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THESIS

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GEORGE T. BENTLEY
1919

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TESTS ON A HYD nO-}PNSUMATIC PRESS

THESIS
Submitted to the Faoulty of the
MICHIGAN AGRICULTURAL COLLEGE

GEORGE T. BENTLEY

Candidate for the degree of
Bachelor of Science

EAST LANSING, MICHIGAN
september 1919,
THESIS
-L=-

TABLE OF CONTENTS

Title --o—o om — oa OOO OBO Bea e2ne2e2eaaea foe Soe ne ee eewee)

Acknowle Agmen t8--- mewn women wewowownownn OE @ BE ONO NSBHlA OBE eceeel

Introduction-----=- Om me ew nem enn mmm wn ew owen wn wm none wmnnnenewng—§
Pur po06@------- orem mmm mmm enn mn mmm meen meen ee nenee wnen nnn §-7
Description of the Machine---------.--28 seen nn see en en nee ~==8-9
Pictures------------------------.-----=-------------------- 10
Suggestions for improvements-------- en mew nn nn cmwwcenne ewneel 1-12
Theoretical check of body for strength---<------ weenenewenn ] 3-16
Testing of force fits-- een ennn--- omen nn nen swan anne nnone eree] 7o2]
Conolusi ons---<------- wseeneee eeweononce m meewewnn www eenne ne 22
Assembly drawing------ wa nnennnnnene------- inside back cover
of . age}
The author wishes to express his gratitude to the
following persons and authorities for aid in conducting

these tests and for information given.

MR. H. B. DIRKS, #rofessor of Mechanical Engineering ,
Michigan Agricultural College.
Mr. G. C. Wright, Foreman Machine Shop, Michigan Agricultural
College.
Mr. C. Ae Holdridge, Chief ungineer, dydraulic Machine Department,
Eastern vrroduction Company, Detroit, Mich.

AUTHORITIES
Handbook for Machine Designers, Shop Men and Draftsmen

F. Ae Halsey.

Elements of Machine Design
Kimball and Barr.

93904
o4 =
I
INTRODUCTION

The Eastern Production Company of Detroit, Michigan has
placed in the Machine Shops of the Michigan Agricultural College,
for the use of her students, a Hydro-pneumatio Press which

promises to be of great use to them.

The machine was placed at this College through the
kindness and good will of Mr. A. P. Corrigan, who was at one

time a student at M, A. C.. and is now at the head of this

Company.

The Eastern Production Company is at present making
hydraulic and hydpo-pneumatic presses of various sizes to a
large extent. They have as the Chief Engineer of the Hydraulic
Machine Department, a man of some ability in the design and
construction of this type of machine, Mr. 0. A. Holdridge.

Mr. Holdridge's latest design is this hydro- pneumatic
press, one of which is in the Machine Shop of this College
today. This machine seems to be meeting with great success in
many shops as a Solution to problems in the quick and accurate
straightening of both rough stock and machined parts, and in
many other jobs for which a lirht »ress will be a saving in

time and money.
Mr. Corrigan in placing this machine at the disposal
of the College, wished that it be used hot only as an adjunct
to the Machine Shop equipment, but that it should also acquaint
the student with the use of this type of machine in modern shop
practice. The men who go from this college will be the manegers
of the near future, and if at this time the usefulness of a
product can be impressed upon them, it will probably be their
Ghoice when they have a job to do for which this machine is
fitted.

Such a gift is of great benefit to the College in that
it is a clear proof that her Alumni are loyal, and willing to do
whatever is in their power to assist their Alma Mater, and that
they consider the College as a real live factor in the Business
World.
- PURPOSE
In casting avout for a sudject on which to write a
thesis, Professor Dirks suggested that the author might in-
vestigate the possibilities and uses of the Hydro-pneumatio
Press, which had been donated to the College oy the Eastern
Production Company of Detroit, Michigan.

The machine is rather an innovation along this line
and its possibilities have not as yet been given a thorough and
painstaking inveatigati on.

At first owing to lack of data and knowledge about the
uses of the machine, it seemed as if the variety of work. which
could be done along this line was very small, but after several
trips to Detroit, and talks with Mr. Holdridge, the Inventor,
the number of tests and the amount of data which could be made
and found was 80 augmented that finally it was necessary to
narrow the tests down to three or four things which we propose

to carry out.

