dynamic mechanisms problems - t4 mechanisms name ... attached to the axle of the ch ... the original...

4
DYNAMIC MECHANISMS NAME: ______________________________ DATE: _____________ Learning Outcomes - Students should be able to: 1 A cycloid is the path traced out by a ________________ on the circumference of a circle as it rolls along a fixed ____________ ______________ without slipping. Figure 1 shows an image of a racing bicycle. The tyres are inflated through a valve located on the rim of the wheel. A circle and a line representing the wheel and the ground are displayed in Figure 2. Point ‘P’ represents the valve on the wheel. Plot the locus of point P as the circle rolls along the line for one com- plete revolution. The Roman architect Vitruvius developed machines for measuring distance, one such machine was an Odometer. The diameter of a chariot wheel was 4 feet. If a mark is placed on a wheel where it touches the ground, and the chariot then moves until the mark comes to the ground again, the chariot will have moved 12.6 feet. A device was attached to the axle of the chariot such that when a wheel made one revolution, a drum with 400 teeth on it moved round one notch. A complete rotation of the drum was equivalent to a motion of 400(12.6)= 5,040 feet by the chariot. At this point the device dropped a stone into a bronze bowl, 5040 feet was one Roman mile. Figure 3 represents the wheel of a Roman chariot. The lines AB and BC represent the ground on which the chariot is travelling. Plot the locus of point P as the circle rolls along AB and BC, without slipping, until point P comes in contact with the line BC. Figure 3 Construct Standard Cycloids from given data Construct a tangent at a point on a cycloid. CYCLOIDS Figure 1 - Racing Bicycle Figure 2

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Page 1: Dynamic Mechanisms Problems - t4 MECHANISMS NAME ... attached to the axle of the ch ... The original Da Vinci sketch of the cam operated hammer

D

YN

AM

IC M

EC

HA

NIS

MS

NA

ME

: __

____

____

____

____

____

____

____

D

AT

E:

___

____

____

__

Lea

rnin

g O

utco

mes

- St

uden

ts sh

ould

be

able

to:

1

A c

yclo

id is

the

path

trac

ed o

ut b

y a

____

____

____

____

on

the

circ

umfe

renc

e of

a c

ircle

as i

t ro

lls a

long

a fi

xed

____

____

____

___

____

____

___

with

out s

lippi

ng.

Figu

re 1

sho

ws

an i

mag

e of

a r

acin

g bi

cycl

e. T

he t

yres

are

inf

late

d th

roug

h a

valv

e lo

cate

d on

the

rim

of

the

whe

el. A

circ

le a

nd a

lin

e re

pres

entin

g th

e w

heel

and

the

grou

nd a

re d

ispl

ayed

in F

igur

e 2.

Poi

nt

‘P’ r

epre

sent

s the

val

ve o

n th

e w

heel

. Pl

ot th

e lo

cus

of p

oint

P a

s th

e ci

rcle

rolls

alo

ng th

e lin

e fo

r one

com

-pl

ete

revo

lutio

n.

The

Rom

an a

rchi

tect

Vitr

uviu

s de

velo

ped

mac

hine

s fo

r m

easu

ring

dist

ance

, one

suc

h m

achi

ne w

as a

n O

dom

eter

. Th

e di

amet

er o

f a

char

iot w

heel

was

4 f

eet.

If a

m

ark

is

plac

ed o

n a

whe

el w

here

it

touc

hes

the

grou

nd,

and

the

char

iot

then

mov

es u

ntil

the

mar

k co

mes

to

the

grou

nd

agai

n, th

e ch

ario

t will

hav

e m

oved

12.

6 fe

et. A

dev

ice

was

at

tach

ed to

the

axle

of

the

char

iot s

uch

that

whe

n a

whe

el

mad

e on

e re

volu

tion,

a d

rum

with

400

tee

th o

n it

mov

ed

roun

d on

e no

tch.

A c

ompl

ete

rota

tion

of t

he d

rum

was

eq

uiva

lent

to

a m

otio

n of

400

(12.

6)=

5,04

0 fe

et b

y th

e ch

ario

t. A

t th

is p

oint

the

dev

ice

drop

ped

a st

one

into

a

bron

ze b

owl,

5040

feet

was

one

Rom

an m

ile.

Figu

re 3

repr

esen

ts th

e w

heel

of a

Rom

an c

hario

t. Th

e lin

es A

B a

nd B

C

repr

esen

t the

gro

und

on w

hich

the

char

iot i

s tra

velli

ng.

