I've been playing around awhile with calculators on the web and whatnot,
but since I don't know what I'm doing, what is the maximum (failure) load
that I can put on the end of a 21 cantilevered piece of 2" standard square
structural tubing, 1/4" wall? How about to the point of permanent
deflection (unrecoverable bend) What is the safe working load that can be
applied? I'm trying to find out what the maximum I can go with for a C
press I'm thinking about making.
I'm sure I need to offer some more information, but like I said, this is
stuff I rarely to never delve into.

On Thu, 11 Aug 2005 03:38:18 GMT, "carl mciver"
wrote:

I've been playing around awhile with calculators on the web and whatnot,
but since I don't know what I'm doing, what is the maximum (failure) load
that I can put on the end of a 21 cantilevered piece of 2" standard square
structural tubing, 1/4" wall? How about to the point of permanent
deflection (unrecoverable bend) What is the safe working load that can be
applied? I'm trying to find out what the maximum I can go with for a C
press I'm thinking about making.
I'm sure I need to offer some more information, but like I said, this is
stuff I rarely to never delve into.

Others will know more about this than I, but here's what I figure
using formulae from Machinery's Handbook:

A load of 1302 lb on the end of your 21" cantilever would result in
deflection of 0.152 inches and max stress of 30,000 lb/in^2. I
used 29 million PSI as E, modulus of elasticity. I think 30,000
lb/in^2 stress is below the yield point for structural steel, and I
seem to recall that it's one figure that is used as rule-of-thumb
permissible stress (before safety margin) for structural steel.

What is "safe" depends on what you want to use for safety margin.

Load that would permanently bend it would depend some on the
particular piece of steel used, might be twice the load stated above.

Max stress will be at the constrained end of the cantilever -- so the
joint design there (weld, bolts, clamp, gussets or not, ???) will
play an important role.

Without going into alot of math and using the area for square tube with
90 degree ends I came up with a quick ball park figure of around 947
lbs. However, be advised that steel tube has radiused ends so your area
will be a little smaller. The other poster is right about max stress
being at the fixed point of the beam as a moment and shear diagram
would show you.

Also, you need a safety factor of at least 4 to 1 to work safely so
your acceptable load now at the end of the beam is 237lbs.

Thanks, Steve

In article KKzKe.4201$WD.3671
@newsread1.news.pas.earthlink.net,
says...
I've been playing around awhile with calculators on the web and whatnot,
but since I don't know what I'm doing, what is the maximum (failure) load
that I can put on the end of a 21 cantilevered piece of 2" standard square
structural tubing, 1/4" wall? How about to the point of permanent
deflection (unrecoverable bend) What is the safe working load that can be
applied? I'm trying to find out what the maximum I can go with for a C
press I'm thinking about making.
I'm sure I need to offer some more information, but like I said, this is
stuff I rarely to never delve into.



If you're talking about loads of more than a few hundred
pounds, you may be asking the wrong question. The design of
a C-frame press is almost always driven by deflection, and
the member that will contribute most to deflection is the
vertical column. The top and bottom of the C will be
subject to a moment that increases uniformly from the load
point to the attachment point. The vertical member must
carry this moment thru its entire length and will be bowed
considerably by this moment. The effect of this bow is
magnified by the length of the horizontal members (your
21").

Look at an arbor press or open sided punch press (or even a
heavy C-clamp) with this in mind and the reason for the
deep back column becomes obvious. It also points up the
reason that most heavy shop presses are H-frames, where the
vertical columns are in pure tension.

Ned Simmons

"Ned Simmons" wrote in message
...
SNIP|
| If you're talking about loads of more than a few hundred
| pounds, you may be asking the wrong question. The design of
| a C-frame press is almost always driven by deflection, and
| the member that will contribute most to deflection is the
| vertical column. The top and bottom of the C will be
| subject to a moment that increases uniformly from the load
| point to the attachment point. The vertical member must
| carry this moment thru its entire length and will be bowed
| considerably by this moment. The effect of this bow is
| magnified by the length of the horizontal members (your
| 21").
|
| Look at an arbor press or open sided punch press (or even a
| heavy C-clamp) with this in mind and the reason for the
| deep back column becomes obvious. It also points up the
| reason that most heavy shop presses are H-frames, where the
| vertical columns are in pure tension.
|
| Ned Simmons

The vertical column is 3" square tubing, 1/4" wall, so deflection there
isn't as much of an issue as the horizontal part there. The connection to
the 2" tubing is that the vertical tubing sort of wraps around a horizontal
piece of 2 1/2" tubing, plus gussets, and the 2" tubing is pinned into that
piece at different spots, and allowed to slide in and out to change the
throat. At higher loads the tubing will be retracted and the throat will be
shorter, so the answer is really not the maximum I can put on the press, but
what is the highest amount that I can work with when at the weakest point.
Does that make sense? As the load needed goes up, I reduce the throat which
reduces flex. The plan is to ballpark what the load maximums are for each
setting, which at the longest is 21" throat and every two inches it can be
pinned, to a minimum of about an inch, which is a throat of about 13". I
failed to clarify, now that I look at my drawing again (duh!) At a 21"
throat, the tubing will be "out" by about 10 inches, so that really changes
the numbers. The difference between extension and throat is the depth that
the tubing it slides into is part of the throat dimension. I'm not
considering the flex in the joint or the female tubing, since it's heavily
gusseted and makes for much more complex calculations.

The reason I'm doing it this way is that half the time I've needed a
press I couldn't get the part in a traditional H press (why I haven't a
clue,) and that made things a real PITA. This is sort of a combination of
possibilities, I guess, and of course takes up a little less room than an H
press, at least as far as width is concerned. I just wanted to get a better
idea of what it was capable of. It's a sort of uprated version of what
Grant Erwin's got on his site at http://www.tinyisland.com/PMarborPress.pdf
with an adjustable throat.

On Thu, 11 Aug 2005 19:15:30 GMT, "carl mciver"
wrote:


The vertical column is 3" square tubing, 1/4" wall, so deflection there
isn't as much of an issue as the horizontal part there. The connection to
the 2" tubing is that the vertical tubing sort of wraps around a horizontal
piece of 2 1/2" tubing, plus gussets, and the 2" tubing is pinned into that
piece at different spots, and allowed to slide in and out to change the
throat. At higher loads the tubing will be retracted and the throat will be
shorter, so the answer is really not the maximum I can put on the press, but
what is the highest amount that I can work with when at the weakest point.
Does that make sense? As the load needed goes up, I reduce the throat which
reduces flex. The plan is to ballpark what the load maximums are for each
setting, which at the longest is 21" throat and every two inches it can be
pinned, to a minimum of about an inch, which is a throat of about 13". I
failed to clarify, now that I look at my drawing again (duh!) At a 21"
throat, the tubing will be "out" by about 10 inches, so that really changes
the numbers. The difference between extension and throat is the depth that
the tubing it slides into is part of the throat dimension. I'm not
considering the flex in the joint or the female tubing, since it's heavily
gusseted and makes for much more complex calculations.

The reason I'm doing it this way is that half the time I've needed a
press I couldn't get the part in a traditional H press (why I haven't a
clue,) and that made things a real PITA. This is sort of a combination of
possibilities, I guess, and of course takes up a little less room than an H
press, at least as far as width is concerned. I just wanted to get a better
idea of what it was capable of. It's a sort of uprated version of what
Grant Erwin's got on his site at http://www.tinyisland.com/PMarborPress.pdf
with an adjustable throat.

I've got a real good idea of what you're doing. In fact I've got a
portable press I made along the same lines. However I think you're
underestimating what it'll take. I made my press frame from two pieces
of 8" channel welding up into a tube. Then my arms have 3" square tube
sockets that take 2 1/2" attachments. The arms are very heavily
gusseted. I've only got about 13" overhang to the center of the jack
when setup. I can get a good 1/2" of flex in the system with a weak
jack that I have in it right now. The jacks supposed to be a 20 ton
but it's leaking back so badly that I can't lift the front of a diesel
truck with it right now so figure I'm not able to get more than 5-10
tons on it.

