Phoenix, a Gravitic Motor Prototype
This section documents the work on a prototype of a two-axis Gravitic Motor named Phoenix. The work was carried out in July/2020, but it is only being publised in 14/08/2022. Because a certain time has passed, I've grown unfamiliar with the work, and I'm still in the process of getting myself reacquainted with it. I'll try to come forward with as much information as I can recall.
Prototype Phoenix was never actually built.
There is an Excel Spreadsheet, that I'll be uploading in the bottom of this page, that contains how far did I go in the design of Phoenix.
On the right side, we see an illustration of Phoenix. There are four H structures facing each other, two of them omitted on the figure. The droppers are also omitted, with the exception of one. I'll focus on what is particular in this prototype.
I used soldable PVC tubes. This is what you need to consider: are you going to use water or pebbles? If you use pebbles, can you remove the pebbles from one H structure without dissasembling the H itself? If so, go for soldable tubes because they will give you a solid assembly, less prone to water leaks.
Two beams or arms cross themselves under the table, in a manner described by the detail of the figure. Their weight need to be factored into calculations too. While I was developing Phoenix, it was unclear if using water was better than solid particles (that are dropped in the columns) so I created a spreadsheet meant to compare both cases.
I even considered using mercury, though that is not meant for you to do at home.
The floaters were made of styrofoam. I'd have used a better material if I had access to it. Note that the lighter the material, the better. The floaters are oiled as we have discussed previously. I've placed garden rocks on the bottom of the columns so that the whole things stand still.
The table is aluminum. I tried using wood or other materials but as it stands out you can make a very thin and light aluminum sheet and that is an asset here.
There is a wooden base (a plate) on the bottom and top of the machine. This is because I'd use glass panes around it. Wooden columns make a frame, like a box. Get your carpenter skills going.
The loads, the samples you put over the table, have two variants, load and micro-load. Micro-load is just a value comparable to a nanosample, a guess.
As I was developing the spreadsheet, it soon became clear that mass is important. We've seen on the equations that mass defines the smallest displacement of the table. So I was always trying to shave some grams from the mass of things, that was always the intent.
A variant of the float was the hollow type. it occurred to me that the floater need not be completely filled object. It can be hollowed inside, or even an object like those 3D prints where you set the fill ratio. This helped shave some more grams. I'd say go for it if you have the means to produce such a hollow floater.
I was considering four cases:
Single drop (of water): where you drop all the water in one single drop, and see if the floater moves.
Multi drop (of water): where you drop multiple microdropplets.
Single grain: where you drop a single pebble, and see if the floater moves,
Multi grain: where you drop, for a time, a continuous flow of fine sand, for example, or any other light particulate material.
I had plans to develop all the approaches, but I realized Multi Grain was superior to the other options. Because you can drop very little mass, that occupies very little volume, you can reach very small displacements! Of course, everything hinges on your ability to drop small particulate quantities.
I ended up leaving the spreadsheet sections of single drop, multidrop and single grain broken and UNFIXED. Sorry. It is sort of a simulation, we try a height of liquid or sand and check if we can beat the friction with the spreadsheet taking into account all the masses. Little by little we trim out the values, until we arrrive at a minimum displacement.
I'll read the results of the spreadsheet, as it is now:
We can get in our Phoenix Gravitic Motor a minimum displacement of 26,5 micrometers with the setup presented at the spreadsheet. The table area is a surface of 5mm x 5mm, and the autonomy is for 789 movements. The size of the table surface interferes with minimum displacement because it increases the mass. The conditions for these results are: no 3D printer, meaning that on top of the surface there is no heater pad; it uses a micro-load of 0,005kg; the floater is rigid, it is not honeycomb (3D printed with fill ration) or hollow.
And that is the Phoenix Prototype. If you have plans to build it, make sure to double check all the calculations (it is very easy to make mistakes working alone), and redo the design spreadsheet in a way that is more comfortable to you. I hope you have a great time, and don't hesitate to contact me if you run into issues. I'd very much like to know if you attempted this, what were the difficulties and so forth. Leave a comment below!
Excel Spreadsheet
In the next section we discuss some of the limitations of the Gravitic Motor idea.
BANNER IMAGE CREDITS: ESA/Hubble & NASA, A. Filippenko, R. Jansen
Want to know more about this image? Follow this external link.