Repairing a Tail-Twister Rotator

 My Tail-Twister rotator was purchased new around 1976 and has been in constant use since that time. It was originally used with a large Mosley TA-36 with the added, and heavy, TA-40KR traps to add 40 meters to the driven element. I also usually always have had a pair of Cushcraft 2 meter twists A144-11T above that, topped with a variety of 2 meter and VHF/UHF ground planes, so there was always a good amount of windload on the rotator.

I moved it to my present QTH in 1992 but it remained on the same 69 foot Rohn 45 tower with the same Cushcraft 2 meter beams and various ground planes above it so it has had a good and hefty windload on it for many years.  All during that time it has served me well.

In 2002, I brought it down and rebuilt it, a job which consisted mostly of a thorough cleaning, new bearings and races, new direction indicating pot and a complete relubrication. I've usually kept a spare stainless steel ring gear on hand but I don't recall replacing that gear at that time. The rotor swap story is available elsewhere on this website.

It came time to do more work on my rotor again when it developed the strange anomaly of stopping when pointed around the 90 degree area. With this installation (the center of the meter scale was on North) it caused some problems. Around Oct of 2005 I had replaced the Mosley beam with a new 3-element SteppIR, still with the Cushcraft 2 meter beams and ground plane above it. When my rotor began to have its stoppage problems when aimed toward the East, the SteppIR became a real life-saver since I could aim West and use the SteppIR's 180 degree reverse feature to shoot back to the East. My only problem would come when my excitement and the technology became too intense.

I also have the Rotor-EZ built into the rotator indicator box and that is attached to my computer while running Logger32 logging and control program. Features in this program allow me to simply click on a small dot on the map where a new DX station has appeared and my rotator automagically turns to that location. Logger32 makes it easy to also click on a spot for long path, and with the 180 degree selection on the SteppIR, that works fine............. except in the heat of battle........ or a sudden pileup. Without thinking, it's possible to attempt to send the beam to aim at the new spot, not thinking about the "dead zone." Several times I let the technology send my array to the East...... Oh No!! Too late.

Once it got the "dead zone," there were only two ways to get out.  One was to either climb the tower and manually turn the antenna away from East while someone below operated the rotor box (pictures of me at other places on this website help to explain why my climbing was not an viable option). The other way was to be in the shack when the wind was blowing hard and when it seemed to be blowing the right direction, I could release the brake and if the wind was blowing just right, it would move back into the rotator's "active zone" and I was OK. Unfortunately, although the wind blows often in Oklahoma (remember the song -- "When the wind goes sweeping down the plains........"), I was never able to completely anticipate when I needed to perform this delicate operation. Sometimes, if I was lucky, I could get it back within a day but there were times when it sat watching the Eastern sky for more than two weeks.

Finally I knew it was time to swap it out, bring it down, and rebuild it. The task went to Harry - KC5TRB, my expert tower man. He got the Tail-Twister down without event and move the replacement back in its spot. The temporary replacement rotator is the Ham II discussed also on these webpages. Right now, after several months, it has developed some problems and the brake will no longer engage. I suspect that the spring or springs which draw the brake wedge to its "brake on" position, has failed. I have a TV camera with microphone mounted just above the rotator and I can usually hear the brake wedge popping in and out. Now, there is a sound but it is not a powerful and definite click like it was originally. Only the motor and its gear train are holding the beam from rotating in the wind........... and they have long ceased to perform this function. My antenna array is currently freely windmilling like a country weathervane without a rooster.

I suddenly now have an added incentive to rebuild my trusty Tail-Twister and that is what this article will describe.

