Re: Topband: Fwd: cable clamps on old Phillystran
Hi Grant and Carl, About 20 years ago, I replaced my steel guy wires on my 80 ft of Rohn 45G with 6700lb Phillystran. At that time the end kits were 4 galvanized cable clamps and a plastic end cap. Their instructions said to torque the cable clamps to 25 ft/lbs. I also used RTV on the end caps. I have had no problem and the installation has been through winds over 80 mph. The Phillystrand did improve my shunt feed performance on 160. I did have to re-tune my Omega Match. I also use 1200 lb Phillystran for the overhead guy on my Telrex 20M456 73 Price W0RI near St. Louis On Thursday, May 29, 2014 10:44 PM, Grant Saviers gran...@pacbell.net wrote: Ice is an interesting question. I'll speculate that it doesn't matter much since the sheath is pretty flexible and the Kevlar has a small sensitivity to moisture. The Kevlar demonstrated very high crush strength, I think about the same as its tensile strength, so to me that is not a concern. However, if the sheath is degraded to expose Kevlar to UV then it is a whole different ballgame. I also think it takes a bit of faith that the factory recommended plastic endcaps on current production Philly keep all moisture out. Grant KZ1W On 5/29/2014 7:45 AM, Carl wrote: What about ice forming inside the sheath from those breaks? Carl KM1H - Original Message - From: Tree t...@kkn.net To: 160 topband@contesting.com Sent: Thursday, May 29, 2014 9:48 AM Subject: Topband: Fwd: cable clamps on old Phillystran Forwarding from KZ1W: -- Forwarded message -- From: Grant Saviers gran...@pacbell.net Date: Wed, May 28, 2014 at 9:56 PM Subject: cable clamps on old Phillystran To: topband@contesting.com Cc: t...@kkn.net Per prior topband posts and discussions about this topic, I've concluded a round of testing of cable clamps on parallel strand (old style) Phillystran. Here is the Conclusions and Summary I wrote: A hydraulic jack H frame press was modified to provide tension in excess of 20,000 lbs. Tension was applied to a 4 foot long 5/8” od parallel strand (old) Phillystran cable terminated with four 5/8” cable clamps and ¾” thimbles at both ends. Clamp nuts were torqued to specific values and the holding capacity of the cable assembly was measured over periods of weeks. There is significant creep of the plastic sheath from the cable clamp forces between the clamp and the Kevlar core. In the first test sequence, the residual torque of the clamp nuts reduced by 65% in 21 days. Subsequent tightening of the clamp nuts showed smaller sequential reductions of residual torques. Five cycles of tightening were demonstrated as necessary over a period of weeks to achieve sufficient residual torque of the clamp nuts. A conclusion at 66 days since initial assembly was that four 5/8” wire rope clamps, torqued in 5 cycles over weeks to a 50 ft-lb value, will support a long term tension without significant slippage at the desired holding strength of 6600 lbs, about 25% of the cable rated strength. After removal of the cable sheath, there was no visible damage to the Kevlar core at the clamps or at the thimble. It is speculated that a slightly higher torque value than 50 ft-lbs would improve the slip strength. Adding a 5th clamp would further improve the slip strength. The core around the thimble showed evidence of small differential slippage of fibers. The test sequence was such that the fibers could slip against each other as tension and clamp nut torques were increased sequentially. Thus, the test process was not the same as tightening the clamps and then installing the guy. However, the Phillystran tested is to be used at 25% of its rated strength, so the risk seems minimal in this case. Note that wire rope is expected to hold at least 80% of rated strength when properly terminated with cable clamps, and is not sequentially pre-tensioned when put into service. Whatever unequal forces exist in the individual wire strands around the thimble are equalized in some manner. From this testing, it seems unlikely that parallel strand Phillystran can be reliably terminated with cable clamps at more than 1/3 of rated breaking strength. The simplified conclusion is that the cable will slip unless the clamp has extruded out most of the plastic sheath in the clamping area. The planned tower has maximum pretension in the guys of 600 lbs. Thus, the average long term tension is substantially below the measured slip value produced in these tests, so it seems unlikely that the preload tension will cause slip over a period of years. Since the plastic sheath was breached by at least one clamp, water will intrude into the core. Moisture does slightly reduce the strength of the Kevlar fiber. The clamp fully covers the split area so degradation from sunlight seems unlikely, although UV degradation is a major concern
Re: Topband: Fwd: cable clamps on old Phillystran
