Group 3 - Homelite Fluid Pump (Gasoline Powered) - Initial Assessment
This Homelight pump was manufactured during the 1980’s. Following the 1970’s energy crisis, the latter part of the 1980’s saw a major surplus in crude oil. Fuel was also readily available in modernized countries such as North America, where it was sold. At this point in time, environmental issues weren’t of high concern in relation to the world we live in today, so emissions weren’t considered in the design process or product review. Overall, this was sure to benefit sales of this gas-powered product. The product was intended to reduce manual labor (and increase productivity) as a compact, home-friendly device. With that said however, the makers may have seen issues designing an affordable product optimizing material usage with performance; during our product analysis, our group will consider what we find to be good and bad designs of the product.
The intended use of the product is to transport liquids from point A to point B in an efficient manner, by means of a gasoline powered motor. The product can be used for both home and professional use (in small town Departments of Public Works, for example). Examples of typical applications for both classes of user include DPW workers using this product to draw excess fluid out of a trench, while a homeowner may use this product to pump water from their swimming pool at the end of the season.
The main purpose on the gasoline powered pump to convert chemical energy stored in the gasoline into kinetic energy of the fluid to be pumped. However, there are many different energy conversions that must occur throughout this process. These different types of energy can be broken down into the following categories:
- Potential chemical energy
- Electrical energy
- Thermal energy
- Translational kinetic energy
- Rotational kinetic energy
- Kinetic energy of the fluid
The transformations of energy are depicted in Figure 1: Energy Flow-Chart and the steps are explained here:
- Step 1
- Energy stored in the chemical bonds of the gasoline is introduced into the cylinder after the gasoline is atomized through the carburetor where it then is ignited by a spark in a process called combustion. When the gasoline is ignited there is a rapid change in temperature. Thus, the energy is now thermal energy.
- Step 2
- The increase in temperature of the cylinder (Thermal Energy) creates a proportional increase in pressure instantaneously because its volume remains relatively constant for a moment. This pressure applies a downward force to the piston which then translates in the direction of the applied force. Thus the energy is now translational kinetic energy.
- Step 3
- As the piston moves with translational kinetic energy, it forces the engine's crankshaft to move as well. Due to the design of the crankshaft, it's motion is rotational, causing the translational kinetic energy to become rotational kinetic energy.
- Step 5
- Part of this rotational energy is then kept internal to the engine system and transformed into electrical energy. This electrical energy is then sent back to step 1 in order to create the spark mentioned.
- Step 4
- The last step is this rotational energy in the engine is than transferred into the pump housing through a direct shaft drive (Engine/Pump Coupling) which is connect to a impeller. This impeller spins the fluid causing it to gain kinetic energy. The fluid is then ejected out through an outlet and is now in the form of kinetic energy of the fluid.
The scale of the fluid pump's mechanical complexity is perceived to be substantial. This complexity can be described in terms of the individual parts, and also in terms of the interactions between assemblies of parts.
Complexity in terms of the machine's individual parts can be considered both high and low. The number of individual mechanical parts that are going to be found inside of the engine and pump is expected to be in the hundreds. Solely from the basis of number of mechanical parts involved in the design, it can be determined that the fluid pump is indeed mechanically complex. However, not every part is innately complex. The measure of complexity of individual parts is expected to be relatively low. What we expect to find is that the individual parts will have an upper limit to their complexity aligned with that of a spring. Although the mechanical complexity of parts may not be too extravagant, on a higher level much more complexity does exist.
When we take a higher level perspective on the machine's design, we can see that it is very complex as a whole, with many parts being required to work at perfectly timed moments in order to properly function. What this describes is that although many of the individual parts are very simple, the interactions between the parts are very complex. This complexity can be taken to be of different forms. Examples of complex part interactions include the kinematic motions which can be found in the cyclic motions of both the engine's and the pump's rotational assemblies, precisely-fitted parts like the needle and jet of a carburetor, and the working mechanism of the recoil pull-start.
