december 14, 2012 joshua matthews, chief engineer m-fly …€¦ · december 14, 2012 joshua...

1320 Beal Ave

Ann Arbor, MI 48109

(269) 762-0546

December 14, 2012

Joshua Matthews, Chief Engineer

M-Fly

Wilson Student Project Center

2603 Draper Ave

Ann Arbor, MI 48109

Subject: Final Report transmittal for study of Magnum XLS-61A motor dynamic thrust

Dear Mr. Matthews:

Enclosed is the final report for a study of the dynamic thrust profile of the breakthrough Magnum

XLS-61A motor.

This report includes results from the complete break-in of the Magnum XLS-61A motor and

wind tunnel testing of the motor with different attached propellers, as you requested. The team

successfully built a static stand to run the motor on and completed the break-in process for the

supplied motor. Thrust Unlimited was able to collect all the necessary data within the 2-hour

testing interval allotted. The previously-built thrust measurement stand and electronic

components worked well with the available data system. Also notable is that less than ¼ gallon

of fuel was consumed while testing the six propellers given to us. From the data collected, we

analyzed the thrust over various wind velocities for each of the propellers.

The team concludes that the Magnum motor with 12-inch diameter propeller and 7° pitch

produces the highest thrust at nearly all airspeeds. On average, the 12” x 7° propeller and

Magnum XLS motor produce two pounds more thrust than the previous year’s configuration of a

12” x 8° propeller coupled with the O.S. motor. Additionally, Thrust Unlimited was able to

complete the analysis and recommendations a week ahead of schedule and nearly on budget.

All of us at Thrust Unlimited would like to send our sincerest thanks for the support you

provided. We are grateful for your time spent answering our questions during break-in and wind

tunnel operation. We would also like to give our thanks for the fascinating tour of the M-Fly

design and test facility in the Wilson Student Project Center this past September. In closing, we

want to express our appreciation of the long-standing relationship our company has had with M-

Fly and are excited to work with your team on future endeavors.

Sincerely,

Duncan Miller (Project Manager) Justin Amara-Parent

Ben Brelje George Konecny

enc. Joseph Schafer

Final Report:

Dynamic Thrust Characterization of the Magnum

XLS-61A Motor for M-Fly Unmanned Air Vehicle

Final Report: Dynamic Thrust Characterization of the Magnum

XLS-61A Motor for M-Fly Unmanned Air Vehicle

December 14, 2012

Prepared by:

Thrust Unlimited

Benjamin Brelje

George Konecny

Duncan Miller

Justin Amara-Parent

Joseph Schafer

Prepared for:

M-Fly Student Design Team

Joshua Matthews (Chief Engineer)

Professor Martins (Advisor)

i

Table of Contents

List of Figures ................................................................................................................................. ii

List of Tables .................................................................................................................................. ii Executive Summary ........................................................................................................................ 1 1 Introduction .................................................................................................................................. 2

1.1 Details of Problem ................................................................................................................ 2

1.2 Summary of Task .................................................................................................................. 2

1.3 Benefits and Impact .............................................................................................................. 3

2 Assessment Criteria ..................................................................................................................... 3 2.1 Effectiveness —Maximum Static Thrust .............................................................................. 3

2.2 Feasibility —Improved Thrust Curve ................................................................................... 4

2.3 Desirability—Maximum Thrust Power ................................................................................ 4

3 Methods of Analysis .................................................................................................................... 4

3.1 Theoretical Background ........................................................................................................ 4

3.2 Experimental Methods .......................................................................................................... 5

3.2.1 Test Articles ................................................................................................................... 5

3.2.2 Facilities and equipment utilized ................................................................................... 6

3.2.3 Motor Break-In .............................................................................................................. 7

3.2.4 Wind Tunnel Testing ..................................................................................................... 8

3.3 Data Processing ..................................................................................................................... 9

4 Results ........................................................................................................................................ 10 4.1 Effectiveness—Maximum Static Thrust ............................................................................. 11

4.2 Feasible—Improved Thrust Curve ..................................................................................... 11

4.3 Desirability—Maximum Thrust Power .............................................................................. 12

5 Recommendation and Alternatives ............................................................................................ 13

6 Omissions and Limitations ........................................................................................................ 13 7 Cost Analysis ............................................................................................................................. 14 8 Schedule ..................................................................................................................................... 14 9 References .................................................................................................................................. 15

Appendix A: Engineering drawings............................................................................................. A1 Appendix B: Detailed Test Procedure .......................................................................................... B1

Appendix C: Calibrations Prior to Testing ................................................................................... C1 Appendix D: Project Management............................................................................................... D1 Appendix E: Raw Thrust Data ...................................................................................................... E1

ii

List of Figures

Figure 1: Existing M-Fly plane with O.S. motor installed ............................................................. 2 Figure 2: Expected dynamic thrust curve from propeller theory .................................................... 5

Figure 3: Test article comparision .................................................................................................. 6 Figure 4: Propeller candidates of two diameters (11” and 12”) and varying pitch ......................... 6 Figure 5: Instructional Subsonic Wind Tunnel testing schematic .................................................. 6 Figure 6: Thrust stand and equipment ............................................................................................ 7 Figure 7: Break-in stand design ...................................................................................................... 8

Figure 8: Full systems diagram of the thrust stand set-up .............................................................. 9 Figure 9: Raw thrust time series ..................................................................................................... 9 Figure 10: Thrust stand drag calibration ....................................................................................... 10 Figure 11: Dynamic thrust curve .................................................................................................. 11

