W1TR Hanging Hinge Plate Boom to Mast Mount
Updated 11-Jun-2021 13:38
Here is the W1TR Hanging Hinge Plate that allows the antenna to stay level while the tower tilts up or down. NN4ZZ makes a similar one called the Tilt Plate, but for $750 I decided to make my own… for less than $200 ! N6RK also has a homebrew design. Undoubtedly theirs are a little stronger, but I could have gotten thicker aluminum plate for maybe $10-20 more if needed. In any case, it seems that the one I built was stronger than the original part ! ? I’ll let you know how mother nature treats it as time goes by! Some folks have tried to make a hinge lock that keeps the hinge shut when in the air, this design could quickly be adapted to have a hinge lock if necessary, I have NOT found it to be necessary even in 60 mph winds.
The stainless steel hinge (1 foot by 5 inches by 1/8” thick) was purchased from McMaster Carr (part 1582A83, $56 + shipping).
The many bolts, nuts, lockwashers were purchased from Sears Hardware, all stainless steel (approximately $25).
The aluminum plates (1 foot square by 3/16” thick) were purchased from Admiral Metals / Metal Source as scrap pieces for $2 / lb, total cost $9 !
They have much thicker ones if needed (even an inch thick or more)!
I drilled over 50 holes in the various parts… first a small starter hole (1/8” drill) then a real hole (13/32” which is 3/8” + 1/32”), and for the 12 clearance holes a 5/8” hole. It is recommended to get a really good drill such as the Craftsman ˝” drill and a drill press kit (or simply a drill press itself). It took quite a while to drill all those holes. The XYL calls it the Aluminum Swiss Cheese, but here is the real Aluminum Swiss Cheese!
As of Dec 2016, the hanging hinge plate has been a total success. Since it’s installation in Dec 2008, no particular wear and tear so I guess it must be rugged enough. It would probably be adequate to use only 4 DX Engineering U-Bolts rather than the 8 that I used, but I wanted to build this thing conservatively.
However, I have the following lessons learned for those who build this item.
The hinge pin tends to work itself out of the hinge slowly as the high winds rock the antenna a little. After 18 months of service, it worked itself out about an inch and a half. So I estimate about 1 inch per year. I tried drilling a small hole through the hinge pin and a inserting a small cotter pin to prevent this from happening. (yeah, drilling through stainless steel is a real pain in the butt, especially in the field instead of on the bench)
As it turned out, the cotter pin broke after a couple of months and the pin began working itself out again.
This time I screwed on a couple of tab / ears that prevent the pin from working its way out.
These tabs prevent the hinge pin from working its way out of the hinge.
I tried to leave the ends of those DX Engineering U-Bolts at their original length, but I just couldn’t get them to have proper clearance in the holes with the antenna mounted and distorting the mounting angle a little. I ended up making the clearance holes larger as well as cutting the ends of the bolts off after all! I used a saws-all to do it mounted on the tower, it would have been much easier to do so on the work bench in the first place?
During a recent phone call from W3JK (JK Antennas), he made
the suggestion that if the hinge were attached to the middle of the aluminum
plate fastened to the mast, there would not be a clearance problem with the
Ah well, this was my first attempt, and there were a few lessons learned!
It has lasted over a decade without any issues, so it wasn’t all that bad a first attempt!