I want to build an overhead "H" shaped frame for LIGHT lifting. The frame
is for between two containers that are 15'6" apart. They are reasonably
accurately oriented parallel and level their tops.

I was doing a cut schedule layout, and saw a couple of things.

Originally, I was going to put vertical posts coming down and resting on a
plate on concrete. Then I thought that I could span the whole thing with
one piece, and rest it on the top of the containers and make two span
supports.

My end goal is to have two parallel spans perpendicular to the containers,
10' apart so I can lift half my 16' aluminum boat with each span. I could
achieve that with just putting two pieces of 3" x 3" x .120" across there.
The lifting points would be outward from center, about three feet from the
container, so I would not be lifting the heaviest thing at the center of the
span. (One end of the boat would be heavier than the other. I want to be
able to lift the boat and pull the trailer out to work on it at home.)

I want one perpendicular center piece, forming a big H. The long legs will
be 15'6", and the short leg 10' long.

Am I okay to use this idea, and just rest them on the top of the container
on plates I shall make? Or should I put a support pole along the containers
for a total of four support poles?

Should I make any "A" shaped reinforcement along the top of the two spreader
bars to give the center a little more strength? Then put another short
piece between the apexes of the vees to give it more strength?

Does anyone know how to calculate what the lifting strength of the 15'6"
beams would be?

I mainly want this to lift items on to and off my welding table, and to turn
pieces of fencing and gates during manufacture. Total weight, 200# max.
The boat, I would say, with motor, weighs 1,000# max, but the lifting points
would be outboard of center, I'd say the boat is 6-8' wide, so I would have
about 8' divided by two on either side of the boat, putting more strain on
the beam closer to center, not in the middle.

I do know this is for light lifting. I have a lot of experience in rigging,
and know how to do a lot of tricks in lifting.

I personally think that if I put a vee shaped piece on top of each beam,
about 8' wide, and 140 degrees at the apex, that would give me more
strength, and help support the middle, hence less sag and more safety.

The end product would look like a house from top plate up, except for side
wall plates. End plates, vee truss, connector, and peak beam.

Input?

Steve

Steve, go to www.pwr-tools.com and download their Engineering Power Tools.
The freeware can do this, or pay the $49 for the full version and lots more
features. For 3"x3"x.120" wall square steel tubing with rounded corners,
15.5' (186") long, ends simply supported, load concentrated at the center, I
calculate that a load of 1000 lbs would cause the center to sag 2.6" and the
maximum stress would be 38.9 ksi. Yield strength for structural steel is in
the 35-45 ksi range so 1000 lbs would just cause it to yield. If you want a
factor of 5 safety margin you could lift 200 lbs with each beam, with the
load concentrated at the center. The standard version can do all of that.
Using one of the advanced version features to allow fancier beam loadings,
if your load is concentrated at two points each 3.75' (45") from each end
with 500 lbs at each of the two lift points so the total is still 1000 lbs,
now the deflection at the center is 1.7" and the maximum stress is 18.8 ksi,
which is about half the yield strength. So about 1000 lbs at each point
(2000 lbs total) would just cause the beam to yield, and a factor of 5
safety margin would let you lift 400 lbs total - still less than half the
weight of your boat. Your idea of a truss beam would greatly stiffen things
up, but unfortunately pwr-tools doesn't do truss beams and my references are
at work so I can't estimate how much stiffer, sorry :-). Hope that helps.

-----
Regards,
Carl Ijames
"Steve B" wrote in message
. ..

I want to build an overhead "H" shaped frame for LIGHT lifting. The frame
is for between two containers that are 15'6" apart. They are reasonably
accurately oriented parallel and level their tops.

I was doing a cut schedule layout, and saw a couple of things.

Originally, I was going to put vertical posts coming down and resting on a
plate on concrete. Then I thought that I could span the whole thing with
one piece, and rest it on the top of the containers and make two span
supports.

My end goal is to have two parallel spans perpendicular to the containers,
10' apart so I can lift half my 16' aluminum boat with each span. I could
achieve that with just putting two pieces of 3" x 3" x .120" across there.
The lifting points would be outward from center, about three feet from the
container, so I would not be lifting the heaviest thing at the center of the
span. (One end of the boat would be heavier than the other. I want to be
able to lift the boat and pull the trailer out to work on it at home.)

