HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Feb 12, 2009, 06:19 PM
Dragon
mech9's Avatar
Vancouver B.C. Canada
Joined Sep 2004
216 Posts
Dag,
That drawing of your air tanks in the fuse looks great, brings to mind putting fins on them and mounting them in the bomb bay.

Cheers.
mech9 is offline Find More Posts by mech9
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 12, 2009, 07:04 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
San Jose, CA
Joined Jan 2008
28,030 Posts
Hi Chickenthief...

Quote:
That theory only applies for AC Just look at the transformer in Your welder, it's solid wires! Wireing in houses are also solid. The sole reason for mulitstrand wires is flexibility
Sorry...not true... I was an electrician for more than 25 years. Most houses are wired with solid wire due to ease of "make-up". But you also must understand, when you pull AWG 14 or AWG 12 gauge wire in a home, you are only pulling up to 15 or 20 amps, while in our models, you are pulling much more amperage over the same size of wire. If you try pulling 65 amps with AWG 12 wire (especially solid), you will melt it, yet we do this all the time with the multi-strand wire we use for our planes.

As to the welder, yes the coils are solid copper, but they are also very large diameter copper, and a larger diameter also has more surface area...

Besides....current is current, whether AC or DC, the only difference is that one flows only in one direction,(DC) while one changes direction at 60 cycles (U.S.). It;s all coulombs flowing ON the surface of the wire, not through.

SteveT
SteveT. is offline Find More Posts by SteveT.
RCG Plus Member
Latest blog entry: My hangar...
Reply With Quote
Old Feb 12, 2009, 08:09 PM
X-Era Motors
DavidB.'s Avatar
Newport, NC
Joined Jan 2002
2,225 Posts
Quote:
Originally Posted by Draknkep
Dag, I`m sure you know this, but for those that don't, electrical current does not actually flow "through" the conductor, but rather on the surface of the conductor, this is why multi-strand cable is able to carry more current than solid wire can.
Only in super high frequency AC applications is this true. DC couldn't care less how many strands are there. Welding cable is high strand because the welder needs complete control over the weld bead..and stiff cable doesn't help.
DavidB. is offline Find More Posts by DavidB.
Reply With Quote
Old Feb 12, 2009, 08:17 PM
War Eagle!
sneasle's Avatar
United States, AL, Huntsville
Joined Sep 2006
2,923 Posts
Quote:
Originally Posted by Chickenthief
That theory only applies for AC
Just look at the transformer in Your welder, it's solid wires!
Wireing in houses are also solid.
The sole reason for mulitstrand wires is flexibility
Thank you for stopping that before it got any further.

"Skin affect" Applies to only higher frequency signals.


Dag:

Let em know the weight when you can. If if is light enough and if you end up with some extra I might take it off your hands.
sneasle is offline Find More Posts by sneasle
Reply With Quote
Old Feb 12, 2009, 08:20 PM
War Eagle!
sneasle's Avatar
United States, AL, Huntsville
Joined Sep 2006
2,923 Posts
To clear this up once and for all, the AWG table for wire sizes:

http://www.powerstream.com/Wire_Size.htm
sneasle is offline Find More Posts by sneasle
Reply With Quote
Old Feb 12, 2009, 08:50 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
San Jose, CA
Joined Jan 2008
28,030 Posts
Not to argue this any farther....but try using a piece of "romex" type house wire, and pull 65 amps (I.E. a mid range electric plane motor) and see how long it lasts...

Ok... I'll shut up now...

SteveT
SteveT. is offline Find More Posts by SteveT.
RCG Plus Member
Latest blog entry: My hangar...
Reply With Quote
Old Feb 12, 2009, 09:26 PM
X-Era Motors
DavidB.'s Avatar
Newport, NC
Joined Jan 2002
2,225 Posts
Wire resistance is a function of cross sectional area, you can look at the link below. Skin depth is only applicable in VERY high frequency AC systems.

http://en.wikipedia.org/wiki/Electrical_resistance
http://physics.bu.edu/~duffy/PY106/Resistance.html
http://hypertextbook.com/physics/ele...ty/resistance/
http://knowledgerush.com/kr/encyclop...al_resistance/
http://www.blurtit.com/q331026.html
http://hyperphysics.phy-astr.gsu.edu...ric/resis.html

These are solid copper.

http://en.wikipedia.org/wiki/File:Busbars.jpg
DavidB. is offline Find More Posts by DavidB.
Last edited by DavidB.; Feb 13, 2009 at 02:58 AM.
Reply With Quote
Old Feb 13, 2009, 02:43 AM
I fly, therefore, I crash!!!
SteveT.'s Avatar
San Jose, CA
Joined Jan 2008
28,030 Posts
Hmmmm....

So, do you really think that the many 1000's of feet of 250mcm, 500mcm, 750mcm, 1000mcm (better known as 1 mil), and even 2000mcm (better known as 2 mil) stranded cable that I have pulled in 25 years as and electrician working on power houses, foundries, and other large factories such as the Boeing plant in Everett, Washington where they build the 747s, and 767s, would have worked just as well if they were solid soft drawn copper??? I doooooonnnn't tink so.....

