Final Design Project:Pressure Washer

EML2023 Computer Aided-Design

Steven Rosenberg4-15-2010

Page | 1

Table of Contents

Introduction 4

Design Specifications 4

Background Information 4-5

Design Concepts 5-7

Design Selection 7-8

Design Description 9-12

Cost Analysis 13-14

Appendix 15-24

Page | 2

Table of Figures

Figure 1: Lawnmower Design 5

Figure 2: Typewriter Design 6

Figure 3: Robot Car Design 7

Figure 4: Decision Matrix 8

Figure 5: Robot Car Assembly 9

Figure 6: Steering Assembly 9

Figure 7: Computer Housing 10

Figure 8: Nozzle Base/Pipe 11

Figure 9: Rear Wheel 12

Figure 10: Back View 12

Page | 3

Introduction

Pressure Washing, is the act of washing away dirt, grim, stains, or other unsightly blemishes through the use of a high pressure stream of water. Pressure washing is most commonly used as a way to clean driveways. According to http://www.drivewaytips.com/ the average American driveway is 10-12 feet wide, and 18-20 feet long. Such large areas make cleaning very long and tedious. This is especially true considering the water stream of a pressure washer can only clean about 1 inch at a time. With those statistics, a person needs to move the washer back and forth 10-12 feet about 230 times.

Aside from taking multiple hours of one’s time, pressure washing for such long hours can cause physical pain. Some of the most common affects from pressure washing is back pain, tennis elbow, arthritis in the hands, and knee issues. Cleaning a driveway should not cause pain nor does it need to. There are innumerous possibilities of how to make this daunting task easier and painless. In the following report I will present some of my personal ideas, as well as expanded upon what I believe is the best solution to the problem.

Design Specification

In order for the design to be considered successful, it should be able to meet or exceed the following parameters.

1. The mechanism should not weigh more than 50 pounds.2. The design should be able to clean at least as fast as a human (about 240

square inches per minute).3. It should take no more than five to ten minutes to setup.4. The design should be reliable and withstand at least 500 cleanings.5. The design should allow for interchangeable washer tips.6. The mechanism should be made of a material that will not rust if it gets wet.7. Last but not least, it should make cleaning easier on the person that purchases it.

Background Information

A pressure washer works in a very simple yet effective fashion. A low pressure garden hose bring water from the source to the pressure washer motor. The motor then pumps the water through a high pressure hose and down to the wand. In the wand the water is forces into a small area causing the velocity and pressure to dramatically increase until the water is forced out of the nozzle at up to 5,000 pounds per square inch of pressure. Such a tremendous force enables the pressure washer to remove virtually anything from any surface. Some pressure washers are capable of putting out so much pressure that the can cut through stone.

Page | 4

Setup for a pressure washer is a relatively simple process. A normal hose connects to a port in the washers motor. Then a specially selected nozzle, normally with a ¼ inch male quick release, is installed into a female quick release that is connected the end of the wand. The entire process takes just a few minutes, and the devise is ready for action.

According to http://www.the-power-washer-advisor.com/pressure_washer_nozzles.html, different pressure washer nozzles are used to clean different surfaces. The 15°nozzle is used to remove tough stains from hard surfaces like concrete. The larger 45°nozzle is commonly used to remove weaker dirt and stains from softer surfaces such as certain woods or soft stone. Because different surface require different nozzles, it would be wise to make a design in which the tips can easily be swapped in and out. The website goes on to say that for the most effective cleaning, the nozzle should be held approximately four inches about the surface.

Design Concepts

Design 1: Mower Style

The first design allows the user to operate the pressure washer like they would a lawnmower. A solid bar at the base of the mechanism will need to be specially manufactured so that when a hose is connected to the top of the bar, it travels to four separate nozzles so the cleaning area is four times greater the with the normal washer. The bar will be connected to a wheel on either side, and do long parallel bars extending upwards. The bars will then be connected by some sort of grip. To use the device, the person will simply need to plug their high pressure hose into the top of the block and then roll the unit around like the original lawnmowers.

Page | 5

Figure 1: Lawnmower design

Design 2: The Typewriter

This design consists of a basic frame sitting on two wheels that extends along an entire driveway. On each side of the frame will be a pulley bound to one another by a large belt. One pulley with be attached directly to the shaft of a reversible motor. A block with and hose connection on one side and a nozzle on the other will be fixed to the front of the belt. The motor will drive the block to the other end of the mechanism where it will hit a switch the reverses the motor. At the same time the motor is reversed, a stepper motor attached the wheels on the frame will be set a number of pulses in order to make the device move down the driveway. Just like a typewriter, the block with move back and forth while scrolling down until the entire area is completed.

