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Posted by Andrew Mawson on September 30, 2006, 4:17 am
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"Moray Cuthill cuthill_at_v21.me.uk>" <moray<dot> wrote in message
>>SNIP<<
>
> At the moment, I've got a rough idea of a plan in my head.
> Since the longest bend I need will only be about 180 degrees
(probably be
> less), I don't need to have above or below the rollers clear.
> This means I can build a sturdy frame (thinking 20/25mm plate for
end
> plates), ball or needle bearings for mounting the rollers (figure
these will
> offer less friction than a plain bearing under load), and then have
supports
> above/below the rollers with additional track roller bearings to
help
> prevent the rollers from bending.
> Power will either be elbow grease via quite a bit gearing (1st
choice),or
> I'll mount a hydraulic motor to do the donkey work (2nd option due
to the
> pain of having to borrow the motor and plumb it up)
>
>
> > Nothing impossible, just quite ambitious. If you could survive
less
> > accuracy
> > then a hearth, tongs, length of bar, striker and a hammer would do
the job
> > handily :-)
>
> Most of my projects are extremely ambitious!
> This project will be physically one of the smallest machines I'll of
built,
> but it's going to be one of the hardest in terms of the parts
required, and
> problems to be solved (bending the metal is going to be the easy
bit, it's
> what's to be done with it afterwards that's going to be hard)
> Unfortunately, accuracy is required for this particular. If radiuses
aren't
> accurate to within a millimetre, then the machine will most likely
not work.
>
I really wouldn't want to use roller or ball bearings for that sort of
crushing slow speed application. Plain bearings may give a small extra
amount of friction but at least they will take the huge sideways
force. The contact area of (particularly) ball races and rollers (to a
lesser extent) is very small.
AWEM
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Posted by Ben on September 29, 2006, 7:35 pm
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> Time to delurk for a while.
>
> For an upcoming project, it looks as though I'm going to need to acurately
> bend some 4 to 6 mm thick sheet (or should it be plate?) metal into
> partial cylinders (max cylinder will be about 270 degrees). The max width
> I'll need to form is 350mm, with diameters in the 5" to 8" range.
>
> I've been searching for slip roll plans, but have so far failed in finding
> anything suitable.
> So, it looks as though I'm going to have to design my own slip roll.
>
> The design I'm looking to build is one with two upper rollers that are
> geared together, with a lower adjustable roller for setting the formed
> diameter.
> But the question is, what kind of forces are involved, what material would
> be best of rollers, and most important, is this a suitable method for such
> thick metal?
>
> thanks
> moray
>Hi Moray,
I have a set of rolls which have 41/2" diam rollers six foot long, its
maximun bending thickness is .250 its electric motor is 5 hp and weighs
about 11/2 ton. How the hell your going to roll that plate by hand I dont
know.
Regards Ben
>
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Posted by David Littlewood on September 29, 2006, 7:57 pm
Please log in for more thread options >Time to delurk for a while.
>
>For an upcoming project, it looks as though I'm going to need to acurately
>bend some 4 to 6 mm thick sheet (or should it be plate?) metal into partial
>cylinders (max cylinder will be about 270 degrees). The max width I'll need
>to form is 350mm, with diameters in the 5" to 8" range.
>
>I've been searching for slip roll plans, but have so far failed in finding
>anything suitable.
>So, it looks as though I'm going to have to design my own slip roll.
>
>The design I'm looking to build is one with two upper rollers that are
>geared together, with a lower adjustable roller for setting the formed
>diameter.
>But the question is, what kind of forces are involved, what material would
>be best of rollers, and most important, is this a suitable method for such
>thick metal?
>
>thanks
>moray
>
The George Thomas book "The Model Engineer's Workshop Manual" has a
detailed description of the design and construction of a set of 3-roller
bending rolls, with a geared version optional. As usual with GHT, the
description is first rate, and there is a very useful discussion of the
principles involved. Thus, even if you find the design is not suitable,
the chapter is worth reading anyway. The ungeared version he built would
handle 10", and bent 1/2"x5/32" strip down to 14" radius, the geared
ones would have gone further.
Would be too small for you, but you should be able to scale up the
design, though your requirements are a little extreme for a piece of
"hobby workshop" equipment. Maybe some of the more large-scale
contributors will have some suggestions....
Best of luck.
David
--
David Littlewood
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Posted by M Cuthill on September 30, 2006, 4:28 pm
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> Time to delurk for a while.
>
> For an upcoming project, it looks as though I'm going to need to acurately
> bend some 4 to 6 mm thick sheet (or should it be plate?) metal into
> partial cylinders (max cylinder will be about 270 degrees). The max width
> I'll need to form is 350mm, with diameters in the 5" to 8" range.