In the pump, it is apparent that a variety of materials have been used in the product. The materials that are clearly visible in the product's exterior include:
- Pump and engine housings (cast); Various other components that are metallic, but non-magnetic are assumed to be aluminum.
- Covers and guards (formed sheet); Fasteners; Throttle linkage
- Pull-start handle; Carburetor choke adjuster; Few other miscellaneous parts.
- Other Materials
- The spark plug contains a ceramic; The spark plug wire is shielded by a polymer insulation; The air filter contains a foam filter element.
Within internals of the product Group 3 expects to find that a majority of the parts that aren't clearly are made of steel. This is due to steel's properties that contribute to good durability and machinability characteristics considering the mechanical environment inside the engine and pump. Other materials that cannot be seen, but are suspected to exist include a copper conductor inside the spark plug wire, possibly some brass (or other smooth metal) bushings in the carburetor, and some sort of gasket-material that is used to seal the housings of the engine and pump assemblies.
User Interaction Profile
User interaction can be experienced on two differing levels which are operational usage and performing maintenance procedures.
The typical use of this product is not at all aided by the implementation of labels containing instructions for use. This isn't a problem at first considering that even for the inexperienced user finding the fuel tank cap to fill it up and figuring out how to pull the pull start handle to turn the motor over shouldn't be too much of a problem. But a crucial step to getting the engine to run includes operating the choke on the carburetor, and this actuator is not labelled at all. Another crucial step to proper operation of the pump is to prime the pump with fluid. Running the pump without priming it first can cause two things to happen. Firstly, the pump's internal mechanism can be damaged. Also, the pump doesn't suck fluid without being primed. The lack of Instructions and warning labels regarding proper use lends itself to the argument that this product's interfaces are not intuitive and that the product is not easy to use for the inexperienced user.
Another attribute of this products typical use that is universal to users of all experience levels includes the ease-of-transport of the device. Whenever a portable fluid pump is implemented, it can be assumed that the device will necessarily be moved to and from its work site. This product is relatively hefty and its carry handle makes it uncomfortable and cumbersome to transport.
Aside from the products typical use we will also take a look at its maintenance procedures. The first of mentionable maintenance procedures has to be cleaning the air filter. Air filter maintenance, among no other product operations, receives a sizable red label that is clearly visible on the product. The suggested filter maintenance intervals are clearly communicated, however instructions are not evident. However, users who are slightly experienced should be able to locate the filter and figure out how to remove it for cleaning (one flat-head screw fastens the filter box to the product). Another maintenance procedure is changing the engine oil. This process is very similar to the required maintenance on similar products and is otherwise no more complicated or confusing.
In summation, the ease of use and maintenance for this product by a user is greatly dependent upon the experience of the user. Inexperienced users may possibly fail to properly use this product because of its lack of labelled instructions. And experienced users may have very little trouble using the product once they become familiar with its design. However, the product's cumbersome carry handle is an uncomfortable interface for everyone.
Product Alternative Profile
An example of an alternative can e taken to be a product that performs a similar function but with and alternative power source and form factor such as API's Solar Water Well Pump . The Solar Well Water pump is a water pump that is able to pump several gallons of water per minute. The advantages of this product are that it is energy efficient and effective throughout across various environments and locations. The Solar Water Well Pump is able to go to submerge 200ft with flow rates of 1.5 to 3 gallons of water per minute. Additionally, the pump is weather protected, easy to handle, and has a solar charged battery. The battery is able to operate 24 hours a day whenever the pump is needed. There are multiple ways to assemble the pump according to how much water the individual wants to pump. This could be powered by one single solar panel in most locations depending on what way you assemble the pump. The Solar Well Water Pump is easy to use in home; it has an on or off toggle switch which is less hazardous to adults and children. However, with a lot of these technical problems there are bound to some type of problems happen. If the Solar Water Well Pump cracks or drops it will cause the water to flow inside the pump and corrode the inner elements. All of the components vary in expenses with the size of the battery an individual needs, solar panel size, etc.: The Solar Water Well pump is energy efficient but very expensive. This product ranges from around $1500 to $2000.