Gate 4 - Product Explanation.

Cause for Corrective Action:

Following gate 3, we feel that we are working well, however there are certainly things to improve on. Our plan to utilize constructive criticism has worked well because it allows for many issues to be resolved before submission, however we clearly need more input based on our grade from gate 3. Also, we feel that our communication is good, and each member of the group is aware of what the other members expect of them, but it is up to but it is up to them to complete their assigned tasks. We have worked hard to make sure that all members are completely informed on what everybody else is working on. Because of this one member can contact another member to ask questions that both would face. In addition, our plan to have multiple people revise submissions has also been very effective. We have found that it is very helpful to have several sets of eyes review each part in order to maximize accuracy and detail.

One of the main problems that we face is anticipating which parts of the product are emphasized in grading. On gate 3, we had one member spend several hours creating CAD drawing of different pieces only to find that these drawing were only worth 5 points. In retrospect, it would have been much more effective to allocate his time towards a component worth more points. To solve this problem, we will analyze point distribution much closer and attempt to put the most effort in the heavily graded pieces.

As we finish out the project, we are content with how the group is interacting, and we will strive to maintain this relationship through the end of the semester.

Product Reassembly:

Scale for Difficulty Rating:

The difficulty rating for each step ranges from 1 - 3. In this scale, a "1" is the most simple and usually consists of just screwing a component in place. Similarly, a "3" is the most difficult and could require a significant amount of time and problem solving. The difficulty scale has been formed specifically for this leaf blower meaning no step would be harder than a "3", or easier than a "1".

Tools Required for Reassembly:

• Flathead Screw Driver
• Phillips Screw Driver
• 20 Piece Metric Standard Hex Key Set (Allen Wrenches)
• ½ inch Combination Wrench

Note: All Allen screws referenced to are the same size.

Leaf Blower Reassembly Steps

This table gives step by step instructions on how to reassemble the leaf blower.

