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Sue VÍtements
11th Sep 2016, 23:45
This is probably going to be a short thread , unless there are several hundred "me too" responses, but I feel I have to say it's really VERY EASY:

Spiral: a two dimensional shape made of a continuous curved line proscribing a locus of ever decreasing (or increasing) radius

Helix: a similar shape but one that requires three dimensions and a constant radius with the locus traversing the third dimension at a uniform rate.



So if Helical Staircase is too poncy for you, try Winding Staircase, but PLEASE refrain from Spiral Staircase. Anyone unable to comply will be taken away and shot.



Incidentally, regarding the helical staircase, if turns are made to the left when descending, that is commonly known as a Defending Staircase. Why? Well think about defending it against an attack, (assuming you were right handed) you'd be able to swing a powerful blow to the attackers where as they would be reduced to the less powerful backhand maneuver.

:8

clark y
12th Sep 2016, 00:27
Sue, had to think about that for a while. Does a helix have to have a constant radius? If the answer is yes then what would the shape be as made by the thread on a tapering/self tapping screw?
My dictionary has multiple definitions of both. Helix has a spiral as a definition and vice versa.

Now if someone could tell me the technical difference between a bolt and a screw.

Hydromet
12th Sep 2016, 02:38
Clark Y, you never hear anyone boasting of having had a good bolt.

A helix that doesn't have a constant radius is called a conic or tapered helix (provided it would actually lie on the surface of a cone. It would also be possible to have a helix that lay on some other shape, say a paraboloid or hyperboloid. All could be described by a set of equations.
A conic helix is also sometimes defined as a 3-dimensional spiral that lies on the surface of a pyramid.

pattern_is_full
12th Sep 2016, 04:34
Sorry, Sue - but you are about 100 years too late. The "death" or "graveyard" spiral dates back nearly to the origin of (unmentionable subject on Jet Blast, involving wings).

And of course, if it was only confined to two dimensions, it would be a non-event. It's precisely and only that it occurs in three dimensions that leads to the names (and the resulting smoking holes in the ground.)

"Graveyard Helix?" Ernest K. Gann would spiral in his grave.

underfire
12th Sep 2016, 04:40
A tapered bolt/screw is helical...as you have a constant pitch rate.

For spirals, there are clothoid, bloss, sinusoidal, cubic parabola, cubic, half-wave diminishing, and bi-quadratic.

For aircraft flight, you have spiral-radius-spiral for a turn. The design uses a clothoid spiral to simulate the way an ac flies. This takes into account the beginning of the turn while the ac banks, pure turn, then spiral out with the bank.

As one can surmise, a turn in a final approach procedure, ie turning while descending, is quite the mathematical challenge! If it had not been for computers, I may have ended up as a pilot.

Would a lighthouse have a helical staircase?
http://eco-turizm.net/uploads/2014/04/The-Wonderful-Barn-Celbridge.jpg

VP959
12th Sep 2016, 09:15
As one can surmise, a turn in a final approach procedure, ie turning while descending, is quite the mathematical challenge! If it had not been for computers, I may have ended up as a pilot.

For a couple of years I flew a mid-wing taildragger with a low wing loading. Our local strip has a hill on the normal approach, and this can create a fair bit of turbulence. I got into the habit of doing a tight circuit and a descending, constant radius, turning approach.

I'm far from being a natural or good pilot, but for me this approach was a heck of a lot easier to judge than a straight-in approach. I think the main advantage for me was that I could just keep the inboard wingtip pointing at a reference as I made the approach. Some at the club reckoned I only did it to emulate the old single engined WWII fighters, who had to land like this because they had virtually no forward view, because of the big engine upfront. For me the only reason was that I found it a lot easier to maintain exactly the right approach speed and descent rate. Straight in landings in that aeroplane were, for me, often pretty untidy.

Not sure about the maths, for me it was just a matter of having a good reference by lining up the wingtip in the turn.

ORAC
12th Sep 2016, 09:33
Words have different meanings and connotations in different disciplines.....

https://thestaircaseexperts.wordpress.com/2013/10/31/the-difference-between-spiral-and-helical-staircases/

Falcon Al
12th Sep 2016, 10:08
I think we're helixing out of control here.

ORAC
12th Sep 2016, 10:10
Don't let yourself get wound up about it.

Falcon Al
12th Sep 2016, 10:15
Does a helix have hertz?

B Fraser
12th Sep 2016, 10:21
Now if someone could tell me the technical difference between a bolt and a screw.


Simple, screws are female and bolts are male. Screws have a slot and bolts have nuts.

Fitter2
12th Sep 2016, 10:44
At the risk of being boringly technical, the thread on a screw goes all the way to the head, a bolt has an unthreaded portion, useful for taking shear loads (although in a normal bolted joint the shear load is primarily taken up by the flat sufaces held by the tension in the bolt).

ORAC
12th Sep 2016, 11:02
http://cdn1.tmbi.com/TFH/Projects/FH00JAU_DRYSCR_02.jpg

Dont Hang Up
12th Sep 2016, 12:14
Yes ORAC, your self tapping wood screw is the exception that proves the rule!

But in the field of metalwork, I believe the appropriately named Fitter2 is correct. It is certainly what I was taught in my apprenticeship days (looking back 35 years now :eek:)

ORAC
12th Sep 2016, 12:47
http://aufaster.com/pic/big/168_0.jpg

andytug
12th Sep 2016, 12:54
Is it not that screws have a pointy end whereas bolts don't?

ORAC
12th Sep 2016, 13:05
No, tap bolts......

https://www.boltdepot.com/Metric_tap_bolts.aspx

http://www.portlandbolt.com/technical/faqs/tap-bolt-vs-cap-screw/

"...To summarize, a bolt is installed by turning a nut, while a screw it installed by turning the head of the fastener. A tap bolt implies that that fastener is fully threaded......."

Smeagol
12th Sep 2016, 13:05
" At the risk of being boringly technical, the thread on a screw goes all the way to the head, a bolt has an unthreaded portion"

But stud bolts ( for bolting flanges together) are threaded throughout their entire length.

Fareastdriver
12th Sep 2016, 13:35
A bolt has a nut on the end. A screw has an anagram of a nut with 'c'.

Fareastdriver
12th Sep 2016, 15:17
How do you tighten up an Archimedes Screw?

andytug
12th Sep 2016, 15:20
How do you tighten up an Archimedes Screw?

Anything with a large enough Eureka moment should do it.

DirtyProp
12th Sep 2016, 15:35
Where is Loose Rivets when you need him?

Dont Hang Up
12th Sep 2016, 16:10
Where is Loose Rivets when you need him?

Probably somewhere getting tight. ;)

andytug
12th Sep 2016, 16:23
Probably somewhere getting tight. ;)

Presumably he needs to get hammered first... etc

ORAC
12th Sep 2016, 16:54
Some people are just all torque....

andytug
12th Sep 2016, 17:00
Drives ya nuts, doesn't it?