156B Week 3

Overview of Status of Analysis, Design, Fabrication, Tests, etc.

Design

Team and sponsor has decided upon the concentric bearing design. Being that it would be more robust, fewer parts, potentially shorten the fabrication time, and lowers risk of failure compared to the roller design. However, it will be more costly due to the large bearings as the heart of the design.

Analysis

Team has undergone analysis for the materials necessary to construct various parts of the self-reacting frame and load frame as well as the bearing housing and its constituents. A motor torque analysis was done to figure out required motor torque. 

Accomplishments from Previous Week

• • Reduced design options to a final design using large diameter bearings - Everyone

  • Created Parts list for self reacting table and loading frame - Jorge/Sergio

  • Finalized CAD design for machine -Jorge/Sergio

  • Analyzed stresses on C-channel and load Frame- Jorge

  • Inquired for quotes on metal pricing- Jorge

• prepare CDR presentation for sponsor Sergio

• Contacted various bearing manufacturers (SKF, Browning, Timken, DODGE, and many others) and asked application engineers about best bearing type for 4 degrees misalignment - Jerry

• Designed a swivel bearing housing to accommodate misalignment (see Figure 2) - Jerry

• Decided upon using tapered spherical roller bearings and acquired a range of spherical roller bearing prices - Jerry

• Decided to use an adapter for fixing the bearing to the shaft - Jerry

• Made a CAD and ran a simple stress analysis of the bearing housing using Solidworks - Jerry

• Designed and made a CAD of motor mount assembly - Brandon

• Performed an analysis on drive belt design to find suitable belt for the belt drive - Brandon

Goals for Next Week (list names after each item). Use specific and measurable objectives.

• Begin to order parts if design is approved - Brandon

• If parts begin to come in, start on manufacturing process - Jorge/Sergio

• Look into RPM sensor- Jerry

• Look into electronic portion of drive assembly - Brandon/Jerry

• Decide upon motor type and corresponding conroller - Brandon

• Compile a bill of materials and/or parts list ready for purchasing - Everyone

• Begin drafting up various parts needed to be machined - Everyone

Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)

• Notes from meeting: 4/13

  • Not too many more design issues

  • update design for motor mount

  • create design for bearing mount

  • call SKF/ others about bearing specs/prices

  • look into cycle counting solution

Instructor Comments from Last Meeting and Actions Taken to Address these Comments  (indicate date of comments and if via email or in person)

From 4/10:

All,

I think we should abort the roller design.  Feel free to talk about it at CDR, but please don’t devote much more time to it.  I think your time is better spent finalizing a design w/ bearings.  The roller design might be a bit cheaper, but I don’t think the end product will be a well working machine.  I think that it is worth paying the money for the bearings as they are the key element to our entire design.

Jerry,

Can you please call some bearing manufacturers today and find out if there is any way we can save money on the bearings?  I think you just need to give them a ballpark idea of the operating conditions (say 1000lb of radial load, 600 RPM, X° angular misalignment, +/- 0.0XX in shaft tolerance) and ask them what the best solution is.  I am very curious to hear what they say.  I was talking to Ted last night, he mentioned that we could have the shaft (test article) precision ground so we can get a tolerance of ~ +/- 0.001 on the OD if need be.

Brandon,

Can you do some calculations regarding the belt drive?  If we use a timing belt, then the tension is not so critical, but we need to make sure that the belt can handle the amount of torque we are putting through it.  We could also consider using a chain drive (like a bicycle).  Or, I think we could probably use a V or flat belt too.  If we go with a V or flat belt then we need to calculate the required belt torque.

Jorge/Sergio,

Please continue the design of the load frame and support structure.  I was thinking about your idea of the diagonal cables, and thought we could make some triangular gussets as shown on slide 3 of attached.  The more I think about it, I don’t think it’s worth the added complexity.  I did some simple hand calcs on the design shown on slides 1 and 2, and with a 0.75” plate we are looking at about 10ksi of bending stress in that plate (A36 steel yields at 36ksi, so that would be adequate).  I think we should just keep it simple and go with the design shown on slides 1 and 2.  We can just drill a hole in the middle of it for the tensioning bolt.

If possible, can you please send me something tonight, so I can give you some feedback.  At least some kind of progress report, but hopefully some screen shots of your CAD.

Thanks,

Greg

Jerry: Already called multiple manufacturers to hone in on our best bearing contestant. Also contacted distributors in San Diego with quotes on the bearings and adapters.

Brandon: Wrote up a report on belt tension and pulley ratios necessary for our belt drive application.

Jorge: Simplified the load frame design and chose materials that suites our design. Performed a simple analysis on the load frame

Sergio: Redesigned the self-reacting table to fit the motor assembly as well as the simplified load frame. Got quotes on the list of materials to fabricate the support structure.

Comments from Other Students in the Class (indicate date of comments and if via email or in person)

Risks and Areas of Concern

• • Bearing Housing design feasibility - need more information on whether bearings can be utilized in this fashion. All application engineers are either against or lacking a strong position about this special use.

  • Delay in purchasing parts due to incomplete design

  • Pulley drive feasibility

  • A lot of expensive parts, which will be very costly to replace if broken: motor and bearings

Resources or Information Required but not Available

Schedule

• • CDR with ATA today (4/16)

  • Begin ordering parts as of tomorrow (4/17)

Budget (list amount spent and amount remaining)

• • None

Progress on Report and Webpage

• • Wrote up a rough draft on the follow sections: Background, Review of Existin Solutions, Statment of Requirements, and Delieverables

  • Website will be updated after the CDR. Presentation and documents on analysis will be posted. All images collected so far will be uploaded soon.