The only damage on my Yagi antennas from the ice storm we had (about an inch of radial ice) was to Philliystran struts. In every case the jacket held in place under the clamps but the strand inside moved. Now I have to rent a crane with man basket to repair the struts. The end attachment with three clamps is obviously not a good system. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Fwd: cable clamps on old Phillystran
Just a thought, but has anyone checked to see if there is a dead-end / preform type of grip that will work on the older style phillystran cable? That might make a better connection than the clamps and thimble setup. -Bill -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Friday, May 30, 2014 3:40 PM To: HAROLD SMITH JR; Grant Saviers; 160 Subject: Re: Topband: Fwd: cable clamps on old Phillystran The only damage on my Yagi antennas from the ice storm we had (about an inch of radial ice) was to Philliystran struts. In every case the jacket held in place under the clamps but the strand inside moved. Now I have to rent a crane with man basket to repair the struts. The end attachment with three clamps is obviously not a good system. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Fwd: cable clamps on old Phillystran
What about ice forming inside the sheath from those breaks? Carl KM1H - Original Message - From: Tree t...@kkn.net To: 160 topband@contesting.com Sent: Thursday, May 29, 2014 9:48 AM Subject: Topband: Fwd: cable clamps on old Phillystran Forwarding from KZ1W: -- Forwarded message -- From: Grant Saviers gran...@pacbell.net Date: Wed, May 28, 2014 at 9:56 PM Subject: cable clamps on old Phillystran To: topband@contesting.com Cc: t...@kkn.net Per prior topband posts and discussions about this topic, I've concluded a round of testing of cable clamps on parallel strand (old style) Phillystran. Here is the Conclusions and Summary I wrote: A hydraulic jack H frame press was modified to provide tension in excess of 20,000 lbs. Tension was applied to a 4 foot long 5/8” od parallel strand (old) Phillystran cable terminated with four 5/8” cable clamps and ¾” thimbles at both ends. Clamp nuts were torqued to specific values and the holding capacity of the cable assembly was measured over periods of weeks. There is significant creep of the plastic sheath from the cable clamp forces between the clamp and the Kevlar core. In the first test sequence, the residual torque of the clamp nuts reduced by 65% in 21 days. Subsequent tightening of the clamp nuts showed smaller sequential reductions of residual torques. Five cycles of tightening were demonstrated as necessary over a period of weeks to achieve sufficient residual torque of the clamp nuts. A conclusion at 66 days since initial assembly was that four 5/8” wire rope clamps, torqued in 5 cycles over weeks to a 50 ft-lb value, will support a long term tension without significant slippage at the desired holding strength of 6600 lbs, about 25% of the cable rated strength. After removal of the cable sheath, there was no visible damage to the Kevlar core at the clamps or at the thimble. It is speculated that a slightly higher torque value than 50 ft-lbs would improve the slip strength. Adding a 5th clamp would further improve the slip strength. The core around the thimble showed evidence of small differential slippage of fibers. The test sequence was such that the fibers could slip against each other as tension and clamp nut torques were increased sequentially. Thus, the test process was not the same as tightening the clamps and then installing the guy. However, the Phillystran tested is to be used at 25% of its rated strength, so the risk seems minimal in this case. Note that wire rope is expected to hold at least 80% of rated strength when properly terminated with cable clamps, and is not sequentially pre-tensioned when put into service. Whatever unequal forces exist in the individual wire strands around the thimble are equalized in some manner. From this testing, it seems unlikely that parallel strand Phillystran can be reliably terminated with cable clamps at more than 1/3 of rated breaking strength. The simplified conclusion is that the cable will slip unless the clamp has extruded out most of the plastic sheath in the clamping area. The planned tower has maximum pretension in the guys of 600 lbs. Thus, the average long term tension is substantially below the measured slip value produced in these tests, so it seems unlikely that the preload tension will cause slip over a period of years. Since the plastic sheath was breached by at least one clamp, water will intrude into the core. Moisture does slightly reduce the strength of the Kevlar fiber. The clamp fully covers the split area so degradation from sunlight seems unlikely, although UV degradation is a major concern with Kevlar. Although the tests were successful in achieving a stable termination at 6600 lb tension, doubts remain in my mind about the long term reliability of using cable clamps. Hence, I plan to assemble and test a Phillystran cable terminated with the standard Crosby Spelter sockets for 5/8” wire rope using epoxy potting. A pdf of the full report is available, contact me offline for a copy. Grant KZ1W _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Fwd: cable clamps on old Phillystran
