An Introduction Into the Benefits Of

An Introduction into the Benefits of

Fully Mechanical Governors

Over Their Electromechanical SystemsCounterparts

Brian J. Katerberg, Senior Mechanical Engineering Student, CalvinCollege

Andrew J. Vander Moren, Senior Mechanical Engineering Student, CalvinCollege

Engr 315, Control Systems, Prof. Ribeiro

Abstract— Due to the lack ofelectricity electrical hookups and electrical know-howexperiencefound in many third world settings, a system designed for operation in the third world will be best suited for the culture if it does not include electrical components. This year a group of four seniors including myself the two authors of this paper are designing a kit style mill to be designed and built in the United States then converted into a mobile kit that will be able to easily be delivered to such places as Kenya where they will be unpacked and assembled. The mill referred to earlier is a mill designed to remove the seed and chaff from the amaranth plant and then separate the seed from the chaff in order to provide high quality grain. One of the primary areas of concern lies in the separation of the grain from the chaff as there is not much size difference and not an extreme weight difference thus setting tight tolerances on the fan speed.

Index Terms—amaranth, fan speed, fanning mill, mechanical governor, speed-control, speed regulation

I. Introduction

n the United States we are so used to having electricity that we sometimes forget don’t realize what it would be like to live without it. It seems that the lack of experience toward a life without electricity causes engineers in the United States to design things that don’t integrate adequately into the culture that they are intended for. My Our senior design team is trying to keep this in mind as we work on developing a mill to help process grain in the third world country of Kenya. While in the United States it would be very easy to use an electric powered, or even gas powered, system with complex moving parts to perform every step of a particular process without anyone needing to be involved; the samethis is not true in other portions of the world. While a breakdown of complex components will cause some delays in the United States as the new part gets made and shipped to the plant, other countries fully relying on that part will have to wait much longer as someone travels to assess the problem, then gets the equipment to make the part, and then some time later provides the farmer operator with a the replacement part. Though it is possible to go through this series of steps, it is much more of a hindrance in other countries then it is here where we can get things shipped ‘same next day’ many timesquite easily.

II. Technical Details

With most systems used in the states in which a given shaft is required to spin at a certain speed, electronics are used to not only monitor the speed but also make adjustments to it. This can be done in several ways one of which is through the use of a tachometer which measures the speed of a spinning shaft. Often this is done with an optical reader thus not adding any extra resistance to the system. A processor hooked up to the tachometer determines whether the shaft is moving too slow, too fast, or just right, in relation to some reference speed. In response to this reading, the governor processor then sends a signal to bring about the necessary changes to pull the system to the desired speed. A system like this one requires only asome fairly simple circuitry, with a motor, tachometer, potentiometer, a series of transformers, and some sort of voltage source (see Figure 1). While this system is not very complex by our standards, we must remember that what we design is rarely done for people with the same level of experience that we havethis is not being built for us, and in this case, but rather the system is being designed for those a people group that are is unfamiliar with electricity in general and are almost guaranteed to not have any ability to fix a system of this nature when something goes wrong with it.

Figure 1 Sample Tachometer Circuit[18][17]

With electrical components being nearly impossible to fix in these third world settings especially with the level of electrical know-how that the locals are likely to have, it is important not to includeto avoid these in our design. Instead of using these electrically based systemsdoing it might be wiser to usethis,some sort of mechanical systems are used in there place, , however even this can be dangerous. In order to make a mechanical system function in the same way that the electrical system would have functioned would require very complex components most likely taking up a lot more space then the electrical components would have inhabited. This in itself will add a good deal of weight to the system making it cost more and be harder to distribute. While the mechanical components could be built smaller that to reduce shipping costs it could increase the cost of machining them as they parts would have higher tolerances and then would be more fragile. This High levels of complexity, like electrical circuits, is also something that should be avoided when designing something for these third world settings. While we are often quite used to the idea that people from third world countries are likely to not have electrical know-howaxcess, we often assume that they have no mechanical background as well, which is not true. While they don’t have a vast mechanical background they still have a higher mechanical background then some people credit them with. don’t tend to think about the fact that they often don’t have a vast mechanical background either. Based on what we have been told by some missionaries to Kenya, it is our teams understanding that the mechanical abilities of the Kenyans we are hoping to design these mills for is also quite low [3], [4]. While they might be able to repair simple basic wooden parts it is quite certain that they would not know how to, or have the equipment to repair any sort of complex system, wood or metal.

