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Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Wed Apr 08, 2020 11:52 pm
by Richard Hull
Same here, the readings are dropping here as well. I never got even close to 100kn/s. Flash arcing will advance any neutron counting by >2k counts instantly, ruining the count run. Several arcs have been EMI powerful to the point that they have shut down the turbo supply (safety feature). (controller not hurt). I have popped the fusor supply breaker twice is severe arc conditions.

It is now fully decided to totally abandon the cross fusor as a rather worthless project for a guy like myself used to 1 mega neut/s with no sweat and no hassles. As I already noted the cross might do great for newbies looking for a quick win. I am going back to a modified fusor IV which will now take on the fusor V moniker in replacement. No light at the end of the cross tunnel save for that due to arcing which limits the top end. Give me the HV clearances and even electric field distribution, large surface areas for D2 absorption and desorption found in a sphere.

Keep up the reporting Jim. I can feel your pain. Sadly, this was the fastest pumping and best sealed system I have ever worked with. From dead start of the mechanical pump to sub micron in under 60 seconds!!

Richard Hull

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 09, 2020 11:39 am
by Frank Sanns
What is the goal here; high neutron numbers or understanding how these contraptions work? It is an important question.

In my iterations of multiple grid electrodes, needle points, plasma electrodes, reverse polarity, non symmetrical, and the like, there is a different set of operating conditions that gives the highest neutron output. Some are paltry outputs and some are much more robust.

The standard fusor, made in a reasonably large chamber, is a near foolproof way to get good neutron production. With it comes limitations. One is that there is a unique highest current that can be put out at a given voltage with a particular configuration. That in itself says that things are not a simple as they might appear.

In the smaller fusors, alignment of these non traditional setups are going to be super critical. A miss in a big fusor is nearly negligible. In these smaller fusors, alignment will need to be closer to laser cavity mirror alignments than the big ole wire grid fusor.

As for flash arcing, try rounding off some of the edges and cut them back a little to give more relief.

Don't give up. Be more observant and more meticulous in your methods and you might be rewarded some very good neutron numbers.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 09, 2020 1:08 pm
by Frank Sanns
Jim,

Somehow my post response to you was lost. I think you may have deleted your post while I was responding. Here is another try.

No insult intended to you or Richard. My post was more directed at the new work that Richard is doing. I just did not want him to give up.

When I was out visiting Jon Rosenstiel a couple of months ago, we looked inside his cube. It was very clear that some micro mechanism was going on there that is not normally seen in a conventional fusor. I simply was trying to convey some of that info to add to the data base. I know you are Richard are extremely throughough. No insults or demeaning intended. None. Zero. Sometimes I just write and forget the "tone" on a technical forum. My bad. Keep up the good work!

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 09, 2020 1:39 pm
by Jim Kovalchick
No worries Frank. I reconsidered my response because I am aware that written posts shouldn't be looked at that way. I appreciate your contributions to my efforts.
Best regards,
Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 09, 2020 2:15 pm
by Mark Rowley
Fwiw, I went through a multitude of grid sizes before I found the sweet spot with one of 0.45” diameter. I started with one around 0.85” and experienced many of the problems you and Richard have pointed out. Once the 0.45” was installed everything began running smoothly. Other than that, I do use an alumina insulator for the stalk and my grid is tungsten. And of course it’s a classic grid and not a tube design.

Input power seems to be a bit different as well. 10mA input seems excessive, at least from what Ive learned with mine. 3.5mA at 45kV with ~35mTorr of D2 should easily put one at near or over the 500k n/s range. With my system, 10mA at 30kV would only serve to overheat the grid to astronomical levels. If you haven’t yet, try raising the flow and pressure of D2. Strive for higher voltages (40-50kV) with current draw below 5mA.

Mark Rowley

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 09, 2020 3:19 pm
by Jim Kovalchick
Mark,
In my fusor I dont bother looking at chamber pressure except to just double check every so often. I set my current using either my voltage or by adjusting my chamber goes ins and goes outs.