Figure 12: Magnum XLS with 12" x 7° versus 2011 motor configuration .................................. 12 Figure 13: Dynamic thrust power ................................................................................................. 13

Figure 14: Calibration of force transducer .................................................................................... C1 Figure 15: Force transducer calibration ........................................................................................ C1

Figure 16: Wind tunnel calibration ............................................................................................... C2 Figure 17: Project plan ................................................................................................................. D1

List of Tables

Table 1: Summary of criteria in accepting the proposed motor .................................................... 11 Table 2: Performance to schedule ................................................................................................. 14

Table 3: Actual costs ..................................................................................................................... 15

Table 4: Project Gantt chart ......................................................................................................... D1

1

Executive Summary

A recent SAE Aero Design competition rule change allows teams to use a Magnum XLS motor

in replace of the standard O.S. motor. As a result, the M-Fly student project team at the

University of Michigan intends to optimize the performance of their motor-propeller

combination in order to predict and improve the maximum carrying capacity of their 2013

aircraft. Thrust Unlimited has responded to M-Fly’s request to “break-in” the Magnum motor

and test six different propellers in a 2- by 2-foot wind tunnel. M-Fly requires data for thrust and

thrust power over airspeeds ranging from 0-70 feet per second (fps)—their entire flight envelope.

Through wind tunnel testing, we have produced thrust data for six different propellers using the

Magnum XLS motor. This report will explain the details of the study as well as the outcomes and

conclusions.

After successfully completing a full dynamic thrust analysis, Thrust Unlimited recommends

installing the Magnum XLS motor and 12” x 7° propeller for the 2013 SAE Aero Design

competition. This propeller produced the highest static thrust of 10 pounds (lb), making it the

most effective candidate. Moreover, the thrust produced by this motor-propeller combination

surpasses the thrust from the O.S. motor currently installed on the M-Fly plane by at least 2 lbs

over all flight speeds. Since the lower-thrust O.S. motor has already proven adequate to power

the airplane for previous M-Fly plane designs, we know that the team’s recommendation of the

new, more powerful motor is feasible. The Magnum XLS motor with 12”x7° propeller is also

desirable because it produced the highest measured thrust power of all the propellers In

summary, we recommend the Magnum XLS motor and 12” x 7° motor-propeller combination

because it is a clear improvement from the O.S. motor configuration on all selection criteria.

2

1 Introduction

M-Fly has asked the engineering team Thrust Unlimited to characterize the dynamic thrust

characteristics of a new motor, the Magnum XLS-61A. In previous years, M-Fly used the O.S.

61 FX motor. However, the O.S. motor is no longer produced and the Magnum XLS-61A will

now be used in its place. This report presents the motivation, methods, and results of the break-in

and characterization of Magnum motor dynamic thrust. This report is organized into the

following sections: Assessment Criteria, Methods of Analysis, Results, Recommendations and

Alternatives, Omissions and Limitations, Cost and Schedule.

1.1 Details of Problem

The characterization of the Magnum XLS-61A motor is sponsored by the student design team,

M-Fly, which represents the University of Michigan at the SAE Aero Design Competition. Over

the past 10 years, competition requirements have required that the student-built planes be

powered by a single O.S. 61 FX motor. However, this specific motor model is no longer

produced; therefore, SAE has approved a motor with similar performance characteristics for use

in the competition: the Magnum XLS-61A.

Figure 1: Existing M-Fly plane with O.S. motor installed

Data for motor performance are used to predict the maximum payload capacity. Since a large

portion of the competition is judged on how well the vehicle’s predicted flight performance

matches actual performance during a flight demonstration, the data used in the prediction model

must be robust and accurate. The previous motor’s performance is very well known due to its

extensive flight heritage and previous testing; the new motor must now be similarly

characterized. By comparing the performance of the two engines, the team can also make a

decision about moving to the new motor in order to gain a possible competitive advantage. Based

on the dynamic thrust data, the best propeller-motor combination was chosen for use in the final

design.

1.2 Summary of Task

This year’s M-Fly team requires knowledge of dynamic thrust (thrust as a function of velocity)

as well as the optimal propeller design (diameter and pitch) for this new motor. This information

will aid in predicting maximum carrying capacity. Thrust Unlimited team members first

reviewed and analyzed past M-Fly data (from 2008 and 2009) and current aerodynamic designs.

Because the test article was a brand new motor, the motor was required to be “broken in” prior to

testing at full throttle. The team designed, built, and used a break-in stand to condition the new

Magnum motor. Once the motor was proven to operate in a safe and predictable manner and the

team’s start-up procedures were fine-tuned and demonstrated, we proceeded with wind tunnel

testing.

3

In the 2- by 2-foot wind tunnel, we measured thrust as a function of velocity for six different

propeller configurations. The team used results from the wind tunnel test to construct a thrust

profile of the Magnum motor for each test configuration, for comparison to the older OS Motor

performance. Our results indicate that the 12” x 7° propeller, combined with the new Magnum

XLS motor, is the optimal configuration for the 2013 M-Fly plane because it proved to be the

most effective, feasible, and desirable candidate.

1.3 Benefits and Impact

Thrust Unlimited’s wind tunnel testing, conducted on behalf of M-Fly, benefits the organization

in two main ways: increased productivity and better model accuracy.

The outcome of this project allowed the 30-40 students involved with this year’s M-Fly team to

be more productive. By outsourcing testing of the vehicle’s power plant, team members instead

focused on the design factors they directly control, such as aerodynamics and structural design.

