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Ignoramus27175
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 Posted: Tue Jun 05, 2007 12:04 am Post subject: Would this structure collapse or not? (Bridgeport mill base) |
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I built a mobile base for a Bridgeport mill. (2,200 lbs)
It is shown here, along with copious comments (pasted here at the bottom).
http://igor.chudov.com/projects/My-Bridgeport-Mill/Mobile-Bridgeport-Mill-Base-On-Casters/
This base will be used for slowly moving the 2,200 lbs mill on
concrete floor (garage), with one groove in the floor.
Do you think that it is adequate?
======================================================================
Pictured here is a homemade base for a Bridgeport mill that runs on
casters.
Design Objectives
* A failure of the base should not make the mill fall (hence it
needed small floor clearance)
* The bars with casters should be removable so as not to take
valuable floor space and not to be a tripping hazard
* During operation, the mill would stand on 2x4s beneath the base,
with casters removed
* Bars with Casters should be easy to mount again if the mill
needs to be moved.
Some notes
The base is made from 1/4" flat stock (1/4" by 5" steel bar) and 1/4"
angle iron. The bars holding casters are 3/16" thick 1.25" steel
square tubing.
The casters are something to behold, these are NOT the usual Harbor
Freight "heavy duty" casters. I bought them on eBay for $40, Here's
the auction screenshot. They are rated for 2,400 lbs each, all swivel,
and are made from very heavy plate. (1/2" and 3/8")
The welded-on T-nut with a bolt in it (seen in front) was attached to
provide attachment point for an eyebolt in case if the mill needs to
be pulled. It is threaded for 1/2"-13 NC. The bolt is there just to
show it better, it will be replaced with an eyebolt.
Enjoy the video of this base being gently kicked.
The internal dimensions of the base are 1/2" more than the dimensions
of the bridgeport base.
Credits -- the PDF file showing Bridgeport mill base dimensions was
created by Richard Kinch (see his shop). As a thank you, here's an SEO
friendly organic link to his site: TeX for Windows.
The base weighs 160 lbs. |
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dlzc
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| Posted: Tue Jun 05, 2007 1:02 am Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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Dear Ignoramus27175:
On Jun 4, 12:04 pm, Ignoramus27175 <ignoramus27...@NOSPAM.
27175.invalid> wrote:
| Quote: |
I built a mobile base for a Bridgeport mill. (2,200 lbs)
It is shown here, along with copious comments (pasted here at
the bottom).
http://igor.chudov.com/projects/My-Bridgeport-Mill/Mobile-Bridgeport-...
This base will be used for slowly moving the 2,200 lbs mill on
concrete floor (garage), with one groove in the floor.
Do you think that it is adequate?
|
I worry about:
- vibration, depending on what you put in the Bridgeport
- getting electricity to it, and
- I don't see any lock on those casters. Do any of those wheels
lock? Should have at least two that lock.
With that "groove" you mention in the floor, it would not take much to
generate 4g's and fail the bearings in the casters.
I guess based on your description that you don't intend to leave the
casters installed during operation. What does the concrete bearing
surface look like? Have you created a wedge suitable for concrete
demolition?
David A. Smith |
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Ignoramus27175
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| Posted: Tue Jun 05, 2007 1:18 am Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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On Mon, 04 Jun 2007 13:02:13 -0700, dlzc <dlzc1@cox.net> wrote:
| Quote: |
Dear Ignoramus27175:
On Jun 4, 12:04 pm, Ignoramus27175 <ignoramus27...@NOSPAM.
27175.invalid> wrote:
I built a mobile base for a Bridgeport mill. (2,200 lbs)
It is shown here, along with copious comments (pasted here at
the bottom).
http://igor.chudov.com/projects/My-Bridgeport-Mill/Mobile-Bridgeport-...
This base will be used for slowly moving the 2,200 lbs mill on
concrete floor (garage), with one groove in the floor.
Do you think that it is adequate?
I worry about:
- vibration, depending on what you put in the Bridgeport
- getting electricity to it, and
- I don't see any lock on those casters. Do any of those wheels
lock? Should have at least two that lock.
|
They do not lock, however, I have moved a lot of stuff on casters and
always use chocks.
| Quote: |
With that "groove" you mention in the floor, it would not take much to
generate 4g's and fail the bearings in the casters.