Since the machine is now in manufacture, the Inventor
believes that several improvements can be made in its design,
and in the care of its machining the first thing to do is to
inspect all the machining and assembly work to see if anything
could be improved here. Then to find its weak points in design

and suggest their remedies,
=] a

Second,to check the design for strength, especially the
G-frame of the body to see if it is made sufficiently strong to
hold up under the load it has to carry.

Third, to make a study of its uses and tabulate such

data as may be found useful.

The machine was primerily designed for the accurate
straightening of work, such as short shafting, and it was the
authors intention to give the machine an exhaustive test in
this. However, due to the fact that it was impossible for the
ocllege to obtain the necessary attachment for doing this work,
and as the machine is also useful as our arbor press, it was

decided to test it in this capacity.
II!
DESCRIOTION OB THE MACHINE

- The main features of the machine are a piston and piston
rod in the base actuated by compressed air. <A high pressure

oil well and a high pressure ram actuated by oil pressure.

Referring to the assembly blue print accompanying this
work, it will be seen that compressed air enters the intake at
a pressure of between seventy-five and a hundred pounds gage,
and passing through the two way valve enters the large cylinder
at the base. The piston is forced upward, and the piston rod
compresses the oil which fills the cylindrical well and curved
channel in the body of the machine. This compressed liquid pushes
down on the ram(20) with a maximum force of approximately fifteen

tons depending on the pressure of the air in the base.

When the-two way valve is thrown to its opposite opening
the air under the piston. is released and new air rushes in on
top of the piston foroing it down. The oil pressure being re-
leased, the ram returns to its highest position through the
action of the coil spring(24).

The reason that such a high pressure can be attained on
the ram is, that the area on which the compfessed air acts is
much larger than this area acting on the oil, The pressure per
Sq. in. of air and oil rewpectively are inversly proportional

to the areas of the piston and piston rod.
ao Jan

The cup leather packing( 365) makes an oil tight bearing
on the ram, and the packing gland(17) makes an oil tight bear-
ing on the piston rod. There is also an oil tight bearing in
the packing gland on the ram return guide rod (23). Fhe surface
between the cylinder and cylinder cover and between the cylinder
cover and the body are kept tight by means of studs holding plane
surfaces between which is inserted a packing of heavy drawing

paper heavily shellaced.

The machine has a round table with a hole bored in
the center which gives an excellent attachment for making press
fits and shrink fits. It ia useful for all kinds of mandrel work,
or any work in which it is necessary to press two or more pieces
together with great force. ‘The Company also manufactures a table
for straightening work from Six inches up to two feet in length
which is very quick and accurate, it being possible to get an
accuracy of two-thousandths of an inch, according to stagements
made by representatives of the menufacturer. It is unfortunate

that the College has no such table as some interesting work could

be done on it.
“lle

SUGG SS TICNHS *OR IMPROVGMENTS

after dissembling the machine and examining the work-
manship, it was assembled and tested at a high pressure. The
following are some of the faults which were brought to light,
ana suggestions are here made for their improvement.

1. The filling and drain plugs for oil are merely screwed
into the cast steel body and if they are hot carefully
coated with white lead each time of removal and screwed
in very tight they are pretty sure to leak oil when the
pressure is high. Since it is unnecessary to remove
the drain plug often, it is not thought necessary to
change this construction, but there is elways some oil
leak making it necessary to refill the oil well, and a
good sturdy filling cock is needed here.

2. The machine that is in the shop leaks some oil past
the cup leather packing at the top of the ram. This
in itself is not a bad fault if the o1i1 would not fall
on the operating table,so the suggestion was made to
Mr. Holdridge that an oil groove be cut near the bottom
of the ram cylinder, and a small pipe lead: off to one
side to drain the oil away from the table. However,
at the time Mr. Holdridge had already made what he
thought was a cheaper and better improvement. He
cored out the ram. cylinder leaving a bearing surface
about two inches long at the bottom,and then placed a
packing gland below this.
-12-

The top of the ram is to be guided by the return guide rod
(27) through its packing gland (23).

3. The flange for the studs which join the body and the cyl-
inder cover is of poor construction, ani it is very difficult
to tighten the studs wnough to keep the drawing paper pack-
ing from blowing out. Mr. Holdridge, however, telisme that
this has veen improved in later machines.

