Detailed Design Part II
Table of Contents
During the detailed design phase of this project our team divided and conquered relevant mechanical and electrical design tasks as detailed below.
Mechanical Systems Design
Building off of the first iteration of detailed design the team went back to the drawing board to finalize their design and include the proper validation prior to purchasing and building.
Motor MountingA critical component of testing on the dynamometer is properly mounting the motor so that it can couple with the loading motor of the dynamometer. After the first iteration design it was seen that the original design failed Finite Element Analysis and needed to be redesigned. After minimizing critical areas of stress concentration and adding thickness to the material the motor mount was redesigned as seen below.
The motor mount will be welded together using a two sided fillet weld along the line of attachment from the upright to the base plate. The gussets will be welded in the same fashion.
After creating an assembly and defining the proper attachments, an FEA analysis can be completed to identify areas of failure and need for improvement upon the initial design. FEA analysis was completed using the following parameters:
Motor Weight = 45 lbs
Rotation Speed = 4000 RPM (maximum case based on motor specifications and applied current and voltage)
Force on Mounting Holes = 100 N/m (greatly exceeds the distributed torque that will be seen on each hole but is representative of a worst case scenario if the user did not use the assumed eight screw hole pattern.
As seen in the image above the results showed that the maximum displacement did not exceed 0.03mm. There is no place within the mount that exceeds the yield strength of the material during testing therefore the material remains in the elastic region and no plastic deformation (permanent deformation) should be observed. Overall the design under worst case loading had a factor of safety of 2.5 which is an acceptable FS based on the risks associated with failure.
The Assembly was placed on the dynamometer CAD as a visual to how it will look when the build is completed. It should be noted that the 4" X 4" hole pattern on the dynamometer does not go throughout the entire mounting plate and the holes on the back portion of the plate will not suite our needs with the motor we are using. In order to combat this the team is inquiring about the possibility of adding the addition hole pattern throughout the mounting plate so that there is ample room to mount the idler and run the chain to the loading motor.
Powertrain Transportation and HoldingAnother key facet to the design of this system is being able to easily transport the powertrain system from the Hot Wheelz team room to the testing facility. Using an industrial cart, the team will modify the cart to hold the batteries, controller and motor during transport and the batteries and the controller during testing. Seen below is the cart sourced to hold components.
The cart features additional mounting areas so that the team can add a place to mount the motor easily during transportation and easily detach the motor to assemble onto the dynamometer. A mount was designed to hold the batteries in insulated boxes on the cart rigidly. The batteries carry the greatest load on the cart and have been designed to remain as close to the center of the cart for mass neutralization of the cart and ease of maneuvering the cart during transportation. The cart base will feature a hole pattern so that if any components need to be moved during the build or in future projects the cart and components remain modular.
After making contact with the company the manufacturer CAD models are being sent to the senior design team so that the final assembly can be made and analyzed to ensure that the weight of the components does not over stress the cart and its capabilities.
Motor to Dynamometer CouplingOriginally the senior design team was going to utilize an existing idler system but upon review it was decided we would need to design our own system. As seen below this is what currently exists in the dynamometer room that will be used as benchmarking for the new design.
First and foremost the gear ratio of the Hot Wheelz car has to be known in order to properly select the pinion and the gear as seen below. The pinion and gear will use a chain to transmit load between the Hot Wheelz motor and the dynamometer.
The main functions of the idler system are to take up slack in the chain and provide a user-adjustable tension force to the chain. These two functions ensure that the chain stays securely in place during our testing. The idler sprocket features an inner bearing that allows it to spin on a rod freely. As seen below, the idler system features a platform that can be secured at a given height by the user. The platform height adjustability allows for the removal of slack from the chain. Under testing, the idler sprocket will experience a downward force from the chain and an upward force from the two springs. Increasing the compression of the springs increases the tension force acting on the chain. The base plate of the idler follows the concept of the motor base plate; slots in the base plate allow for movement and adaptability to ensure the sprockets on the Hot Wheelz motor, the dynamoneter, and the idler are in alignment.
Electrical Systems DesignThe electrical components of this project consist of many different aspects from sourcing the proper sensors to collect the necessary data to integrating with the Dyne Controller that is currently featured on the dynamometer.
DAQ SelectionProfessor Wellin has donated the NI cDAQ-9172 for our use in the project. After weighing pros and cons, it was determined that this was the best solution in terms of cost, risk and time.
You may find the manual for NI cDAQ-9172 here
Sensor Sourcing and MountingIt is critical that data is collected on key components of the powertrain system including voltage, current, battery and motor temperature, rpm and torque.
Sensors that have been sourced to collect measurements. Highlighted in yellow is a component that is dependent on the DAQ device the team is able to acquire.
Now that the sensors have been sourced, the team needs to work together to properly mount the sensors to the current design so that the sensors remain safe during test and transportation.
System Wiring DiagramThe wiring diagram and PCB diagram from previous phase was updated to the diagrams below, to reflect changes in design. It was determined that a dedicated thermocouple DAQ will be acquired for data acquisition purposes. Wiring harness designs are also presented in order to get ready for building in MSD II.
P15280 Guide to Operating DynoThis quick start guide was written by the P15280 senior design team to assist any team working with the dynamometer and to provide clarification on anything that may not be up to date in the official Dyn-Loc IV user manual and quick start manual.
Link to the guide is located here: KGCOE Dynamometer Lab Quick Start Guide
- Please note, this document is continuously updated as we find different tips that may be useful for future teams to use.
Detailed Design ReviewOur team assembles a conclusive presentation at the end of each review to summarize our work which is located here: Phase 5: Detailed Design Review Presentation Part II
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