Allowing Thrust Unlimited to handle the motor characterization and break-in ultimately frees up

members to work on more valuable tasks.

Thrust Unlimited is also helping M-Fly compete and win by providing the most accurate possible

thrust characterization. Our team provided access to the proprietary small-motor thrust stand

which enabled us to gather high-quality data. Accurate data on motor performance will allow M-

Fly to construct more accurate models to predict this year’s airplane payload carrying capability.

The thrust characterization may, in this way, lead directly to higher scores and a better overall

finish.

A byproduct of this study is a small break-in stand to be delivered to the team. This stand will be

beneficial to future teams, who may be required to use a different motor if the team chooses to

move to a different class of competition or in the case of another change in competition

requirements.

Furthermore, the study may have benefits for the hobbyist community at large if M-Fly should

choose to share the data. Little or no dynamic thrust data exists for the Magnum motor; therefore,

Thrust Unlimited’s data could be a valuable resource for hobbyists everywhere.

2 Assessment Criteria

We identified three criteria in order to gauge the performance of the Magnum XLS motor and the

six corresponding propellers. These criteria will quantify and support our recommendation. A

trade study of past M-Fly designs has provided benchmarks for thrust and thrust power.

Organized from most to least important these distinguishing criteria are: effectiveness,

feasibility, and desirability.

2.1 Effectiveness —Maximum Static Thrust

The most effective propeller will have the highest static thrust. This is a measure of the

maximum force generated by the motor. Higher static thrust causes the airplane to accelerate

more quickly from rest and takeoff in a shorter distance. Static thrust is the most important

criteria in judging the capabilities of the motor because the plane is required to lift off the

4

runway in a specified distance. A benchmark of 7 lbs static thrust has been drawn from the

previous M-Fly thrust testing.

2.2 Feasibility —Improved Thrust Curve

Our second ranked criterion, feasibility, is judged on the degree of improvement compared to the

2011 configuration. A feasible motor-propeller combination will have a dynamic thrust equal to

or greater than the O.S. Motor and 12” x 8° propeller previously used. This ensures that the plane

will have sufficient thrust capability throughout the entire flight envelope.

2.3 Desirability—Maximum Thrust Power

Finally, the most desirable propeller will extract the most power from the fuel relative to the

other propellers, over the expected flight speeds. With a constant throttle setting of 100%, this

becomes a measure of the efficiency of the candidate motor-propeller combination. Our

benchmark is the maximum thrust power measured from last year’s plane—0.3 horsepower (hp).

3 Methods of Analysis

Propeller theory can provide an order of magnitude estimate of motor performance, given motor

characteristics (stroke length, displacement volume, fuel energy density) and propeller diameter,

twist and taper. However, historically, it has been relatively cheap and straightforward to

evaluate and corroborate motor performance experimentally. Moreover, experimental testing

data is looked on favorably by the SAE Aero Design competition. Thus, the theory has been used

to substantiate results, but our recommendations are based on the testing conducted as follows.

3.1 Theoretical Background

The basis for dynamic thrust characterization is the actuator disc model of propellers.

Conservation of energy dictates that thrust power, or propulsive power imparted to the free

stream, depends on the flight speed. For a motor of fixed power (such as a simplified internal

combustion motor like the Magnum motor), the thrust of the motor depends inversely on the

forward velocity, such that the thrust power equation is conserved (Equation 1)[1]

.

Equation 1

Where:

Psh = Shaft power

η = Propulsive efficiency

T = Thrust

U∞ = Free stream velocity

For a constant-power motor driving a simplified actuator disc propeller, the dynamic thrust curve

will look roughly like Figure 2, resembling an ax-1/2

power law with some offset from zero

velocity.

5

Figure 2: Expected dynamic thrust curve from propeller theory

Typically, propulsive efficiency peaks at about 80%, but it also depends on free stream velocity

(Equation 2).

Equation 2

As the induced velocity ue /u0 converges to 1, propulsive efficiency also approaches 100%. In

practice, this doesn’t happen because of frictional losses, and because thrust itself depends on the

induced velocity (Equation 3).

( )

( )

Equation 3

There is no way to explicitly solve for thrust, power, and efficiency using the actuator disc

theory, so empirical testing is relied on to choose optimal propeller-motor combinations.

3.2 Experimental Methods

The dynamic thrust testing was carried out in a wind tunnel so that the expected flight conditions

could be simulated. A motor is started and affixed to a load transducer within the wind tunnel

itself, to measure the thrust produced by the propeller. Then, the wind tunnel is turned on to a

known speed and the thrust produced by the motor is recorded. The post-processed result

resembles Figure 2.

3.2.1 Test Articles

The subject of this study is the Magnum XLS-61A hobbyist motor (Figure 3). The Magnum

XLS-61A is a 0.61 cubic inch displacement, two-stroke motor that was released to market in

2007. Documentation released by Magnum, specifically the owner’s manual, is freely available

0

0.2

0.4

0.6

0.8

1

1.2

2 4 6 8 10

No

rmal

ize

d T

hru

st

Velocity (Arbitrary Units)

Available thrust expected to

decrease with increased speed

6

online. However, since optimal propeller diameter, pitch and throttle vary based on the specific

part number and application, official thrust characterization curves relevant to M-Fly are lacking.

Along with the motor, several propellers were supplied by the sponsor for testing (Figure 4).

These propellers of varying diameter and pitch were tested to identify the best propeller selection

for M-Fly’s new aircraft design.