I want one perpendicular center piece, forming a big H. The long legs will
be 15'6", and the short leg 10' long.

Am I okay to use this idea, and just rest them on the top of the container
on plates I shall make? Or should I put a support pole along the containers
for a total of four support poles?

Should I make any "A" shaped reinforcement along the top of the two spreader
bars to give the center a little more strength? Then put another short
piece between the apexes of the vees to give it more strength?

Does anyone know how to calculate what the lifting strength of the 15'6"
beams would be?

I mainly want this to lift items on to and off my welding table, and to turn
pieces of fencing and gates during manufacture. Total weight, 200# max.
The boat, I would say, with motor, weighs 1,000# max, but the lifting points
would be outboard of center, I'd say the boat is 6-8' wide, so I would have
about 8' divided by two on either side of the boat, putting more strain on
the beam closer to center, not in the middle.

I do know this is for light lifting. I have a lot of experience in rigging,
and know how to do a lot of tricks in lifting.

I personally think that if I put a vee shaped piece on top of each beam,
about 8' wide, and 140 degrees at the apex, that would give me more
strength, and help support the middle, hence less sag and more safety.

The end product would look like a house from top plate up, except for side
wall plates. End plates, vee truss, connector, and peak beam.

Input?

Steve

http://www.flickr.com/photos/deserttraveler/

Here's a pencil drawing. It is all 3 x 3. The house like frame would give
it rigidity, and take some of the bending out of the cross pieces by
transferring it into compression at the peak. The peak will keep the thing
from torquing. The D rings will be the lifting points for the boat, but
other than that, there will be three roller D rings on the main 20' beam.
Where it sticks 5' out from the crossmembers, it will be supported by chain
to the peak.

The biggest thing I will lift with this are an aluminum boat with a 40 hp
motor @ the four points, about 3' in from the sides where they rest on top
of the plate on top of the container. After that, the maximum I would lift
would probably never reach 500#, but it would be used for items up to 150#
during construction of the item on the welding table. By your estimation,
Carl, it should be safe for that.

What do you think of this design? I know I could overload this, but I know
the weight I would be lifting, and I'm thinking 300# would be a big lift.
This is not the design that I would like to do, but a compromise. I want to
keep the open space without losing it to supports. I was an Offshore
Petroleum Institute certified rigger, various union OSHA certified courses,
and a crane operator. I know this will do what I want it to do, be an extra
man for me when I need to flip a piece of fence, or lift something up on the
table to work on or weld. I'm just trying to get an idea on the max load,
and then I'll divide by 4 or 5 and live with that.

Steve

The simple beams were within a factor of 2 or 3 of just enough, so my gut
says your truss will be plenty - I just can't back it up with numbers
without looking up some stuff. If I get a chance tomorrow at work I'll try.

-----
Regards,
Carl Ijames

"Steve B" wrote in message
. ..

http://www.flickr.com/photos/deserttraveler/

Here's a pencil drawing. It is all 3 x 3. The house like frame would give
it rigidity, and take some of the bending out of the cross pieces by
transferring it into compression at the peak. The peak will keep the thing
from torquing. The D rings will be the lifting points for the boat, but
other than that, there will be three roller D rings on the main 20' beam.
Where it sticks 5' out from the crossmembers, it will be supported by chain
to the peak.

The biggest thing I will lift with this are an aluminum boat with a 40 hp
motor @ the four points, about 3' in from the sides where they rest on top
of the plate on top of the container. After that, the maximum I would lift
would probably never reach 500#, but it would be used for items up to 150#
during construction of the item on the welding table. By your estimation,
Carl, it should be safe for that.

What do you think of this design? I know I could overload this, but I know
the weight I would be lifting, and I'm thinking 300# would be a big lift.
This is not the design that I would like to do, but a compromise. I want to
keep the open space without losing it to supports. I was an Offshore
Petroleum Institute certified rigger, various union OSHA certified courses,
and a crane operator. I know this will do what I want it to do, be an extra
man for me when I need to flip a piece of fence, or lift something up on the
table to work on or weld. I'm just trying to get an idea on the max load,
and then I'll divide by 4 or 5 and live with that.

Steve

"Carl Ijames" wrote
The simple beams were within a factor of 2 or 3 of just enough, so
my gut says your truss will be plenty - I just can't back it up with
numbers without looking up some stuff. If I get a chance tomorrow
at work I'll try.