Page | 6

Figure 2: Typewriter design

Design 3: Robot Car

This design will utilizes the technology of computer chips to drive a robotic car around a drive way. The user will be able to enter in the dimensions of their driveway into the computer which will then proceed to control a pair of motors in order to sweep over the entire area. The robots forward motion is driven by two back wheels attached to an axle which is driven by a motor. The steering will be controlled by a stepper motor on a gear rack. When the stepper is turned, the rack moves sideways which turns the front wheels. The water will be split into five separate streams so more area will be cleaned at one time.

Design Selection

After much deliberation I decided that design number 3, although very complex, would be the best solution to the problem. Number 3, the robotic car, will require almost no setup from the user and seems to be the most flexible of the designs. Design

Page | 7

Figure 3: Robot Car design

number 1, although very cheap to produce and easy to use, it would still require a lot of manual labor. Instead of taking four hours to wash the driveway is might take one, however, that is still an hour that one could spend doing something more enjoyable.

Design number 2 would be a totally automatic system but it too has some fatal flaws. For one, the device would be extremely difficult to store. A ten to twelve foot piece of metal with motors and wheels attached to it would not be easy to find a resting place for. This design is also not very dynamic. Say for example you had a driveway longer then the device. If that was the case then the entire mechanism would need to be redesigned, or after going down the driveway once it would have to be reset a few feet over in order to clean the rest. This design would also take a very long time to finish the job.

Design number 3, the robotic car, has none of the weaknesses of the others yet all of their strengths. It would be able to clean the driveway no matter what size, and do more the one inch at a time as in design number one, yet it would be fully automatic as in design 2. Unlike the design 2, a small robotic car would be extremely easy to store. Though it may cost a little more than the other designs, but the fact that is will clean faster, setup easier, and be far more versatile, makes the difference in price well with it.

The decision matrix below demonstrates how the different design compare to one another based on cost, setup, speed, versatility, and ease of operation.

Criteria Weight Factor Design 1 Design 2 Design 3Score Score Score

Cost .2 10 7 5Setup .2 8 6 10Speed .2 5 4 10

Versatility .2 7 5 10Ease of Op .2 4 9 10

Total Score: 6.8 6.2 9

Page | 8

Figure 4: Decision Matrix

Design Description

As seen in figure 4, the final design is a robotic car in which all parts are joined together by a large 1 foot by 2 feet aluminum frame. The back wheels are the driving force of the car, while the front wheels control all steering. The steering mechanism is powered by the stepper motor mounted to the front of the frame. Figure 6 illustrates how the rest of the steering mechanism is put together.

Page | 9

Figure 5: Final robotic car assembly (isometric view).

Figure 6: Steering assembly(exploded view).

A ¾” diameter shaft goes through the front holes of the frame then through each of the steering collars. The shaft is then welded to the frame so it does not turn, but the collar is free to rotate around it. Wheels are mounted to axle part of each collar. A ½”x2” bolt then loosely connects the gear rack to each of the collars and mated to the gear of the stepper and secured by a nut on the other side. When the stepper motor turns, the rack moves right or left, pushing one collar while pulling the other causing the wheels to angle thus making the car turn.

Behind the steering mechanism will be the computer chip housing. The housing is put together and mounted to the frame as shown in figure 7 below.

The main housing will be constructed out and ¼” thick aluminum sheet metal. It will be shaped like a box with and open top and two flaps on the sides. As shown in figure 7, bolt will mount the box to the front of the frame through holes in the flaps and the frame. Inside of the box will then go the computer chip as shown in green above. Finally a piece of cut class ¼” thick will be able to slide into place on top of the box to protect the chip from any water. The user will need to open the housing in order to enter their driveway dimensions into the computer. The chip will be programmed to then send the back motor power for the amount of time to reach the other side of the driveway. At that time the computer will send pulses to the stepper motor that will turn the car and send it back the other way.

Page | 10

Figure 7: Computer chip housing assembly (exploded view).

The next part of the assembly is the nozzle base and special one to five high pressured pipe. Figure 8 shows how the section is put together.

The nozzle base is made out of a 1”x1”x2” aluminum bar. There are a series of five ¼” holes spaced 1.5 inches apart. At the bottom of each hole goes a ¼” female quick release connector. This way five nozzles are working at once and can easily be switched. In order to get water to each of the nozzles, a special brass pipe is mounted in the other side of the bar. The pipe is made out of ¼” tube and turns one jet of water straight from the washer’s hose into five streams of water. With five nozzles, the car will be able to clean about 5” at a time. This assembly is then placed to two small brackets on the frame, and then secured with four ½”x2” bolts with nuts on the other side.