III. The Incentive

It is important that steps be taken to not simply provide the Kenyans with up-to-date equipment, but rather to help fuel their own ability to build up their own economy. One way that this is can be done is through helping them develop their agriculture. By helping the Kenyan people grow and harvest a cash crop such as amaranth more effectively we are able to help the Kenyans develop themselves. When people go into third world countries and simply provide the people living there with what they think is needed to help them improve their quality of life, it doesn’t usually solve their problems. A combination of resources, time, and patient guidance are what will help put a country back on its feet.

Figure 2 Threshing Amaranth

Figure 3 Winnowing By Hand

Because of the setback that these people have endured because of being neglected for so long it is important that steps be taken to not simply provide them with up-to-date equipment, but rather to help fuel their own ability to grow. One way that this is can be done is through helping out in developing their agriculture. By helping the Kenyan people grow and harvest a cash crop such as amaranth more effectively and efficiently, we are able to help the Kenyans develop themselves. When people go into third world countries and simply provide them with stuff it doesn’t solve problems it often just temporarily reduces them. In order to develop a country, however, one can not expect that simply dumping more stuff into the country will solve the problems; instead it is often time, patients, and love that help put a country back on its feet.

Figure 2 Harvesting Amaranth in Kenya

At the present time missionaries working in Kenya with such organizations as CRWRC (Christian Reformed World Relief CoalitionCommittee) and PCD (Partners for Christian Development) have helped prove the feasibility of growing large amounts of amaranth in Kenya. One Now that the feasibility of growing the amaranth has been proven the next problem that is presently faced is how to handle all of the grain being harvested. Currently the grain is harvested and cleaned by hand in a very labor intensive and time consuming process. The current cleaning method for example requires that the grain heads be beaten on the ground with a stick in order to knock the seed and chaff off of the head. After this has been done, the seed/chaff mixture is tossed in the air on little screens allowing the chaff to be caught by the wind and blown away. This cleaning takes a large amount of time and even then does not provide the quality that is desired. In order to make this process more feasible, it would be ideal to replace the slow seed cleaning process with a more automated one that works more effectively. While this is the most time consuming portion of the entire harvesting process, improving the threshing process would also be very beneficial to the Kenyans that are towill receive these mills.

While it would be nice in the eyes of most Americans to have a fully automated system, this can be lessis less then desirable in to manyin third world settings. Many in Kenya are very willing to do physical work while some other cultures are not as willing. By fully automating these mills, the farmers are less likely to feel that they have contributed as much and thus do not feel they have the same level of ownership that they used to have when they did everything by hand. So, while we feel it is nice to have things more or less run themselves, others do not feel the same way. One other reason that makes it harder for the Kenyans to accept the fully automated systems is that the farming is such a large part of their life and taking away their mills would take away a large part of their life. If these automated systems were all implemented at once, the things that the farmers used to spend their time with would be taken from them, By fully automating these mills, the farmers don’t feel like they have contributed as much and thus to not feel they have the same level of ownership that they used to have when they did everything by hand. So, while we feel it is nice to have things more or less run themselves, others don’t feel the same way. One other reason that makes it harder for the Kenyans to accept the fully automated systems is that the farming is such a large part of their life. Additionally, if these automated systems were all implemented at one moment all the things that the farmers used to spend their time with would be taken from them, leaving them with the decision of what to do with their time.