Yes, 10 mA is too much for mine if I run for much time at all. 5 mA is also depending on run length. I really want to try a section of tungsten tube for my next grid. Stainless cant hold the temp. I may shorten my grid a little to give a little more clearance. I had tried tungsten before, but I want to try again.

Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 09, 2020 3:51 pm
by Dennis P Brown
I've posted in two other threads on this topic today, which makes me think that the implications of my previous work wasn't fully understood.

What I am posting and trying to make clear now is that the dominate effect of a "small" chamber isn't its size (volume) so much as its higher operating deuterium pressure. As I showed in my posted experiment, a large chamber can easily be made into a "smaller" chamber simply by installing a wire cage to act as the primary grounding plane around the HV cathode.

This allowed me to operate my "apparently small" chambered fusor at far higher pressures in my existing large chamber machine as if it was really a small chamber. My 50% reduction in 'apparent' volume allowed my existing fusor (previously capable of around 250 K neutrons/sec) to increase its yield by also 50% (roughly.) This certainly was an advantage using my same power supply (identical voltages & current.) However, this increase neutron count wasn't due to a smaller physical chamber alone. Rather, just the obvious effects of operating at a higher fuel pressure.

Now, it is true that there are specific advantages to creating smaller chamber fusors - they can be lower in cost to obtain (a few vacuum components) and offers ease of little to no manufacture issues (off-the-self components); better still, for a given power supply, it can offer more neutrons (very useful, especially for a marginal supply.)

On the other hand, smaller chambers appear to offer more difficult design issues relative to the cathode (as posted by others here)and require very careful control of voltage (this I discovered after making my own, actually smaller chamber to test this experimental idea further.) I did not like operating that small fusor. It posed a lot of control issues and after many attempts dealing with those issues, I retired it as not worth my time (I had a working large chamber, anyway.)

Aside: sorry for posting so much but I do want new users to understand that small chambers aren't necessarily the best route to fusion. As Richard said, these machines do offer another method to reach the goal of creating neutrons. They aren't really superior to normal large chamber machines. Its what one is looking for - join the neutron club (and likely leave) or have a machine available that allows experimental versatility (like my large chamber that easily converted into a small one.)

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 09, 2020 5:34 pm
by Mark Rowley
Dennis,
I completely agree with your theory on D2 pressure. 100% concurrent with my findings as well as what others have said in other forums and groups.

However, your last two paragraphs are problematic, at least from my experience. Firstly, cube and cross Fusors have easily broken the mega mark and are deeply into the realm of being “research grade”. To say they aren’t is nothing short of inaccurate and misleading. Secondly, the difficulty of addressing the cathode issues are no more difficult than finding, assembling, and paying for what a large chamber device demands. The power supply alone for a large chamber device is a monumental effort just on its own. Yes, no one said this is easy but casting undue criticisms and stones at the smaller systems only serves to offer counterproductive doubt in the minds of new folks getting into the hobby (as seen in one very recent post).

It’s too bad the same enterprising and optimistic mindset the group had 20 years ago isn’t prevalent with the smaller systems. Highly likely if a cross or cube Fusor was introduced in 2000 the present day negativity would not be seen.

Mark Rowley

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 09, 2020 6:39 pm
by Jim Kovalchick
Dennis,
I'm not sure why you posted on the thread about my fusor that your earlier posts were being misunderstood. I fully understand that to take the same voltage position on the Paschen curve for a smaller effective plate difference means that gas pressure will need to be higher. The early successful small fusor builders well before me knew about it, and the extra pressure has been discussed by me and others in past posts.

Reading my posts, you will see that my issues are have been related to material and operation considerations.

I went after a smaller fusor because I was intrigued by the success of others. The smaller fusors have been putting out decent tier numbers and you can get cliserto a higher flux for the same neutron production rate because the fusion chamber is compact. Hence Jon R's crazy good silver foil activation to 5000 com. These devices work. There are design challenges as you pointed out, but people have found ways to make it work.

With regard to putting an inner grid into a larger chamber, of course it has the same Paschen effect, but I think it's only needed if the chamber is so big that to get to s desired spot on the curve you have to drive pressure to a point that small amounts of chamber outgassing will be significant in comparison to the amount of deuterium. Also taking closer tolerances with a secondary or inner ground grid can produce the same challenges to arcing as clearances in a small fusor does. Choosing an inner ground grid in a bigger fusor may work, but it necessarily will expose a lower workable flux for the same tier. Richard brought up that he is concerned about a small cross fusor not presenting a uniform surface for ion interactions. He may have a point, but again I counter that others have made it work.

To close my rant: my problems are not about understanding how fusors work. My problems are engineering related.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 09, 2020 6:42 pm
by Jim Kovalchick
Mark,
Your post went up as I was drafting my last. I agree with your premise. Thanks for posting it.

Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Apr 10, 2020 12:13 am
by Frank Sanns
Part of the issue that I have with this thread has nothing to do with your work Jim. It is the fact that Richard and I have not moderated it so that the technical discussions occur elsewhere on the forum rather than in your showcase thread. This is YOUR images thread and as such the rest of us should take the technical into another thread. Only complements or minor commentary should be going on in this section by others. Going round and round on the details of fusion in general are not critiques of your work but rather discussions outside of your work but trigger by your work. That did not come out right but you get the idea.

I looked back through it and I do not see a good way to relocated the discussions without destroying your thread, which we will not do. The problem is that discussions on the matter seem to be directed at you are they are not. They are good technical questions, suppositions, and answers for a stand alone post. Appearing in your showcase though feels personal to you as I saw earlier today. I think a new generic technical discussion on such matter is warranted.

The other problem is that historically, the Images section gets thinned and deleted except for the very best. You of course have nothing to worry about there but in the future, Richard and I need to catch this sooner. Again, my bad.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Apr 10, 2020 12:26 am
by Richard Hull
Like I noted, I leave this field and its associated problems as an activity for the advancing student. I am a neutron guy, not a fusion guy. I have to work with fusion to get my neutrons.

The cross has 6 arms welded at sharp right angles at less than one inch from the grid. You can't radius these weldments to a level suitable in a common 1.5 inch cross without risking cutting into the weld so deep as to damage the cross. I see no sparkling at the weldments which had no little beads, etc. (smooth).

In my perpetually vigilant video image sprayed over a 9"X 9" Monitor screen there is no warning, no creeping currents, just instant unpredictable white arcs. These tight little cross systems are RF and EMI nighthmares! Subtle tritchel pulses aplenty to add to the RF mayhem. I would be highly suspect of any electronic neutron counting around them. This is from several hundred of times I spent hitting the reset button on the counter.

My actual grid diameter in the direction of the discharge streams is .40 inch and was originally a .501 sphere. Enjoy the hunt gentlemen. I need neutrons and neutrons alone. Cylinders and spheres, cylinders and spheres.

Like Frank, this is nothing to do with Jim's effort. I learned much of what I know of value prior to my beginning this cross work in this thread solely from Jim and a few others. Jon R. is always a special case for successes. This is why I leave all this work to the other gentlemen here who will persist in this effort. I had fun and burned off over 40 hours mostly from 11PM at night until stumbling into bed about 8 AM in the morning. Awaking at 4 PM in time for my 1 mile walk, supper, some time with the wife and back at it again. All the time, looking for a sweet spot that never came due to arcs. I went through 8 conflat copper gaskets removing and replacing the grid system and HV insulator that took 44kv on fusor IV I have a robust system. All of my efforts came to naught. (polishing, rounding, careful alignment, etc.) The big x-ray power supply and turbo controller really took some nasty belts on the chin and got up off the canvas to start over again. As the owner of this less than a champ, I now throw in the towel. This system will sit as a trophy until I decide to move on the newer fusor V as this was a non-fusing system in my view, but a winner for any DIY newbie.