O.S. Motor

Magnum XLS Motor

Figure 3: Test article comparision

Figure 4: Propeller candidates of two diameters (11” and 12”) and varying pitch

3.2.2 Facilities and equipment utilized

In order to gather all of the needed data, Thrust Unlimited used the University of Michigan’s

instructional 2- by 2-foot subsonic wind tunnel, the student machine shop, and the expertise of

the department machinist, Terry Larrow. Figure 5 represents a schematic of the method of wind

tunnel dynamic thrust testing. The test article is installed on a thrust stand inside the wind tunnel

test section; the free stream simulating aircraft flight flows from left to right.

Figure 5: Instructional Subsonic Wind Tunnel testing schematic

7

The subsonic wind tunnel was chosen for the size of the test section as well as the flow speeds it

can produce. The wind tunnel can provide the low turbulence testing conditions required for

testing, capable of producing a maximum flow speed of 80 fps throughout the four-foot-long test

section, exceeding M-Fly’s test requirement of 70 fps maximum velocity. The test section

dimensions easily accommodate the test stand and maximum propeller diameter to be used

during testing of 12 inches. This ensures that the propeller will be operating in flow unaffected

by the tunnel wall’s boundary layer. Thrust Unlimited also used the student machine shop to

fabricate the break-in stand and fittings for a servo-actuated throttle linkage.

Thrust Unlimited utilized a variety of equipment and supplies to complete the study. This

equipment can be broken into two categories: operational and instrumentation equipment. The

glow plug, crank starter, and fuel are common supplies used by RC hobbyists to maintain and

operate small motors. The mounting bracket, servo, and transmitter were incorporated into

testing equipment to control the motor remotely and increase safety.

Instrumentation is required to measure force produced by the motor during testing. Mr. Larrow,

the department machinist, has allowed us to use his personal thrust stand for data collection

during wind tunnel testing. The equipment is available on a short-term loan from Mr. Larrow to

complete the study. Figure 6 is a photo of the complete thrust stand configuration with installed

instrumentation equipment.

The thrust stand incorporates a metal frame, a 25lb force transducer, an Omega Omni-Amp III

signal amplifier, and a LabJack analog-to-digital converter.

Figure 6: Thrust stand and equipment

The team also required a static mounting stand to “break-in” the motor prior to testing. Thrust

Unlimited designed and fabricated a simple stand to complete this task, as described in Section

3.2.3.

3.2.3 Motor Break-In

Before running at full throttle under test conditions, the Magnum motor needs be conditioned by

repetitive use for at least one hour. This “break-in” period is typical for small motors and is

8

needed every time a new motor is purchased. A stand was constructed from aluminum 6061

stock to hold the motor during the break in procedure. Figure 7 compares the break-in stand as

designed and as built and installed. Appendix A provides detailed orthographic views illustrating

the simple and robust structure.

As-designed

As-built

Figure 7: Break-in stand design

Step by step procedures for break-in can be found in Appendix B. After securing the motor to the

break-in stand and making sure all parts were assembled according to manufacturer’s

specifications, we connected the glow plug and fuel lines to the motor. After making sure the

motor and stand were locked in place, the motor was started. The inlet valve was positioned to

fully open to allow for maximum RPM and the motor was run for approximately one hour. No

motor problems were identified during break in and the motor was deemed ready for testing.

3.2.4 Wind Tunnel Testing

Thrust Unlimited measured the dynamic thrust of the Magnum XLS-61A motor on a precision,

one-axis thrust stand inside the 2- by 2-foot wind tunnel. Detailed test procedures can be found

in Appendix B, and the interfacing diagram is shown in Figure 8.

Prior to testing, using a near identical set-up procedure as break-in, the motor was instead bolted

to the thrust stand mounting plate. The team configured the data acquisition software and

calibrated the load cell in the thrust stand using hanging weights. Once a calibration series was

constructed, we bolted the thrust stand to the floor of the tunnel.

Next, the wind tunnel was started and force on the thrust stand was measured to account for drag

of the test equipment at a range of airspeeds. We then started the motor and closed the tunnel.

Thrust was measured at wind tunnel speeds from 0 to 70 fps by varying the wind tunnel speed

controller. After thrust data was recorded at a series of tunnel speeds, the tunnel and motor were

turned off and a new propeller installed. This process repeated for six different propeller test

articles.

9

Figure 8: Full systems diagram of the thrust stand set-up

3.3 Data Processing

Raw data from the load cell was sampled at 2 Hz and revealed a large degree of noise due to

mechanical vibration from operating the motor (Figure 9).

Figure 9: Raw thrust time series

In order to statistically account for the noise, a time-average was applied for all points

corresponding to a particular wind tunnel speed. Averaging results greatly reduced the

Ran

ge

of

nois

y d

ata

10

confidence interval of each measurement and allowed useful data to be extracted from a very

noisy signal.

Drag on the thrust stand was another concern. The thrust stand had a large, flat plate normal to

the wind direction, presenting an abnormal amount of pressure drag at low speed and causing

turbulent flows behind the stand at high speeds. In order to account for the drag of the stand, a

calibration curve of drag at a range of wind tunnel speeds was created (Figure 10). A curve fit

was applied to the data, and this curve fit was subtracted from subsequent thrust data in order to

account for drag forces.

Figure 10: Thrust stand drag calibration

4 Results

The results for most propellers indicated that the Magnum XLS motor produces similar or

greater thrust at full-throttle throughout the dynamic range than the O.S. motor previously used

by M-Fly. Thrust depends more on pitch than diameter, with low-pitch (6 or 7 degrees)

producing markedly higher thrust than high-pitch propellers (8 degrees or greater).