And...those busbars that you are referencing are only 1/4" to 3/8" thick by about 3" to 4" wide...so just how much surface area do you think they have?? And you notice that they have multiple layers for each bus..gee....more surface area... The Caterpillar Foundries in Mapleton Il.(which I helped build), also have busbars (which I helped to install), carrying 13,800 volts to their induction furnaces....they aren't big honking thick bars, they are 1/2" thick by 12" wide....again, for more surface area...

But....this is not my thread, and I'm sorry for thaking it off track, so... back to Dag's wonderful plane...

Dag, your aluminum sheeting is looking great, as I have said before, this will be and amazing plane when finished..

SteveT
SteveT. is offline Find More Posts by SteveT.
RCG Plus Member
Last edited by SteveT.; Feb 13, 2009 at 03:15 AM.
Reply With Quote
Old Feb 13, 2009, 02:58 AM
X-Era Motors
DavidB.'s Avatar
Newport, NC
Joined Jan 2002
2,225 Posts
Updated my post with more links. If you still think somethings fishy we can talk about it in emails. No point muddying this up further.
DavidB. is offline Find More Posts by DavidB.
Reply With Quote
Old Feb 13, 2009, 03:12 AM
I fly, therefore, I crash!!!
SteveT.'s Avatar
San Jose, CA
Joined Jan 2008
28,030 Posts
The majority of the threads you have listed are all talking about resistance, this has nothing to do with surface theory, there can still be resistance on the "skin" of a material...Sorry, you're not going to convince me otherwise, so as you said, lets not continue this here...

SteveT
SteveT. is offline Find More Posts by SteveT.
RCG Plus Member
Latest blog entry: My hangar...
Reply With Quote
Old Feb 13, 2009, 08:50 AM
Its all fun
Tonystott's Avatar
Australia, NSW, Forster
Joined Oct 2004
7,210 Posts
Guys, get a room eh?
Tonystott is offline Find More Posts by Tonystott
Reply With Quote
Old Feb 13, 2009, 02:55 PM
RCHN #150
Rickn816's Avatar
Lawrenceville, GA
Joined Nov 2007
5,997 Posts
Quote:
Originally Posted by Chickenthief
That theory only applies for AC
Just look at the transformer in Your welder, it's solid wires!
Wireing in houses are also solid.
The sole reason for mulitstrand wires is flexibility
High frequency AC.
Rickn816 is offline Find More Posts by Rickn816
Reply With Quote
Old Feb 13, 2009, 03:26 PM
War Eagle!
sneasle's Avatar
United States, AL, Huntsville
Joined Sep 2006
2,923 Posts
On the bright side, at least it is a technical argument?
sneasle is offline Find More Posts by sneasle
Reply With Quote
Old Feb 13, 2009, 04:07 PM
Crafter of flying plugs
Owen Hedger's Avatar
Armidale, NSW
Joined Feb 2007
1,238 Posts
http://en.wikipedia.org/wiki/Skin_effect

In copper, the skin depth at various frequencies is shown below.

frequency d
60 Hz 8.47 mm
10 kHz 0.66 mm
100 kHz 0.21 mm
1 MHz 66 Ám
10 MHz 21 Ám

So as the frequency goes up the skin depth get shallower. So even at 60Hz skin effect depth is 8.47mm.

"In Engineering Electromagnetics, Hayt points out that in a power station a bus bar for alternating current at 60 Hz with a radius larger than 1/3rd of an inch (8 mm) is a waste of copper, and in practice bus bars for heavy AC current are rarely more than 1/2 inch (12 mm) thick except for mechanical reasons."

Does the touching surfaces in a multistrand cable still count as 'skin'?

Brushless ESC's are switched 10's of KHz but are they switched to produce AC?
Owen Hedger is offline Find More Posts by Owen Hedger
Reply With Quote
Old Feb 13, 2009, 05:05 PM
Registered User
Angelo's Avatar
Chicago, IL
Joined Nov 1999
2,081 Posts
Owen, you may be great, but if you're going to quote sources, Wikipedia is not the way to go. ANYONE can go in and edit a listing, hell, I could go in right now and re-write it to say that depth is what matters. Some one else might see that and fix it. Then again, maybe not.

"Wikipedia, the triumph of democracy over truth."
Angelo is online now Find More Posts by Angelo
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Good B-36 site (drawing with cross sections, too!) Thomas B Scale Kit/Scratch Built 26 Oct 11, 2011 10:14 PM
Discussion B-36 B-52 kgmorris Scale Kit/Scratch Built 20 Jan 02, 2009 07:27 AM
b-36 dorysch1 Scale Kit/Scratch Built 32 Feb 01, 2004 09:33 PM
Questions about my wally B-36...I'm new to foam. Boba_Fett Foamies (Kits) 8 Jun 11, 2002 04:36 PM
B 36 Trobber Parkflyers 3 Dec 30, 2001 01:33 PM