#	Step	Explanation	Time Required	Difficulty Rating	Picture
1	Connect piston to crank shaft.	1. Slide piston back onto crank shaft (no fasteners should be used). The piston was most likely originally assembled by a factory worker. The assembly and disassembly of this component are the same and it should go back on very easily. No tool is required.	15 seconds	1
2	Attach combustion chamber to engine housing.	1.) Slide combustion chamber over piston. 2.) Attach to engine housing with two Allen screws. This would have been originally assembled by a factory worker and the process to reassemble is the same a disassembly. Requires a 5/16 Allen wrench.	3 minutes.	1
3	Replace black plastic engine cover.	1.) Slide the black plastic engine cover over the crank shaft. 2.) Secure with two Allen screws. This step in very simple. Again, we feel this would have originally been put in place by a factory worker and removal is no different than assembly.Requires a 5/16 Allen wrench.	2 minutes.	1.
4	Attach carburetor support.	1.) Reattach the black plastic carburetor support to the engine housing using two Allen screws and a 5/16 Allen wrench. This is a very simple step that would have been originally been assembled with a power tool. Reassembly is the exact opposite of dissasembly.	3 minutes.	1.
5	Reassemble and replace pull cord unit.	1.) Recoil spring and insert it into the steel casing. 2.) Insert the spring and steel casing into the plastic housing. 3.) Screw the two plastic pieces of the housing together with a Phillips head screw driver and two Phillips head screws. This step can be very difficult because the spring is hard to recoil. When taking it apart, recoiling the spring was not involved. This was done by a machine when the product was originally assembled.	20-30 minutes.	3.
6	Reattach magneto.	1.)Replace the magneto by screwing it to the engine housing with a 5/16 Allen wrench and two Allen screws. This step is very easy. It was most likely originally assembled by a factory worker and should go on the same way it came off.	1 minute.	1.
7	Attach pull cord assembly.	1.) Slide the assembled pull cord unit onto the crank shaft. This piece is not connected with a fastener, but the shape of the crank shaft will hold the unit in place. No tools are required. This was most likely put in place by a machine when originally assembled. replacing this piece is no different than removing it.	1 minute.	1.
8	Replace spark plug.	1.) Screw the spark plug back into the threaded hole on the engine casing. This step requires a crescent wrench. In the factory, this would have been assembled by a machine. Once again, disassembly was the same as reassembly.	2 minutes.	1.
9	Replace fan.	1.) Reattach the fan by sliding it over the crank shaft and securing with 1 steel washer and 1 1/2 inch nut. You will need a 1/2 inch wrench to tighten the nut. This would have been assembled by a machine in the factory. Removing the fan was the same as replacing it.	3 minutes.	1.
10	Lay engine in housing.	1.) Set the assembled engine unit into the green outer housing. 2.) Run the pull cord handle to the back of the unit and out the small hole on the back of the housing. It can be tricky to line everything up, so the unit sits in the housing properly. No tools are required. This would have been set in place by a factory worker when originally assembled. Removing this piece was easier because no time had to be spent lining up the engine supports and pull cord.	5 minutes.	2.
11	Replace heat guard.	1.) Slide black metal heat guard into the proper slot on upper right side of engine casing. This requires no tools and would have been done by a factory worker. Taking this piece off was no different than putting it on.	30 seconds.	1.
12	Attach muffler.	1.) Reattach the muffler over the black heat guard with 5/16 Allen two Allen screws. This attachment pinches the outside plastic housing which secures the engine unit in place. This was no different than disassembly and would have originally been done by a factory worker.	2 minutes.	1.
13	Replace gas tank.	1.) Set the gas tank in the molded opening behind the engine casing. 2.) Run the fuel lines through the small hole at the top of the outside housing towards the carburetor. This step requires no tools or fasteners. Again, this was no different than disassembly and would have originally been done by a factory worker.	1 minute.	1.
14	Align fan cover.	1.) Lay black plastic fan cover in the molded slot at the bottom of the unit. This will allow the cover to be pinched between the two outer housing pieces. No fasteners or tools are required. This would have been done by a factory worker and there is no difference between assembly and disassembly.	1 minute.	1.
15	Apply left piece of outer housing.	1.) Lay the left side outer green housing on top of right side and assembled engine. Be sure that the handle and fan cover are in place so they fit evenly between the left and right pieces of housing. No fasteners or tools are needed for this step. Again, this would have been originally assembled by a factory worker. Reassembling this piece was much more difficult that removing it, because when removing it, lining up the screw holes was not a factor.	5 minutes.	2.
16	Connect outer housing.	1.) Connect the two pieces of green housing with a 5/32 Allen wrench and eight 5/32 Allen screws. This piece probably would have been originally assembled by a factory worker with a power tool. Assembly and disassembly are no different.	6 minutes.	1.
17	Attach carburetor.	1.) Reattach carburetor to black plastic support using two very long Allen screws and a 5/32 Allen wrench. 2.) Attach gas lines to small tubes on carburetor. Should be very similar to removing the carburetor and would have been originally assembled by a factory worker with a power tool.	2 minutes.	1.
18	Attach carburetor cover.	1.) Attach purple carburetor cover using a Phillips screw driver and two Phillips screws. This is no different than removing it, and it would have been originally put in place by a factory worker.	2 minutes.	1.
19	Attach muffler cover.	1.) Secure muffler cover using a Phillips head screw driver and two Phillips head screws. This step is very simple and was the same as disassembly. The muffler cover would have been originally put in place by a factory worker.	2 minutes.	1.
20	Attach tube.	1.) Slide the circular end of the tube into the circular opening at the front of the outer shell and secure by tightening hand screw with fingers. Should be the same as disassembly and it would have been originally assembled by a factory worker.	1 minute.	1.
21	Attach gas cap.	1.) Screw gas cap onto gas tank using fingers. This should go on very easily just as it came off. Again, this piece would have been originally attached by a factory worker.	30 seconds.	1.

NOTE: One should plan to spend two to two and a half hours when reassembling this leaf blower. Depending on problems faced, up to 3 hours may be required.

Problems Faced During Reassembly:

Rewinding the spring:

One problem we encountered during the leaf blower reassembly was putting the spring back into the pull cord unit. The spring gains a lot of tension as it is wound up and becomes very difficult to hold as it is wound small enough to fit in its place. It is clear that this piece would have been originally assembled by a machine when the product was made. In order to overcome this, we simply kept trying different ideas until it worked. After many failed attempts, we finally got it back together. One person held the center of the spring with pliers while another wound it up. It took us over an hour until it worked, but it eventually went back together.

