Topic: Anemometer mounting: galvanized water pipe vs galvanized chain-link fence rail

[Ladd]

I'm looking to attach my new VP2 anemometer to a 10-foot pole which will be attached to the side of my garage with heavy duty three-leg antenna mounts (max pole size capable 1.5"), reaching 7 feet above the top of the roof. Hoping to not use guy wires on the pole.

I've looked at 1" galvanized water pipe (outside diameter = 1.32") and it seems very rigid. Haven't yet looked at galvanized chain-link fence rail (outside diameter = 1 3/8" (1.375"). I doubt the fence rail would be as rigid as the water pipe, but it might be rigid enough for anemometer use. It is certainly lighter in weight (8.1 lbs vs 16.8 lbs).

I don't know how much a pole will weigh when the anemometer and cable is mounted.

I guess the two criteria that are most important are sufficient rigidity for anemometer use and ability to lift the pole out of the loosened clamps and lower it to the rooftop in a controlled manner when maintenance/inspection is required.

General wisdom and opinions requested one which pole to use.

[MesquiteWx]

IMO for what you're looking for I would probably look at conduit as it is lightweight and rigid and would fit the anemometer nicely.

[Ladd]

IMO for what you're looking for I would probably look at conduit as it is lightweight and rigid and would fit the anemometer nicely.

Nice suggestion; it's certainly less expensive than the two options I thought I had. I'll check it out when I go to Home Depot later today. With no actual knowledge on the subject of conduit, I don't know if a 10 foot length of 1.25" conduit weighing less than one pound will be rigid enough to withstand the pressure of a good wind against an anemometer, but I'll take a look.

[CNYWeather]

I have a 10' galvanized chain link fence pole on mine. I bolted it to a tripod mount. Been up there for almost 6 years now without any issues.
In really strong winds it has a slight shake but nothing really bad.

[Ladd]

I have a 10' galvanized chain link fence pole on mine. I bolted it to a tripod mount. Been up there for almost 6 years now without any issues.

Any type of cap on the top to keep rain out of the inside of the pipe?

[dalecoy]

What is most important?  (Size, weight, or rigidity?)

Conduit of a particular size is less rigid than the same size pipe.  Larger diameter tends to be more rigid than smaller diameter.  Etc.

[Ladd]

What is most important?  (Size, weight, or rigidity?)

Conduit of a particular size is less rigid than the same size pipe.  Larger diameter tends to be more rigid than smaller diameter.  Etc.

It's my understanding that the pole an anemometer will be mounted on should be "reasonably" rigid. I'm guessing that the 1" water pipe would be the most rigid, with the chain-link fence railing somewhat less rigid and the 1.25" conduit possibly the least rigid.

I will be mounting the pipe on a three foot vertical wall where the top of the front lower roof (low pitch) meets the top of the back  upper roof (steeper pitch).

Kind of like this side view, albeit a slight pitch (left = lower) on the lower roof  and less pitch on the upper roof:

         |\
         |   \
         |      \
_____| 

My theory on taking the pole down is to loosen the bolts on the two U-brackets , lift the pipe straight up several feet, set the bottom of the pipe down on the roof then walk the pipe down to horizontal position taking care to not damage the anemometer.

So, I don't think the heavy duty 1" water pipe (16 lbs + anemometer) would be too difficult to dismount, I'm sure the chain link rail pipe (8 lbs) would not be difficult at all and the conduit may not be rigid enough for operating use. I have to go to Home Depot and see and touch the pipes to get a feel for weight and rigidity, but always a good idea to ask other people's opinions.

[CNYWeather]

I have a 10' galvanized chain link fence pole on mine. I bolted it to a tripod mount. Been up there for almost 6 years now without any issues.

Any type of cap on the top to keep rain out of the inside of the pipe?

I put electrical tape over the top of it to cap it.

[W3DRM]

It's the wall thickness of the pipe that makes each type more or less rigid with the water pipe probably the more rigid of the three being mentioned. I would not consider the conduit as it is not designed to be self-standing and most likely would eventually fail in a high wind gust.

Another alternative - antenna mast: RadioShack and Home Depot used to carry 10' sections that were 1-1/2" in diameter and are excellent for what you are trying to do. I have three 10' sections of antenna mast that I use for my VP2 anemometer but, due to the height, I have two guy wires holding it steady. I use the 3/16" nylon or rayon cord as the guy wire. It lasts forever even with constant sun exposure.

As for covering the end of the mast, I simply find a pvc end cap of appropriate size and place it on both ends to keep out the rain and critters (spiders love an open pipe).

[MesquiteWx]

I would not consider the conduit as it is not designed to be self-standing and most likely would eventually fail in a high wind gust.

