Mech 3305 project report

1. MECH 3305.002 CAD Project
ROBOTIC BOAT
Design Report
Team Members: Jason Zubrick, Husam Wadi, Jason Comiths, Demarcus Lott
Date: April 6, 2015
Due Date: April 30, 2015

2. System Description:
Initial Considerations
In contrast to other CAD teams who create static CAD models, Our CAD team created a
make-shift toys boat with full maneuverability and significant storage capability. The boat has
robotic components that will enable full aquatic mobility.
However, the ability to have full teleoported control comes at a stiff price. Many hours of
planning was spent to ensure that all the components fit within the boat. Namely we had to
ensure that a microcontroller, the Arduino Nano, micro motors, motor controller, battery, servo,
IR sensors, LEDs, and wiring all fit and were light enough to allow the boat to float. Our original
prototype ensured us that the volume could be enough to offset the mass, as the density of water
=1. If the mass exceeded the volume then the boat would sink 𝐷 =
𝑚
𝑣
.

3. We wanted the boat to satisfy these functions:
 Be teleoported via IR for remotes and IR enabled smartphones
 Ability to flash police lights (red and blue LED)
 Ability to shoot rubber bands (servo enabled)
 Ability to be steered via tank drive (two side by side motors instead of a motor and a
servo for direction)
 Waterproof/Float
 Physically Appealing
Design Strategy:
Once the size and rudimentary dimensioning was settled, we began designing and assembling the
components of the boat. Our team liked the general shape of the hunter cigarette boat, so we
decided to shape the hull of the boat similar to the boat shown below:
The overall design processes followed in this timeline format:
1. Hull (bottom of boat)
2. Hulltop (top of boat)
a. Gear (rubber band shooter)
b. Servo Mounts
c. Rails (cosmetic)
d. Hook (tip of boat)
e. Lip (seals top and bottom of the boat)
3. “Cabin” (top of boat, houses IR sensors and windows)
a. Window Cut Out
b. Steering Wheel
c. Steering Dashboard
d. Flag
4. Hull Functionality
a. Motor Housings (Holds the motors in place)
b. Propeller Shaft (transmits force from the motor to the propeller)
c. Propeller

4. First we designed the hull, the bottom part of the boat, which took the most time and
effort. The design for the hull had a significant impact on the design on the rest of the boat. Its
volume played a part in what and how much robotic components we could use. Its thickness
limited the material was left for the rest of everything else. Its overall shape effected how we
place each component inside. Last but not least, the curves about it determined how it'll flow
through the water. It was, in every sense of the word, the foundation of our project.
Designed in Creo, the hull had to be big enough to house all the internal components but
thin enough as to leave printing volume for all the other required parts. Once the hull was lofted,
we “democratically” debated on how thick the walls should be; eventually our team settled on
between 1/8 inch (.125) and 1/16 inch (.0625) at exactly (.08).
Once the hull was foundationally completed, we sectioned the top piece of the boat
(Hulltop) to be completed. The hull was exported to Solid works for quick designing of the
Hulltop. Originally, the hull top was to be one solid piece, with it beginning at 0.75 inches thick
and tapering off to 0.25 inch thick, however this was later exchanged with the tapered part (the
cabin) to be its own separate piece. Much consideration was given to the design of the top of the
hull as it had to be functional and look pleasing to the eye. Also, we decided to give the bottom
part of the boat, the hull, a seal so that it does not rattle off the hulltop. We constrained the servo,
motors, and Arduino Nano within the hull (these parts were downloaded from grabcad.com as
they provided really accurate dimensions and saved us hours of work designing the electrical
components). With the functional parts constrained, their profiles were referenced to the hull top
to create extrusion cuts for the servo and servo mounts, gear, rubber band holder, and cabin cut
out:

5. CAD PROTOTYPEHulltop
Tuesday, April 14, 2015
1:19 PM
A 3D printed gear was needed to wind up a 6 shot rubber band system for the boat. The
gear was to be press fit into a servo and the two pieces were to be aligned so that the tip of the
gear teeth was flush with the midpoint of the boat. The idea was that a button would be pressed
on a remote and it would actuate the servo 60* to allow one rubber band to fly. The inspiration
for this design comes from a fairly generic “rubber band gun” found in hobby stores:

6. If one notices our gear comes out horizontally instead of vertically as in the rubber band
gun picture. This was due to keeping the boat waterproof and lack of space within the hull
interior (instead of a large rectangular cut we can have a tight circular cut with the horizontal
gear). Once the gear was created in Solidworks, Servo Mounting/Spacers were made to offset the
servo from the top of the boat. It was a fairly simple piece with a hole through the center to allow
a bolt and nut to go through. After gear and servo spacer were created, a rubber band holder
(hook) was parametrically created in Creo to allow the rubber band to be stretched by the
rotation of the gear. The piece was exported into solid works and constrained to the very front
and center of the boat.
At this point the hull is almost complete, with the functionality of the rubber band shooter
settled it was time to create cosmetic appeal to the Hulltop. Railings were made by referencing
the curvature of the boat and were seamlessly mounted to the hulltop.
The cabin was parametrically designed in Creo then imported into Solidworks for
assembly. Rectangular holes were made in the sides and back to allow IR sensors to be inserted.
A separate rectangular hole was made for the charging port in the rear and another on the top to
allow wires to be routed for an on/off switch for the boat. Finally two holes were extruded cut
from the front of the boat for cosmetics and flashing LED lights.
After the completion of the cabin, cosmetic pieces were made to fit on top of the boat. A
steering wheel and steering wheel base were made to be placed on the top surface of the boat to
give it cosmetic appeal. A flag was also made in Creo parametrically then exported to
Solidworks and placed on top of the boat. An extruded hole was made to ease in placement of
the flag.

7. Back to the hull design, after all the other components were secured the most important
functional pieces were created: Motor and Propellers. The motors were mounted and fixed in the
assembly at a 30* angle, the reason for the angle is that if the motors were mounted horizontally
water would leak into and sink the boat. Referencing the motors, two hollow extrusions were
created into the hull to allow the motors to slide into place. Then a propeller shaft was created
referencing the motor shaft to allow the propellers to be offset from the bottom of the boat. With
the shaft and motor mounting created, propellers were made using angled planes and allowed to
allow a virtual screw to push or pull the water surrounding the boat. The propellers were made
with an extrusion so that they can be separately fit to the propeller shaft. The reason behind this
design step is to allow easy of assembly with the motors. The motors will be fit to the shaft,
inserted into the hull then the propellers will be glued to the shaft from the exterior of the hull.

8. With all the cosmetic and functional parts completed the boat took this final shape:

9. Parts Models and Methods:
Hull: The hull of the boat was created using a swept blend. First 10 offset datum planes
were created from the front plane that were offset by 0.5 inches. Then on each of those planes a
sketch of half of the profile of the boat was created using a cubic spline. For the first seven
sketches on the front plane and the first six datum planes the sketch remained constant and then
decreased in size successively on datum planes 7-10. After this was done a projection path was
sketched along the top corner of all the sketches connecting them together. After this was
completed the swept blend option was selected from the shapes group of the model tab. The line
connecting the sketches was selected as the trajectory and then each of the sketches was inserted
as a selected section. This created the first solid half of our boat. The swept blend was then
mirrored about the right half of the boat to give it the correct profile. After this was completed
the model was converted into a parasolid and imported into SolidWorks where it was then
shelled and the motor housing was added. To create the motor housings for the hull the motors
were first situated and constrained to a 30* angled plane and the edge of the hull. With the
motors fixed, a .125 inch offset plane from the angle plane was created and a sketch made on that
plane. The edges of the motor housing were referenced onto the plane and then offset by .01
inch. Another offset loop was created .025 inches from the original converted entity and the
offset loop was extruded to the tip of the gearbox of the motor (roughly .5 inch). Then a .125
thick base was made on the backside of the extrusion with a centered hole .25 inches in diameter
to allow the propeller shaft to exit the boat. A 0.4 inch diameter circle extrusion was made from
the base of the offset motor housing to the surface of boat completing the motor housing and
shaft exit.
Hulltop: After the hull was exported to Solidworks the top surface of the hull was
referenced into a sketch. That reference was then finished into a loop and extruded 0.25 inch.
With a solid feature the part was shelled with 0.07 inch thickness and the bottom face of the part
was selected to be removed. With a shelled feature, a 2 inch by 2 inch hole was extrude cut from
the rear of the hulltop, centered about the middle of the boat. This cutout was made to
accommodate the cabin. Then 3 holes were made for the servo mounting and gear. A sketch was
made referencing the servo holes then offset holes by .01 inch were made off the referenced
circles. A 0.4 inch hole was made to accommodate the gear in that sketch. All 3 holes were
extrude cut – through all surfaces of the hull top. After the completion of the holes we decided to
create 3 thin lips each on one of the corners of the boat profile (2 in the back 1 in the front).
These lips were 0.1 inch wide and were extruded to the bottom face of the hulltop in one
direction and 0.1 inches in the other direction.
Gear: The gear was created as a component within the main hull assembly. Referencing
the hole created in the hulltop an offset circle of 0.02 inch was made as the surface of the gear
exterior. The interior wall of the gear was offset from the exterior by .10 inch. Extruding the

