OHIO University Mechanical Engineering Summary Report: Human Power System for Small Appliances and Machinery

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1 OHIO University Mechanical Engineering Summary Report: Human Power System for Small Appliances and Machinery Appalachian Human Power Brad Bundy Ben Chovan Zach Fetchu Ed Passarrelli Ryan Tedford Will Zaylor Abstract: This project is intended to address the need for portable, sustainable power in such areas as tertiary countries, specifically dealing with mechanically powering the appliances of a chosen client, Constantine Faller, at the Athens Farmers Market. Mr. Faller dedicates his life to supporting his local economy as well as to eliminating his carbon footprint. The design is a simple universal transmission which consists of a frame with two axles supported by bearings on which a stepped pulley system is used to generate the proper speed and torque needed for the appliance. The input and output are universal in nature allowing the user to implement this device as needed to any and all applications. Again the specific goal is to power Mr. Faller s appliances which consist of a coffee grinder, bench grinder, and blender. These appliances demonstrate the device s ability. A bicycle demonstrates the input or drive for the device although other means of input are easily adapted.

2 How It Works: The delivered prototype can operate three different appliances to show the range of applications. The three appliances are a coffee grinder, blender, and a bench grinder. The coffee grinder represents a low speed high torque application, the bench grinder represents a low torque, high speed application, and the blender represents a medium speed and medium torque application. Figure 1: The full setup system Figure 1 shows the system with a bicycle as the power input. The system operates by transmitting the power from the input shaft to the output shaft. Different ratios of pulleys can be used to change the speed of the output shaft relative to the input speed. This allows for different speed and torque characteristics for the output. The input and output shafts are supported on both sides of the pulleys by an internal frame.

3 The Power Take off Unit (PTO) is mounted to a base board which is clamped to a table with c-clamps. This allows the unit to be stable without modifying the table. The base board can easily be modified to accommodate other appliances. The Vertical Adapter (VAD) can be used to power appliances with a vertical orientation. The VAD transmits power between two shafts with a belt and pulley (1:1 ratio). The input shaft is oriented horizontally, and the output is oriented vertically. This change in orientation twists the belt by 90 o. This design allows power to be transmitted between the two shafts, however there is a significant loss of power. The main base board and coffee grinder base and stand have been sanded, routed, stained and coated with polyurethane. This is to ensure protection from the elements and to have an attractive aesthetic. Both frames and tensioner bracket arms as well as the adjustable tensioner lip were primed and painted a metallic color. The casings for both the PTO and the Vertical VAD were primed and painted bright red. This protects the metal components from the elements and has a noticeable aesthetic improvement which draws attention to them which is a key part of Constantine s desire to have this product catch the attention of his patrons as a way to go green. The casing was also bent in several places to eliminate different sharp edges. The lids were cut to fit and rubber dots were added to the casing to reduce vibration noise between the lid and the casing during operation. Further more for additional aesthetic presence the lexane lids for the PTO and VAD were CNC etched with our team name as seen in Figure 1. Figure2: Lid Etching

4 A new coupler was created replacing the set screw type with a hose and hose clamps. This reduced wear and stress on the two shafts and allows for a flexible coupling between the two shafts of the PTO and VAD. The pulley system stayed the same for both the PTO and VAD. The bike stand was improved by re-welding it and adding two matching rubber feet. The resulting system can be seen in Figure 1 and 2 above. The design is small and light enough to be transported by the client, and it can function as a source of power for modified appliances. A coffee grinder and a bench grinder can be powered by the design. The design can also power a blender, however there is a limit to the blenders functionality. Due to power losses in the VAD, the blender cannot be used for chopping, however it can be used as a mixer. Final Design The final design operates the same as the original prototype. It still transmits power from an input shaft to an output shaft through pulleys, and it also tensions the belts with a roller like the original design. In the original design, the frame and the tensioner have a low material cost, but both parts had a high cost of manufacturing. These two parts were redesigned to reduce the cost of manufacturing. Figure 3: Showing the Final Design without Casing The major difference between the prototype and the redesign is that the frame only supports the shafts on one end. This greatly reduces the cost of manufacturing because only one part has to be drilled. This eliminates the precision need to have two parts align. This greatly reduces the cost of drilling and welding.

