Alan Bottomley, the inventor of the Magnabend has posted some
information on his web site. Not the User's Manual, which has always
been available, but Principles of Operation (magnetic & electrical). He
has a place mark for "Build Your Own Magnabend", which I eagerly await.

Good stuff Maynard, check it out:
http://aaybee.com.au/Magnabend/Magna...0Homepage.html

Bob

Bob Engelhardt fired this volley in
:

He
has a place mark for "Build Your Own Magnabend", which I eagerly await.


Ok... I'm lost. What more useful functions does this fairly complex and
expensive device have over a conventional clamp-bar style of brake?
Certainly, the mechanism is no simpler than a mechanical one.

That it works is not in question, but it has severe drawbacks -- like not
maintaining clamping force with thick sections, or when doing sharp
bends.

WHY would someone want a brake that cannot be counted on to do exactly
what the designer asked in the drawings?

LLoyd

Lloyd E. Sponenburgh wrote:

Ok... I'm lost. What more useful functions does this fairly complex and
expensive device have over a conventional clamp-bar style of brake?
...

The video says it better than I could:
http://www.youtube.com/watch?v=OipSiPSRti8

Bob

Bob Engelhardt fired this volley in
:

http://www.youtube.com/watch?v=OipSiPSRti8

Ok... I get it! It was only a little special until I saw the small
"insert" special formers. Then, it was special.

Ok... Where do I get one? G

LLoyd

On Sun, 03 Apr 2011 20:25:03 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Bob Engelhardt fired this volley in
:

http://www.youtube.com/watch?v=OipSiPSRti8

Ok... I get it! It was only a little special until I saw the small
"insert" special formers. Then, it was special.

Ok... Where do I get one? G

http://goo.gl/xjsaz Double that price to include shipping from the
other side of the galaxy.

--
Not merely an absence of noise, Real Silence begins
when a reasonable being withdraws from the noise in
order to find peace and order in his inner sanctuary.
-- Peter Minard

MSC carries them in the US - www.mscdirect.com. Also seen on ebay, and
there may be other suppliers.

--
-----
Regards,
Carl Ijames

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
.70...
Bob Engelhardt fired this volley in
:

http://www.youtube.com/watch?v=OipSiPSRti8

Ok... I get it! It was only a little special until I saw the small
"insert" special formers. Then, it was special.

Ok... Where do I get one? G

LLoyd

Bob Engelhardt wrote:
Alan Bottomley, the inventor of the Magnabend has posted some
information on his web site. Not the User's Manual, which has always
been available, but Principles of Operation (magnetic & electrical). He
has a place mark for "Build Your Own Magnabend", which I eagerly await.

Good stuff Maynard, check it out:
http://aaybee.com.au/Magnabend/Magna...0Homepage.html

Cool! Thanks Bob!

--Winston

In article ,
says...
Lloyd E. Sponenburgh wrote:

Ok... I'm lost. What more useful functions does this fairly complex
and
expensive device have over a conventional clamp-bar style of brake?
...

The video says it better than I could:
http://www.youtube.com/watch?v=OipSiPSRti8


The Magnabend is a really cool device. I do have to mention a far
cheaper solution for those who need an occasional bender for home use.
It's also available from Harbor Freight and other places.

http://www.eastwood.com/30-mighty-br...ing-brake.html

Like the Magnabend, the advantage lies with the removable hold down bar.
By making a variety of shorter bars as you need them, any size box can
be made. You do have to get C clamps on the bar instead of using
magnetic force, but that is not a problem for most things I have made.

It would make most things that Magnabend showed in the video, even the
odd angled box where the clamp bar ends up inside.. You simply have to
make a custom clamp bar like they did. I think it will do everything
except when they had the end of the box outside the edge of the machine.

It will even do the pipe trick to make large radius bends, by welding a
pipe to the edge of a clamp bar like they did.

The little bender is not a toy. It is slow, it's certainly not a
production tool, but it you don't need a bender that often, well worth
looking at.

I always had sheet metal tools available and when I retired this was the
bender I bought, and haven't looked back.

--
DT

Bob Engelhardt wrote:
Alan Bottomley, the inventor of the Magnabend has posted some
information on his web site. Not the User's Manual, which has always
been available, but Principles of Operation (magnetic & electrical). He
has a place mark for "Build Your Own Magnabend", which I eagerly await.

Good stuff Maynard, check it out:
http://aaybee.com.au/Magnabend/Magna...0Homepage.html

Bob

The "Build Your Own Magnabend" section is available and it's very
interesting. It's something of a work in progress, but mostly complete:
http://aaybee.com.au/Magnabend/Build...Magnabend.html

Also, Alan has also been posting to the MagnaBend thread on the
Practical Machinist forum:
http://www.practicalmachinist.com/vb...ml#post1551641
or
http://tinyurl.com/3dqpheg

As much as I enjoy building stuff from scrounged parts & material (e.g.,
MOTs), I'm starting to get The Fever for a built-right Magnabend. Just
now, when there's so much house & garden stuff to do. Sigh.

