Saturday, September 01, 2012

new uses for old tv towers 2

Old television tower sections are low- or no- cost structural components that can be re-used for horizontal spans like this small footbridge that was made over a single weekend. The boards I used for the top and sides are salvaged 2x4's that otherwise would have been scrap.

(click any pic to enlarge it)

Many of the towers around here were made by the Delhi Metal Products company (now Wade Antenna), manufactured in Delhi, Ontario. Typical towers are bolted together of sections that are each 10 feet (300cm) in length. The top section is different and has the antenna mount platform. The sections are made of 18 ga. steel tubing with welded rungs. If they are in good condition, they are very strong, even if used sideways.

The galvanized zinc coating has probably mostly dissolved away in it's mission to protect the steel. Many of these old towers are standing un-used as we've switched, most of us, away from off-the-air TV.

I wanted a small footbridge across what we call here the "seasonal stream". The amount of water varies but at wettest is more than we can jump. It seemed a perfect place for a small bridge. Two or three of us can stand on it and it does not sag at all. Not unpleasant to look at and certainly functional.

The sections I used for this bridge had been sitting by the family cottage for years since being taken down. There were two of the regular sections and a top section. I took the top section to the metal scrap dump and took the other two home.

In a tall tower, you may have more sections. These towers with guy wires sometimes reached four or five sections. If still standing, towers are extremely dangerous to take down and if they are to be re-used, some care is required so that there is no damage. The bolts are rusty and the task is not fun if you have vertigo. There are people who do this sort of work and you probably should hire someone with insurance to do it.

Tower guys are also a good source of supply. For another project, a sun deck, I needed four tower sections and those came from a tower guy. He even let me pick very nice ones from his stock yard that matched.

With tower sections at hand my first step was to clean them with coarse steel wool and wet sand paper and examine them carefully, rung by rung to see if there was any damage. I wanted them strong. In my case, I had to have a couple rungs re-welded to the tubes as they had been broken loose.

I then moved the towers to the bridge site and primed, painted and let them dry in the sun while I thought about the foundations.

The foundations were simple. The tower legs rest on a patio "stone" of precast concrete, the pair cost about $10 and were the first of only three things I had to buy for the project. The rest of the material was recycled.

I did have some loose gravel and bedded the stones on about six inches. I also placed some loose real stones against the stream side to slow the erosion a bit. Three years later, that has held up fairly well. I will probably rework the foundations a bit. Maintenance is easy. With two people, one at each end, the bridge can simply be lifted off its foundations and moved aside.

Here is a view from underneath to help me explain the mounting system for the planks. With the Delhi towers with the round tubes, I used plastic clamps of the kind used to hold down plastic conduit. The planks don't actually get screwed to the tower but are captured by the clamps. This seemed easier than trying to drill into or through the tower tubes. I measured the diameter and then went looking for clamps to fit. I splurged on stainless steel screws to hold the clamps to the planks. The clamps and screws where another $15. I thought that the plastic clamps would be good underneath where they aren't so exposed to sunlight so even if they are not listed as UV safe, they should be fine. The plastic won't rust.

I realized at about this point that I would have to watch for rungs as I spaced out the planks since they might interfere with the clamps. So I did a mock up and laid the planks and slid them around. The clamps could go towards one edge of a plank if necessary yet still keep the plank tied to the tower. When I had an arrangement that seemed to work, I fastened the two end planks at both ends of the bridge with their clamps and worked inward toward the center.

I used a string attached to the two end planks and stretched it to form a guideline. You can see how that helped me in this view. Without the string, it would have been uneven at the edges.

I cut all planks in the shop on a crosscut saw set with a length stop. Working from a pile of salvaged 2x4s, I selected sections that were sturdy and cut them out of the scrap, all to the same length. Some had been painted, some not. Some pressure treated, some not. The best of the pile. The balance now was firewood. The pressure treated cuttings went to the landfill (I always keep PT separate), but so much less. Most of the scrap was used in the bridge.

The finishing touch is a strip of wood down each side fastened to each plank with a stainless steel screw. These tie the planks together so they don't move when you walk on them and also help define the edge. I had tried it before these were added and it just didn't seem as safe.

These strips are cut from the scrap 2x4s like the planks except in this case, the scrap wood is sawn lengthwise.

Probably I should add a kick board at the end and a yellow hazard strip? So the fox and coyotes can see it. They do use it. I see their trails over it in the snow.

This small footbridge has been weathering nicely here for three years. The most of the old paint has fallen off the recycled planks and the bridge is starting to look uniformly gray. It feels sturdy and safe to walk on. The old tower sections look like they will useful for at least the next 20 or 30 years or so.

Thanks for your interest!

To the first new uses for old TV towers

You may like another bridge project.


The Mayor said...

Very clever idea and careful detail. Thank you. I will copy for future reference if I don't make a windmill first. Cheers! Ron

Unknown said...

Know whete I can find a ower? John

George Plhak said...

John - try your yellow pages under "antenna tower" or check a local metals recycler.

Sea Biscuit said...

Nice work....Do think they would be strong enought to build a 6x8 fish hut on? Thanks in advance,

George Plhak said...

To spread the load on the ice? Not sure Kelly, probably. Worth a try. They are light. Depends on how heavy you build the hut?

Anonymous said...

Terrible waste of a good antenna tower.
You could have sold it as a tower and bought the materials need to make you bridge.