I guess based on your description that you don't intend to leave the
casters installed during operation. What does the concrete bearing
surface look like? Have you created a wedge suitable for concrete
demolition?
|
I will not run the mill while it is on casters, casters are mounted on
bars which are removable. (other than just trying it for a couple of
times). It will be powered via a VFD, which I already have and set
up for 1HP.
Good point on the groove -- I will try to either fill it or insert a
suitable round rod into the groove. The groove is about 1/2" wide.
My question is, mainly, do you think that the frame will hold up under
described use.
I am not sure I understand your question regarding concrete
demolition, the mill will sit on the shown base, which in turn will be
sitting on top of 2x4s lying flat. To remove or insert 2x4s, I will
use a car jack, most likely.
i |
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N:dlzc D:aol T:com (dlzc)
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| Posted: Tue Jun 05, 2007 7:30 am Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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Dear Ignoramus27175:
"Ignoramus27175" <ignoramus27175@NOSPAM.27175.invalid> wrote in
message news:A_GdnQEpUewW7vnbnZ2dnUVZ_qKqnZ2d@giganews.com...
....
| Quote: |
My question is, mainly, do you think that the frame will
hold up under described use.
|
Does the bridgeport straddle the "box", or sit down inside it? I
worry about those unreinforced joints at the bottom of the box if
the latter, and the lack of diagonal bracing (or at least corner
bracing) if the former.
| Quote: |
I am not sure I understand your question regarding concrete
demolition, the mill will sit on the shown base, which in turn
will be sitting on top of 2x4s lying flat. To remove or insert
2x4s, I will use a car jack, most likely.
|
You could build the 2x4s into the frame bottom. If the frame
does not cut the 2x4, then you have no issues.
David A. Smith |
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Ignoramus27175
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| Posted: Tue Jun 05, 2007 8:12 am Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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On Mon, 4 Jun 2007 19:30:11 -0700, N:dlzc D:aol T:com (dlzc) <dlzc@aol.com> wrote:
| Quote: |
Dear Ignoramus27175:
"Ignoramus27175" <ignoramus27175@NOSPAM.27175.invalid> wrote in
message news:A_GdnQEpUewW7vnbnZ2dnUVZ_qKqnZ2d@giganews.com...
...
My question is, mainly, do you think that the frame will
hold up under described use.
Does the bridgeport straddle the "box", or sit down inside it? I
worry about those unreinforced joints at the bottom of the box if
the latter, and the lack of diagonal bracing (or at least corner
bracing) if the former.
|
The box is approximately 1/2" wider in both dimensions than are the
dimensions of the base. So, if the base is placed in the center, there
would be approximately 1/4" distance between the base and the walls of
the box. That's why I hope that the bottom bars will not bend too
much, as they have nowhere to go.
Note though that I will appreciate opinions of real engineers (I am a
"software engineer" a.k.a. computer programmer, and not a mechanical
eingineer).
| Quote: |
I am not sure I understand your question regarding concrete
demolition, the mill will sit on the shown base, which in turn
will be sitting on top of 2x4s lying flat. To remove or insert
2x4s, I will use a car jack, most likely.
You could build the 2x4s into the frame bottom. If the frame
does not cut the 2x4, then you have no issues.
|
Well, but I like the flexibility of being able to install or remove
2x4s.
i |
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N:dlzc D:aol T:com (dlzc)
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| Posted: Tue Jun 05, 2007 9:15 am Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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Dear Ignoramus27175:
"Ignoramus27175" <ignoramus27175@NOSPAM.27175.invalid> wrote in
message news:S_qdnYJfHKU2SfnbnZ2dnUVZ_qiqnZ2d@giganews.com...
| Quote: |
On Mon, 4 Jun 2007 19:30:11 -0700, N:dlzc D:aol T:com (dlzc)
dlzc@aol.com> wrote:
Dear Ignoramus27175:
"Ignoramus27175" <ignoramus27175@NOSPAM.27175.invalid> wrote
in
message news:A_GdnQEpUewW7vnbnZ2dnUVZ_qKqnZ2d@giganews.com...
...
My question is, mainly, do you think that the frame will
hold up under described use.
