WPV Reprot Section 5 & 6

8/12/2019 WPV Reprot Section 5 & 6

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5. Performance Evaluation and Discussion

Before making a decision on the final design of our wind-powered vehicle (WPV) we

utilised the various blades and hubs we had designed by testing the WPV using the

blades in various arrangements. We tested the WPV using initially the PVC blades

attached to a Perspex hub, then attaching them to a wooden hub before implementingour pinwheel design. We also adjusted the arrangement of our blades such as trying

the blades out the front of the WPV and also testing the blades by position them in the

middle of the WPV. Another factor we took into consideration for out testing was the

use of two blades, this included using two pinwheels or mixing the PVC blades and

the pinwheel, trying them in various arrangements.

5.1 Analysis, testing and evaluation

Design 1:PVC blades with Perspex hub

The first design we tested utilised 6 PVC blades, which were position strategically

around a Perspex hub. The blades were placed on the Perspex hub by using 6 u-

clamps that allowed us to adjust the angle of the blades. The blades were turned on an

angle in a way, which allowed them to capture the greatest amount of wind as seen in

figure 1. A single pulley system was utilised in this design.

Table 1: PVC blades with Perspex hub

The results from table 1 clearly indicate that the design using PVC blades with a

Perspex hub is rather ineffective in achieving a mass-time ratio of 800g/s or greater.

The weight of the Perspex hub and blades together was quite heavy and the start up

time for the blades to start turning quickly was quite long, making it unproductive.

Figure 1:PVC blades with Perspex hub

Mass (g) Time (s) Mass/Time (g/s)

4000 15.1 265

7000 22.3 314

10000 32.8 305


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Design 2: PVC blades with wooden hub

The second design implemented a wooden hub with 6 PVC blades, with holes drilled

around the outside of the hub in which to place the blades as seen in figure 2. The

blades were still able to be rotated which allowed us to adjust the angle, in order to

capture the greatest amount of wind. A single pulley system was utilised in thisdesign.

Table 2: PVC blades with wooden hub

After analysing the results in table 2 it was apparent that changing the hub didnt

improve our results from table 1, in fact they had become worse. The excessiveweight of the PVC blades was creating a problem making the design unsuccessful in

achieving a mass-time ratio of 800g/s or greater.

Figure 2: PVC blades with wooden hub


4000 14.6 274

7000 23.8 294

10000 33.5 299


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Design 3: Pinwheel placed at the middle of WPV

In order to increase our mass-time ratio we decided to use lighter blades made out of a

different material and use a different design all together. We implemented a pinwheel

design using cardboard, with aluminium strips placed along the edges in order to

make the structure more rigid. Initially we placed the pinwheel in the middle of theWPV to investigate whether an equal distribution of weight across the WPV would

make an impact on our mass-time ratio. A single pulley system was utilised in this

design.

Table 3: Pinwheel placed at the middle of WPV

Mass (g) Time 1 (s) Time 2 (s) Time 3 (s) Time 4 (s) Mean

time (s)

Mass/Time

(g/s)

4000 12.8 12.5 13.1 12.9 12.825 312

7000 14.5 15 14.9 15.2 14.9 470

10000 17.5 15.5 14.5 16 15.875 63012000 15.7 16.8 17 15 16.125 744

13500 19.7 18.9 19.2 20 19.45 694

The results from table 3 clearly demonstrate a vast improvement on the PVC blades.

Through the use of a lighter material our initial the start up time for the blades to start

turning quickly was quite short, making it rather productive. The fact that the

pinwheel covered a larger surface area than the PVC blades allowed it to trap more

air, in order to move a lot faster. However we were only able to achieve the mass-time

ration of 800g/s just once, instead consistently averaging between 600-700g/s.


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Design 4: Pinwheel placed at the middle of WPV and front of WPV

To improve on our previous design we decided to use two pinwheels instead of one as

we calculated that implementing two blades would assist in increasing the speed of

WPV whilst carrying a large weight as seen in figure 3. Both pinwheels were madeout of cardboard with aluminium strips to reinforce the cardboard as well as provide

some extra mass in order to make the start up speed of the blades a lot quicker. Also

when using two blades we made use of a two pulley system.

Table 4: Pinwheel placed at the middle of WPV and front of WPV

After analysing the results in table 4 it was apparent that adding an additional

pinwheel didnt improve our results from table 3. The major problem with the design

was that the front pinwheel was trapping most of the wind, meaning the pinwheel

behind it only trapped minimal air. This resulted in the second pinwheel simply

become extra, unnecessary weight, making the design ineffective in achieving a mass-

time ratio of 800g/s or greater.

Figure 3: Pinwheel placed at the middle of WPV and front of WPV


7000 13.3 526

10000 16.7 599

12000 19.9 603


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Design 5: Pinwheel placed at the middle of WPV and wooden hub with PVC blades at

front of WPV

In order to increase our mass-time ratio we decided to maintain our two blade design

however we combined the PVC blades that were attached to a wooden hub and the

pinwheel. The PVC blades attached to a wooden hub were positioned at the front ofthe WPV allowing for some air to travel to the pinwheel behind it, positioned in the

middle of the WPV. The PVC blades were positioned at an angle to allow for

maximum air to be trapped. A two pulley system was maintained for the design.

Table 5: Pinwheel placed at the middle of WPV and wooden hub with PVC blades at

front of WPV

The results from table 5 again demonstrate there was hardly an improvement in our

results when compared to the previous designs. The initial start up time for the PVC

blades to start turning was too long, hence reducing our mass-time ratio.

Design 6: Pinwheel placed at the middle of WPV and Perspex hub with PVC blades at

front of WPV

In order to improve our results we decided to continue with our two blade design

however we decided to see if using a Perspex hub with PVC blades at front and a

pinwheel in the middle would have any impact on our results. A two pulley system

was maintained for the design

Table 6: Pinwheel placed at the middle of WPV and Perspex hub with PVC blades at

front of WPV

After analysing the results in table 6 it was evident that using a Perspex hub instead of

a wooden hub made no impact, with the PVC blades being heavy and ineffective. We

were unsuccessful in achieve the mass-time ration of 800g/s or greater.


10000 17.7 565

12000 21.6 632


12000 25.6 469

12500 24.8 504


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Design 7: Pinwheel placed at the front of WPV

To improve our results we decided to revert back to using a single pinwheel at the

front of the WPV, with a single pulley system being utilised, simplifying the design of

our WPV. The pinwheel was made from cardboard with aluminium strips placed

along the edges to add more mass to help the initial turn of the pinwheel as well asreinforce the structure of the pinwheel. The pinwheel was placed at the front of the

WPV to allow for maximum air to be trapped hence increasing the velocity of the

vehicle as seen in figure 4. The pulley system was positioned on the driving wheels of

the vehicle to increase the torque.

Table 7: Pinwheel placed at the front of WPV

Mass (g) Time 1 (s) Time 2 (s) Time 3 (s) Time 4 (s) Mean

time (s)

Mass/Time

(g/s)

11000 15.8 14.7 16.7 15.2 15.6 705

12000 17.5 16.4 17.9 18.1 17.475 68713000 19.1 15.1 16.5 17.3 17 765

13500 17.6 18.9 19.2 17 18.175 743

15000 24.3 22.5 23.6 25.2 23.9 628

The results from table 7 clearly demonstrate that placing the pinwheel at the font of

the WPV is our best option. We were able to achieve our best mass-time ratio of

861g/s, however we were unable to replicate the result. We were able to consistently

achieve a mass-time ratio between 700-800g/s when there was a payload of 13kg on

the vehicle, showing that having the pinwheel at the front of the WPV is our best

design option.

Figure 4: Pinwheel placed at the front of WPV


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5.2 Modification, redesign and rebuild

In order to determine which of our seven designs would be the most effective in

transporting a payload over two meters and achieve a mass-time ratio of 800g/s or

greater, we decided to create a graph of mass-time ratio versus payload, based on all

the seven results from our testing. The graph would then allow us to compare whichprototype had the highest mass-time ratio and had the most consistent results.

Figure 5: Graph of mass/time vs mass, comparing all 7 designs

After analysing the graph in figure 5 we were able to see that the pinwheel design

placed at the front of the WPV was evidently our best WPV design. Through the use

of a lighter material our initial the start up time for the blades to start turning quickly

was quite short, making it rather productive. The fact the pinwheel was at the front

and had a large surface area allowed it to trap more air, allowing the WPV to move a

lot faster.

Based on this information we modified our vehicle by eliminating the PVC blades all

together, instead preferring to use the pinwheel. We also decided to implement a

single pinwheel system rather than combing PVC blades with the pinwheel or using

two pinwheels. We rebuilt our vehicle by adding a pulley on the driving wheel in

order to provide greater torque and allow the vehicle to move a lot faster.

After redesigning then modifying and rebuilding our WPV we were left with our end

design that utilised a pinwheel at the front of the WPV and a single pulley system on

the driving wheels as seen in figure 4.


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6. Conclusion

In the final design of our WPV we decided to implement a pinwheel at the front of the

vehicle, four wheels and a single pulley system that used a string as it didnt requireany lubrication and provide a high mechanical efficiency. The overall weight of the

vehicle was 1.8kg with the lightness helping the WPV to move faster. The initial start

up time for the blades was rather quick, making it productive. The fact the pinwheel

was at the front and had a large surface area allowed it to trap more air, allowing the

WPV to move a lot faster. The pinwheel was made from cardboard with aluminium

strips placed along the edges to add more mass to help the initial turn of the pinwheel

as well as reinforce the structure of the pinwheel.

In the offical run of our vehicle our best mass-time ratio was 679g/s which was a

disapoinemnt compared to our test runs.

Table 8: Official Run using final design

After analysing these results and comparing them to our trail runs, we were able to

determine that the results we received were similar to what we had expected with

670g/s close to our averages of 700g/s.

In summation, our final design for our WPV was effective in achieving a mass-time

ratio of approximately 700g/s. Despite this we were unable to achieve the ideal mass-

time ratio of 800g/s making our WPV relatively ineffective in meeting the criteria,

however it was still able to achieve a mass-time ratio greater than 2g/s and travel 2m

comfortably. The mechatronics component of our WPV worked accurately and

effectively, as the binary counter was able to calculate the distance travelled correctly.


13200 19.44 679

11600 19.05 609

Documents

WPV Reprot Section 5 & 6