Ratchet & pawl alternative, 4" wheels

I’m looking for an alternative to the ratchet & pawl to allow a flywheel launcher to free spin. $15 x 2 kits x 8 teams is too large of a bill for our program right now.

I’ve seen this alternative, which is really slick, but I need to apply something like this on a system with 4" traction wheels. I’d prefer not to have to drill out these wheels so they can free spin.

I suppose maybe we can apply something like this with a high strength gear back a shaft (in the gearing assembly) from the wheel shaft.

Have you come across any other solutions to allow flywheels to coast to a stop?

The sprockets and 90 degree bearing work well together as ratchets.

Honestly I do not think a ratchet is even necessary. I think that it is sometimes necessary to lose energy very quickly, in which case a ratchet is actually detrimental.

Please explain.

I would agree with 254 when they say that the ratchet is not necessary. If you are shooting full field shots and want to transition quickly to close up shots, a ratchet will allow the flywheels to keep spinning quickly and not slow down to the speeds necessary to make an accurate close-up shot.

Cough Cough… Angle control would allow the flywheel to maintain its momentum and still shoot short shots by adjusting the arc as well as increasing the rate of fire because the motors don’t need to be set at a lower power. In this situation a ratchet would be ideal.

one thing that i did for an early ratcheting mechanism was use zipties. if put at an angle they are better than the plexiglass used by the team you mentioned because the zip ties are more flexible.

Ok. So ratchets allow a flywheel to keep spinning whenthe power is turned off. While this is good for conserving energy in the flywheel, it prevents one from losing speed easily. For things like shooting up close, one might have to decrease their speed from a high one, in which case it would take a while to reach the desired speed because the ratchet allows the flywheel to continue storing its energy.

In something like PID, this could also be a problem because the flywheel is not spinning at the same “speed” as the encoder. I say “speed” because the encoder is probably not going to be on the same axle as the flywheel.

Following?

If you have a flywheel that could keep this much speed while you drive from base all the way to the goal - I want to study your design and, likely, copy it. :slight_smile:

It is a valid point with PID. But it could be programmed with extra smarts to estimate how fast flywheel slows down. Any ratchet & pawl adds more complexity and makes entire design less reliable. But motors have so much friction, it just seems to be a waste of power to keep them running all the time.

I have a ratchet and a PID control on my shooter, it really is simple to fix the PID loop so that the ratchet doesn’t cause problem, if error is negative, (IE the wheels are spinning faster than you want them to) the motors stop spinning, you just institute an if statement that will not allow the power sent to the motors to go below zero, on t he other hand, if you want to spin the motors against the ratchet to slow it down, then you just leave the PID loop as it normally would be.

The point of using a ratchet isn’t to store rotational kinetic energy as you have said, but to prevent damage to the motors. If motors are forced to spin after the power to the motor is cut it can cause over heating issues and damage.

So the two solutions are 1. Use a ratchet + gradual power up (ours is 1.5 second to full spin), 2. Gradual power up and down of motors at all times.

The second time damge occurs if the moment of firing when launching the ball pushes against the drive of the motor causing a current spike, we are trialling cutting power at the moment of shooting and letting the stored Angular Momentum launch the ball and then powering the motor back up for the next shot. All to prevent motors overheating, we killed a motor in our first competition without a ratchet gear. Started with a 3 motor launcher finished with 5 to compensate for the death of a motor. Still won the comp…