Does the bridgeport straddle the "box", or sit down inside it?
I
worry about those unreinforced joints at the bottom of the box
if
the latter, and the lack of diagonal bracing (or at least
corner
bracing) if the former.
The box is approximately 1/2" wider in both dimensions than
are the dimensions of the base. So, if the base is placed in
the center, there would be approximately 1/4" distance
between the base and the walls of the box. That's why I hope
that the bottom bars will not bend too much, as they have
nowhere to go.
|
Oh. Well, if the welds don't break right off, the "flat bar"
members will probably never clear the floor. They will arc down,
trying to get necessary support from the floor. I would guess
you will need 3 or more inches lift before the center of the flat
bars clear the floor.
Where the "1/4 x 4 inch" flat bars cross the bottom of the box...
is this where the normal support feet of the bridgeport are
located?
Is the base of the bridgeport hollow, such that away (4" or so
from outer walls) from the box edges, the flat bars could be made
thicker / taller?
| Quote: |
Note though that I will appreciate opinions of real engineers
(I am a "software engineer" a.k.a. computer programmer, and
not a mechanical eingineer).
|
I forgive you. ;>)
You would similarly turn your nose up at my coding style...
| Quote: |
You could build the 2x4s into the frame bottom. If the frame
does not cut the 2x4, then you have no issues.
Well, but I like the flexibility of being able to install or
remove
2x4s.
|
I love the idea of looking for sacrificial 2x4s, after having
left them behind where the machine came from. It is your labor.
"Let each man lay his dead according to his own fashion."
Seems like a lag bolt shot through a hole in the base would work
just fine. And enable future replacement without difficulty.
David A. Smith |
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Ignoramus20900
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| Posted: Tue Jun 05, 2007 4:19 pm Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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On Mon, 4 Jun 2007 21:15:27 -0700, N:dlzc D:aol T:com (dlzc) <dlzc@aol.com> wrote:
| Quote: |
Dear Ignoramus27175:
"Ignoramus27175" <ignoramus27175@NOSPAM.27175.invalid> wrote in
message news:S_qdnYJfHKU2SfnbnZ2dnUVZ_qiqnZ2d@giganews.com...
On Mon, 4 Jun 2007 19:30:11 -0700, N:dlzc D:aol T:com (dlzc)
dlzc@aol.com> wrote:
Dear Ignoramus27175:
"Ignoramus27175" <ignoramus27175@NOSPAM.27175.invalid> wrote
in
message news:A_GdnQEpUewW7vnbnZ2dnUVZ_qKqnZ2d@giganews.com...
...
My question is, mainly, do you think that the frame will
hold up under described use.
Does the bridgeport straddle the "box", or sit down inside it?
I
worry about those unreinforced joints at the bottom of the box
if
the latter, and the lack of diagonal bracing (or at least
corner
bracing) if the former.
The box is approximately 1/2" wider in both dimensions than
are the dimensions of the base. So, if the base is placed in
the center, there would be approximately 1/4" distance
between the base and the walls of the box. That's why I hope
that the bottom bars will not bend too much, as they have
nowhere to go.
Oh. Well, if the welds don't break right off, the "flat bar"
members will probably never clear the floor. They will arc down,
trying to get necessary support from the floor. I would guess
you will need 3 or more inches lift before the center of the flat
bars clear the floor.
Where the "1/4 x 4 inch" flat bars cross the bottom of the box...
is this where the normal support feet of the bridgeport are
located?
|
A Bridgeport mill does not have feet, it has a flat rectangular
base. So, I hope that the flat 1/4x5 inch bars will support it on the
outside perimeter of the base.
| Quote: |
Is the base of the bridgeport hollow, such that away (4" or so
from outer walls) from the box edges, the flat bars could be made
thicker / taller?
|
I think that it is not hollow.
i |
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jim
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| Posted: Tue Jun 05, 2007 4:29 pm Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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Ignoramus27175 wrote:
| Quote: |
On Mon, 4 Jun 2007 19:30:11 -0700, N:dlzc D:aol T:com (dlzc) <dlzc@aol.com> wrote:
Dear Ignoramus27175:
"Ignoramus27175" <ignoramus27175@NOSPAM.27175.invalid> wrote in
message news:A_GdnQEpUewW7vnbnZ2dnUVZ_qKqnZ2d@giganews.com...
