Problem Statement:

Renewable energy, especially wind energy can be an unpleasant sight in residential and commercial areas. Engineering a more efficient wind turbine, whose power transmission uses a toothed pulley, is the goal for this assignment. Maintaining an affordable, sleek, and efficient design are the specific constraints of the design. 

Assumptions About the Problem

• The consumer wants a low cost product
• The consumer wants an efficient product that can power their home
• The product must be suitable for commercial and residential use
• The ease of use and maintenance requirements for the product must be reasonable

Pugh / Decision Matrix

Link: Decision MatrixLinks to an external site.

Matrix Factors:

Aesthetics: Aesthetics remains an important factor of the decision matrix due to the fact that it is one of the core bases upon which this project was started on. An Aesthetically pleasing design is a key factor, however the three different modules will look almost identical from the outside. The inside of the wind turbine is what will look different. All of the designs will look similar, however due to the way that pulleys work, they are somewhat more aesthetically pleasing than a simple geared system, giving them the small leg up in the decision matrix

Ease of installation / maintenance: Since this is a consumer grade product, it must be relatively easy to maintain and get serviced in the field. The installation process must also be kept in mind, since it is intended to be used in suburban areas. The modules that consist of pulleys are easier to maintain than the geared system. This is due to the fact that if the weak link (the belt) breaks, it can be easily replaced, however if the gear shears or breaks, the unit will be down for a much longer period of time. (T = FD, F = MA)

Lifespan: The lifespan of the unit was also one of the core constraints of the project. The turbine must be sustainable, with a 10+ year overall lifespan. The turbine must also be able to withstand 100mph sustained winds, and weathering typical of the southeast United States (humid, hot, cold, rainy). The gear has the potential to have a longer lifespan than the units with belts, however the differences are not too significant, as shown by the similarly scored performances in the decision matrix. The gear also has the potential to get buildup in between the teeth from various weather events, if the outside case is to become compromised. (Failure stress / Allowable stress)

Energy transmission efficiency: This is one of the heaviest weighted categories, due to the fact that the whole point of having a wind turbine is to create energy. Having the most efficient wind turbine is the ideal situation. A geared design would have the least drivetrain loss of the entire system, with a regular slip pulley having the least. The mix between the two (pulley with teeth) will combine the efficiency of the geared system, with the safety of the pulley system. It is a good compromise between the two, providing the system with an adequate mix of efficiency and lifespan / ease of maintenance. 

Cost of production: This is another heavily weighted factor, because this wind turbine is intended to be consumer grade; That is it must be economically feasible for the regular person to justify this purchase. In order for the manufacturer to make money and provide the product at a reasonable price, the cost of production must be kept to a minimum. The geared system will require a casting, and forging process, with multiple refinishing steps to ensure the proper fitment of the teeth at a 90 degree angle between the turbine blades and the driveshaft. This can get expensive quickly. The slip pulley would be the cheapest to produce, as it is just a simple pulley and belt. The pulley with teeth will be a combination of the two processes, without as much manufacturing needed as the straight up gears. The respective scores are indicative of these facts. 

Solutions:

Top Pulley FRDPARRCLinks to an external site.

Bottom Pulley FRDPARRCLinks to an external site.

Pulley Belt FRDPARRCLinks to an external site.

The solution for the wind turbine is a design that uses a pulley with teeth. This solution is the most effective at maintaining the given constraints while utilizing resources to the fullest extent. The model can be found below, and it should be noted that a few specific modeling techniques were used to create the parts and assembly. These techniques include: Circular and linear pattern features to create the teeth on the pulleys and the belts, shell features to add to the ease of design for the case around the turbine, offset cut and extrude features to utilize the existing planes within the model, loft features for the blade design, and fillets to reduce stress concentrations. A few design techniques were also used: Bearings within the top and bottom shafts to hold the pulleys in place as they rotate, pulleys with teeth, threads, and a set screw with a corresponding flat plane to mate the turbine blades onto the output shaft. The material selected for the pulleys with teeth, is a forged aluminum. This comes from a cast piece, of which the teeth are then forged to allow for a higher stress tolerance. The belt to be used in this setup consists of rubber and Kevlar fiber reinforcement, to allow for a higher strength than a traditional rubber timing belt.

Gantt Chart:

Lessons Learned: 

The lessons learned from the previous assignment (modules) involving CAD also carried over to this assignment. It is sometimes easy to have an idea in your head of how something needs to operate, however modeling that idea in CAD can take some time and finicky procedures to be done properly. It is also important to be referencing your previous assignments and designs, to understand the original intent of the project. Sometimes it is easy to get caught up in a design change, even though it may be going against your original intentions.