I am installing a small I beam trolley in my work shop that can lift a 1000#
max size of beam is important because of head space so I am looking for
information on length and sizing and capacity of beams

Ed

wrote:
I am installing a small I beam trolley in my work shop that can lift a 1000#
max size of beam is important because of head space so I am looking for
information on length and sizing and capacity of beams

Ed


length of beam and method of supporting said beam are pretty big
factors , a four inch i beanm will carry that load if properly supported

i use a program called beam boy for sizing beams at work , it is
free-ware , just google beam-boy

On Fri, 17 Mar 2006 16:45:26 -0600, WILLIAM HENRY
wrote:

wrote:
I am installing a small I beam trolley in my work shop that can lift a 1000#
max size of beam is important because of head space so I am looking for
information on length and sizing and capacity of beams

Ed


length of beam and method of supporting said beam are pretty big
factors , a four inch i beanm will carry that load if properly supported

i use a program called beam boy for sizing beams at work , it is
free-ware , just google beam-boy

Second that comment. I used beam boy to size the 27ft long beam that holds up
my workshop roof.


Mark Rand
RTFM

Anyone have any luck w/ this download? The various primary/secondary
download sites (at geocities, prodigy, or Getze's page) ain't workin.
--
Mr. P.V.'d
formerly Droll Troll
" wrote in message
om...
I am installing a small I beam trolley in my work shop that can lift a
1000# max size of beam is important because of head space so I am looking
for information on length and sizing and capacity of beams

Ed

Never mind... seems to be working (finally) from he
http://www.geocities.com/richgetze/
--
Mr. P.V.'d
formerly Droll Troll
"Proctologically Violated©®" wrote in message
...
Anyone have any luck w/ this download? The various primary/secondary
download sites (at geocities, prodigy, or Getze's page) ain't workin.
--
Mr. P.V.'d
formerly Droll Troll
" wrote in message
om...
I am installing a small I beam trolley in my work shop that can lift a
1000# max size of beam is important because of head space so I am looking
for information on length and sizing and capacity of beams

Ed

How did you determine what an "acceptable" deflection would be? Building
codes?
--
Mr. P.V.'d
formerly Droll Troll
"Mark Rand" wrote in message
...
On Fri, 17 Mar 2006 16:45:26 -0600, WILLIAM HENRY

wrote:

wrote:
I am installing a small I beam trolley in my work shop that can lift a
1000#
max size of beam is important because of head space so I am looking for
information on length and sizing and capacity of beams

Ed


length of beam and method of supporting said beam are pretty big
factors , a four inch i beanm will carry that load if properly supported

i use a program called beam boy for sizing beams at work , it is
free-ware , just google beam-boy

Second that comment. I used beam boy to size the 27ft long beam that holds
up
my workshop roof.


Mark Rand
RTFM

Proctologically Violated©® wrote:
How did you determine what an "acceptable" deflection would be? Building
codes?


i personally use the moment and bending stresses , and a safety
factor of 3 to four , with 36000 psi being a standard for most beams you
dont want to get over 9 to 11 k in the bending and moments , you will
see deflections of less that 1/16 inch for a properly designed beam ,
while anything over 1/8 inch you will see the bending and moment
stresses edgeing up into unacceptable levels

On Sat, 18 Mar 2006 01:42:20 -0500, "Proctologically Violated©®"
wrote:

How did you determine what an "acceptable" deflection would be? Building
codes?

I Googled for building codes (this is in the UK and there are some fairly
clear and simple national regulations). I also looked for more general-purpose
architectural stuff relating to things like "acceptable beam deflection".

IIRC the number that popped out was a deflection of 1/400th of the span was
acceptable for a roof beam. This worked out at 0.81" for my beam. I designed
for 0.4" when supporting the entire roof load. Effectively this was a 4:1 over
design. I made no separate allowance for snow loading, since the worst snow
loading in this area is two or three inches a couple of times in the last 50
years.

When the walls were built and the roof beam was up, but without the roof on
it, the beam was noticeably springy if you jumped up and down on it. Once the
roof was fixed on to the walls and beam, the whole lot became pretty well
rigid in feel when walking over it. More so than a typical wooden floor in a
house. Roof and walls are both 6" thick SIP's.


