P18510: Ramelli's Rotating Reader

Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase


Plans during this phase:

Accomplishments during this phase:

Feasibility: Prototyping, Analysis, Simulation

Wood Expansion

According 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 Staining
Some preliminary testing was performed on historical staining methods.

public/Photo Gallery/Iron_Stain_Setup.jpg

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. public/Photo Gallery/wood stain chart iron.jpg

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

Assembly Model

public/Preliminary Design Documents/pic_WheelAssembly.PNG

Assembly Drawing

public/Preliminary Design Documents/drawing_WheelAssembly.PNG

Frame Drawing

public/Preliminary Design Documents/drawing_Frame.PNG

Central Axle Drawing

public/Preliminary Design Documents/drawing_CentralAxle.PNG

Pinion Axle Drawing

public/Preliminary Design Documents/drawing_PinionAxle.PNG

Wheel Face Construction

public/Preliminary Design Documents/pic_WheelPieces.PNG

Bill of Material (BOM)

public/Preliminary Design Documents/BOM.png

The live document can be found here.

Test Plans

Unbalanced Load Testing:

Test Procedure:
  1. Start with no weights on bookwheel.
  2. Sequentially place 5lb loads on 4 of the 8 cradles.
  3. After placing each weight,release break and turn wheel so that the weight is at a 90’ angle
  4. Activate the break, if the wheel does not turn, add another weight and try again.
  5. Record number of weights required before wheel

Stability/Tip Testing:

Test Procedure:
  1. Strap bathroom Scale to the side of the bookwheel.
  2. Push on the scale by hand until the bookwheel begins to tip.
  3. Record force when edge starts to lift.

Noise Testing

Test Procedure:
  1. Place decimeter 10 feet from base of bookwheel.
  2. Release brake, Start turning bookwheel at approximately 10rpm.
  3. Record Gear noise and volume.
  4. Activate brake, Record brake noise and volume

Load Capacity Testing

Test Procedure:
  1. Place loads on bookwheel to determine weight capacity of books.
  2. Place 5 lb weights on a cradle.
  3. Keep placing weights until the total weight on the cradle is 30lbs.

Design and Flowcharts

This section should continue to be updated from your systems level design documentation.
Gear Profiles

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.

public/Preliminary Design Documents/Gear Comparison.png

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.

public/Preliminary Design Documents/Circular Gear Mesh.png

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.

Risk Assessment

public/Preliminary Design Documents/Risk Assessment.jpg

The live document can be found here

Plans for next phase

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