The final part of the car is the driving force behind the whole thing. That driving force is two wheels that are rotated by a dc motor. Figure 9 shows how this section is assembled.

Page | 11

Figure 8: Nozzle base/pipe assembly (exploded view).

As seen in the figure above, a 20 rmp dc motor is mounted to the frame via two small screws. On the shaft of the motor sits a 3/8” to ½” bushing, and on top of that a 3” gear. The rear axle will be made in two halves and later welded together so that another 3” gear can first be placed on it and mated to the motor’s gear. When the motor rotates counterclockwise, it will cause the axle to rotate clockwise. A 5” diameter wheel will be fixed to each half of the axle using ½”x1.5” bolts with a nut on the other end of each. The wheels will turn with the axle making the car roll forward. At 20 rmp the car should be able to travel about 26 feet per minute. If it cleans 5” and a time that means it cleans about 3,120 square inches per minute. The car moves just a little faster than a human probably would but with the five nozzles, can clean around five times faster.

Page | 12

Figure 9: Half of the rear wheel assembly (exploded view).

Figure 10: Back view (fully assembled).

Cost Analysis

Part Supplier Part Number

Quantity Needed

Price Total Price

1”x1” Aluminum tube

McMaster 88875k32 74” $9.12/6’Or$2.37/1’

$11.49

1”x2”x Al bar McMaster 8975k411 10” $13.09/1’ $13.09¼”x2” Al sheet

McMaster 6023k281 1’ $16.69/1’ $16.69

¼”x10” Al sheet

McMaster 8975k115 14” $12.32/1’ $24.64

¼”x3” Al disk McMaster 9035k31 2 $9.28/ea. $18.56½” Al rod McMaster 6750k163 14” $13.25/1’ $26.50Motor McMaster 6142k55 1 $48.61/ea. $48.613” gear Small Parts GSS-1460-

012 $26.56/ea. $53.12

3/8” to 1/2” bushing

McMaster 1688k13 1 $0.87/ea. $0.87

5” rubber wheels

McMaster 2337t43 4 $3.59/ea. $14.36

¼” quick release

McMaster 6537k63 5 $5.61/ea. $28.05

4” Gear McMaster 6325k32 1 $51.87/ea. $51.87Stepper Motor

All Electronics

23km-k246-01v

1 $9.00/ea. $9.00

¼” Brass tube

McMaster 7782t111 20.5” $4.64/1’ $9.28

3/8”-16x1.5” McMaster 91746a452 2 $8.75/ea. $17.50Gear Rack QTC Gears Ksrh2-100r 9” $26.00/8’ $26.008-32x.5” screw

McMaster 91355a075 4 $6.61/25 $6.61

½”-20x2” bolt McMaster 91251a020 10 $10.85/10 $10.85½”-20x1.5” bolt

McMaster 91251a016 10 $9.28/10 $9.28

½”-20 nut McMaster 93827a249 18 $7.50/25 $7.50¼” glass sheet

McMaster 8481k71 10”x9.5” $31.13/10”x10” $31.13

¾” Al rod McMaster 9062k331 5” $9.53/1’ $9.53¾”x1.5” Al tube

McMaster 9056k291 5” $10.42/1’ $10.42

¼”x3/4” Al bar

McMaster 6023k141 6” $7.64/1’ $7.64

Total Price: 429.98

Page | 13

Note: The price shown does not account for manufacturing costs, cost of the computer chip, or programming. The price does however pay for more material then actually needed.

Page | 14

Appendix

Note: All dimensions are +-.01 inches unless otherwise specified.

Table of Contents

Rear axle half 16

Computer housing 17

Frame 18

Left steering collar 19

Right steering collar 20

Back wheel 21

Nozzle base 22

Steering rack 23

Steering shaft 24

Pipe 25

Page | 15

Page | 16

Axle half

Page | 17

Computer housing

Page | 18

frame

Page | 19

Left wheel collar

Page | 20

Right wheel collar (only the changes from the left collar are shown)

Page | 21

Back wheel (only what needs to be modified from purchased part is shown)

Page | 22

Nozzle Base

Page | 23

Steering Rack (only what needs to be modified from purchased product is shown

Page | 24

Steering shaft

Page | 25

Pipe (although hard to tell, the pipe is made from ¼” brass tube