Wayne Cook
Shamrock, TX
http://members.dslextreme.com/users/waynecook/index.htm

"Wayne Cook" wrote in message
...
| On Thu, 11 Aug 2005 19:15:30 GMT, "carl mciver"
| wrote:
|
|
| The vertical column is 3" square tubing, 1/4" wall, so deflection
there
| isn't as much of an issue as the horizontal part there. The connection
to
| the 2" tubing is that the vertical tubing sort of wraps around a
horizontal
| piece of 2 1/2" tubing, plus gussets, and the 2" tubing is pinned into
that
| piece at different spots, and allowed to slide in and out to change the
| throat. At higher loads the tubing will be retracted and the throat will
be
| shorter, so the answer is really not the maximum I can put on the press,
but
| what is the highest amount that I can work with when at the weakest
point.
| Does that make sense? As the load needed goes up, I reduce the throat
which
| reduces flex. The plan is to ballpark what the load maximums are for
each
| setting, which at the longest is 21" throat and every two inches it can
be
| pinned, to a minimum of about an inch, which is a throat of about 13". I
| failed to clarify, now that I look at my drawing again (duh!) At a 21"
| throat, the tubing will be "out" by about 10 inches, so that really
changes
| the numbers. The difference between extension and throat is the depth
that
| the tubing it slides into is part of the throat dimension. I'm not
| considering the flex in the joint or the female tubing, since it's
heavily
| gusseted and makes for much more complex calculations.
|
| The reason I'm doing it this way is that half the time I've needed a
| press I couldn't get the part in a traditional H press (why I haven't a
| clue,) and that made things a real PITA. This is sort of a combination
of
| possibilities, I guess, and of course takes up a little less room than an
H
| press, at least as far as width is concerned. I just wanted to get a
better
| idea of what it was capable of. It's a sort of uprated version of what
| Grant Erwin's got on his site at
http://www.tinyisland.com/PMarborPress.pdf
| with an adjustable throat.
|
| I've got a real good idea of what you're doing. In fact I've got a
| portable press I made along the same lines. However I think you're
| underestimating what it'll take. I made my press frame from two pieces
| of 8" channel welding up into a tube. Then my arms have 3" square tube
| sockets that take 2 1/2" attachments. The arms are very heavily
| gusseted. I've only got about 13" overhang to the center of the jack
| when setup. I can get a good 1/2" of flex in the system with a weak
| jack that I have in it right now. The jacks supposed to be a 20 ton
| but it's leaking back so badly that I can't lift the front of a diesel
| truck with it right now so figure I'm not able to get more than 5-10
| tons on it.
|
| Wayne Cook
| Shamrock, TX
| http://members.dslextreme.com/users/waynecook/index.htm

Wayne, I was poking around your site, seeing if there was either a
direct picture of it, or just it in the background of something, but nothing
turned up. Got some pics about!

In article mtNKe.4373$WD.1860
@newsread1.news.pas.earthlink.net,
says...
"Ned Simmons" wrote in message
...
SNIP|
| If you're talking about loads of more than a few hundred
| pounds, you may be asking the wrong question. The design of
| a C-frame press is almost always driven by deflection, and
| the member that will contribute most to deflection is the
| vertical column. The top and bottom of the C will be
| subject to a moment that increases uniformly from the load
| point to the attachment point. The vertical member must
| carry this moment thru its entire length and will be bowed
| considerably by this moment. The effect of this bow is
| magnified by the length of the horizontal members (your
| 21").
|
| Look at an arbor press or open sided punch press (or even a
| heavy C-clamp) with this in mind and the reason for the
| deep back column becomes obvious. It also points up the
| reason that most heavy shop presses are H-frames, where the
| vertical columns are in pure tension.
|
| Ned Simmons

The vertical column is 3" square tubing, 1/4" wall, so deflection there
isn't as much of an issue as the horizontal part there.

I think you'll find that even though the 3" tube is approx
4x as stiff as the the 2" tube, it'll contribute more to
the deflection than the 2" tubes, unless it's very short. I
guess all I'm saying is that effort put into stiffening the
vertical member will have a bigger payoff than stiffening
the arms.

The connection to
the 2" tubing is that the vertical tubing sort of wraps around a horizontal
piece of 2 1/2" tubing, plus gussets, and the 2" tubing is pinned into that
piece at different spots, and allowed to slide in and out to change the
throat. At higher loads the tubing will be retracted and the throat will be
shorter, so the answer is really not the maximum I can put on the press, but
what is the highest amount that I can work with when at the weakest point.
Does that make sense?

Don's answer looked good, except I'd reduce the stress in
the steel to 22000 psi, which is what the AISC prescribes
as design stress for A36 plain vanilla structural steel, so
around 800# at 21".

Another thing that may not be obvious is that the
deflection of the arms by themselves is a function of the
cube of the distance from the verical member to the load.
The deflection at the load point caused by the bowing of
the vertical member will vary as the square of the distance
to the load. This is because the bending moment in the arms
increases uniformly as move towrds the attachment point.
The bending moment in the vertical member is constant, and
equal to the max in the arms, over its entire length.

Ned Simmons

On Thu, 11 Aug 2005 23:24:21 GMT, "carl mciver"
wrote:


|
| I've got a real good idea of what you're doing. In fact I've got a
| portable press I made along the same lines. However I think you're
| underestimating what it'll take. I made my press frame from two pieces
| of 8" channel welding up into a tube. Then my arms have 3" square tube
| sockets that take 2 1/2" attachments. The arms are very heavily
| gusseted. I've only got about 13" overhang to the center of the jack
| when setup. I can get a good 1/2" of flex in the system with a weak
| jack that I have in it right now. The jacks supposed to be a 20 ton
| but it's leaking back so badly that I can't lift the front of a diesel
| truck with it right now so figure I'm not able to get more than 5-10
| tons on it.
|
| Wayne Cook
| Shamrock, TX
| http://members.dslextreme.com/users/waynecook/index.htm

Wayne, I was poking around your site, seeing if there was either a
direct picture of it, or just it in the background of something, but nothing
turned up. Got some pics about!

I'll see what I can do. It's in pieces right now stacked near my
drill presses. But the pics of the drill presses are old enough that
it's not in there. My big problem right now is time. I've got a big
stainless fertilizer spreader in the shop that's been giving me a hard
time. It's been there way to long but between interruptions and
equipment break downs I'm having trouble getting it out.

Wayne Cook
Shamrock, TX
http://members.dslextreme.com/users/waynecook/index.htm

"Ned Simmons" wrote in message
...
| In article mtNKe.4373$WD.1860
| @newsread1.news.pas.earthlink.net,
| says...
| "Ned Simmons" wrote in message
| ...
| SNIP|
|
| Don's answer looked good, except I'd reduce the stress in
| the steel to 22000 psi, which is what the AISC prescribes
| as design stress for A36 plain vanilla structural steel, so
| around 800# at 21".

Thank you very much for a well thought out response.
I was doing some more thinking about load paths and realized that I made
another error. The tube I brought up is, for the most part, not in the load
path, other than providing a leverage point out at the end. I plan on
reinforcing this part on the top and bottom with straps top and bottom on
the exposed part.
The load path is as follows: At the top of the vertical part of the C,
resting on the slip sleeve for the aforementioned tube, will be a hydraulic
jack. The jack pushes up on another 2" tube reinforced with a 3/16" or so
strap on the bottom and top, and/or with a doubled tube even, and to provide
a surface for the jack top to bear on. Near the other end is a pair of
holes that a vertical link connects to from it the tube first discussed. At
the very end it's pinned to a vertical tube, full of holes to make it
adjustable up and down. So the jack pushes the lever up, levering it
against the link and pushing the other end down to do the business needed.
The leverage factor is from 1:1 up to 7:1 depending on how far you've got
the tubes positioned, and which pair holes the link is using. At the ends
of the lever there will also be side plates, because the forces in this
short area will be pretty high, considering the leverage.
Should I just post my drawing and make it that much easier to explain, I
feel like I'm making everyone try hard to imagine it as I describe it?

In article KmWKe.4294$Wi6.1087
@newsread2.news.pas.earthlink.net,
says...

"Ned Simmons" wrote in message
...
| In article mtNKe.4373$WD.1860
| @newsread1.news.pas.earthlink.net,
| says...
| "Ned Simmons" wrote in message
| ...
| SNIP|
|
| Don's answer looked good, except I'd reduce the stress in
| the steel to 22000 psi, which is what the AISC prescribes
| as design stress for A36 plain vanilla structural steel, so
| around 800# at 21".

Thank you very much for a well thought out response.
I was doing some more thinking about load paths and realized that I made
another error. The tube I brought up is, for the most part, not in the load
path, other than providing a leverage point out at the end. I plan on
reinforcing this part on the top and bottom with straps top and bottom on
the exposed part.
The load path is as follows: At the top of the vertical part of the C,
resting on the slip sleeve for the aforementioned tube, will be a hydraulic
jack. The jack pushes up on another 2" tube reinforced with a 3/16" or so
strap on the bottom and top, and/or with a doubled tube even, and to provide
a surface for the jack top to bear on. Near the other end is a pair of
holes that a vertical link connects to from it the tube first discussed. At
the very end it's pinned to a vertical tube, full of holes to make it
adjustable up and down. So the jack pushes the lever up, levering it
against the link and pushing the other end down to do the business needed.
The leverage factor is from 1:1 up to 7:1 depending on how far you've got
the tubes positioned, and which pair holes the link is using. At the ends
of the lever there will also be side plates, because the forces in this
short area will be pretty high, considering the leverage.
Should I just post my drawing and make it that much easier to explain, I
feel like I'm making everyone try hard to imagine it as I describe it?


A picture would be helpful. I've formed a picture in my
head of your press that may not look much like what you're
imagining.

Ned Simmons

"Ned Simmons" wrote in message
...
SNIP|
| A picture would be helpful. I've formed a picture in my
| head of your press that may not look much like what you're
| imagining.
|
| Ned Simmons
|

It was about time I did that!
They are http://metalworking.com/DropBox/PressDsn.jpg and
http://metalworking.com/DropBox/PressDsn.txt
The text didn't come out as well as I would have liked, but it's the
idea that's most important.

In article yrfLe.5231$WD.2303
@newsread1.news.pas.earthlink.net,
says...

"Ned Simmons" wrote in message
...
SNIP|
| A picture would be helpful. I've formed a picture in my
| head of your press that may not look much like what you're
| imagining.
|
| Ned Simmons
|

It was about time I did that!
They are http://metalworking.com/DropBox/PressDsn.jpg and
http://metalworking.com/DropBox/PressDsn.txt
The text didn't come out as well as I would have liked, but it's the
idea that's most important.


I was wondering at first why you weren't just using the
jack's ram directly, but I can see a few advantages to your
design, the most obvious being flexibility in mounting
tooling.

The first thing I would suggest is to replace the single
tube with gusset that you're using as the column with a
pair of tubes spaced apart under the horizontal sleeve.
This'll make a huge difference in the stiffness and
strength of the column. (I hesitate to call it a column
because columns are normally thought of as carrying
compressive loads, while this member, even though vertical,
is subject to bending loads that more resemble a beam.) To
really stiffen it up you could add a web (or triangulation)
between the two tubes, at which point you've got something
that resembles an I-beam with tubular flanges (or a bar
truss, in the case of triangulation.)

Another thing that occurs to me is the possibility of a
lever that you can actuate manually in place of the jack.
Sometimes the feel of a manual press is preferably to
having lots of force available.

Ned Simmons

"Ned Simmons" wrote in message
...
| It was about time I did that!
| They are http://metalworking.com/DropBox/PressDsn.jpg and
| http://metalworking.com/DropBox/PressDsn.txt
| The text didn't come out as well as I would have liked, but it's the
| idea that's most important.
|
|
| I was wondering at first why you weren't just using the
| jack's ram directly, but I can see a few advantages to your
| design, the most obvious being flexibility in mounting
| tooling.

That's the plan. This can do the job of a much smaller press, even an
arbor press, as well as something much heavier duty, all with the same tool.
I like the versatility and real estate saved in my garage. Being able to
change the press tonnage from nothing to incredible easily appeals to me as
well. I can use a one ton jack just as well as I can a twenty ton, and they
just sit in same place since they're all roughly the same height.

| The first thing I would suggest is to replace the single
| tube with gusset that you're using as the column with a
| pair of tubes spaced apart under the horizontal sleeve.
| This'll make a huge difference in the stiffness and
| strength of the column. (I hesitate to call it a column
| because columns are normally thought of as carrying
| compressive loads, while this member, even though vertical,
| is subject to bending loads that more resemble a beam.) To
| really stiffen it up you could add a web (or triangulation)
| between the two tubes, at which point you've got something
| that resembles an I-beam with tubular flanges (or a bar
| truss, in the case of triangulation.)

