97963A Early Season Reveal

[anon4126930]

There are some things I agree and disagree within this thread.

@7686B_Ian

don’t waste two motors on a lift if it is not a DR4B. If you gear it right it can work just as well as a two motor one. And if you are having trouble with it lifting up, just add some rubber banding.

@Gameoa

You definitely dont need 2 V5 motors on a rd4b

@Riptide

Even a dr4b works fine on 1 V5 motor.

This really does depend. The main reason why my robot worked so well with one motor with 200 RPM and 1:7 gear ratio is because the lift, although looked bulky, was incredibly light (Seen in the reveal, they are using C-Channel Box bracing rather than X-Bracing, because it’s lighter and smaller) and the banding was tuned explicitly to be near linear with only two points. So, if you want your lift to be fast and only use one motor you need the following:

• Light field elements and in low numbers
• Lift that uses KEPS screw joints, in all places possible (Even through the gears)
• Lift has no more than 2 axles for its support, so you can track the position of the lift with a potentiometer
• Rarely use X-Bracing, as it is heavier and there are alternative, lighter methods that provide the same support (Such as C-Channel Box bracing, as seen in the video)
• Drill out the holes out of C-Channels that any axle or screw will go through, if the hole has a bearing flat screwed onto it
• Use regular bearing flats, with the joints and axles located in the middle of the 3 holes, as much as possible between two anchored points.
• You don’t need triangle bracing for your lift to be linear. In fact, triangle bracing, for the most part, makes the lift have more friction which will not be good if you are planning on doing one motor. You should be doing two point bracing in a manner that makes the lift linear.

If you lift up 10 of the cubes, you will be lifting up roughly the weight of TWO mobile goals, or 1 Mobile goal and 10-12 cones if you know the struggles from In The Zone. My cap bot only lifted 0.6 Ibs of weight. So if you’re planning on doing one motor you should be either doing 100 RPM 1:7 with one motor or 200 RPM 1:7 with two motors, and even that will likely be more or less a struggle for most teams. If you wish to copy my method of gearing if you’re attempting one motor, it will not work, as the HS gears are plastic the HS inlet will strip from all of the stress/momentum shifts.

@sarah_97963A

Yes those are abs wheel legs. We need anti tip mech (our drive wheels never enter the goal zone), and we don’t want our robot to be lifted up while crossing the goal zone. Wheel legs can achieve that easily.

Very intuitive thinking! But considering the repetitive shaking motion while moving how does it affect your autonomous? I cannot see the extra sensors on the robot, but I’m assuming you have tracking wheels?

@doge

I’m aware that we are talking about the 100 rpm cartridges. well maybe but in my experience 100 rpm with an external 1:7 gearing struggles to lift even a 2 bar in a goofy style bot

@64540A

You can’t rubber band a two bar (glad to see some one try tho)

It is definitely possible to rubber band a two bar. Look up StarStruck season and you will see plentiful examples on how teams rubber banded a two bar.
And most importantly, anything is possible with the right gearing or right support

@Gameoa

It is really easy to rubber band a 2 bar as seen with 99% of starstruck robots.

^ Agreed. And if you look in “In The Zone” you can even see methods of rubber banding for two bars that are capable of extending past 250 degrees of motion.

@Gameoa

P loop is not a very good solution for a lift, you would need atleast a PI loop and most likely a full PID loop to make a lift run effectively.

Considering the delicacy of handling cubes into towers during the matches, I have to agree with this.

@Gameoa

P loops can easily overheat a motor if their tuning is too high, and if you go any lower than that your movement becomes very slow.

I partially agree. Motors can even overheat even with PID because it doesn’t consider momentum/inertia compared to the force applied. This is where motion profiling comes in, but to be frank your robot should be built in a manner where the motor would never overheat even without motion profiling.

@Gameoa

P loops work fine for small lightweight mechanisms, but quickly fall apart when tested on something load bearing.

To be honest, even if the mechanism is lightweight you should always use PID. If the mechanism is light then it would be very easy to overshoot the position, hence is why PID exists to compensate and re-adjust from the overshooting.

@64540A

First off, I say two motors specifically for this year because of the heavy load that will most likely be carried.

I agree, and I would definitely suggest teams to do a 2 motor lift if they are incapable of following build quality techniques.

@64540A

I use a full pid loop but I heard somewhere that you could just use a p loop.

I used a P loop in StarStruck for my two bar, primarily because:

• My knowledge of coding was still developing
• I didn’t know what PID is
• The elements were massive so there wasn’t a need for something so precise