sam lindop l018852a transport technology technical report
TRANSCRIPT
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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