Regards
Mark Rand
RTFM

If you are designing a building you use deflection as primary criteria
because what goes in the building needs a stable structure and you want to
avoid floors having a bouncy feel. For cranes you use the moment and
bending stress.as primary and deflection can be greater.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Proctologically Violated©®" wrote in message
...
How did you determine what an "acceptable" deflection would be? Building
codes?
--
Mr. P.V.'d
formerly Droll Troll
"Mark Rand" wrote in message
...
On Fri, 17 Mar 2006 16:45:26 -0600, WILLIAM HENRY

wrote:

wrote:
I am installing a small I beam trolley in my work shop that can lift a
1000#
max size of beam is important because of head space so I am looking for
information on length and sizing and capacity of beams

Ed


length of beam and method of supporting said beam are pretty big
factors , a four inch i beanm will carry that load if properly supported

i use a program called beam boy for sizing beams at work , it is
free-ware , just google beam-boy

Second that comment. I used beam boy to size the 27ft long beam that
holds up
my workshop roof.


Mark Rand
RTFM

In article ,
says...
Proctologically Violated©® wrote:
How did you determine what an "acceptable" deflection would be? Building
codes?


i personally use the moment and bending stresses , and a safety
factor of 3 to four , with 36000 psi being a standard for most beams you
dont want to get over 9 to 11 k in the bending and moments

The AISC standard uses a factor of safety of 1.67 in most cases, which
results in a working stress of 21.6 ksi for A36 steel.

you will
see deflections of less that 1/16 inch for a properly designed beam ,
while anything over 1/8 inch you will see the bending and moment
stresses edgeing up into unacceptable levels

That's a huge oversimplification. A deflection much greater than 1/8" is
acceptable in a long beam, and a very short beam may fail, probably in
shear, before it deflects 1/16".

Ned Simmons

In article ,
says...
On Fri, 17 Mar 2006 16:45:26 -0600, WILLIAM HENRY
wrote:

wrote:
I am installing a small I beam trolley in my work shop that can lift a 1000#
max size of beam is important because of head space so I am looking for
information on length and sizing and capacity of beams

Ed


length of beam and method of supporting said beam are pretty big
factors , a four inch i beanm will carry that load if properly supported

i use a program called beam boy for sizing beams at work , it is
free-ware , just google beam-boy

Second that comment. I used beam boy to size the 27ft long beam that holds up
my workshop roof.


I just downloaded Beamboy and played with it a bit and it works very
well, as far as it goes.

But anyone using it needs to understand that while it may yield good
data on stress and deflection, that's not sufficient to insure a safe
design. The most obvious missing factor re the case at hand, a trolley
beam, is lateral stability of the beam. This is usually not an issue if
the beam is built into a structure like a roof or floor system, but is a
real concern with a beam that lacks intermediate lateral bracing.

Just a heads up to warn against getting lulled into a false sense of
security by a neat piece of software.

Ned Simmons

Ned,

You raise a very good point, one that is often overlooked even in
industrial applications.

For unbraced lengths of beam the maximum bending moment must be reduced
so as not to encroach on the buckling resistance of the compression
flange. I had to do a heck of a lot of digging (for a client) to get a
handle on this since textbooks don't address this very well.

I found what I needed in a copy of the Crane Manufacturers Association
of America, Inc. "Specification for Electric Overhead Travelling
Cranes" , spec # 70. (Spec # 74 is more appropriate for manual cranes,
but # 70 is all I got).

It states that the factor of safety of all hoists is 5, BASED ON THE
PUBLISHED AVERAGE ULTIMATE STRENGTH OF THE MATERIAL.

The booklet contains much useful info, and it gives the following limit
on compressive stress for unbraced, single web-beam, crane runways:

Max. compressive stress = 12000 x A / Ld ; with a maximum of .6 x
yield strength

where A = area of the compression flange
L = unsupported / unbraced length of span
d = depth of the beam, in inches

Maximum shear stress = .35 x yield strength

Maximum deflection of beam not to exceed .001125 inches per inch of
span, based on trolley weight and rated load.

Trust this enlightens a little.

Wolfgang

Max. compressive stress = 12000 x A / Ld does not make sense. 12000 x A
is simply 60kpsi steel with a safety factor of 5 tossed in. L times D
for any reasonable beam will be in the 100's eg 10" beam and 60"
supports would be 600.


wrote:

Ned,

You raise a very good point, one that is often overlooked even in
industrial applications.

