Is There an Optimal Size for Magrid Casings?

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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Billy Catringer
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Post by Billy Catringer »

Roger wrote:Whats wrong with standoffs like the 4 that held up Wb-6? Tapered cylinders IIRC.

Nothing, except now we will have to use 24 of them, four for each torus. The 2 meter magnets are too large, too heavy and too powerful to be held together the way the WB6 magrid was held together. I was not sure that we could put that many posts in the system. It turns out that we don't have a great deal of choice.

Roger
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Post by Roger »

Plus the standoffs can be kept in the shadow. Yeah 24 standoffs aint my first choice either.

Back to WB-7.1, I wonder what Nebel will do with no nubs... Standoffs? Or just better nubs that electrons dont like..... ?
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

Billy Catringer
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Post by Billy Catringer »

Roger wrote:Plus the standoffs can be kept in the shadow. Yeah 24 standoffs aint my first choice either.

Back to WB-7.1, I wonder what Nebel will do with no nubs... Standoffs? Or just better nubs that electrons dont like..... ?

That's a good question. My guess is that he will try to insulate them some how. Standoff aren't cheap and he would have to modify the vacuum chamber to mount them. The picture of the chamber I saw suggests that it is a coded vessel and if you weld anything at all to it, you have to get an underwriter's stamp on each modification. That isn't exactly cheap either.

D Tibbets
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Post by D Tibbets »

Couple of layman comments.
24 standoffs/ four per magnet? Why not three, good tripod support. The standoffs could be further reinforced with cross bracing if needed, so long as everything was kept in the shadow(?). Or, as I suggested in another thread, keep the joints, but arch them further from the plane of the magnets. Use 2-3 standoffs per magnet for further strength and stiffness (and vibration dampening) if needed.
And, the standoffs would not need to be welded to the vacuum vessel. They could be attached to a cage, something like the
Faraday cage used for WB6, except much stronger (vacuum vessel size permitting).


Dan Tibbets
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Billy Catringer
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Post by Billy Catringer »

D Tibbets wrote:Couple of layman comments.
24 standoffs/ four per magnet? Why not three, good tripod support. The standoffs could be further reinforced with cross bracing if needed, so long as everything was kept in the shadow(?). Or, as I suggested in another thread, keep the joints, but arch them further from the plane of the magnets. Use 2-3 standoffs per magnet for further strength and stiffness (and vibration dampening) if needed.
And, the standoffs would not need to be welded to the vacuum vessel. They could be attached to a cage, something like the
Faraday cage used for WB6, except much stronger (vacuum vessel size permitting).


Dan Tibbets

Actually, it will two very close together with two more set 120 degrees apart from the centerline between the two that are close together. I will have to do that in order to accommodate the plumbing. The reason for the plumbing being a pain is that I will have to put a partition between the inlet and the outlet wth the inlets and outlets be being very close to one another. Why? Because if I don't do it that way, I can't guarantee even flow around the toroidal shells.

MSimon
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Post by MSimon »

Coolant in. Coolant Out.

Current in. Current out.

Since the currents for SCs are not large (100s of Amps) one standoff might work for current. But, if the coolant standoffs HAVE to be close together then you need two more spaced 120 deg from them to manage torques.
Engineering is the art of making what you want from what you can get at a profit.

Scupperer
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Post by Scupperer »

Image

Forgive me, I'm just a caveman, and understand very little of what is discussed here, however much I enjoy reading it, but I love geometries.

I'm curious what effect reshaping the "nubs" as pictured above might have on the fields. Will changing their intersection to the rear of the coils, and increasing their radius clear them of the wiffleball effect and recirculating particles?

I understand the change in shape would require an increase in material for them to continue to act as supports for the 4 magnets, but if the shape change doesn't solve the interference that the current "nub" configuration apparently causes, then solving for size is immaterial. (Unless there's no chance such a configuration could support a "full" size coil to begin with, which is entirely possible with the stresses on a support arc over 90 deg).

Please, no laughing; the idea just occurred to me as I was looking at WB 6/7 photos and wondering why the nubs were intersecting the coils in areas that were clearly within the interior field lines of the device.

Also, even if they aren't capable of independently supporting the 4 coils as shown, they could be what's need to prevented vibration/torque with cantilevered standoffs for those coils, if they no longer interfere with recirculation.
Perrin Ehlinger

Billy Catringer
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Post by Billy Catringer »

I can't speak to the physics, Scupperer, but I can tell you that getting coolant to those nubs is a hairy business unlikely to succeed. Without coolant, they are useless.

Also, the horseshoe shaped ones you drew would not make for good tension members. They would impose torque on the shells they are attached to.

Scupperer
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Post by Scupperer »

Billy Catringer wrote:I can't speak to the physics, Scupperer, but I can tell you that getting coolant to those nubs is a hairy business unlikely to succeed. Without coolant, they are useless.
If the nubs are capable of providing some support, then the coolant could still be provided from a cantilevered standoff - the standoffs just wouldn't have to be as large to support the full weight of the upright coils. P*l makes for pretty hefty size requirements the larger l gets, especially if you have deflection/vibration concerns, along with mechanics you need stuff inside the supports.
Also, the horseshoe shaped ones you drew would not make for good tension members. They would impose torque on the shells they are attached to.
The shape would make a horrible tension member. But if they aren't providing coolant, and only act as support, it's an engineering/materials solution that may be within possibility - it depends on the size of the "shadow" on the rear of the coil that they can attach to in order to spread the loads out, or how much structural offset they provide for cantilevered supports.

As to the practicality, it's just a question of if they still interfere with the working of the device.
Perrin Ehlinger

ekribbs
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Post by ekribbs »

Scupperer wrote:Image
Billy Catringer,

Scupperer's idea here will put the semicircular "nubs" into massive bending due to the 60 Tesla magnetic forces you stated earlier, The "nubs" would break from the bending and the whole assembly would fly apart. 60 Tesla, WB-6 was 1.25 Tesla. Am I correct Tom Ligon?

Remove all the semicircular loops, add the same leg supports to the other four tori, spread out the base legs, and add diagonal struts to prevent rotational collapse, and you have my idea, Billy.

Scupperer
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Post by Scupperer »

ekribbs wrote:Scupperer's idea here will put the semicircular "nubs" into massive bending due to the 60 Tesla magnetic forces you stated earlier, The "nubs" would break from the bending and the whole assembly would fly apart. 60 Tesla, WB-6 was 1.25 Tesla. Am I correct Tom Ligon?

Remove all the semicircular loops, add the same leg supports to the other four tori, spread out the base legs, and add diagonal struts to prevent rotational collapse, and you have my idea, Billy.
Image
(angled legs and diagonal struts omitted for ease of modelling)

How far is the cantilever expected to be? And what is the expected force a 60 Tesla magnet will push back at? If it's high enough to rip the "nubs" apart, how is a cantilevered support going to keep it stable, particularly if it really is as heavy as 55,000kg?

My structural intuition is pretty good when it comes to buildings, this is a bit out of my field, but for that kind of weight you'd probably have to camber a cantilevered structure, trussed or not, against gravity just to account for the deflection. If a force is pushed back on it, it'd be bouncing all over the place.

I suspect, however it's supported, something's going to have to connect the coils to each other to keep them in position relative to each other, unless there's enough freedom where displacements of the coils from each other don't matter.

Image
This, however, would avoid a lot of those engineering problems. It's why I'm curious if changing the geometry of the nubs will reduce/omit their effect on the field. Whether they're capable of being primary supports or not in this shape is almost the aside.

Edit: not that it has any basis in reality or the science of fusion/polywell, but they also look kind of like solar flares.
Image
Perrin Ehlinger

ekribbs
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Post by ekribbs »

Scupperer wrote:
ekribbs wrote:Scupperer's idea here will put the semicircular "nubs" into massive bending due to the 60 Tesla magnetic forces you stated earlier, The "nubs" would break from the bending and the whole assembly would fly apart. 60 Tesla, WB-6 was 1.25 Tesla. Am I correct Tom Ligon?

Remove all the semicircular loops, add the same leg supports to the other four tori, spread out the base legs, and add diagonal struts to prevent rotational collapse, and you have my idea, Billy.
Image
(angled legs and diagonal struts omitted for ease of modelling)

How far is the cantilever expected to be? And what is the expected force a 60 Tesla magnet will push back at? If it's high enough to rip the "nubs" apart, how is a cantilevered support going to keep it stable, particularly if it really is as heavy as 55,000kg?

