Group 25 - Snow Blower (Gasoline Powered)/Gate2

From GICLWiki

Purpose

For gate2, we will begin dissecting our snow blower. We will be documenting the steps taken in the removal and dissection of each component as well as the screw and bolt sizes. We will also be taking pictures of each component as we remove it. When listing the steps of dissection we will provide a reference for the difficulty level.

Cause for Corrective Action

As described in Gate 1, the original plan of disassembly for the Craftsmen Eager-1 snow blower involved our group partitioning the whole system into 4 different subsystems (Engine, Drivetrain, Auger/Chute and Handles/Controls). We were to start by removing the Handles/Controls subsystem by disconnecting all the associated cables and levers (throttle, chute controls, gear shift) and then unbolting the handlebars from the drivetrain housing. This process was very simple and as such went smoothly just as we planned.

The next step in our plan required us to remove the auger from the auger housing and then separate the auger housing from the drivetrain housing. We proceeded with this plan by removing 6 bolts securing the auger blade axle to the right and left sides of the auger housing. The next step required us to remove 4 bolts that we believed were securing the long auger axle and the impeller base to the rear of the auger housing. We encountered our first problem in the fact that we could not reach those 4 bolts with the tools available. Unable to remove the auger from the auger housing, we attempted to remove the auger housing from the drivetrain housing by unbolting it. However, we only succeeded in unbolting the front of the auger housing from its rear component. This step accomplished little because the auger blades could not yet be removed and were an obstruction to the removal of the front portion of the auger housing.

Unable to remove the auger from the auger housing or the auger housing from the drivetrain housing, we quickly decided to change direction and approach the dissection from the other side of the snow blower. From here on out our plan became flipped upside down. Rather than remove the auger and auger housing from the drivetrain before the engine, we decided to focus on removing the engine from the drivetrain housing and then separating the drivetrain housing from the auger housing. This plan appealed to us because it allowed us to make up lost time by having two people work on dissecting the engine separately while the other three worked on finishing the auger housing/drivetrain housing dissection. The new plan required us to remove the top and rear plates comprising the drivetrain housing. Once they were removed, not only was the entire drivetrain system clearly visible, but it became possible to access and remove four previously unseen bolts securing the drivetrain housing to the auger housing. Once we had succeeded in separating the drivetrain and auger housings, we began working on removing the auger from the auger housing with the intention of opening up the auger gearbox. The three working on the auger housing/drivetrain dissection were unable to remove the auger from the auger housing due to the difficult positioning of two square bolts securing the auger axle to the auger flywheel and the lack of adequate tools. Consequentially, we settled with cracking open the auger gearbox while it was still in the auger housing.

The Engine dissection team ran into it’s own difficulties. They had planned on removing the pulley on the crankshaft in order to remove the engine housing cover. However, the pulley (which obstructed the removal of all other major components) was secured by rusting set screws which were stripped when we attempted to remove them. The group discussed cutting the axle and cutting the engine body cover in order to see inside. However, these solutions would cause difficulties when it came time for reassembly so we decided to meet in the machine shop in Jarvis Hall so that we could use more advanced tools to remove the crankshaft.

While proceeding through this gate we did not encounter any management challenges. Everyone in the group is consistently showing up to meetings when they are available and everyone is doing the work assigned to them.

Product Archaeology: Product Dissection

GSEE Factors For Connection Implementation
Global

The snow blower uses metric units in the bolts and nuts that connect each subsystem together. The SI measurement system is internationally recognized. This simplifies maintenance because the consumer can easily find the correct size of tool to use.

Societal

There is an electric start button on the top of the snow blower which will allow the elderly or those that aren’t strong enough to use the pull start to start the snow blower.
The controls are placed near the handles with arrows showing the direction in which each lever moves and explaining what each lever does.

Economic

The connections in the snow blower are connected by inexpensive bolts and nuts.
The bolts and nuts are mostly the same type and size ranging from 8mm-13mm. This makes it simpler and less expensive to mass produce since there isn’t a large variety of materials used.
The user controls are connected by inexpensive cables and pulleys that can perform efficiently while keeping the price low.

