Link: Product Dissection Plan

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Contents

Introduction

If the product dissection plan is adhered to closely, then disassembly of the Homelite®, UT 15151 Versatool™, can reduce, and perhaps prevent, unnecessary exertion, ultimately proving minimally labor-intensive. The tools required are few and fairly common, with several exceptions. Furthermore, the total dissection of the product is outlined below along with documentation of exploded views supplied for reference. Each step contains a difficulty rating and a brief explanation of the rationale behind that rating. The difficulty scale (ratings range from 1 to 5) is primarily based on three components:

  1. Time: How long does it take to perform the step?
  2. Tools required: Are the tools required for the step uncommon for an ordinary homeowner?
  3. Component visibility and technical knowledge: Does the step require mechanical knowledge or experience to be performed, and is the fastener visible or easily accessible?

Steps labeled with the highest difficulty rating (5) meet the entire aforementioned criterion at a high level; steps receiving the highest difficulty rating exacted substantial effort and time from the disassembly technicians of the group. The scale is further analyzed later in this section.


Tools Required

Note: Asterisk (*) denotes the rarity of the tool such that it registers a high rating on the scale of difficulty for the typical homeowner.

  1. Torque wrench size T25 (use straight-shafted, screwdriver grip)*
  2. Socket size 3/8
  3. Socket size 5/8 (deep)
  4. Socket size 7/16
  5. Adjustable Channel locks
  6. Holding pin (Straight shafted torque wrench will suffice)
  7. A manual press machine*
  8. Needle-nosed pliers


Scale of Difficulty

The scale of difficulty follows the three main criteria mentioned above along with several other minor attributes. Throughout the illustrated chart of the dissection process each step is characterized by a rating and a brief rationale behind that rating. Ranging from the numbers 1 to 5, the scale is as follows:

  1. Disassembly warrants the use of a common household tool, or even no tool as it may not be necessary
    • Component is easily accessible and very visible; that is, no other components of the product's configuration obstruct access to the component in question
    • Step for disassembly requires less than a minute given the application of and access to proper tool

  2. Satisfies all aspects of a difficulty rating of "1", although the tool necessitated may not be too common or readily available to the typical homeowner
    • More than one tool is required for adequate disassembly

  3. Step for disassembly requires a certain amount of mechanical and/or technical knowledge (e.g., in the case of a spring-loaded part)
    • Investment of considerable amount of time, apart from that consumed by the prerequisite of grasping and determining the appropriate procedure for a given step for disassembly, may be required for the typical homeowner to disassemble the particular component of assembly successfully

  4. Meets the criteria noted for a difficulty rating of "3", but involves an issue with the component's visibility (e.g., technical knowledge requirement: a shaft may require alignment so that it can be removed, but this alignment is obscured by other components)

  5. Step for disassembly requires a spectrum of knowledge transcending that of the average homeowner
    • The proper tools necessitated by the disassembly are seldom part of the standard technical equipment of a typical household
    • Typical homeowner may damage the product by utilizing improper, or entirely inapplicable, equipment and technique to remove a particular component.
    • Technical skill is a prerequisite to perform disassembly, which may entail limited visibility of the component being removed and the internal structure thereof that may affect neighboring or interdependent components


Procedure for Disassembly

Note: On the images below, red circles enclosing numbers, which are arbitrary and thus bear no relevance to any particular step corresponding to the exploded views, denote the region of the product or component thereof referred to in its respective step of disassembly. Please disregard, in the interest of obviating confusion, other annotations on the images as they are impertinent to the corresponding step of disassembly.

Images are courtesy of the Homelite®-published "Parts List", accessed via the public domain. For references, please scroll to the bottom of this page. [1]


Table 2.1: Procedure for Disassembly
Step Number Procedure Tools Difficulty (1-5) Image
1 Remove (4) fasteners that connect the control handle to the front plastic covering assembly.

Detach line trimmer shaft from complete engine assembly.
Requires torque wrench (T25). 2: Tool somewhat rare.
Figure 2.1: Two Taptite fasteners (27) on opposing sides are highlighted. Click to view a higher resolution of the image.


Engine Disassembly

2 Remove (2) fasteners from rear plastic covering (exhaust housing) located at the rear of engine assembly

Remove the covering by pushing in the plastic clip on the bottom.
Requires torque wrench (T25). 2: Tool somewhat rare.
Figure 2.2: Two Plastite fasteners (21) on opposite sides of the Rear Housing (20) are highlighted. Click to view a higher resolution of the image.
3 Remove the clutch drum from front end of engine shaft via a fastener located down the hollow tube of the clutch.

