Design Team 13

Twin-Engine Remote Hovercraft

January: Build Report

Raymond Fitzpatrick

B00322395

Martin Mitchell

B00433676

Jake Martell

B00431852

Travis Lunn

B00448582

Jeremy Keans

B00450500

Dr. J.M. Chuang

Submission Date: January 13th, 2009

Submitted to: Dr. J. Militzer

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Table of Contents Table of Contents ................................................................................................................ 2 List of Tables ...................................................................................................................... 3

List of Figures ..................................................................................................................... 3 1. Introduction ................................................................................................................. 4 2. Design .......................................................................................................................... 5

2.1. Thrust Powertrain ................................................................................................. 6 2.2. Lift Powertrain ..................................................................................................... 7

2.3. Platform & Skirt ................................................................................................... 8 2.4. RC Control & Steering ......................................................................................... 9

3. Final Budget .............................................................................................................. 10 4. Technician Time Required ........................................................................................ 11 5. To Be Determined ..................................................................................................... 11

5.1. Platform & Skirt ................................................................................................. 12 6. Progress Summary & Schedule ................................................................................. 12

Appendix A: Calculations ................................................................................................. 22 Appendix B: Drawings ..................................................................................................... 24

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List of Tables Table 1: Main Parts List for Thrust Assembly.................................................................... 7 Table 2: Main Parts List for Lift Assembly ........................................................................ 8

Table 3: Main Parts List for Platform and Skirt ................................................................. 8 Table 4: Main Parts List for Steering / RC Control Assembly ........................................... 9 Table 5: Final Budget........................................................................................................ 10 Table 6: Estimated Technician Time Requirements ......................................................... 11

List of Figures Figure 1: Final Design ........................................................................................................ 5

Figure 2: Thrust Powertrain Assembly ............................................................................... 6 Figure 3: Lift Powertrain Assembly ................................................................................... 7

Figure 4: Platform ............................................................................................................... 8 Figure 5: Steering Control Assembly ................................................................................. 9

Figure 6: Gantt Chart ........................................................................................................ 16

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1. Introduction

Team 13 is undertaking the design and construction of a twin-engine remote

controlled hovercraft also known as an Air Cushioned Vehicle (ACV) which will be

capable of carrying a 100 lb payload across various terrains. The design was selected

after using iterative design methodology in which many different designs for the four

separate sections were considered. The main focus was to find the best balance between

performance, budget, and construction feasibility.

The selected design consists of two engines (one lift & one thrust), a bag skirt

design, single plate platform, and rotating thrust fan for steering. This prototype

hovercraft design will utilize all of the thrust power from the fan by rotating the fan

versus using the conventional flaps which reduce air flow. The hovercraft will be

controlled using a 6 channel remote control and receiver which will control both engine

throttles as well as steering of the craft. In order for safety the craft will be equipped with

two kill switches, one for each engine. This report will outline the build requirements,

preliminary budget, and a list of items which have yet to be determined, as well as a

Gantt chart for the remainder of fall 2009 and through winter 2010.

Team 13 will build and test the designed hovercraft which will be constructed in

the winter 2010 term.

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2. Design

The hovercraft design incorporates many challenges for Team 13 to overcome.

These challenges presented themselves throughout the design process. The design

minimizes the center of gravity of the overall craft in order to increase the stability of the

overall ACV. The overall final design is the one that uses tried and tested hovercraft

design with a state of the art rotating thrust fan for steering, which can be seen in

Figure 1.

The hovercraft was designed by separating the craft into four separate sections:

Thrust Powertrain, Lift Powertrain, Platform & Skirt, and the Remote Control, Steering,

and Electronics.

This section will outline any design changes which have been made to the

hovercraft since the last Build report submitted in November[Design Team 13, Build

Report I, Nov.2009].

Figure 1: Final Design

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2.1. Thrust Powertrain

The thrust powertrain as shown in Figure 2 is the system responsible for lateral

propulsion of the ACV. To keep the center of gravity as low as possible the engine will

be mounted directly onto the rotating steering plate, see Section 2.4 for details on the

rotating steering plate. The center of gravity was largely taken into account in order to

maximize the overall stability of the craft. In order to drive the fan, the drive shaft of the

engine will have an attached gear sprocket which will be attached to the input shaft of the

fan via chain. The thrust fan is attached directly to the input shaft using a key and bolt

connection.

Since the last Build Report the only change has been made to the fan support

frame. In order to increase stiffness and strength we have added a second strip of

aluminum which will be welded to form an L-Beam as can be seen in detail in Figure 3.

This will require more technician time as no team member is a qualified welder.