Richard Hull

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Apr 10, 2020 5:38 am
by Dennis P Brown
Hello and glad you posted your results on your fusor. Your work has been excellent.
I apologize if you think I am "casting stones". I did not intend this. I too built such a small volume device (though, didn't have the success you achieved.)
Again, your experimental work is very good and do stay at it and continue to post - small volume fusors are and remain an interesting project for people building fusors (as I pointed out, they offer superior performance for smaller power supplies.)

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Apr 10, 2020 9:41 am
by Jim Kovalchick
To investigate my diminishing neutron numbers I opened my chamber last night. I found no discernable issues with the inner surfaces. I do not have an endoscope camera, and not wanting to open my beam end conflats, I did not exam those surfaces. The stainless steel grid looked better than I thought. No signs of melting. The outside of the grid tube was tarnished with a shiny pale blue. I wish I could get a good picture of this, but the inner surface of the grid tube was a dull light gray. I can't make any specific conclusions from these observations.

I elected to put the fusor back together with a new grid. I dont have a tungsten tube to try yet, so I decided to return to using titanium. My first grid was a poorly formed demo tube of Ti. This time I formed and polished a short tube of Ti sheet. I recycled my titanium clip from the latest grid. I decided to make the grid a little shorter than my last one to give more margin to arc shorting. The tube is also wider to more closely match the bigger diameter of other small fusors on this forum. I forgot to take exact measurements of the grid before sealing the chamber, but the opening is about .75 inches. I put a slight bend in my stem to compensate for sag to center the grid in the chamber. The attached photo is my new grid before placing it in the chamber.
In the coming days, I expect to test the new grid. I will continue to post results here.
Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Apr 10, 2020 12:31 pm
by Jim Kovalchick
I walked the new grid up to - 38 kV and 5 mA with almost no difficulty. Some sparkles now and then, but that subsided quickly. I kept my current at 5 mA or below.

Obviously my grid is heating unevenly, and my guess is that is related to my grid clamp. The beam also looks a little feathery, but I'm not sure if that is significant.

Initial neutron numbers at 38 kV were more than twice what I recorded yesterday for the same conditions. 559 counts in one minute on a beam end of the cross using an Eberline PNC tube that read 400 cpm when held against the shell of Richard's fusor IV. From here, I would like to see if these numbers change with successive runs.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Wed Apr 22, 2020 11:52 am
by Jim Kovalchick
You guys are probably tired of hearing about iterations of my grid, but here is the latest. I have added some bulk to it to try to time extend the heat driven window to H desorption. My stainless grid would get yellow hot quickly with any real current. My titanium grid was thin and heated unevenly. My goal is maximizing neutrons for my top end voltage of 40 kV by driving current. I hope to try this new one in the next couple days.

Tungsten carbide. 12 mm tall, 17 mm inner diameter, 22 mm outer diameter. Definitely my heaviest grid in this fusor and hightest melting point.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Wed Apr 22, 2020 8:56 pm
by Jim Kovalchick
Tungsten carbide grid
I walked up voltage on the new grid to -37 kV with no difficulty. There was a little cleaning sparks but not much to speak of.

I did manage to make the grid glow red, but it took a long time to do it at 6 mA. No really bad colors like yellow. Also heating looks even.

Neutron numbers were about as good as I've seen on this fusor, and I did not go to 40 kV.

The real test will be going to top voltage quickly after the chamber is conditioned and see what the numbers look like then.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Wed Apr 22, 2020 11:25 pm
by Richard Hull
Great work Jim, I have secretly, and without comment, also changed my grid to a custom made machined titanium cylinder and done very limited fusion with it. (just under 100k n/sec) before the *%$@#! thing arced shutting down the Turbo. I remain very frustrated with the entire cross system, and shall still rip this thing apart, ultimately. I just feel that the tolerances are just too close due to the grid/stalk positions relative to the 6 sharp right angle weldments of the arms. If a 4" six way cross was not so expensive, that might be the way to go, but the smooth warranted spherical system is a proven performer.