-----
Regards,
Carl Ijames

"Steve B" wrote in message
. ..

http://www.flickr.com/photos/deserttraveler/

Here's a pencil drawing. It is all 3 x 3. The house like frame
would give

Steve,

Based on Carl's previous numbers I would tend to agree that it should
be sufficient. I would personally move the angles out until they are
over the edges of the containers (opening up the 140 deg apex and
leaving the height about the same). This will deliver the load from
the center I beam to the containers directly instead of just
stiffening the middle of the cross bars. Leaving the "boat hooks" mid
span on your cross bars should not be a problem. I am sure you would
think of it, but I would also weld 4 stops to the cross bars so they
can not slide across the roofs of the containers.

--
Stephen B.
Remove the first Spam only to e-mail directly

"Stephen B." wrote

Based on Carl's previous numbers I would tend to agree that it should be
sufficient.

My gut says it's good to go, but approaches strain at 350# on center beam,
and redlines at 500#. I have a 497# atv that will be a test lift, and
deflection noted. Perhaps even put in vertical temporary stiffener whenever
lifting more than 350#.

I would personally move the angles out until they are
over the edges of the containers (opening up the 140 deg apex and leaving
the height about the same).

It's all 3 x 3. The reason I brought them in is that is the point of
attachment to lift the boat, the biggest thing I'll lift.

This will deliver the load from
the center I beam to the containers directly instead of just stiffening
the middle of the cross bars. Leaving the "boat hooks" mid span on your
cross bars should not be a problem. I am sure you would think of it, but I
would also weld 4 stops to the cross bars so they can not slide across the
roofs of the containers.

Better than that, four base plate structures will be welded to the tops of
the containers to receive the ends. NO CHANCE OF MOVEMENT ONCE IT IS WELDED
OUT.


--
Stephen B.

Thank you for your comments.

Steve

"Carl Ijames" wrote in message
...
The simple beams were within a factor of 2 or 3 of just enough, so my gut
says your truss will be plenty - I just can't back it up with numbers
without looking up some stuff. If I get a chance tomorrow at work I'll
try.

-----
Regards,
Carl Ijames


Appreciate it. Now's the time to do the numbers. This gives me a clear
span under the lift, converts downward bending to compression, and just
stiffens and strengthens in several ways.

Steve

"Steve B" wrote in message
. ..

Appreciate it. Now's the time to do the numbers. This gives me a
clear span under the lift, converts downward bending to compression,
and just stiffens and strengthens in several ways.

Steve

Have you considered wood?
http://www.awc.org/technical/spantables/tutorial.html
In Fig 3 a 2x12x16' falls within the range you are looking for.
Pressure treated syp (Southern Yellow Pine) is nearly as strong as oak
and doesn't need protection from the weather. You do have to brace it
to stop twisting but the H center bar helps. Pick two without knots on
one side and make it the bottom.

jsw

"Jim Wilkins" wrote


Have you considered wood?
http://www.awc.org/technical/spantables/tutorial.html
In Fig 3 a 2x12x16' falls within the range you are looking for. Pressure
treated syp (Southern Yellow Pine) is nearly as strong as oak and doesn't
need protection from the weather. You do have to brace it to stop twisting
but the H center bar helps. Pick two without knots on one side and make it
the bottom.

jsw

No, I have not. I have this steel in stock, and the means of working with
it. That's the main reason, plus, I like to just paint it good, and not
fool with it for a long time. Wood is good, but for this, I think I trust
steel a bit more.

Steve

On 23/02/2012 22:32, Steve B wrote:
"Jim wrote


Have you considered wood?
http://www.awc.org/technical/spantables/tutorial.html
In Fig 3 a 2x12x16' falls within the range you are looking for. Pressure
treated syp (Southern Yellow Pine) is nearly as strong as oak and doesn't
need protection from the weather. You do have to brace it to stop twisting
but the H center bar helps. Pick two without knots on one side and make it
the bottom.

jsw

No, I have not. I have this steel in stock, and the means of working with
it. That's the main reason, plus, I like to just paint it good, and not
fool with it for a long time. Wood is good, but for this, I think I trust
steel a bit more.

Steve


Can't disagree, but in the olden days they used timber rather than steel
for mining for good reasons. Firstly, wood gives early warning by making
noises before it lets go, and secondly it will usually tolerate much
larger deflections before collapsing. But, since you have the steel, go
with that but back up your instincts with some basic calcs. In
particular, watch out for buckling (which is what tends to get missed
when bridges collapse while they are being built).

Ok, I got out my old book and did a little trig :-). For a simple
triangular truss with two equal sides and a horizontal crossbar at the base,
the load needs to be applied at the joint at the apex of the angled risers.
That places the angled risers in pure compression and the horizontal bar in
pure tension. You can drop a vertical bar from the apex to the center of
the horizontal beam and apply the load at the base of that, if you want,
just make sure it can support the entire load in tension. If you use two
lift points part way up each angled riser, that adds bending stress and
greatly weakens the assembly. Here are a few equations for you:

length of horizontal beam: L
angle of base of risers with horizontal beam: T
load applied to apex: W

length of each angled riser = L / (2 * cos T)
height of apex = (L * tan T) / 2
compressive force on each angled riser = W / (2 * sin T)
tensile force on horizontal beam = W * cos T

So, if L=15.5'=186", W=1000 lbs, and T=30 degrees:
length of each angled riser = 186 / (2 * cos 30) = 107.4"
height of apex = (186 * tan 30) / 2 = 53.7"
compressive force on each angle riser = 1000 / (2 * sin 30) = 1000 lbs
tensile force on horizontal beam = 1000 * cos 30 = 866 lbs

Using eng. pwr tools, one estimate of the compressive load a slender beam
like 3" square tube 107.4" long can support 8900 lbs with a safety margin of
5x. The cross sectional area of 3" square .120 wall tube is 1.34 in^2 and
if the tensile strength is 35,000 lb/in^2 the horizontal beam can handle
35,000 lb/in^2 * 1.34 in^2 = 47,000 lbs, or 9,000 lbs with a factor of 5
margin. Gosh, one truss like this can handle 9,000 lbs (if you can keep it
upright :-)). Anyway, play with the formulas to find an angle you like.

-----
Regards,
Carl Ijames
"Steve B" wrote in message
. ..


"Carl Ijames" wrote in message
...
The simple beams were within a factor of 2 or 3 of just enough, so my gut
says your truss will be plenty - I just can't back it up with numbers
without looking up some stuff. If I get a chance tomorrow at work I'll
try.

-----
Regards,
Carl Ijames


Appreciate it. Now's the time to do the numbers. This gives me a clear
span under the lift, converts downward bending to compression, and just
stiffens and strengthens in several ways.

Steve

I think with all the calcs, and looking at it, that the way I posted it on
flickr will be a good way to build it. Plus, I can set the horizontals,
then lift the premade vees with peak attached as one piece, and weld it all
together in the air. I have some masonry screw jacks that I will support
everything with to take away any sagging from the heat.

I'm good go to with this.

Steve


"Carl Ijames" wrote in message
...
Ok, I got out my old book and did a little trig :-). For a simple
triangular truss with two equal sides and a horizontal crossbar at the
base, the load needs to be applied at the joint at the apex of the angled
risers. That places the angled risers in pure compression and the
horizontal bar in pure tension. You can drop a vertical bar from the apex
to the center of the horizontal beam and apply the load at the base of
that, if you want, just make sure it can support the entire load in
tension. If you use two lift points part way up each angled riser, that
adds bending stress and greatly weakens the assembly. Here are a few
equations for you:

length of horizontal beam: L
angle of base of risers with horizontal beam: T
load applied to apex: W

length of each angled riser = L / (2 * cos T)
height of apex = (L * tan T) / 2
compressive force on each angled riser = W / (2 * sin T)
tensile force on horizontal beam = W * cos T

So, if L=15.5'=186", W=1000 lbs, and T=30 degrees:
length of each angled riser = 186 / (2 * cos 30) = 107.4"
height of apex = (186 * tan 30) / 2 = 53.7"
compressive force on each angle riser = 1000 / (2 * sin 30) = 1000 lbs
tensile force on horizontal beam = 1000 * cos 30 = 866 lbs

Using eng. pwr tools, one estimate of the compressive load a slender beam
like 3" square tube 107.4" long can support 8900 lbs with a safety margin
of 5x. The cross sectional area of 3" square .120 wall tube is 1.34 in^2
and if the tensile strength is 35,000 lb/in^2 the horizontal beam can
handle 35,000 lb/in^2 * 1.34 in^2 = 47,000 lbs, or 9,000 lbs with a factor
of 5 margin. Gosh, one truss like this can handle 9,000 lbs (if you can
keep it upright :-)). Anyway, play with the formulas to find an angle you
like.