Well, to put it as it affected me as I read it, that's enough to give me the willies. While some might have read that as a victory of sorts, a successful test of a non-factory method, the very idea of 5 torquings, or that one can only use 1/3 of the rated strength of the line, is way more than enough to stifle me from ever considering using it. Particularly, the pretension stresses are not really the deal breaker, it's what happens when you get an hour or two of near hurricane winds, or actual hurricane winds, or a really nasty derecho wind, with its shearing pulse winds. We'll throw in the towel with tornados. Back in the day W4BVV lost his 150' 40 meter tower (and the huge 70' boom, full size element yagi on top of it) when STEEL cable pulled through triple cable clamps. As a result, I've never felt good about clamps on anything big. He later did something complex with a folded back end that was woven and clamped, forcing a failure force to unbend the fold AND unbend it with the fold clamped down, before pulling it through the main clamps. So far as I know those were still working fine when they came down on the way to re-erection at W3LPL. These days we have the wraps, and the right size, new, never come off. Yup, stick to the factory method. Guy systems are one place where cheep makes no sense at all. Chopping up mangled tower plus mangled beams is very discouraging. And whatever political viewpoints one might have on climate change, winds are gradually creeping up both in velocity and frequency. It's no fun at all beating the loyal contest opposition because some of his antennas are in a heap on the ground. 73, Guy. On Thu, May 29, 2014 at 9:48 AM, Tree t...@kkn.net wrote: Forwarding from KZ1W: -- Forwarded message -- From: Grant Saviers gran...@pacbell.net Date: Wed, May 28, 2014 at 9:56 PM Subject: cable clamps on old Phillystran To: topband@contesting.com Cc: t...@kkn.net Per prior topband posts and discussions about this topic, I've concluded a round of testing of cable clamps on parallel strand (old style) Phillystran. Here is the Conclusions and Summary I wrote: A hydraulic jack H frame press was modified to provide tension in excess of 20,000 lbs. Tension was applied to a 4 foot long 5/8” od parallel strand (old) Phillystran cable terminated with four 5/8” cable clamps and ¾” thimbles at both ends. Clamp nuts were torqued to specific values and the holding capacity of the cable assembly was measured over periods of weeks. There is significant creep of the plastic sheath from the cable clamp forces between the clamp and the Kevlar core. In the first test sequence, the residual torque of the clamp nuts reduced by 65% in 21 days. Subsequent tightening of the clamp nuts showed smaller sequential reductions of residual torques. Five cycles of tightening were demonstrated as necessary over a period of weeks to achieve sufficient residual torque of the clamp nuts. A conclusion at 66 days since initial assembly was that four 5/8” wire rope clamps, torqued in 5 cycles over weeks to a 50 ft-lb value, will support a long term tension without significant slippage at the desired holding strength of 6600 lbs, about 25% of the cable rated strength. After removal of the cable sheath, there was no visible damage to the Kevlar core at the clamps or at the thimble. It is speculated that a slightly higher torque value than 50 ft-lbs would improve the slip strength. Adding a 5th clamp would further improve the slip strength. The core around the thimble showed evidence of small differential slippage of fibers. The test sequence was such that the fibers could slip against each other as tension and clamp nut torques were increased sequentially. Thus, the test process was not the same as tightening the clamps and then installing the guy. However, the Phillystran tested is to be used at 25% of its rated strength, so the risk seems minimal in this case. Note that wire rope is expected to hold at least 80% of rated strength when properly terminated with cable clamps, and is not sequentially pre-tensioned when put into service. Whatever unequal forces exist in the individual wire strands around the thimble are equalized in some manner. From this testing, it seems unlikely that parallel strand Phillystran can be reliably terminated with cable clamps at more than 1/3 of rated breaking strength. The simplified conclusion is that the cable will slip unless the clamp has extruded out most of the plastic sheath in the clamping area. The planned tower has maximum pretension in the guys of 600 lbs. Thus, the average long term tension is substantially below the measured slip value produced in these tests, so it seems unlikely that the preload tension will cause slip over a period of years. Since the plastic sheath was breached by at least one clamp, water will intrude into the core. Moisture does slightly reduce the strength
