1. ShingleBot Mechanical Design
Mark J. Underhill
September 6, 2016

2. Basic Concept
A primary mechanism, working on the same principles as a roofing shovel, moves down the roof using a thrusting action
A “wedge”, the simplest of tools, is thrust forward from the main body
An array of teeth, designed to capture nails roofing shovel, provides the leading edge
A pair of anti-kickback pawls prevents the main body from moving backwards when force is applied (i.e. it does not rely solely on gravity)
When nails are encountered, a prying action is used to remove the nails
A slight retraction of the wedge may be necessary at this point; profile TBD
Anti-kickback pawl ($21 in single piece qty)

3. Basic Concept (continued)
The primary mechanism is contained within a vehicle (rover) used to both assist in shingle removal and to transport the mechanism back to the top of the roof after removing a strip of shingles
The primary mechanism “drops” to the roof in order to remove shingles at the beginning of each cycle
The vehicle lifts the mechanism when it needs to travel back up the roof using a simple set of swing arms (essentially a four bar linkage) and a gear motor or other mechanism
Primary Mechanism
Thrust Mechanism
Wedge Mechanism
Models captured in Autodesk Fusion 360
What does RIT use?

4. Basic Concept (continued)
In order to provide basic structural rigidity, a pair of linear guides ensures that the wedge and the main body are mechanically linked
The load on the linear guides is quite low under normal circumstances
When fully retracted for travel, the wedge is well supported
Using a pair of outside guides requires good alignment, but allows use of a single actuator and single feedback device
A fully assembled “table” style pair of linear guides is relatively expensive
Thomson linear guides were selected, purchased, and have been received
SPB12 “super pillow blocks”
ASB12 end supports

5. Thrust Mechanism Detailed Concept
The basic thrust mechanism is illustrated in Figure 1 with the guide extensions removed
Thomson linear guides (pillow blocks, end stops, and round rail) are used to stabilize the wedge mechanism
A Nook ACME screw based actuator provides thrust (ACME used rather than a ball screw based actuator)
The baseplate and clevis were machined in a prototype lab
Not shown: Pawls and glide rails
Figure 1: Thrust Mechanism
Figure 2: With extensions

6. Mechanical Drawing Package
(Thrust Mechanism)
Thomson linear guides were chosen based on the level of detail provided for their parts. They are, however, quite expensive and an alternative should probably be examined eventually.

7. Mechanical Drawing Package
(Thrust Mechanism)
Two 19.5” L, ¾” D style “L” shafts were specified and received from Thomson to complete the linear guide assembly.

8. Thrust Actuator Selection
Mechanical Drawing Package
(Thrust Mechanism)
200 lbs. of thrust is deemed more than a normal human being can regularly thrust
Preferred maximum rate would be several inches per second
A comprehensive search found that force is available but that speed comes at a price premium
24V is preferred; 12V likely boxes the design in too severely
DC brush motors will be used for the prototype
BLDC may be used for the production design
Position feedback needs to be provided by the actuator or separately

9. Thrust Actuator Selection
Mechanical Drawing Package
(Thrust Mechanism)
Thrust Actuator Selection
The Nook ND A-305-POT-IP65 has been selected for the prototype, with an upgrade path to the ball screw version of the same actuator
337 lbs. of force
33 mm/sec
An Acme screw is generally more forgiving than a ball screw
9 amps current at full torque
The ND B-305-POT-IP65 ball screw version is available
450 lbs. of force
67 mm/sec (2.64 inches/sec)

10. Thrust Actuator Selection
Mechanical Drawing Package
(Thrust Mechanism)

11. Thrust Actuator Selection
Mechanical Drawing Package
(Thrust Mechanism)

12. Thrust Actuator Selection
Mechanical Drawing Package
(Thrust Mechanism)
The thrust actuator has been received and is available for inspection as necessary.

13. Thrust Mechanism Baseplate
Mechanical Drawing Package
(Thrust Mechanism)
Tapped holes are tapped for screws
Untapped holes are 0.22” nominal
½” 6061 aluminum plate selected to allow for robust thread engagement and because it was available free
Screws, bolts, washers and lock washers preliminarily selected (McMaster catalog part numbers)

14. Thrust Mechanism Clevis
Mechanical Drawing Package
(Thrust Mechanism)
Manufactured in prototype lab of 6061 aluminum

15. Mechanical Drawing Package
Thrust Mechanism Misc.
Mechanical Drawing Package
(Thrust Mechanism)
Linear Guide “U” Channel
On Line Metals 6061 “U” Channel ( 4”(A) x 2”(B) x 0.23”(C) x 0.15”(D) ) x 2’ long
Note: Length (2’) not depicted to scale

16. Mechanical Drawing Package
Thrust Mechanism Misc.
Mechanical Drawing Package
(Thrust Mechanism)
Pawls
The pawl selected is a purchased part from Craftsman tools. It is intended to be mounted on the baseplate in a “pocket” with a clevis in order to support its intended operation. This modification has not yet been made.
Glide Rails
Holes have been drilled to support three ½” glide rails, intended to be mounted on the bottom of the baseplate, in order to allow the mechanism to traverse objects (such as broken nails) as high as ½”. These rails have not been fabricated (or designed) as of yet.
Craftsman Table Saw Anti-Kickback Pawl

17. Mechanical Drawing Package
Wedge Mechanism
Mechanical Drawing Package
(Wedge Mechanism)
The wedge mechanism is illustrated to the right
It consists of the following elements
Linear actuator
Piano hinges (2)
Wedge pushplate
Actuator mounting bracket/clevis
Wedge plate
Pivot aluminum angle brackets (2)
Wedge actuator clevis
Wedge Mechanism

18. Wedge Mechanism Actuator
Mechanical Drawing Package
(Wedge Mechanism)
NOOK ND B
Actual actuator selection not determined until final mechanical configuration is complete.
Effective ratio determined by plate length and crank arm length. Actuator final selection based on best combination of force and speed.
Need to add a position sensing device since the potentiometer adds more than one inch to this package.

19. Mechanical Drawing Package
Wedge Mechanism Hinge
Mechanical Drawing Package
(Wedge Mechanism)
“Piano” Hinge
Holes and hole pattern not yet defined
Aluminum selected to ease machining concerns

20. Wedge Mechanism Pushplate
Mechanical Drawing Package
(Wedge Mechanism)
Holes and hole pattern not yet defined
Aluminum selected to ease machining concerns
½” plate chosen to simplify mounting / assembly

21. Wedge Mechanism Actuator Mounting Bracket
Mechanical Drawing Package
(Wedge Mechanism)
Holes and hole pattern not yet defined
Aluminum selected to ease machining concerns
Left and right side plates required
Bottom hole acts as the thrust actuator mount while the top hole is the wedge actuator mount

22. Wedge Mechanism Plate Clevis
Mechanical Drawing Package
(Wedge Mechanism)
Holes and hole pattern not yet defined
Aluminum selected to ease machining concerns
Expected to bolt to the wedge plate

23. Mechanical Drawing Package
Rover
Mechanical Drawing Package
(Rover)
The rover is being designed and fabricated by a skilled ME who is also serving as a mechanical consultant
It consists of the following elements
Chassis fabricated from ½” aluminum (part of the same plate that the primary mechanism base plate was fabricated from)
Two brush motor based gear motors
Four spring casters
Weight budget: 35 lbs.
Required to climb a 12/12 pitch roof with a total weight of 100 lbs.

24. ShingleBot Test Facility
Adjustable pitch simulated roofing surface
16’ x 8’ surface
Adjustable by Kubota