10. hollow cylinder .6 inches, a sketch was then created on the top surface of the new cylinder. A
circle sketch was made centered about the cylinder axis and this circle was given 0.25 inch
diameter. After the gear face was extruded 0.1 inch, and advanced pattern was made with another
extrusion off of the gear face. A U profile was extruded from the edge, with the tip of the U
centered about the middle of the boat, and this new extrusion was axially patterned 6 times
equidistantly around the edge of the gear face. With that complete the gear was completed with
its full set of teeth.
Servo Mount: Referencing the holes created in the Hulltop for the servo, a slightly
ellipse profile was created on the bottom of the hulltop. The profile consisted of two circles each
.1 inch in diameter linked together by two parallel lines 0.5 inch long. The excess lines from the
circle were trimmed leaving a nice oval surface that was extruded from the bottom side of the
Hulltop to the fixed surface of the Servo.
Rail: To create the rail, a sweeped feature needed to be created. The edge of the
hull/hulltop was referenced into a sketch onto the top face of the hulltop. This edge was to be
used as the path of the sweeped profile. A second sketch was made on the rear flat face of the
hulltop. An I-beam shape was created using two 0.05 by 0.1 inch rectangles connected and
centered by a 0.05 by 0.05 inch square. Excess edges were trimmed, and then the sweep tool was
invoked referencing the I-beam sketch and the edge of the hulltop as the pathway creating a solid
rail feature. To create the rivets in the rail a plane was made parallel to the starting edge of the
rail (since the rail was a curved edge a sketch could not be created directly onto its face). A 0.09
by 0.09 square offset by 0.03 from both edges of the rail was created in a sketch. Fortunately
Solidworks has a curve driven pattern tool in which the edge of the rail was referenced as the
curve and the extrusion cut of the 0.09 by 0.09 square as the patterned feature. An equidistant
spaced pattern of 40 entities was created giving the rail the perforated look. Unfortunately the
mirror tool did not work so we had to repeat the process for the rail on the other side of the boat.
Hook: The hookof the boat wasmodeledbycreatingaparametriccurve thatwas usedas the
path fora sweepoperation.The equationof the parametriccurve instandardformis
𝑃( 𝑡) = [
𝑥( 𝑡)
𝑦( 𝑡)
𝑧( 𝑡)
] = [
𝑡
38.8316𝑡3 − 14.7818𝑡2 + 2.27302𝑡
0
] 𝑤ℎ𝑒𝑟𝑒 𝑡 ∈ [0,0.7]
The equationsrepresentedabovewere putintoCreousingthe curve fromequationoptioninthe datum
groupof the model tab.
A thinrectangle wasof height0.45 inchesandwidth0.1 incheswasextrudedalongthe pathfor0.7
inchestomake a rectangle thathad an S shapedprofile.Thenasketchof a roundedshape made usinga
spline thatwasclosedwasextrudedalongthe widthof the material foraddedsupportbecause thisisa
functional partmeantto holdthe force associatedwiththe tensionof the rubberbandthatwill be
placedonit. The frontendof the hookwas thenroundedbycreatingan extrudedcut.Afterthiswas

