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 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 _________________ Topband Reflector Archives - http://www.contesting.com/_topband