Remove entire clutch assembly by unscrewing the clutch from the engine shaft.
Requires torque wrench (T25). 4: Fastener not visible.
Figure 2.3: Clutch and Drum Kit (8) are highlighted. Click to view a higher resolution of the image.
4 Unscrew the fasteners (4) from the front plastic covering, and remove covering. Requires torque wrench (T25). 2: Tool is somewhat rare.
Figure 2.4: The Starter Assembly. Click to view a higher resolution of the image.
5 Remove flywheel from engine shaft.

Parts may contain small tolerance and may require an arbitrary tool for leverage.
No tools required. 1:
(Note: Rating subject to a “2” if tool is required for leverage).
Figure 2.5: The Flywheel (6), or Rotor, is highlighted. Click to view a higher resolution of the image.
6 Remove fuel lines from carburetor with needle-nosed pliers.

Remove fuel tank from assembly by force.
Requires needle-nosed pliers. 2: Step requires some amount of force applied by the technician.
Figure 2.6: The Fuel Tank Assembly (F) and its component Fuel Lines (8 and 9) are highlighted. Click to view a higher resolution of the image.
7 Remove air filter cap by simply pressing the plastic tab.

Remove filter.
No tools required. 1: Only hands required for removal of component.
Figure 2.7: The tab of the removable cap of the air filter is highlighted. Click to view a higher resolution of the image.
8 Unfasten Hex nuts inside of the air filter case.

Remove filter case as well as carburetor and its gasket (caution: gasket may tear).
Requires socket size 3/8. 1: Tool is very common and parts are easily accessible .
Figure 2.8: The Gasket (5) to the Carburetor and Hex nuts (10) securing the air filter kit to the carburetor are highlighted. Click to view a higher resolution of the image.
9 Unfasten (2) screws connecting heat dam to engine head, located directly behind carburetor.

Remove heat dam and gasket, as well as long screws that will be within heat dam.
Requires torque wrench (T25). 2: Tool somewhat rare.
Figure 2.9: The Gasket (1) and Screws (Sems) (4) of the Heat Dam are highlighted. Click to view a higher resolution of the image.
10 Remove muffler assembly, and gasket, via the (2) fasteners, which go through the muffler, and are located to the right when looking at the face of the muffler. Requires torque wrench (T25). 2: Tool is somewhat rare.
Figure 2.10: The Gasket (3) and Screws (Truss hd.) (4) of the Muffler Assembly are highlighted. Click to view a higher resolution of the image.
11 Remove ignition kit (magneto) from front of engine assembly by unfastening the 2 screws and disconnecting the terminal from the top of spark plug. Requires torque wrench (T25). 2: Tool required is somewhat rare.
Figure 2.11: The Screws (Taptite) and the Terminal (1) and Cover (2) of the Ignition Kit are highlighted. Click to view a higher resolution of the image.
12 Back out spark plug from atop the engine head. Requires deep socket size 5/8. 1: Part accessible; step requires less than 60 seconds to be performed.
Figure 2.12: The Spark Plug (3) raised above the ribbed piston encasing is highlighted. Click to view a higher resolution of the image.
13 Detach crankcase cover assembly from crankcase located at the rear of the engine assembly.

Unfasten the 4 screws and remove the component and its gasket.
Requires torque wrench (T25). 2: Tool is somewhat rare.
Figure 2.13: A Screw (Sems) (12) for the Crankcase Cover Assembly is highlighted. Click to view a higher resolution of the image.
14 Unfasten (3) fasteners which adjoin the engine head to the short block.

Fasteners are located underneath the head; screw in “upside down.”

Remove engine head and gasket allowing piston to slide out.
Requires torque wrench (T25). 2: Tool required is somewhat rare.
Figure 2.14: A Screw (Sems) (9) and the encasing, or engine head (4), for the Cylinder Assembly are highlighted. Click to view a higher resolution of the image.
15 Remove Piston & Rod Assembly from the crankcase by pulling bottom end of Rod off the shaft peg.

Remove Piston, Piston ring, and Piston Rod.
No tools required. 1: Components removed manually.
Figure 2.15: The Piston Ring (3), as well as the Piston & Rod Assembly (2), are highlighted. Click to view a higher resolution of the image.
16 Remove engine shaft from short block by machine pressing.

