Gate 4 - Product Explanation (Group 24)
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Revision as of 15:59, 30 November 2012
In gate four we reassembled the Cyclo HBB Buddy Box and created a step by step tutorial for others to follow. We also provided an explanation of the mechanisms within our product and we provided three suggestions for changes that could be made a system level.
Project Management: Coordination Review
Cause for Corrective Action
During the reassembly of the Cyclo HBB Buddy Box our group faced many challenges. First and foremost we faced a significant time restraint. Our product required the use of the Machine shop in order to be reassembled. However, the machine shop hours do not coincide with the hours of the dissection lab. This proved to delay our reassembly significantly. We managed to overcome this challenge by working as long as we had to during the few times that we were able to work.
Secondly our group faced the challenge of transporting our product. The HBB Buddy Box weighs approximately 90 pounds and it very unwieldy and hard to carry. We were required to move it from the dissection lab to the machine shop, lift it onto and off of the press multiple times, turn it, support it, and manipulate it in many ways during the course of the reassembly. This proved to be an exhausting and very difficult step to the project. By taking turns, working together, and just accepting that it needed to be done we were able to overcome this challenge.
Finally, our last challenge during the assembly of this project was balancing and finessing the assembly of a few of the subsystems. When we were inserting the ball in the ball bearing case of the shaft (Step 8) one of us needed to suspend the gear perfectly center while the other carefully inserted bearings making sure not to knock any of the out of the track or move the gear at all. The other assembly that was very difficult was the reducer. In order to assemble the reducer we needed to make sure that many loosely connected pieces stayed in place until the entire assembly was complete and the components finally secure. Both of these challenges were very frustrating and required an enormous amount of patience and determination.
Our main unresolved challenge, as a group, is balancing the enormous workload from this course with the work load from our other courses. All of us feel as though our ability to master the material in our other, more fundamental, engineering courses is suffering because of this introductory level course. In order to pass this course we feel the need to pour hours upon hours of our time into this project. Unfortunately this forces MAE 277, a complimentary course, to become a priority over our primary engineering courses - threatening, not only our graduating date, but also our ability as engineers. We understand that the material that we are learning in this course is of a much different breed and,arguably, of equal or greater importance to the material in our other courses. However, upon communicating with other students we are confident that we are not alone in feeling that the goals in the course are overzealous and outside the realm of undergraduate study. We plan to overcome this challenge by doing the best that we can possibly do given the time constraints that we have. We will work incredibly hard, making this project a priority until it is done. We will also accept the fact that we cannot do anything greater than our best given each of our unique circumstances.
We were able to work through our main scheduling conflicts as a group and everybody was able to pitch in during this gate. We accomplished this by being clear about when and where we were going to meet after discussing the options that we all had available to us. Planning, luck, and willingness to sacrifice other courses came in very handy during this gate. We were able to resolve this challenge by admitting that the incredible workload of this course absolutely needed to get done so we did what we had to do.
Over the course of the semester the work load between group members has not been evenly distributed for a number of different reasons ranging from abilities, scheduling conflicts, missed meetings, and desire. This, once again, caused a few of the group members to receive a higher work load during this gate. This discrepancy was not due to the lack of willingness to work in this case, but the lack of expertise in the technical details of the project. Unfortunately, in order to get the gate done in time this could not be avoided. We plan to resolve this problem by redistributing the workload during the final gate, letting the more experienced members review and check the work of the less experienced members before it is posted to the wiki. In this way the workload will be more evenly distributed and the less experienced members will become experts in the project.
Another unresolved challenge was, once again, related to scheduling conflicts. A few group members literally cannot make it to the machine shop during the day. Therefore, the responsibility for assembling every component that required a press fell strictly onto the members that could actually make the meeting. This could not be avoided at all and is strictly due to the many restraints that crop up during academic projects. We plan to resolve this problem by redistributing the workload to make up for it during the final gate.
Product Archeology: Product Explanation
Upon dissecting and reassembly the Cyclo HBB Buddy Box it is clear that it was originally assembled by a machine. Many of the parts require a press, and the ones that do not still require very precise fits. Also, the difficulty level of some of the steps indicates that it would be too time consuming, too costly, and too frustrating to be assembled by hand. Finally, while we were assembling the HBB Buddy Box we noticed that there were many areas in which it would be far too easy to damage the product while assembling it by hand. Using robotics and machinery to assemble this product would allow for very precise and extremely challenging steps to be done quickly and more cost effectively. The utter weight of this product alone is an indicator that machines were used to assemble this product. It would be dangerous and extremely cumbersome for employees to be moving, flipping, and otherwise handling this product during the assembly.