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Tail-Twister prior to opening	First, I placed the rotator upside down over the 1 1/2" pipe mounted on the wooden form.  This form, shown on the right, was originally used to hold a portable TV antenna on my travel trailer.  The piece with tapered ends is placed between tandem wheels.  It works nicely as a rotator support form too. It is important to support the rotator, bottom-side up, when you're working on it.  It does not need to be a solid support but you'll want to have your rotor bottoms up while you work on it. The 4 longer bolts facing up are bolts used to hold the rotator to the rotor shelf on the tower.  The replacement rotor uses different sized bolts so when this one was brought down, I kept its bolts with this rotor so they wouldn't get lost or used for something else. Note that the Ham-M series rotators use 4 bolts to hold the two halves together, the Tail-Twister has 6 bolts.  Don't pay any attention to the messy workbench -- lots of simultaneous projects going. Remove the 6 bolts and nuts (plus the 4 others mentioned above) and place all of them in an empty pill bottle.  That's what those amber-colored bottles are and they help me keep track of removed hardware.
When I opened the rotator up, the grease was fairly dry and didn't look like it was doing much lubrication. Not sure how he got in but there was a dead spider inside the top bell. He was about 1/4" long in his current condition and I'm sure he had some interesting rides around on the wiper of the direction indicating potentiometer before assuming his current condition.  I haven't found any small particles of broken metal pieces inside so I'm already encouraged with this. As mentioned in another article about repairing antenna rotators, it's a good idea to mark the two case pieces with a magic marker so they can be matched up easily when reassembling.  I also mark the bottom plate of the rotor (the one which rotates when it is upside down, and the bottom shell of the rotor.  The Tail-Twister does not seem to be as critical along this line as some of the units in the Ham-M series.  I actually did mark my cases before disassembly but ended up painting over the marks.   It might help you to mark them, it shouldn't hurt anything, but you'll need to make some other provisions if you plan to repaint your Tail-Twister as I did. An observant reader will see some atrocious-looking goo covering the screw terminals on the bottom of the rotor.  This is the way I chose to seal or weatherproof the screw terminals.  All of my rotors are the older type which have screw terminals for the 8 connections instead of the newer socket.  I attached the wires of the rotor cable, then covered the area with black RTV silastic rubber compound.  In recent years I have read about the vinegar-smelling goo causing problems with some connections over time but since it's been on there for several decades and I'm not aware of any of my rotor problems being caused by these connections, I'm going to not worry about it.  It's kinda like asking the 98 year old man if he didn't think he should stop his smoking so he could live longer.

Once the motor assembly was separated from the bearing races, the bottom bell containing the brake "engagement slots" I looked over things, trying to find any obvious damage. A recent message on the TowerTalk reflector talked about a Tail-Twister which was slow running in one direction. His later message described the problem he had found with a broken gear shaft so I was looking, in particular, for that being a possible solution to my problem. See message below: The plastic bearing holders have a flange on one side.  Take careful note of the way this flange is seated, whether up or down.   You'll need to know when you put it back together.  On my Tail-Twister, the small and large bearing races (the first to be removed with the rotor upside down) both had the flange down.  The smaller bearing race holds 40 ball bearings.  The larger bearing race (the middle one in the rotor) holds 49 bearings.

At 04:41 PM 1/28/2008, Mike wrote: Need some ideas on where to look to find out why the T2X turning in the CCW direction is slower than in the CW direction. Recently noticed my T2X takes longer to turn in the CCW direction than in the CW direction. Wind is not the reason as slow CCW direction turning occurs even with ~0 wind. The phase capacitor is mounted at the T2X and the power and position indicator lines are, respectively, #12 and #14 gauge wire. The capacitors are several years old and mounted in a water resistant box (small vent hole on the bottom). The T2X is ~ 250 ft from the in-shack control box. The T2X is turning a EF240X and a 4 el. SteppIR on a 2" dia., 1/8" wall, 21 ft chrome-moly mast. The mast and ant. weight are supported by the T2X. Sixteenth inch shim stock is used to center the mast in the T2X. Thrust bearings are used to center the mast but not for supporting the mast and ant. weight. The T2X is mounted 8 ft from the top of the tower. Several months ago the T2X's mounting bolts and thrust bearing mounting bolts were checked for snugness. This CCW rotation slowness was just noticed this last month when the weather turned cold. The last several years the T2X rotated the mast/ant. equally the same speed in both directions. 73, Mike, K4GMH From:    Mike <k4gmh@arrl.net> Subject:    Re: [TowerTalk] T2X Slow CCW Rotation Problem Date sent:    Thu, 06 Mar 2008 14:15:03 -0500 Hello, The problem with the rotor is the rod holding the series of gears used to turn the internal ring gear and the rotor had sheared off in two places. When the rotor housing was first removed, noticed the drive gear was wobbling. The wobble is the reason for the delayed start in the CCW direction as it wasn't engaging the ring gear at start up. This same thing, post shearing off, happened three years ago and the T2X part was replaced. Probably a good indication that its trying to turn too much ant. 73, Mike, K4GMH	Brake wedge
	Brake solenoid
	Brake engaging grooves
	Top bell with upper bearing race (old race with dried grease)