Re: Topband: Fwd: cable clamps on old Phillystran
Ice is an interesting question. I'll speculate that it doesn't matter much since the sheath is pretty flexible and the Kevlar has a small sensitivity to moisture. The Kevlar demonstrated very high crush strength, I think about the same as its tensile strength, so to me that is not a concern. However, if the sheath is degraded to expose Kevlar to UV then it is a whole different ballgame. I also think it takes a bit of faith that the factory recommended plastic endcaps on current production Philly keep all moisture out. Grant KZ1W On 5/29/2014 7:45 AM, Carl wrote: What about ice forming inside the sheath from those breaks? Carl KM1H - Original Message - From: Tree t...@kkn.net To: 160 topband@contesting.com Sent: Thursday, May 29, 2014 9:48 AM Subject: Topband: Fwd: cable clamps on old Phillystran Forwarding from KZ1W: -- Forwarded message -- From: Grant Saviers gran...@pacbell.net Date: Wed, May 28, 2014 at 9:56 PM Subject: cable clamps on old Phillystran To: topband@contesting.com Cc: t...@kkn.net Per prior topband posts and discussions about this topic, I've concluded a round of testing of cable clamps on parallel strand (old style) Phillystran. Here is the Conclusions and Summary I wrote: A hydraulic jack H frame press was modified to provide tension in excess of 20,000 lbs. Tension was applied to a 4 foot long 5/8” od parallel strand (old) Phillystran cable terminated with four 5/8” cable clamps and ¾” thimbles at both ends. Clamp nuts were torqued to specific values and the holding capacity of the cable assembly was measured over periods of weeks. There is significant creep of the plastic sheath from the cable clamp forces between the clamp and the Kevlar core. In the first test sequence, the residual torque of the clamp nuts reduced by 65% in 21 days. Subsequent tightening of the clamp nuts showed smaller sequential reductions of residual torques. Five cycles of tightening were demonstrated as necessary over a period of weeks to achieve sufficient residual torque of the clamp nuts. A conclusion at 66 days since initial assembly was that four 5/8” wire rope clamps, torqued in 5 cycles over weeks to a 50 ft-lb value, will support a long term tension without significant slippage at the desired holding strength of 6600 lbs, about 25% of the cable rated strength. After removal of the cable sheath, there was no visible damage to the Kevlar core at the clamps or at the thimble. It is speculated that a slightly higher torque value than 50 ft-lbs would improve the slip strength. Adding a 5th clamp would further improve the slip strength. The core around the thimble showed evidence of small differential slippage of fibers. The test sequence was such that the fibers could slip against each other as tension and clamp nut torques were increased sequentially. Thus, the test process was not the same as tightening the clamps and then installing the guy. However, the Phillystran tested is to be used at 25% of its rated strength, so the risk seems minimal in this case. Note that wire rope is expected to hold at least 80% of rated strength when properly terminated with cable clamps, and is not sequentially pre-tensioned when put into service. Whatever unequal forces exist in the individual wire strands around the thimble are equalized in some manner. From this testing, it seems unlikely that parallel strand Phillystran can be reliably terminated with cable clamps at more than 1/3 of rated breaking strength. The simplified conclusion is that the cable will slip unless the clamp has extruded out most of the plastic sheath in the clamping area. The planned tower has maximum pretension in the guys of 600 lbs. Thus, the average long term tension is substantially below the measured slip value produced in these tests, so it seems unlikely that the preload tension will cause slip over a period of years. Since the plastic sheath was breached by at least one clamp, water will intrude into the core. Moisture does slightly reduce the strength of the Kevlar fiber. The clamp fully covers the split area so degradation from sunlight seems unlikely, although UV degradation is a major concern with Kevlar. Although the tests were successful in achieving a stable termination at 6600 lb tension, doubts remain in my mind about the long term reliability of using cable clamps. Hence, I plan to assemble and test a Phillystran cable terminated with the standard Crosby Spelter sockets for 5/8” wire rope using epoxy potting. A pdf of the full report is available, contact me offline for a copy. Grant KZ1W _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