Part contains tolerance of about .001 of an inch.
Requires a manual press machine, or some other machinery of similar complexity and function. 5: Tool required is exceedingly rare for a common household; this step should be performed by someone with proper equipment and technical qualification (i.e., machine shop personnel).
Figure 2.16: The Engine Shaft connected to the Short Block is highlighted. Click to view a higher resolution of the image.
17 Remove (2) bearings and rubber seal from where shaft entered the short block.

Part contains tolerance of about .001 of an inch.
Requires a manual press machine, or some other machinery of similar complexity and function. 5: Tool required is exceedingly rare for a common household; this step should be performed by someone with proper equipment and technical qualification (i.e., machine shop personnel).
Figure 2.17: The image refers to the same as in the one above.


Line Spool/Guard Disassembly

18 Between the grass deflector shield and the string head, there is a thick washer.


If one rotates this washer, a cut-out square groove can be seen.

The bottom part of the Gear Head assembly also has a similar cut-out hole. Align these two holes and insert a holding pin (something thin enough to fit, but strong enough to withstand force. Torque wrench T25 should suffice.)


While keeping the holding pin in, use a pair of channel locks to grab the Stringhead and turn it counter-clockwise from a bottom point of view.

Remove Stringhead and washer.
Requires channel locks and a holding pin. 4: Step requires some technical knowledge in order to determine how to perform it; also, step may take a few minutes to perform, and the holes are not readily apparent.
Figure 2.18: The Gear Head (11), Grass Deflector (14), and Flanged Washer (18) are all highlighted. Additionally, the direction in which the Holding Pin is applied and in which the Stringhead rotates are also indicated by red arrows. Click to view a higher resolution of the image.
19 Unfasten (5) screws that hold the grass deflector to the Gear Head assembly, located underneath the grass deflector.

Remove grass deflector.
Requires socket size 7/16. 3: Step may require several minutes to be performed owing to the presence of a number of fasteners.
Figure 2.19: The Gear Head (11), Grass Deflector (14), and Taptite Hex Hd. Screw (12) are highlighted. Click to view a higher resolution of the image.
20 Unscrew (4) fasteners from the side of the Gear Head assembly.

Open Gear Head assembly and remove flexible drive shaft (some prying may be needed to open the gear assembly)

Gears may be removed.
Requires socket size 7/16, and torque wrench (T25). 3: Tool somewhat rare; two tools required; time-consuming process owing to the amount of fasteners present and possible prying.
Figure 2.20: The Taptite Hex Hd. Screw (12) and the Hex Hd. Screw (13) of the Gear Head assembly are highlighted. Click to view a higher resolution of the image.


Concluding Remarks

The complete dissection of the Homelite® Versatool™ line trimmer can be performed in approximately 4 hours, given all proper tooling and a non-corroded product. On the issue of disassembly, the product requires a relatively marginal time frame; however this does not mean that it was meant to be easily taken apart, much less to be fully disassembled.


Certain steps require tools that, conventionally, are not found in the possession of the ordinary homeowner. Steps 16 and 17, for instance, fall into this category, and are not meant to be taken apart. By rational and analytically guided estimate, the shaft and bearings are assumed not to manifest evidence of fatigue and possible failure for approximately a decade or more. The life of a line trimmer, to the contrary, is usually less than this. Therefore, there exists no reason to amend the removal of these components so as to reduce effort, whether technical or otherwise, on the part of the typical homeowner.


Components are so designed as to be easily accessible, thus allowing for comparatively hassle-free routine maintenance, and received a difficulty rating no higher than a “2”. These components consist of the air filter, the carburetor, and the spark plug. These components should be serviced seasonally; hence the product’s design oriented toward enabling disassembly that limits the breadth of technical knowledge needed during such a process.


The fasteners used for most of the product are torque screws, as they are easy to remove and apply enough compression to resist vibration. In some cases, as in the connection of the engine head to the short block, lock washers are used in addition to the torque screws. This connection undergoes extreme vibration during the product’s operation; lock washers provide a more secure connection to mitigate the probability of mechanical mishaps in that region of the product. The Homelite®, UT 15151 Versatool™, line trimmer dissection is rated as “simple” for regularly serviced components and as “difficult” for the other components.


To access further information relevant to Homelite® products and the Homelite® brand in general, please direct your browser to the link noted in the "References to Supplementary Material" below. [2]


References to Supplementary Material

[1] Web link to "Parts List" released to the public domain under the auspices of Homelite®. <http://dl.owneriq.net/c/cbf6c17d-6a3d-4204-b67d-144253fdccd7.pdf.>

[2] Online Home Page of Homelite®. <http://www.homelite.com/>


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Reverse Engineering Team Project: Homelite® VersaTool™ Line Trimmer (Group 29)