Advanced Flywheel Ideas -- Ratchet and Pawl?

VEX V5 General Discussion General Forum
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So as I was regularly checking forum this morning, I ran across this thread: https://vexforum.com/t/expanding-flywheel/29779/1

And I liked both the mechanism and the idea. Although the mechanism failed in the end of the video, I am still very very thrilled to see teams already starting to look for something more than just motor >> a bunch of gearing >> flywheel.

In short, flywheel is something that has huge angular momentum. When starting up it requires a good bit of current from the motor even with some slew rate control, and when the motors are suddenly shut down – ahhh that’s the worst part – the huge momentum can rip apart chains, gears, and the worst, internal motor gears.

The former is something you can handle with some slew rate control. But the latter, as mentioned before, occurs at the end of autonomous and the match, when the motors are forced to shut down by the field control. The issue thus arises that one has to make a decision between sacrificing a few seconds of launching time in auton and driver control to decelerate my flywheel properly, which is a huge bite out of auton, and powering motors until the end and prepare to accept broken gears, flying chains and the horrifying “click click click” coming from inside the motors.

Is there a way to circumvent this issue?

[FONT=“Arial Black”]Think about bicycle wheel.[/FONT]

I was inspired by the thread I quoted to think more than just motor directly powering flywheel, and I thought of a bicycle’s ratchet and pawl mechanism. A flywheel does some similar tasks to a bicycle – it only needs to be accelerated, while doesn’t necessarily need to be precisely decelerated. When the power source stops, the movement of the wheel shouldn’t suddenly stop.

https://www.youtube.com/watch?v=RuA1bD8vtCE
[Ratchet and Pawl Meachanism - YouTube

VEX has ratchet and pawl mechanism, I thought. The spring part might be tricky, but it can easily be done by a rubber band.

I think this is a pretty significant idea that can possibly greatly enhance the functionality of NBN flywheels. So I decided to post my thoughts here. Feel free to comment and offer your opinion. Right now I am pretty excited, and I will work on a design that is possibly gonna work with VEX parts.

To better flywheels,

Martin](Ratchet and Pawl Meachanism - YouTube)

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And of course, there’s already a matured VEX design out there.

3

What a good idea!

I’m not quite sure how it would work on a flywheel launcher though; can you explain it a bit more? :confused:

4

I already have a working one that uses no elastics or springs whatsoever. It has absolutely no issues with coasting friction and it allows the motors in my flywheel to rest while not launching while still maintaining a very high RPM on the flywheel and a free spinning post match cool down. I find it very effective and hope to see other teams develop their own ways of accomplishing a ratcheting clutch for their flywheels.

5

It didn’t actually fail. It worked significantly better with the extra weight. I was just lazy and didn’t secure it on the axel with collars (not the best idea). I was also using nuts in the replacement internal motor gear bags which aren’t vary strong either, especially at that speed with that weight attached with just a ziptie (again, not my best idea). It works beautifully now with better weights and I hope to use it in competition this season. :slight_smile:

6

Amazing. No springs or elastics for the pawl, no coasting friction, then the only solution is gravity. brilliant. Absolutely.

I am still obsessed with using a pneumatic shifting gear to hook up flywheel motors with the base. So the ratchet is very important in this case.

I feel kinda bad revealing your ultimate awesome design idea… don’t be mad please. :stuck_out_tongue:

7

Well I believe that is a even cooler idea. Future innovate award candidate!!!

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Lets save that for April… :smiley:

9

He didn’t say no coasting friction. he said

as in there is, but it’s not necessarily critical. That should enlarge the alluring beauty of this mystery.

10

Funny that we had similar ideas, VEX Nothing but Net Robot in 3 days documentary - YouTube.

11

Very nice! I love the cam. (no there’s no pun there, the polycarb cam) Never thought to blow it up so large.

What is the firing rate on that guy?

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Ha ha thanks! The firing rate on a full battery is a ball per second.

13

I don’t really understand the ratchet and pawl mechanism in the video. In order for the 5" diameter wheel to spin freely, its hole should be circular, shouldn’t it? But to my knowledge, 5" diameter wheels only come with square holes. Did you guys drill the wheel’s hole to make it circular, or am I missing something? :confused: Sorry if this question seems silly in some way, since this is my first post on the forums.

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It’s most likely just got the plastic inserts to let it spin freely

15

How long does it take to completely spin down after stopping the motors? The only thing Im worried about with a ratchet design is if it takes so long to spin down that when you go around to intake more balls you accidentally launch one because your flywheel is still spinning.

16

You’ll want to build something to prevent the balls from reaching your flywheel when you aren’t ready to fire them. It doesn’t make sense to completely stop your flywheel every 4 balls; that rather defeats the purpose of a flywheel- to store energy.
Whether or not you use a ratchet you’ll want to be able to control firing without stopping your flywheel.

17

Complexist,

Aren’t the inserts only compatible with gears and the new traction wheels and omni wheels? In the video they seem to be using the older 5" wheels.

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You can pop out the inserts in the wheels and replace them with the round plastic or metal ones.

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http://www.vexrobotics.com/catalog/product/gallery/id/26789/image/30802/

Now that I take a closer look at the wheel it looks like you guys are right and the standard insert may be removable. That’s strange, however, because while I was playing around with those wheels while prototyping a flywheel I don’t remember seeing that. But thanks for your help Highwayman and Complexist!

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does anyone have an effect way to remove the inserts? it seems that they are glued in and when i tried to forcibly remove it on one wheel i destroyed the plastic. any ideas would be great. thanks