For unbraced lengths of beam the maximum bending moment must be reduced
so as not to encroach on the buckling resistance of the compression
flange. I had to do a heck of a lot of digging (for a client) to get a
handle on this since textbooks don't address this very well.

I found what I needed in a copy of the Crane Manufacturers Association
of America, Inc. "Specification for Electric Overhead Travelling
Cranes" , spec # 70. (Spec # 74 is more appropriate for manual cranes,
but # 70 is all I got).

It states that the factor of safety of all hoists is 5, BASED ON THE
PUBLISHED AVERAGE ULTIMATE STRENGTH OF THE MATERIAL.

The booklet contains much useful info, and it gives the following limit
on compressive stress for unbraced, single web-beam, crane runways:

Max. compressive stress = 12000 x A / Ld ; with a maximum of .6 x
yield strength

where A = area of the compression flange
L = unsupported / unbraced length of span
d = depth of the beam, in inches

Maximum shear stress = .35 x yield strength

Maximum deflection of beam not to exceed .001125 inches per inch of
span, based on trolley weight and rated load.

Trust this enlightens a little.

Wolfgang

How would this change for an aluminum beam?

TMT

In article . com,
says...
Here it is EXACTLY as given in the reference:

Compression = 12000 / (Ld / A) with a maximum of 0.6 Yp

I should have added that: L = length of unbraced span in inches
A = area of compression
flange in square inches
d = depth (or heigth) of
beam in inches

Just noticed that in this booklet the unit for stress is ksi, ie.
Kilopounds per square inch.

The job I used it on had a 360 in. span, 12" beam, 5" flange width,
average fl. thickness 1/2" (I'm guessing here).

Plugging all this into the formula above gets you: 12000 / {(360 x 12)
/ (5 x 1/2)} = 12000 / 1728 = 6.944 ksi or 6944 psi allowable
compressive stress.

If your bending stress calcs exceed this you need a beam with larger
section modulus, or reduced loading. In a structure you'd add
bracing or stiffening to the compression flange. This of course is not
possible with an under running trolley hoist.

Sorry for the confusion.

Wolfgang

BTW: From the formula above you can see that the strength of the steel
does not affect the allowable compressive stress. This is indeed the
case for column buckling calculations where the column exceeds a
certain "slenderness ratio": ie. tall skinny columns can be made from
A36 (36 ksi Yp) which would buckle at the same load as the same column
made from 100 ksi Yp. steel. Neat stuff, buckling.WFH.


Very useful information, Wolfgang. The formula agrees exactly with the
tabulated data for unbraced beams in the AISC Steel Construction Manual,
at least for a W8x15 section, which I checked beacause it's the
travelling beam in my crane.

In the past I've seen large factors of safety for cranes bandied about
with no explanation. If I understand your first post, in addition to
limiting stress in the compression flange of the beam based on the
formula, the max stress in the beam must not exceed ultimate tensile/5.
UTS for A36 is 58-80 ksi, so 12-16 ksi max stress, compression or
tension, in the beam. Is that your understanding?

Is this a general factor of safety that applies to all components in the
lifting gear?

Ned Simmons

Ned Simmons wrote:
In article ,
says...

Proctologically Violated©® wrote:

How did you determine what an "acceptable" deflection would be? Building
codes?


i personally use the moment and bending stresses , and a safety
factor of 3 to four , with 36000 psi being a standard for most beams you
dont want to get over 9 to 11 k in the bending and moments


The AISC standard uses a factor of safety of 1.67 in most cases, which
results in a working stress of 21.6 ksi for A36 steel.


you will
see deflections of less that 1/16 inch for a properly designed beam ,
while anything over 1/8 inch you will see the bending and moment
stresses edgeing up into unacceptable levels


That's a huge oversimplification. A deflection much greater than 1/8" is
acceptable in a long beam, and a very short beam may fail, probably in
shear, before it deflects 1/16".

Ned Simmons


On a cantilever beam hoist you want to keep the deflection to a minumum
because with a heavy load it will want to roll down hill in the
direction of the negative deflection. It will take off by itself when
you hoist a load, and that can get exciting.

