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SOME MATERIAL HANDLLNG PROBLEMS
N A LEATHER TANNERY.
WITH PRACTLCAL SOLUTIONS
THESIS FOR THE DEGREE 0? 1E.

W. P. Robinson
1930

 

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U. P; iobinson

_"‘——

C;

Rachag’cal Ergiucer

jHEStS

 

'(D

C.)
a - GENERAL STATUS OF TIE ITTDUSTIIY TO DIE CON SID JERE 3-
b - SPECIAL LABOR TIE QUIET EITTS 3
C - THE ECOITOIJIC SITUATIJI'T AS IT A377°TCTS BUILDINGS MID A:

EQUIPTESITT

01

d - ITECESSITY I‘OII II'PIIOVE D ELITE JL III-IITDL ITTC— MTIIODS

[5

e - CHOICE OF L’IUIPIIEITT TO BEST SUIT .L‘IIE CONDITIONS 0

J

CD

If - DE SCR IP‘] IOI-T OF IIOI‘TOI IAIL S VSTEIT [II‘TD II S APPLICATIOI‘T
g - DESCRIPTIOI‘T OI‘ SPECIEIJ E.O.T. CRIIITE AITD TRAYS IO
YS ELI ILITD ITS APPLICM ION

h - SOLUTION OF PEOEL'TETIS TIE” TJITII III ESE CIT OF CED-LITE 14:

oOo

- DESIGN DI? ..’IITCS -

 

SK 2-4-29A - Plan of Honorail System

SK 2-4-29B - Plan of fionorail System

SK l-lO-ZQB - Double Hook and Bail

S 6-8-29B - General Drawing of G-ton Crane

S 5-11-29A - Speed Iiedueer

SK 6-13-29A - General DraJing of 6— ton Transfer
SK 5-9-29A - Headbeam Hook :Eor Racks

SK 5-15-293 - Bearing

oOo

- PHOTOGRAPH -

 

Ph A - Crane and Transfer - Case 1.

4' g“ , 'l‘
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a - Ge.sa I F‘qm' 0? W16 I“DU T?Y TO BE CONSIDERED.

W18 for.rard march of the world makes inexorable
demands on our industrial life which more often than not
take the form of problems for the preper solution of which
engineering assistance in some form is necessary. A few
outstanding branches of our great industrial body set

this forward pace. Pe erha

"3
0’)

one is pushing forward some
new discovery or invention; another may be interested in
the intensive develOpnents in some such field as the
generation of power. In such cases an appeal is mad e to
the imagination and love of accomplishment of the modern
business man and it appears that all the incentives are

1 .

present for rapid develOpment. It is quite evident that
with some stepping out in front the others soon catch

he spirit, and the race is on. Soon we see the deiand
for greater an‘ still greater efficiency taking form in
one way or another; greater production is wanted, or
better material. We s;e a brand new industry arise over
night with material requirements t1at were not dreamed

of before; immediately certain suppliers of the required
materials beg in to perform the impossible and the demands
are met satisfactorily. Besides tl1i for rn of stiznulus to
our technical advance,a n1 of an equallv insistent nature
there is the ever present force of competition at work
Operating to make the progressnve manufacturer more pro-
gressive and to eliminate the too consar ative manufac-

rn‘

turer. inis is probably the nest gore wr llv fc t and most

  
  

.m 51.5.”: u.. ”Wan,‘ , qufllwq .. . I13...

'.I!. I

 
 

(D

(.4.

easily recognized cause of technical advance and the terms
in which it is expressed are familiar to all - how can the
cost of manufacturing be still further reduced? How can
the cost of power be reduced, etc.? Still another incen-
tive to the deveIOpment of new ideas, new methods, etc.,
is the possibility existing in so many industries of
suddenly having to change from an old ell- -known product
to another entirely new one. Witness the number of auto-
mobile manufacturers hat were originally carriage
builders. A1d so we see going on Mounl us coz1t inually

the building of new plant, installing of new nacainery,

(‘3‘
Ho

.4

the trying of new methods, and i s safe to say that
there is not a major industry unaffected. Let us now
recognize that the driving force behind all this indus-
trial life is the making of a satisfactory living or
profit.

