Just another electrical question

[Cord]

Now I see that you are trying to design for a future light show. The idea of setting a panel out there is a good one for distribution purposes, however, the panel needs to be 36" above ground. Very unsightly. Instead of a permanent install, I'd suggest using temporary equipment which is mobile. Being a seasonal display this would be appropriate and then the rules start to relax.

 

[EddieWalker]

I disagree with some of the others on the footing. At 30 feet, with a flat, during a severe storm, you will have a lot of force pulling at that pole. Assuming that you are using a pole designed for flags, and not just a pipe of some kind, I wonder if you are deep enough? If it was me, I think deeper and not as wide would be a lot better. Just a 12 inch hole 6 feet deep would give you more strength, and 8 foot deep would be even better.

I have several street lights that are cemented into the ground over three feet deep from my 12 inch auger that sway in the wind. They are twelve feet in the air and made from 4 inch galvanized pipe.

Of course, before doing anything, I would contact the flag pole company and do what they say. If they say four foot deep by four foot square, then that wold be the best thing to do.

 

[Redlands Okie]

A rule of thumb often seen with such items as telephone poles or light poles is that they are placeded at 10% of the length of the pole plus 2 feet. So the 30 ft pole would be at least 5 feet deep.

 

[JerryK]

Depends on how big of a flag, too... I have put in several with about a 3' by 12" wide hole with about a 3' dia cement pad around it to help with mowing. Poles about 25' high and 3' by 5' flag.... no problems in many, many, many years...

 

[TemporaryKubotaOwnerMark]

A rule of thumb often seen with such items as telephone poles or light poles is that they are placeded at 10% of the length of the pole plus 2 feet. So the 30 ft pole would be at least 5 feet deep.

Not when you have such a massive diameter footing in relation to the pole. No need to go deeper with all that concrete in place.

On the other hand, an 18" hole 5 feet deep with a 4' diameter pad (say, 6" deep) would actually be better and take FAR less concrete.

 

[EddieWalker]

Not when you have such a massive diameter footing in relation to the pole. No need to go deeper with all that concrete in place.

On the other hand, an 18" hole 5 feet deep with a 4' diameter pad (say, 6" deep) would actually be better and take FAR less concrete.

I disagree. You are focusing all the stress of the pole on 18 inches. While the amount of concrete might be sufficient to hold a 30 foot pole in the air, the amount of surface area of the pole in contact with the concrete, or side walls of a hole needs to be sufficient to withstand the forces applied to the end of the pole farthest away.

A 30 foot pole is over 3 stories high including the roof!!!! That's a lot of height, and a lot of leverage.

 

[JerryK]

All the stress on the poles is at the point the pipe exits the concrete... There is not much stress on the pole, say 1' into the concrete... I put my poles in with two 4" channel cemented into the concrete, with the pole sandwiched in between these two pieces bolted thru with stainless bolts. That way I can lower them to paint/fix rope/etc. All you need concrete wise in enough mass stuck into the ground deep enough that the soil will keep it from shifting. Depending on pole height, size of flag, etc... with a proper pad around it so you can zoom by with your ZTR.

 

[TemporaryKubotaOwnerMark]

150' steel monopolies and electrical transmission towers are mounted with NONE of the pole in contact with the concrete. They bore a hole just a bit bigger than the diameter of the base of the pole, and a rebar cage is set in place and concrete poured on that. The tops of some of the vertical rebar pieces are threaded, and after curing, nuts are run down on the threads. The pole is set on those nuts (which are carefully leveled first) and then more nuts go on top of the pole base.

Scaled up to 150' from 30', the equivalent of 18" would be 5 * 1.5', or 7.5 feet, which is about what those monster poles have. But they have FAR more weight and loading on them than any 30' flagpole ever will.

 

[EddieWalker]

150' steel monopolies and electrical transmission towers are mounted with NONE of the pole in contact with the concrete. They bore a hole just a bit bigger than the diameter of the base of the pole, and a rebar cage is set in place and concrete poured on that. The tops of some of the vertical rebar pieces are threaded, and after curing, nuts are run down on the threads. The pole is set on those nuts (which are carefully leveled first) and then more nuts go on top of the pole base.

Scaled up to 150' from 30', the equivalent of 18" would be 5 * 1.5', or 7.5 feet, which is about what those monster poles have. But they have FAR more weight and loading on them than any 30' flagpole ever will.

But how deep do the bore that hole into the ground?

 

[TemporaryKubotaOwnerMark]

Same 10% of pole height, in normal conditions. Of course, really sandy soil, bedrock, lots of variables can change that.

I saw one that was on sand that went down basically forever. Very loose. Not good. They poured something like a 20x20 slab about 8 feet thick. This was for a big monopole, but I don't remember the height. The point is, soil conditions mean a lot.