John

john wrote:


Ned Simmons wrote:

In article ,
says...

Proctologically Violated©® wrote:

How did you determine what an "acceptable" deflection would be?
Building codes?


i personally use the moment and bending stresses , and a safety
factor of 3 to four , with 36000 psi being a standard for most beams
you dont want to get over 9 to 11 k in the bending and moments



The AISC standard uses a factor of safety of 1.67 in most cases, which
results in a working stress of 21.6 ksi for A36 steel.


you will see deflections of less that 1/16 inch for a properly
designed beam , while anything over 1/8 inch you will see the bending
and moment stresses edgeing up into unacceptable levels



That's a huge oversimplification. A deflection much greater than 1/8"
is acceptable in a long beam, and a very short beam may fail, probably
in shear, before it deflects 1/16".

Ned Simmons



On a cantilever beam hoist you want to keep the deflection to a minumum
because with a heavy load it will want to roll down hill in the
direction of the negative deflection. It will take off by itself when
you hoist a load, and that can get exciting.

True enough, but what's "a minimum" in that context? The load needs to
be pinned, held by cable, etc. to restrain the horizontal motion.

Bill

Ned,

A standard section I-beam will have the same numerical value stress in
the tension and compression flange, when subjected to a given bending
moment. There is not much that can be done here. Therefore, if you
keep the compressive stress to the earlier stated limit of 0.6 Yp,
then you will get the same result (opposite sign) in the tensile
flange, Yp (36) x 0.6 = 21.6 ksi. There are slight exceptions to this
which, for home use, we shall ignore.

On custom built beams one can make the compression flange thicker, also
add gusset reinforcings, to allow it to withstand higher buckling
forces. This type of design is generally too expensive for my
clientele because of the design time required.
I stick to what I can pick out of the "Handbook of Steel
Construction" published by the "Canadian Institute of Steel
Construction", second edition, 1975. It still deals in lb, in, kips,
which I am more comfortable with in engineering applications.

As far as I know, the F.S. = 5 applies only to the crane, with the
following exeption: the hoisting cable is a consumable, and its life
expectancy may be increased by using a larger factor of safety on it.
Typically a F.S. = 7 or 8 is used on the hoisting cables. For really
severe duty cranes such as steel mill service (100% capacity loads, x
number of times a day) the factor of safety on the ropes may be even
much higher, including much larger sheave and cable drum diameters. All
this to increase the life time expectancy of the hoisting cable.

At the other extreme is the power house crane which may undergo a
full-capacity lift only half-a-dozen times or so during its life time.
Here the drum dia., sheave dia., cable size, are much closer to the
"average lift" capacity without encroaching on the F.S. = 5.

Under-hook appliances such as spreader beams, pallet hooks, coil hooks,
etc. require a F.S. = 3, based on the yield strength of the material.
The exception are vacuum cup lifting attachments where the rules say
that a F.S. = 2 is required. I don't subscribe to this rule; when I
design vacuum lift attachments I use my own ideas which are somewhat
more conservative. (Ref.: ANSI B30.20-1999. chapter 20.1)

What I AM unclear about is the factor of safety of any building into
which an overhead travelling crane is installed. Normally the building
structure is designed with a F.S. = 1.67. (That's why you can't turn
an ordinary building into a library!)

At Dominion Bridge Company, Limited, where I spent the formative part
of my career, the crane runways were always separately supported on
their own columns. These in turn were laced (shear-braced) with the
adjacent building columns, all moment connected to the concrete column
footings, making for very stiff and sway resistant building walls.
Visually this was a very elegant solution as it provided room for
offices and small storage between the columns.

I suppose a 1.67 F.S. for buildings, even with runways suspended from
the roof joists, is OK provided that you take all loading into
consideration during the design stage of said building, including
accelerations ot the load in the case of electric hoists with electric
traverse. It can get interesting when a client wants to attach a jib
crane to an existing building column!

Trust this muddies things not too badly!

Wolfgang

For an aluminum beam the steel beam calculations would give you 3x the
deflections expected from the steel design.

I would start with the deflection calculations, which, generally would
make the remaining stresses OK. They would still require checking,
though, since it is impossible, for me at least, to tell which specific
conditions apply without doing the arithmetic.

