Stacking Higher: Tech Discussion and Videos

During my RI3D with 448, 21, 1437, and a few other people, we experimented with different configurations before settling on the one seen in our reveal. A lot of our process will be in the documentary, but I wanted to open up some broader technical discussion to the whole community.

The biggest challenge by far of our RI3D and (I think) more generally of this game is stack height. The rollers, even with 2 motors and high compression, weren’t able to push more than 6-7 cubes up the magazine. In order to get more torque, the friction of the cubes against the magazine would need to be lower (lexan would help), the angle of the magazine would need to be lowered which raises COM concerns with a tall stack, or some sort of roller or pusher or something would need to assist the rollers by pushing cubes up the magazine a few cubes up the stack. It may be possible to use the tilter motor, maybe with clever gearing or a basic differential, to spin a wheel or move an arm that would help, or it may be more efficient to use a 1 motor side roller like this:

and dedicate the other motor to a stack assist of some sort. There are probably a lot of ways to make a “stack assister” and one of the purposes of this thread is to brainstorm how to create one.

The other aspect of stacking higher is expanding the magazine. Our RI3D, and some other notable reveals as well:

use a single, unfolding, static stage that allows for stacks of 6-7 cubes. But what if a passive elevator design or something similar was used instead? Something like this:

Not only would this allow for taller stacks, but it would be more compact when the robot wasn’t carrying around a stack, and it wouldn’t require a deploy. It seems like this type of design is unequivocally better. But this particular design is concerning because steel sliders are so heavy and bulky. Is there a way to make a more compact custom elevator? Maybe with lexan? Is there another way to do the magazine that doesn’t require linear motion? I’m not sure. And that’s the other thing I want this thread to be about.

This community has collectively become talented and experienced enough I feel like we’re already on the brink of figuring out this game. A robot capable of 10-12 stacks at side roller speed would probably be extremely competitive, even by late season. Brainstorm away!


You could use string instead of linear slides couldn’t you?

I tried build my string intake and the biggest problem was that a substantialy large and constant force needs to be applied. I couldn’t figure out how to do it passively.

There is the possibility of using a motor although it does need to apply a large force without turning and overheating could be an issue. You could however solve this by having two gears rubberbanded together and non-backdrivable mechanism connect it to the motor. This way the motor will turn to a spot and stay there and gears will turn together untill the one connected to the string cannot any more. The other gear will turn a bit further than that. This way it will pull the other gear therefore applying constant pull without overheating the motor.

This could also be combined with a passive claw.


I think as the season progressed we’ll see 3 stage trays. I’ve also found that with rollers, single rollers on each side instead of treads connecting 2 sprockets are more effective. the biggest issue I’ve encountered is where the second stage of the tray goes when compacted, and how it’s banded to deploy. I found that the second stage of the tray is best compacted into the front of the first stage, rather than behind the first stage. and for the third stage, some sort of linear slides would probably be the best imo.

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As far as string goes, bumping your robot could cause the stack to fall over. Is there a way to do a tray without string?

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Ok second thought: is there a way we could use c channels inlaid in each other with bearings similar to a cascade lift for a tray?

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Although bumping might still be an issue.


Also, if u have less than the full stack, the cubes will slide around.


What do you mean? The string is always pulled to the right length. It winds/unwinds on a spool. It isn’t in that video but you can see it here.

I am confused what is a single roller? I thought rollers were sprockets with chain and chain with flaps (vex website calls them Conveyor-belt Base Links and Conveyor-belt Inserts)

@Xenon27 is referring to side roller intake… which was very popular during gateway and tossup.


Do you mean something like this


so the spool is motorized? otherwise how do you keep the string unwound to the right length?

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First the idea was to have it be passive (rubber band get wound up and pulls the more rope that get unwound or something like that) but I am not sure that passive would works so it would most likely be motorized.

I did mean side rollers like @meng said. I experimented with rollers and to me sing side rollers using the largest flaps on 18t sprockets spaced 15 holes apart and raised about 3” above the ground

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Yes… this is side roller intake.


People often neglect latex tubing, it is legal I believe and it has a much more consistent stretch than a rubber band. Where as a rubber band becomes incredibly hard to stretch and even risks snapping if over stretched. Not to mention the elastic force of a rubber band increases exponentially when stretched.

Personally, I have a linear slide mechanism that I’m not willing to leek. It applies pressure on the cubes from the topmost cube. If you know anything about physics, increasing the normal force between two objects also increases the static friction between two objects. So having some sort of pressure plate on the top of a stack will stabilize it much more than just letting the cubes rest freely within an intake. This is somewhat demonstrated in the string video where the guy is able to sway the stack without having any cubes shift.

But I can say that it is fully cadded and in theory, it should weigh under 2 pounds (based on the specs of weight for different parts on the vex website). Lexan is a really good material, and aluminum is also good against the cubes because the surface of the cubes slides against aluminum fairly easily.

My main problem is getting the friction of the sliding mechanism to be really low and also not having much, if any, wiggle room with the design. Also having constant tension throughout the expansion mechanism. I have an idea for constant tension but I have not tested it out yet.

(for my design) Basically, as you load cubes up, you want to be able to control how much tension is applied to the cubes from the top because as you deposit you won’t be able to release a stack without being able to release the tension. One way to over come that issue is to have a linear lift, so that you can release a stack vertically and at the same time control the amount of tension.

Any other ideas, questions? I’m curious what other people have in mind.


well… we do have a few other variations going on in the lab. but as usual, we will do our reveals after singvex (which is next monday and tuesday).

and yes - i am glad to declare that 8059 Ri1D has just started :slight_smile:


Sweet, the 8059 reveals are always awesome


Will singvex get streamed?


Oh no…
In fact, nowadays singvex is a non-official event.
No awarding of worlds spots, just fighting for bragging rights between the powerhouse teams :stuck_out_tongue: