But the dark-side is that a Crank-Up Tower suffers from 100% cable dependency.
If the cables hold, the tower stays up. If a failure happens the tower will drop in seconds, collapsing below the minimum height possible while rigged with cables.
Usually such a failure will write off the antennas, often the rotor and feed-lines and anything within the base of the tower is usually history.
Depending on the loading of the tower and side loads when it happens, the tower itself maybe damaged.
This danger is recognized by the “NO CLIMB” instructions and signage by Crank-Down tower manufacturers. Even when at their lowest, a cable failure would drop the tower a few feet more, and the pinch points would seriously injure a climber or even knock them off the tower after hurting them. As tempting as it may look, simply don’t do it – don’t ever climb a Crank-Up Tower.
Inspections go a long ways towards making sure your Crank-Up tower is as safe as it can be.
Inspection points include:
- Cable Condition – no rust, no cut strands, no kinks, no unraveled sections
- Cable Eyes and terminations (cable clamps are not recommended – the cables should be properly fitted with rigging grade swagged fittings at each end)
- Limit Switch Function (if fitted)
- Winch Condition
- Cable Routing and securement
- General Tower Condition, specially the pulleys & fittings for the Crank-Up portions.
If anything looks the least bit amiss, lower the tower to its lowest position if possible, and block the tower from further descent. Several 4x4s rigged for each section might be a good solution for safety blocking.
Once blocked, make the needed repairs before raising the tower again.
If you cannot safely lower the tower, have a lift brought in and block it in the raised position before making repairs from the lift.
Here is what can happen if a cable breaks (click on the picture for a larger version):
Pretty sad picture. In this case a large 40m-10m Yagi suffered damage to a number of elements and a high-end rotor was destroyed.
On the plus side, no one was hurt and it looks like the tower survived in a repairable state. Cables and Micro-switches will need to be replaced, but the main structure looks ok on inspection.
In the pictured case a section of cable suffered rapid deterioration and an isolated portion of that one cable gave way. Whether this was previously undiscovered lightening damage, some sort of galvanic reaction fallout or long-term cable decay missed in inspections, it isn’t certain. The rest of the cable set looks like new, but without scheduled FULL visual inspections the damage area was not caught, instead causing the fall.
As part of your station plans, you should include periodic inspections of major safety items like Crank-Up Tower cables. It should be right there with checking lightening protection gear, grounding, cable connector securement, antenna securement and all the other checks we need to make.
I’m looking at doing my major checks twice a year. A before-Winter major inspection and a mid-spring after-Winter major inspection. I’ve selected these times knowing that the Wisconsin climate does 80% of its weather damage in 20% of the months, deep winter.
You may be better served selecting dates around your QTH’s weather extremes.
Additionally I will include re-inspection each time the tower is in a position to make an easy inspection.
On the tower selection side I am told that one time some of the Crank-Up Tower manufacturers offered dual-cable options as a built-in safety option, but have not found any currently being offered.