Re: My first ARSG, or a Dangerous Design?

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

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

In a message dated 1/23/03 10:05:44 AM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:


>Original poster: "Scott Hanson by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <huil888-at-surfside-dot-net>
>
>Some time ago, when I saw the first proposal for a rotary gap based on this
>design, I cringed but refrained from making any comments.
>
>However, I feel that I must warn anyone who would consider this "makeshift"
>type of rotor that it is unquestionably the most dangerous design concept
>that I have ever seen proposed on the TCML. Please understand that this is
>not a personal attack on anyone who has conceptualized, designed, or built
>such a device; its just that this design is intrinsically incredibly
>dangerous, and is contrary to all conventions and design standards that have
>been established for high speed rotating machinery.
>
>The single greatest weakness in this design is in the attachment of the
>rotating electrode (tungsten rod) to the "hub". The only thing retaining the
>rod in the hub is friction, whether it is obtained from a press fit of the
>rod into the hub, or side load provided by a set screw, etc. The coefficient
>of friction between any plastic and a smooth tungsten rod is very low.


Hi Scott, Dan, Terry B, All,

OK here is some CONSTRUCTIVE criticism. IF there really is a problem of low 
coefficient of friction causing slippage, here is one way it can be easily 
cured:
1) Push tungsten rod through an externally taper-threaded piece of split 
brass tube, so that the tube is in the middle of the rod. The tube must be 
about 0.5" longer than the width of the hub. Hole in hub should also be 
threaded.
2) Thread tube with rod in it through hub.
3) Put a locknut on each end of tube to both lock rod into tube and hold 
tube locked into position in hub.
4) Balance and Run.
5) Naturally, all plastic parts subjected to rotational stress must be 
inspected periodically for wear and replaced when wear is observed. This is 
true for HDPE, Nylon, Lexan, or G10.

Without these modifications, even at 15,000 rpm, the tip speed of an 8" 
rotor is  ~524 fps. If the rod did start to slip out, it would impact the 
stationary electrodes before it could leave the hub. While this would most 
likely wipe out the rod, the electrodes, and the hub, it would be less 
dangerous than an airborne disk or tangentially-flying small electrodes. 
The design is very creative and hardly what I would call "makeshift".

Matt D.
"Fear precludes creative thinking" D. H. Martin III