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Caleb Savard

Shingle Brush

Industrial Device

Skills Showcased

Mechanical Design
Decision Matrices
Sheet Metal
Test Design
Technical Writing

For my senior design project, I worked with a team of 3 others to design, build, and test this device for removing asphalt particles from a shingle production line for our sponsor GAF. At the end of the year-long project, we had determined that brushing was an effective method of removing these particles, succeeding in removing over 80% of them. We were also able to deliver recommendations on bristle type and future testing.


In manufacturing their shingles, GAF applies a coating of asphalt particles called fines.

Sand-like asphalt particles
Asphalt fines applied to shingles

Most of these fines stick to the shingle, but vibrations eventually cause some fines to fall off throughout the production line. This causes waste and mess, so GAF sponsored a senior project team to develop and deliver a quarter-scale prototype to solve the problem.

Ideation and Design

We first reduced our assignment to its component functions: removing fines from the shingle, collecting them in an organized manner, and remaining structurally stable. After researching various related devices and patents, my team and I sketched several solutions we thought were viable. A weighted decision matrix was used to compare the effectiveness of each solution at accomplishing each design criteria. The design direction took the shape of a rotating brush to get fines off the shingle and into a chute. To verify the effectiveness of this design, we mocked up a concept prototype and ran a few rudimentary tests.

Wooden structure with a rotating brush
An early prototype to test the concept of a rotating brush
Brushed shingle
Test results show visible difference between brushed (top) and unbrushed (bottom) shingle.

These proved promising, so we continued toward developing a final prototype. We contacted industrial brush manufacturers for bristle samples and chose the 3 most promising types. We ran hand calculations and FEA on the structure to ensure it could handle the static and vibrational loads.

Deflection Simulation Vibration simulation
Loaded leg deflection (left) was within spec. The first vibration mode (right) occurred at 1750 rpm, well above our operating speed.

Finally, we made drawings from our CAD model and sent them off to our sponsor for approval.

Drawing of industrial device
Exploded view of final design.
Cut sheet
Cut sheet for the shroud.


The main frame was made by GAF with minor changes to our drawings. It was our job to produce the sheet metal parts (since the school has a waterjet), the electronics, and work out any problems that arose.

The brush shroud and chute were cut by a Cal Poly shop technician on the waterjet from our SolidWorks sheet-metal model. Next, we made the bends specified on our drawings using brake. A malfunction during cutting caused one quarter of the shroud profile to be cut about ½” too short, but we bent it as planned and welded on extra material where necessary.

Bent sheet metal shroud
Finished brush shroud.
Sheet metal patch welded into a gap
Repair of the gap left by a waterjet malfunction.

We also designed and fabricated an electrical box using the same techniques. This included vents for airflow, cutouts for controls and readouts, and a lid. Our DC power supply and motor controller would be mounted inside.

Sheet metal box with vents
Finished electronics box.

Finally, we assembled all the parts.

Bolting the chute to the frame
Me bolting the chute to the frame.
Installing the gearmotor
Installing the gearmotor. Bolt holes are slotted to allow for adjustment.
Installing brush
Me installing the brush and shaft on the frame. There was just enough space to slide the coupler together.
Installed electronics box
The electrical box with all the componenets installed. It is bolted to the frame on the opposite side from the motor.
Attaching the shroud
Installing the brush shoud. Clevis pins were used on the sides to hold it in place.

Testing and Results

We wrote 11 test procedures to verify that the prototype met our design criteria. The most important was the Fines Removed and Collected tests, which measured how much of the loose fines were removed from the shingle, and how many made it into the collection bin.

We simulated the pre-brushed shingle surface by sticking fines to the back of a finished shingle using spray-adhesive, then pulling it past the spinning brush and measuring the difference in mass of the shingle to determine the amount of fines removed. After two more passes, the final weight is used to calculate the percent of loose fines removed. This test was run several times for each bristle type, which helped determine the best bristle for the job.

Partly clean shingle
A shingle after being brushed by the prototype. The plywood clamped to one end was used as a handle.
Brush TypeFines RemovedFines Collected
0.022" Level95% ± 25%69% ± 39%
0.028" Level90% ± 24%54% ± 28%
0.028" Crimped87% ± 11%41% ± 14%
Results of the Removal/Collection test. Despite large confidence intervals, the most flexible bristle (0.022") seems to perform the best.


This project was a great opportunity to practice some of the more administrative parts of engineering. Documentation, technical writing, purchasing and budgeting, presenting. It also gave me a chance to practice soft skills like brainstorming with my team, communicating ideas, working with vendors and experts, and keeping the project moving with a preoccupied sponsor. In the end, I am happy with what we were able to accomplish, although I wish we had been able to test the more parameters to better understand the factors of brush effectiveness and longevity.