Bob

Bob Engelhardt wrote:

The "Build Your Own Magnabend" section is available and it's very
interesting.

Alan reveals some very interesting stuff here that I suspected but
did not know for su

* The 'E' core is more efficient than the 'U' core.

* Clamping force for the 'E' core falls off significantly on the ends
because of the narrowed middle pole.

* Regular door hinges are a practical substitute for the complicated
biaxial set used on the commercial model.

Thanks again, Bob!

--Winston

On Sun, 17 Apr 2011 13:33:11 -0700, Winston
wrote:

Bob Engelhardt wrote:

The "Build Your Own Magnabend" section is available and it's very
interesting.

Alan reveals some very interesting stuff here that I suspected but
did not know for su

* The 'E' core is more efficient than the 'U' core.

* Clamping force for the 'E' core falls off significantly on the ends
because of the narrowed middle pole.

* Regular door hinges are a practical substitute for the complicated
biaxial set used on the commercial model.

Thanks again, Bob!

--Winston

Good stuff and very useful but I'm a bit worried by the simple
statement that the E core is more efficient.

A lot depends on both the assumptions made and the detail
design. The E core design may not necessarily the most efficient.
However the differences are not large enough to be important in
home brew projects.

Jim

wrote:
On Sun, 17 Apr 2011 13:33:11 -0700, Winston
wrote:

Bob Engelhardt wrote:

The "Build Your Own Magnabend" section is available and it's very
interesting.

Alan reveals some very interesting stuff here that I suspected but
did not know for su

* The 'E' core is more efficient than the 'U' core.

* Clamping force for the 'E' core falls off significantly on the ends
because of the narrowed middle pole.

* Regular door hinges are a practical substitute for the complicated
biaxial set used on the commercial model.

Thanks again, Bob!

--Winston

Good stuff and very useful but I'm a bit worried by the simple
statement that the E core is more efficient.

A lot depends on both the assumptions made and the detail
design. The E core design may not necessarily the most efficient.
However the differences are not large enough to be important in
home brew projects.

Alan Unless you have very good milling facilities then I suggest
Alan that you go for a U-type magnet body. Although this design
Alan is not quite as efficient as an E-type body...

Given the inverse - cube character of magnetic attraction vs.
distance, it seems axiomatic that the two additional gaps
of the U core design should result in higher magnetic
reluctance than that of the E core, all else being equal.

Alan could be wrong on that point, I figured that he is in a
position to know, however....

--Winston

On Apr 18, 9:28*am, Winston wrote:
wrote:
On Sun, 17 Apr 2011 13:33:11 -0700, Winston
*wrote:

Bob Engelhardt wrote:

The "Build Your Own Magnabend" section is available and it's very
interesting.

Alan reveals some very interesting stuff here that I suspected but
did not know for su

* The 'E' core is more efficient than the 'U' core.

* Clamping force for the 'E' core falls off significantly on the ends
* *because of the narrowed middle pole.

* Regular door hinges are a practical substitute for the complicated
* *biaxial set used on the commercial model.

Thanks again, Bob!

--Winston

Good stuff and very useful but I'm a bit worried by the simple
statement that the E core is more efficient.

* A lot depends on both the assumptions made and the detail
design. The E core design may not necessarily the most efficient.
However the differences are not large enough to be important in
home brew projects.

Alan Unless you have very good milling facilities then I suggest
Alan that you go for a U-type magnet body. *Although this design
Alan is not quite as efficient as an E-type body...

Given the inverse - cube character of magnetic attraction vs.
distance, it seems axiomatic that the two additional gaps
of the U core design should result in higher magnetic
reluctance than that of the E core, all else being equal.

Alan could be wrong on that point, I figured that he is in a
position to know, however.... *

--Winston


I am following the developments in Practical Machinist and plan on
building the E-type bender just as described.

The hinging though is giving me pause. On the commercial magnabend
the hinge is such that the work piece may extent past the bender,
whereas this is not possible with the standard "door hinge" design. I
happen to think that this feature is desireable even in a home shop.

Going through Mechanisms, Linkages, and Mechanical Controls, there is
a hinge mechanism, a 6-bar linkage, that does away with the need for a
hinge pin at the corner of the bending leaf.

Unfortunately the brief description in the aforementioned book gives
no design rules for this mechanism. Since the various pivot points in
this linkage do not lie on straight lines, I suspect that the
synthesis of this mechanism is tricky. Hmmmm, maybe try and build
it from my old TRIX set? Wonder where it is?

Can anyone here shed some light on the design of this mechanism?
Thanks.

