Preliminary Detailed Design
Team Vision for Preliminary Detailed Design PhaseSummary:
Plans during this phase:
- Select Material
- Design & Simulate Gear Profile
- Finalize Dimensions
- Order Samples
- Test Different Staining Methods
- Visit Robin’s Library
- Visit Pittsford Lumber
Accomplishments during this phase:
- European beech was selected for wheel
- White oak was selected for the frame
- Beech samples were ordered
- One method of stain was tested
- Visited Robin’s Library in UofR
- Visited Pittsford Lumber
- Created Bill of Material
- Created Test Plans
Feasibility: Prototyping, Analysis, Simulation
Wood ExpansionAccording to the Wood Handbook released by the Forest Products Laboratory of the U.S. Department of Agriculture, dimensional change coefficients can be used to estimate wood shrinking or swelling based on the type of wood, the change in moisture content, and the direction of the wood grain – functionally, whether the wood is quartersawn or flatsawn.
Assuming that a typical climate controlled room varies in humidity by about 4% a 14 inch gear will expand about a tenth of an inch if quartersawn or a quarter of an inch if flatsawn. We will incorporate climate data for the Robbins Library and the Cary Archive when modeling to account for changes in humidity.
We plan on running tests on different sized gears to see how this expansion will impact the tooth meshing. We likely will end up over-tolerancing the gears to account for the changes in size.
Wood expansion will also impact how the wood needs to be processed. For 6/4 in wood, we will likely purchase 8/4 inch wood and step mill it down to size over several weeks to give the wood time to acclimate before each cut.
Wood StainingSome preliminary testing was performed on historical staining methods.
A Stain was made using steel wool and 5% apple cider vinegar. The Vinegar rusts the iron in the steel wool creating a black oxide (Fe3O4) that stains the wood. As the stain solution sits, more steel rusts and pigmentation increases, this leads to a darker stain.We tested the stain after “brewing” for 30 minutes, 1hr, 2hrs, 6hrs, 12hrs, and 24hrs. As well as getting darker, the stain seemed to get redder, probably from the production of red iron oxide (Fe2O3), which forms in higher oxygen environments than black iron oxide.
Additionally, two different methods of applying the stain were used. On the top, excess stain was wiped away immediately after the stain was applied. On the bottom, the stain was left to seep into the wood.
It appears as if wiping off the stain might result in a more uniform coloring, but the results were somewhat irregular. Further testing on staining technique should be done using larger samples.
Drawings, Schematics, Flow Charts, Simulations
Central Axle Drawing
Pinion Axle Drawing
Wheel Face Construction
Bill of Material (BOM)
The live document can be found here.
Unbalanced Load Testing:
- Engineering Requirement: Bookwheel should not turn of its own accord.
- Instrumentation: Weights:
- Start with no weights on bookwheel.
- Sequentially place 5lb loads on 4 of the 8 cradles.
- After placing each weight,release break and turn wheel so that the weight is at a 90’ angle
- Activate the break, if the wheel does not turn, add another weight and try again.
- Record number of weights required before wheel
- Engineering requirement: Bookwheel should not tip when subjected to a 150lb force 5 feet from the ground.
- Instrumentation: Bathroom Scale.
- Strap bathroom Scale to the side of the bookwheel.
- Push on the scale by hand until the bookwheel begins to tip.
- Record force when edge starts to lift.
- Engineering requirement: noise in operation should be less than 60db.
- Instrumentation: Decimeter (Volume meter)
- Place decimeter 10 feet from base of bookwheel.
- Release brake, Start turning bookwheel at approximately 10rpm.
- Record Gear noise and volume.
- Activate brake, Record brake noise and volume
Load Capacity Testing
- Engineering Requirement: Book Cradles should be able to support 20 lbs
- Instrumentation: Weights
- Place loads on bookwheel to determine weight capacity of books.
- Place 5 lb weights on a cradle.
- Keep placing weights until the total weight on the cradle is 30lbs.
Design and FlowchartsThis section should continue to be updated from your systems level design documentation.
After talking with the University of Rochester, we considered a few different gear profiles. Three profiles that we considered were the circular tooth profile, a simple trapezoidal tooth profile, and the modern Involute profile.
The circular profile has zero interference and constant velocity profile, but has varying pressure line resulting in less smooth movement and irregular resistance. The zero Interference profile allows for the gear to be used with no clearance, resulting in no play.
The trapezoidal tooth profile is easy to manufacture and has interference necessitating clearance between the teeth, resulting in some play in the gears, it lacks constant contact and a moving pressure line resulting in less smooth movement and “clacking” as the teeth impact.
And the involute profile is a constant pressure profile that has interference, so clearance must be put between the teeth, resulting in some play in the gears. The gears are very strong and smooth, but the mathematics behind modeling them had not been discovered before the 16th century.
The involute profile above was generated using http://geargenerator.com.
Shown here is a mesh between two 12 toothed circular profile gears, the gear has no interference, so the front and back of the tooth are both in contact at the same time.
The live document can be found here
Plans for next phase
- Maher Abdelkawi
- Order Materials
- Help with prototyping gear profile
- Help with break design
- Speak to woodworkers on campus regarding joinery
- Go to training in the construct
- Ian Kurtz
- Refine the BOM (3 hours, 4/12)
- Be trained on CNC router in the construct (1 hour, 4/12)
- Find steam bender (2 hours, 4/17)
- Calculate required spring constant for brake (2 hours, 4/12)
- Finalize brake design (4 hours, 4/17)
- Matt Nygren
- Test Staining Techniques and formulation" (3 hours 4/11)
- Be trained on CNC router in the construct (1 hour, 4/12)
- Cut test Gear Profiles and check meshing (4 hours 4/17)
- Investigate Brake pad/surface materials (3 hours 4/5 )
- Reese Salen
- Update CAD model dimensions and include gear profiles
- CAD model motion study
- Get trained on CNC router
- Research axle hubs
- Research hardware available in the period