Environmental

The snow blower’s different components and subsystems are connected by metal bolts which will allow it to sustain harsh beatings from the weather.
The hard sheet metal used for the housing of the snow blowers allows it to take harsh beatings from the weather and other variables in the environment.
The paint covering the body panels is not only for esthetics but also protects the body panels from oxidation.
The snow blower uses a four stroke engine which in general has cleaner emissions then its two stroke counterpart.

Sub-System Connections

Scale of Difficulty	Description
1	Very easy part is intended to be removed(i.e has visible fasteners that are not corroded and are easily accessible) can be removed with little to no tools(very intuitive) no experience neccesary
2	Easy Part is intended to be removed(i.e has visible fasteners that are not corroded and are easily accessible) Can be removed with one or two basic tools Small amount of experience with tools needed
3	Moderate part is intended to be removed for maintenance purposes(i.e has visible fasteners) and/or part is corroded Can be removed with one or two basic tools Moderate experience with tools needed
4	Difficult Part is not intended to be removed unless repairs are needed(i.e has visible fasteners) Can be removed with multiple tools/techniques required Experience with multiple tools/techniques required
5	Very Difficult Part is not intended to be removed(i.e no visible fasteners) Advanced tools/techniques needed Experience with advanced tools/techniques required

Step Number	Description	Image	Approximate Time	Tool Used	Difficulty
1	Disconnect throttle, chute adjust, auger engagement, pulley engagement cables	NO IMAGE	10 minutes	Needle Nose Pliers	3
2	Remove 4 bolts fastening controls to drivetrain housing		5 minutes	13mm socket wrench	2
3	Remove one bolt holding together U-joint on the linkage for the chute twister		2 minutes	10mm socket wrench	1
4	Remove 4 bolts from the two plates holding the chute on and removed chute		5 minutes	10mm crescent wrench	2
5	Remove bolts from the drive train housing and remove the housing		5 minutes	11mm socket wrench	1
6	After slipping the belts off the pulley connected to the engine, remove 4 bolts from the drive train housing		10 minutes	13mm socket wrench and crescent wrench	2