Wolfgang

wolfgang wrote:
On the commercial magnabend
the hinge is such that the work piece may extent past the bender,
whereas this is not possible with the standard "door hinge" design.

Why not?

See how Dave Clay handled that:
http://www.ch601.org/tools/bendbrake/brakeplans.pdf

--Winston

On Mon, 18 Apr 2011 06:28:24 -0700, Winston
wrote:

wrote:
On Sun, 17 Apr 2011 13:33:11 -0700, Winston
wrote:

Bob Engelhardt wrote:

The "Build Your Own Magnabend" section is available and it's very
interesting.

Alan reveals some very interesting stuff here that I suspected but
did not know for su

* The 'E' core is more efficient than the 'U' core.

* Clamping force for the 'E' core falls off significantly on the ends
because of the narrowed middle pole.

* Regular door hinges are a practical substitute for the complicated
biaxial set used on the commercial model.

Thanks again, Bob!

--Winston

Good stuff and very useful but I'm a bit worried by the simple
statement that the E core is more efficient.

A lot depends on both the assumptions made and the detail
design. The E core design may not necessarily the most efficient.
However the differences are not large enough to be important in
home brew projects.

Alan Unless you have very good milling facilities then I suggest
Alan that you go for a U-type magnet body. Although this design
Alan is not quite as efficient as an E-type body...

Given the inverse - cube character of magnetic attraction vs.
distance, it seems axiomatic that the two additional gaps
of the U core design should result in higher magnetic
reluctance than that of the E core, all else being equal.

Alan could be wrong on that point, I figured that he is in a
position to know, however....

--Winston

Just a few comments on magnetic attraction.

There is a comprehensive discussion in
http://en.wikipedia.org/wiki/Magnet

A brief summary may be useful.

Attractive force varies as square of the field strength

For a NS magnet of fixed field strength the far field strength
varies as cube of distance so the attractive force varies as
sixth power of the distance.

Close to end of long magnet (i.e.in small air gaps) the field
strength only varies as square of distance - so the force varies
as the fourth power of the distance.

These comments define "magnet field strength" as Amps/metre i.e
fixed coercive force. The resultant Flux density B is then
controlled by the cube or square relation.

With real magnets coercive force is a function of working flux
density so this is only true for an ideal square loop magnet.

This is a fair approximation for rare earth magnets but with
alnico or ceramic magnets field strength drop is even faster
because the working coercive force drops as the flux density
decreases

Jim

wrote:
On Mon, 18 Apr 2011 06:28:24 -0700, Winston
wrote:

wrote:
On Sun, 17 Apr 2011 13:33:11 -0700, Winston
wrote:

Bob Engelhardt wrote:

The "Build Your Own Magnabend" section is available and it's very
interesting.

Alan reveals some very interesting stuff here that I suspected but
did not know for su

* The 'E' core is more efficient than the 'U' core.

* Clamping force for the 'E' core falls off significantly on the ends
because of the narrowed middle pole.

* Regular door hinges are a practical substitute for the complicated
biaxial set used on the commercial model.

Thanks again, Bob!

--Winston

Good stuff and very useful but I'm a bit worried by the simple
statement that the E core is more efficient.

A lot depends on both the assumptions made and the detail
design. The E core design may not necessarily the most efficient.
However the differences are not large enough to be important in
home brew projects.

Alan Unless you have very good milling facilities then I suggest
Alan that you go for a U-type magnet body. Although this design
Alan is not quite as efficient as an E-type body...

Given the inverse - cube character of magnetic attraction vs.
distance, it seems axiomatic that the two additional gaps
of the U core design should result in higher magnetic
reluctance than that of the E core, all else being equal.

Alan could be wrong on that point, I figured that he is in a
position to know, however....

--Winston

Just a few comments on magnetic attraction.

There is a comprehensive discussion in
http://en.wikipedia.org/wiki/Magnet

A brief summary may be useful.

I should have said "given the nonlinear relationship of
magnetic attraction vs. distance ...."
I see the situation more clearly now; thanks, Jim.

FWIW, I suspect that the flux density inside our solenoid
(cross-section radius *inside* the core) falls as the fourth
power of the distance from the windings, yes?

--Winston

On Tue, 19 Apr 2011 09:15:43 -0700, Winston
wrote:

wrote:
On Mon, 18 Apr 2011 06:28:24 -0700, Winston
wrote:

wrote:
On Sun, 17 Apr 2011 13:33:11 -0700, Winston
wrote:

Bob Engelhardt wrote:

The "Build Your Own Magnabend" section is available and it's very
interesting.

Alan reveals some very interesting stuff here that I suspected but
did not know for su

* The 'E' core is more efficient than the 'U' core.

* Clamping force for the 'E' core falls off significantly on the ends
because of the narrowed middle pole.

* Regular door hinges are a practical substitute for the complicated
biaxial set used on the commercial model.