I will continue what effort I can with this system until it so frustrates me that without a care, at that point, I will gleefully tear it to pieces. The work is so pathetic that I just haven't the heart to report on it. It is a beautiful system in looks and operation if you like sudden arc breakdowns about the time you think you are getting there through careful operation and a couple of hours of tedious nursing. Yes, it is an easy win for newbies who just want a win and then leave, but for a seasoned veteran attempting to equal and better his previous work it is a study in frustration.

Richard Hull

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 23, 2020 6:56 am
by Jim Kovalchick
Richard,
I too am frustrated, but I remain inspired by Jon Rosenstiel. I am starting to believe though that the man is some kind of wizard.
Regarding the sparks, I have found that the dimensions of the grid are very important that way, but more importantly, I can't rely on glow cleaning to get rid of my sins. I suspect your construction techniques are better than mine, and you have less sparking. I find that as voltage goes up, the glow cleaning sparks are what initiate the nasty arcs. Yesterday, I had to slow down at 37 kV because my grid clamp started sparking too much for my liking, and I suspected I was close to striking a continuous arc. I am going to try baking longer at lower voltages, and I'm confident I will be able to get to stable 40 kV ops.
My new grid was intended to get somewhat close to Jon's dimensions at least in diameter. I also wanted some mass to give it some heat capacity, a high melting point, and a ultra smooth finish. I'm not sure of the overall impact of it, but to me, I think a higher desorption temperature would be advantageous. Picking tungsten carbide gets me closer to my goal. I certainly can't sinter my own WC grid, but why bother, when they sell wedding rings in various sizes for a little over 15 bucks polished? This grid is a size 7 lol.
My neutrons seem to plateau as things heat up. My next goal is to figure out if the culprit is grid heating or chamber heating. I am working on some ideas for figuring it out that involve operations and construction.
More to come.
Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 23, 2020 7:01 am
by Dennis P Brown
First, very good work on your fusor, Jim. Sorry to hear, Richard but the issues with 'real' small fusors, apparently, can be difficult but that has made Jim's work both rather original and interesting.

This work by Jim makes me think I should re-explore creating a small fusor via my first and rather successful method - using a large fusor but with a small "anode cage".

But that fusor project will have to wait till I build a new building to house my next generation equipment (I also have a lot of research equipment for making my new armor that is based on my revolutionary composite that is a flexible glass.) That equipment, along with the fusor, has my garage filled so I have no room for my car - lol.

I gave up on working on fusors in my Den due to safety issues since that is just too small/restrictive an area. A few months ago I laid out, dug and built the foundation of the new facility but thanks to the virus, have been forced to put that build on hold - also, I've rebuilt many parts of my existing dwelling - apparently, my endurance isn't what it use to be - ;).

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 23, 2020 7:25 am
by Jim Kovalchick
Dennis,
Wouldn't the small anode cage still create close tolerances that would create the chance of the arc phenomenon Richard and I are experiencing?

Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 23, 2020 8:41 am
by Richard Hull
Jim do not think Jon is a wizard, remember, his is not a cross but a 4" square block into which I am sure he bored the largest hole that could mount his conflats. Even a tiny amount over the 1.5" tubulation arms found in our crosses could help avoid arcing and I wonder if Jon rounded his internal hole joint right angles; something which we cannot do. He is such a damned good machinist and has enough long held fusion savvy to consider this 'radiusing" a real aid in avoiding arcs at high voltages in close quarters. However, if he drilled 1.5 inch holes and left them razor sharp then I might agree, He is a wizard. I might have guessed this before leaping into this current effort. But, like I say, I will piddle with this pig until either I or it squeals "uncle".... and I am close to squealing.

Regarding your issues and mine.... I think it is a matter of cathode heating and electron emissive runaway and thereby, conduction, within close toleranced, non-radiused edges, of the arms of the cross. I can't imagine the chamber heating to above 250 degrees F or even higher playing any sort of role in this mutual nightmare. We are guys who have been there and done that in the mega neutron range. We are also fully aware of conditioning issues and the slow and tedious operator learning curve for any fusor and are more than willing to inch the thing forward in real baby steps. We are not looking for the quick win like a newbie. We have both poured a number of hours into our systems. The frustration is real and palpable.

It is now past my normal bed time, so I will get some shut-eye.

Richard Hull

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Apr 23, 2020 10:35 am
by Dennis P Brown
As for maybe the same arc issues - that might or might not be the case if I continue to shrink my anode: while it would seem likely if I continued along that path, my results didn't appear to require that to achieve the same pressure increase as seen in small fusors. My anode cage was much larger than a 50 mm cross. What I was interested in was operating at the same pressure as most such small, 50 mm devices - which I did. Further, since the cage was still rather large (about 200 mm diameter, 500 mm vertical) my cathode was also rather large. In fact, it was my orginal cathode. As a result, it was well worn already (no sharp points and somewhat erroded.)

For me, the operating pressure was the key parameter I was testing and had suspected was the real advantage offered by small fusors. That I achievied typical 50 mm cross fusor pressures was what I had hoped - so, maybe the constraits on this approch - large fusor volume but somewhat smaller anode walls in a cage form are more relaxed. That I had a 50% increase in neutron count compared to my orginal large fusor flux was a significant improvement well worth the effort- so, except for the anode cage and steady operating pressure all else was the same (cathode size, total volume, power supply/voltage/current.) Getting the system to operate at far higher pressure was my goal. This experiment proved that volume itself wasn't either the issue or constraight on higher pressure systems/better neutron count for the same power but rather, simply available fuel.

All this is not in any way to indicate that making smaller fusors isn't both a worth while expeiment or a more cost effective approch. Again, your posts are very useful and experiments are very good work. Keep up experimenting - it opens up the parameter space for fusors and is, in my opinion, something that makes the science more accessible.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Apr 24, 2020 12:53 pm
by Jim Kovalchick
I did some more conditioning today. 38 kV at 7.8mA. My neutron count rate at one of my beam ends was 1.75 times the count rate the same detector read held to the shell of Richard's Fusor IV. I need to get a good silver foil to see what kind of activation I can get. Anyone know of a cheap place to get a 2 inch diameter .007 foil?

At this upper end I am getting arcs at my external feedthrough connection. I have it wrapped with kapton, but I must be at the top end of that.

I used the opportunity to dig one of my standby neutron detectors out of storage and try it out.

This one is an Ebrrline HP-280 epithermal ball. It doesn't work for the fusor, but if I put my hand over the ball, I was able to get some counts put of it.

The ball is cadmium lined to kill thermal neutrons, so putting some moderator between it and the neutron source only would work if I under-moderate. I took the little Nancy Wood BF3 detector out of the ball and put it in the detector well in the parafin block of my old PNC. At 1700 V bias, it gave 400 cpm when the PNC read 700 cpm. The count rate was a little jump though. I may need to fiddle with the bias and threshold some more. Either way. It's nice to know this old dumpster save works.

Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Apr 24, 2020 1:38 pm
by Frank Sanns
Nice work Jim.

My only comment to you and Richard again is symmetry. This configuration is VERY critical for beam paths. The proof of this is in your own photos with the feathered beam on one side and a better formed one on the other side.

When I was out at Jon Rosenstiel's this past January, I had a chance to see his precision in his alignment and his geometry. I also had the chance to see the actual Philo Farnsworth grids and configurations. There are similar trends. Symmetry is king, ratios of inner grid sizes and placements, and also one other important but not so obvious to a lay person (no suggesting that of you), is the detrimental roll of ion funneling with conical inner grids.

I am NOT trying to insult anybody. Please take it as it is given since I have had eyes on these devices and seen results. Of course I have done many variations too but that just is icing.