Ah, excellent idea. Would the same be gained by just welding two tubes
to each other? The inner tube would be in tension under load, while the
outer tube would be in compression. I just had the notion that I could fill
the outside, "unused" tube with concrete, which resists compresssion (and
buckling the walls of the tube,) but I'll have to cap the ends off, of
course. Then again, one or two small I beams or channel between them sounds
pretty strong too, with the outer tube full of concrete would be good.
Resists twisting really well, too. Whaddya think?
Gusseting the horizontal tube would get interesting, of course, but most
of that load just passes around it, rather than the whole thing being a
cantilever beam. There's a hard to read note about the column "wrapping
around" that tube, which passes the load around it nicely.

When I first starting thinking about this, before I was aware of the PM
design, I had a much simpler design using an I beam as the column, but I was
concerned about it twisting, so was kinda stuck. You've helped me work that
out.

| Another thing that occurs to me is the possibility of a
| lever that you can actuate manually in place of the jack.
| Sometimes the feel of a manual press is preferably to
| having lots of force available.

That's one of those details that was so easy to implement, I just noted
it in text, and the text pretty much washed out in the scan. With a double
tube lever, I'd just weld on a couple pieces of tubes to the side of the top
one and slip in a piece of pipe to suit. This way it's just as easy to use
the press in manual mode or when necessary, just reach over and start
pumping the jack, since the jack isn't attached to the upper lever. There's
many times I suspect that the jack's job is over, and the rest of the
operation requires less pressure, so all you have to do is just reach up and
pull.

|
| Ned Simmons

Thanks for sticking with me this far through it! Your input has been
invaluable.

In article _1ALe.5598$WD.5081
@newsread1.news.pas.earthlink.net,
says...
"Ned Simmons" wrote in message
...


| The first thing I would suggest is to replace the single
| tube with gusset that you're using as the column with a
| pair of tubes spaced apart under the horizontal sleeve.
| This'll make a huge difference in the stiffness and
| strength of the column. (I hesitate to call it a column
| because columns are normally thought of as carrying
| compressive loads, while this member, even though vertical,
| is subject to bending loads that more resemble a beam.) To
| really stiffen it up you could add a web (or triangulation)
| between the two tubes, at which point you've got something
| that resembles an I-beam with tubular flanges (or a bar
| truss, in the case of triangulation.)

Ah, excellent idea. Would the same be gained by just welding two tubes
to each other?

I figure this would be about 4.5X as stiff as the single
tube. If you were to separate the two tubes with a web of
1/2x2 flat bar it would be 12.6X as stiff.

The inner tube would be in tension under load, while the
outer tube would be in compression.

The farther you separate the tubes, while restraining them
from shifting relative to one another, the closer you'll
get to this ideal. In an idealized I-beam one flange is in
tension, the other in compression, while the web is in
shear as it resists the tendency for the flanges to slip
relative to one another.

I just had the notion that I could fill
the outside, "unused" tube with concrete, which resists compresssion (and
buckling the walls of the tube,) but I'll have to cap the ends off, of
course.

Unless you prestress the tubes as the concrete cures, I
don't think you'll see any benefit. And even if you got it
to work, I doubt it would make enough difference to make it
worth the trouble.

Then again, one or two small I beams or channel between
them sounds
pretty strong too, with the outer tube full of concrete would be good.
Resists twisting really well, too. Whaddya think?
Gusseting the horizontal tube would get interesting, of course, but most
of that load just passes around it, rather than the whole thing being a
cantilever beam. There's a hard to read note about the column "wrapping
around" that tube, which passes the load around it nicely.

I'm afraid I'm not following this. Are you saying that the
horizontal tube is not carrying the force being applied by
the press ram? The situation is not as simple as if the
jack were at the end of the arm and acting directly, but
the horizontal tube is still carrying a considerable load.