- The assembly was exactly the same as the disassembly in reverse order.
The key component of the SMCyclo Helical Buddy Box is the parallel helical gear mechanism. A gear would be similar to a lever with the added feature of rotating continuously instead of rocking back and forth through a short distance. The parallel helical gear’s function is to transfer the rotational energy that is produced from the reducer. The rotational energy is transferred to a shaft with a helical gear fused around its diameter. The angled teeth then grip onto the angled teeth located around the diameter of the gear. The gear then transfers the energy applied to the shaft which is statically locked with the gear due to a key and a key slot that is shaped on the inside diameter. This rotational energy is then transferred up the shaft to whatever application is necessary.
The relationships for a gear are based on the diameter, the number of teeth on each gear and the rotational velocity of gears. With helical gears, the tooth of each gear is set at a distinct angle. This angle is dependent on the amount of noise created, stress tolerances, and the maximum torque that can be applied to each tooth. Due the flexibility of this variable, the designs of each tooth can be modified for multiple applications and load capacities.
For all necessary equations refer to the Equation Sheet from Boston Gear.
Revision 1: Spurred gear with ceramic ball bearings
When this product was received we assumed that due to a broken seal, this product then becomes useless and “irreparable”. Our assumption was correct due to the time and cost needed to repair a broken seal isn’t worth the downtime of a large operation. The actual failure was due to the fragmenting of steel due to a ball bearing failure. With this revision we would not only change the shape of the gears used within the gearbox, but also the material used to create the ball bearings.
Spurred gears are far more efficient and much cheaper to make than the complicated design of a helical gear. Ceramic ball bearings are more expensive but can operate at much higher temperatures after being treated. This increase in stability decreases the chance of failure.
These saving in cost can then be transferred over to the use of ceramic ball bearing instead of steel ones thus, decreasing the chance of failure. Further analysis would need to be taken understand the specification changes needed for these saving to be maximized.
Revision 2: Belt Drive
This product revision call for the use of a belt drive to replace the gears used within the casing. By using a high strength chain or Nitrile rubber and looping each end around fixed axial cylinders with varying diameters (dependent on ratio of speed that is needed to be reduced) a belt drive may be extremely cost effective.
Although the percentage of failure is increased with this new system, maintenance of this device would be almost negligible in comparison to the SMCyclo HBB by allowing access to movable parts much easier to achieve thus making it easier to replace these failed components. This will allow the company to save more than 10x the cost, at about $150.00 dollars and 15 minutes of down time per repair v.s. over $1,000 and over 3 hours of downtime to replace a gear box.
Revision 3: Syncronous Belt Drive
Synchronous belts(also known as timing belts) Are belt drives that have teeth that match up in unison with the pulley while rotation occurs. By appling this belt system and using helical teeth, similar to the products original design it can also, similarly to the original design, provide a quiet and highly efficient system to transfer rotational energy. Synchronous belt drives remain at an energy efficiency of 98-99% over the life of the belt. A proven, viable alternative to standard belt drives, V-belt drives, and roller-chain drives, they are economically smart design decision across a variety of industrial applications.
Again, as a belt drive system, although the percentage of failure is increased with this new system, maintenance of this device would be almost negligible in comparison to the SMCyclo HBB by allowing access to movable parts much easier to achieve thus making it easier to replace these failed components. This will allow the company to save more than 10x the cost, at about $150.00 dollars and 15 minutes of down time per repair v.s. over $1,000 and over 3 hours of downtime to replace a gear box.
Revision 4: Roller Chain Drive
Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire and tube drawing machines, printing presses, cars, motorcycles, and bicycles. It consists of a series of short cylindrical rollers held together by side links. It is driven by a toothed wheel called a sprocket. It is a simple, reliable, and efficient means of power transmission.
Though chains have a shorter life span than gears it is similar to belt systems in that it allows for easier access for repairs. This opens up the opportunity to repair the component rather than replacing it. Saving more than 10x the cost, at about $200.00 dollars and 15 minutes of down time per repair v.s. over $1,000 and over 3 hours of downtime to replace a gear box.
Revisions 2, 3, and 4 similarly follow the same GSEE factors. It allows globally for any industry to easily provide maintenance to the product due to the ease of access to the important subsystems. They also provide an economical advantage due to the reduced pricing of the necessary components used to provide the transfer of energy. These savings can then e past on to the consumer.
As for revision 1 the economic factors come into play when failure is analyzed. Since this functions at high temperatures and continuous stress failure isn’t common, but the chance of said failure can be reduced thus increase the serviceability that Sumitomo Technology can provide to their consumers.