Based on analysis of the processed thrust data, the optimal propeller for the Magnum motor is

the 12” x 7°. At 10 lbs of static thrust this propeller produces almost two pounds more static

thrust than the high-pitch propellers, and maintains a similar advantage at high air speeds.

Magnitude of drag force

increases at higher

velocities

11

Table 1: Summary of criteria in accepting the proposed motor

Generic Criterion Effective Feasible Desirable

Figure of Merit Maximum Static

Thrust

Improved Thrust over

All Flow Velocities

Maximum Thrust

Power

Injector Performance 10 lbs >2 lbs more thrust

over the entire flight

envelope

0.33 hp

Benchmark (Industry

Standard)

7 lbs 0.3 hp

Result Pass Pass Pass

4.1 Effectiveness—Maximum Static Thrust

Figure 11 displays the thrust curves for all six propellers tested with the Magnum XLS motor.

The plot shows two main groups of propellers: a group of three high-performance, low –pitch

propellers (between 6° and 7° pitch angle) and a group of three high-pitch propellers with lower

thrust (between 8° and 10°). The low-pitch propellers produce approximately two pounds higher

thrust than the high-pitch propellers throughout the entire range of air speeds.

Figure 11: Dynamic thrust curve

The criterion for effectiveness demands highest static thrust (that is, thrust at zero wind speed).

Based on the curve fit for dynamic thrust, the 12” x 7° propeller produces the highest static

thrust, with 9.6 lbs thrust at zero wind velocity (Figure 11). This is greater than the 7 lbs

produced by the 2011 design using the O.S. engine and 12”x8° propeller. Therefore, the most

effective propeller for M-Fly’s application is the 12” x 7°.

4.2 Feasibility—Improved Thrust Curve

Figure 12 directly compares the dynamic thrust of the Magnum XLS motor with 12” x 7°

propeller to the configuration used by M-Fly in 2011 (O.S. motor with 12” x 8° propeller). Error

12

bars illustrate the contribution of vibrational noise to measurement data and represent a 95%

probability that the true thrust value is contained within the interval.

The criterion for feasibility is equal or increased thrust throughout the range of flight speeds

compared to the baseline 2011 motor configuration. The 12” x 7° propeller with the Magnum

motor outperformed the previous M-Fly propulsion system by at least 2 lbs over all flight speeds.

This guarantees that the motor will have adequate propulsive thrust over the entire flight

envelope and will be feasible for M-Fly’s design.

Figure 12: Magnum XLS with 12" x 7° versus 2011 motor configuration

4.3 Desirability—Maximum Thrust Power

Finally, the measure of propulsive power (thrust multiplied by velocity) at 100% throttle was

indicative of motor efficiency and used as a metric for motor desirability. Figure 13 illustrates

the calculated thrust power generated by each propeller over the range of air speeds.

The team found that the 12” x 7° propeller produced 0.33 hp, which was more power than any

other propeller tested and a 10% improvement over the 2011 configuration. Therefore, the 12” x

7° propeller is the most desirable motor for the given application.

Error bars show 95% confidence after time

averaging

13

Figure 13: Dynamic thrust power

5 Recommendation and Alternatives

The 12” x 7° outperformed all other propellers by all three of the previously described selection

criteria: effectiveness, feasibility, and desirability. Thus we conclude that the Magnum XLS and

12” x 7° motor-propeller combination meets or exceeds all benchmarks and is the best candidate

for the M-Fly 2013 design.

However, if design considerations required the selection of a smaller propeller, an alternative

propeller choice could be an 11” x 6° propeller, which produced marginally smaller static thrust

(0.6 lb less, Table 11) similar thrust curve improvement over the 2012 configuration (2 lb more,

Figure 12), and slightly less thrust power (40 ft-lb/s less, Figure 13) relative to the O.S motor.

6 Omissions and Limitations

There were several limitations in the experiment revealed by our data. One limitation is the

amount of time in the wind tunnel. Equipment used for testing, including the dynamic thrust

stand, the data acquisition system, and the wind tunnel were only available for two hours. We

took steps to optimize our time with our resources in the finite time given by performing

assembly and calibrations of the equipment before starting the 2-hour testing period. The time

allotted only allowed for the team to produce six to seven data points per motor/propeller

combination. More data points per test run would allow for a more precise thrust curve and

possibly a better recommendation. The shortage of time also prohibited repeat measurements of

the same propellers. We were unable to run the same test twice to confirm our findings.

Another area for improvement might be improving the sampling rate of the data acquisition

system. The LabJack equipment provided with the testing stand records data samples at only 2

Hz or two samples per second. Upgrading to a higher sampling rate system is highly

recommended in conjunction with a filter to cut down on the noise in the signal from motor

vibration. Additionally, the dynamic thrust stand used a 1-axis load cell. This was able to capture

axial loads—transverse force components were not recorded. The installation of a second

orthogonal load cell would provide additional insight into the loads produced by the motor. Both

these improvements to the data collection will provided a cleaner and more accurate result.

14

We were limited to test and give recommendations on only the six propellers provided by M-Fly.

We concluded that the 12” x 7° pitch propeller was the best in combination with the Magnum

motor out of the given options. However, all propeller diameter/pitch combinations in production

today were not tested. It can only concluded that the 12” x 7° propeller is the most optimum

propeller of the sample set but there may be a different propeller that is more desirable for use in

combination with the Magnum motor. Running more tests with different diameter/pitch

combinations could confirm globally that the 12” x 7° propeller is in fact the best of all possible

propellers for the M-Fly application.