5 Figure 4: Showing the Redesign of the Frame Next To the Prototype The holes that are drilled do not have tight tolerances. The holes for the shafts are clearance holes, which would allow them to have a tolerance of ±1/16. The holes for the tensioner also have the same large tolerance because the location of the tensioner does not have to be precise. The only thing that must be precise is that the shaft support is perpendicular to the drill while drilling. This is not an unusual or intricate operation, so it does not significantly increase the cost of manufacturing. The second part that was redesigned was the tensioner. This part had a low cost of materials, but most of the parts had to be manufactured. This part was simplified such that only two parts have to be manufactured. Figure 5: Showing the Redesign of the Tensioner. The main part that has to be manufactured is the fixed shaft. This part requires four separate manufacturing processes, but it eliminates the need for three separate parts. It also

6 solves issues with the tensioner becoming misaligned. The simplification of this part will reduce the cost of manufacturing, and it will also reduce the cost of assembly. Assembly of the prototype s tensioner was cumbersome, but the redesign would be easier to assemble because it is cantilevered. The final design reduced the manufacturing cost by reducing the number of parts, and also reducing the need for precision while manufacturing. Cost is also reduced by the simplification of the assembly. This simplification decreases the amount of time to assemble which reduces the cost. Cost of Production Many of the parts used in building the PTO are available online or in stores. These mainly consist of pulleys, bearings, bushings, nuts, and anything that is does not need to be made out of flat or round stock. While this does increase the materials cost, it significantly lowers manufacturing cost. Seen below are the parts necessary to assemble the PTO. Parts that can be purchased have their supplier indicated in parenthesis, and those that are custom made are described in the design drawings appendix. The total cost of the bought supplies is $184.57, and the total cost of the stock required is $ Table 1: Parts List Part Qty Part Qty PTO Frame 1 Shaft Key 1 Bushing (6383k232-Mcmaster) 6 PTO Mount 1 Bearing (7208k52-Mcmaster) 2 PTO Lid 1 3,4,5 Pulley (4X559-Grainger) 1 Lid Hinge (Lowes) 4 4,5,6 Pulley(3LC25-Grainger) 1 Lid Knob (Lowes) 2 1.5" Pulley(6245K11-Mcmaster) 1 Handle (Lowes) 2 3" Pulley (6245K516-Mcmaster) 1 V.A. Frame 1 2" Pulley (6245K514-Mcmaster) 4 V.A. input shaft 1 2.5" Pulley(Tractor Supply) 1 V.A. output shaft 1 Input Shaft 1 V.A. Side Panel 2 Output Shaft 1 V.A. Lid 1 Tension Slide 1 Hose Coupler 1 Tension Handle 1 Hose Clamp (Lowes) 2 Roller Bar 1 1/4" Thumb Screw (Lowes) 10 Tension Bracket 2 1/4"-20 x 1" bolt (Lowes) 4 Tension Handle Pin 1 1/4"-20 Nut (Lowes) 4 PTO Long Side Panel 2 1/4" washer (Lowes) 8 PTO End Panel bolt (Lowes) 8 Snap Ring (97633A200- Mcmaster) nut (Lowes) 8

7 The majority of the fabrication work is cutting the pieces of stock to length, which can be done on band saws and then ground clean thanks to the generous tolerances of the final design. Drilling must also be done in several places, which also falls under the miscellaneous assembly category. Other miscellaneous jobs include the bending of the sheet metal, painting, and general assembly. These tasks are estimated to take 6 hours of labor for an experienced worker, for a total cost of $ There are two primary operations that require skilled labor: welding and turning operations. Welding the frame together and the pieces of the tensioner bar are estimated to take 3 hours if appropriate jigs are supplied. Turning operations must be performed to put snap ring grooves in the shafts, to put a fine finish on the tensioner roller tube, and to etch the lids of the PTO and vertical adapter. All of this is estimated to take another 3 hours of skilled labor, bringing the total skilled labor cost to $ In addition to the man hours necessary for production, an additional $341 cost is expected from basic overhead and equipment costs. The costs are summarized below in Table 2. Table 2: Cost of Production Requirement Cost Bought Parts Metal Stock Miscellaneous Labor Skilled Labor Overhead/ Equipment Total Conclusion & Recommendation The finished prototype is a unit that meets the needs of the customer, however the manufacturing cost is high. Due to the dual-crossbar design of the frame, it was necessary to perform precise machining operations on the shafts and frame. In fiscal terms, this resulted in a high cost of manufacturing. The final design maintains the functionality of the original while reducing the cost of manufacturing. Some of the materials for the final design are more expensive, such as using angle iron rather than flat stock, but the amount of skilled operations for manufacturing is greatly reduced. This reduces the cost of manufacturing and the overall cost of production.

8 In order to improve the performance of the unit, rather than just reducing the cost, it is recommended that future human power transmissions sacrifice portability for increased usability of the overall system. A less portable system would allow users to use an effective flywheel, which would ensure a smoother operation of appliances. This less portable unit would better suit a wider range of people because the product would have the ability to store rotational energy with a flywheel. However an effective flywheel would increase the size and weight of the unit making it less portable, and a less portable unit would not have met the customer s need to be able to transport the unit on a weekly basis. The delivered prototype meets the customers need for a source of power that is portable and sustainable.

9 Appendix: Design Drawings

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