Thanks for sticking with me this far through it! Your input has been
invaluable.


My pleasure. It's an interesting idea.

Ned Simmons

"carl mciver" wrote in message
nk.net...
"Ned Simmons" wrote in message
...
| It was about time I did that!
| They are http://metalworking.com/DropBox/PressDsn.jpg and
| http://metalworking.com/DropBox/PressDsn.txt
| The text didn't come out as well as I would have liked, but
it's the
| idea that's most important.
|
|
| I was wondering at first why you weren't just using the
| jack's ram directly, but I can see a few advantages to your
| design, the most obvious being flexibility in mounting
| tooling.

That's the plan. This can do the job of a much smaller press,
even an
arbor press, as well as something much heavier duty, all with the
same tool.
I like the versatility and real estate saved in my garage. Being
able to
change the press tonnage from nothing to incredible easily appeals
to me as
well. I can use a one ton jack just as well as I can a twenty ton,
and they
just sit in same place since they're all roughly the same height.

| The first thing I would suggest is to replace the single
| tube with gusset that you're using as the column with a
| pair of tubes spaced apart under the horizontal sleeve.
| This'll make a huge difference in the stiffness and
| strength of the column. (I hesitate to call it a column
| because columns are normally thought of as carrying
| compressive loads, while this member, even though vertical,
| is subject to bending loads that more resemble a beam.) To
| really stiffen it up you could add a web (or triangulation)
| between the two tubes, at which point you've got something
| that resembles an I-beam with tubular flanges (or a bar
| truss, in the case of triangulation.)

Ah, excellent idea. Would the same be gained by just welding
two tubes
to each other? The inner tube would be in tension under load, while
the
outer tube would be in compression. I just had the notion that I
could fill
the outside, "unused" tube with concrete, which resists compresssion
(and
buckling the walls of the tube,) but I'll have to cap the ends off,
of
course. Then again, one or two small I beams or channel between
them sounds
pretty strong too, with the outer tube full of concrete would be
good.
Resists twisting really well, too. Whaddya think?
Gusseting the horizontal tube would get interesting, of course,
but most
of that load just passes around it, rather than the whole thing
being a
cantilever beam. There's a hard to read note about the column
"wrapping
around" that tube, which passes the load around it nicely.

When I first starting thinking about this, before I was aware of
the PM
design, I had a much simpler design using an I beam as the column,
but I was
concerned about it twisting, so was kinda stuck. You've helped me
work that
out.

| Another thing that occurs to me is the possibility of a
| lever that you can actuate manually in place of the jack.
| Sometimes the feel of a manual press is preferably to
| having lots of force available.

That's one of those details that was so easy to implement, I
just noted
it in text, and the text pretty much washed out in the scan. With a
double
tube lever, I'd just weld on a couple pieces of tubes to the side of
the top
one and slip in a piece of pipe to suit. This way it's just as easy
to use
the press in manual mode or when necessary, just reach over and
start
pumping the jack, since the jack isn't attached to the upper lever.
There's
many times I suspect that the jack's job is over, and the rest of
the
operation requires less pressure, so all you have to do is just
reach up and
pull.

|
| Ned Simmons

Thanks for sticking with me this far through it! Your input has
been
invaluable.

One problem I see is the jack might have to be on pivots if the ram is
going to move any appreciable distance. The pivoting arm isn't going
to stay parallel with the pad the jack is sitting on, and the contact
point along the pivoting arm will change too. I suspect the ram may
tend to bind in the socket, too.

I'd be tempted to make a wood or cardboard model of the linkage first

"Rick" wrote in message
k.net...

"carl mciver" wrote in message
nk.net...
"Ned Simmons" wrote in message
...
| It was about time I did that!
| They are http://metalworking.com/DropBox/PressDsn.jpg and
| http://metalworking.com/DropBox/PressDsn.txt
| The text didn't come out as well as I would have liked,
but
it's the
| idea that's most important.
|
|
| I was wondering at first why you weren't just using the
| jack's ram directly, but I can see a few advantages to your
| design, the most obvious being flexibility in mounting
| tooling.