Thanks again, Bob!

--Winston

Good stuff and very useful but I'm a bit worried by the simple
statement that the E core is more efficient.

A lot depends on both the assumptions made and the detail
design. The E core design may not necessarily the most efficient.
However the differences are not large enough to be important in
home brew projects.

Alan Unless you have very good milling facilities then I suggest
Alan that you go for a U-type magnet body. Although this design
Alan is not quite as efficient as an E-type body...

Given the inverse - cube character of magnetic attraction vs.
distance, it seems axiomatic that the two additional gaps
of the U core design should result in higher magnetic
reluctance than that of the E core, all else being equal.

Alan could be wrong on that point, I figured that he is in a
position to know, however....

--Winston

Just a few comments on magnetic attraction.

There is a comprehensive discussion in
http://en.wikipedia.org/wiki/Magnet

A brief summary may be useful.

I should have said "given the nonlinear relationship of
magnetic attraction vs. distance ...."
I see the situation more clearly now; thanks, Jim.

FWIW, I suspect that the flux density inside our solenoid
(cross-section radius *inside* the core) falls as the fourth
power of the distance from the windings, yes?

--Winston


Like most things in magnetics there's no simple answer. Wiki is
again of some help http://en.wikipedia.org/wiki/Solenoid and
http://en.wikipedia.org/wiki/Electromagnet but once again you
have to choose which particular combination of approximations is
appropriate.

For a very long air cored winding (i.e. a long solenoid) the
internal flux density varies little and is almost independent of
the distance from the winding wires.

With a short air cored winding there is a rapid radial variation
of flux density but this is drastically modified as soon as an
iron core is present. For typical working permeabilities of 2000+
the flux distribution is effectively short circuited leaving
little radial variation.

For working flux densities approaching true saturation the
permeability drops with some return of radial variation but the
amount is strongly dependent on the particular shape of the iron
B/H characteristics and the geometry of the iron circuit.

Jim

wrote:
On Tue, 19 Apr 2011 09:15:43 -0700, Winston
wrote:

wrote:
On Mon, 18 Apr 2011 06:28:24 -0700, Winston
wrote:

wrote:
On Sun, 17 Apr 2011 13:33:11 -0700, Winston
wrote:

Bob Engelhardt wrote:

The "Build Your Own Magnabend" section is available and it's very
interesting.

Alan reveals some very interesting stuff here that I suspected but
did not know for su

* The 'E' core is more efficient than the 'U' core.

* Clamping force for the 'E' core falls off significantly on the ends
because of the narrowed middle pole.

* Regular door hinges are a practical substitute for the complicated
biaxial set used on the commercial model.

Thanks again, Bob!

--Winston

Good stuff and very useful but I'm a bit worried by the simple
statement that the E core is more efficient.

A lot depends on both the assumptions made and the detail
design. The E core design may not necessarily the most efficient.
However the differences are not large enough to be important in
home brew projects.

Alan Unless you have very good milling facilities then I suggest
Alan that you go for a U-type magnet body. Although this design
Alan is not quite as efficient as an E-type body...

Given the inverse - cube character of magnetic attraction vs.
distance, it seems axiomatic that the two additional gaps
of the U core design should result in higher magnetic
reluctance than that of the E core, all else being equal.

Alan could be wrong on that point, I figured that he is in a
position to know, however....

--Winston

Just a few comments on magnetic attraction.

There is a comprehensive discussion in
http://en.wikipedia.org/wiki/Magnet

A brief summary may be useful.

I should have said "given the nonlinear relationship of
magnetic attraction vs. distance ...."
I see the situation more clearly now; thanks, Jim.

FWIW, I suspect that the flux density inside our solenoid
(cross-section radius *inside* the core) falls as the fourth
power of the distance from the windings, yes?

--Winston


Like most things in magnetics there's no simple answer. Wiki is
again of some help http://en.wikipedia.org/wiki/Solenoid and
http://en.wikipedia.org/wiki/Electromagnet but once again you
have to choose which particular combination of approximations is
appropriate.

For a very long air cored winding (i.e. a long solenoid) the
internal flux density varies little and is almost independent of
the distance from the winding wires.

With a short air cored winding there is a rapid radial variation
of flux density but this is drastically modified as soon as an
iron core is present. For typical working permeabilities of 2000+
the flux distribution is effectively short circuited leaving
little radial variation.

For working flux densities approaching true saturation the
permeability drops with some return of radial variation but the
amount is strongly dependent on the particular shape of the iron
B/H characteristics and the geometry of the iron circuit.


Thanks again, Jim.

--Winston

Does it come with a manual, in English, that Americans can understand?


----------------------

"Carl Ijames" wrote in message ...
MSC carries them in the US - www.mscdirect.com. Also seen on ebay, and
there may be other suppliers.

--