Author Topic: Suggestions for forums for Vacuum Systems?  (Read 6583 times)

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Offline TerraHertz

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Suggestions for forums for Vacuum Systems?
« on: November 25, 2015, 02:59:33 pm »
Does anyone know of an active and informative forum (like eevblog) on vacuum system practices and materials?

Googling finds:

http://belljar.net/forum/
But registrations are closed, and the posting history reveals it to be a virtually dead forum, and has been for years. Possibly the owner's demand that people register using their real names may have something to do with that - there's no way I'd consider that an acceptable condition.  And whhyyyyy would anyone keep a zombie forum online?

https://www.physicsforums.com/#physics.9 
Only has a few vacuum-related posts now and then. Not suitable.

http://www.fusor.net/board/viewforum.php?f=10    Vacuum Technology (& FAQs)
Quite active, and interesting. But sadly, they flatly demand real name registration. And I flatly refuse.

Surely there must be at least one vacuum-systems forum that is both active and has sensible registration rules?

I'm refurbishing an old Edwards Speedivac 2SC20A rotary vacuum pump, and need advice on things like best solvent for final rinse before reassembly, and material for making new oil seals.
This is just for practice, before attempting check & clean rebuilds of larger, better rotary vacuum pumps I have.
Also I have the user manual and have scanned it, but can't find any service manual online. Possibly the model is so old there wasn't ever such a manual.  In fact I have two copies of the user manual (both undated) but the earlier one uses "mm of mercury" for all pressure measurements, while the later one replaces that with Torr (exactly the same unit, just different name.) That would date it, except I don't know when 'Torr' became widely adopted.

Mine is the center one in the pictured group. I'm doing a photo-writeup of the refurbishing, and will post when done.
 
« Last Edit: November 25, 2015, 03:01:10 pm by TerraHertz »
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Offline amyk

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Re: Suggestions for forums for Vacuum Systems?
« Reply #1 on: November 26, 2015, 04:08:40 am »
I thought you were asking for a forum on vacuum cleaners...

But sadly, they flatly demand real name registration. And I flatly refuse.
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Offline calexanian

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Re: Suggestions for forums for Vacuum Systems?
« Reply #2 on: November 26, 2015, 04:42:53 am »
I have never rebuilt any of those particular Edwards pumps but most of them are similar enough to the Welch and Kinney type designs that many things hold true for all of them. First of all the actual vacuum pumping seal is made by the oil itself between the vanes or rotor and the inside of the pump wall itself. If both are still smooth you should be fine. Most leaks occur in the exhaust valve seal in those types of pumps, or the shaft seals. Also gas ballast valves can be problematic. Generally there are no seals to speak of between the internal pump wall and the face plates as thees are precision ground surfaces and the oil itself maintains the seal.

Generally you can fill the pump with oil. Turn it by hand a few times, then plug the inlet and turn it a few more times by hand. If you hear any gurgling back into the pump you have a leaking exhaust valve. This may be of a reed or ball type and sometimes rarely a tappet valve type.

As far as cleaning I just use engine degreaser like if I were cleaning any steel engine component. Berrymans Chem DIp works well for carbon deposits. I also clean with warm soapy water and then just water and then use brake cleaner. Do not touch parts at that point with your fingers or the acid and stuff from your hands can make a dirty or rusty spot down the road. Coat everything in pump oil and re assemble it. Also when its all back together feed a few tablespoons of oil through the pump to help build up the initial film on everything and force it into all the places it needs to go.

That's pretty much my procedure for doing Welch pumps and I cannot imagine that Edwards being much different. I already looked and could not find a kit for that one. Its simply too old. Thats why i always stick with Welch because rebuild kits are readily available.  Good 1400, 1405, and 1402 pumps can be had fairly often and at reasonable prices.
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Offline TerraHertz

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Re: Suggestions for forums for Vacuum Systems?
« Reply #3 on: December 03, 2015, 08:43:18 am »
calexanian, thanks for the hints. The rebuild is going OK, and I managed to find info on the net that I needed. But practical tips like yours are rare, thanks.