Figure 2: Thrust Powertrain Assembly

Figure 3: L-Beam Support Mount

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Table 1: Main Parts List for Thrust Assembly

Item Description Qty Engine 6.5 hp horizontal shaft engine (make TBD) 1

Fan 22" diameter fiberglass fan 1

Dampers Rubber dampers (from scrap) N/A

Fan Supports Custom manufactured aluminum fan supports 10

Sprocket 10 tooth V-Series sprocket 2

Chain Length of chain 1

Fan Shaft 3/4" custom shaft 12" length 1

Angular Bearing 3/4” bearing for thrust and radial load 1

Bearing Block Custom built block for angular bearing 1

Pillow Block Radial bearing 1

Nuts & Bolts Size not selected N/A

Mounting Plate 24" OD aluminum mounting plate 1

2.2. Lift Powertrain

The lift powertrain as shown in Figure 4 is in charge of providing the necessary

pressure underneath the craft to lift the craft’s weight off of the ground. This pressure is

created using a vertical shaft engine attached directly to the lift fan. This fan forces air

directly into the bag skirt, see Section 2.3 for bag skirt details, which then inflates the

skirt and creates the pressure under the craft.

As with the Thrust Powetrain supports, the same change has been made to the Lift

Powertrain as was depicted in Figure 3. The Support Mounts are now L-Beam mounts so

that they are structurally stronger. The height of the vertical fan has also been raised in

order to allow for a smoother transition of airflow from the fan to the skirt.

Figure 4: Lift Powertrain Assembly

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Table 2: Main Parts List for Lift Assembly

Item Description Qty Engine 5 hp vertical shaft engine (make TBD) 1

Fan 20" diameter fiberglass fan, 5 vane 1

Key Standard square key way for 7/8” shaft 1

Dampers Rubber dampers (from scrap) N/A

Engine Mounts Custom manufactured aluminum fan supports 6

Mounting Plate Custom manufactured aluminum engine mount plate 1

Nuts & Bolts Not yet selected N/A

2.3. Platform & Skirt

The most important aspect of design of a hovercraft is the platform as shown in

Figure 5 and skirt design. This design is essential as it separates the lift air flow and

creates the high pressured area beneath the craft which lifts the vehicle. The platform is

also the housing for all the mountings of equipment such as engines, electronics, and

fans.

The main design alteration to the platform is in the size and location of the air

flow channel to the skirt. In order to feasibly channel the airflow into the skirt, the hole

was greatly reduced from 22” to 12” in diameter, and the lift powetrain was raised to duct

air into the 12" diameter hole. This design change allows for a much simpler ducting

design, as well as keeping construction and assembly as straight forward as possible.

Figure 5: Platform

Table 3: Main Parts List for Platform and Skirt

Item Description Qty Aluminum Plate 5.5’ x 3’ with 18” radius and 22.5” dia. hole 1

Skirt Material Black-8 linear yards N/A

Flotation Added buoyancy N/A

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Strengthening Ribs Aluminum rods for added strength N/A

Skirt Bolt Strips Aluminum strips to pinch skirt to platform N/A

2.4. Remote Control & Steering

A majority of RC control components have already been obtained free of charge,

such as a 6 channel controller and receiver along with 5 servomotors. These have all

been salvaged from previous design projects and will work perfectly for our

requirements.

No serious design alterations have been made in this section. The steering is

controlled by a servomotor which will rotate the centre shaft causing the thrust

powertrain to rotate and steer the hovercraft by redirecting thrust air. The assembly can

be seen in Figure 6.

The remaining remote control is controlled by four small servomotors, two

responsible for the kill switches on each engine, and two for the throttle control of each

engine. These five servomotors combine to control all of our required control systems,

steering, lift, thrust, and emergency shutoff.

Figure 6: Steering Control Assembly

Table 4: Main Parts List for Steering / RC Control Assembly

Item Description Qty Bearing Thrust and radial bearing w/ housing 1

Shaft Shaft

Sprockets 10 tooth V-Series sprocket 2

Chain Size and length of chain 1

Bearing Plate Supports Caster wheels to distribute load 6

Steering Motor Ultra torque servo motor (manufacturer TBD) 1

Remote Control 6 Channel 1

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Servos Small Servos 5

Battery 6 Volts for Receiver 6.0V for more power (optional) 1

3. Final Budget

The following section outlines a detailed budget of all the necessary parts to build

the hovercraft. A full budget can be seen in Table 5.

Table 5: Final Budget

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4. Technician Time Required

Team 13 will be requiring a significant amount of time from the shop technicians

in order to build the hovercraft. This work will be mainly with aluminum in order to

create the overall craft and its components. Although some of the work can be done by

the team, the estimated technician time required as shown in Table 6, which does not take

this into account. Included in this table is also the time which will be required for the

welding for the support frames.