A word of caution on using aluminum: I would not use aluminum in a
hoist application without knowing the COMPLETE history of manufacture
and usage. The reason is that there is a huge variety of Al alloys,
with differing heat treatments, made for differing applications (eg.
architectural vs. structural). Without knowing all this it is
impossible to determine which yield stress to use for design.

You should also be aware that aluminum does not have an endurance
limit, ie. it WILL, eventually, fail in fatigue! That is why it would
be important to know the usage history of the Al beam. Further, was it
subjected to any heating, welding (especially attachments, mid-span)?
Because this would negatively affect the heat treated strength
SEVERELY.

I am sorry to say that I know of no safe way of using an Aluminum beam
of unknown history in a hoisting application.

Wolfgang

Muddies??

How 'bout *dizzying* ?!

..001" per foot is not a whole helluva a lot!

What would you think the the max allowable deflection would be in a W beam
in a building application (floors, roofs, etc.)? Previously cited were
numbers like L/120, L/360, L/720.
For one foot, L/360 is .033" deflection, 33x greater than your .001"!

Is this pushing a failure point?
--
Mr. P.V.'d
formerly Droll Troll
wrote in message
oups.com...
Ned,

A standard section I-beam will have the same numerical value stress in
the tension and compression flange, when subjected to a given bending
moment. There is not much that can be done here. Therefore, if you
keep the compressive stress to the earlier stated limit of 0.6 Yp,
then you will get the same result (opposite sign) in the tensile
flange, Yp (36) x 0.6 = 21.6 ksi. There are slight exceptions to this
which, for home use, we shall ignore.

On custom built beams one can make the compression flange thicker, also
add gusset reinforcings, to allow it to withstand higher buckling
forces. This type of design is generally too expensive for my
clientele because of the design time required.
I stick to what I can pick out of the "Handbook of Steel
Construction" published by the "Canadian Institute of Steel
Construction", second edition, 1975. It still deals in lb, in, kips,
which I am more comfortable with in engineering applications.

As far as I know, the F.S. = 5 applies only to the crane, with the
following exeption: the hoisting cable is a consumable, and its life
expectancy may be increased by using a larger factor of safety on it.
Typically a F.S. = 7 or 8 is used on the hoisting cables. For really
severe duty cranes such as steel mill service (100% capacity loads, x
number of times a day) the factor of safety on the ropes may be even
much higher, including much larger sheave and cable drum diameters. All
this to increase the life time expectancy of the hoisting cable.

At the other extreme is the power house crane which may undergo a
full-capacity lift only half-a-dozen times or so during its life time.
Here the drum dia., sheave dia., cable size, are much closer to the
"average lift" capacity without encroaching on the F.S. = 5.

Under-hook appliances such as spreader beams, pallet hooks, coil hooks,
etc. require a F.S. = 3, based on the yield strength of the material.
The exception are vacuum cup lifting attachments where the rules say
that a F.S. = 2 is required. I don't subscribe to this rule; when I
design vacuum lift attachments I use my own ideas which are somewhat
more conservative. (Ref.: ANSI B30.20-1999. chapter 20.1)

What I AM unclear about is the factor of safety of any building into
which an overhead travelling crane is installed. Normally the building
structure is designed with a F.S. = 1.67. (That's why you can't turn
an ordinary building into a library!)

At Dominion Bridge Company, Limited, where I spent the formative part
of my career, the crane runways were always separately supported on
their own columns. These in turn were laced (shear-braced) with the
adjacent building columns, all moment connected to the concrete column
footings, making for very stiff and sway resistant building walls.
Visually this was a very elegant solution as it provided room for
offices and small storage between the columns.

I suppose a 1.67 F.S. for buildings, even with runways suspended from
the roof joists, is OK provided that you take all loading into
consideration during the design stage of said building, including
accelerations ot the load in the case of electric hoists with electric
traverse. It can get interesting when a client wants to attach a jib
crane to an existing building column!

Trust this muddies things not too badly!

Wolfgang

PV:

Please read my post again: It sez .001125 inches PER INCH! That's
..0135" per foot.

The reason for this relatively small deflection is to keep the power
requirements low on the trolley drive when loaded to capacity. Don't
forget that some of these cranes have large capacities and spans. In
my sphere of responsibilities were 50 ton,132 ton, and 200 ton capacity
cranes, all with a span of 100 feet. The small deflection also reduces
the bounce when inching or spotting a load for assembly.

