There are different time machines in Steven Gibbs report, like TA-30, STM, STR, Space Time Portal, Quartz Crystal and so much more! I don' even know if they work because i did not test them yet. But let me tell you that the most effective time machine is your mind, try to devepop your mind skills and you will achieve what you desire.
My mind has been filling with idea's for inventions to travel in time and space (and i'm sure many imagine ways to do so as well), yet the one of the things MetaMatrix said, is actually something that fits a theory in my mind that i have not shared yet, long as i can remember anyhow, i could be wrong) Anyhow the Quartz Crystal, something which can act as a clock pulse for a microcontroller chip, or rather a "PIC" chip, is actually something that does give an ability that , i feel , has the source which can be used for a device of interdimensional space/time travel. A much more accurate one to use though, would be an "atomic clock" , yet like with all inventions, there are many methods to create an invention. a person travelling down a road in a car, compared to one riding a bicycle, would still be viewed as using a similar invention as the bicycle rider, there are many differences , not only in how both inventions are designed, yet also the abilities and strengths that both have against compared to each other.
my point is, part of what is within my imagination, is that, there is an answer within these clock devices. Everything seems to be observed or read, through waves, or pulses , of energy . a clock pulse source, such as that of an atomic clock, quartz crystal, or even a home made oscillator , such as using a Capacitor and Resistor together, ... can all be used to create pulses, or waves (of course many other sources can too, ) , the point is, i feel these are most important , for some sort of dimension travel invention.
the atomic clock, would be more accurate, yet a quartz crystal, is still creating a count pulse within space/time.
there is something within the reaction of these particles, that scientists, have not become aware of yet, perhaps, ... i think anyhow, a reaction which can be used to open gateways to other dimensions.
anyhow i will stop talkin before i talk forever.
peace all.
and ya, if one creates any time / dimension travel devices, it is doubtful they would sell it. And as was said, they would disappear to another dimension, yet if they did, there's a chance a double would return .
any with such a device, would most definitely be taken by governments.
alrighty peace all