Fly wheel discussion

Plan 1: Blue motor, 15 motor ratio (3000rpm) over heats
Plan 2:Double green motor 1
5*5 motor ratio (5000rpm) over heats
Does anyone have any gear ratio or ideas for the fly wheel, the main problem is the over heating and inaccuracy.


Currently we are testing out a double blue 7-1 so 84 tooth to 12 tooth gear ratio and works pretty well for us


Yep, that works really well, but if it only uses one blue motor it will over heat. We are trying to find a way of making a non-heating flywheel only using 1 motor. I don’t know if using roller chains design could avoid over heat

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Using chain could possibly increase friction

If you can stabilize the wheel so it doesn’t vibrate much it will also help with over heating

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Sounds like you might have a friction problem, posting pictures of it may help.


Our team currently utilizes a 7:1 ratio on a single blue motor for 4200 rpms and have no problem with overheating. Like VexTeamZ said it sounds like you have a friction problem with your flywheel. Make sure your bearing flats are all properly aligned etc.


Blue motor 600 rpm geared 84;12 (4200 rpm) Does not overheat


What wheels are you using on your flywheel? Our team was having some overheating issues when we used the 4” flex wheels on our one motor 4200 rpm flywheel. We switched to standard traction wheels and it no longer overheats.


We prototyped a quick flywheel with a single blue 600 rpm motor geared 7:1. We used a 4" 30A flex wheel on a makeshift mount as it is the only type we have. The wheel diameter expands at least 0.5 inches at speed and it occasionally get out of balance. Definitely a first prototype with issues.

Based on the reported motor rpm, the fly wheel normally reaches between 3200 and 3600 rpm and adequately launches our 3D printed disc. It will overheat if we leave it run at full speed… but this led us to a workable solution (for now)…

We do not need to keep the flywheel at full speed unless we are actively shooting discs. We slow it down between shots (or a burst of shots) and monitor the motor temp. We will probably continue to do this even after we refine the flywheel with a stiffer flex wheel and proper mounts (and maybe a 2nd motor - who knows)


When the motor runs, what is it using its energy on? The motor should be spinning freely and with very little current draw if it is not actively accelerating anything. Can you identify what RPM your motor spins at while it overheats (possibly as % or as RPM). Just use the brain to investigate.

So here is the thing. Once the flywheel is up to speed, the only force it is fighting against is friction/drag.

Friction, from the axial loads of the pulleys sitting on the shafts or from the shafts spinning in the hubs is usually independent of friction, and since P=Fv, the power it sucks is directly proportional to the current velocity. Doubling the velocity doubles the frictional power draw.

Drag will be less in general, but increases with the square of velocity, so as you spin it up from half to full speed, the power lost to drag P=(4F)(2v) so it will require 8 times more power.

So just watch the power (watts) as you go from 25% to 50% to 100% speed. If the power usage grows by a factor of 2-3x as the velocity doubles, it is likely friction. If the power usage jumps by 5-7x then it is likely air resistance. While I believe it to be entirely friction, this quantitative comparison should let you model what the likely culprit is.

There is actually way more to this than just friction and drag, like vibrational modes, but likely if you just reduce friction by using greased shafts and teflon washers, and then perfectly align all of the shafts and gears, you should be fine.

Next, heat. The higher the current, the faster it heats up. You can experiment with several velocities and see at what point the temp starts climbing. I would recommend collecting data where you operate the motor at a speed and find the equilibrium temperature.

But mostly just build better. Watch this video for how to do it.


Wow, Thank you so much. I will really look forward to the awesome information that you provided. Good luck in your first robot👍

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Thank you for the information. I think maybe making a double blue motor circular launcher like the team that made the robot in 24 hours will work better than direct flywheels, because it increases the launching distance. Good luck in spin up👍

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Asked this in another chat, but how exactly would you get up two motors to one flywheel? Do you use a chain or just motors and gear? Sorry if this is a stupid question.

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You can attach the two motors with gears or chain, but chain might be more likely to break. All you have to do is make sure it’s a 1:1 ratio between them or they could fight each other.

I suggest you just do a 12:84:84 double blue motor straight launcher, and place the 2 blue motor on each 84 tooth gear to reduce torque. or you can make a circular launching system like the RI24d team robot and place the 2 blue motor on top and buttom of a 84:12 ratio flywheel

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I tested out 2 blue motor vs 1 blue motor yesterday and 2 works way better. 1 over heats and can’t spin to full velocity

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IS this what you are using? also if so how manyish disk were you able to fire before you ran into complications?

How long until it over heated?

If you use 1 blue 7:1, after 30 seconds, the shooting distance and force lowers


I set this up just now. Does ur set up sound like a frieghttrain too?