Flywheel choice + questions

[JT_39599B]

Hello, after a past competition my team has decided to rebuild most of our robot in hopes of improving it from our mistakes and errors. Right now we are trying to decide on how we are going to redo our flywheel. Right now, we have a standard flywheel, that is fed directly from our intake. and shoots out the back of the robot We are wondering if we should keep a design like this, or change it to the roundabout design that has the flywheel spin 180 degrees backwards so it shoots on the same sie the intake is on (I will post pictures of ours and an example of the other variation at the end of this post). What I want to know are the ups and downs of each, and which one is in general better. I also have some questions about how I can make mine more accurate, because during our matches, it would shoot in different directions and at different speeds almost every shot. Thank you, sorry if this is confusing.

Roundabout flywheel design (not ours):

Our flywheel:

On the second picture of our flywheel: the intake feeds the discs directly into the flywheel, then it shoots out the back, versus the first picture which spins the disc around 180 degrees so that the disc shoots out the front of the robot.

[JThomas]

Hey @JT_39599B

I am probably the least qualified person to help you since my robot is terrible

My robot

How ever I still want to help you. So from most videos I’ve seen. All flywheels can be really good. What matters most is

• time between each shot

• accuracy

• rpm lost between each shot

I believe each flywheel design can be optimized to be good in all 3 of these areas. I will say I preform not to do the 180 flywheel since it is big

[JT_39599B]

Hi, thanks for responding. Okay so this gives some basic criteria, what are some flywheel building/using strategies so that the flywheel can pass this criteria, and function well?

[JThomas]

You want your flywheel to be as efficient as possible. This means you want everything to be aligned. If you have ball bearings, use them. Ball bearings are so much better than a high-rpm metal rubbing on plastic.

You can use either of these motor setups

• 1:1 3600 rpm motor

Build Guide

606X Spin Up | 3600 RPM Explanation - YouTube

• 2 motor

Each choice is about as equal in pros and cons. I use a 2 motor flywheel and can get up to 4000rpm, but limit it to 3200-3000. You also need to take into account the angle of your flywheel.

You can also add a ratchet to your flywheel. A ratchet will let the flywheel continue spinning even when it isn’t receiving power from the motors. Adding more weight makes it retain its energy longer

[TimmyOsborne]

I would do a straight flywheel. gives you a faster cycle time, easier to build all around and it has very similar range/ consistency

i would also use a blue cart geared up 5:1 (12:60)

i suggest a 60a flywheel with either a second wheel stacked on it(for weight) or a flywheel weight to decrease the amount of energy lost per shot.

i suggest a 60a flywheel because it does not expand so its more consistent for auto

[VexTeamZ]

Part of your issue with consistency may be because your flywheel is cantilevered, meaning only supported on one side. Try adding a support to the top of your flywheel shaft and see if that helps.

[turbodog]

Do you have hard data to back this up? Like actual watt readings?

Also, the ball bearings have a good amount of grease in them. I’d STRONGLY suggest blasting this out with some electronics cleaner. Your rotational friction will decrease significantly. The bearings don’t get enough use for the grease to matter longevity-wise anyway.

[JeterPeter]

These green gears are your ratcheting mechanism, correct?
Our team has the same type of flywheel drive as yours does, with 2 motors on 84T gears driving a 12T pinion, but I would recommend switching to a more compact ratchet that would eliminate the need for an entire shaft to hold the ratchet.
This is the ratchet our team uses:

About the ratchet

There is a plastic shaft insert in the gear, which has a circle instead of a square hole for the shaft:

That’s just an example, but using a ratchet that fits onto the gears rather than needing its own shaft would reduce the thickness of your flywheel chassis and give you more space to work with, but more importantly, it would reduce the overall friction because your gear train has fewer shafts to add said friction.
On the same topic of friction, you also don’t need bearing flats on your motor side(I can’t tell if you have them or not).

Non-aerosol lubricants are also legal, though our team doesn’t use them.

I’m not our team’s coder, only the designer, but our technical teammate(and other people on the forums) have also said that using watts as a measurement to drive the flywheel motor is more effective and stable for the flywheel(If anyone can expand/elaborate on that, please do).

I’ll also echo VexTeamZ for the sake of support: a cantilevered flywheel is no bueno. Our team tried it, but the flywheel had consistency issues. Though bracing it didn’t fix all our problems, it did help quite a bit.

One last tip:
If you have a 4in flywheel, 4200rpm is way too much. Our team uses a 4in flywheel and we don’t go above 3000rpm, which is we are switching to a 60:12 gear ratio to drive our flywheel from the 84:12 like you have.

There are also numerous topics about flywheel consistency and design, using the search bar and perusing those topics could also help.

[BP1353]

What is the benefit of using a ratchet when you could just set your motors to coast when not receiving power?

[JeterPeter]

I’m not entirely sure(this is the coder on our team’s area of expertise) but I don’t think that works at the end of matches. Our team put ratchets on because at the end of matches, the motors are locked to prevent movement, and doing that on a flywheel would damage the motors.

[TimmyOsborne]

If motors are locking at end of match its a programimg issue as weve never had this happen.

[550G.Robotics]

If I were you, I would focus on making the flywheel spin. This will allow rotational motion that can propel discs to be launched out of your robot.

[JT_39599B]

Hey everyone, thanks for the feedback. My team talked it over and this is what we are going to do to try and improve our flywheel;
-Straight flywheel
-60a flex wheel for flywheel
-Ratchet on 84t gear reducing number of gears + shafts
-Lower gear ratio
-Use watts for measurement
-Supported flywheel on 2 sides
Thanks everyone, and let me know if you have any more suggestions, I will try and post a picture when we finish it, it may take a couple of days though.

[cvslinc]

Just want to add some stuff on to that:

JThomas recommended a 5:1 ratio for the flywheel, and the 84T ratchet will give you a 7:1 ratio. The ratchet design posted by JeterPeter should also work on a 60T gear, giving you the 5:1 ratio you need. The ratchet goes on the same shaft as the motor, making the overall flywheel smaller.

Although watts are a great way to measure the friction in your flywheel, they should be used to test your build quality, not drive the flywheel. In order to run your flywheel, I would tell your programmer to look into making a PID loop that uses voltage instead of velocity.

[turbodog]

Just dropped a video/post with a new passive ratchet design. Worth a look.

[JT_39599B]

Just watched it, nice design! You mind if I use it and give credit in my notebook?

[550J_Robotics]

My team has done some research and built a couple of prototypes and we have found that the best way to keep a consistent speed of the flywheel is to add more motors. Our flywheel now has 4 motors. We keep it at a very high velocity to maximize our range, but it is also possible to slow it down and create a faster-firing, more accurate, short-range flywheel. I hope that this helps

[turbodog]

no problem. please post back in the original thread about your results/pics/etc.