Single Flywheel Help

i am planning on making a 4 torque motor single flywheel, so what would be the ideal external gear ratio for it? I have access to all gears Vex makes and high Speed internal gears. I am trying to have the flywheel shoot from everywhere on the field and a good recovery time which i have heard great recovery times for this design.

Many people are doing 35:1 (7:1,5:1)

25:1 with 4 high torque motors will work like a charm.

TitaniumNyanKat… what flywheels are you using with this configuration?

Single wheel shooter.

4" traction wheels or 5"?


I’m using a 15:1 with turbo gears (36:1 overall) with 5in wheels, and it seems to be working.

Going in tangent of the topic, what gear ratio works for shooting in front of the bar?

I have seen 7-1 and up works fine but I would probably go to a 7-1 with speed and change the values in the code

You just need to change the power input for the motors, there is no need to change the gear ratio.

I want attempt to make a field robot that can have a slip gear long range shooter or a lift system. :&

I want to see about making a 2 motor single flywheel.

So I presume your single flywheel is for up against the pole?

Then you can even consider going higher to about 1:35.
And 2 motor should be fine for close range.


I think that a 1:35 is the best gear ratio however, with a 2 motor fly wheel you will be getting close range - which is totally fine.

Huh. I honestly thought it would be much lower. :l

If you’re going for close range only, you don’t need outrageous speeds. I have seen 7:1 double flywheels, so a 15:1 single flywheel should work fine. The lower the gear ratio, the more torque you put into the flywheels, so you will get better acceleration and a higher fire rate at the expense of top speed and range. This same tradeoff appears in car design, and is why cars have transmissions. Correct me if I’m wrong, but torque is basically rotational force, and F=ma still applies, except the mass (inertia) is replaced by the moment of inertia, which is I=md^2 (assuming even distribution of weight from the center, which is generally false, but makes life so much easier). Basically, the moment of inertia is the product of the mass of the wheel and the square of its diameter. Therefore, rotational acceleration (change in speed, not centripetal acceleration, a change in direction around a point) is τ=md^2a. The more torque you have, the higher your acceleration will be, and the faster you can shoot.
Also, 35:1 is higher than my team uses externally (we use turbo motors at 35:3) but even with torque motors, I don’t think two motors will turn a 5" wheel for very long. 35:3 with turbo motors is enough for full court, and we are considering going to speed motors to get more aggressive spin ups and a faster rate of fire.

Honestly, we have run 1:25 gearing ratios for bar shots with a single flywheel and that has barely been enough. We were able to shoot from about 20 inches away from the bar in order to eliminate possible defense as well. However, we have had issues with heating. I am not sure if these are due to friction because the majority of this prototype had built by our B team and I wasn’t a huge part of it. Our launchers are double flywheels because they have definitely worked well for us, but we are always open to new ideas and are constantly trying them. I would like to understand why our 1:25 was stalling, was it a friction issue?

If it was stalling without shooting balls, then yes, it most likely was friction, so you can have people disassemble it and check every bearing flat, since those have been a big problem for my team (some are too tight, and the axle doesn’t spin freely), and if it still is a problem, add a little bit of lube. My team doesn’t use lube, since it’s too much of a hassle for almost no return with our flywheel, but I’ve heard of other teams needing it, and we might try it eventually to try to increase our rate of fire even more. If it works fine without balls, but stalls when you try to shoot, then the balls are being compressed way too much, and you should fix that. We use a polycarb hood so it bends, rather than squeezing the ball.
If friction was in fact the problem, then your 25:1 gear ratio actually might be spinning really slowly. Do you have an encoder somewhere on your flywheel? I would recommend calculating the velocity to see if the motors are under heavy load (the motor rpm is really low). My team uses a 35:3, or ~11.67:1 gear ratio, and we can shoot full court at about 60 power (we use a TBH/PD controller for it), so something is placing heavy load on your motors and slowing them down a lot.
Also, do you use 4" or 5" wheels? We use a 5" wheel on ours. If you use a 4" wheel, that translates to a lower angular velocity (also a lower moment of inertia, but that only makes a difference with the initial spin up time), so that could be part of the issue.

I’m making the same design and 2 turbo motors 7:1 works really good. (4" wheels)

I agree with the above posts. In our experience for shooting full court with a single flywheel you need somewhere between 25:1 and 35:1 total gear ratio.

If you can use high speed or turbo motors do that over force motors. All motors deliver the same output power, but the higher they are geared the smaller torque (forces) are going through the geartrain.

The tricky part of using the same flywheel to shoot both full court and from the bar is that you have to fire at the higher angle and therefore need to be very precise with the speed control. If all you care is full court shots then either flywheel or a puncher could send the ball directly into the goal with higher than necessary velocity. This way you don’t care that much about varying balls, but are limiting yourself to shooting from a specific location.

As for the friction: if you don’t count cases where axles are touching metal frame, then bent or misaligned axle is the biggest source of friction. Also, you have to be very careful if you put two motors on the same axle. Definitely use shaft coupler if they are more than 2" apart. If motor is not aligned or axle enters it at an angle you could easily have half of the motor power going into bending metal that it is attached to.