The story of that pump is here: http://everist.org/NobLog/20151112_planning_vacuum.htm
(Mixed in with random other stuff. Scroll down. Still in progress.)

This was useful too:
http://vacuumcursus.nl/casussen/Cleaning_Chapter.pdf
CLEANING FOR VACUUM SERVICE

Btw, can you suggest any possible sources for a cheap turbomolecular pump?
I've been looking for one I can afford for years, no luck. Ebay ones are almost invariably too pricey AND missing the controller.  Recently a possible source came up, but it's looking like nothing will come of it. Person involved seems to think turbo-pumps may be prohibited exports from the USA to Australia. And proving they are not, given the complexity and incomprehensibility of US gov online red tape, defeats me.

Pic of my vac chamber below. Bottom port is intended to connect to the big oil diffusion pump below it, via a gate valve and cold trap. But I _really_ don't want to use the diffusion pump.
« Last Edit: December 03, 2015, 09:05:12 am by TerraHertz »
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Offline TerraHertz

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Re: Suggestions for forums for Vacuum Systems?
« Reply #4 on: December 03, 2015, 09:15:38 am »
But sadly, they flatly demand real name registration. And I flatly refuse.
Does it matter? https://fakena.me/ and you're done. ;)

That could work. But there are two more subtle issues. One being honesty. Nothing wrong with using a nic where that's accepted practice (like here, and *most* net venues.) But when a site demands real names be used, and you fake it, that's dishonest. I'm not willing to do that, regardless of their reasons.

Their demand for real names also makes me paranoid, about *why* they want real ID. In the case of Fusor.net I think I have a pretty good idea, and it's not their stated reason. I don't want to touch it with a pole. Not even an 'anonymously' redirected pole. There's no such thing as true anonymity on the net anymore, from eyes that matter.
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Offline Someone

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Re: Suggestions for forums for Vacuum Systems?
« Reply #5 on: December 03, 2015, 10:47:50 am »
Btw, can you suggest any possible sources for a cheap turbomolecular pump?
I've been looking for one I can afford for years, no luck. Ebay ones are almost invariably too pricey AND missing the controller.  Recently a possible source came up, but it's looking like nothing will come of it. Person involved seems to think turbo-pumps may be prohibited exports from the USA to Australia. And proving they are not, given the complexity and incomprehensibility of US gov online red tape, defeats me.
I've not remembered any simple vacuum technology being export restricted, its probably just the overly cautious US sellers. But you may want to stick with reliable sources if you're spending serious money for it as the bearings can be very sensitive to shipping, the original packaging for pumps is very elaborate to keep them safe.

Your best bet would be to ask around the local universities, stuff goes in and out of fashion and there is always spare equipment for a good cause. Also become familiar with the assembled equipment that contains vacuum hardware, it crops up for auction as scrap metal all too often.
 

Offline Denton.Hess

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Re: Suggestions for forums for Vacuum Systems?
« Reply #6 on: December 03, 2015, 11:36:10 am »
My background is mostly on in house use of vacuum pumps: preventive maintenance, performance diagnosis, installation, removal, and helium leak checking on installed equipment: Vacuum dry pumps, boosters, and turbos on sputtering and low pressure chemical vapor deposition systems.

Restrictions on shipping Turbo and Vacuum Dry pumps may have to do with contamination concerns. Toxics contact, that is not be easily decon-able: Arsenic, Antimony from Ion Implantation systems, Phosphine and other dopants in CVD processing equipment prohibit shipping contaminated parts without a lot of extra documentation: Attached Safety Data Sheets, etc...

If your looking for an inexpensive turbo with controller, you may try checking with refurb company such as HiVac (they may have one for sale), or, call equipment refurb houses and offer to troubleshoot controllers in exchange for equipment you want. Try not to get yourself a contaminated pump.

How are you going to leak check your vacuum system? Also, don't for get a backing pump for your Turbo, and consider how you are going to rig up water cooling for the bearings.