Table 6: Estimated Technician Time Requirements

Component Material Work Description Qty Est. Time

Platform Aluminum

-Cut out overall shape -Remove 12" hole in front -Drill bolt holes as required

1 ~ 10 hr

Horizontal Engine Mounting Plate

Aluminum

-Cut 22" diameter plate -Drill bolt holes as required

1 ~ 2 hr

Vertical Engine Mounting Plate

Aluminum

-Cut 24" diameter plate -Cut and remove suction sections -Drill bolt holes as required

1 ~ 4 hr

Fan Supports Aluminum -Cut strips -Drill bolt holes -Welding of brackets

~ 4 hr

Bearing Housing Steel -Bore bearing housing -Drill bolt holes

1 ~ 1 hr

Fan Shaft Steel -Turn correct diameters of stepped shaft -Turn groove for circlip

1 ~ 2 hr

Steering Shaft Steel -Turn groove for circlip 1 ~< 1 hr Servo Motor Support

Aluminum -Cut and drill as shown 2 ~ 1 hr

Shroud Steel -Cut steel -Weld as shown

2 ~ 1 hr

Consultation N/A -For assembly N/A ~ 5 hr

TOTAL ~ 31 hrs

5. To Be Determined

At this time there are only a few aspects which need to be determined with respect

to the building of the hovercraft.

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5.1. Platform & Skirt

The design of the number of holes as well as location of holes to be placed in the

skirt is still to be determined. As is the cutout shape of the skirt, and the foam placement

within the skirt. These are to be decided when the platform is constructed so we can

mock up the skirt without cutting it to ensure it is done correctly.

5.2. Mounts and Bolts

The servomotor's responsible for engine kill switches and throttles

mounting brackets are still to be determined. It was decided to wait on designing these

until we were ready to install the servomotors, which would allow us visualize better

where they will be positioned with the assembly together. Due to the very small size of

the servomotor's this is a minor design and will just need to be bolted down.

The fan shroud mounts are also still to be determined. Mainly because we

are waiting to see how the sheet-metal will shape up into its circular shroud, then mount

supports will be fabricated to hold the sheet metal in place.

Finally, the bolts are still to be determined. This is once again a minor step

because we just need to determine what size and what length bolts will be used in certain

applications throughout the hovercraft.

6. Progress Summary & Schedule

Purchasing of parts has begun and will continue until all parts have been ordered.

Once parts are received construction will begin in order to remain on schedule as outlined

in the gantt chart below, shown in Figure 7. Since the parts have yet to be received we

cannot outline a construction plan. This will be decided upon once the first parts are

received.

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Figure 7: Gantt Chart

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Appendix A: Calculations

Skirt Volume and Buoyancy Calculation:

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Thrust Calculation (National, 2008)

Given

Where,

= volume flow rate of air

= density of air at a given temperature and pressure

Then the thrust (T) is defined as

Where,

= mass flow rate of air

= discharge velocity of air

= total cross sectional area of the fan

Therefore,

Convert the thrust to lbf,

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Appendix B: Parts List

Part Manufacturer Part No Ordered Arrived Shop

6.5 Hp Horizontal Shaft Engine Powerfist N/A Y Y N

Thrust Bearing Misumi BGCSB14 N N N

Vertical Thrust Bearing Shaft Misumi

SFRJ30-40.0-F16.0-H5.0-G16-P10-T30.0-Z7.5-V16-Q14 N N Y (mod)

Horizontal Motor Mount N/A N/A N N Y

Top Plate ?????? N/A N N Y

Thrust Fan Shaft N/A N/A N N Y

Bearing Support Frame N/A N/A N N Y

Bearing Support Frame 1 N/A N/A N N Y

Bearing Support Frame Cross Brace N/A N/A N N Y

Caster Bearing ???? ?????? N N N

5 HP Vertical Shaft Engine Powerfist N/A Y Y N

22" Hascon Wing Fan Slipstream Fan-AC-A1259-MBL-TC-Promoco N N N

3/4" Pillow Block and Bearing Princess Auto N/A N N N

Thrust Bearing Block N/A N/A N N Y

3/4" Tapered Roller Bearing Princess Auto N/A N N N

3/4" V Series Hub Princess Auto N/A N N N

10 Tooth V Series Sprocket Princess Auto N/A N N N

#50 Roller Chain Princess Auto N/A N N N

10 Tooth V Series Sprocket Bored Out Princess Auto N/A N N Y

Servomotor Plate and Hub N/A N/A N N Y

Vertical Rotation Servo Mount N/A N/A N N Y

Caster Bearing Mount N/A N/A N N Y

Motor Mount Brackets N/A N/A N N Y

Motor Mount Brackets 1 N/A N/A N N Y

Bag Skirt With Holes ???? ?????? N N N

Lift Fan Shroud N/A N/A N N Y

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Appendix C: Drawings