4. The machine which is here in the College is »out together
very carelessly, and there were some cast iron chips lodged
between the cup leather packing and cylinder wall at the
top of the ram, which accounted for a part of the oil leak
at this place. There was quite an accumulation of core sand
on and avout the large cylinder, which if allowsd to stay |
there and the machine be used much would soon make a leaky
piston. Mr. Holdridge was informed of these facts and took

steps to get more careful assembly.
~13-
Vv
THEORETICAL CHECK OF THE BODY FOR
| STRENGTH

From the appearance of the G frame vody, it was thought
to be rather weak at the center, so an extensometer was put
on the machine to determine the amount ofr strain under difrer-
ent loads. This extensometer is shown set up on the machine
in one of the photographs. A tanulation of the strains is

shown velow;

 

 

Load right left dixfrerence dirference average
tons dial dial right dial left dial difference
S838 enn a a =
1 25.5 21.5 2 3-5 2075
2 28 18 4.5 7 5.75
3 20 4 15.7 6.9 10.7 8.8
4 33.26 13.5 10. 12. ll.
5 3602 10 2 12.7 14.8 15.75
6 40 8. 16.5 17. 16.75
7 42 5.4 18.5 19.6 19.05
8 44.8 Be 21.3 22. 21.65
9 47. o& 25.5 24.6 24.05
10 #50 -2 26.5 276 26.75
ll 52.6 -5 L296 3. 29.5
12 += ng -8.4 51.5 23544 52.45
13 58. -10. 34.5 35. 54.75

 

 

REMARKS: All measurements are in thousm athe of an inch at

the center line of the ran.

Owing to low air pressure, it was impossible to get

more than a load of thirteen tons.
— 42

14

HORIZONTAL CROSS SECTION THROUGH THE CENTER OF THE G FRAME OF

A 10-15 TON HYDRO PNUEMATIC PRESS

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. 0 Gravity

 

 

 
From the forgoing data it appears that the structure
may be too weak to take the stresses of a full load so it will
be wise #o check its strength. Por dimensions of the section

in doubt see the sketch on page 14.

Consider the frame to be in the form of a hollow circle
tangent to a rectangle, the material peing cast steel, then:
Area of the hollow circle a 3.1416 x (2.26) minus 3.1416 x
(1.5)” aoe 9 Bq. ine
Area of rectangle a 1.25 x 5
a= 6.25 sq. ine
Making moments anout the axis X------ X to find center of gravity

C. G.= 9 x 3.5 plus 6.26 x 6.25 = 2,352"
15.256
Taking the maximum load to ve fifteen tons and the allowaple
fiber stress fox cast steel to ve 10000 lba. in tension.

Te reach of the machine is 7",
p= P+ Pae
e Fr
« 30000 lbs.
as 15.25 Bde ine
ws 7 + 2.528 = 9,32 ine

2ede
97.63 for this section

MO © & tu

p.= 30000 + 30000 x 9.32 x 2.32
t T5556 "OF 65 -

Po 8620 1ps/sq. ine

Which is a safe load on cast steel.
-16-

Checking for compression on the pack of the frame.

P” 30000 + 380000 x 9.52 x 3.435
15.25 97.65

P = 7880 lps/sq. in
CG
-17-

VI
TESTING OF FORGE FITS

To test the usefulness and capacity of the machine, it

was found desirapdle to make some force fits of cast i@on hubs

(
¢

or rings on steel shafts.

From Halseys Handbook it was found that for reamed holes
in cast iron hubs and steel shafts ground to size the machine
would handle avout a maximum allowance of three thousandths of
an inch. The ratio of the outside diameter of the hub to the
inside diameter to be three.

Following are tapdulated dimensions of the rings and the
shaft.
RINGS OR HUBS

 

outside diameter inside diameter

  

 
  

             

 

 

 

 

R Te eh mater 1.al_
e Re De

2 " fA) 1 1/2 Ww 1/2 " cas ron
3 ] "” 1 1/2 " 1/2 " re r
la " 9 3 " 15/16 in, s of
‘2a " F 3 " 15/16 " " n

Sa rT) wn 3 " 16/16 " 7 v9
4a 7. 3 " 156/15 * " "
5a . 3 . 346/16 * " "
1b _— 41/2 " 1ij/e " nooo

b 4 1/2 11/2 " " "

SHAFTS
No. Length of diameter of allowance for material
ground surface ground surface force fit |
e e e co TrOLied stee

2 - * 502 e002 " " "
3 . FF e503 2003 " " "
la " * 9385 e001 " " "
2a " 8 09398 e002 " " "
3a 7 8 09405 e003 " " "
4a 7 f 093585 e001 " " "
5a ." «9385 e001 " " "
lb . *f 1.501 - e001 " " "
2b " f 1.502 e002 " " "
3b " f 1.503 2003 " " "

 

 

The shafts were made slightly longer thah &.in¢ches
ang 8 taper of ten degrees given the end to give an enterthg
guide
The shafts were now forced into the hubs on the hydro-
pneumatic press and the pressure required noted. They were
then forced out again recording the pressure required to start
them out and forced in again on the Olsen Testing Machine in
the Engineering Laboratory at M. A. C.