Lastly, You may need PFPE oil for your vacuum pump, if you are pumping oxygen. Otherwise petroleum based oils become combustible in oxygen rich environments. "PFPE lubricants are engineered for those applications where heat, chemicals, solvents, corrosion, toxicity, flammability, and service life present lubrication problems. " ~Solvay
« Last Edit: December 03, 2015, 11:43:32 am by Denton.Hess »
 

Offline TerraHertz

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Re: Suggestions for forums for Vacuum Systems?
« Reply #7 on: December 03, 2015, 01:55:25 pm »
I've not remembered any simple vacuum technology being export restricted, its probably just the overly cautious US sellers. But you may want to stick with reliable sources if you're spending serious money for it as the bearings can be very sensitive to shipping, the original packaging for pumps is very elaborate to keep them safe.

Yeah, I can imagine. The packing issue would be something I'd address once there was some possibility of the things actually being available to ship. No sign of that yet. Still have fingers crossed. Hopefully the price won't be in 'serious money' territory - since if it was I couldn't afford it.

Quote
Your best bet would be to ask around the local universities, stuff goes in and out of fashion and there is always spare equipment for a good cause.
Really? In Australia? I guess I've become too cynical after years of seeing Oz companies trash all their cool surplus stuff. You are right, I should try the 3 Sydney universities. Especially since a lot of the vacuum gear I already have came from a university-related source.

Quote
Also become familiar with the assembled equipment that contains vacuum hardware, it crops up for auction as scrap metal all too often.
I've no idea where to begin. Which auction venues in Oz ever have things like that? I've obviously not been looking in the right places.

Restrictions on shipping Turbo and Vacuum Dry pumps may have to do with contamination concerns. Toxics contact, that is not be easily decon-able: Arsenic, Antimony from Ion Implantation systems, Phosphine and other dopants in CVD processing equipment prohibit shipping contaminated parts without a lot of extra documentation: Attached Safety Data Sheets, etc...
I don't have any information on the history of the pump(s) possibly being offered, other than quote "in really good shape". I'm aware of the potential for contamination, but that's not the other party's concern. I don't know if he's even aware of the possibility.

Quote
If your looking for an inexpensive turbo with controller, you may try checking with refurb company such as HiVac (they may have one for sale), or, call equipment refurb houses and offer to troubleshoot controllers in exchange for equipment you want. Try not to get yourself a contaminated pump.

Mm... I'm in Australia. That's why finding a turbo pump is hard.

Quote
How are you going to leak check your vacuum system?
I have a Varian 930-60 He leak detection system, with all the manuals, including training materials and spare sensor heads. It was bought as working, but has been in storage for years. (It's in the foreground of that pic.) Overhauling that will be another vacuum systems learning adventure. Main chamber is still under vacuum. Downside is it requires LN for the cold trap, but I can live with that. It uses a small diffusion pump, no turbo. I will be able to use it for slowly pumping down the big chamber, but there are reasons I'd rather keep it independent in use.

Oh, also have a calibrated He leak, for checking it.

Quote
Also, don't for get a backing pump for your Turbo,
Backing pumps are the one thing I have more than enough of. http://everist.org/NobLog/20141212_racked_serendipity.htm
Still need assorted non-return, isolation, gas admittance, pulse leak, etc, valves, preferably all pneumatic/electric. I want to have the whole system automated, so it can be cycled repeatedly without (my) screwups. As rapidly as possible.


Quote
and consider how you are going to rig up water cooling for the bearings.
I'm really really hoping I find one that doesn't need water cooling. There's no water supply in the room, and I don't want  to bring one in. If unavoidable I can put pipes through the wall and run a heat exchanger outside, with recirculating coolant.

[/quote]Lastly, You may need PFPE oil for your vacuum pump, if you are pumping oxygen. Otherwise petroleum based oils become combustible in oxygen rich environments. "PFPE lubricants are engineered for those applications where heat, chemicals, solvents, corrosion, toxicity, flammability, and service life present lubrication problems. " ~Solvay
[/quote]

I'll only be dealing with gas mixes with similar or less oxygen than air. Some noble gas mixes, some N, and others at low pressures.

Oh btw, one *other* thing I want to look into once the vacuum system is up, is vacuum deposition of mirror surfaces. I have a couple of old but high resolution spectrophotometers to restore, whose main problem is some small non-planar mirrors outside the closed vacuum chamber, have decayed front silvering. Hopefully it will be possible to strip the old silvering off the glass, and re-coat. Need a high-res spectrophotometer for the thing the vac chamber is for, so it would be cool if the vac chamber can be used to get them working. They are Shimadzu QV-50. VERY old, still can't find a manual.

One other question. Among other stuff I was given a 5 gallon drum of Shell Vitrea Oil 41. With a handwritten note on the drum "vacuum pump oil". But looking it up on the net, it seems to be just a standard lubricating oil. With presumably uncontrolled vapor pressure. Anyone know if it is or isn't suitable for rotary vacuum pumps? I do have some small containers of actual rotary pump and diffusion pump oils, but not a lot.

Assuming that drum really is vitrea 41, and not some genuine vac pump oil, in a wrong container. Seems unlikely but given it's origins, who knows.
« Last Edit: December 03, 2015, 02:53:50 pm by TerraHertz »
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Offline calexanian

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Re: Suggestions for forums for Vacuum Systems?
« Reply #8 on: December 03, 2015, 03:37:27 pm »
I will compose some thoughts later on today.
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Offline zapta

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Re: Suggestions for forums for Vacuum Systems?
« Reply #9 on: December 03, 2015, 04:54:58 pm »
Does it matter? https://fakena.me/ and you're done. ;)

Awesome. Thanks.
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Offline calexanian

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Re: Suggestions for forums for Vacuum Systems?
« Reply #10 on: December 03, 2015, 06:07:55 pm »

First thing that needs to be asked is what are your objectives in your chamber? What kind of experiments are you wishing to perform. In many cases a diffusion pump is the best pump to use. Additionally I fear that little mechanical pump may be not be able to keep up with such a large chamber as a backing pump. Under IDEAL circumstances of perfect sealing you should be fine, however you will have a very large virtual leak and gas load and any UHV pump may stall. Your two options would be to have a small diffusion booster pump or step up to a larger mechanical pump such as a welch 1402. Generally that pump is considered the standard for this sort of work. I have found it to be the overall best balance of pumping speed, ultimate pressure, long life, and low noise. Depending on there sort of experiment you are going to perform will dictate what sort of pump you should be using. If you are going to have a large gas load then diffusion pump with silicone oil is the best way to go. If you will be doing surface research then you can only use dry pumps. A good option to turbo pumps at relatively low UHV would be a charcoal cryo sublimation pump. They are clean and easy to use provided you have access to liquid nitrogen. Also ION pumps are a good option. I have found turbo pumps to be more trouble than they are worth. Also I find I cannot think with the noise they produce. I do however find the low RPM whuring sound of a welch pump rather therapeutic. As far as trapping goes, for research a good trap is critical. As far as running liquid nitrogen in one, for me that is debatable. It depends once again on the research. For my use in vacuum tubes we don't even bother. A bend or two in the manifold at room temperature is sufficient to condense back streaming vapor, and our parts are RF heated to the point where any condensate on the parts we are testing are evaporated back off at operating temp. On my home rig I use a water cooled baffle under my valve. The cooling water for the pump runs through the baffle first so its cooler than what is coming off the pump. Optical opacity in the path is a requirement. You may find that you have to use a non silicone oil if you are performing surface studies. Be ware that any admittance of oxygen will begin precipitating carbon deposits in the form of sludge in the pump if you use a hydrocarbon oil. Silicone oils can be exposed to air for a brief period at working temperature and after re stabilizing the system on subsequent operations can return to good performance without the buildup of crud. The nature of the silicone oil however can form a very thin non conductive layer on internal components and experiments if bad back streaming or over heating of the pump occurs.