Plot

the

locu

s of p

oint

P a

s the

circ

le ro

lls a

long

AB

and

BC

, with

out

slip

ping

, unt

il po

int P

com

es in

con

tact

with

the

line

BC

.

Figu

re 3

C

onst

ruct

Sta

ndar

d C

yclo

ids f

rom

giv

en d

ata

C

onst

ruct

a ta

ngen

t at a

poi

nt o

n a

cycl

oid.

CY

CL

OID

S

Figu

re 1

- R

acin

g B

icyc

le

Figu

re 2

Page 2: Dynamic Mechanisms Problems - t4 MECHANISMS NAME ... attached to the axle of the ch ... The original Da Vinci sketch of the cam operated hammer

D

YN

AM

IC M

EC

HA

NIS

MS

NA

ME

: __

____

____

____

____

____

____

____

D

AT

E:

___

____

____

__

Lea

rnin

g O

utco

mes

- St

uden

ts sh

ould

be

able

to:

2

LO

CI 1

A la

dder

is sh

own

lean

ing

agai

nst a

bric

k w

all.

An

eyel

et fo

r atta

chin

g a

safe

ty ro

pe is

la

belle

d as

poi

nt P

on

the

ladd

er. I

f the

ladd

er w

ere

to sl

ide

dow

n th

e w

all a

nd c

ome

to a

rest

on

the

grou

nd a

s ind

icat

ed, p

lot t

he lo

cus o

f the

poi

nt P

for t

his m

ovem

ent.

P

A g

arde

ner w

ishe

s to

mar

k ou

t an

ellip

tical

sha

ped

flow

erbe

d si

mila

r to

the

one

in th

e ph

otog

raph

acr

oss.

The

gard

ener

will

use

a tr

amm

el

to m

ark

out t

he c

urve

. Th

e m

ajor

and

min

or a

xes

are

1.5m

and

1.2

m re

spec

tivel

y. T

o a

scal

e of

1:1

0 m

ark

out t

he e

llips

e us

ing

a tra

mm

el o

n th

e ce

ntre

lines

dra

wn

belo

w.

P

PA

45

PB

75

P 1A

1

P 1B

1

P 2A

2

P 2B

2

Show

n be

low

is a

n el

lipse

with

maj

or a

nd m

inor

axe

s of 1

50m

m a

nd 9

0mm

, res

pect

ivel

y. T

he li

ne

PB is

equ

al in

leng

th to

hal

f the

maj

or a

xis a

nd is

pos

ition

ed w

ith P

on

the

curv

e an

d B

on

the

m

inor

axi

s. A

is th

e po

int w

here

the

line

inte

rsec

ts th

e m

ajor

axi

s. Th

e m

easu

rem

ents

PA

and

PB

are

reco

rded

in th

e ta

ble

acro

ss. F

ill in

the

rem

aini

ng m

easu

rem

ents

in

the

tabl

e. D

o yo

u no

tice

any

patte

rn e

mer

ging

? W

hat c

an w

e co

nclu

de fr

om th

is in

form

atio

n?

C

onst

ruct

the

locu

s of a

poi

nt d

efin

ed b

y th

e m

ovem

ent o

f a li

ne re

lativ

e to

ano

ther

line

Con

stru

ct a

n el

lipse

usi

ng a

tram

mel

Page 3: Dynamic Mechanisms Problems - t4 MECHANISMS NAME ... attached to the axle of the ch ... The original Da Vinci sketch of the cam operated hammer

D

YN

AM

IC M

EC

HA

NIS

MS

NA

ME

: __

____

____

____

____

____

____

____

D

AT

E:

___

____

____

__

Lea

rnin

g O

utco

mes

- St

uden

ts sh

ould

be

able

to:

3

LO

CI 2

C

onst

ruct

the

locu

s of a

poi

nt in

a li

nk m

echa

nism

An

inte

ract

ive

toy

for

a ch

ild i

s pi

ctur

ed i

n Fi

gure

1. T

he t

oy i

ncor

pora

tes

a m

echa

nism

whi

ch c

ause

s th

e fr

ont

load

er t

o ra

ise

and

low

er w

hen

the

back

w

heel

s ro

tate

. Fig

ure

2 sh

ows

the

fron

t loa

der

in it

s lo

wes

t pos

ition

. The

line

di

agra

m fo

r the

mec

hani

sm is

show

n be

low

. (a

) D

raw

the

fron

t loa

der w

hen

it is

in a

fully

ext

ende

d po

sitio

n.

