strength of old buzzard glass ant insulators vs. imported ceramic from china

[N3DRB The Derb]

just curious - most of the old buzzardly glass ant insulators were made with Pyrex or borosilicate glass. how does this compare in strength to typical ceramic jobs imported these days? I am going to freshen up my "temporary" antenna while it is down with new insulators, weatherization job, and redoing all the splices in the ladder line. I got 2 clear glass and 2 jumbo "square egg" white glazed ceramic. I don't like nylon or plastic stuff, even though it works well enough,  I just don't like em.

I'm going to shoot the other end back up with a cheap 30# bow. Thinking one of the 'square eggs' in the center and the 2 glass jobbers on the ends. They're about 4 " long.

[k4kyv]

I've had both to break.  I use the 8" long pyrex ones on my beverage antenna.  Overkill, but that's what I have on hand, and the wire is #8 copperweld, so it takes a good husky insulator to hold up 900 ft. of it.  When I was putting up the extended section for winter last year, I suddenly lost tension when I tightened up the wire using my ratchet puller.  Went to investigate, and found that one of the pyrex insulators had pulled in two right at the eyelet.  I  replaced it with another one and had no more problem, but I was careful not to overtighten the wire.

I use the little 3" dog-bone insulators to hold the open wire line to my dipole.  Two at the bottom and two at the top, and maintain tension with a couple of small turnbuckles.  The open wire line and antenna are made using one solid piece of #10 copperweld on each leg.  Last winter (or maybe year before last) we had an unusual cold snap compared to our wx for the past 10 years.  I fired up the  rig and it wouldn't load up.  When I investigated, I found that one of the dog-bone insulators at the bottom of the open wire line  had pulled in two, evidently when the temperature dropped, the wire contracted and exceeded the tensile strength of the insulator.

I "temporarily" repaired it by wrapping several turns of some Philistran scrap I had lying around, to form a  makeshift insulator.  So far I haven't attempted to permanently replace the insulator, since the makeshift job seem  to work FB OM.

[N3DRB The Derb]

glass ones seem to be prone to failure right where yours broke, where the eyelet joins the ribs. There's good ones, where the glass is very thick at that spot,  and others where it tapers too far down. Knox seem to be a good brand with thick glass everywhere you look. of course he cool ones are the ones made of colored glass (for looks anyway).

I'm concerned the quality of the chinese ceramic will be spotty, like everything else made in that country is. I don't trust anything made in china these days.

[Ed/KB1HYS]

Avoid insulators with thin necked areas, These are stress concentrators. Some of the cheap ones have deep machined groves to improve voltage resistance, unless the grove has a decent radius at the bottom, it will act like a scribed line in some cases.   With glass, scratches and surface damage can effect tensile strength of the sample, by concentrating the stress at the damage point. Ceramic should behave similar (or better) to glass unless it's some exotic blend.  Glass reinforced plastic insulators should work well, depending on UV sensitivity of the material/finish.

Wires should never be pulled taught, there should be some sag, to provide relief due to temperature changes, wind and such.  From a mechanical standpoint it is better to add a sliding support, like a pulley, in the middle of a long run than to try to pull it up straight by tension alone. Some folks use the counterweight method to keep an antenna straight.  Works ok, but in some conditions the inertia of the weights can break the line just as if it was a fixed attach point.  Heavy springs like for screendoors might be better. I've never tried dynamic support for my ants.  I just leave some sag in them and use nylon line as halyards for a little flexibility.  When those big pines flex in the breaze there's movement, but nothing gets pulled too tight.

My 0.02 cents worth...

[N3DRB The Derb]

I'm gonna have to buy some of that black dacron rope too. I guess it's all still up in the tree, I never did find it.

gotta go back down to dad's for 2 days. I cant get anything done these days. I'm being shuffled around too much.   

[Todd, KA1KAQ]

Derb, beware of the brown ribbed (ewuh) ceramics sold on ebay. Some guy sells them 10-12 in a bunch for $9.99. They LOOK great, feel heavy, and break easily. Gave a couple to a buddy who used them on a dipole, witnessed him *clack* the insulators together as he set it down rolled up. Not hard either. One broke. When he set it back down after examining it, the other broke. Neither impact was at all hard, the insulators are just very brittle, soft ceramic, something.

I doubt they'd even be safe to use for a SW receiving wire for any length of time - assuming you could get the thing in the air without one breaking. I thought they were surplus, obviously imports.

Never had a glass or Pyrex one break. Yet.

[k4kyv]

Wires should never be pulled taught, there should be some sag, to provide relief due to temperature changes, wind and such.  From a mechanical standpoint it is better to add a sliding support, like a pulley, in the middle of a long run than to try to pull it up straight by tension alone.

For my beverage, I use some of the smaller size pyrex inslulators for intermediate supports.   But I use them as vertical supports.  I simply thread the wire through the eyelet at one end, and use a piece of wire between the overhead support and the eyelet at the other end, and the insulator just dangles down.  That way, the wire can slide freely to and fro through the eyelet as tension varies along the wire with temperature and wind conditions.  For the rigid conduit or water pipe support poles I use in some points along the way, I use a 6" long, 1" thick round EF Johnson ceramic end-insulator.  Again, the antenna wire is fed through the eyelet at one end of the insulator, and for the other end, I use a stiff, heavy piece of galvanised wire, about #8, through the eyelet, and fold each end back so that the insulator and wire are inserted about half its length into the pipe, then the wire is bent back and down over the exterior of the pipe.  For good measure I then wrap another piece of wire over the ends of the wire to hold the wire basket in place.  The eyelet of the insulator peeks out of the pipe  far enough to accommodate the antenna wire, while keeping it a safe distance  from the pole.  I have used this for about 5 years now, with no problem.

[Ed/KB1HYS]

That way, the wire can slide freely to and fro through the eyelet as tension varies along the wire with temperature and wind conditions. 

Quite right. There has to be some play in a system otherwise something HAS to give, and not usually what you had planned or wanted.

[Steve - WB3HUZ]

Never had one of these break.

[N3DRB The Derb]

where'd you get that puppy from? looks good to me. I like that shape for ends because they slip though the branches better me thinks.

[WA1GFZ]

I use the old Johnson 8 inchers. I broke one when I dropped it on concrete.

[N3DRB The Derb]

I thought they were surplus, obviously imports.

yeah, thats what I'm scared of. Going to a fester and buying what LOOKS like scroteful jobbers but they sux because they made for greater glory of China by prison labor.

I think I'd rather go vintage glass.

[Steve - WB3HUZ]

Radio Works. Warning, it is plastic.  But a big, tough mutha, about 6" long. I've used several of these on numerous antennas for over 20 years. Even had one that sustained some zorches when the end of the antenna shorted on some tree branches. The thing is still useable though.

where'd you get that puppy from? looks good to me. I like that shape for ends because they slip though the branches better me thinks.