My structural intuition is pretty good when it comes to buildings, this is a bit out of my field, but for that kind of weight you'd probably have to camber a cantilevered structure, trussed or not, against gravity just to account for the deflection. If a force is pushed back on it, it'd be bouncing all over the place.

I suspect, however it's supported, something's going to have to connect the coils to each other to keep them in position relative to each other, unless there's enough freedom where displacements of the coils from each other don't matter.

Image
This, however, would avoid a lot of those engineering problems. It's why I'm curious if changing the geometry of the nubs will reduce/omit their effect on the field. Whether they're capable of being primary supports or not in this shape is almost the aside.
You must remove the semi-circular loops because:
1) radial outward forces will break them.
2) they provide an electron loss path.

As I listed in my design idea earlier:
1) make the truss stiff, and that also means ADD diagonal struts to the base legs to prevent rotational collapse !
2) spread the base of the legs to add bending stiffness to the truss.
3) optionally add "bumpers" in the 8 corners if the short truss cannot by itself suppress vibration and deflection.

Scupperer
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Post by Scupperer »

ekribbs wrote:You must remove the semi-circular loops because:
1) radial outward forces will break them.
2) they provide an electron loss path.
1) Not if they're not the primary supports and are just acting in a lateral support capacity, as shown in the previous post.
2) This is really the only concern. I'm curious if this is the case, because the idea of changing the shape is to start in the shadow on the rear of the coil and go around the cusp line, instead of directly through it. I'll admit my caveman understanding here, though, yet I shall forever wonder why the supports themselves aren't an electron loss path, too.
Perrin Ehlinger

ekribbs
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Post by ekribbs »

Scupperer wrote:
ekribbs wrote:You must remove the semi-circular loops because:
1) radial outward forces will break them.
2) they provide an electron loss path.
1) Not if they're not the primary supports and are just acting in a lateral support capacity, as shown in the previous post.
2) This is really the only concern. I'm curious if this is the case, because the idea of changing the shape is to start in the shadow on the rear of the coil and go around the cusp line, instead of directly through it. I'll admit my caveman understanding here, though, yet I shall forever wonder why the supports themselves aren't an electron loss path, too.
1) Look at your own picture. Imagine a small tangential force on one of the tori, from whatever source. Now add a large axial magnetic force on the same torus. This is a classical buckling problem. The torus will rotate and the four columns will buckle and collapse. ADD the damned diagonals!
The little semicircular tubes will not resist the rotation. Also, Billy has already said that he cannot provide adequate and even cooling or electrical power through the little things.

2) If you get a picture from online somewhere, your semicircular tubes STILL cross magnetic lines of force and provide an electron loss path. The only components that may be aligned to lie only in a "shadow" would be the base legs! I also stated that all the truss components must be insulated as well.

Scupperer
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Post by Scupperer »

ekribbs wrote:1) Look at your own picture. Imagine a small tangential force on one of the tori, from whatever source. Now add a large axial magnetic force on the same torus. This is a classical buckling problem. The torus will rotate and the four columns will buckle and collapse. ADD the damned diagonals!
The little semicircular tubes will not resist the rotation. Also, Billy has already said that he cannot provide adequate and even cooling or electrical power through the little things.

2) If you get a picture from online somewhere, your semicircular tubes STILL cross magnetic lines of force and provide an electron loss path. The only components that may be aligned to lie only in a "shadow" would be the base legs! I also stated that all the truss components must be insulated as well.
1) I'll accept that you didn't read a thing I wrote after the first picture, and didn't understand that the tubes were thereafter intending to act solely as stabilizers, secondary to the cantilevered supports, and as such would not need wiring nor cooling within them, nor would they spontaneously buckle/explode without the legs first giving way.
2) I'll accept that I have little to no understanding of the magnetic fields, nor even if insulating the nubs in this configuration would make any difference in their effect on the field; just that it would be on the exterior of the line cusp at this location, instead of crossing through the line cusp, as one can see in the diagrams of the fields at these locations.

Therefore, I'll move on to other interests ftm. Enjoy.
Perrin Ehlinger

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