That's the plan. This can do the job of a much smaller press,
even an
arbor press, as well as something much heavier duty, all with the
same tool.
I like the versatility and real estate saved in my garage. Being
able to
change the press tonnage from nothing to incredible easily appeals
to me as
well. I can use a one ton jack just as well as I can a twenty
ton,
and they
just sit in same place since they're all roughly the same height.

| The first thing I would suggest is to replace the single
| tube with gusset that you're using as the column with a
| pair of tubes spaced apart under the horizontal sleeve.
| This'll make a huge difference in the stiffness and
| strength of the column. (I hesitate to call it a column
| because columns are normally thought of as carrying
| compressive loads, while this member, even though vertical,
| is subject to bending loads that more resemble a beam.) To
| really stiffen it up you could add a web (or triangulation)
| between the two tubes, at which point you've got something
| that resembles an I-beam with tubular flanges (or a bar
| truss, in the case of triangulation.)

Ah, excellent idea. Would the same be gained by just welding
two tubes
to each other? The inner tube would be in tension under load,
while
the
outer tube would be in compression. I just had the notion that I
could fill
the outside, "unused" tube with concrete, which resists
compresssion
(and
buckling the walls of the tube,) but I'll have to cap the ends
off,
of
course. Then again, one or two small I beams or channel between
them sounds
pretty strong too, with the outer tube full of concrete would be
good.
Resists twisting really well, too. Whaddya think?
Gusseting the horizontal tube would get interesting, of
course,
but most
of that load just passes around it, rather than the whole thing
being a
cantilever beam. There's a hard to read note about the column
"wrapping
around" that tube, which passes the load around it nicely.

When I first starting thinking about this, before I was aware
of
the PM
design, I had a much simpler design using an I beam as the column,
but I was
concerned about it twisting, so was kinda stuck. You've helped me
work that
out.

| Another thing that occurs to me is the possibility of a
| lever that you can actuate manually in place of the jack.
| Sometimes the feel of a manual press is preferably to
| having lots of force available.

That's one of those details that was so easy to implement, I
just noted
it in text, and the text pretty much washed out in the scan. With
a
double
tube lever, I'd just weld on a couple pieces of tubes to the side
of
the top
one and slip in a piece of pipe to suit. This way it's just as
easy
to use
the press in manual mode or when necessary, just reach over and
start
pumping the jack, since the jack isn't attached to the upper
lever.
There's
many times I suspect that the jack's job is over, and the rest of
the
operation requires less pressure, so all you have to do is just
reach up and
pull.

|
| Ned Simmons

Thanks for sticking with me this far through it! Your input
has
been
invaluable.

One problem I see is the jack might have to be on pivots if the ram
is
going to move any appreciable distance. The pivoting arm isn't going
to stay parallel with the pad the jack is sitting on, and the
contact
point along the pivoting arm will change too. I suspect the ram may
tend to bind in the socket, too.

I'd be tempted to make a wood or cardboard model of the linkage
first

On second thought, having the jack on pivots would introduce a force
along the axis if the pivoting arm once the arm was not parallel. A
roller on the top of the jack would reduce that..

The linkage reminds me of that found on a pitcher pump....

"Ned Simmons" wrote in message
...
SNIP
| I'm afraid I'm not following this. Are you saying that the
| horizontal tube is not carrying the force being applied by
| the press ram? The situation is not as simple as if the
| jack were at the end of the arm and acting directly, but
| the horizontal tube is still carrying a considerable load.
|

Okay, I had to draw it out in a line diagram to see it. The link will
be pulling up on the horizontal tube, so the force will be a cantilever up.
The vertical ram passes through the sleeve at the end, so it can't flex too
much or it will bind. Maybe it would be worth it to shorten that sleeve a
lot. I had to remove the connection between the horizontal tube and the
vertical ram to get that out of my head, then the large up forces show up as
a simple lever. I can up the sizes of the tubing to make the horizontal
stronger, since it's a slip joint. If I were to weld in straps on the upper
and lower sides of the tube using plug welds, it wouldn't affect for the
slip joint, but will stiffen things up in the vertical direction. I had
thought about doing that with an entire second piece of tubing telescoped
and welded inside, so maybe that's an option. Or both, as long as I can get
a pin in it. Any good ideas in that respect?