Lets start narrowing in by figuring out that you have in mind for this system.
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Offline Someone

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Re: Suggestions for forums for Vacuum Systems?
« Reply #11 on: December 03, 2015, 09:31:05 pm »
Also become familiar with the assembled equipment that contains vacuum hardware, it crops up for auction as scrap metal all too often.
I've no idea where to begin. Which auction venues in Oz ever have things like that? I've obviously not been looking in the right places.
The big auction houses locally will be a good place to start but even ebay has the occasional pile 'o junk, there have been several mass spectrometers for scrap value over the past year and I've seen vacuum autoclaves and freeze drying equipment similarly without homes.
 

Offline calexanian

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Re: Suggestions for forums for Vacuum Systems?
« Reply #12 on: December 03, 2015, 10:59:15 pm »
Be careful though. You have no idea what that system was sucking up in a former life. Could be some nasty stuff from a fab house or something. Generally though must systems are in contact with air or introduced benign gasses. I have encountered systems that I know came from old semiconductor fabs and you don't want to touch that stuff until you are sure its clean! Nasty stuff. I have heard horror stories of off the chart toxic materials having condensed in diffusion pump oil and adhering to the walls of vacuum chambers. Again though. Most stuff just spends its life sucking up air.
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Offline TerraHertz

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Re: Suggestions for forums for Vacuum Systems?
« Reply #13 on: December 04, 2015, 01:43:13 am »

First thing that needs to be asked is what are your objectives in your chamber? What kind of experiments are you wishing to perform. In many cases a diffusion pump is the best pump to use.
Several different things, with different degrees of vacuum requirements ranging from gassy glow discharges (think plasma ball and neons displays), through surface sputtering work, down to electron tube range. I'm aiming to work my way down the torr negative exponent scale as I learn techniques. I've never done vacuum system work before.
Most of that will be just interesting sidelines once I have the gear running, but the main project, that it's all for is something I won't discuss in detail. Sorry. It's _similar_ in requirements to fusors, but isn't a fusor. Though, I do want to replicate those things just for fun and photos at one point, since the gear is so similar.

One thing I do need is to be able to cycle from open chamber down to working vacuum, and back, fairly quickly and often. Also I hate cleaning oil off stuff. This is why using that big diffusion pump is a last resort. A water-cooled back-stream condenser baffle came with that, but it's not very good and I'd need to make a better one.

Quote
Additionally I fear that little mechanical pump may be not be able to keep up with such a large chamber as a backing pump. Under IDEAL circumstances of perfect sealing you should be fine, however you will have a very large virtual leak and gas load and any UHV pump may stall.

No no, that little pump is not for that chamber.
It's for general use, and mainly I'm refurbishing it as practice before attempting any of the much larger backing pumps I have. There are pics of them in here:
  http://everist.org/NobLog/20141212_racked_serendipity.htm

In fact the pumping system rack will have two backing pumps - one a large Busch 3-phase unit (that I'm still not sure what form it is inside, possibly scroll?) for pumping the chamber down from atmosphere fast, switching over to a 1/2 HP rotary to maintain. Yes, I know about oil suck-back.

Quote
Your two options would be to have a small diffusion booster pump or step up to a larger mechanical pump such as a welch 1402. Generally that pump is considered the standard for this sort of work. I have found it to be the overall best balance of pumping speed, ultimate pressure, long life, and low noise. Depending on there sort of experiment you are going to perform will dictate what sort of pump you should be using. If you are going to have a large gas load then diffusion pump with silicone oil is the best way to go.

The main project will have a large gas load, but requires rapid fine-controlled gas mix and pressure in the chamber. The plan is to have a turbo (or diffusion, sigh), with a servo-controlled iris aperture in the port between the chamber and the turbo.

Quote
If you will be doing surface research then you can only use dry pumps. A good option to turbo pumps at relatively low UHV would be a charcoal cryo sublimation pump. They are clean and easy to use provided you have access to liquid nitrogen.

