Fusion on wheels

. donderdag 28 april 2011
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Have been working on the steel hemispheres last weekend, and welded a rack for the fusor. With wheels! Good blue wheels from a KLM flight case. (flee market, 5 Euro).

Here are the pictures, the last picture shows two big pieces of aluminium (20mm thick!) on which the turbo pump and the hemispheres are going to be mounted:

Connecting to ISO 100

. zondag 17 april 2011
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Tried to make the connection between the upper part of my chamber and the ISO 100 bellows, this is the result:

Since I don't have a lathe, I used the pillar drill and the right angle grinder to make the circular grooves:

This is the viton ring on the pump side:

The disk with the bellows: 

The grove on the chamber side, a viton ring is going to be placed directly in the groove, the M10 en M8 holes have thread for connecting to the chamber and connecting the bellows:

Now with the 80mm opening, it still needs a lot of polishing: 

Top cap

. maandag 11 april 2011
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Working on the top cap this weekend, the surface of the aluminum was quite rough, but armed with new sandpaper wheels for my right angle grinder and some heavy polishing it now has a mirror-like surface.
I have put some petroleum jelly on it right after polishing, to prevent oxidation for now.
Next time I will clean of the jelly and give it a potassium hydroxide bath, when the surface will be exposed to air after washing off the potassium hydroxide, it will form a thin dense layer of Al2O3, without the hydroxide it would form a thicker, more open layer of aluminum oxide.
Also made some clamps for the top cap:

Also got the viton o-rings last Friday, from Polymax, prompt delivery and good prices.
The o-rings are shore 75, I would have preferred shore 90 (the force will be high on the big rings) from Eriks, but their web-shop did not show any prices, and they asked extra money for orders lower than 350 euro's!
I would like to construct a double ring system where the space between the rings is connected to pre vacuum, a construction like that can prevent leakage caused by the permeability of the rings. But that's the next step.
There is a lot of machining to do....

More disks

. donderdag 7 april 2011
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Found some 160mm diameter aluminum disks on marktplaats.nl, 15 and 18mm thick, they will close the holes on the sides of the hemispheres:

Cutting edge solid state hard disk technology

. zondag 3 april 2011
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Found an aluminum disk on marktplaats.nl, 20mm thick with a diameter of 235 mm, the right size for the top of my vacuum chamber.
Machining is easier with aluminum:

The surface was not really smooth, but it's a very solid and hard disk.
It took some maching to get the surface clean, I'm not there yet, but this is what it looks like now:

It will be on top of the fusor, with a viton ring between the aluminum cap and the stainless steel hemisphere.
Which brings us to our "cutting edge" technology.
The upper and the lower hemisphere have to be connected to the aluminum cap and the turbomolecular pump. But the edges were damaged, so I tried soft soldering, which was not a good idea (bakeout impossible). I tried heathing the hemisphere is a coal fire and then hard soldering with a torch. That didn't work, the temperature was too low.
Finally I just tried cutting the edge with the right angle grinder. First with a grinding wheel and after that with 2 different radial flap discs.
And it worked, this is the result:

The first time I also tried the whetstone, but that is not needed, grinding wheel, rough radial flap disc, smooth radial flap disc and then some polishing does it.
This is a first impression of the construction, imagine the turbo pump under the chamber: