ShingleBot Mechanical Design Mark J. Underhill September 6, 2016

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)

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?

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

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

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.

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.

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

Thrust Actuator Selection Mechanical Drawing Package (Thrust Mechanism) Thrust Actuator Selection The Nook ND8-24-10-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 ND8-24-5-B-305-POT-IP65 ball screw version is available 450 lbs. of force 67 mm/sec (2.64 inches/sec)

Thrust Actuator Selection Mechanical Drawing Package (Thrust Mechanism)

Thrust Actuator Selection Mechanical Drawing Package (Thrust Mechanism)

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

Thrust Mechanism Baseplate Mechanical Drawing Package (Thrust Mechanism) Tapped holes are tapped for 10-32 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)

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

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

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 089037008705 Table Saw Anti-Kickback Pawl

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

Wedge Mechanism Actuator Mechanical Drawing Package (Wedge Mechanism) NOOK ND8-24-5-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.

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

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

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

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

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.

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