Build, Test, Document
Build, Test, Document DirectoryClick here for the link to the Build, Test, Document repository
Redesign & Diagrams
The original design was reworked to the current revision, as shown below in the schematic drawings. Many of the edits were simple, making angles 90 degrees, using the same parts to ease assembly and fabrication of the frame.
One major feature that was added to simplify the design was the aluminum plate on the drive side of the Better Water Maker. Utilizing one piece here ensured alignment of holes, bearings, and most importantly, gear teeth.
Additional support was added to the support of the second bearing interfacing with the pinion shaft.
Due to price concerns, approval to modify the gear from the current model of the BWM was obtained. Due to the threat of tear out in the plastic gear, the two "pressure plates" were added to either side of the gear to provide more surface area and greater clamping force. Additionally, the pressure plates will be pressed onto the fabricated pinion shaft to increase possible transmitted torque through high contact friction.
Better Water Maker, uninterruptable power supply
This modular component allows for seamless operation of the BWM. In addressing the difficulty of maintaining a high RPM to overdrive the motors providing the power to the Pump/Lamp assembly and the frustration from the 10 second delay of the pump initiation that takes place at restart, we have design an uninterruptable power supply (UPS).
The modular device is connected between the generator and the pump/lamp assembly. With the toggle switch flipped the pump/lamp assembly will initiate and run off the battery power. When the user then energizes the generator to the required RPM outputting above 14V, the voltage comparator will energize the relay and disconnect the battery, powering the pump/lamp assembly from the generator. Simultaneously, 300mA from the generator will be charging the sealed lead acid battery. When the user drops below the required RPM, and the voltage drops below 14V, the voltage comparator will de-energizes the relay and switch to battery power in less than 3ms for a seamless transition and, without restarting the pump delay, as would normally happen.The device features a battery management system that allows for the battery to be charged from any 12-15V source, not just the current generator designs, for instance: solar panels. The device also implements a boost converter to allow for a cheap and common 12V sealed lead acid battery to be used, but provide the 13.5V minimum required by the system.
This component is not required for operation, however, its flexibility as a power storage device as well as a mechanism to create a less frustrating user experience makes it a valuable and versatile add-on.
|Harbec supplied us with their Buck converter and pump control designs which we utilized in the electrical system. One recommendation for future teams would be to make the pump control board more efficient. There were significant power losses in the board. Shown below are the buck converter and pump control board schematics respectively.|
Bill of Materials
Harbec Generator Circuit BOM
Harbec Pump Control BOM
Test Plans & Test Results
Final test plan, as well as performance vs specifications. Test plans were created for each Engineering Requirement as established on the Problem Definition page. Each will have a test or a series of tests to determine if all the requirements have been met, are exceeding or falling short of expectations or are within the acceptable range.
Boost Converter Simulation Results
Comparator Simulation Results
When the voltage from the motors drops below the output voltage of the boost converter, the relay switches and the power to the pump and light is now supplied by the battery. This operation is shown below in the simulation results.
Electrical Testing of Treadle System
The output of the motors and the regulated output at the buck were tested for using an oscilloscope. As shown below the voltage of the motors appear sinusoidal in nature with a peak to peak voltage of approximately 13.2V and a DC offset of about 18.4V.
The output of the motors is then rectified and regulated to approximately 14.8V with a ripple voltage of about 1V. The regulated signal is shown below.
VO2 Testing Results
Our system was tested in a fitness lab to see how hard a person would have to exert themselves to produce clean water. About a minute of good results were obtained and are shown below. We were told by the fitness lab director that the CO2 results were the most important. High CO2 levels indicates that the body is relying on anaerobic respiration which means the body is over-exerting itself.
Assembly InstructionsAssembly Procedure
1) Press bearings in main drive shaft support and intermediate shaft support
2) Press one way bearings on drive shaft with PVC spacers
3) Bolt triangular sides together using ¼-20 bolts
4) Bolt cross braces for triangular sides together using ¼-20 bolts
5) Bolt drive shaft supports in place in triangular frame using ¼-20 bolts
6) Bolt intermediate shaft support into gearbox side triangular frame using ¼-20 bolts
7) Bolt motor supports in place with spacer blocks using ¼-20 bolts
8) Bolt lateral base supports in place to gearbox side triangular frame using ¼-20 bolts
9) Bolt motors to motor support plate
10) Install square side of drive shaft into bearing in drive shaft support on gearbox side
11) Install main drive gear
12) Install retaining pin for main drive gear
13) Install shaft collar on other side of bearing support from main gear
14) Install intermediate shaft in intermediate shaft bearing with pinion bearing on the outside of the frame
15) Install intermediate gear on intermediate shaft
16) Install split ring collar on intermediate shaft
17) Bolt split ring collar to intermediate gear
18) Bolt in lateral base support cross brace using ¼-20 bolts
19) Bolt second intermediate shaft support to lateral base support cross brace using ¼-20 bolts
20) Bolt handles on
21) Bolt handle cross support on
22) Bolt pulley mount to handle cross support
23) Install drive shaft
24) Bolt second triangular frame to base lateral supports
25) Bolt pedals around one way bearings with clamps
26) Jump up and down in excitement
Problems & Solution Tracking
|Hole locations do not match||Slot cut holes to fix error||Max, Tyler Burns, Tyler Schmidt||Ongoing||End date 4/2|
|Bearing Does not have a P.F. slightly looser||Apply Locktite and let set||Tyler Burns||Completed|
|Metal U bracket might not have enough grab on bearings||Research/ Purchase thin rubber sheet to improve friction||Tyler Schmidt||Ongoing||Due 3/31|
|Handles sharp on edge||Break edges and purchase pool noodle as safety cover||Tyler Burns||Ongoing||Due 3/31|
|Have to cut new PVC spacer, Original spacer too short||Cut a new one||Max||Ongoing||Due 3/31|
|Have to add 2 new holes to bottom frame to make room for bracket attachment||Add holes||Max||Ongoing||Due 3/31|
|Bolt interference on various parts||Created Brackets to mount to, changed hole locations||Tyler Burns||Completed|
- ALL PARTS ON HAND, INCLUDING LARGE GEAR, CURRENTLY
DEBUGGING MECHANICAL DESIGN AND ALIGNMENT ISSUES BEFORE
BUILD CAN BE COMPLETED 3/19
- NEED TO ACQUIRE RUBBER SHEET FOR BEARING TO BRACKET CONNECTION
This is one idea that has the potential of working, rope or belt of some kind would be wrapped around the drive shaft and pulled, effectively increasing the frictional force exponentially.
Risk Assessment Charts
Current as of phase 4