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Posted by Boo on October 4, 2006, 8:06 pm
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Hi Chaps,
I want to make some "turnbuckle" style control rods for my RC toy aeroplanes but
I am stuck for a technique / tool for making them. For those who don't know,
the items I'm referring to are ally rods threaded at both ends, one end with a
rh thread, t'other with a lh thread. This means that when the rod is turned the
fittings screwed to either end move together or move apart. This saves having
to detach one of the fittings to adjust the linkage. Making these threads is
not the issue at all, I know how to do that.
The problem is I want them to be thicker in the middle than at the ends. But
they are pretty thin anyway (say 5mm in the centre, tapering to 3mm at the ends)
and they are around 200 mm long. This means that any attempt to taper turn them
is doomed because you can't use the normal travelling steady on a taper, and
they are so thin they'll just bend.
So my question is : Is there a taper turning mechanism that allows the tool to
move back while at the same time the steady moves in the opposite direction ?
(ie the tool and steady either move closer, or further apart).
I have vague ideas in my head about maybe having the steady and toolpost on the
same slide but each having oppisite handed nuts and the feedscrew being
comprised of two sections of lh and rh thread. This would give the motion I
require, provided this feedscrew could be driven at an adjustable proportion of
the lathes' main leadscrew rotation rate (so I can set the taper).
Anyway, I just wondered if there is a mechanism like this (maybe in an old ME
?), or if anyone has any ideas about it ?
Thanks,
Boo
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Posted by Tim Leech on October 5, 2006, 2:37 am
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On Thu, 05 Oct 2006 01:06:51 +0100, Boo
>Hi Chaps,
>
>I want to make some "turnbuckle" style control rods for my RC toy aeroplanes
but
>I am stuck for a technique / tool for making them. For those who don't know,
>the items I'm referring to are ally rods threaded at both ends, one end with a
>rh thread, t'other with a lh thread. This means that when the rod is turned
the
>fittings screwed to either end move together or move apart. This saves having
>to detach one of the fittings to adjust the linkage. Making these threads is
>not the issue at all, I know how to do that.
>
>The problem is I want them to be thicker in the middle than at the ends. But
>they are pretty thin anyway (say 5mm in the centre, tapering to 3mm at the
ends)
>and they are around 200 mm long. This means that any attempt to taper turn
them
>is doomed because you can't use the normal travelling steady on a taper, and
>they are so thin they'll just bend.
>
>So my question is : Is there a taper turning mechanism that allows the tool to
>move back while at the same time the steady moves in the opposite direction ?
>(ie the tool and steady either move closer, or further apart).
>
>I have vague ideas in my head about maybe having the steady and toolpost on the
>same slide but each having oppisite handed nuts and the feedscrew being
>comprised of two sections of lh and rh thread. This would give the motion I
>require, provided this feedscrew could be driven at an adjustable proportion
of
>the lathes' main leadscrew rotation rate (so I can set the taper).
>
>Anyway, I just wondered if there is a mechanism like this (maybe in an old ME
>?), or if anyone has any ideas about it ?
>
There is/was a turret tool made to do that sort of thing, though
whether it would be viable on thayt sort of length/diameter, I have no
idea.
I've got one somewhere, if I can lay my hands on it I'll post a pic.
It's incomplete in that anything like that will need linking to a
fixed point.
Tim
Dutton Dry-Dock
Traditional & Modern canal craft repairs
Vintage diesel engine service
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Posted by on October 5, 2006, 8:45 am
Please log in for more thread options
Boo wrote:
> The problem is I want them to be thicker in the middle than at the ends. But
> they are pretty thin anyway (say 5mm in the centre, tapering to 3mm at the
ends)
> and they are around 200 mm long. This means that any attempt to taper turn
them
> is doomed because you can't use the normal travelling steady on a taper, and
> they are so thin they'll just bend.
Use a Vastly Expensive and Complicated Machine to make them.
Or else find some cheap commercial product that already makes use of
similarly tapered stock, probably by using the aforementioned VEACM.
Butted bike spokes any use to you?
I imagine the commercial solution to this is a rolling mill.
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Posted by Dragon on October 5, 2006, 10:23 am
Please log in for more thread options Boo,
Save yourself the bother and use a carbon fibre tube instead.
Stiffer and lighter.
Haven't bought any lately but kite shops were a good source.
Cheers
Henry
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Posted by Mike on October 5, 2006, 10:34 am
Please log in for more thread options On Thu, 05 Oct 2006 01:06:51 +0100, Boo
>I want to make some "turnbuckle" style control rods for my RC toy aeroplanes
but
>I am stuck for a technique / tool for making them. For those who don't know,
>the items I'm referring to are ally rods threaded at both ends, one end with a
>rh thread, t'other with a lh thread. This means that when the rod is turned
the
>fittings screwed to either end move together or move apart. This saves having
>to detach one of the fittings to adjust the linkage. Making these threads is
>not the issue at all, I know how to do that.
>
>The problem is I want them to be thicker in the middle than at the ends. But
>they are pretty thin anyway (say 5mm in the centre, tapering to 3mm at the
ends)
>and they are around 200 mm long. This means that any attempt to taper turn
them
>is doomed because you can't use the normal travelling steady on a taper, and
>they are so thin they'll just bend.
>
>So my question is : Is there a taper turning mechanism that allows the tool to
>move back while at the same time the steady moves in the opposite direction ?
>(ie the tool and steady either move closer, or further apart).
>
>I have vague ideas in my head about maybe having the steady and toolpost on the
>same slide but each having oppisite handed nuts and the feedscrew being
>comprised of two sections of lh and rh thread. This would give the motion I
>require, provided this feedscrew could be driven at an adjustable proportion
of
>the lathes' main leadscrew rotation rate (so I can set the taper).
>
>Anyway, I just wondered if there is a mechanism like this (maybe in an old ME
>?), or if anyone has any ideas about it ?
Have you really, really, really got a requirement for this loss of
weight?
Assuming by "ally" you meant aluminium then assuming a density of
2.7g/cm3 and ignoring the weight loss due to the thread form, a plain
5mm diameter 200mm long rod weighs around 10.6 grams
Having a 10mm threaded section at each end and tapering the central
180mm from 5mm at the centre to 3mm results in a weight of around 6.6
grams, a difference of 4 grams per rod in exchange for what could be
tens of hours of machining for a full set of rods.
So, have you really, really, really got a requirement for this loss of
weight?
If so then take a 1mm dia aluminium rod former, glue on the 3mm
threaded ends and then wind a couple of mm thick of carbon tow soaked
in epoxy along the whole length of the 1mm section, overlapping the
threaded rod bond line. The overall volume will be less, stiffness
will be much higher and you will also get a significant weight
reduction, down to about 3.5 grams if I got my calculations right.
--
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>
>I want to make some "turnbuckle" style control rods for my RC toy aeroplanes