Conduit is rather rigid, will it flex some under wind, yes a little but in the manner the OP plans to strap it it shouldn't flex to much if very little. It is more rigid that antenna mast sections and thicker. Antenna masts are very thin walled and light. You wan't it to have some give otherwise it will rip away from the straps. With the conduit you have less surface area to create drag compared to a larger dia pipe so it can handle more of a wind load. Even the mast kits they sell at Ambient for the Davis stations flex some in the wind with guy lines. You won't some flex to keep the strain off the strap. It is just line your amateur radio antennas on a tower. They have a wind load rating because they create drag. Less drag, higher wind load rating it can handle.

I think you would be fine with it. Just go look at your options for what would work for you which you think would be easier to take down if need be and how much of a hassle it would be to strap it safely.

[moehoward4]

1¼" ID EMT conduit from HD or Lowes.....one piece has been out there for 18+ years, another one for 7½ years....LOTS of wind been blown on both with no issues.

[dalecoy]

It's the wall thickness of the pipe that makes each type more or less rigid ...

Too simplistic.  It's also the diameter of the pipe...  (If you had a 12-inch diameter pipe and a 1/4 inch diameter pipe with the same wall thickness, the larger pipe would be more rigid).

...and, of course the material (paper vs copper vs steel?)

...and even with steel, there are different heat treatments for different uses that affect the rigidity/stiffness.

Ladd is taking the right approach - ask for info, and then go inspect/choose.  Let's see what he chooses.

And, with regard to capping the pipe - if the bottom is open, there's no reason to cap the top.  (i.e., eave mount).  But if it's buried in the ground, then a cap is important.

[Ladd]

1¼" ID EMT conduit from HD or Lowes.....one piece has been out there for 18+ years, another one for 7½ years....LOTS of wind been blown on both with no issues.

Just got back from HD and after flex testing all three 10-foot pipes (1.25" I.D. galvanized water pipe, 1.375 O.D. galvanized chain-link rail pipe and aluminum 1.25" EMT conduit), I purchased the conduit. It had way less flex than the chain-link rail and slightly more flex than the 1.25" water pipe, but was half the price of the water pipe and 1/16th the weight.

I wouldn't be surprised that there may be only a slight correlation between resistance to flexing and outright failure due to high wind loads, but I'm comfortable with my selection and we'll see what happens.

Looks like it might go above freezing tomorrow where I live, so hopefully I'll be able to get the anemometer/wind vane up and running.

Thanks for everyone's opinions and help.

Ladd

[Ladd]

And, with regard to capping the pipe - if the bottom is open, there's no reason to cap the top.  (i.e., eave mount).  But if it's buried in the ground, then a cap is important.

Good to know that I don't need to cap top and bottom of the pipe. Of course, with talking to a sales person in HD, once I learned that the conduit I was looking at was aluminum, I wasn't worried about capping it at all.

Hopefully there won't be any reaction between the steel mounting U-bolt and the aluminum ...

[Garth Bock]

If you use galvanized pipe don't forget to put Teflon tape between the second. When I went to raise my station for better wind exposure I found the sections rusted together. Also to eliminate the "pendulum" or sway you might want to split the ane from the ISS. Put the ane at the top and leave the rest of the ISS farther down the pole. Less wind loading and sway from the full ISS being at the top.

[Ladd]

I'm only using one 10-foot length of aluminum conduit, so no threads to tape. I'll be using the wireless transmitter on the anemometer/wind vane (located down near ground level), so the ISS can be in another part of the yard (final resting place to be determined).

[dalecoy]

... aluminum 1.25" EMT conduit), I purchased the conduit. It had way less flex than the chain-link rail and slightly more flex than the 1.25" water pipe, but was half the price of the water pipe and 1/16th the weight.

Aluminum?  Or EMT?

[W3DRM]

I'm only using one 10-foot length of aluminum conduit, so no threads to tape. I'll be using the wireless transmitter on the anemometer/wind vane (located down near ground level), so the ISS can be in another part of the yard (final resting place to be determined).

Be sure to post some photos of your final installation so we can all enjoy your work.

The only reason I suggested putting caps on the pipe ends was to keep the bugs and spiders out.

[Ladd]

Aluminum?  Or EMT?

The sales guy said it was aluminum; the label on the pipe says EMT. I'll believe the label. And the HD website says it weighs less than a pound when it clearly does not.

[dalecoy]

Aluminum?  Or EMT?

The sales guy said it was aluminum; the label on the pipe says EMT. I'll believe the label. And the HD website says it weighs less than a pound when it clearly does not.

Yes, believe the label - and I've never seen aluminum conduit at Home Depot.

The weight is probably "per foot". 

[Ladd]

The weight is probably "per foot".

That makes sense. Still weighs much less than the 1" I.D. water pipe.

[C5250]

Hopefully there won't be any reaction between the steel mounting U-bolt and the aluminum ...

I think it's already clear you probably don't have aluminum, the easy way to check would be to use a magnet (a magnet will stick to steel, but not AL or most SS). But, there is some reaction between AL and steel, don't ever combine AL and stainless though. That said, anything galvanized should show little corrosion for about 15 years.

I've never capped the top of a mast, my thinking being that there is better airflow uncapped to dry it out. Rain would not be the only source of moisture, condensation will happen nearly every day.