The Triwheel (or trYwheel) theory

  Today, I am here to discuss a new theory. I call it the triwheel. Most ordinary flywheels are cyndrillical, creating a square gap in between where the dart is forced through. The hycon flywheels create a circular, dart shaped gap, and consequently, they do much better. The supposed third stage of flywheel improvement is what I am proposing here.

  To understand the solution, I must first explain the problem. With standard, cyndrillical flywheels, this isn’t this problem, but with tapered flywheels like the hycon variation, the issue becomes (mathematically, at least) apparent. The smaller, curved center of the flywheel moves slower than its perimeter. I want to find out if this has any effect on dart performance.

  Each wheel takes ½ of the crush space, and therefore is curved, roughly, in the shape of a semicircle. The more curvature the flywheel has, the bigger the hypothetical speed difference should be. This is bad. We want as little speed difference as possible within the flywheel. The natural thing to do is decrease the curvature, but if this happens, the flywheels will lose their complete encapsulation (envelopment). However, if you add another flywheel to the cage, each wheel need only take ⅓ of the total crush space, decreasing the amount of tapering of each wheel, and subsequently, the speed difference.

 

  This works as a thought, but it needs numbers to back it up, so I measured the diameter of the low and high points of 3 different flywheel types to see just how much of an issue this is to begin with and how much 3 flywheels would enhance it. As a template, I used a 50mm diameter flywheel with a 9.5mm complete envelopment. Here are the results:

Type	50mm dia. 9.5mm crush 0mm spacing Standard wheel	50mm dia. 9.5mm crush 1mm spacing Standard wheel	50mm dia. 9.5mm crush 0mm spacing Triwheel
difference (inner circumference over outer circumference, 50)	40.5          127.23                ———— 50             157.08	41.5          130.38                ———— 50             157.08	45.25        142.16                ———— 50             157.08
percentage of original	81%	83%	91%
% difference	19%	17%	9%

 

*note*

The mm spacing is the distance between flywheels. In real life, they will be separated by some degree. 2 of these measurements are of the same type of flywheel, one just has a 1mm gap between them. I later dropped this for later experiments.

 

The results are quite staggering. The worst flywheel’s minimum traveled 19% less fast than its maximum. The triwheel, on the other hand, received a 9% percent difference, almost a 10% decrease. In theory, the more flywheels are added to the cage, the closer the percent will be to 0, but there is a downside. This number increases radically, so with each wheel added, the performance boost effects are less and less. Three wheels, however, still offer some decent improvement without going too far overboard.

(Insert graph)

 

For further reference and proof of this theory, I also added the measurements of 4 and 5 wheel setups, just to prove that I was on the right track, and:

 
 
 

 *note*

this graph is a rough guess of the correlation of the number of wheels to the percent difference. it is NOT 100% accurate. The line does not follow each dot exactly, rather it shows the type of correlation and is used as a visual aid.

 

Type	50mm dia. 9.5mm crush 0mm spacing Standard wheel	50mm dia. 9.5mm crush 0mm spacing Triwheel	50mm dia. 9.5mm crush 0mm spacing Quadwheel	50mm dia. 9.5mm crush 0mm spacing Pentawheel
difference (inner circumference over outer circumference, 50)	40.5      127.23             ———— 50         157.08	45.25     142.16             ———— 50          157.08	47.22     148.35               ——— 50          157.08	48.18    151.36              ——— 50         157.08
percentage of original	81%	91%	94%	96%
% difference	19%	9%	6%	4%

 

  This is just a hypothesis now, but I will be testing it soon (once my essential hardware arrives)

G1 Update1: The Mayor

   After some time, I presented my work to a friend in the product design field. He liked where this was going, but he did not like the boxy, chunky demeanor of the current design. To show me what He thought it should look like, he quickly drew up the following idea sketch.

This sketch later became the cornerstone whenever aesthetics where involved. After several design iterations and updates, I had myself a product that looked quite similar to the above sketches (except that this one could actually work). I deemed it "The Mayor"

I soon realized that the blaster's signature front foregrip was, sadly, too small to fit in the ESC's. It could work if the Esc's used were smaller, but the ones I was currently using were big and chunky by comparison, so a different foregrip was needed to fit them. The result is pictured below. It is not quite as good looking as that original design, but it works and still looks decent at the same time.

The weapon looks pretty neat in a digital rendering, but how about real life? Would it function as desired? That is what I next planned to find out.
A little pretext here, (an excuse, if you will) I printed the entirety of the Mayor in ABS plastic, which, warps. Big time. Until the last few prints, I had used ABS slurry and masking tape to hold the plastics down. This lessened the warping, but did not rid me of it entirely. Many of the pieces you see here will be reprinted later, as I now have a nice PEI bed the holds prints like these firmly in place.
   On the plus side, things fit well in the blaster and worked accordingly. The next step was to put it together. The Mayor had several shortcomings when it comes to assembly. There are several locations (like where the screws hold on the trigger and the shroud) where the screws bore into, and get their hold from, plastic. This is not good at all. I spent quite some time thinking on how to combat this, and have only recently come up with the solution, so the weapon in the images below does not have these improvements (yet).

For the flywheel cage, I used and ideation similar to that of torukmakto4 and FDL-1 (as stated in a previous blog) when producing it. There is, however a major difference between those cages and the one I am currently using. They both have their motors screwed directly into the plastic. Unlike the mentioned people, I implemented some nice, metal motor brackets for the motors to be screwed into. Those, in turn, are then screwed into the cage with 4 larger, stronger screws. This creates a wider anchor range and is less likely to shear off due to normal wear and tear.

   The Mayor uses 2205 type brushless motors with 2300 KV rating. The flywheels, as mentioned in the original post are 9.5mm (crush space). This setup on 3s yields roughly 150 FPS, the same as a typical FDL blaster. (you see me making many references to FDL, and that is because it is the brushless standard in the nerfing community). The T19 yields 180 FPS, and that is because it runs on a 4s setup. If the Mayor were to also use a 4s LiPo, output would be roughly the same, as most other aspects (I.E motor type, etc.) are pretty similar across both platforms. The battery tray is plenty big enough for a 4s LiPo, so switching to a beefier battery is as simple as plugging one in.

   Unfortunately, while testing,  I had a mishap with a simonK firmware and it took out 2 of my ESCs and one motor with a fantastic bang. I, luckily have spare Esc's, but will need fresh motors to fully complete the weapon.

Current iteration files are on Thingiverse and source code will be up on GitHub soon.