Attention to detail:

Another problem we had was not something technical such as rewinding the spring. When reassembling the leaf blower, we went ahead and forgot to put a part in. We were assembling the engine and realized we forgot to put in the magneto. We took the casing, cylinder and piston out and attached the magneto. We then went ahead with the reassembly until we were almost finished until a group member noticed the piston lying on the far end of the table. The piston was the first step to reassembly so we had to go all the way back and put it in. We reassembled the second time even more carefully making sure we did not forget any parts, and eventually got it all back together. It is important to make sure no detail is missed when reassembling the leaf blower.

Design Revisions (System Level)

Electric Starter:

The first change recommended on the leaf blower would be to use an electric starter as opposed to a pull cord. An electric starter would influence the societal factors of the product by making it more user friendly. Simply plugging in the leaf blower and pushing a button, such as one that says "START" as shown in Figure 1, is a much easier task to perform rather than priming the engine and pulling the cord, which may have to be done multiple times when dealing with an older engine. The product’s target audience is a middle class home owner, who will usually look for simplicity when purchasing a product such as a leaf blower. Adding an electric starter will require some minor design revisions of the outside shell. Altering the position of the entire motor to fit with the electric starter will be costly, so it may be more efficient to design the electric starter around the current position of the motor.

Figure 1 Possible design of an electric starter

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Clutch:

While using the leaf blower, it is very possible for a situation to arise that calls for the user to set down the leaf blower for a brief moment without wanting to turn the engine off. However, air would continue to blow out a high speeds. Not only is it a safety hazard, but it might ruin neatly piled leaves and debris, creating more work for the user. This is a societal factor that addresses safety and the desires of the consumer. A good solution would be to install a clutch with two gears. The engine is currently directly connected to the fan through the piston rod. Instead of a direct connection, a second piston rod could be installed (one connected to the engine and one connected to the fan). These two piston rods could be connected through the two gears that are controlled by the clutch. This allows the engine to become temporarily disconnected to the fan, stopping air flow. In addition, if the two gears are of different diameters, it would also provide additional air flow. If a smaller gear is connected to the engine and a larger gear is connected to the fan, the angular velocity of the fan will be greater than if it is directly connected to the engine. Perhaps a gear such as the one on the right in Figure 2 could be attached to the engine and the gear on the left could be attached to the fan.

Installing a clutch and gear system, however, will require major design revisions internally. The center of the fan must be offset from the piston rod coming out of the engine, as they will no longer be directly connected. This in turn might call for a design revision of the outter shell. These revisions may be costly and should first be researched. The company must figure out several things:

1.) The cost to redesign the product

2.) Whether or not the revisions will add to manufacturing costs

3.) How much of a demand a clutch and gear system in a leaf blower would be for consumers

4.) Finally, comparing the cost to consumer demand and determining if the revisions are worth it

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Back Straps:

A third recommendation would be to separate the engine housing from the blower tube with a short hose. By separating the two, back straps could be added to the engine housing in order to carry it on one’s back, as shown in Figure 3. The flexible hose connecting the engine to the blower tube would allow for free range of the tube with the engine being carried on the user’s back. This influences the societal factors of the product by reducing the human energy input. Carrying the majority of the blower’s weight on the back rather than with the handle makes the product easier move and use. The reduced weight required to carry by hand when using the product makes directing the tube much simpler. Again, this improvement would heavily favor either business owners who use the blower for extended periods of time, or middle age people who might become fatigued while supporting the weight of the entire leaf blower.

In order to implement this revision, almost the entire outter shell must be redesigned. The leaf blower must be comfortable on the user's back. Therefore, the entire side that makes contact with the user's back should be flat and smooth. It may be benificial to add a piece of padding to cover that side of the leaf blower's shell for additional comfort. If the entire shell is redisgned, internal components may also require revisions, such as placement of the fan and therefore placement of the motor to line up with the fan. These revisions may be costly, however the societal factors that back straps address (comfort, ease of use, etc.) are major selling points and could be used to promote the product and increase sales.

Figure 3 Possible addition of back straps