In addition to being limited by the number of propellers, our recommendations are limited to

only the data collected through our tests. To confirm and verify our results, an in depth propeller

theory analysis is suggested. Measuring the rotational velocity (RPM) of each propeller during

test conditions would be required in order to apply blade element theory, which might help

explain or support our finding.

And finally, occupational exposure could be improved for future studies. While running the

motor in the tunnel, large amounts of unburnt fumes with harmful chemicals such as nitro

methane began to fill the air. To protect the health of individuals conducting the tests, we would

recommend respirators and goggles (such as commercial NIOSH type) be worn while the test

motor is running and producing exhaust. These measures will ensure the safety of all those in the

room during testing.

7 Cost Analysis

Table 3 summarizes estimated costs associated with the project. The team’s initial estimate to

complete the project was $18,537.16. However at the end of the project the actual total cost came

out to $18,560.42. This is $23.37 over budget. Labor comprised by far the largest cost category

of realized expenses, totaling $18,150 including overhead and benefits. The materials and

equipment are a fraction of the total (excluding labor): $264.79 in addition to $145.63 of

overhead.

8 Schedule

Thrust Unlimited established key milestones and target dates in order to ensure that all data and

final recommendations were delivered prior to M-Fly’s requested deadline of December 14,

2012. Table 2 outlines the milestones and actual dates of completion.

Thrust Unlimited was able to achieve all milestones ahead of schedule. A full Gantt Chart with

intermediate steps is included in Appendix D.

Table 2: Performance to schedule

Key Milestone Target Date Deadline Actual Completion

Break In Motor 11/1/12 11/11/12 11/7/12

Conduct Thrust Test Dry Run 11/12/12 11/25/12 11/13/12

Conduct Wind Tunnel Test 11/15/12 11/26/12 11/15/12

Formulate Recommendations 11/27/12 11/29/12 11/28/12

Complete Final Report 12/6/12 12/14/12 12/14/12

15

Table 3: Project costs

Item Unit Cost ($) Units Cost ($)

Labor

Duncan – Lead Engineer 40/hour 100 4,000.00

Justin – Engineer 35/hour 100 3,500.00

Ben – Engineer 35/hour 100 3,500.00

George – Engineer 35/hour 100 3,500.00

Joe - Engineer 35/hour 100 3,500.00

Terry - Consultant 150/hour 1 150.00

Subtotal 18,150.00

Facilities

Wind Tunnel (2’ by 2’) 60/hour 2 120.00

Student Shop No Charge 0.00

Subtotal 120.00

Materials

Powermaster 15% Nitro Fuel 31.02/gallon 1/4 31.02

O.S. #8 Glow Plug 6.98/plug 4 27.92

6061 Aluminum Flat Bar 11.98/1’ 6 71.34

Bolts (Grade 5, ¼”-20) 11.98/25 25 11.98

Nuts (Grade 5, ¼”-20) 2.53/100 100 2.53

Subtotal 144.79

Total 18,414.79

Overhead 55% of Total

(excluding

Labor)

145.63

Grand Total 18,560.42

Initial Estimate 18,537.16

Over budget 23.27

9 References

[1] Farokhi, Saeed. Aircraft Propulsion. N.p.: Wiley, 2008. Print.

A1

Appendix A: Engineering drawings

B1

Appendix B: Detailed Test Procedure

Part 1: Break-in Stand Operation: Outside the tunnel on static thrust stand assuming servo and

testing different propellers):

1. Ensure motor is correctly assembled to muffler and butterfly inlet assembly per

manufacturer instructions

2. Secure full motor assembly to the mounting bracket using (4) bolts provided

3. Secure the other end of the motor mount bracket to the front of the static thrust stand

using (4) bolts provided

4. Mount servo behind motor mounting plate on shelf using hot glue:

a. Make sure to orient the servo long side parallel with mounting plate

5. Bend servo linkage in order to connect the linkage rod between motor inlet valve and

servo actuator arm

6. Secure battery and transmitter using duct tape next to servo on the shelf

7. Make all necessary electronic connections between transmitter, battery, and servo

8. Turn on radio controller

9. Ensure radio controller operates the servo resulting in the butterfly valve opening 100%

and closing 100%

10. If radio controller does not operate as specified in step 9:

a. Remove servo from shelf using a screwdriver and attach in new location until step

9 is true

11. Connect 2 fuel lines:

a. One end of the fuel line to the inlet nipple on the butterfly assembly and the other

end to the bottom of the fuel tank

b. One end of the fuel line to the nipple on the muffler and the other end of the same

line to inside top of fuel tank

12. Secure fuel tank to center of base plate using duck take

13. Remove propeller nut from motor

14. Install propeller on the motor shaft

15. Secure propeller with propeller nut

a. Warning: propeller nut has reverse threads

16. Install glow plug in top of motor head using correct tools

17. Ensure glow plug igniter is fully charger

18. Clip glow plug igniter on glow plug

19. Ensure propeller crank starter is fully charger.

20. Align red rubber end of crank starter on propeller shaft nut and push

21. Turn on crank starter

22. Hold the throttle 25% open on the controller while crank starter is spinning propeller for

10 seconds or until motor starts

23. If motor does not start:

a. Turn off crank starter and remove from propeller shaft nut

b. Remove glow plug igniter

c. Wait 30 seconds

d. Repeat steps 18-22

24. Remove crank starter and glow plug igniter from motor

B2

25. Set controller to 100% open throttle enabling motor to reach maximum RPM

26. Run for 7 minutes

27. Kill motor by returning throttle lever on controller to full back position and then flicking

the kill switch on the top left of controller to ‘off’