Assume, however, that a major industry, such as will
be discussed in this paper, has found it dilfi cult, if not
impossible, to secure a satisfactory profit from opera-
tions. It is not the purpose of this paper to show why
there should be, or should not be such, but to merely
state that there were three in 192 - lea,her, sugar and
wool - in a total of .57 industries, and of these three
the leat21er induSLry has shown a defiCit consi isten tly for
several years. This is the industry that this paper is

concerned with and it is our purpose to show how this

condition may give rise to problens which can be solved

only by the application of exactly the same devoted and
concentrated engineering attention that is causing the
world to march at its present pace, — with, however, this

J.

difference:- that the cost of improvements must be the
absolute minimum, and those costs will be incurred only
when the results are certain beyond question to produce
lower process costs. Let it be stated here that the un-
favorable situation in which the tanning industry has
found itself for several years past is in no measure due
to lack of ability on the part of the tanners. On the
contrary quality has been improved and manufacturing
costs out without the encouragement of visible profits,
which is a condition requiring both ability and courage
of high order.

The condition u have to bear in mind than is that
there is a great basic industry like the sole leather
tanning business, with an intense desire to surmount the

economic handicaps that exist iaternally, and little

0 1-1

money Wlbfl which to do it.

b - SP 130111-, LABOR P17351712“)?IIITTS.

 

 

F’l"

ine tanning industry is an old one in many cases
having descended from generation to generation in the same
family, each generation having been born in and bred to

the business. A natural result has been self-reliance and

CT
}-—0
0)
O
53
d.
:1

great conserva‘ ‘0 part of executives who have been

entirely self-sufficient, and, urged by necessity have

deve lepe'd consile1aole strength in handling the heavy wet
Ihides, “filfl111n3r BS'ult that CLIrervy labor tflulWJVSP has
'7

been undesirable. Another eonse suenee nas been that labor-

saving machiner7 or metaods were sound to receive more

than ore inar7 attention. The tanning process is continuous
and considerable ingenuit7 must be exercised in order to

have most of the bani linj in and out of vats, as well as

tie processes in which direct labor is involved such as
de-l'zairing, done in the dajrli f1 horns. The abor situ-

ation TJill continue b0 be a din icult one in so far as
such phases continue as the difficultv of brc :1king in
new men and tie need of great pr7sical e: m7rtion. Relief
can be nad o1l7 b7 making free use 01 mach;~
the hard jotng :nrl since labor is one of the lar
in the cost of tn

product, as much labor should be saved

.8.

(D

as po sibl'e .

C - TIE ECOT'OIIIC S '17fo IOIT AS IT AFFL CTS EUIT .J/I'Tj; ETD

'I“‘f\ ‘vfij‘vm
1‘4 fill-P- _ -11_. . l

 

need of more and more la or savin” methods bein“

.41
H
o

la M

Q to note the conditions which

*4.

('fr nted, it s intere st
keep the problem from be ing so sirple as one would wish.
The plants are usually old an; low-roofed 7nd are spread

over considerable STO ound area, due to tie necessit7 for

using vats Tille d ‘itn VlriOUS solutions is “71cc ens
hides are trea ed; - further, the >ulldlfl‘” often were con-

ructe d oiece1eal and without too much recourse to

0

surve7ing instruments or stress figures. If labor savinfl

5.

methods proven in oizher industr es .an be made use 01

without too great alt mr tio:;1 to 7xistin; plant, Yell ard
'V3o3, ’” Inst 1 1: - "" ’ 1 giie? ’STcnfie £x7etvfl3ltr is 1:0

surplus in the treasur7 available for re plant, and the
financial reports of the leatier inl str7 for years past

‘sould not tend to i iluce new capital

‘Cl'r‘fi +10 nq—mr -—-—~‘ yj Icnnvx vwfiD u.» n. {‘11-'77 [A I TTA‘VTT‘. TOT yv""mT-CT‘\f‘1
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A—A —o“

 

L 1

u use long been reeogr ized that material handling
is a field which offers very great possibilit’es to those

.1.

who “lo .er proluct ion costs, and the leather (aniery

looks like one place where the material Lanlling expert
an effect worth-while safings. The hides must pass through

vat after vat, each time being lifted with the absorbed
load of liquor through a height of from three to six feet,
and each time h3it75 transported some distance h7 some
means. The primitive method of liitinv
putting in the vat 1.as teen to handle eaer
in and out and W11 sport
narrow gauge trachs over the vats. It is evident tgat
some floor space must be devoted to these tracts which

would better be used for vat space. These old 7vbuOJ 1ne

f

still practiced to a ver7 large extent as cause of the

great difficult7e DOP_3Jde i1en OlC tries to make use of

1»

- 1 .L‘.‘ -1 7-,— 1.. pm 0
naele on b-10 ...a1u.et. i;1OI‘C is no mles-

x'\ V‘ ‘ ‘. ‘ay 4- J“ a ‘ ‘3‘ p . L 'V _ 7 I V'. '3 ‘ '
ln1oor rwrnlire.mn1ts as 14107'1s1ve GJJJ3de cunl.navgnu3 the

1e"a expediting or improving the process-

e - C"OICB F ”TITP"‘"” TO P13? SUIT TY? O"DITIO 113
The situation confrontiag us then when called upon to
1

recon glenl prolaer handling nethoes was, first,

even the it might be

ct

for suitable and stanhL 1d 0111o
something of a compromise; and second, to dOSiTR if

- _ “.1 °. - .. ,1 .’_ H. 1.. ,‘I 1.- 1,. .4, j L'v
necessary machinery for uOlUb the JOPn. “Lei bfl

it is well to cons 1er the design of vats and buildings in
pla11ts of 1 e recent origin in which standard handling

equipment has
in area and the buillings desi
use of

holding a certain number of hides, tne best method being

(D

to fold eacl11f m:i across a stick:rfirhfl11t_s its ends
carried b7 the top frame work of the rack. This rack fits
into the vat and the hides hand freel7 in the liq1J or. The
total weight may be f1o:1 o11e to six tons and even more.

In the case we have to consider however, there are posts

J

throughtout the tanner7 spaced from 16' to 20' and in
sor1e cases the posts are not even in line. The ceilings

are low, averaging from 9' to 10'

Two e11eral lanali g schemes were worked out to suit

two different sets of CODL litions. The scheme which will

be designated as the Eonorail Scheme is suitable where the

progre as of the material s in general along one row of

vets and not acr ss vats,- another requirement of this

 
 

en bein5 that the load should not he more than 2000
elv ee seen t3i1at the monorail
system is a congromise. ihe only reason for its adoption
is its heapness. It is essentially a manually travelled
system because there is not sufficient head room ior
motor travelled telfers or monorail trolleys. Due to the
same restrict ion it is irpos.°31e to use heavy anfl ru55ed

equipment which will 5ive minimum maintenance cost. Its

limitations are treli: Shall capa ity; Fahd travel by

pushing; slow hoistin5 ‘3ecwd aifficulty of f suing
current to the hoi t; line coverage ins toad of area

covera5e ; necess 7? for carefully balancing the loaded

rack; the necessity for feet paths alen5 each row of vats;

the interference of the wn 5in5 rac1-: with each other on

l—vo
l—J

the monora tracks unless the routin5 can be worked out

to avoid this.

1;]

1he scheme desi5nated as the Crane System has no

such linitations as the Lenorail bysten, but in a building
1avin5 a "reat manv rows Ol poses the cost of installing
runways and cranes over each row would be prohibitive and
even if standard cranes could be found . ch would 50 into
the low headroom there soul; still be the impossibility of
easilv carryin5 the ra cl :s from one row of vats across to
another parallel row.1evertheless means were found to

1 o , J L"

aaa “t the travellina crane to the pee Ml ar neeus of the
y e i

.1"

situation and several years or successful service have

proven the adaptability of the Crane System aid its

$

efficiency and low maintenance.

f - D330 {I TIC? O?” IIOI'O :11 SVEJ’TLJTT [LTD ITS APPLICai ICU:

 

.—

Sketches 2-i-BOA and B-Q—LQB saew the monorail

system adapted for one particular department where the

we

lide

('3

can be loaded on the reel :3 directly from the de-

1

hair'ng stands and process d in a fairly stra_5mt li e.

The arrangeaent of tricks and junctions lS sucn that the

racks progress in an orderly manner without int

C.)

Mf rence,
being loaded on track 212-?33-hhd and unleaded many hours
later on track CSO, the ennties being returned on the out-
side track 673 to C5. The tracks are continuous, with no
gaps, and hang from the steel ceiling I-beaus by means of
ordinary belts with spacer washers to permit of leveling
the complete system. Due to the p ss'bility of slippage
and consequent misalignment of junctions clamps are not
used but bolt holes are dr ille in the lower flanges of
ceiling beaxs and the upper flang s of the monorail beam.
The belt heads are placed under the monorail beam flange
with wedge shaped washers and as little room as possible

taken up in order not to interfere w t'

[—70
H4
r—J

C3"

he trolley
wleels. The junctions are a standard design having a
continuous upper member belted securely to the tOp flanges
of the abutting monorail be we hut with openina
lower flanges and webs through which the trolleys may pass.

On the bottom flange at the entering end is a shallow lug

which engages a movable pin on the trolley at the will of

the Operator. when the trolley apgroaches the junction
without engagement of the pin and lug the trolley keeps

on straight through the junction, but when the Operator
pulls a handle engaging the pin with the lug the trolley
is deflected to the right or left as the case may he on

to the curved track. These junctions are made of malle-
able iron reinforced with steel plate tOp and when once
adjusted preperly will remain so pernaneztly. The track
supports are siaced so that very little bending is resisted
by the junctions. The trolleys are of standard four wheel
articulated design with large, ball bearing wheels, altered
as to length so that the center distance of two trolleys
when as close together as possible will not exceed 14".

A small number of trolleys carry small electric hoists
which were found after much search. These hoists have a
capacity of 2000 lbs., weigh only 125 lbs., and take up
very little head room. The balance of the trolleys used
carry only a special double hook as shown on Sketch l-lOe
29B. The hide rack has at its center a Special double eye
steel bail which is also shown on Sketch l-lO-BQB, and
when being lifted by the electric hoist the upper 100p of

the bail is used; when the rack has reached the upper

)

limit of its travel one heck of thr double hook is engaged

\

in the lower 100p and he electric hoist lowered away
until the rack is swung over the distance of 14" until it

centers under the adjacent trolley. The trolley and

electric hoist are then free to handle another rack and

10.

the rack just lifted is pushed away to its destination.
Each hoist carries a length of rubber covered triple con-
ductor cable with a plug on its end for plugging into
sockets located on each post. One man can handle the
racks, and the Operation of loacli ing and unloah :the
racks is much easier than the Old 1et Od of thro ring the
hides on cars. Two manual handlings now instead of at
least six before effects considerable labor saving and
the mechanical handlings almost entirely emove the dis
agreeable phase of this work. One expert is suff icie nt
and the rest may be common laborers of usual strength
and ability. The cost of maintenance is confined to an
occasional overhaul for the hoists a_nl the regular lubri—
cation Of the trolleys. Speed is not a requisite in this
department and the number of vats is sufficient to keep
busy the mini11um number of men which would in any case be
required to man the system, thus giving a very efficient
installation.

The monorail syste1 has the inherent advantage Of
easy eXpansion as evidenced by t1 e fact that the tracks
shown on S1<etch 2-4-29B had not been in use more than a
few months when it appeared that a small extension en-
abled another Operation to be greatly simplified.

g - DES RIPT IOU 0h SPECIALI ELECTRIC OVERHEKD TRAVELIEG
1A"; a? TTELF :SFER SYS‘XT A13 ITSAPPLICAC IOI:

hany departments could not be equipped with the

Monorail System for several reasons, some of which have

11.

been mentioned. For instance, in most cases the ceiling
beams were already loaded to their limit as floor beams

of the second floor. In most cases the capacity of a
Honorail System would not be large enough. To meet the
situation in a complete manner required the use of
electric traveling cranes and the idea was conceived of
equipping every longitudinal bay with crane runway rails;
installing a transfer bridge on runway rails in a trans—
verse bay, and use only one crane. A complete installa-
tion of this nature was made in the one and only depart!
ment where the headroom was sufficient to permit the use
of standard crane equipment obtainable on the market.

It was necessary, however, to alter the crane trolley
design somewhat to obtain a four suspension head beam
lifting rig for carrying the large six ton rack by its
four corners. It was also necessary to carefully design
the crane bridge for an absolutely minimum headroom
dimension. This installation is shown on Ph A where the
crane is in the background and the transfer is in the
foreground. The transferring of the crane from one bay

to another was new because so far as is know this is the
irst installation of its kind. The transferring of mono-
rail cranes on which the trolley travels on an underslung
beam is very common practice and it seened entirely feas~
ible to adapt the same principles to the design of a trans-
fer which would carry a standard double girder crane having

its trolley traveling on the top of the bridge girders.

It will be evident that the transfer must have tracks of
some sort to run on and that as the electric traveling
crane passes on or off the transfer beams it must clear
these tracks. It is equally obvious that the transfer
tracks must be as close to the ceiling as possible with

he electric traveling crane passing under then in order

to minimize the head room required. Two heavy I-bems

were used fastened directly to the ceiling and on the lower
flanges 20 lb. tee rails were bolted, on which the trans-
fer bridge wheels travelled. This would be designated
therefore as an underslung birdge. Half of the wheels are

driven by a 7% HP motor. The structure is designed with

two longitudinal beams carrying rails and mat

O

hing exactly

1

with the runway benas in the several bays. Clearance is
provided for the electric traveling crane to travel clear
across the transfer. In other words when the transfer is
locked in place opposite any crane runway it forms an
integral part of the runway. Two sets of current collec—
tors are provided on the electric traveling crane bridge
to avoid interruption of the travel motor circuit when
crossing the gaps. The safety features consist of two
things; the transfer travel controller is so placed that
it can.be reached by the operator, who rides in a cab on
the electric traveling crane, only when the electric
traveling crane is in proper position on the transfer; an
interlocked locking arran.ement on the transfer locks the

m
L)

crane to the transfer and unlocks the transfer from the

building, or vice versa. Only one lever performs these
Operations and it can be reached only when the electric
travelilg crane is in prOper position. It is therefore
impossible for the crane to run off an Open runway or for
the transfer to be moved without carrying the crane.

,
1

Actual operation has checked the original design of taese
features thoroughly.

A second installation of the crane system was then
made in a department with somewhat les heal-room and
several changes were necessary or advisable on account
of the different conritions. In this case there was a
transverse ridge in the roof providing anple clearance in
one transverse bay for the transfer, but at other places
the clearances were very restricted. It was decided
therefore tha' the transfer should run on two ordinary
f

1

being underslung, and that the

1..)
O

runway beans insteav
hoist would be built into the bridge of the electric
traveling crane between the girders, thus saving about a
foot of room and permitting the crane to run under the low
eaves of the buildih . lhis installation likewise proved
In both Case 1 and Case 2, described above, of the
Crane System, it was necessary to rebuild the vats to
suit the cranes and when it came to studying the other
departments of the plant it was found that such rebuilding
would be prohibitive. Furthermore in both of these cases

the available head room was greater than elsewhere in the

l4.

plant where cranes might be installed, and a decision was
made to try and design a crane transfer system which

would go into about 5 feet Lead room and which would not

require any vat changes except as certain ones might have

l-o.
‘3

to be altered to suit a standard Side of rack. It must
not require too much special construction for the insta ll-
ing of crane and t ansfer run ys. Absolutely nothing in

th

(D

way of complete stands rd equipment could be found, so
design drawings were made which will now be explained.

One very important consideration which had to be faced was
the diffi ieulty that mi ght be encountered in having very
special crazxe ec1uipzacnt built by the usual makers,
especially in busy tidCS. It is generally found that the
work is either refused entirely or else a very fancy price

'V L

charge . To overcome this tie design must be such that

..J

parts could be obtained from standxlo sources and the
equipment assembled in a joboing shOp or in the tannery's

own shop, if necessary.

h - SOLUTION OF PdOeLJJ~ MET 3 TH IN DEbICN OF RAKE
rl1r{“ r_T*(‘1:1 1{ (71er h".
L) -.LL'-A.._J .

Referring to SK- ~O-8-29A, showing the design of Crane
adopted, the following assumptions were made, based on
previous experience with Case 1 and Case 2 installations:

Capacity on four repes - 6 tons
Span - Variable but usually about 80'
Hoisting Speed i 23% PPM

Crane Travel Speed i 250 FPM

Lift - ma. . 20‘

Rack size - Variable but approximately 7' x 10'

1..

Current - 110 volts, direct.

The frame of the crane consists of simple shapes riveted

J

or welded together and great rigidity laterally is pro-
vided by the %” plating on underside of main channels.
The standard mechanical parts are Simple and may be
assembled to suit tne crane dimensions required. Con-
sidering the hoist mechanism first, the component parts

.1.

consist of the m tor wi

| ‘

th motor-mounted solenoie brake,

direct connected to a speed reducer; two rope drums on
the slow Speed shaft of the reducer; idler sheaves for
two of the suspension repes; and the controller having
dynamic braking lowering connections. After considerable
search for a speed reducer that would have a maximum
reduction of BO to 1; that is completely ball or roller

bearing; and tha would not be more than 18” in height;

\f).

L‘J a

with input and output shafts in the sane horizontal pla

r-4’

1

1-1 ..I. .L 1.
bilulb bile S

ecifications could not be met b

U

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B
C]
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C
”5
:1.

PC;

.0 J- 1y ‘- r1. r -. -~ 14" i‘ -\ ‘ r "‘ ..- - ' -
any oi inie auraawxl or.aere irnlacers OKliJM3ilHPLCt. ffliat

the specifications are not too difficilt to accomplish is

;

indicated by the very simple design that was developed

and which is shown on SK-S-ll-BOA. Its depth overall is

16-1/8" and the maximum gear ration is 80 - 1. It will

transmit 10 HP with a Factor of Safety of at least five

I

and its efficiency may be assumed to be over 95%. t may

I

be described as a straight spur sear reducer with four

b

pairs of heat treated steel gears rounte i on t2 ee sq
two of which carry quills; each gear Hitli its nei: gdoorina
pinion is carried between two roller or ball bearinns; he
tn halves of ie cast iron case are exactly duplica
joints are ero askets against oil 1691:8'9, so
that lubrication is by oil bath and need be attended to
only once or twice a year. One reapec in Wiich this hoist
mechanism ‘iffers from the usxal designs is that the drum
shafts and gears are preportio 3 to carry full load

directly from the drum instead of eduCing the load by

"(‘3

multiplying the number of strands of rore supporting the

1.

load. Thi saves head room but requires that all the

03

speed ratio be secured in the gearing, and it increases all
stresses in the parts.

