43 0.82 0.12

    70 51.45 2.03 1.16 0.14

    80 51.88 2.46 1.41 0.16

    90 52.22 2.8 1.60 0.18

    100 53.01 3.59 2.06 0.20

    110 53.34 3.92 2.24 0.22

    120 53.68 4.26 2.44 0.24

    130 54.25 4.83 2.77 0.26

    140 54.57 5.15 2.95 0.27

    150 55.07 5.65 3.23 0.29

    160 55.4 5.98 3.42 0.31

    170 55.83 6.41 3.67 0.33

    180 56.51 7.09 4.06 0.35

    190 57.05 7.63 4.36 0.37

    200 57.33 7.91 4.52 0.39

    0.092421Average Torsional Rigidity

    Graph 1

    Table 5 is the unlimited chassis.

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    From graph 1 we can see that the full chassis is the strongest, this is because it has the roof and the

    windscreen for the extra rigidity. To work out the torsional rigidity you use the equation that is given

    from the graph and divide it by 1, this gives you the amount ofnewtons of mass is needed to move

    the chassis 1 degree. For the full chassis this figure is at 0.168 Nm/Deg and when you take the

    windscreen out, this figure goes down to 0.107 Nm/Deg, and when you make the chassis into a

    convertible this figure goes down to 0.028 Nm/Deg.

    The difference between the full chassis and the windowless chassis is 0.062 Nm/Deg. This is a large

    amount of rigidity to lose in a chassis. By losing the front windscreen the front is less rigid because

    there is nothing to hold the roof and A-pillars straight.

    Our target for our chassis was to be within 75% of the torsional rigidity of the full chassis, this gave

    us a target of 0.126 Nm/Deg. Unfortunately our chassis did not reach this target; the card chassis

    torsional rigidity was 0.058 NM/Deg which was 0.068 NM/Deg off. The unlimited chassis torsional

    rigidity was 0.092 Nm/Deg. This was 0.034 Nm/Deg off the target of 0.126 Nm/Deg.

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    ConclusionTo conclude the windscreen in a chassis has a large effect on how the chassis changes. With the

    windscreen in the chassis was only flexing at the rear, whereas when it was taken out the chassis

    was flexing at the front a rear and more significantly down the middle.

    For the convertible chassis there was flexing all over the floor which gave us a lot of scope to

    improve. All of the additions we made in improving the chassis made some difference in the rigidity

    of the chassis. However they still did not reach the 75% target that was set out. This is because we

    were close to the weight limit and did not want to go over it. Also for the card model we had no

    reference to go off therefore had no idea how the improvements we had done will do. This is why

    the card model was less than what was expected. However we could use what we had learned to

    improve the unlimited model. For example to put more emphasis on the transmission tunnel and

    lower on the front bulkhead and less high up on the bulk head as this has less effect on the rigidity.

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    ReferencesSmout, C. (2012) Chassis assignment, CE-00411-5 [Hnadouts] Transport Technology Chassis

    Assignment. 30th

    October 2012. Transport Technology. Staffordshire University, faculty of computing

    and engineering technology. Carlow Court, 13/12/2012