...
My question is, mainly, do you think that the frame will
hold up under described use.
Does the bridgeport straddle the "box", or sit down inside it? I
worry about those unreinforced joints at the bottom of the box if
the latter, and the lack of diagonal bracing (or at least corner
bracing) if the former.
The box is approximately 1/2" wider in both dimensions than are the
dimensions of the base. So, if the base is placed in the center, there
would be approximately 1/4" distance between the base and the walls of
the box. That's why I hope that the bottom bars will not bend too
much, as they have nowhere to go.
|
I don't see bending the bottom of the "box" itself to be any problem.
Putting the flat pieces diagonally at the corners might have been
better. If you put your weight on the flats about 4" from the edge that
will cause about as much bending as the weight of the mill at 1/2" from
the edge.
If I understand your design the weight of the mill is supported on the
4 bolts that go thru the square tubes, That looks to me to be the
weakest point of the design. At the very least you should have some big
heavy washer under the nuts to spread the load a little.
Seems to me the whole "box" thing is superfluous. Usually the base of a
mill will have drilled holes so that the mill can be bolted to the floor
or set on adjustable feet for leveling. Your 2 pieces with the square
tube and castors could be bolted directly to the mill base instead of to
the box.
-jim
| Quote: |
Note though that I will appreciate opinions of real engineers (I am a
"software engineer" a.k.a. computer programmer, and not a mechanical
eingineer).
I am not sure I understand your question regarding concrete
demolition, the mill will sit on the shown base, which in turn
will be sitting on top of 2x4s lying flat. To remove or insert
2x4s, I will use a car jack, most likely.
You could build the 2x4s into the frame bottom. If the frame
does not cut the 2x4, then you have no issues.
Well, but I like the flexibility of being able to install or remove
2x4s.
i
|
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Ignoramus20900
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| Posted: Tue Jun 05, 2007 5:49 pm Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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On Tue, 05 Jun 2007 06:29:35 -0500, jim <"sjedgingN0sp"@m> wrote:
| Quote: |
Ignoramus27175 wrote:
On Mon, 4 Jun 2007 19:30:11 -0700, N:dlzc D:aol T:com (dlzc) <dlzc@aol.com> wrote:
Dear Ignoramus27175:
"Ignoramus27175" <ignoramus27175@NOSPAM.27175.invalid> wrote in
message news:A_GdnQEpUewW7vnbnZ2dnUVZ_qKqnZ2d@giganews.com...
...
My question is, mainly, do you think that the frame will
hold up under described use.
Does the bridgeport straddle the "box", or sit down inside it? I
worry about those unreinforced joints at the bottom of the box if
the latter, and the lack of diagonal bracing (or at least corner
bracing) if the former.
The box is approximately 1/2" wider in both dimensions than are the
dimensions of the base. So, if the base is placed in the center, there
would be approximately 1/4" distance between the base and the walls of
the box. That's why I hope that the bottom bars will not bend too
much, as they have nowhere to go.
I don't see bending the bottom of the "box" itself to be any problem.
Putting the flat pieces diagonally at the corners might have been
better.
|
I agree. Note though that the flat bottom pieces, also have "lips"
that connect them to the front and rear of the box, that, to me, sort
of acts more like a corner.
| Quote: |
If you put your weight on the flats about 4" from the edge that
will cause about as much bending as the weight of the mill at 1/2" from
the edge.
|
OK, that's exactly what I will do, will place some thin plywood flats
along the sides so that the mill's foundation applies its weight close
to the sides of the box.
| Quote: |
If I understand your design the weight of the mill is supported on the
4 bolts that go thru the square tubes, That looks to me to be the
|
4 bolts that go through steel angle.
| Quote: |
weakest point of the design. At the very least you should have some big
heavy washer under the nuts to spread the load a little.
|
OK. I used 1/2" bolts. I will indeed use such washers as you say, thanks.
| Quote: |
Seems to me the whole "box" thing is superfluous. Usually the base of a
mill will have drilled holes so that the mill can be bolted to the floor
or set on adjustable feet for leveling. Your 2 pieces with the square
tube and castors could be bolted directly to the mill base instead of to
the box.
|
The purpose of this setup is to make the mill movable around my
garage, and the casters detachable so that they are not a trip hazard,
dop not flatten out from weight etc. For regular operation, casters
will be removed and the square box set on 2x4s.
i |
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jim
Guest
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| Posted: Tue Jun 05, 2007 7:33 pm Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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Ignoramus20900 wrote:
| Quote: |
I don't see bending the bottom of the "box" itself to be any problem.