Engine

#	Component/subsystem	Description	Material	Component connected-How they are connected
1	Gas Tank	The gas tank stores the gasoline that powers the engine of the snow blower. The fuel line is connected to the bottom of the tank and leads to the carburetor.	Plastic	Carburetor-Mass
2	Carburetor	The carburetor is bolted onto the intake manifold of the engine body and it imports fuel through the fuel lines from the gas tank and mixes it with air it imports from the atmosphere. Once the intake valve is actuated by the cam shaft, the fuel mixture gets sucked into the cylinder.	Various metals Rubber Plastic	Gas tank-Mass Governor-Signal Engine body-Physical Piston-Mass
3	Valves	Exhaust valve- opens to remove exhaust gas from the cylinder Intake valve- opens to let fuel/air mixture into cylinder Both valves consist of a valve stem, spring, lifter, valve seat and two spring retainers. The valve stem sits in the engine body vertically and is held shut against the valve seat by the spring and retainers. Below the valve stem, the bottom of the lifter sits on the camshaft.	Steel	Camshaft-Physical Engine body-Physical Piston-Mass Cylinder head-Mass
4	Camshaft	Rotated by the crankshaft to actuate the intake and exhaust valves using two cams that are set on the shaft. The camshaft rotates and periodically opens the intake and exhaust valves in extremely synchronous timing with the crankshaft.	Forged steel	Valve lifter-Physical Crankshaft-Physical Engine body-Physical
5	Piston	The piston subsystem consists of the piston head, connecting rod and piston rings. The piston head has three grooves in it where the piston rings sit. These rings seal off the bottom of the piston from the top. The piston head and rings are situated inside of the cylinder of the engine body. The connecting rod is attached to a pin on the bottom of the piston head so that it is free to rotate on one axis. Below the cylinder, the other end of the connecting rod is bolted to the crankshaft. When the piston moves vertically in the cylinder this linear motion is converted to rotational motion through the connecting rod due to the eccentricity of the the portion of the crankshaft that attaches to the connecting rod.	Aluminum-Piston head, Connecting rod Steel-Piston rings	Engine body-Physical Cylinder head-Energy Camshaft-Physical Spark plug-Energy Intake and Exhaust valves-Mass
6	Crankshaft	The crankshaft sits horizontally in the engine body. The eccentric vertical force from the connecting rod creates a moment which rotates the shaft. The teeth of the gear on the crankshaft mesh with the gear in the camshaft. The gear on the governor is also meshed with the gear on the crankshaft.	Forged steel	Camshaft-Physical Connecting rod-Physical Engine body-Physical Governor-Physical Flywheel-Physical Pulley-Physical
7	Governor	The governor provides a negative feedback system between the crankshaft and the carburetor. It sits on the engine body cover and when in place, the gear on the governor meshes with the gear on the crankshaft. When the crankshaft rotates too quickly, two small spring loaded weights on the governor move outward due to centrifugal force. This causes the governor to move a pin on the outside of the engine body cover which is connected to the carburetor. Once the pin moves, the carburetor reduces the amount of fuel it is dispensing into the cylinder until the crankshaft slows down enough for the spring loaded weights to move back into place. This process is constantly happening in the motor to regulate the flow of fuel into the cylinder.	Steel-Weights and Spring Plastic-Gear	Carburetor-Signal Crankshaft-Physical Engine body cover-Physical
8	Flywheel	The purpose of the flywheel is to store the rotational energy coming from the crankshaft. It is mounted to one end of the crankshaft that is tapered using a keyway. The flywheel also houses two magnets that pass very close to the spark distributor when the crankshaft rotates.	Cast iron	Crankshaft-Physical Distributor-Energy Electric starter-Physical Pull start-Physical
9	Spark Distributor	The spark distributor slides onto the crankshaft (underneath the flywheel) and is bolted to the engine body. When the flywheel rotates, two magnets pass very close to a portion of the distributor and cause an electric current to flow. The electric current runs out of the distributor though a wire to the spark plug.	Various metals Plastic Rubber	Flywheel-Energy Engine body-Physical Spark plug-Energy
10	Spark Plug	The spark plug is what creates the spark in the combustion chamber to ignite the fuel. The top of the spark plug is connected to the wire running from the spark distributor. The wire feeds electric current into the spark plug which creates a spark at the bottom of the plug. The spark plug is bolted into the cylinder head and the sparking section if it sits right above the piston.	Various metals Plastic	Cylinder head-Energy Spark distributor-Energy Piston-Energy
11	Cylinder Head	The cylinder head is bolted to the top of the cylinder portion of the engine body. The cylinder head houses the spark plug and the underside of the head is where the combustion of fuel takes place.	Cast aluminum	Spark plug-Physical Engine body-Physical Intake and exhaust valves-Mass Piston-Mass
12	Muffler	The muffler is attached to the exhaust port on the engine body. It directs the exhaust out and away from the engine as well as muffling some of the noise coming from the engine.	Iron	Exhaust valve-Mass Engine body-Physical
13	Engine Body(crankshaft and connecting rod visible in picture)	The engine body provides a base for all of the engine subsystems and components to be supported and fastened to. The top portion of the engine body is the cylinder while the bottom of the engine body is the crank-case.	Cast iron	All components/subsystem
14	Pull start	The pull start is bolted onto one of the body panels. When someone pulls the cord on the pull start, a tooth on the pull start grabs onto a receiving cup that is bolted directly to the flywheel and spins the flywheel. This is one way to start the engine if electricity is unavailable.	Nylon Steel Plastic	Flywheel-Physical Body panel-Physical
15	Electric Starter	The motor of electric start is screwed onto the engine body while the plug receiving end is screwed to the cylinder head. When plugged into an electrical source the electric starter can be activated using a button on the plug receiving end. When the button is pushed, the electrical motor spins causing the gear on the tip of it to engage with the teeth on the flywheel. Once you stop pressing the button the electric motor stops spinning and the tip of it retracts to its original position.	Various metals Plastic Rubber	Flywheel-Physical Engine body-Physical Cylinder head-Physical
16	Pulley	The pulley is what transfers the power from the engine to the belts that drive the auger and drivetrain. It is fastened onto the crankshaft using a keyway and two set screws.	Iron	Crankshaft-Physical Auger and drive train belts-Physical

