Comparing the Vesta v2 and the Batant v1

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 Batant Construction Guide v1
 Vesta Construction Guide v2

The Vesta was built first as well as the construction guide. Later, two students at Corte University in Corsica, Baptiste and Nathan, built a smaller version of the Vesta as part of a renewable energy project. A smaller Vesta, though may not be the best design for the watt range as explained here, became evidently an essential project for anyone wishing to know this technology. Not only is the Batant it a less ambitious first project, but being smaller and fully demountable it can be more easily used for demonstrations and so on. Which brings us to the general difference between the Batant and the Vesta.

Welding or Bolts

The Batant’s strength is it’s mobility, and so all the fixed joints (joints that don’t move) in the Batant guide are held together by bolts. The first advantage is that the machine can fit into a smaller space, the second advantage is that it is simpler for someone who has little experience welding, and the third advantage is that the pieces can be easily taken off the machine and modified or replaced. The disadvantage of using bolts is that the joint is weaker and will eventually rust.

The Vesta is thus designed to stay in one place and be used everyday for cooking, boiling water, making charcoal and so on, it is not designed to be moved as much as a oven or fridge. The Vesta is obviously much larger and takes more time to take apart and put back together, so there’s much less enthusiasm to move it around anyway (if you have already built a Batan there would be of course much less occasion). So, it makes much more sense to simply weld all the fixed joints creating a final solid piece, it is also simpler to build if you have the hang of welding.

Key or Tube

In the Batant a Key is used as the central pivot whereas the Vesta uses a two tubes the larger rotating around the smaller.

Though at first glance the tube method seems simpler it can run into difficulties: 1, it’s often difficult to find the right tubes and buying them usually requires taking 6 meters (only 50 cm is needed for the smaller), 2. The tubes have to be cut very straight or they won’t turn well and 3. drilling wholes and welding things onto a round tube is much more difficult than a box tube. Finally, round tube is heavier than box tube and more total length is needed (the 50 cm of smaller tube is not theoretically necessary).

The Key method uses a large bolt and two large in order to rotate. The advantages of the key method is that the same type of of box tubing as used for the rows can be used as the mast. So it eliminates the need for tube altogether and so reduces the types of material needed by two. Also, a large bolt can be fairy cheap, I spent a Euro, so the total cost of the machine is also reduced. And finally, the key creates one more degree deconstruction, which be useful if one wanted to replace the mast. The disadvantage is that welding the key together is not easy for someone will little welding experience.

However, using the key method for the Vesta would require a larger bolt, that may be difficult to find. Also, since the Vesta is much larger a support may be need to attach the axe to the mast, to create a triangular support and reduce tilting. So far, we have not built a Vesta with this method, and so do not have a guide nor recommendations.

Straight Rows or Dropped Rows

The most important difference between the Batant v1 and Vesta v2 is the construction of the rows. In the Vesta v2 the classic straight rows are used. This design is fairly problematic: 1. It is difficult to weld tiny squares to the end of box tubing, and moreover to weld them straight 2. The squares must be “tapped” (threaded so a bolt can attach) and any tapped whole can strip (threading destroyed), especially when the threaded metal is softer than the bolt which will most likely be the case. If the threading is sheared off or becomes two rusty the only solution is to cut the end off and recreate and re-weld another piece. This is fairly annoying to do, since it requires access to a drill press, tapping thing, grinder and welder, and so contradicts the philosophy that the machine should be maintained by the users on place. The advantage of tapping is usually ease of mounting the machine since a threaded whole is already held in place, and doesn’t require another arm to tighten as a bolt and nut usually do. The disadvantage is clearly that the threading can strip. If there is still the option of placing a bolt on the other side then there’s not really a problem, a bolt and a nut does the same job as a bolt and a threaded whole. The problem with the straight row is that the “other side” is inside the box tubing and so closed off, it is impossible to place a bolt behind the threaded whole if the threading fails, and requires as mentioned 4 tools to fix. To make matter worse, as far as much as we’ve tried when this occurs to improvise a solution, we haven’t found anything reasonable, and to make matters even worse without a solution an entire row is out of operation reducing the power of the machine by 20 % in the case of the Vesta. The solution is therefore to redesign the machine to avoid this situation.

The dropped row is shown in the Batant guide. The idea is simply to have the row hang down and swing on a bolt accessible from both sides. This also has the advantage of balancing the center of gravity of of the row, and so requires less tension to hold in place. Also when the handle is bent (1 cm above the swing) a limit to rotation is created. The rows never have to reflect downwards (less than about 30 degrees) to focus onto the target since the sun never shines from below. However, if the rows are free to swing downward then every so often there is not enough tension to keep them in place and the reverse and the mirrors hit the ground or the principle axe in the case of the lower rows. By placing a bend above the swing the handle is blocked from rotating all the way around, thus creating a safety mechanism. And of course, even if you decide to use threaded wholes you can always use a bolt if need be.

Other differences are: 1, the design are that the handles in the Batant v1 bend out and around the exterior mirrors; this reduces the length of each row and the principle axis as well as the top stabilizing bar. In the Vesta this represents 7 pieces, if 20 cm are saved that’s 140 cm less steal used, machine both lighter and cheaper. 2, the handle is not welded onto the row so can be detached for transportation or to be easily replaced, for a better handle. These last aspects can of course be incorporated into the straight row design, if for whatever reason it is chosen. And welding the handle to the bar is a lot faster than drilling a bunch of wholes, so should not be avoided by someone who, in the event the handle needs to be taken off, is grinder happy enough for the job.

Base

The base in the Batant is constructed with angle iron and so reduces the types of materials needed.

Stove Top

The Stove Top physically holds the pot, pan etc. on the focal point. The two basic options are a fixed stove top or a stove top that moves. A fixed stove top is clearly easier to build and less likely to break, the simplest stove top we could imagine is featured in the Batant guide. Also for the Batant there would be little reason to want something that moves. The Vesta however is much larger and a person of smaller stature may find it difficult to reach the focal point. If the machine is intended for general use (not a specific use), then a stove top that can be moved in and our of the focal point is useful. See the Stove Top page for the basic ways to do so. But before you begin, it’s useful to know that the stove top can be easily replaced without taking apart the rest of the machine; so it’s recommended to begin with a fixed stove top to finish the machine as soon as possible, and serve as a backup if a future movable design breaks.