-----
Regards,
Carl Ijames
"Steve B" wrote in message
. ..


"Carl Ijames" wrote in message
...
The simple beams were within a factor of 2 or 3 of just enough, so my gut
says your truss will be plenty - I just can't back it up with numbers
without looking up some stuff. If I get a chance tomorrow at work I'll
try.

-----
Regards,
Carl Ijames


Appreciate it. Now's the time to do the numbers. This gives me a clear
span under the lift, converts downward bending to compression, and just
stiffens and strengthens in several ways.

Steve

"Steve B" wrote

"Stephen B." wrote

Based on Carl's previous numbers I would tend to agree that it
should be sufficient.

My gut says it's good to go, but approaches strain at 350# on center
beam, and redlines at 500#. I have a 497# atv that will be a test
lift, and deflection noted. Perhaps even put in vertical temporary
stiffener whenever lifting more than 350#.

I would personally move the angles out until they are
over the edges of the containers (opening up the 140 deg apex and
leaving the height about the same).

It's all 3 x 3. The reason I brought them in is that is the point
of attachment to lift the boat, the biggest thing I'll lift.

I understand your resoning, but you are actualy not helping yourself
much. You are proposing to attatch the stress load of the boat on the
cross bar at the point that the beam stifness changes. The load would
be slightly higer where you are not stifening (added weight of the
stifening). If you look at
http://www.classictruss.com/roof_truss_facts.asp their is a reson all
the trusses shown have both the uper and lower span coming to the
bearing point . For ease of manufacturing, you may want to consider a
Modified "2x4 roof truss". make to laders with only a couple of short
cross brases (at load locations). or if you have some small stell,
make thboth trusses like one side of
http://www.garrettsbridges.com/wp-co...ss-bridge5.jpg
heavy outer beams and thin stock stringers between them.

This will deliver the load from
the center I beam to the containers directly instead of just
stiffening the middle of the cross bars. Leaving the "boat hooks"
mid span on your cross bars should not be a problem. I am sure you
would think of it, but I would also weld 4 stops to the cross bars
so they can not slide across the roofs of the containers.

Better than that, four base plate structures will be welded to the
tops of the containers to receive the ends. NO CHANCE OF MOVEMENT
ONCE IT IS WELDED OUT.


Are you basically welding everything so the two containers are
indirectly welded together or are you trapping the ends so they can
not move much? If the containers are not on good foundations, I would
lean towards the later.



--
Stephen B.

Thank you for your comments.

Steve

Your welcome. I am sure you will be fine whatever way you do it.

--
Stephen B.

"Stephen B." wrote

Are you basically welding everything so the two containers are indirectly
welded together or are you trapping the ends so they can not move much? If
the containers are not on good foundations, I would lean towards the
later.



--
Stephen B.

I had that thought after posting. This is why it is to discuss a plan
before executing it.

Steve

"Stephen B." wrote in

I understand your resoning, but you are actualy not helping yourself much.
You are proposing to attatch the stress load of the boat on the cross bar
at the point that the beam stifness changes. The load would be slightly
higer where you are not stifening (added weight of the stifening). If you
look at http://www.classictruss.com/roof_truss_facts.asp their is a reson
all the trusses shown have both the uper and lower span coming to the
bearing point . For ease of manufacturing, you may want to consider a
Modified "2x4 roof truss". make to laders with only a couple of short
cross brases (at load locations). or if you have some small stell, make
thboth trusses like one side of
http://www.garrettsbridges.com/wp-co...ss-bridge5.jpg
heavy outer beams and thin stock stringers between them.

This will deliver the load from
the center I beam to the containers directly instead of just stiffening
the middle of the cross bars. Leaving the "boat hooks" mid span on your
cross bars should not be a problem. I am sure you would think of it, but
I would also weld 4 stops to the cross bars so they can not slide across
the roofs of the containers.


This will be used to lift items that are in the less than 250# range 99% of
the time. For the boat, it will be only to lift it long enough to get some
cribbing under it, and it will be lifted about two inches off the trailer.
I have no reservations that this will hold the front (empty) end of a 16'
aluminum boat.

Steve