Putting the flat pieces diagonally at the corners might have been
better.
I agree. Note though that the flat bottom pieces, also have "lips"
that connect them to the front and rear of the box, that, to me, sort
of acts more like a corner.
If you put your weight on the flats about 4" from the edge that
will cause about as much bending as the weight of the mill at 1/2" from
the edge.
OK, that's exactly what I will do, will place some thin plywood flats
along the sides so that the mill's foundation applies its weight close
to the sides of the box.
|
Well I don't think that is really necessary but probably won't hurt
either. The weight will naturally rest on the outer edge of the cast
base. As soon as the flat pieces bend even the tiniest amount all the
weight will be on the outer edge of the mill base (which won't bend). If
the welds can hold the weight there shouldn't be a problem.
| Quote: |
If I understand your design the weight of the mill is supported on the
4 bolts that go thru the square tubes, That looks to me to be the
4 bolts that go through steel angle.
weakest point of the design. At the very least you should have some big
heavy washer under the nuts to spread the load a little.
OK. I used 1/2" bolts. I will indeed use such washers as you say, thanks.
|
Yes each 1/2 in. bolt should support several tons, but will the square
tube support the weight concentrated at one point? That point being also
the weakest spot due to the drilled hole. The angle iron or flat iron
underneath doesn't really do anything to keep the square tube from
bending or collapsing.
| Quote: |
Seems to me the whole "box" thing is superfluous. Usually the base of a
mill will have drilled holes so that the mill can be bolted to the floor
or set on adjustable feet for leveling. Your 2 pieces with the square
tube and castors could be bolted directly to the mill base instead of to
the box.
The purpose of this setup is to make the mill movable around my
garage, and the casters detachable so that they are not a trip hazard,
dop not flatten out from weight etc. For regular operation, casters
will be removed and the square box set on 2x4s.
|
Yes I understand. You are hanging the thing from 4 bolts. Alternatively,
the 4 bolts could be coming up thru the holes in the mill base itself.
In theory it could be designed so you had 4 bolts or studs sticking up
thru the base. You would slide one of your pieces with castors attached
over 2 of the bolts and tighten down the 2 nuts and it would lift the
mill off the floor on one side. Do the same for the other side and the
mill is completely off the floor and can be moved. Lifting it 1/4"
should be enough if the floor is very flat. Ultimately it still comes
down to making the cross member (what is now a square tube) sufficiently
strong and rigid.
You also should consider twisting forces on the square tube. When the
castors are at right angles to the tube there will be quite a bit of
force twisting the tube. The tube may be able to handle that but the
bolts may not and bend and eventually break.
-jim
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Ignoramus20900
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| Posted: Tue Jun 05, 2007 7:49 pm Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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On Tue, 05 Jun 2007 09:33:51 -0500, jim <"sjedgingN0sp"@m> wrote:
| Quote: |
Ignoramus20900 wrote:
I don't see bending the bottom of the "box" itself to be any problem.
Putting the flat pieces diagonally at the corners might have been
better.
I agree. Note though that the flat bottom pieces, also have "lips"
that connect them to the front and rear of the box, that, to me, sort
of acts more like a corner.
If you put your weight on the flats about 4" from the edge that
will cause about as much bending as the weight of the mill at 1/2" from
the edge.
OK, that's exactly what I will do, will place some thin plywood flats
along the sides so that the mill's foundation applies its weight close
to the sides of the box.
Well I don't think that is really necessary but probably won't hurt
either. The weight will naturally rest on the outer edge of the cast
base. As soon as the flat pieces bend even the tiniest amount all the
weight will be on the outer edge of the mill base (which won't bend). If
the welds can hold the weight there shouldn't be a problem.
|
Thanks. (like I said, even if the base fails in any manner, no danger
to life will result due to low ground clearance, just an
embarrassment). I am happy that you think that it should hold.