11. complete anotherextrudedcutwasusedtomake the prongsat the front of the hook thatwill be used
to holdthe rubberband.
Cabin: The cabin of the boat was modeled by creating a parametric curve that was used
as the path for a sweep operation. The equation of the parametric curve in standard form is
𝑃( 𝑡) = [
𝑥( 𝑡)
𝑦( 𝑡)
𝑧( 𝑡)
] = [
𝑡
−8.07462𝑡3
+ 5.91105𝑡2
+ 0.0631316𝑡
0
] 𝑤ℎ𝑒𝑟𝑒 𝑡 ∈ [0,0.5]
The equations represented above were put into Creo using the curve from equation option in the
datum group of the model tab.
A thin rectangle was then extruded using a sweep operation along this path. This created the
front surface of the cabin. Then a profile of the curve was projected onto a sketching plane and
used to create a new shape that was then extruded across the surface to make a solid part. This
part was then shelled to the required thickness of 0.07. After these operations were completed,
the cuts for the windows were made and the ledges for the sensors were added at the window
openings.
Steering Wheel: The steering wheel was based off the stereotypical pirate ship steering
wheel. To make it a circle was made and extruded into a cylinder. A ring was cut out of the
middle of this disk. This left an outside ring and a smaller inner disk. A rounded peg was made
by making the cross section and revolving. This rounded peg, which functions as a handle, was
patterned circularly around the disk and ring. This completes the steering wheel.
Steering Dock: A fairly simple piece, this part was created using a rectangular profile
centered on the top of the cabin. The profile was extruded and a 0.25 inch/45* chamfer was
created on one edge of the rectangular extrusion. A circular sketch was created centered on the
chamfered edge and extrude cut 0.20 inches deep. This circular cut was created to hold the
steering wheel in place.
Flag: The flagof the boat wasmodeledbycreatingaparametriccurve that was usedas the
path fora sweepoperation.The equationof the parametriccurve instandardformis
𝑃( 𝑡) = [
𝑥( 𝑡)
𝑦( 𝑡)
𝑧( 𝑡)
] = [
𝑡
10.2525𝑡3 − 11.952𝑡2 + 3.7303𝑡
0
] 𝑤ℎ𝑒𝑟𝑒 𝑡 ∈ [0,0.75]
The equationsrepresentedabovewere putintoCreousingthe curve fromequationoptioninthe datum
groupof the model tab.

12. A thinrectangle of height0.5 inchesanda widthof 0.07 incheswasextrudedalengthof 0.75 inches
alongthe parametricpath. Afterthisstepwascompletedaflagpole of diameter0.08 incheswas
extrudeddownwardstoa lengthof 0.75 inchesfromthe top of the flag.
Propeller Shaft: With the motor housing created, a new part was created within the
Solidworks hull assembly. Referencing the bottom face of the motor shaft, an offset 0.01 inch
loop was created from the motor shaft (the shape resembled the letter “D”). A circle was made
centered around the motor shaft with diameter 0.25 and the profile was extruded 0.4 inches. Then
a full circle extrusion was created 1 inch from the hollowed cylindrical feature.
Propeller: The propeller was a fairly difficult part to make. To start off, a cylinder was
made by extruding a circle. An angled plane was made from the base. Then a fin of the propeller
was made with the spline tool and some finagling. This fin was patterned around the cylinder to
complete the propeller. This sounds quick and easy, but you had to make sure that each fin was
completely incased in the cylinder and that the fins where angles to a proper degree. Also the
overall shape of the fin was taken into consideration.
Assembly Model:
Since there are many functional parts within the boat that all have to be constrained beforehand,
we used a top down model almost unanimously from start to finish. The hull and all the other
team had to literally be at the same place and same time to work on the parts (since they were all
linked together) scheduling posed a problem with the “Top Down” approach; however, this
design path proved essential for the functionality and constraints of the robotic boat.
The only parts that could be considered from the “Bottom Up” approach were the cosmetic parts
which were created beforehand and brought in as an afterthought rather than planned into the
grand scheme of the robotic boat (Rails, Steering Wheel, Steering Base, and the Flag)

13. A diagram visualizing our process is included below (you may have to zoom in to read):
Assembly Mates / Sub Assembly / Mates:
[1]- Flush/Mate Constraints: Hull top face to Hulltop bottom face, Hook bottom face to
Hulltop top face, Cabin to Hulltop, Rail to edge of Hulltop (2 sides), Servo Mounts top
face to Hulltop bottom face, Steering Wheel to Steering Wheel Base, Steering Wheel
Base to Cabin, Flag bottom face to Cabin top face, Propeller to Propeller shaft face.
[2]- Pin Joint/Tangency Mate (same axis constraint): Gear cylinder to Hulltop hole, Flag
to Cabin flag hole, Servo Mount to Hulltop hole, Propeller to Propeller Shaft, Steering
Wheel to Steering Wheel Base hole.

14. [3]-Free Rotational Parts: Propellers are free to rotate about the Propeller Shaft axis, the
Gear is free to rotate about the Hulltop hole axis, and the Flag is free to rotate about the
Cabin hole axis.
[4]-Angle Constrained/Parallel Parts: The Steering Wheel is perpendicularly (90*)
constrained to the Cabin top. This is done by selecting one of the axis of the Steering
Wheel handles and aligning it with the top face of the cabin. The Servo Mount/Spacers
were flushed to each other and then flushed to the front axis to keep them aligned
properly.
[5]-Fixed Parts: The hull was fixed in space as a reference point for all the other parts.
Appendix: