Single or Double Flywheel

My team and I were looking online at some already revealed robots for some inspiration for this season’s robot. We already decide on a flywheel type shooter because of its speed and use in similar games (FTC & FRC). We were looking at some robots and saw a lot of single flywheels, and thought that would be a good idea because apparently they put a spin on the discs. But then we saw some videos from China and saw that most teams there is using a double flywheel.

So, I guess my question is, which design is better, a single or a double flywheel? And which one are you planning on using on your robot and why?

What design is better? I don’t think anyone knows. It’s just what works for you, and how you chose to test and try more designs.

They do put spin on the discs, but what does that mean? Why would spin be better? What have others said about how spin effects scoring the discs?

Personally I think I am going to be using a single flywheel as it seems simpler to me. I also thought about how the motors are being used. While a double flywheel doesn’t need two motors its simpler to do it with 2 so having the option of using one motor appeal to me.


Then why does China use double flywheels? Surely if one design is better they would have found it by now (heck they have even started to compete, and ARL champs are in a couple of weeks too).

I have heard that spin makes the discs more stable in flight, but if that’s so, then I don’t know why China wouldn’t go with a single flywheel. Perhaps there’s something I’m missing here?

Spinning makes the disc stable so it flies without tumbling end over end.

However, by the time you get the velocity high enough for good distance, there’s some fairly serious spin on it… enough that it ricochets sideways when the front hits something solid.

A perfect launcher might be 2 flywheels, one on each side, spinning at different speeds. This would impart spin, but not so much that it deflects when it hits something.


People say single flywherls are better becaue of that spin giving it better long range capabilities but for this competition I beleive most shooting will probably be done within a relativley short range distsnce (such as, the center line) so a double flywheel would work fine for the most part, or you could even a same side double flywheel. I honestly dont really think one is particularly better than other, I would suggest building prototypes of both and deciding for yourself which one works best for you.

If a double flywheel would work fine, then why not use a single flywheel for the added long range capabilities. Still not sure why China has chosen the double flywheel. I wonder if it has any innate qualities that would make it stand out against single flywheel?

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Could you link any videos to these people you’ve seen? Maybe we can all analyze some key differences in performance based on the videos. I’ve only seen one half reveal from China. I hope one is a turret so I can get some vindication that the Chinese approved of the design.


It’s not hard to find them if you know where to look!

Also, let’s try to stay in topic…and no, there’s no turret. I don’t think China would build that complex of a design when driver practice could achieve practically the same functionality.

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This is one of the better ones that I’ve seen from China. They also provide a detailed explanation of the advantages of each flywheel type underneath the video.


Yeah man, I’m usually on the forums/YouTube I don’t tend to go looking into the mp.weixin.qq sites cuz they’re sketchy (at least to my western brain, I don’t really know much about how the CCP mines data). Plus it’s super hard to use the internet because I have the slowest WiFi on planet earth, but I did find it on yt and was able to watch: VEX Robotics Spin Up | Team13186A | Double Flywheel Shooter - YouTube

From our testing of flywheels, two motor one flywheel shooters shoot insanely far, surpassing twice the length of the field at something like 20 degrees, which isn’t even the optimal range. One motor one flywheels can do maybe 3/4 across the field, with less reliability.

According to them, they’re doing double flywheel quite literally because it’s weaker, giving them more disc capacity in the goals (discs aren’t flying off into the sunset). This is definitely a smart idea. However they have to be EXTREMELY close to the goal to be able to shoot, and have almost no stability. This could be just them, I’m not able to watch much more right now (it takes ten minutes to watch a one minute video, - looking for it). If it’s not though, I will say full heartedly this is a horrible idea. Yes, this is ok for driver skills, maybe even better, however with a head to head match, i think range will be key. I do like the idea of extra disc capacity, but you could just have to seperate buttons for shooting: one for a long range shot, one for a short range, and then use two motor single flywheel


I think one possible benefit is that since there is 2 wheels you contact a larger surface area of the disk to spin it which might be able to make things more efficient. I havent yet tested this for myself yet though. As for a benefit of using double flywheels shorter range: long range requires a lot of energy meaning slower rate of fire, and the wobbling of the disk slowing it down might allow it to make a softer contact in the goal reducing the chance of it falling out.

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If they are sketchy then why was last season’s Asia Pacific Worlds livestream on there? Why is it the main (if not only) social media platform for official VEX/RECF communication in China? Why do all of the major event organizing committees have official accounts on there literally sharing information for every Chinese event (official or not) for teams to see. Why can teams use it to pay for events? Why is it practically the backbone of VIQC, VRC & VEXU operations in China?


if this is true in your case, then your testing is flawed. motor count shouldn’t have an effect on how far discs travel after a shot, only how long it takes for the flywheel to accelerate to its maximum speed. try to minimize the drag/friction on the flywheel


Well then we truly did make a bad flywheel then the first time. Luckily we improved the second. We did do testing on how fast it could reload, single motor flywheel was around 2 - 3 seconds, while two motor flywheel was a little less than one second. We may be doing a 180 degree flywheel, so I believe that would decrease our reloading time, but it’s still up in the air whether or not we’ll do it.

Thank you for letting me know about motors not increasing range, thought it was the case since there’d be more torque. I’m not a builder and I’m letting them mostly handle the flywheel so :sweat_smile:

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It does matter to some extent, especially with a 90 degree flywheel, because as the disc goes through the flywheel, the wheel will lose less speed if it’s being powered with more torque. Therefore the disc gets more speed imparted to it. If the shot was an instantaneous tranferrence of momentum, then motor count really would have no effect.


It’s just that practically every time something from China is discussed in the VEX scene, it’s usually not in the best of light. Sure, there are known data issues with WeChat, but just because something, or some team is Chinese, doesn’t mean you shouldn’t automatically question the authenticity/safety of it (not everything is bad you know). There’s other social media sites that are practically just as bad.


Cough cough facebook cough cough


Help me here. If I have a flywheel on the edge of the robot are they 0 / 180 degrees and if the flywheel is on the flat surfaces they are 90 / 270 degrees?


A 180 degree flywheel would increase your reload time because the disc would have more contact with the flywheel meaning the disc takes more speed away from the flywheel.


No no, you misunderstand. It’s not about the placement,it’s about how much it goes around the flywheel. So a 0 degree would be just putting the disc in the flywheel and going straight out.


A 90 degree flywheel would it being touched for 90 degrees of movement, so the disc moves like this:


And what we’re doing, a 180 degree flywheel, gets the disc shot out like this:


For the vertical angle, it’s smart to do 45 degrees, as that can go the farthest. and I see most people being in the 30-60 degree range.