Some times you don't need a heavy duty tower bracket.
Two version have been designed. Starting with the left type, it's designed for mounting a yagi beam to a small tower, such as R-25G. Angle "L" metal is used. For the sizing, the general rule of thumb is the same size as the pipe it will hold. For example (on the left) the yagi's boom is 3/4" copper pipe, therefore that V section is "L" angle 3/4" x 3/4". R-25G legs are around 1", therefore that V section is "L" angle 1" x 1".
Then for the hose clamps to be used, the yagi (3/4" pipe) needs size # 12, while the (1") tower leg needs size # 20. These "sizes" are standards for brands of hose clamps, including Ideal. Check their web site for other equivalents of hose clamp sizes, if you need to.
The antenna V section is mounted with enough distance away from the tower leg to permit easy access to the coax connector.
For the right picture is a back-to-back "VV" bracket for mounting a sewer pipe (ABS) dipole to this type or larger tower. In this case the ABS used is 1 1/2" therefore, that V section is "L" angle 1 1/2" x 1 1/2". The other half of this bracket depends on the tower it's going on; in some cases large microwave tower legs are 3-5" in diameter, etc. For the hose clamps for this application it's believed the (ABS) antenna side would need size # 32. Depending on the tower leg, the other half might need a size # 40; but it's best to check the leg's diameter to be sure. There are some sites, where the leg's over 12". Size # 104 or even a couple in series may be needed. As always, it's best to bring several sizes of hose clamps to the site.
Note the room that is designed into both version, to give the hose clamps room to slip inside and around the V and pipes.
On the Yagi (VV) bracket example, here's some tips on installation. Keep in mind these pictures were not "staged" on the ground, rather taken with an actual (in-service) antenna on the tower at the 40 foot level. In case you one arm is tied up you can even do most of it with the other. In this case install the two hose clamps to the tower leg. For the R-25 that will be #20 clamps. Tighten them in the direction you wish to point the yagi. Next, place the two other clamps, for the antenna as show leaving the right clamp closed but loose. That would be #12 clamps. Then slide the end of the yagi inside the closed clamps to hold it. Then tighten both of them.
Plug in the coax and tape it up. For most of the prototypes and MCP location (in town) only one layer of tape is used. However for major sites, a minimum of two layers is needed. Another alternative is one layer, then covered by the mastic padding, then an outer layer of tape.
Just another angle of the installation. Note the clamps are not completely installed at time of this photo was taken. Early construction pictures are available here. .
Notice the close fit from the connector to the tower leg? In 2014 an improved version was realized, by making the top "V" at an angle as you can see in the early construction picture; the existing ones were modified to various angles, with more rough stock in the background for future projects.