Be careful in considering aluminum as a mast material. Whereas some aluminum alloys offer an attractive yield strength, many do not exhibit an ultimate strength with much margin over yield (a.k.a. to
Steve - I should have better defined toughness as the amount of additional strain a material can tolerate before it reaches ultimate strength. The later is often, but not always associated with the d
As a consulting PE, I would caution you that copying someone else's design documentation for an unintended installation does not necessarily guarantee a safe installation, and may violate laws in cer
Thanks Joe. Sorry Maximo, I completely missed your location and situation. KM5VI --Original Message-- From: towertalk-bounces@contesting.com [mailto:towertalk-bounces@contesting.com] On Behalf Of Jos
screening... "Steel is a very poor conductor at RF" You may also want to look up WB0JGP's article on ground screens from Aug 1977 edition of Ham Radio magazine. As an engineer, steel, even galvanize
GM3SEK brings up an interesting point about skin effect. Good comments also about soil characteristics having a profound effect on corrosion life. Drawing on experience with underground piping - it's
For proportional crankup tower lift systems, I have successfully used angle stops added to the top section just below the rotor plate. The stops prevent the top section (only) from nesting the rotor
I can suggest taking a look at the MMANA-GAL and 4nec2 programs. MMANA-GAL may be more user friendly but 4nec2 is more versatile. These are both available for download - just Google search. Both will
Dave, I have designed a hinged base for my LM-470 using finite element stress analysis techniques. The design in present form uses (6) 1-1/8" x 36" high strength anchor bolts and facilitates service
Take a look a 4NEC2 and also MMANA-GAL KM5VI Hello to the group, I just discovered that the program I use to model antennas is defunct. It is/was Antenna Model. What are the programs that are being u
Bolt failure theory and the engineering design of bolted connections differentiate connections by how the load will be transferred though the connection. "Slip-critical" class connections rely on fri
It would take a wind pressure of over 750 psf to bend a 4' section of 2" SCH 40 pipe to the point of permanent deformation. 750 psf is about 30 times as much pressure as would be generated by a 100 m
The 750 psf considers tensile bending stress in a 4' mast section only (no antenna) assumed yield 35 ksi - probably a little high. Agree that 27 ksi is a better design limit w/ some safety factor. Th
Nice explanation & spot-on. KM5VI Dave: The comment was meant to make you think about what you purport to say is true when it is not, in the context you use. Concrete does indeed have pores and they
Echo the good recommendations to look for a motor shop, but to address your question you might try WW Grainger, a national industrial supply company. 73 KM5VI Some one else already mentioned it, but
I have an older F12 EF240X beam with linear loading. I initially found the F/B performance to be dependent on the tuning of the elements. I used an antenna modeling program to find a combination of e
Hans is right, if the design calls for 5000 psi then it should be adhered to. Crank-up tower foundations function more as ballast (to prevent overturning) than as structural columns. Because of the m
Perhaps Holes, Inc. can help. KM5VI Howdy, TowerTalkians -- I've added anchor bolts to existing concrete bases many times and historically have rented a roto-hammer and bit. It wasn't a concrete dril
At least one manufacturer does offer an option for stainless steel lifting cables. The option does require some pulley upsizing because size-for-size, stainless steel cable alloys have lower load rat
This thread peaked my curiosity... Neglecting the RF characteristics of a strike, impedance, & skin effects... Calculate how long it would take a copper rod, 2" dia and 1 meter long to reach melting