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Re: an interesting mechanical engineering problem

Original poster: Frank <fxrays@xxxxxxxxxx>

You want something that is easy to rig up/ tear down and does not have a lot of loose parts. Nuts and bolts are easy to loose, over torque, bang knuckles and require a lot of time to assemble/ disassemble.

You might consider something called a hammer union, http://www.fmctechnologies.com/FluidControl/Flowline/WingUnions/StandardService/Figure100.aspx This has a easy to mate, square thread and is fast, yet it makes a solid mechanical and electrical connection. Although this model is steel, you could contact the mfgr for a brass type if desired. As to the threads, a simple machining of the ends for a bevel prep could be done and then silver solder the copper to the steel, it will take fine and provide the mechanical/ electrical connection desired.
This union is cheap and could be a clean solution.

This thread profile could be duplicated in brass with a tubing profile for silver brazing at any machine shop as well.

To lubricate the threads and help prevent corrosion from ozone, use this lubricant: http://www.americawestdrillingsupply.com/products/details.asp?PDID=28 It is excellent and the micro copper flakes make it very easy to make up/ remove the connection as well as provide additional electrical conductivity.

Thanks, Frank

At 10:36 PM 1/10/2007 -0700, you wrote:
Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 03:45 PM 1/10/2007, Tesla list wrote:
Original poster: Tom Perigrin <tip@xxxxxxxxxxxxxx>

At 08:56 PM 1/9/2007, you wrote:
Original poster: Mike <megavolts61@xxxxxxxxx>

 You can't get cheaper and simpler than some saw cuts and
electrical tape.

-Phil LaBudde
(save your time and money for the IGBT's)

Although I'm a big advocate of going cheaply as possible, I'd have a problem with the visual asthetics of this idea when spending thousands on what is a showpiece.

I'd suggest getting a plug and socket made for each joint. The plug and socket would consist of a 4" OD taper by about 12" long. These should be accurately turned to be +/- 0.001 (or better). Then, get them gold plated with at least 0.005 of 24K gold. Also, there should be a mechanism like a pipe union that snugs the joint together.

That's a clever idea. Coarse thread, like a firehose coupling, you can put a wrench on it, pulls the joint together. In fact, you might look at firehose couplings.. 4", brass, etc.

I don't know about gold plating. It would work. You could also use silver plate. Silver oxide is still a fairly decent conductor.

Clean the joints with warm soapy water before each use, and make a protective covering for transport. That's not going to be a lot of gold..

If you use firehose couplings, there are plastic caps made that just fit.

Firehose couplings come in 2" through 6" and probably bigger. There are male screw threads that could be be brazed onto your conductors. The female side has a spinning clamp that pulls the mating surface into contact.

You can also get braze on fittings or ones with a pipe thread on the other side.

A standard firehose wrench has a nifty little hook that engages the pin sticking out of the side to give you some leverage for tightening.

There are also cam lock style couplings that have very high clamping forces at the join (to hold against the high water pressure in a 6" line, you need pretty high clamping force). I think Mcmaster calls them "cam and groove" connectors.

Best yet, they're all available (although not in the biggest sizes) from the tesla coiler's mail order friend, McMaster Carr. Check out page 209 in the online catalog.

I personally prefer the rocker lug over the pin lug for hoses (less sharp edges), but if you're using a spanner wrench, the pin lug might be better. You could put a hydrant plug (male thread) on one pipe.. braze it on, and a Male Adapter/Female Swivel or Female Adapter/Female swivel on the the other pipe. You might even be able to get the female Swivel all by itself.