The deflections you state are for building floors; with the standard
being L/360 and L/480.

Wolfgang

In article .com,
says...
Ned,

A standard section I-beam will have the same numerical value stress in
the tension and compression flange, when subjected to a given bending
moment.


On custom built beams one can make the compression flange thicker, also
add gusset reinforcings, to allow it to withstand higher buckling
forces. This type of design is generally too expensive for my
clientele because of the design time required.


Trust this muddies things not too badly!


Not at all, I appreciate the time you've taken.

I understand that the magnitude of the stress in a symmetrical beam is
equal in the tension and compression members. But since compression and
tension are treated differently in the sort of spans we're discussing,
I'm surprised to hear that fabricated beams are not more common in large
cranes - they're pretty common in bridge construction here in New
England.

Ned Simmons

Ned,

I think I caused a bit of confusion.

The BIG cranes I mentioned earlier I did NOT design, nor was I
responsible for, their fabrication.

They were part of the facilities (Dominion Bridge - Sulzer in Lachine,
Quebec) where I was manager of manufacturing engineering, responsible
for the economic fabrication and machining of hydraulic turbine and
nuclear reactor components. I was instrumental in the procurement of
one 132 ton crane...we had two. All the big cranes I mentioned earlier
were double beam double web custom design / fabrications (box sections
with internal stiffening), with trolleys on top of the beams.

Fast forward 17 years. I now run my own engineering office where I am
'chief cook and bottle washer', with one employee: me!

I offer my services to local businesses that can profit from my
engineering services, which nowadays are often mandated by legislation.

On occasion I am asked to design a small overhead travelling hoist, or
to certify an existing one cobbeled together by who-knows-who.

The 12" I-beam with 30 ft span in my example was a case-in-point of the
latter. I take all relevant dimensions, make sketches and
calculations, and certify the hoist (or equipment requiring
certification) as having a safe working load of xxx lb. For hoists of
unknown origin an inspection is then required by a certified NDE
technician (not me) who checks the welds, bolts, cable, etc. He issues
his report, puts appropriate labels on the hardware, and the hoist is
good to go. Where I design stuff I use material that's available in
the fabricator's yard as much as possible. Keeps the costs down and my
client happy.

Since I design only small hoists it would be uneconomic to custom
design a beam that could meet the differing requirements for the
tension and compression flange. With the load and span specified by the
client and basic calculations, it is easy to simply pick an
appropriately sized beam from the published tables, keeping an eye on
the unsupported length.

It is during analysis of an existing installation that I get into
difficulties. I have to explain to the owners/managers that while their
equipment may not be in danger of crashing down about their ears
(because it has been in use for xx years before the ministry of labour
caught up with them) it nevertheless does not meet regulations, ie. the
legally required factor of safety. Then they want to know why.....

To summarize: Yes, custom designed beams are used for the big stuff;
off-the-shelf material is used on small hoists because of the large
range of standard sizes of beams available, which cover the most often
encountered, smaller, requirements.

Trust this clears the fog somewhat.

Wolfgang

Ps.: I NEVER certify anything I haven't personally inspected. My
errors and omissions insurance is a little too expensive for that.
This is also the reason I do not offer free design advice/information
on this discussion group. WFH

On Mon, 20 Mar 2006 22:23:36 -0500, Ned Simmons
wrote:

In article .com,
says...
Ned,

A standard section I-beam will have the same numerical value stress in
the tension and compression flange, when subjected to a given bending
moment.


On custom built beams one can make the compression flange thicker, also
add gusset reinforcings, to allow it to withstand higher buckling
forces. This type of design is generally too expensive for my
clientele because of the design time required.


Trust this muddies things not too badly!


Not at all, I appreciate the time you've taken.

I understand that the magnitude of the stress in a symmetrical beam is
equal in the tension and compression members. But since compression and
tension are treated differently in the sort of spans we're discussing,
I'm surprised to hear that fabricated beams are not more common in large
cranes - they're pretty common in bridge construction here in New
England.

Ned Simmons


Which reminds me...part of the load I brought home this past week was
5 LODESTAR electric hoists. All but one are 220 3ph, the orphan is 440
3 ph.

No idea if any work or what their issues are. I recently rebuilt a
Coffing J-4 1/4 ton unit for a friends shop. These are rated 1/2 ton

Most are missing the trolly..though a couple do have them. All have
chain buckets,

Anyone in California, interested?


Gunner



"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3

Bill Schwab wrote:

john wrote:



Ned Simmons wrote:

In article ,
says...

Proctologically Violated©® wrote:

How did you determine what an "acceptable" deflection would be?
Building codes?


i personally use the moment and bending stresses , and a safety
factor of 3 to four , with 36000 psi being a standard for most beams
you dont want to get over 9 to 11 k in the bending and moments




The AISC standard uses a factor of safety of 1.67 in most cases,
which results in a working stress of 21.6 ksi for A36 steel.


you will see deflections of less that 1/16 inch for a properly
designed beam , while anything over 1/8 inch you will see the
bending and moment stresses edgeing up into unacceptable levels




That's a huge oversimplification. A deflection much greater than 1/8"
is acceptable in a long beam, and a very short beam may fail,
probably in shear, before it deflects 1/16".

Ned Simmons




On a cantilever beam hoist you want to keep the deflection to a
minumum because with a heavy load it will want to roll down hill in
the direction of the negative deflection. It will take off by itself
when you hoist a load, and that can get exciting.


True enough, but what's "a minimum" in that context? The load needs to
be pinned, held by cable, etc. to restrain the horizontal motion.

Bill


Every cantilever hoist that I have used never had any restraints or
locks for horizontal motion. Most of the heavier ones ( 2 and 3 tons)
have the cantilefer arm with a secondary turnbuckle rod between about
2/3 the was out on the horizontal and back to the upright above the
attachpoint of the horizontal beam forming about a 30 degree triangle.

John

snip

i was pointedly being really simple , there really is no point in "P.E."

engineering in a hoist to unload a 1/2 or 1 ton pick up , some basics
will get you all the way home , while 1.67 is a standard in A.I.S.C.
work , there is not a crane, hoist or any other lifting device built
using that small of a safety factor , as shifting or otherwise unstable
load can load that system well over its rated factor very quick .

example would be an overhead crane rated for 70 tons is built to
a safety factor of four . and i have personally seen a 35 ton injection
mold break an eye bolt and bring the whole thing to the floor .


safer is heavier and more expensive

"Brian Lawson" wrote in message
...
On Mon, 03 Apr 2006 20:55:48 -0500, "c.henry"
wrote:

SNIP

example would be an overhead crane rated for 70 tons is built to
a safety factor of four . and i have personally seen a 35 ton injection
mold break an eye bolt and bring the whole thing to the floor .
SNIP

Ohhhh....what happened? Care to elaborate on that a bit??????

Take care.

Brian Lawson,
Bothwell, Ontario.

Looks like an eye bolt broke, and the whole thing came down on the floor.

HTH.

Steve

well to elaborate , my crew was in a customers plant repairing the
threaded platen holes on a 3300 ton injection molding press{ read pretty
big] and the companies die setters were moving a 35 ton ford trim
molding die across the aisle to another area , did not have anything to
do with our guys or the machine we were working on at the time . I just
happened to be doing a little proactive pocket management while watching
the thing move.

their first error was they had the die hanging at an odd angle using
unequal length chains to the four corners from the main hook .

second problem was this plant has a mix of American and metric dies

and a mix of American and metric lifting eye bolts , you know the
really fancy swiveling kind .

wrong bolt , wrong hole , load broke free on one end , swung to vertical
and yanked the whole dam crane down on the floor , i can still close my
eyes and see it , then i have to pee real bad !!!

nobody was hurt real bad , but it took 12 riggers to clean the mess up
and put the crane back up , the carriage was a total loss , replaced it
outright

The question might be better stated as "why would a 70 ton overhead
crane with a safety factor of four fail when a 35 ton weight snaps off
one mounting point?"

I have a guess... the loss of a lifting point unbalanced the load,
causing forces at an angle to the crane.


Steve B wrote:
SNIP
example would be an overhead crane rated for 70 tons is built to
a safety factor of four . and i have personally seen a 35 ton injection
mold break an eye bolt and bring the whole thing to the floor .