No, won't be. The closest I'd come to that will be attempting to do metal deposition mirrors, as sidelines. But everything  I do has to run on a frayed shoestring. So equipment has to be what I already have, or can scrounge for almost nothing. Even regular use of liquid nitrogen will be a cost strain, to avoid if possible.

Quote
Also ION pumps are a good option. I have found turbo pumps to be more trouble than they are worth. Also I find I cannot think with the noise they produce.

Hmm. I've never heard one running. I'd have thought the main peak would be up beyond audible? And with mag-lev bearing types, why is there any noise at all?
Anyway, my hearing is shot since a noisy industrial employment in my early 20s. I can't hear anything above about 8 to 10KHz. So maybe it's not a problem? If it is, nothing a sound absorbing enclosure won't fix. Or ear protectors. The main noise problem round here is and always will be neighbor's stupid barking dogs.

About 'more trouble than they are worth' I had the impression from reading that turbo pumps are reliable and low maintenance? Provided you don't allow sudden air admittance while they are running.
Is 'low maintenance' not true? It's a major attraction for me, since running costs need to be as near to zero as possible. No oil, and cheap to run - this wins, for me. Sublimation/ion pumps - I'd always be worrying about the ion source material running out.

Quote
I do however find the low RPM whuring sound of a welch pump rather therapeutic. As far as trapping goes, for research a good trap is critical. As far as running liquid nitrogen in one, for me that is debatable. It depends once again on the research. For my use in vacuum tubes we don't even bother. A bend or two in the manifold at room temperature is sufficient to condense back streaming vapor,

Yeah, the plan is to have all the oil-containing roughing pumps in one rack, then the chamber and high vacuum pumping in another stand, preferably with no oil at all in that one. Then I can try different oil vapor traps between the two. As you say, probably just a hose with some bends would be good enough.

Quote
and our parts are RF heated to the point where any condensate on the parts we are testing are evaporated back off at operating temp. On my home rig I use a water cooled baffle under my valve. The cooling water for the pump runs through the baffle first so its cooler than what is coming off the pump. Optical opacity in the path is a requirement. You may find that you have to use a non silicone oil if you are performing surface studies. Be ware that any admittance of oxygen will begin precipitating carbon deposits in the form of sludge in the pump if you use a hydrocarbon oil. Silicone oils can be exposed to air for a brief period at working temperature and after re stabilizing the system on subsequent operations can return to good performance without the buildup of crud. The nature of the silicone oil however can form a very thin non conductive layer on internal components and experiments if bad back streaming or over heating of the pump occurs.

Well, I still have a lot of other things to do before I have to commit to bolting on that oil diffusion pump. Still keeping my fingers crossed that a suitable turbo pump can be found before then.

Also that I won't need water cooling. I'm putting in a high airflow extraction duct to my soldering bench, which is right next to the vacuum system. So hopefully I can use that to also provide air cooling for vacuum system components where needed.

Quote
Lets start narrowing in by figuring out that you have in mind for this system.

Ha ha, ask a volt or time nut what accuracy they want. My main objective doesn't need very high vacuum or pristine conditions at all. But whatever the system can do, allows for more fun things to try. Exploration!
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Offline TerraHertz

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Re: Suggestions for forums for Vacuum Systems?
« Reply #14 on: December 04, 2015, 08:31:26 am »
Let me guess, trying to recreate Shawyer's experiment?  :palm:

Ha. I had to google that. Had heard of it, but not by that name. No, nothing remotely like that. I do enjoy a good weird science read though. Mostly for entertainment and the mental exercise of identifying flaws.

The electromagnetic thruster - I have no opinion as yet. It's interesting, and the virtual particle separation theory seems to make 'layman sense'. But I'll wait to see someone actually pushing something along with one, before I get excited.
I gather you are already decided it's impossible rubbish?

But anyway, I wouldn't be going to all this trouble instead of spending few remaining active years on more enjoyable pastimes, if it was something I knew had already been done somewhere.

As for why I won't discuss my project, how about:
 - Don't want to jinx it.
 - Potential commercial value.
 - Like to keep a surprise.
and a few others.
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