Top 4 Bar Speed

VEX V5 General Discussion Technical Discussion
1

Hi,
I currently have an internally stacking robot with a top four bar currently at 1:3 Turbo, and its moving too slow for me. its made with standoff’s like several top 4 bars are. What are some ways I could make it faster? Like certain ways to rubber band it or is there anything I can do in the code? Thanks.

  • Evan56G
2

Is the lift jittery? As in, is it struggling to get up? If that’s the case, it’s probably best to either rubber band the four bar or change the internal motor gearings to speed or torque if it’s really necessary. If that’s not the case, you can always make the four bar direct drive, assuming you have two motors allocated to the mechanism. I personally haven’t seen a one motor 1:1 four bar, but I doubt it will be possible.

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  • Are your four bar standoffs any longer than 7”? If so, reducing their size means less of a load on the mechanism.
  • Is the motor on your intake (if it has one) as close to the point of rotation as possible? Some teams have their motor on the outside roller, causing a much higher/unbalanced load on the four bar.
  • Try to add just a few rubber bands, as that helps a lot of teams run 1:1.
4

Try and make your intake light, because the less weight the four bar has to lift the faster it will lift.

5

Thanks for the tips. I’ll experiment with rubber banding and see if there anything I can remove as far a weight. The standoffs are only 6" and the motor is in the middle of the roller intake, so its fairly balanced, but I can probably remove a few things.

6

Are you using half c channel at all? The strength of a full piece is not needed on something with so little stress being put on it, and it’s a good way to reduce a lot of weight.

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I am using half C-channel in some places. I think I can cut down even further though.

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For coding, I would use PID on the lift, while it doesn’t increase speed directly, it will keep the lift very stable which will put less stress on a certain motor. Which in turn will make your lift be able to go up easier. Also for your intake, using a passive intake out of polycarbonate plastic will reduce your weight of your lift. Also Turbo motors have little torque which will make the lift slowish, I would recommend using High speed motors (using high speed gearing) or even standard ones. We use standard motors on our lift without modification to the gearing, and we have a quick lift. Also we were using 35’ c-channels for our arm (the part that connect the arm to the tower) and we were pretty good as far as speed is goes. Definitely use 25’ c-channels for the part of the arm that connects the arm with the tower. We did have PID on everything so it was more stable.

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It seems to me that you are talking about the primary lift. OP was referring to a secondary lift.
@Evan56G go crazy with weight saving on EVERYTHING that’s on your rollers/4bar. For example, I use ziptied bearings and 1 x L channels. I only use 1 motor screw (I know it’s kind of extreme). Using nylon screws would also be a good idea, as would be using aluminum screws. I also got rid of some of the structure parts of our rollers for weight reduction, and all of this helped a lot.

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Yeah, just noticed that, I meant to talk about the four-bar, ignore the part of with the 25’ and 35’ connecting c-channels to the tower. In summary, using a passive intake would save a lot of weight, and using PID would make the four-bar faster. Sorry for the confusion.

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