All the gears in my Tail-Twister seemed to be secure with no broken posts. I hooked power back up to the motor and turned it all the way CCW. It moved the ring gear around normally and tripped the end of rotation switch, just as it should. Remember this is a stainless steel ring gear and not the cast metal type used in the older Ham II, III, etc. series. I turned it back CW and it turned beautifully until it got to what would have been the eastern direction on my tower, and it stopped. The motor continued to turn, as long as I kept my finger on the switch, but the rotation on the ring gear had stopped.

	Still, I didn't see what might be causing this, however, as soon as I dug out my extra bright flashlight, the problem became evident. Eight teeth on the ring gear were missing but they had not been apparent when I first looked because the missing teeth were directly under the stob which trips the end of rotation switches. In addition, there were 3 teeth partially chewed down from 1/4 to 3/4 of the height of a normal tooth. Once I knew what I was looking for, I could look back down on the ring gear and see several of the teeth missing which were unshielded by the stob. In no other spot around the ring gear were any teeth even partially damaged.   It would be interesting to learn what caused those teeth to be broken out of just that one area. Perhaps, some day I will sit with my feet propped up and the cleaned-up culprit ring gear in hand and contemplate the possibilities of the damage.
The cure became simple, replace the stainless-steel ring gear with another of the same material (but several more good teeth) and continue the clean-up, lubrication, and repainting of the Tail-Twister. Fortunately, I like to keep a spare stainless steel ring gear and a spare direction indicating potentiometer.  It was an easy fix for me.  This old antique may outlive me now.

Cleaning the parts became quite a challenge. Ideally, if a person had a solvent dunk-tank, they could let the pieces (with the exception of the motor assembly) have a good soaking. If you had such a tank, or know a mechanic who has one, I would recommend it highly. Unfortunately, I did not have one nor did I know anyone who did so I had to do it all by hand, like the early pioneers did.

Most of the rusted bearings were in the smaller race which fits in the bottom area of the rotator, below the motor assembly. The bearing race holds only 40 bearings whereas the larger two races hold 49 bearings each. I believe that these were the most rusted because the bottom of the rotator provides the poorest seal against the weather. When mounted normally, the rotor body does shield this area but there is still a space which must be there to allow the rotator to rotate. Dust, moisture, and evidently my spider were able to enter the unit at this point.

By the way, MFJ didn't seem to have a specific package listed for the Tail-Twister, only the HAM-IV (Ham-M series). The third bearing race, the one mentioned above from the lower run and with the rusted bearings, is actually smaller and takes fewer ball bearings. This means I'll have some left-over bearings when my project is complete.  If you are buying the replacements from MFJ for a Tail-Twister project and they only had the same package they offered to me, you will obviously need two packages. 

