On 10/14/2011 6:21 AM, Jim Thomson wrote:
> I think a Sleeve bearing would have been better still.<:-))
>> ## so far, on the new HDX-689 tower, the PEER brand thrust bearings, with
>> their locking collars works good.
>> The set screw for the locking collar has to be slopped with never seize
>> goop though....and also more goop to be
>> applied to the female thread.
>> ## Thrust bearings are not easy to replace..after the fact.
> That's what makes the wood and other split blocks so nice.
>> The Rohn bearing's are not only expensive, they are poor value
>> for the money, and poorly designed. If u do use the TB3/4's... add a zerk
>> fitting, so at least u can pump it with grease
>> once or twice per year.
> I'm not sure if that will make them last any longer, but it will make
> them run smoother.
> Roger (K8RI)
> ## Roger, if you want things to go smoothly, start with the mast. Use
> either a quality 87 ksi DOM mast...
That's what I'm using with the exception of lighter loads and there I'm
using 2" 6061T6 with a 1/4" wall.
> a heat treated 4130 chromolly mast [ 107-120 ksi]. Either way, make
> sure they are hot dipped galvanized.
> Ok, no rusting masts. On my HDX-689... they not only use a PEER brand
> thrust bearing at the very top, I also have
> a 2nd identical thrust bearing down aprx 4'. On the UST 689 tower, they
> also use a.. 'sleeve bearing', just below the
> top plate/bearing. This 2nd plate is aprx 6" below the top of the tower. A
> section of pipe with an ID that's a tiny bit bigger
> than 2" is welded into place..and runs between thrust bearing plate at top
> of tower..and down 6" to 2nd plate . Both the top thrust
> bearing plate and the 2nd plate are welded to the tower legs. [ the lower
> thrust bearing + prop pitch plates are bolted into
> place, so 4 x plates in all]. That short 6" sleeve pipe has nuts welded
> to it, and 3/8" bolts. Their purpose is to pin the mast,
> when working on the rotor. IE: mast is temp elevated 12"-18"...and
> 3/8" set bolt through the sleeve bearing stops the mast
> from free wheeling about.
> ## although both PEER brand bearings spun smooth, I replaced em both on
> spec with new ones, since the tower is old, and the
> bearings were not too expensive. I had no problem getting the locking
> collars off either thrust bearing either. They provide an
> indented hole on the locking collar to tighten the collar...with a few
> smacks CW with a drift punch. The 2nd hole on the locking collar
> is for the big set screw. As long as the set screw and mating female
> thread on the collar are glopped with plenty of never seize
> [ marine grade is the best version], you will never have a problem with em.
> ## I did have to replace the bad bearing on the end of the big rotor drum
> though. the bearing was just fine, but the base had 2 x cracks
> in it, right where the 5/8" bolt pass's through one end. [ both drum
> bearings and thrust bearing are 2 x hole mount]. The bad bearing
> had to be cut off, since it seized on the 2" solid shaft. After it was cut
> off.... I could see the insides of those things are built like a tank !
> ## both drum bearings are the self aligning type, they will swivel a bit,
> and factor in any mis-alignment. Now you think the thrust bearings
> have some kinda big side load on em in a high wind, wait till you see the
> side load on a 2" drum bearing ! Yikes, the entire weight of the
> tower + mast/rotor/ants is on that lift cable [ with a 4:1 mech
> advantage]... and the drum bearings are taking all the load.
Good place for roller bearings instead of ball bearings. <:-))
> Note, the very bottom tower section is sitting on concrete, so is not part
> of the drum bearing load. Note, the ID of the drum bearings is a hair
> less than 2"..while both thrust bearings have an ID that is a hair bigger
> than 2". The drum bearings have a thicker base and are self aligning.
> I checked peer's website..and no reason why u can't use their standard 2"
> self aligning bearing for a thrust bearing, at top of the tower, or
> their normal bearing [ no self aligning]..but with a thicker base.
Which I probably will in some instances.
> ## in the case of the UST towers, it's sorta a moot point, since that
> huge 6" sleeve that's welded between two plates is the ultimate ticket.
> [ Plus both those plates are welded to tower legs. ] Between the sleeve and
> the top thrust bearing, it will handle a massive side load.
> ## On the bottom thrust bearing [just above the prop pitch] I don't use
> the locking collar per se. I slide the locking collar up the mast 2", then
> lock it.
> This allows the mast to free float in the lower thrust bearing.
Good idea to prevent loading due to expansion and contraction due to
> I feel more confident [ and safer] when working on the PP, that the mast
> is supported
> by the top thrust bearing/sleeve/then the lower thrust bearing.
I use two sections of DOM masting with a 16" long coupling that fits
over the masting. Recesses are drilled into the masts, but only deep
enough to prevent the bolts from slipping.
A sleeve large enough to take an intermediate size piece of DOM split
length wise can be dropped into this. It holds the split piece in place
with the bottom serving as a stop while the bottom of the coupling rests
on the top of the split piece. Normally the split pieces are in the
shop, or would be if I had that back up. That "will be" the system that
has the 3 or 4L 40 and 7L C3i 6-meter Yagi at 100 and 115 feet when it
goes back up. It goes in place of the array I've posted photos of.
> [ + the mast is pinned via the bolt through the sleeve, only used when mast
> is elevated
> a bit, and PP is worked on. I ended up buying the UST mast raising
> fixture, which bolts to the 2nd plate [ 6" down from top]. That 2nd plate
> the big hole in it so the cable for the mast raising fixture just passes
> through it. A special 2 x piece clamp, clamps to the mast, and
> terminates on the
> mast lift cable.
> ## Everything is galvanized, nothing rusts,
Good except for composite or say Delrin sleeves where the rough surface
of the galvanizing can cause abrasion.
> bearings are built really good, everything has zerk grease fittings, and
> the small K7NV PP runs like a
> swiss watch, globs of TQ. BTW, you can also get grease fittings that have
> 90 deg bends in em..and also 45 deg and also 65 deg..and also straight.
I have boxes of them (used to farm) of not only the different angles but
different sizes as well. I don't really like the ones with the tiny
threads as they are quite fragile and can be broken off.
> I capped off the very top of the 2" x .375" wall chromolly mast. Then
> no water coming down the inside of the mast.
I weld caps on both ends of the tubes, usually a minimum of 1/8" but
prefer 1/4". I then drill and tap a small hole in one end. Then dump in
about a half cup of LPS2 for a 24' long by 2 or 3" tube and insert a
plug. The mast is rolled and tipped to coat the inside. Then the
threaded hole is welded closed. I do this with tower legs also. It's a
good idea to save this operation for last, after the welding has been done.
> The mast is also climbable.
> I gave up years ago with painting masts. On the galvanized chromolly
> mast.... I gave it a couple of coats of cold galvanize spray. That stuff is
> cheap, and works good. I have enough zinc on everything so nothing should
> rust. The cold galvanize spray sticks to the hot dipped galvanized
> parts very well.
Unfortunately I have not found any place than can hot dip 24' tower
sections that are 2 to 4 feet on a side.
> later....... Jim VE7RF
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