Simple question, not so simple to find answer?
Simple question, not so simple to find answer?
(OP)
Question: I am wondering why the bases of the large wind turbines I toured recently had something like 64 large, "left hand" thread bolts in the base. The tour guide did not know, but he did say they were torqued to something like 2000 lbs. Why the '"left hand threads?
Thanks,
George
Thanks,
George





RE: Simple question, not so simple to find answer?
I find some threaded rebars are available in left/right threads so you can match two end-to-end and thread a coupler on them without rotating the bar. But if they're available in both orientations, I can't think why you'd use left-handed for anchors.
I found one link that mentioned certain bars were threaded left-hand so they could be screwed into soil or rock and were apparently threaded left-handed to match other equipment used, "together with a lefthand thread for standard rotary percussive drilling".
RE: Simple question, not so simple to find answer?
Maybe its just as simple as you suggested.
"When you go looking for problems, you will find them... They may not be the problems you went looking for!"
RE: Simple question, not so simple to find answer?
"Dayton Superior offers anchor bolts in Grade 75 (W6), Grade 95 (W9) and 150 ksi (W3) strengths ...Bolts are available in #6 to #24 sizes...All bars have left-hand thread. Bars are fully threaded and available in any length up to 60 feet."
The threads in question are not a conventional bolt-thread pattern.
I just now sent an inquiry in to them to ask, see if we get a response!
RE: Simple question, not so simple to find answer?
"When you go looking for problems, you will find them... They may not be the problems you went looking for!"
RE: Simple question, not so simple to find answer?
In a situation where neither threaded pipe end can be rotated to tighten/loosen the joint, e.g. in traditional heating pipes running through multiple rooms in a building. In such a case, the coupling will have one right-handed and one left-handed thread
http://en.wikipedia.org/wiki/Screw_thread
I just don't know exactly how they make the rest of that connection.
RE: Simple question, not so simple to find answer?
http://en.wikipedia.org/wiki/Precession_%28mechani...
"When you go looking for problems, you will find them... They may not be the problems you went looking for!"
RE: Simple question, not so simple to find answer?
RE: Simple question, not so simple to find answer?
i can't see it myself ... why not RH threads with a locking feature (if there is some loosening effect from loads)
but it is a tricky design ... how to make sure they don't strip the buried thread ...
Quando Omni Flunkus Moritati
RE: Simple question, not so simple to find answer?
Cheers
Greg Locock
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RE: Simple question, not so simple to find answer?
https://www.google.com/search?q=post-tensioned+anc...
RE: Simple question, not so simple to find answer?
RE: Simple question, not so simple to find answer?
RE: Simple question, not so simple to find answer?
Never having been present at the building of such a base, I cvisualize how the process is actually performed.
"When you go looking for problems, you will find them... But they may not be the problems you went looking for!"
RE: Simple question, not so simple to find answer?
Note that none of these bars are furnished in left-right stud-type configuration, where one end is threaded one way, the other end the other way. It's one direction or the other the full length. The threads are already a non-standard configuration, it would seem, so little issue of a nut mix-up.
RE: Simple question, not so simple to find answer?
"When you go looking for problems, you will find them... But they may not be the problems you went looking for!"
RE: Simple question, not so simple to find answer?
RE: Simple question, not so simple to find answer?
ASTM F1554
I believe there are three grades, and the washers and nuts also have to meet the grades... thus .....
"ASTM F1554 is the newest construction fastener specification developed by the American Society for Testing and Materials and covers steel anchor bolts intended for anchoring structural supports to concrete foundations. Chemical requirements, mechanical properties, and dimensional tolerances are all covered under the F1554 specification"
Charlie
www.facsco.com
RE: Simple question, not so simple to find answer?
RE: Simple question, not so simple to find answer?
RE: Simple question, not so simple to find answer?
Here is one explanation I have been able to find.
http://www.pat2pdf.org/patents/pat20090044482.pdf Link
"When you go looking for problems, you will find them... But they may not be the problems you went looking for!"
RE: Simple question, not so simple to find answer?
But someone else just mentioned that you can tighten the bolt without it coming loose in the resin used to secure the anchors in the cage. So maybe I don't know.
"The "Kelislipped" Anchor is installed in the usual manner. The nut can be wrench tightened by hand without risk of rotating the anchor within the cured resin."
I'll just read then, but it's a fun post
Charlie
www.facsco.com
RE: Simple question, not so simple to find answer?
I think I get the post-tensioning principle, but I've no experience in the civil sector. Just guessing that the tooling that actually installs it is standardized to have the RH thread in the machine, and the LH thread on the anchor. Then just drive the anchor nut and everything gets tighter as you go...
So, how do the post-tensioning machines work anyway?
STF
RE: Simple question, not so simple to find answer?
http://www.windfarmbop.com/tag/bolts/
Charlie
www.facsco.com