The load of 6 tons is to be carried on 4 strands of
repe but more than half load may be carried on 2 strands
so the size selec ed is 9/16” diar etc r, 6 x 9 best plow
eel, which is good for 21- tons at a Factor of Safety of
t = 5. The drum diameter should be about 24 times the
rope diaW1eter or 151", but 12" was chosen as he pitch
diameter because of the restricted room. The gear ratio
is therefore

600 (F.L. Hotor.Speed) x 5.1416' (drum circus)=:80

(F.L. Hoisting Speed)

The getrs in the speed reducer will be

12-2 5 x lZg X 133 x 153 = 80 reduction
0“ 5 at $1 1%

17.

Although it is Specified that two strands of rcpe shall

be able to carry full loai, the usual method of suspension
will be one rOpe to each corner or near the corner, of the
hide rack. If there are two rows of vats in a bay a head
beam may be used wi h the 4 hoisting ropes attached to it
at convenient points, and with the rack carried from the
headbeam by means of hooks as shown on SK 5-s—29A and SK
6—8—29A. The hooks a1 e adjus table on the beams and will
hook into the bails on raclts by moving the crane bridge
forward. when headbeams are not used simple angle spac-

J.

ers are used between the four hooks to hold them in
alignment because in no case is it necessary to use a
ground man for hoolzing the load. In some cases automatic
self-locking hooks are used which enter the bail and lock
securely by simply movingt ne bridg e for*n ard, and vice
versa. Racks of any size witiin the span and capacity of
the crane niay be handled by this arrar WGIOIt and racks may
be moved transversely within the crane bays by making use
of the transfer to be described later. The hoist motor

horsepower equals

19000 x 85 .5. = 10
55000 X .8 5

 

For the sake of standardization of parts all bearings
on the crane outside of the speed reducers are exactly the
same; the bridge axles and the drum shaft are the same
diameter; and the speed reducers are the same except that

the bridge reducer has only two pairs of gears with a

18.

reduction of 72, arrived at by the use of gears as follows:
12-2 5 x 15$ = 7%. By using a 250 volt motor on the 110
U
volt crane Circuit the gear re atio can be Obtained more
L1.

easily; and with 12" diameter wheels b 113 ratio will be:

558 (F L. motor speed) X 5.1416 (circum. of wheels)=;8
250 (F.L. travel Speed)

A full torque solenoid brake is mounted. on the hoist motor
to hold the load when stationary and suspended, and a half
torque bra‘1ce is mountei on the eridge travel motor to de-
celerate the crane and hold it when stationary.

The simple daa si gn of a standardized bearing is shown
on SK 5-15-2 9A. The very much greater core t of roller

A”

hearings on the 2-15/10 shafts resulted in a deci.ion to

L0

use babbitted bearings out.ide of the speed reducers with

low bearing pressure and Alemite pressure lubrication. It
is to be noted that the we1ght of crane and load is hung
on the bearings, calling for extra large bearing bolts.
The idler sheave pins and the idler wheel pins are of
the same size and the method of mounting both is very
flexible as to location. The wheel as m1bly construction
used is such that the driving wheels are overhung while
the idler wheels are of standard pin tfipe, and the great-
est dimension from center of runway rails to face of posts
is 2%, 1vhich.with4 3” minimum clearance gives 5" from
centre of rails to face of pea ts The total height of
the crane above the runway rails is 15". Both of these

dimensions are exceptionally small for a 6 ton crane,

especially so in View of the very rugged and rigid deSign.
A narrow stand-up type of suspended Operator's cab close

to the floor permits the Operator to step in and out

d-
(,2)

easily. The two controllers for hois nd bridge travel

1

are mounted in the cab over the operator's head with

handles hanging downward.

The assembling of the various units in this design
in the tannery's own shop is a comparatively easy matter,
assisted by the use of flexible couplings between the
motors and the speed reducers. All material outside of
the speed reducers, drugs and bearings, which are Special,
is easily procured from known sources and a few of the

1
r

Special parts are carried in stock whicq means that

}-\J

cranes can.be built at any time without Special drawings
and in record time.

Referring to SK 6-15-29A this design drawing shows
the type of transfer adOpted for installations where the
dimension from floor to ceiling is only 9 feet, embodying
the same principal of carrying the crane bodily as
described for Cases 1 and 2, but differing in design and
clearances.

