Bent probes and cavity a no-go and CNC Machinist


  • Bent Probes and cavity a no-go and CNC Machinist

Last week I was up at the university and tested the bent probes.  The results were bad enough that I didn’t record any results.  The problem is that there doesn’t seem to be much of correlation between what is expected and what is measured.  Worse, I don’t know why.

To move forward, I have to step back to simpler cavities and make sure I can create cavities that match measured results to simulations.  Once there, I can then make and test incremental changes, until I arrive back at the original shape with all the improvements necessary.

Making the cavities by hand, i.e. folding copper into a tube, isn’t an option because I can’t get enough precision.  Using 2.45Ghz requires using cavities that are on the order of the wavelength at that frequency, which is roughly 10 to 12cm or larger (depending on propagation in free or enclosed spaces).  A crappy metal lathe starts at $600 ( – I like the word “Metal Worker” on the side 🙂 ) and a good one goes for a few multiples of that.

Simple small tube cavities are easy on a manual lathe, but eventually, making large asymmetrical ones, which are at the heart of the EMdrive, requires a CNC controlled lathe.  Second hand CNC lathes can be had for about $12K and up but require 220V or 480V and require knowledge about the controllers.  I have neither the knowledge, money, electrical power or space in my garage for such a beast.   Because all the cavities are one-offs and can be large, local machine shops won’t touch them, as I found out when trying to get the $2K cavity built (I think I contacted ten different machine shops).   The cavity is large enough, 280mm dia. at the large end, that it is outside the build envelope of a lot of lathes, and the larger lathes that are capable are all tied up doing more valuable work.   Ordering from is too slow, as the lead time is months and I want to iterate through cavity designs weekly.

I have decided to kill a few birds with one stone by becoming a CNC machinist, my third career.  My first career was a design/marketing engineer at a small BC company, my third was Levitee research, which I haven’t given up, and now a machinist.  I have been working on research now for ten years, four of which was Levitee specific, slowly burning through my savings ($30K left!!).  I also need to again start saving for retirement.  Again?  Yes, I was fortunate enough to have enough money from my first job, and willing parents, to “retire” at the age of 28 when I started down this crazy path. I need to turn on the money faucet once again.

The three birds I will kill with one stone are – learn how to be a CNC machinist, make cavities and money.

The good news is that there is a solid demand for CNC machinists in Edmonton, in large part, thanks to the oil industry.  To that end, I have, through a friend, applied at a local company which has some CNC positions open and without much surprise, they are reluctant to hire me.  To overcome those fears and because I don’t know anything about machining, I have now enrolled in an evening/weekend CNC machinist training course at NAIT and should be done by May 12th, 2012 (costing roughly $2K and 200 hours in time).

On the Levitee front, a few things did get done, for example, I received the Signalhound and I bought cables for Neil.  I plan to be up at the university next week to test the Signalhound against a more expensive spectrum analyzer to give Neil a better idea of the differences.  Things are still moving forward, even if I have to take a side step at this point.  Besides working with Neil to get the magnetron feedback loop working and simulating test cavities, things will slow down.