Hustler BTV Feed Point Repair
I recently acquired a Hustler 6-BTV HF Vertical Antenna. However, as it seems to be a common problem on the BTV series, I found that the screw that is the coax center feedpoint on the base of this antenna was rusted in place. I tried soaking in penetrating oil and it wouldn't budge. As I had no other choice I cut the head off the bolt/screw so that I could fully disassemble the base assembly for further analysis. I drilled it out, and decided to attempt re-tapping it for a new 1/4" bolt, in doing so I snapped off the hardened tap! After doing that I had to engineer a repair, which I will document here!
I had some requirements in mind, it must be mechanically sound as well as electrically, but also allow for ease of future repair if necessary. It also had to be affordable, a replacement base assembly is sold as a complete unit for $53, the total cost of this repair is roughly $20! I also wanted this to be an improvement as well as a repair/replacement!
With that in mind here is the components i needed to purchase.
1 - 1/4" x 2 1/2" Stainless Steel Bolt
4 - 1/4" Stainless Steel Flat
Washers
2 - 1/4" Stainless Steel Lock Washers
2 - 1/4" Stainless Steel Nuts
1 - #6
x 1 1/2" Stainless Steel Machine Screw
1 - #6 Nylock Nut
1 - Custom Aluminum Slug (read on for details, its easy!) I also have some
available for sale!
Disassembly:
I am not going to bore you with details here, however I will try to represent it well enough to allow duplication! The first thing you need to do is carefully cut off the head of the screw, this is necessary so you can fully disassemble the base assembly by removing the tube and insulators from the mounting bracket. Once you have done this you will need to drill out the cross pin that holds the factory installed steel slug in the bottom end of the base tube. On the side of the tube there is a weep hole and directly below that there is a second hole in which you will see a steel pin. You will need to drill that out, I center punched and drilled the pin out, however I went with a slightly larger bit then necessary as I was not sure if i would need a larger hole to facilitate removal. After having done this now I can tell you a drill bit the same size as the new #6 machine screw can be used to remove this pin!
Here you see the pin drilled out and the steel slug that they insert into the base tube removed. I had to use a long steel rod inserted into the base tube from the top end and a couple solid blows of a hammer to pop it out. Now remember, I did soak the base in penetrating oil in an attempt to remove the screw at first so that may have helped loosen it up a bit as well.
Here is a better look at the steel slug that was pinned into the base of the tube for the feedpoint connection. As I mentioned above I broke off a hardened tap in it, which means its pretty well shot. Drilling out the tap would be next to impossible, yes they do make tap removal tools but i decided to make a smaller investment and replace it.
The next step is to drill out the base insulator to accept a 1/4" nut on the base of the new slug which will be replacing the original steel part that was removed. In the above picture you can see that the steel piece had a shoulder on it, this shoulder keeps the base tube centered in the base insulator and the hole in the bracket. The shoulder is 3/8" in diameter by 1/4" in length. My initial thought was to use a bronze bushing on the 1/4" bolt to accomplish this, but locally these bushings are hard to find and cost about $3 each, so I decided to go with the cheaper hardware store alternative and drill it! I used a Unibit, it makes a nice clean hole in plastic, I drilled halfway from both sides to get a nice clean 1/2" hole in the base insulator.
Drilled and ready to install!
Now to create the new slug. If you have a metal lathe you could easily
create this piece and machine a really nice replacement including the shoulder.
I don't have that ability. I kept this repair to the basics, hand tools,
and basic power tools. I do have a drill press at my disposal to make it a
bit easier, but this can also be done with a handheld drill and some time and
patience. The first step is to acquire the new slug. I couldn't find
a source locally for this piece and had to order it from
www.onlinemetals.com for a total of
about $16. I know, expensive. But shipping is a large portion of the
cost and its a cut and ready piece that all I needed to do was drill it out.
Compare this to a replacement base assembly at roughly $53 and its inexpensive!
Here is the raw pieces as received.
6061 Aluminum, Dimensions - 13/16" (.8125) diameter x 1 3/8" (1.375) length. A note on the length, be sure to measure the distance from the bottom end of the tube to your weep hole so that the slug sits even with the bottom of it or slightly above the bottom edge of the weep hole so it won't trap water. This was the perfect length on mine, but there may be slight variances in manufacturing so adjust accordingly!
The first step in machining this part is to drill a center hole all the way through for the 1/4" bolt.
The next step in machining this part is to insert the 1/4" bolt and mark the thread length needed. The threaded portion of the bolt is not long enough, time to dig out the tap & die set to fix that!
Now we have a new slug with a bolt installed in it using a single nut only.
The next step is to drill through the base tube, slug, and bolt for a cross bolt, the #6 machine screw in the parts list. I just inserted the slug into the base tube and set it flush with the bottom end of the tube and drilled all the way through. Again the drill press makes this easier but with a vise and a handheld drill this can still be accomplished.
All that is left to do now is install the #6 machine screw, cut off the excess if you prefer, and then reassemble the base. Slide the tube back into the bracket, install the top three screws and tighten, slide the bottom insulator over the new bolt and install the three screws that hold it to the bracket.
Install washers and a lock washer on the new 1/4" bolt in the same configuration as you would for the machine screw and add a single nut.
Conclusion:
Remember to use Penetrox A and anti-seize on all the joints and connections. To facilitate removal in the future you should use anti-seize on the new stainless steel bolt and a product like Penetrox A on the slug to prevent it from corroding inside the tube.
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