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You don't pull a 25,000 lb block of cement out of the ground. You tip it over by providing a large force at 40,50,70 feet etc, from the base and using the standard ft lb calculations you generate a tremendous rotational torque at the base.Case in point here. My Hygain Explorer 14 presents a wind load of 192 lbs. in an 80 mph wind. Mounted at 65 feet that means 12,500 ft. lbs. of rotational torque at the base plus the wind drag over the length of the tower not to mention the other antennas mounted on it. If the ground has been saturated by rains etc then it can move if it is too small. Of course as with everything there is a safety factor built in and it depends on the soil conditions at each site. Unless one has a degree in soil mechanics or geotechnical engineering and can properly analyze their soil conditions and install exactly to their own local conditions then you pretty much have to follow the general recommendations from the manufacturer. My base is actually a bit smaller than the manufacturer recommends. This is because I encountered a bed of slate about 2 1/2 feet down. The top foot or so of this slate was soft and relatively easy to break out with an electric jackhammer I had rented. Down about 5 feet it was very hard to break up and extract from the hole. I used a pressure washer to wash the sides of the slate bed cleaning out any stones plugging uo the layers. This allowed the concrete to really grab good into the layers of slate. I also drilled a couple holes into the slate and drove some metal rods in at an angle. This anchored the concrete base to the slate bed making for a very strong base even if it was a bit smaller than the recommended size.I also made the hole wider at the base than at the top to make it somewhat bell shaped to make it harder to want to lift. If it had been all sand it would have been a different matter.

This is what I had to contend with. On the left side you can easily see the line where the slate starts. This is before I washed out the loose stones and drilled the bottom of the hole.

<blockquote data-quote="Captain Kilowatt" data-source="post: 454368" data-attributes="member: 39">You don&#039;t pull a 25,000 lb block of cement out of the ground. You tip it over by providing a large force at 40,50,70 feet etc, from the base and using the standard ft lb calculations you generate a tremendous rotational torque at the base.Case in point here. My Hygain Explorer 14 presents a wind load of 192 lbs. in an 80 mph wind. Mounted at 65 feet that means 12,500 ft. lbs. of rotational torque at the base plus the wind drag over the length of the tower not to mention the other antennas mounted on it. If the ground has been saturated by rains etc then it can move if it is too small. Of course as with everything there is a safety factor built in and it depends on the soil conditions at each site. Unless one has a degree in soil mechanics or geotechnical engineering and can properly analyze their soil conditions and install exactly to their own local conditions then you pretty much have to follow the general recommendations from the manufacturer. My base is actually a bit smaller than the manufacturer recommends. This is because I encountered a bed of slate about 2 1/2 feet down. The top foot or so of this slate was soft and relatively easy to break out with an electric jackhammer I had rented. Down about 5 feet it was very hard to break up and extract from the hole. I used a pressure washer to wash the sides of the slate bed cleaning out any stones plugging uo the layers. This allowed the concrete to really grab good into the layers of slate. I also drilled a couple holes into the slate and drove some metal rods in at an angle. This anchored the concrete base to the slate bed making for a very strong base even if it was a bit smaller than the recommended size.I also made the hole wider at the base than at the top to make it somewhat bell shaped to make it harder to want to lift. If it had been all sand it would have been a different matter.This is what I had to contend with. On the left side you can easily see the line where the slate starts. This is before I washed out the loose stones and drilled the bottom of the hole.<img src="http://imageshack.us/a/img7/9139/img2293x.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" /></blockquote>

[QUOTE="Captain Kilowatt, post: 454368, member: 39"] You don't pull a 25,000 lb block of cement out of the ground. You tip it over by providing a large force at 40,50,70 feet etc, from the base and using the standard ft lb calculations you generate a tremendous rotational torque at the base.Case in point here. My Hygain Explorer 14 presents a wind load of 192 lbs. in an 80 mph wind. Mounted at 65 feet that means 12,500 ft. lbs. of rotational torque at the base plus the wind drag over the length of the tower not to mention the other antennas mounted on it. If the ground has been saturated by rains etc then it can move if it is too small. Of course as with everything there is a safety factor built in and it depends on the soil conditions at each site. Unless one has a degree in soil mechanics or geotechnical engineering and can properly analyze their soil conditions and install exactly to their own local conditions then you pretty much have to follow the general recommendations from the manufacturer. My base is actually a bit smaller than the manufacturer recommends. This is because I encountered a bed of slate about 2 1/2 feet down. The top foot or so of this slate was soft and relatively easy to break out with an electric jackhammer I had rented. Down about 5 feet it was very hard to break up and extract from the hole. I used a pressure washer to wash the sides of the slate bed cleaning out any stones plugging uo the layers. This allowed the concrete to really grab good into the layers of slate. I also drilled a couple holes into the slate and drove some metal rods in at an angle. This anchored the concrete base to the slate bed making for a very strong base even if it was a bit smaller than the recommended size.I also made the hole wider at the base than at the top to make it somewhat bell shaped to make it harder to want to lift. If it had been all sand it would have been a different matter. This is what I had to contend with. On the left side you can easily see the line where the slate starts. This is before I washed out the loose stones and drilled the bottom of the hole. [IMG]http://imageshack.us/a/img7/9139/img2293x.jpg[/IMG] [/QUOTE]

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