Three specimens of the game size and allowance namely;
15/16 in. diameter and .001 thousandths allowance, were forced
in in different manners for purposes of comparison. Wo. la was
forced in on the hydro-pneumatic presa. No. 4a was pressed in
on the same press, but without lubricant. No. 5a was forced in

on the Olsen Testing Machine.
REOORDED PRESSURES ON 10-15 TON HYDRO-PNEUMATIC PRESS FOR

FORCE FITS

 

 

 

 

 

No of diameter allowance pressure to maximum Lubricant
jece _ start tons pressure

“I TE ine O01 1 ° Machine ofl
2 1/2 ing ,002 1.5 . " "
3 1/2 in. 2003 1.5 345 " "
la 1 /16 ine e001 0.5 2. " "
2a 15/16 in. 2002 0.75 4e " "
3a 15/16 in. .003 0.5 5. " "
lb 1 [2 ine eOO1 0.5 5. " "
Ph 11/2 in. .002 0.5 4. " "
3d 1 1/2 in. 003 1.5 Ae " ®

 

 

RECORDED PRESSURES ON OLSEN TESTING MACHINE SHAPTS HAVING BEEN
PREVIOUSLY FORCAD IN ON THE HYDRO-PNEUMATIC PRESS AND WITHDRAWN

 

 

 

 

 

 

No of diameter ‘allowance pressure to maximum iuoricant
piece etart tons pressure
tons
T 1/@ in. OL tC ene ° machine oi.
2 1/2 in. 0002 0.2 225 " "
3 1/2 in. «003 0.5 1.8 " "
la 15/16 in. e001 0.2 1.6 " "
2a 15/16 in. .002 0.5 2.7 " "
3a 15/16 in. »0035 0.5 325 " "
lb 11/2 in. .001 0.6 4.5 " "
2b 11/2 in. .002 04 2.6 " n
3b 11/2 ine .0023 0.5 1.6 " "
REMARKS: It will be noticed that the pressure required to force

the three different allowances on the 11/2" rings does

not increase directiy as the allowance, out on the

contrary decreases.

It is thought that this 18 due to

faulty reaming of the holes in that they were slightly

out of round on specimens 2b and 3D.
-21-

Three specimens of the same diameter and allowance were

forced in under different conditions as follows:

 

No of diameter  allowane pressure to maximum Lubricadt

iece start tons ressure tons
Fins! PRESSURE AcPLIED OB HYDRO-PWEUMATTC PRESS

 

 

 

 

la 15/16 in. e001 0.5 2 Machine oil

le 18/16 ine <0Ol 0.2 166 Machine ofl

" SCRME PRESSURE ADPL

5a maa in. 000 0.28 2.58 Machine oil
PhS STRE APPLIED ON THE HYDRO-PREOMZ WAC HINGE

NH. B. The s pecimen was cut for lack of lubricant and it was

impossinle to farce it home on this machine

 

 

PRESSURE NECESSARY TO START THE SHAFTS OUT ON THE HYDRO-
PNOUMATIC PRESS AFTER THEY HAD BEEN LEFT IN ONE DAY.

 

 

 

 

 

Wo of afameter allowance pressure required tons
lece to start
1/@ in. 2eOOL 0.5
2 1/2 in. 002 4
3 1/2 ine e003 3
la 18/16 in. 001 2
2a 15/16 " 002 3
3a 15/15 * 2003 6
1b 1 i/2" 2001 6
2b 11/2." 0002 4
3b 11/2" e003 4

 

 

 
VIL
CONCLUSIONS

It is the opinion of the investigator in aw far as he
can judge from the tests, it Was ,ossible to make, and with
not having tested the machine on the work for which it is the
most used, namely; the straightening of short shafting etc.,
that it will give satisfa tica in its capacity when the sSugrest-

ed improvements have been made,

Phe data here ziven on the power required for press
fits shows that considerably larger allowances could be used
on this machine. Halsey's Handbook & ows that larger allowances
on ground shafts and reamed holes Would take considerapdly more

power than the machine is opaple of.

The data also shows that it is impossible to make a
press fit of this kind withomt lubrication.
OOM USE ORLY

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