(b)

Dra

w th

e lo

cus o

f poi

nt P

for t

his m

ovem

ent

Figu

re 2

- Lo

ader

in lo

wes

t pos

ition

Figu

re 1

- In

tera

ctiv

e To

y

Figu

re 3

- El

liptic

al

Exer

cise

Mac

hine

Dai

ly e

xerc

ise

is a

n es

sent

ial c

ompo

nent

of

a he

alth

y lif

esty

le.

Figu

re 3

dis

play

s an

imag

e of

a s

ki e

xerc

ise

mac

hine

com

mon

ly

foun

d in

the

gym

. A li

ne d

iagr

am re

pres

entin

g th

e m

ovem

ent o

f th

e sk

i m

achi

ne i

s ca

ptur

ed i

n fig

ure

4. P

oint

P r

epre

sent

s th

e fr

ont o

f the

foot

pla

tform

and

is fi

xed

on B

C. P

oint

s A a

nd O

are

fix

ed, B

is a

pin

join

t and

C is

con

stra

ined

to tr

avel

abo

ut O

Pl

ot th

e lo

cus o

f poi

nt P

for t

he m

ovem

ent o

f the

mec

hani

sm.

Figu

re 4

Page 4: Dynamic Mechanisms Problems - t4 MECHANISMS NAME ... attached to the axle of the ch ... The original Da Vinci sketch of the cam operated hammer

D

YN

AM

IC M

EC

HA

NIS

MS

NA

ME

: __

____

____

____

____

____

____

____

D

AT

E:

___

____

____

__

Lea

rnin

g O

utco

mes

- St

uden

ts sh

ould

be

able

to:

4

CA

MS

2

Figu

re 1

, acr

oss,

show

s a

pinb

all

mac

hine

com

mon

ly fo

und

in a

mus

emen

t arc

ades

. A c

am a

nd

follo

wer

mec

hani

sm is

use

d to

rele

ase

the

ball

to th

e pl

ayer

. W

hen

a co

in is

inse

rted

a ca

m ro

tate

s an

ticlo

ckw

ise

and

the

follo

wer

mec

hani

sm ra

ises

the

ball

to th

e la

unch

pad

in fr

ont o

f the

plu

nger

. The

bal

l is

held

mom

enta

rily

for t

he p

lung

er to

mak

e co

ntac

t with

it; t

hen

the

mec

hani

sm d

rops

bac

k do

wn

to re

ceiv

e th

e ne

xt b

all.

(a)

Plot

the

disp

lace

men

t dia

gram

for

the

cam

giv

en th

at it

impa

rts th

e fo

llow

ing

mot

ion

on

the

follo

wer

;

0° to

180

° ris

e of

30m

m w

ith u

nifo

rm a

ccel

erat

ion

and

reta

rdat

ion

18

0° to

270

° dw

ell

27

0° to

360

° fal

l of 3

0mm

with

uni

form

vel

ocity

The

near

est a

ppro

ach

of th

e fo

llow

er to

the

cam

cen

tre is

18m

m.

(b)

Con

stru

ct th

e co

rres

pond

ing

cam

pro

file

to im

part

this

mot

ion

Show

n in

figu

re 2

is a

mod

el o

f a c

am o

pera

ted

sled

ge h

amm

er

base

d on

an

idea

by

Leon

ardo

Da

Vin

ci. T

he c

am, b

ased

on

an

Arc

him

edea

n sp

iral,

is d

esig

ned

to ra

ise

the

ham

mer

slow

ly a

nd

then

dro

p it

from

a h

eigh

t. C

onst

ruct

the

cam

pro

file

give

n a

min

imum

radi

us v

ecto

r of 1

2mm

an

d a

max

imum

radi

us v

ecto

r of 6

0mm

.

Figu

re 2

- C

am o

pera

ted

Sled

ge H

amm

er

The

orig

inal

Da

Vin

ci s

ketc

h of

the

cam

op

erat

ed h

amm

er. I

t is

belie

ved

that

he

deve

lope

d th

e id

ea

of

an

auto

mat

ic

ham

mer

to h

elp

blac

ksm

iths,

who

use

d re

peat

ed b

low

s of a

ham

mer

in th

e

proc

ess o

f for

ging

stee

l.

C

onst

ruct

cam

pro

files

and

dis

plac

emen

t dia

gram

s

Con

stru

ct ra

dial

pla

te c

ams o

f giv

en u

nifo

rm v

eloc

ity, s

impl

e ha

rmon

ic

m

otio

n, u

nifo

rm a

ccel

erat

ion

and

reta

rdat

ion

to in

-line

kni

fe e

dge

follo

wer

s.

Figu

re 1

- Pi

nbal

l Mac

hine