L1 Save Energy

(Sand Rigs)

ES185L1 First Year Laboratory

Denys Ilyushenko

University of Warwick

School of Engineering

2

Abstract

The aim for this experiment was to analyse energy loses within a

conveyor belt system and to explore methods of improving its efficiency. The

secondary objective of this laboratory experiment was to develop an

understanding of measurement of torque, speed and power.

The laboratory involved regulating the speed of a conveyor belt and

applying various loads to it, in a form of sand bags, in order to observe the

time taken for the belt to move the load through a specified distance. During

the experiment measurements of current, power, angular speed and force on

the spring were taken.

From the analysis, a conclusion was made that the system should be

operated at mid to high speeds for heavier loads. The heavier the load,

however, the slower the speed should be.

3

Table of contents:

Introduction 4

Theory 4

Apparatus and Method 5

Observation and Results 7

Analysis of Results and Uncertainties 10

Discussion 12

Conclusion 13

4

Introduction:

The laboratory investigates the power losses in a conveyor system and

encourages students to suggest revised methods of operating the apparatus

more efficiently.

The purpose of this lab was to increase our understanding of energy loss

analysis and to portray the importance of efficiency in simple systems.

Students were shown in reality how much loss a system like conveyor belt can

make.

Background information can be found in the laboratory briefing sheet,

provided by the ESO, which provides a basic information on how the lab should

be run and the measurements necessary to take.

For the required calculations and analysis of data, basic knowledge of

electricity and mechanics is necessary. John OMalleys Basic Circuit Analysis

and J.F. Collingwoods Mechanics, Structures and Thermodynamics, Volume 2,

will be a good source of this knowledge.

Numerous readings were taken during the experiment with varying

speeds and loads. And corresponding calculations completed to reach a

conclusion.

Theory:

There are 2 types of energy losses in this system. Fixed loss occurs when

the machine is on but is not doing any useful work. These losses occur due to

various factors in the system such as friction in the gears and bearings, power

consumed to operate the instruments themselves and other.

Variable losses occur when the machine is doing useful work. These

usually vary with the load that is put onto the system as well as the speed at

which it operates.

Peter ThomasSticky NoteNice to flag up the background reading!However, the formal style of citing is not quite right.... You should have usedsomething like:".... a good source for ... is O'Malley (20xx) ..." and then add details for reference at end of report in a separate References section.

5

First calculation necessary to do after a set of results is obtained is to

calculate the mechanical power delivered to the conveyor for each setting. For

this an equation can be used:

= (1)

where P is the mechanical power supplied to the system, T is the torque in

Newton-metres and is shaft speed in rad/s.

Torque acting on the system can be found using the following equation:

= 0.13 ( 0) (2)

where T is the torque acting, 0.13 is the radius of the shaft, F is the force

measured with load applied and 0 is the force measured without any load

applied.

Speed has to be in rad/s, therefore a formula can be used to convert

r.p.m. to rad/s:

= 2

60 (3)

Where n is speed in rpm.

Therefore, the final formula for finding mechanical power input from the

motor is:

= [0.13 ( 0)] 2

60

Apparatus and Method:

Apparatus:

A conveyor belt is set up on a

metal rack (1,9) which allows

the angle of the conveyor to be

changed. It is a 0.96m long and

lifts the load through a vertical

height of 0.25m. The belt is

operated by an electric motor

(7,8), which is a small DC

machine, it is attached to a

Peter ThomasSticky NoteYou need to draw attention to which component is shown on which photograph otherwise reader cannot follow...I am not sure what I am looking at!?Also all figures need figure numbers and captions...

6

gearbox (5,8). The gearbox provides a speed reduction of 30:1. For the purpose

of this exercise, the gearbox has a 1:1 ratio. The motor is held in place by a

spring (also shown in 1) which measures the force required to hold the motor

in place. The motor is operated by a speed regulator (6,9), which is connected

to the a.c. mains through a transformer, there is also a safety interlock (4,9)

which can stop the apparatus in case of an emergency. The power used by the

apparatus is shown on the screen of a wattmeter (3,9), which also measures

voltage and current. The load to the system is applied by putting 2kg sand bags

(2) on the conveyor belt.

