[TowerTalk] Rohn Torque Bar confusion

Tue Aug 3 18:41:53 EDT 2004

There is no argument that a 6 point guy is far superior to a 3 point
with or without torque arms.  Just look at the original geometry, the
torque arms can obviously not do anything until they are turned out of
line with the anchors, then the lever arm to resist the twist is only
the distance they have moved off the straight line, maybe only inches at
most.  The star guy starts out with double the number of guys and an arm
that is feet in length opposing the initial twist... now of course only
one of the two guys will be in play for either direction of rotation,
but the initial lever arm does most of the work anyway.

The original discussion was whether or not the torque arms did anything,
and the answer is obviously that yes they do.  They definitely are
better than just attaching the guy wire to the leg of the tower.  At
least as long as they are rigidly connected to the tower so they can't
move in the guy bracket.  Some older ones may not have a good fit and
require shims or washers to make a tight fit.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of Keith Dutson
> Sent: Tuesday, August 03, 2004 22:00
> To: TowerTalk
> Subject: RE: [TowerTalk] Rohn Torque Bar confusion
> 
> >but the farther away the attachment point is from the center of
rotation
> the bigger the angle on the guy wire so the higher the resistance to
the
> twist.
> 
> Here is some food for thought.  Take it to the extreme where the
torque
> arm
> is lengthened and rigidly attached to both the tower and guy anchor
point.
> Twisting the tower will result in bending the torque arm.
> 
> Now, reduce the length of the torque arm to one inch less than the
> distance
> from the tower and install a one inch guy wire.  Please don't laugh.
I
> know
> hardware alone would not allow such a condition, but this is just for
> visualization of force.  In this case the tower could twist a fraction
> without bending the arm.  Or could it?  Keep moving in to longer wire,
> shorter arm.  In each case the resistance to twisting is placed on
> rigidity/strength of the torque arm and tension/strength of the guy
wire.
> 
> IMO, if you compare the above to a six point torque arm system, well,
> there
> really is no comparison.
> 
> Keith
> 
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of David Robbins
K1TTT
> Sent: Tuesday, August 03, 2004 2:51 PM
> To: kr7x at comcast.net; 'Tower (K8RI)'; TowerTalk at contesting.com
> Subject: RE: [TowerTalk] Rohn Torque Bar confusion
> 
> 
> 
> 
> > When you translate the plane triangle section in rotation in its
> plane,
> > twist or torque load, initally the guys cannot resist the lateral
> > displacement as the guy's line of action is perpendicular to
theaction
> > direction of the load. As the triangular section twists additionally
> then
> > there is created an angle between the line of force and the guy line
> of
> > action which can develop a vector resistance to the movement of the
> > triangular section. This value of resistance is a function of the
sine
> of
> > the angle created.  It wil start at 0 degrees at rest, sine of 0
> degrees
> > is 0.
> >
> > This explains why the torsional resistance of the standard guying
> scheme
> > is so low and why if significant torsional forces are present in a
> tower
> > they twist.
> >
> > In this case the farther away from the center the guy attachment
point
> is
> > really doesn't help with the torsional strength the angle between
the
> guy
> > and the line of force of the torque is what matters.
> >
> 
> but the farther away the attachment point is from the center of
rotation
> the
> bigger the angle on the guy wire so the higher the resistance to the
> twist.
> Granted at 0 there is no force so it won't help with very small
movements
> but adding rigidly clamped arms that approximately double the radius
of
> rotation should increase the resistance proportionally.  Also
increasing
> the
> radius to where the reaction force is applied increases the length of
the
> arm applying the force also increasing the reaction torque applied by
the
> guy wires.
> 
> 
> David Robbins K1TTT
> e-mail: mailto:k1ttt at arrl.net
> web: http://www.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> 
> 
> _______________________________________________
> 
> See: http://www.mscomputer.com  for "Self Supporting Towers",
"Wireless
> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041
with
> any
> questions and ask for Sherman, W2FLA.
> 
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> 
> _______________________________________________
> 
> See: http://www.mscomputer.com  for "Self Supporting Towers",
"Wireless
> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041
with
> any questions and ask for Sherman, W2FLA.
> 
> _______________________________________________
> TowerTalk mailing list
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> http://lists.contesting.com/mailman/listinfo/towertalk