Component Interactions: Engine Timing

In order for the engine to operate correctly there is very crucial timing that must be satisfied between the crankshaft, camshaft, valves, and spark distributor. In a single cycle of the the four stroke combustion cycle, the piston moves from its highest position to its lowest position(known as the stroke) two complete times. This means in one cycle, the crankshaft makes two complete revolutions. Because each valve only opens once for every cycle, the camshaft only needs to make one complete revolution per cycle. To resolve this, there is a two to one ratio between the meshing gears of the crankshaft and camshaft. If these two gears are meshed correctly, in each four stoke engine cycle, each valve will open once at the exact time it is necessary. Now the timing of the spark distributor is similar to the camshaft timing in that for every four stroke cycle, the spark plug only fires once when the piston is at its highest position(known as top dead center). In order for this to happen, the magnets on the flywheel must be in a very specific location in relation to the crankshaft that the flywheel is mounted on so that when the crankshaft rotates to move the piston to top dead center, the magnets pass the distributor, a current is generated and the spark plug fires!

Note: This image is an Overhead Cam configuration where the camshaft(s)and valves are located above the cylinder in the cylinder head, where as our own configuration places the camshaft inside the crankcase adjacent to the crankshaft.

Step number	Description	Image	Approximate time	Tool used	Difficulty
1	Remove hex bolts holding on some body panel as well as engine head and remove it with the gasket	,	10 minutes	13mm socket wrench	3
2	Remove the spark plug from the head		1 minute	21mm socket wrench	2
3	Unscrewed oil filler spout		1 minute	none	1
4	Remove 4 phillips screws holding on electric start		2 minutes	Medium phillips head screwdriver	2
5	Remove 2 hex bolts holding on pulley guide		2 minutes	13mm socket wrench	3
6	Remove hex nut and washer holding on pull start receiver		1 minute	19mm deep well socket wrench	3
7	Remove 3 phillips screws holding on exhaust, exhaust mount, and gasket		5 minutes	Medium phillips head screw driver	4-screws rusted in place
8	Remove 2 hex nuts and 2 phillips screws holding on carburetor		5 minutes	11mm crescent wrench, phillips head screwdriver	4-difficult to access
9	Remove phillips screw fastening governor linkage		2 minutes	small phillips head screw driver	2
10	Drill out, stripped 4mm allen set screws on motor pulley		5 minutes	power drill, 1/4in metal drill bit	4
11	Remove pulley from crank shaft		10 minutes	gear puller, medium adjustable wrench	4
12	Remove flywheel from crank shaft		5 minutes	gear puller, medium adjustable wrench	4
13	Remove 2 hex bolts holding on distributor		1 minute	11mm socket wrench	2
14	Remove 8 hex bolts from engine housing cover and took off engine housing and gasket		5 minutes	10mm socket wrench	3
15	Remove 2 philips screws holding on the cover to access the valve spring		2 minutes	small phillips head screwdriver	2
16	Remove valve spring		20 minutes	spring compressor, needle nose pliers	4-removal of spring retainers proved very difficult
17	Remove intake and exhaust valves.		1 minute	none	1
18	Turn the motor upside down to remove the cam shaft		1 minute	none	1
19	Remove lifter from engine housing		1 minute	none	1
20	Remove Remove two bolts and oil splasher from bracket fastening connecting rod to crankshaft(10mm)		2 minutes	10mm socket wrench	3
21	Pull crank shaft through engine housing		1 minute	none	1
22	drop piston through engine housing		1 minute	none	1