IV. The Concerns

As pointed out in Section II. using an electrically based system would add levels of complexity that can not easily be resolved by the Kenyan people; in the same way, complex mechanical systems would require a higher level of maintenance then would easily be provided by people with little machining background. With these two options being blocked, we are left with needing a very simplistic system that is light weight, easy to use, low cost, and does a good job at processing the grain. As I already pointed out, using an electrically based system would add levels of detail that can not easily be resolved by the Kenyan people; additionally, complex mechanical systems also provide for a system that would be hard for the recipients to care for as it really needs. With these two options being blocked, we are left with needing a very simplistic system that is light weight, easy to use, and does a good job at processing the grain. Unfortunately this combination of things ideals does not come together easily. For example, a system that is cheap and simplistic is not likely not going to do an adequate job at processing the grain while a complex system that can adequately process the grain will not be light weight or easy to repair. In order to make a good design we have to make some value judgments. For example, is it more important for the mill the work effectively or be simplistic; is it better to be small or to be capable of handling high volumes? For these two issues we felt that while neither extreme was completely ideal a mix that leaned towards being effective and capable of high volumes seemed to be a more favorable goal.

One thing that these old mills did was provide multiple gear ratios to help provide greater ease in achieving consistent fan speeds, however the operator was the one determining how fast to spin the crank. With the operator acting as the closed loop portion of this system there is quite a bit of variation in quality that will get better with experience. It would be very nice if consistently good results could be achieved by different people no matter what their experience level is.

seemed like the ideal mix.

V. The Current Mill

While many villages still winnow seed by hand, some have received Clipper Fanning Mills like the one seen in Figure 4.These millscurrently being used for processing amaranth seed in Kenya have two layers of precisely sized screen, the first allowing anything the size of the seed and chaff and other smaller things through while sending the larger stuff out a waste chute. The second screen keeps the seed and chaff on top while letting the fine dust through. After this sorting is done, the seed and chaff falls into a vertical shaft that has a flow of air running up and out the top.

Figure 4 Clipper Fanning Mill

This air stream lifts the chaff and sends it out the upper chute while the seeds themselves fall

Figure 3 Current Fanning Mill

down and are collected at the bottom. These mills work quite a bit better faster then the manual traditional process of sifting tossing the seed in the air, but due to the high cost of the screens and the cost of shipping something so large and heavy, these mills do not work well for being built in the US and then shipped overseas as several organizations are hoping to do. Additionally the current mills are made out of plastic wood causing them to have a much more limited life as boards wear or even rot. Another thing plaguing these mills is that there is a lot of back and forth motion. Because of all of this vibration, the mills wear down much more quickly then if all of the motion was cyclical. In order to make milling more simplistic, another thing that was done was to use wooden pulleys instead or real gears. These wooden gears do make the mills cheaper but they are also less precise and require more maintenance.

VI. HISTORY OF GOVERNORS

The Scottish inventor James Watt is credited with inventing the first device that adjusted the input to a system relative to the system’s output [2]. This device is called the flyball governor. This invention stems from Watt’s interest in the newest invention of his time, the steam engine. One of the major causes of steam engine failure was due to over working/over revving an the engine. Watt’s’ flyball governor addressed this problem and enabled the steam engine to adjust its speed automatically regardless ofin response to the load applied to the system.

Figure 5 Watt’s Flyball Governor [2]

A flyball governor is comprised of a shaft that is driven by the device in that is intended to be controlled. The shaft is spinning at the speed of the shaft that is to be monitored. This shaft is positioned vertically and has two weights that hang down from the shaft via small rods. As the speed of the shaft increases, the weights connected to the shaft move outward due to centrifugal force. The faster the shaft moves; the farther out the weights move. A special linkage is connected to the top ends of the shafts holding the weights. This linkage moves relative to the position of the weights. This linkage can be connected to the throttle of the engine that is spinning the shaft the governor is attached to. When the engine is at rest, the throttle of the engine is wide open. As the engine begins to speed up, the weights move outward which causes the throttle to close slightly. If a load is suddenly applied to the engine, the speed of the engine slows down which causes the weights to fall down closer to their rest position. The movement of the weights supplies more fuel to the engine therefore allowing the engine to speed back up to the desired speed.

Once the load on the engine is removed, the engine begins operating at higher speeds than it should. The weights then move even higher. This movement of the weights decreases the amount of fuel supplied to the engine. Less fuel being provided to the engine limits the amount of power the engine can make produce and therefore slows down the speed of the engine until the equilibrium speed is achieved once again.