The welds are quite solid, made with dry good E 7018 electrodes, I
have full faith that they are at least half strong as solid steel of
the same cross section.
| Quote: |
If I understand your design the weight of the mill is supported on the
4 bolts that go thru the square tubes, That looks to me to be the
4 bolts that go through steel angle.
weakest point of the design. At the very least you should have some big
heavy washer under the nuts to spread the load a little.
OK. I used 1/2" bolts. I will indeed use such washers as you say, thanks.
Yes each 1/2 in. bolt should support several tons, but will the square
tube support the weight concentrated at one point? That point being also
the weakest spot due to the drilled hole. The angle iron or flat iron
underneath doesn't really do anything to keep the square tube from
bending or collapsing.
|
OK, I see your point now.
A couple of days ago, I used the metalgeek calculator here:
http://www.metalgeek.com/archives/2004/10/03/000039.php
and entered 1.25" square tube, supported on both ends, 18" long (twise
the bending radius of 9 inches), 0.188" thick, with 1,200 lbs applied
in the center.
The calculated deflection came out to be 0.0082".
That IGNORED the drilled bolt hole, so the calculation is not
definitive, however, it gives some hope.
You have a great point on twisting, which I am not competent at all to
even look at and was just going by the seat of my pants.
Worst case is, if this tubing fails, I will unbolt it and buy bigger
tubing.
| Quote: |
Seems to me the whole "box" thing is superfluous. Usually the base of a
mill will have drilled holes so that the mill can be bolted to the floor
or set on adjustable feet for leveling. Your 2 pieces with the square
tube and castors could be bolted directly to the mill base instead of to
the box.
The purpose of this setup is to make the mill movable around my
garage, and the casters detachable so that they are not a trip hazard,
dop not flatten out from weight etc. For regular operation, casters
will be removed and the square box set on 2x4s.
Yes I understand. You are hanging the thing from 4 bolts. Alternatively,
the 4 bolts could be coming up thru the holes in the mill base itself.
In theory it could be designed so you had 4 bolts or studs sticking up
thru the base. You would slide one of your pieces with castors attached
over 2 of the bolts and tighten down the 2 nuts and it would lift the
mill off the floor on one side. Do the same for the other side and the
mill is completely off the floor and can be moved. Lifting it 1/4"
should be enough if the floor is very flat. Ultimately it still comes
down to making the cross member (what is now a square tube) sufficiently
strong and rigid.
|
Yes.
| Quote: |
You also should consider twisting forces on the square tube. When the
castors are at right angles to the tube there will be quite a bit of
force twisting the tube. The tube may be able to handle that but the
bolts may not and bend and eventually break.
|
I am hoping, personally, that if the bolt is tightened strongly, then
the bending force would not be great. Would you think that it is not
warranted?
i |
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Jeff Finlayson
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| Posted: Wed Jun 06, 2007 6:11 pm Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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Ignoramus27175 wrote:
| Quote: |
I built a mobile base for a Bridgeport mill. (2,200 lbs)
It is shown here, along with copious comments (pasted here at the bottom).
http://igor.chudov.com/projects/My-Bridgeport-Mill/Mobile-Bridgeport-Mill-Base-On-Casters/
This base will be used for slowly moving the 2,200 lbs mill on
concrete floor (garage), with one groove in the floor.
Do you think that it is adequate?
======================================================================
Pictured here is a homemade base for a Bridgeport mill that runs on
casters.
Design Objectives
* A failure of the base should not make the mill fall (hence it
needed small floor clearance)
* The bars with casters should be removable so as not to take
valuable floor space and not to be a tripping hazard
* During operation, the mill would stand on 2x4s beneath the base,
with casters removed
* Bars with Casters should be easy to mount again if the mill
needs to be moved.
Some notes
The base is made from 1/4" flat stock (1/4" by 5" steel bar) and 1/4"
angle iron. The bars holding casters are 3/16" thick 1.25" steel
square tubing.