28. If breaking in the motor for the first time:

a. Refill the fuel tank

b. Wait 3 minutes

c. Repeat steps 18-27 until 6 cycles have been concluded

29. Remove propeller nut and propeller from motor shaft


30. Install next propeller on motor shaft

31. Repeat steps 14-27 with new propeller until all propellers have been tested

32. Disconnect all fuel lines from motor, exhaust, and fuel tank

33. Disassemble (4) bolts holding motor bracket to thrust stand

Part 2: Dynamic thrust Stand Operation: Calibration of wind tunnel

1. Measure the atmospheric pressure with barometer

2. Turn on the wind tunnel main power box

3. Use the wind tunnel controller to set the motor RPM

4. Set the wind tunnel controller to 0 RPM and record the manometer reading on the

wind tunnel

5. Increase the wind tunnel by increments of 100 RPM until 1000 RPM is reached

recording the manometer reading at each step

6. Reset the wind tunnel to 0 RPM

7. Turn the wind tunnel main power box off

8. Use the manometer readings to figure out wind tunnel velocity

Part 3: Dynamic thrust Stand Operation: Calibration of load cell




3. Secure the other end of the motor mount bracket to the front of the static thrust stand


4. Place dynamic thrust stand on table 6” from edge

5. Attached wire to motor through a whole in mounting bracket

6. Place tripod in front of dynamic thrust stand

7. Route other end or wire over top of pulley attached to tripod

8. Adjust pulley height on tripod so the wire is perpendicular to the ground when the

wire passes over it and then is directed straight down

9. Connect the force transducer wire to the OMNI AMP III

10. Connect the OMNI AMP III to the LabJack

11. Connect the LabJack to a computer and open program

B3

12. Make sure that when the free end of the wire passes over the pulley and is directed

vertically downward that the wire does not hit the table

13. Remove rubber stop between front plate and force transducer

14. Record the reading of the force transducer when no load is put on the wire

15. Add base plate to free end of wire and record voltage from force transducer

16. Add additional mass in smallest increments until 12 lbs is reached remembering to

record the force transducer voltage output

17. remove all weights from wire

18. Detach wire from motor


Part 4: Dynamic thrust Stand Operation: Inside the tunnel on Dynamic thrust stand assuming

servo & testing different propellers):




3. Secure the other end of the motor mount bracket to the front of the dynamic thrust stand


4. Use (2) lock nuts on the top two bolts to prohibit them from backing out

5. Mount servo behind motor mounting plate on the left side of dynamic thrust stand using

hot glue:

a. Make sure to orient the servo long side parallel with mounting plate

6. Bend servo linkage in order to connect the linkage rod between motor inlet valve and

servo actuator arm

7. Secure battery and transmitter using duct tape next to servo on the stand

8. Make all necessary electronic connections between transmitter, battery, and servo

9. Turn on radio controller

10. Ensure radio controller operates the servo resulting in the butterfly valve opening 100%

and closing 100%

11. If radio controller does not operate as specified in step 10:

a. Remove servo from shelf using a screwdriver and attach in new location until step

10 is true

12. Place dynamic thrust stand with motor assembly in the wind tunnel test section

13. Secure dynamic thrust stand in wind tunnel using (2) bolts, (2) washers, and (2) wing

nuts

14. Install glow plug in top of motor head using correct tools

15. Secure fuel tank on the dynamic stand slide rail centered ~6” behind battery, transmitter,

and servo

16. Connect the force transducer wire to the OMNI AMP III

17. Connect the OMNI AMP III to the LabJack

18. Connect the LabJack to a computer and open program

19. Make sure ONMI AMP III, LabJack, and computer are outside of wind tunnel

20. Connect 2 fuel lines:

a. Fuel line to motor from fuel tank:

B4

i. One end of the fuel line to the inlet nipple on the butterfly assembly

ii. Other end of fuel line connected to bottom of fuel tank

b. Fuel line from motor return to fuel tank:

i. One end of the fuel line to the nipple on the muffler

ii. Other end of the fuel line connected to the inside top of fuel tank

21. Warning: Ensure rubber stop is installed between front plate of dynamic thrust stand and

force transducer. If not, install it.

22. Install propeller needing to be tested on the motor shaft and secure with nut


23. Ensure glow plug igniter is fully charger

24. Ensure propeller crank starter is fully charger.

25. Ensure fuel tank is full

26. Clip glow plug igniter on glow plug

27. Align red rubber end of crank starter on propeller shaft nut

28. While a person hold the thrust stand in place in the wind tunnel push the crank starter

onto the propeller nut with force

29. Turn on crank starter

30. Hold the throttle 25% open on the controller while crank starter is spinning propeller for

10 seconds or until motor starts

31. If motor does not start:

a. Turn off crank starter and remove from propeller shaft nut

b. Remove glow plug igniter

c. Wait 30 seconds

d. Repeat steps 26-30

32. Remove crank starter and glow plug igniter from motor

33. Remove rubber stop between front plate and force transducer once motor is running

34. Set controller to 100% open throttle enabling motor to reach maximum RPM

35. Close and secure wind tunnel

36. Record manometer reading in tunnel when tunnel is off.

37. Record value from force transducer

38. Turn wind tunnel on

39. Record 6 manometer readings between wind tunnel velocity free stream values of 0 m/s

and 70m/s and their correlating force transducer measurements

a. Make sure to wait until the tunnel had stabilized at set speed before recording

manometer and pressure transducer readings

40. Turn off wind tunnel and open test section

41. Kill motor returning throttle lever on controller to full back position and then flicking the

kill switch on the top left of controller to ‘off’

42. Remove propeller nut and propeller from motor shaft


43. Repeat steps 23-42 until all propellers have been tested

44. Disconnect all fuel lines from motor, exhaust, and fuel tank

45. Remove dynamic thrust stand from test section.


47. Clean wind tunnel walls downstream of motor exhaust

C1

Appendix C: Calibrations Prior to Testing

Prior to conducting wind tunnel testing on Mr. Larrow’s thrust stand, the force transducer was

calibrated by applying known loads and measuring the voltage output. Although the force

transducer produces linear output in both tension and compression, the loads were applied in the

forward direction, in the same way that the motor pulls forward. Two calibrations were

performed prior to testing, and subsequent calibrations were taken between tests as we changed

propellers outside of the tunnel.

Figure 14: Calibration of force transducer

Figure 15: Force transducer calibration

C2

Figure 16: Wind tunnel calibration

Force Transducer Calibration 1

Load (lb) Transducer output (V)

0 -5.4234

0.565 -5.3456

1.565 -5.21

2.565 -5.0918

3.565 -4.955

4.565 -4.8152

5.565 -4.6723

6.565 -4.5421

7.565 -4.4081

8.565 -4.27

9.565 -4.1453

10.565 -4.0167


Load (lb) Output Voltage (V)

0 -5.45

0.565 -5.37

1.565 -5.22

2.565 -5.12

3.565 -4.99

C3

4.565 -4.84

5.565 -4.7

6.565 -4.56

7.565 -4.42

8.565 -4.28

9.565 -4.16

10.565 -4.03


Load (lb) Output Voltage (V)

10.565 -4.04

9.565 -4.16

8.565 -4.28

7.565 -4.42

6.565 -4.56

5.565 -4.68

4.565 -4.84

3.565 -4.97

2.565 -5.11

1.565 -5.24

0.565 -5.37

0 -5.45

Wind Tunnel Calibration

Wind Tunnel Fan Speed

(RPM)

Manometer

(in H20)

0 0

200 0.02

300 0.08

400 0.15

500 0.24

600 0.34

700 0.47

800 0.62

900 0.79

1000 0.97

Drag Measurements

Wind Tunnel Fan Speed

(RPM)

Voltage Output

(V)

0 -5.4234

C4

250 -5.3793

560 -5.4165

740 -5.4568

850 -5.4859

980 -5.532

D1

Appendix D: Project Management

Table 4: Project Gantt chart

Project management was partially conducted MS Project in order to identify critical paths in the

project. Project was used to produce the Gantt chart in 4. This led to identification of the “dry

run” as a critical task, which had potential to delay testing and delivery of results. By ensuring

that the critical path of tasks for the project was met, we were able to avoid delay and meet all

deadlines early or on time. Figure 17 is a project plan flow chart representing the steps in our

project and the dependencies between tasks.

Figure 17: Project plan

E1

Appendix E: Raw Thrust Data

XLS-61A with 12" x 7o propeller

Velocity

(ft/s)

Thrust

(lb)

Power

(ft*lb/s)

0 11.6412 0

6.12 9.11 55.7531

12.28 8.3563 102.6157

16.6158 6.9986 116.287

31 6.9686 216.0252

43.68 5.6369 246.2216

54.9063 5.0457 277.0396

63 4.4229 278.6453


Velocity

(ft/s)

Thrust

(lb)

Power

(ft*lb/s)

0 6.1016 0

12.28 6.4371 79.0482

25.6595 5.9105 151.6595

34.155 5.2299 178.6275

41.7678 4.4989 187.908

52.3295 3.9754 208.028

59.755 2.9871 178.4971


Velocity

(ft/s)

Thrust

(lb)

Power

(ft*lb/s)

0 6.6345 0

9.195 6.4135 58.972

19.7248 6.7868 133.8692

27.855 4.8681 135.6018

37.32 5.0428 188.1965

45.9155 3.8056 174.7339

53.9392 3.0887 166.6

61.7008 2.6526 163.6683


Velocity Thrust Power

E2

(ft/s) (lb) (ft*lb/s)

0 6.9728 0

12.28 5.7213 70.2576

22.2192 6.1305 136.215

31 5.0528 156.6374

41.1312 4.8002 197.4386

52.0078 4.3968 228.6689

61.0518 1.0584 64.618


Velocity

(ft/s)

Thrust

(lb)

Power

(ft*lb/s)

0 9.2836 0

14.1358 8.0413 113.6697

23.2188 6.8938 160.065

29.7408 6.6747 198.5117

37.32 6.9169 258.1381

44.3182 6.1818 273.9678

54.5838 5.9829 326.5692

61.3762 2.7458 168.5294


Velocity

(ft/s)

Thrust

(lb)

Power

(ft*lb/s)

0 7.2123 0

10.7363 7.5624 81.192

18.48 7.9732 147.3454

28.7974 6.6078 190.2885

39.2238 6.1129 239.7692

46.875 7.1918 337.1155

57.9422 4.2691 247.361

december 14, 2012 joshua matthews, chief engineer m-fly …€¦ · december 14, 2012 joshua...

Documents