Cisco 1RU Standardization

Exterior Bonderson Projects Center
Cisco currently designs a variety of custom chassis for different types of servers, routers, and switches. Our senior design project aims to reduce the number of custom chassis Cisco develops by standardizing the perimeter mounting locations for the printed circuit board assembly on the chassis.

Our Team

We are the Cisco 1RU Standardization team. We are mostly from California (and Hawaii).

Sarika Singhal

Secretary of Defense

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John Liu

MATLAB CODER

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Leia Tashiro

MATLAB Coder

I am a 5th year general concentration Mechanical Engineering major. I will be graduating this spring and plan to pursue a mechanical design engineering position in the Fall.

Bryce Young Circle

Bryce McNeil

not matlab coder

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Acknowledgements

Thank you to Professor Schuster for always accommodating our project group.

Thank you to Cisco for initially reaching out and giving us the opportunity to work with a larger company.

Our Project's Videos

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Our Project's Digital Poster

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  • Withstand maximum torque input of 400 lb-ft.
  • Must incorporate a limited slip differential (LSD).

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Parallel shaftlayout was chosen for the following reasons:

  • Createsacompact layout and housing design.
  • Utilizes helical gearing to maintain better tooth contact between meshing gears. The helical gears were also selected for noise reduction at high speed operation.

Other design choices to note:

  • Rectangularhousing uses flat plates bolted together for ease of assembly and manufacturing.
  • Tapered roller bearings to help support the axial loads produced by the helical gears.
  • Material choice of HT 8620 for gears to provide the strength of gears without oversized face widths.
  • Shafts of HT 4140 material for good machinability and strength.
  • Axial forces can bedirected into shoulders on shafts while the vehicle moves forward.

Direction of axial forces generated by the gears while the car is in the forward drive position

Shear and moment diagrams helped us find the points of highest stress on the shafts. From there we were able to pick an appropriate material for the strength requirements.

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Figure 1

Rendered CAD model of assembled drivetrain.

Figure 2

Exploded view to show all components included in the fully assembled drivetrain.

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This CAD model allowed for dimensions of various components to be finalized and aided in determining tolerances necessary for manufacturing and assembly.

This project is sponsored by...

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The solid blue line shows the torque output curve of the REMY HVH250-115 motor to be used with our drivetrain.

Theoretical vehicle top speed and traction capabilities which account for various vehicle parameters.

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Torque test set up with the input wrench of the right and the output on the left. A digital torque sensor was used to measure the torque at the input and output shafts.

The linear correlation of torque input to torque output features error bars to indicate the uncertainty of the measurements.

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TorqueTest- Our design was verified by testing the torque increase through the drivetrain. We used torque wrenches to measure the torque at the input and output shafts. In theory, the torque should increase by 8.04 times from the input shaft to the output shaft. However, we found the torque increased by 7.36 times. This discrepancy is due to mechanical losses in the drivetrain.

Speed Reduction Verification-The speed reduction was also verified, and as expected, the gear ratio matches what we designed the gears for, coming to 8.04:1.

Oil Leakage Test- In order for the drivetrain to function properly, it needs to retain nine quarts of oil. The oil is necessary to reduce friction and wear between meshing gears. To ensure proper sealing we used RTV sealant to seal the housing plates, filled the drivetrain with oil, and let it sit overnight. After a 24 hour period, we inspected the housing with no signs of leakage.

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Specifications
Weight -89.4 lbs
Overall Reduction -8.04:1
Dimensions -19.25” X 9.25” X 12.5”

Custom Components

  • Aluminum Bearing Mounts
  • Aluminum Housing Plates
  • Helical Gears –8620 Case Hardened Steel
  • Heat Treated 4140 Steel Shafts
  • Steel Housing Reinforcement Blocks

Stock Components

  • Ford 8.8” Traction-Lok Limited Slip
    Differential
  • SKF and Timken Tapered Roller Bearings
  • SKF Rotary Shaft Seals

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SharpellTechnologies is currently “gutting” the interior of their 2002 BMW 330ci test vehicle, to the extent where the backseats have now been removed. This area will be utilized to house the battery pack modules as well as the electricmotor that our drivetrain will be coupled to. Our drivetrain will be mounted in between the rear axle shafts of the prototype vehicle,allowing for power to be transmitted to the rear tires.

The drivetrain will be used in the Sharpell Technologies test vehicle to help aid in the testing of their new battery technology and newly developed motor controller.

Electric vehicle battery comprised of many individual battery pack modules.

REMY HVH250-115 motor capable of producing 310 lb-ftof torque

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Improvementsto be made if drivetrain were to be re-designed:

  • Optimize drivetrain’s size and weight by reducing the sizes of shafts and gears.
  • Utilize a smaller differential assembly to allow for smallergear sizing.
  • Utilize better material heat treatment processes to allow for stronger and smaller componentswhile still meeting the desired factor of safety.
  • Reduce the rotational inertia of shaft assemblies by slotting the gears faces to reduce excess material and weight.
  • Design and cast a housing for a more compact drivetrain unit.

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