The casters are something to behold, these are NOT the usual Harbor
Freight "heavy duty" casters. I bought them on eBay for $40, Here's
the auction screenshot. They are rated for 2,400 lbs each, all swivel,
and are made from very heavy plate. (1/2" and 3/8")
The welded-on T-nut with a bolt in it (seen in front) was attached to
provide attachment point for an eyebolt in case if the mill needs to
be pulled. It is threaded for 1/2"-13 NC. The bolt is there just to
show it better, it will be replaced with an eyebolt.
Enjoy the video of this base being gently kicked.
The internal dimensions of the base are 1/2" more than the dimensions
of the bridgeport base.
Credits -- the PDF file showing Bridgeport mill base dimensions was
created by Richard Kinch (see his shop). As a thank you, here's an SEO
friendly organic link to his site: TeX for Windows.
The base weighs 160 lbs.
|
The diagonal cross member is not doing much good. That's for
reinforcing against shear loads and most of your loading will be normal
to the frame (downward). Under load it could deform downward a fair
amount. Short diagonal members or triangular pieces in the corners
would be better, I think.
You can test it out and see if the diagonal member comes close to
touching the floor and redesign as needed then. Good luck.
Jeff |
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Ignoramus27187
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| Posted: Wed Jun 06, 2007 6:34 pm Post subject: Re: Would this structure collapse or not? (Bridgeport mill b |
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|
On Wed, 06 Jun 2007 08:11:25 -0500, Jeff Finlayson <finlayson@hiwaaay.not> wrote:
| Quote: |
Ignoramus27175 wrote:
I built a mobile base for a Bridgeport mill. (2,200 lbs)
It is shown here, along with copious comments (pasted here at the bottom).
http://igor.chudov.com/projects/My-Bridgeport-Mill/Mobile-Bridgeport-Mill-Base-On-Casters/
This base will be used for slowly moving the 2,200 lbs mill on
concrete floor (garage), with one groove in the floor.
Do you think that it is adequate?
======================================================================
Pictured here is a homemade base for a Bridgeport mill that runs on
casters.
Design Objectives
* A failure of the base should not make the mill fall (hence it
needed small floor clearance)
* The bars with casters should be removable so as not to take
valuable floor space and not to be a tripping hazard
* During operation, the mill would stand on 2x4s beneath the base,
with casters removed
* Bars with Casters should be easy to mount again if the mill
needs to be moved.
Some notes
The base is made from 1/4" flat stock (1/4" by 5" steel bar) and 1/4"
angle iron. The bars holding casters are 3/16" thick 1.25" steel
square tubing.
The casters are something to behold, these are NOT the usual Harbor
Freight "heavy duty" casters. I bought them on eBay for $40, Here's
the auction screenshot. They are rated for 2,400 lbs each, all swivel,
and are made from very heavy plate. (1/2" and 3/8")
The welded-on T-nut with a bolt in it (seen in front) was attached to
provide attachment point for an eyebolt in case if the mill needs to
be pulled. It is threaded for 1/2"-13 NC. The bolt is there just to
show it better, it will be replaced with an eyebolt.
Enjoy the video of this base being gently kicked.
The internal dimensions of the base are 1/2" more than the dimensions
of the bridgeport base.
Credits -- the PDF file showing Bridgeport mill base dimensions was
created by Richard Kinch (see his shop). As a thank you, here's an SEO
friendly organic link to his site: TeX for Windows.
The base weighs 160 lbs.
Note, check out my later thread saying that the mill is installed in |
the base and things look OK.
| Quote: |
The diagonal cross member is not doing much good.
|
I agree. I only tacked it for the purposes of making this thing rigid
before welding.
| Quote: |
That's for reinforcing against shear loads and most of your loading
will be normal to the frame (downward). Under load it could deform
downward a fair amount. Short diagonal members or triangular pieces
in the corners would be better, I think.
You can test it out and see if the diagonal member comes close to
touching the floor and redesign as needed then. Good luck.
|
I removed the diagonal member prior to installing the mill in the
base.
There are little lips that connect the middle of the crossmembers, to
the front and back sides of the frame, which, I hope, are helping to
keep this structure more rigid.
See the mill in casters here:
http://igor.chudov.com/projects/My-Bridgeport-Mill/Mobile-Bridgeport-Mill-Base-On-Casters/
i |
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