Snipe on a Tower

There is a limited ability to achieving mechanical leverage when you are working on a tower. You can only "push" against the tower, directly or via your positioning lanyards. As I like to say: an ordinary task on a tower is three times as difficult as it is on the ground.

A good example is one I wrote about several months ago: adjusting the direction of a large yagi. I had to rig my positioning gear to maximize how far I could lean out from the tower to plant my legs and pull on the boom or driven element to overcome the antenna's inertia. Then I had to do it again to stop the rotation. There's a lot of angular momentum in a 300 lb antenna with a 46' boom and 65' long elements!

There are many other examples in tower work. The most common is tightening and loosening the bolts that hold a tower together. On large towers those bolts have a wide diameter and high tensile strength. The required torque can be difficult to achieve on the ground, let alone at the top of the tower you're erecting or taking down.

The bolts in the above picture are examples of what I've dealt with recently. On the left is a ½" grade 8 bolt used to join the horizontal flanges of mated tower section (see the picture below right). Unlike the typical round or V-shaped tower legs familiar to hams, you'll find that many commercial towers are built this way. They're far easier to work with when the tower sections are long, wide and very heavy. On the right is a galvanized ⅝" A325 bolt that is designed for the high shear forces found in V- or L-shaped tower legs.

The specified torque for these bolts is high. Achieving a torque of 100 ft-lb or more is no easy feat when you're on a tower. It can take even more force to loosen fasteners that have corroded or attracted dirt over the years. On the left bolt you can see what was lurking under the nuts.

For the tower I was taking down, those ½" grade 8 bolts had been properly torqued when it was erected years ago. Each section joint has 6 bolts, with two per flange on 3 legs, and there were 5 of these 11' sections. 

Pulling hard on my long ¾" wrench wasn't good enough to loosen the nuts. The nuts either didn't budge or, in a few cases, the bolt and nut moved in unison. I needed more torque.

Since it took longer than expected to remove the antennas and cables, tower removal was deferred to a later date. That gave me time to fashion a solution. In essence, I needed a longer lever arm to increase the torque at the wrench head. 

There are "breaker bars" made for this very purpose but they're heavy and expensive, and if you're a typical ham you probably won't get much use out of it. Also, they usually take sockets and that can make it difficult to firmly hold the nut because you apply force to the tool arm that is necessarily offset from the work surface by up to 2".

The traditional way it's done is to slip a steel pipe over the wrench and use that for added leverage. It's simple, easy and works well when the wrench is forged steel and designed to take the abuse. My ¾" offset box wrench is very robust (40 years of reliable service!). However, it is extremely awkward to manipulate a large pipe slipped over it when perched on a tower. You'll inevitably drop the wrench, pipe or both. Ask me how I know!

A common name for a pipe used in this way is a snipe. It's a term that seems to vary by country and industry, so you may know it by a different name. I'll stick with the term I know.

Note about safety. Careless use of a snipe can destroy the fastener or the tool. If you find that you're applying far more torque than the job should require, stop immediately. The problem may not be simply the lack of torque. Inspect the fastener for signs of rust, debris, metal distortion and other anomalies. Shearing a tower bolt, if it's the last one holding the sections together, invites disaster. The shrapnel from a shattered wrench or snipe can easily injure you and the debris can strike those on the ground. Hardhats and eye protection are recommended.

When we returned several days later to take down the tower I brought along the snipe I purposely built for the job. I keep a lot of scrap material around for reasons just like this. Here's what I whipped together after 30 minutes in my workshop.

The wrench has two box ends. The 25/32" end is inside the pipe and held in place by a ⅜" grade 5 bolt. The wrench cannot slip out of the pipe. To keep the weight low I used a short length of thin wall 1.5" diameter pipe. It looks like it was once part of a mast for a TV antenna. There's a PVC coupler jammed into one end that I remember once trying and failing to remove. So I drilled a hole through it and tied on a short length of rope. On the other end of the rope is a large spring-loaded carabiner. A length of stranded wire is less flexible but you may find it more reliable than rope. Don't use solid wire since it can fatigue and break.

Because the pipe wall is thin, the edge of the wrench can bend and perhaps break the pipe under high torque. A rusty muffler clamp strengthens this high stress point. The snipe is far lighter than one made from a thick wall pipe. The carabiner clips to a ring on my climbing gear or onto a tower strut. You would have to be exceptionally clumsy to drop this tool.

Notice that the total length is only about twice that of the wrench along. As a general rule, use the shortest snipe that accomplishes what's required. There's less risk of accidents due to application of excess force. With the tool as constructed you can likely achieve more than twice the torque of the wrench alone because the round pipe is more comfortable in the hand than the wrench narrow side profile. Breaker bars are round but are comparatively thin.

The purpose of the snipe is to "crack" the nut, not to remove it. For properly torqued bolts of this size and quality there is a satisfying crack when the nut first moves. You can probably set the snipe aside at that point and use ordinary and less awkward wrenches. 

If the bolt turns, have your tower partner put a wrench on the bolt head to hold it. You typically need less torque to hold the bolt head than to turn the nut due to friction between the tower steel and the bolt head. The snipe should always be applied to the nut, not the bolt head. We passed the snipe back and forth depending on which of us was best positioned to crack each nut.

When all the nuts are cracked, proceed with fastener removal and lowering the tower section. The snipe was clipped onto the lower section while we did this. Pick a place that won't interfere with the delicate job of shifting and lowering the tower section with the gin pole.

This little snipe worked so well that after removing the carabiner and wrench I kept it intact. I don't know when or if I'll use it again but I'd like to have it ready just in case.