The more I checked the metal machined tracks attached to the motor assembly, the more I found much evidence of the goopy material made up of dust/dirt and dried grease. It clings to every piece and needs to be completely removed down the to original bare metal. Not a particularly easy job but a necessary one. It seems to hide too. Clean, inspect, and clean some more. Put the piece aside for a while and when you come back to it, you'll probably find more goopy stuff which also needs to be removed. I even used a quantity of Q-tips with solvent to clean those hard-to-get-to places. I'm quite sure, when I rebuilt my Tail-Twister back 6 years ago, I did not check it as carefully as I did this time. I didn't remove any but the most obvious goopy stuff back then. Of course, that may explain why it lasted 26 years until its first rebuilding but only 6 years until the second. I recommend you spend lots and lots of time cleaning it up while you have it opened up. This may also explain why you thought it was too expensive to send your rotor to a commercial rebuilding facility that advertises in QST.  If it's done correctly, you'll spend some time in the effort.

Here are the two outer shells, complete with their new flat black paint job.  Note that I did take out, i.e. did not paint, the stainless steel U-bolts and the other clam-shell piece used to hold the mast tightly against the taller V-shaped piece on the top of the rotator.

Now you're ready to assemble the motor assembly to the rotor upper bell.  This operation can be quick and easy and highly successful or can be one of the most frustrating activities you've encountered since first trying to learn the morse code.   Several pieces must be identified: 

Assuming that all is OK, i.e., the first set of greased ball bearings is seated correctly, the motor assembly is correctly inserted in the top bell housing, the rotor is able to rotate a full 360 degrees and the motor stops completely at the end of each rotation, and (most importantly, at this point) the meter indicator moves from zero scale at one extreme rotation to full scale at the other extreme rotation and keeps following the rotation, regardless of where the rotor position is moved.   You're now on the home stretch, but wait!!!!!! Don't get in too much of a hurry because that's how ball bearings get accidentally knocked out of the race and roll under the work cabinet or down the heater and air conditioner vent in the floor.  Of course, since you had some left over ball bearings, the one that dropped is still findable but if you only had just enough, that puppy that dropped would now be in China.

Take the second larger plastic bearing race and load it up with its 49 ball bearings while you still have the whole thing in a box with small sides or a larger box top.  Completely grease up the race as described above.  Use enough grease because it's going to be up there on your tower, unattended, for the next 5, 10, maybe 20 years without needing any intervention from you (we can dream, can't we?).   Immediately, while your hands and fingers are still greasy, place this bearing race in place in the rotor housing, paying particular attention to which way the race's flange is pointing (you did write down that information when you started, didn't you?)

When that race is in place, you'll want to finish up the bottom bearing race.  Actually it's at the top of what you're working on since you should still have the rotor upside down on the workbench.  This plastic bearing race will be too long as it comes from MFJ so you'll need to trim it down.  The piece, as it comes from the package, will hold a total of 49 bearings but this last race is smaller and should only have 40 balls.  It can be trimmed easily with a pair of side-cutters but I must caution you with the old carpenter's axiom:  "Measure twice, cut once"   I suggest counting from one end to the 40th hole and count backward from the other end to make sure there were 9 other spaces.  Once the race is trimmed, the last bearings should be inserted and greased up as above. 

Now it's time to clean up those hands --- they're probably too messy now for just paper towels and may require a trip outside to rub them in the grass or on the family sheepdog.  Perhaps a trip to whatever room has the Lava soap is your safest bet.

Now the bottom shell of the rotator, perhaps now well cleaned up and freshly painted, is ready to be mounted back on the complete assembly.  There doesn't seem to be any particular way to mount this, besides making sure the 6 bolt holes line up, but you will probably need to manually push the brake wedge back in so the shell fits down easily.  I'd also be careful not to rattle the whole thing around too much to make sure the last two bearing races stay in place.  Once the bottom shell fits against the top bell housing, you can place the bolt, lock washer, and nut in each hole and tighten things up.  How tight?  Well, I wouldn't try to tighten them right after I had a 20 oz steak but I try to remember that they're going to be up there where I'm not........... and have no intention of going.......... EVER, so I get them good and tight.  The ears on a Tail-Twister case don't seem to be a such an angle that overtightening might break one off but I try to be somewhat gentle....... in a rugged sort of way.

Email to: k5lad@arrl.net

Created April 12, 2008      The page was updated on 10/01/09 04:56 PM

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