The clearance over the crane just described when
traveling along he longitudinal crane bays is 5”, i.e.,
there is a distance of 5" from the highest point of crane
to the lowest point of the ceiling. The transfer Operates
in a transverse bay Where the ceiling is 4" higher than in

the longitudinal bays, and the problem was to put the

rails for carrying the transfer into this dimension of 4”
'7”

plus 0 , or 7”. Iith any standard construction at least
a 15” beam would be required and some clearance in addi-
tion, probably 8” in all. This problem was solved by

doing two things: makin

an

O

pen ended transfe , and

.'

using a swinging transfer runway bean adjacent to tne
C°ane tracks. For such a scheme the transfer must be
installed in an end bay because the crane cannot run onto

both sides of it. The transfer runway track next to the

|_J

end of the buildirs is of u I-beam construction sur-

. . ‘
~.4

ll T
' 4.

03

mounted by Tee rail, waile the track at the entrance side
of the transfer consists of len; as OI 18” heavy ship
channels with a Tee ra’l fastened to the inside of the

lower flange. Opposite each crane bay is a swinging

section of this trac< suspended by means of Special

*3in5 sections are Short fixed sections. The trans-
fer end truck on the wall side is of usual construction

and the same as the crane end trucks, but at the entrance
or Open gap side there are two trucks, each with a double
flanged wheel running on the channel track Tee rail and
with a plain tread wheel running on the under side of the
ship channel; the Section of beam correSponding to the

J,

crane runway tracks, RdiCh is carried by the transfer, is

[—10

thus cant levered on these two trucks, permittins the
crane to pass on to the transfer by sninsins the section

of transfer track out of its way. This is done by tw

deflector bars on the crane, one on each end. Only the one
section Opposite the crane bay in which the crane is
traveling swings and the transfer cantilever trucks are
carried by the adjoining sections. Horizontal alignment

is preserved by the fixed trarsfer track on the \Jall

Side and the transfer is locned on this side. The trans-
fer travel controller and the locxins
located exactly as described for Cases 1 ans 2 transfers.
The travel motor, Speed reducer, axles and wheels are the

same as on the rane. The idler nieels, however, are over-

hung and ca ried on lon 3squaring xles the sane as the
driving nh vels in order to ass’st in keeping the transfer
structure from getting out of line.

The crane Operators become very expert in spotting

the transfer, and the transferring of racks Ol hide from

bay to bay is done very quickly and smoothly. There ar

CL)

no complications in the machinery; the neintenar ce resuire;l
is confined to daily Fressing of a few bearings and an
occasional inspection; and o~e crane with its transfer

will cover every square foot of vat space in the building.

lurtnerm01e, the initial cost is less than that of stania rd
crane equipment, irsteid of greater as would usually be the

1

1y euilt equipment.

0
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140
D
{._.l

COITCLUS IOU:

 

fi‘I .

It has been the intention in this paper, not to set

forth tne comp arativelv Sllple calculca tions necessary for

L

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1;; {a o

the design or preper preportioning of :a‘ts of the equip-

to
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b
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(a

ment, but to indicate by example ° that actually

_J.

been done, how important it is for an eng_ne when

(I)
’2‘»

..

faced with problems, whether usual or unusual, to

approach his problea with an open mind and with the

n o o

'v'. '. 1 ‘ t 1 '." r .~- ‘ n ‘3 a "1 - 1- .'~ - ~ <
exerCise Oi as much ina,ination aid iflQOHULLV as

1e is

p_..a

capable of. It is wise to assume that it is usually

quite possible to perfora the inrossihlc when the

.~' ~ F1H'.1,~ . v x" ;-.‘- -. i“ .- M 4‘1‘.\ ’- 1‘. - ~1— \ - “A.
inpossiole is simply soue A115 that has not been HJHG
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ocfore. Lse nas oezn made Oi the cesi n arasia»s and

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