Re: Treenails??

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Mddeming-at-aol-dot-com>

Hi Erik, Gary, Gang (Y'All) 
In a message dated 4/5/01 12:21:02 PM Eastern Daylight Time, tesla-at-pupman-dot-com 
writes: 



>
> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>" < 
> Gary.Lau-at-compaq-dot-com> 
>
> There is no reason to avoid the use of metal screws.  I had performed an 
> experiment where I observed the ringdown time of the primary, with no 
> secondary.  A faster ringdown time would indicate that losses were occuring. 
> I did observe a faster ringdown time when large metal objects like NST's or 
> shorted strike rails were brought within a foot or so of the primary.  But I 
> could take a handful of metal screws directly into the center of the primary 
> with no observable change in ringdown times. Save a tree and save yourself a 
> lot of trouble. 



I see the real problem with metal screws as being one of providing added 
unseen current paths. If you are using wooden platforms and the wood is not 
perfectly dry internally, then running a metal screw into at two places 
provides a high resistance, but still conductive pathway. The more structural 
metal you have, the more places you provide for something to jump out and 
bite you.  I prefer either dowels or nylon screws, nuts, washers, even 
threading holes in plastic for nylon machine screws. Where a metal connector 
is needed for structural reasons, I use 3/8" all-thread inside PVC 1/2" pipe 
with PVC pipe caps over the locknuts. Wooden pegs and plastic connectors are 
just a little more insurance. (The necessity of accident insurance and how 
much is a philosophical question that may be off-topic.) 

>
> There was a thread on this List about a year or so ago, where someone had 
> reported that a shorted NST secondary could release a high voltage shock 
> after the short was opened.  In theory this could happen.  If the secondary 
> was shorted at the time of peak current flow and that energy stored in the 
> magnetic field of the secondary, the energy could in theory persist for an 
> observable period of time.  With NST secondary inductance in the thousands 
> of Henries and winding resistance of a few KOhms, the L/R time constant 
> could be a couple of seconds.  I tried to replicate this by shorting the 
> secondary with power applied, them immediately removing power and opening 
> the short into a small NE-2 neon bulb, but was unable to see anything 
> happen. 



I can't imagine an NST of that size. My 15/60 has XL~V/I =15000/0.06=250,000 
ohms and R=4800 ohms. 
Since L=XL/2pif ~250000/377=663Hy, ==> L/R = 663/4800=138 millisecs., it's no 
wonder you didn't see anything. Even a 15/30 would only have L~1326 Hy so a 
time constant beyond 300 ms seems very unlikely. 



>
> Gary Lau 
> Waltham, MA USA 
>
> >Original poster: "ebyng by way of Terry Fritz <twftesla-at-uswest-dot-net>" 
> <ebyng-at-netlimit-dot-com> 
> > 
> >odd topic, hmm? 
> > 
> >here we go.. 
> > 
> >I read and have held firm to the "do not use metal screws in tesla coil 
> >construction".  If any of you have built boats or have looked into that, 
> >you know what this is about.  For those of ya'll who dont, a treenail is 
> >the 1600-1700's answer to the nail.  Its basically a piece of dowel with 
> >slits  sawn into the wood about a 1/2 inch long, both ends.  you would then 
> >drill a hole in which ever pieces of wood you were going to join, and then 
> >place wedges into both of the slots.  with the wedges still in, you would 
> >lower the dowel into the hole and hit it into place with a mallet.. 
> >When the wedges were hit, the ends of the dowel would expand, acting like 
> >the treads of a screw... 
> >



Treenails may be somewhat overkill, but their presence in a project of today 
indicates a pride of craftsmanship that I can relate to. 


>
> >Get any of that?? 
> > 
> >good. 
> > 
> >So, could they be used to hold together the base/table for the primary?? 
> > 
> >Why not screws, btw, and what are YOU useing?? 
> > 
> >second section.. 
> > 
> >has anyone ever known/heard of NST's retaining charge after their 
> unplugged?



I think only those with an internal PFC Cap would be capable of biting. 
>
> > 
> >Thanks 
> >Erik



Lightning in the mountains, 

Matt D.