Method:

Safety Interlock was turned on (green button), this increased the reading

on the wattmeter due to the circuit inside the interlock using some power. The

on button on the speed controller was then pressed, which also increased the

reading even further. The controller was then increased to setting 2, which

made the motor drive the conveyor belt. Required measurements were made.

The speed was the increased incrementally to setting 4,6,8, and 10

measurements were taken for each setting.

The experiment was then repeated with one sand bag (2kg) of load

applied to the belt. The measurements were taken some time after the release

in order to allow the system to stabilise. The only measurement to be taken

throughout the experiment was the time taken for the load to reach the top.

This experiment was carried out at each speed setting and was repeated

again in order to minimise errors. This was also done to 2 bad and 3 bag loads.

Peter ThomasSticky NoteI don't know what I am looking at...You haven't expalined what is shown here...

Peter ThomasSticky NoteI am not really interested in which buttons you pressed and what colour they had! ... I only want to know about the important processes relating to the experiment.

Peter ThomasSticky NoteAnd what does 'setting 2' supposed to mean to me? I have never seen the experiment...

7

Observations and Results:

Power taken by the safety interlock = 2.47 Watts

Power taken by the safety interlock and motor controller = 2.40 Watts

0 = 9N

When no load was applied to the system, the following results were obtained:

Speed Setting

Current (Amps)

Power (watts)

Speed (rpm)

Speed (rad/s)

Force (N)

Torque Mech Power

2.00 0.27 3.00 24.00 2.51 9.40 0.05 0.13

4.00 0.32 3.80 43.80 4.58 10.00 0.13 0.60

6.00 0.38 4.85 69.20 7.24 11.00 0.26 1.88

8.00 0.40 5.60 88.10 9.22 11.00 0.26 2.40

10.00 0.40 6.00 102.10 10.69 11.00 0.26 2.78

Table 1 table of results with no load applied

Fig.1 Variation of Electrical and Mechanical Power with speed (no load)

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0.00 20.00 40.00 60.00 80.00 100.00 120.00

Mec

han

ical

Po

wer

(w

atts

)

Elec

tric

al In

pu

t p

ow

er (

Wat

ts)

Speed in rpm

Variation of Electrical and Mechanical Power with Speed (no load)

Electric Power Mechanical Power

Peter ThomasSticky NoteAm I suposed to decipher what is shown in the table myself? Sorry, no time for this! You need to tell me in brief words as guidance...

8

With 1 sandbag load (2kg) applied, the following results were obtained:

Speed Setting

1 Bag 2 4 6 8 10

Take 1

Take 2 Average

Take 1

Take 2 Average

Take 1

Take 2 Average

Take 1

Take 2 Average

Take 1

Take 2 Average

I (Amps) 0.38 0.38 0.38 0.44 0.46 0.45 0.51 0.53 0.52 0.51 0.51 0.51 0.54 0.55 0.55

Power (watts)

3.60 3.70 3.65 4.80 4.90 4.85 6.20 6.40 6.30 7.10 7.10 7.10 8.10 8.30 8.20

Speed (rpm) 21.80 21.80 21.80 38.60 38.60 38.60 63.50 63.50 63.50 83.20 83.60 83.40 96.80 97.10 96.95

Speed (rad/s)

2.28 4.04 6.65 8.73 10.15

Force (N) 14 13 14 15 15 15 15 15 15 15 15 15 15 15 15

Torque (Nm)

0.59 0.78 0.78 0.78 0.78

Mech Power (W)

1.33 3.15 5.18 6.81 7.91

Time taken (s)

10.20 10.00 10.10 5.70 5.60 5.65 3.60 3.50 3.55 2.60 2.60 2.60 2.30 2.50 2.40

Table 2 table of results with 2 kg load

Fig.2 - Variation of Electrical and Mechanical Power with speed (2kg load)

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

0.00 20.00 40.00 60.00 80.00 100.00 120.00M

ech

anic

al P

ow

er (

Wat

ts)

Elec

tric

al In

pu

t P

ow

er (

Wat

ts)

Speed in rpm

Variation of Electrical and Mechanical Powers with speed (1 bag load)

Electrical Power Mechanical Power

9

With 2 sandbags (4kg) load applied, the following results were obtained:

Speed Setting

2 Bags 2 4 6 8 10

Take 1

Take 2 Average

Take 1

Take 2 Average

Take 1

Take 2 Average

Take 1

Take 2 Average

Take 1

Take 2 Average

I (Amps) 0.41 0.43 0.42 0.53 0.52 0.53 0.63 0.61 0.62 0.70 0.73 0.72 0.81 0.76 0.79

Power (watts) 4.10 4.20 4.15 5.60 5.40 5.50 7.30 7.30 7.30 9.50 10.20 9.85 11.10 11.10 11.10

Speed (rpm) 17.70 17.40 17.55 35.30 35.20 35.25 70.10 70.20 70.15 83.10 82.60 82.85 92.70 92.30 92.50

Speed (rad/s) 1.84 3.69 7.34 8.67 9.68

Force (N) 17 17 17 17 18 18 18 17 18 18 19 19 20 20 20

Torque (Nm) 1.04 1.11 1.11 1.24 1.43

Mech Power (W)

1.91 4.08 8.11 10.71 13.84

Time taken (s) 11.50 12.00 11.75 6.10 6.50 6.30 3.50 3.50 3.50 2.90 3.20 3.05 2.30 2.30 2.30

Table 3 - table of results with 4 kg load

Fig. 3 -

Variation of

Electrical

and

Mechanical

Power with

speed (4kg

load)

With 3 sandbags (6kg) load applied, the following results were obtained:

Speed Setting

3 Bags

2 4 6 8 10

Take 1

Take 2

Average

Take 1

Take 2

Average

Take 1

Take 2

Average

Take 1

Take 2

Average

Take 1

Take 2

Average

I (Amps) 0.59 0.60 0.60 0.73 0.73 0.73 0.81 0.88 0.85 0.95 0.86 0.91 0.87 0.89 0.88

Power (watts)

5.50 5.60 5.55 7.50 7.50 7.50 9.90 11.1

0 10.50

11.30

12.30

11.80 13.9

0 13.4

0 13.65

Speed (rpm) 13.3

0 12.9

0 13.10

28.00

28.40

28.20 53.0

0 53.1

0 53.05

78.10

77.60

77.85 92.9

0 93.0

0 92.95

Speed (rad/s)

1.37 2.95 5.55 8.15 9.73

Force (N) 22 21 22 22 22 22 23 22 23 23 24 24 24 23 24

Torque (Nm)

1.63 1.69 1.76 1.89 1.89

Mech Power (W)

2.23 4.99 9.74 15.36 18.34

Time taken (s)

15.00

15.90

15.45 7.50 7.30 7.40 4.30 4.00 4.15 3.10 3.00 3.05 2.40 2.70 2.55

Table 4 - table of results with 6 kg load

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

0.00 20.00 40.00 60.00 80.00 100.00 Mec

han

ical

Po

wer

(W

atts

)

Elec

tric

al P

ow

er (

Wat

ts)

Speed in rpm

Variation of Electrical and Mechanical Power with Speed (2 bags load)

Electrical Power Mechanical Power

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Fig. 4 - Variation of Electrical and Mechanical Power with speed (6kg load)

Analysis and Uncertainties:

From the experiment, it is clear that the safety interlock is consuming a

significant 2.47 watts. When the motor was switched off, the consumption fell.

I was not able to find any reason why that could be the case, therefore, I

assume, that the fall in power consumption from 2.47 to 2.40 is nothing else,

but an error. At the time of the experiment, it was not clear that the error was

made and therefore no action was taken to prevent it.

When no load was applied (Fig 1), the increase in speed and mechanical

power output means a certain increase in amount of energy consumed. The

lines are almost identical and parallel, suggesting an equal increase in the

values, perfect correlation.

However, different relationship is observed as the load is applied. Fig. 2

shows that the amount of mechanical power supplied increased at a much

greater rate than the power consumed.

This is also confirmed by Fig.3. When 4kg of load were applied, the

relationship changed a lot. Increasing the speed increased the electric power

input in the same way as before, however, amount of mechanical power

supplied to the belt increased dramatically. From the graph, it is clear that

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00

Mec

han

ical

Po

wer

(W

atts

)

Elec

tric

al P

ow

er (

Wat

ts)

Speed in rpm

Variation of Electrical and Mechanical Power with speed (3 bags load)

Electrical Power Mechanical Power

Peter ThomasSticky NoteOK... I have seen various graphs in Figs 1-4 but I don't know what the show... You haven't mentioned this to me...And I don't feel like trying to reason myself what is what...