>
> I've been searching for slip roll plans, but have so far failed in finding
> anything suitable.
> So, it looks as though I'm going to have to design my own slip roll.
>
> The design I'm looking to build is one with two upper rollers that are
> geared together, with a lower adjustable roller for setting the formed
> diameter.
> But the question is, what kind of forces are involved, what material would
> be best of rollers, and most important, is this a suitable method for such
> thick metal?
Thanks for the replies so far guys.
Sourcing tubing may be suitable for some parts, but given that things may
have to be tweaked quite a bit, and even possibly remade using slightly
altered dimensions, I'd rather build the equipment so I can shape what I
want.
Having now thought about the design of a suitable slip roll, I'll design it
around plain bearings, as it means less material has to be removed from the
end plates (a suitable ball bearing would be quite a bit larger in diameter
than a plain bearing), with end plates being 20mm thick with welded in wider
bosses to give the bearings a larger surface area.
Also, designing it around a hydraulic motor will most likely be the best way
forward, but with the option of sticking a handle on it.
As for the rollers, I'm thinking about 2 1/2" diameter, and made from a
hardenable steel. Thinking something like EN24, which has quite a bit of
strength, even when it's not hardened.
Does anybody have alink to suitable formulas/figures for working out the
bending forces involved, or at least suitable google sugestions?
And for the poster who mentioned my ideas are not quite 'home hobbyist'
size, they're quite right. I like to think of it more as professional
hobbyist, due to the fact quite a large chunk of the stuff I build just now
is built to work, even though I don't make any money out what the work done.
I just get the joys/headaches of designing and building stuff, and going
further into the negative availability of workshop space!
--
Posted via a free Usenet account from http://www.teranews.com
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Posted by Jonathan Barnes on October 1, 2006, 7:15 am
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>
> > Time to delurk for a while.
> >
> > For an upcoming project, it looks as though I'm going to need to
acurately
> > bend some 4 to 6 mm thick sheet (or should it be plate?) metal into
> > partial cylinders (max cylinder will be about 270 degrees). The max
width
> > I'll need to form is 350mm, with diameters in the 5" to 8" range.
> >
> > I've been searching for slip roll plans, but have so far failed in
finding
> > anything suitable.
> > So, it looks as though I'm going to have to design my own slip roll.
> >
> > The design I'm looking to build is one with two upper rollers that are
> > geared together, with a lower adjustable roller for setting the formed
> > diameter.
> > But the question is, what kind of forces are involved, what material
would
> > be best of rollers, and most important, is this a suitable method for
such
> > thick metal?
>
> Thanks for the replies so far guys.
>
> Sourcing tubing may be suitable for some parts, but given that things may
> have to be tweaked quite a bit, and even possibly remade using slightly
> altered dimensions, I'd rather build the equipment so I can shape what I
> want.
>
> Having now thought about the design of a suitable slip roll, I'll design
it
> around plain bearings, as it means less material has to be removed from
the
> end plates (a suitable ball bearing would be quite a bit larger in
diameter
> than a plain bearing), with end plates being 20mm thick with welded in
wider
> bosses to give the bearings a larger surface area.
> Also, designing it around a hydraulic motor will most likely be the best
way
> forward, but with the option of sticking a handle on it.
> As for the rollers, I'm thinking about 2 1/2" diameter, and made from a
> hardenable steel. Thinking something like EN24, which has quite a bit of
> strength, even when it's not hardened.
>
> Does anybody have alink to suitable formulas/figures for working out the
> bending forces involved, or at least suitable google sugestions?
****
Probably modeling the plate as a beam with two supports and a centre load
will give an idea of the force required..
Needs plate cross section, length between bottom rolls ( alow for contact
point moveing in as radius is rolled ) and yeild stress of the steel.
You might need to calculate the flex of your rollers..... the forces
involved might bend the rollers to much..
What is your minimum radius.?
My " toy " formit metal bender rolls 1.5mm, and has 15?mm end plates. your
force requirement probably increases with the forth power of thickness so
your end plates may need to be a lot thicker than the 25mm you suggested.
I think you need to find a freindly boiler maker to do this work on a sub
contract basis..
****
>
> And for the poster who mentioned my ideas are not quite 'home hobbyist'
> size, they're quite right. I like to think of it more as professional
> hobbyist, due to the fact quite a large chunk of the stuff I build just
now
> is built to work, even though I don't make any money out what the work
done.
> I just get the joys/headaches of designing and building stuff, and going
> further into the negative availability of workshop space!
>
>
>
> --
> Posted via a free Usenet account from http://www.teranews.com
>
Regards Jonathan
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