Auger & Drive Train

#	Component/subsystems	Description	Material	Component connected
1	Wheels and Axle	Two 10 inch wheel locked to a single axle within the Drive Train section	Rubber and Steel	Axle runs through final drive gear member in drive gear subsystem. Final stage in converting rotational energy from drive gears to linear motion along the ground.
2	Drive Pulley and Belt	Main wheel that receives power from the engine crank shaft and transfers it to the system that moves the snow blower	Steel and Rubber	Connected to the Crank Shaft by rubber belts and to the Drive Wheel by an axle.
3	Drive Wheel	Wheel that receives power from the fly wheel axle and can be moved side to side by the Transmission to adjust the speed	Steel with rubber circumference	Connected to the Drive Gear system by an axle
4	Driving Gear System	Two sets of axles with gears on either end to reduce RPM and increase torque	Steel	Two sets of chains converting power from the Driving Wheel to the Wheels
5	Housing Plates	Three steel shields that enclose the internals of the Drive Train. Provide structural integrity	Steel	Bolted to the Housing. The housing plate subsystem fulfills a function unrelated to energy transformation/translation.
6	Belt Engagements	Two pulleys that when force was applied by a cable from the controls, would tighten the belts and drive the desired units	Steel	Bolted to the Drive Housing, and received tension from the Controls, and helped transfer power from the engine to the Auger and Drive train
7	Auger Pulley and Belt	Receives power from the engine Crank Shaft and transfers it to the Auger Drive Shaft	Steel and Rubber	Connected to Enginge Crank Shaft and Auger Drive Shaft
8	Auger Drive Shaft	The main "axle" providing rotational energy to the impeller and the auger gearbox	Steel	Connected Auger Pulley, Impeller, Auger Geabox
9	Impeller	Receives energy from the Drive Shaft and uses it to throw snow out of the chute	Steel	Connected to Auger Drive Shaft
10	Auger Gearbox	Translates the rotational energy from the drive shaft 90 degrees to the auger itself by means of a worm gear setup inside	Steel and gear lubricant	Connects the Auger Drive shaft and the auger
11	The Auger	Receives rotational energy from the gearbox and uses it to intake snow with the auger blades and sends it to the Impeller	Steel	Connected to the Auger Housing and the Gearbox
12	Auger Housing	Encases the Auger Unit and holds the the Auger in place while snow is taken in	Steel	Connected to the auger and the Impeller Housing
13	Impeller Housing	Encases the impeller and holds the chute in place as well as the auger housing	Steel	Connected to the Auger Housing and the Drive Train Housing and Chute
14	Chute	Funnels snow thats being thrown by the Impeller and directs it in a desired diredction	Steel	Connected to the Impeller Housing and the Controls via a rod

Step number	Description	Approximate time	Tool used	Difficulty
1	Remove belt tensioner from right side of housing. 2 bolts (11mm)	2 minutes	Wrench(11mm)	3
2	Remove top drive train plate connected by 6 bolts (1/2 inch)	3 minutes	Wrench(1/2 inch)	2
3	Remove gear box from Drive Train Housing. 2 bolts (19mm)	2 minutes	Wrench(19mm)	2
4	Disconnect Drive Train Housing from Auger. 4 bolts (14mm)	6 minutes	Wrench(14mm)	3
5	Remove 8 bolts holding Auger Differential together. (1/2 inch)	20 minutes	Socket Wrench(1/2 inch)	3
6	Remove 2 bolts securing Auger Blades to Auger Axle. (13mm)	5 minutes	Wrench(13mm) and Hammer	4-bolts were rusted/pinched in place
7	Crack Auger Gearbox open with screw driver and hammer (Be ready for fluid drainage)	2 minutes	Screwdriver and hammer	3