Peter ThomasSticky NoteIt is not clear to me!? You haven't explained it to me... I cannot follow....

Peter ThomasSticky NoteAha, here comes first hint at what is shown in figures... But this comes a bit late...

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after 70 rpm, the motor started giving comparatively more mechanical power

that it was using electrical power.

Fig. 4 portrays a similar, but more extreme relationship. The motor

started giving off more power at 50rpm.

This suggests that for light loads and slower speeds, the motor

consumes more power than it gives off, making it very inefficient. Lighter loads

should be raised at high speeds to improve efficiency.

When a load of 4 kilograms is applied, the load should be lifted at 70

rpm to break even with the consumption and lift. Faster speed would mean

faster lift, but at the same time, increased power consumption. Therefore the

optimal speed to lift 4 kg load is 70rpm.

Loads of 6kg have a similar principal as 4 kg loads, except of the fact that

the consumption breaks even at a lower speed, around 50rpm. Once again,

faster speed would mean that the work will be done quicker, but is not

necessary.

In all the graphs (figures 1,2,3 and 4), if the lines for an electrical input

power are extended backwards, it crosses the Y-axis. This suggests that even

when the motor is not operational there are still losses to the power. This is

due to the Safety interlock circuit consuming part of it to operate normally.

Uncertainties:

As with any experiment, several factors could have affected the result.

One of the biggest sources of errors is the precision of the instruments used.

And although all the care was taken to minimise the uncertainties, they were

still present.

The table below summarises some measurements and the according

uncertainties. When a range of value was present, the uncertainty was given as

half of the largest range.

Measurement Instrument Uncertainty

Current Wattmeter 0.05

Power Wattmeter 0.05

Speed Tachometer 0.02

Force Spring 1

Time Stopwatch 1

Peter ThomasSticky NoteWhere 'below'? I don't know which table you are referring to... Use: "Table x shows...."Where is your table number and caption?

12

The uncertainties in this experiment were fairly significant. This was

clearer during high speed experiments. Sometimes the load would be

propelled upwards faster than the stabilisation period of the tachometer. In

this case, the experiment was repeated several times and the average value

was taken.

When operating a stopwatch, it was very important to pay attention to

the load as precise timing was necessary. The person operating a stopwatch

was also closely monitoring the person who places load onto the conveyor.

This was done in order to start the stopwatch at exact moment the load is

applied at.

Spring has also had a stabilisation period. At first it would fluctuate due

to the load being applied unexpectedly. At slower experiments, the readings

were not taken until the whole system was stable. At faster experiments, the

experiment was repeated and an average value was taken.

Current and Power measurements were the easiest to take as they did

not fluctuate much. The instrument was quick and precise.

Discussion:

Practically, the experiment was a fair challenge to conduct. Coordination

and concentration were both needed to conduct this experiment correctly.

This has potentially increased the possibility of an error. Reduction to this error

was made by repeating the experiment number of times.

The speed dial was not a continuous dial (only certain positions were

possible, as the knob would click into place) reducing the chance of human

error. It was not possible to put the speed setting to, for example, 2.5.

On the other hand, the experiment required students to use a

tachometer. Majority of students were not familiar on how to use it and

therefore had to be trained. In addition to this, it required a good connection

between the rotating shaft and the instruments sensor. Any movements of

the hand while measuring the speed would of ruined the result. However, in

most cases, the operation of the instrument was good.

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Regardless of the errors, the experiment provided enough data for the

correlations to be observed and conclusion to be drawn. Looking the figures 1-

4, the points are close to the line of best fit, which suggests absence of

anomalous results.

Conclusion:

All the data was close to the line of best fit, with tiny deviations,

suggesting that the experiment went well. Main source of power loss is the

safety interlock, losing almost 2.4 watts of power. And the most efficient way

to operate the belt is at or beyond the point at which the lies cross.

14

Bibliography

John OMalley. Basic Circuit Analysis. Second Edition. 2014

J.F. Collingwood, D.G. Chetwynd and R.E. Critoph. Mechanics,

Structures and Thermodynamics. Volume 2. 2014

Peter ThomasSticky NoteI cannot find these books! You didn't provide me with enough information to find them.... Who is publisher?