RD4B With Tray - Attached to Lift or Base?

So my team is considering building a bot with a tray and a rd4b to get the best of both worlds of towers and stacking. Our biggest dilemma is this:

  • attach the tray to the lift as well as the intake and tilter mechanisms
    This would be more heavy and unstable
    BUT have the ability to add to preexisting stacks

  • have the tray pivot on the base and always remain low
    Only intake attached to the lift with the ability to hold 1-2 cubes without the tray (tower scoring)
    Would not be able to add on top of existing stacks
    Avoid top-heaviness and too much for the dr4b to be lifting

Let me clear up a common misconception. You are wasting time by stacking on stacks. Have a longer tray and that’s it. Stacking on stacks is an idea floated time and time again but it has yet to work out for any of the lift tray bots, me included. You’d need a boatload of bands to lift enough cubes to make scoring on top of a pre-existing stack worth it. You’re more than likely going to topple the stack. All of this is true of course only if your robot is able to remain steady and not itself topple from all that weight going up.

To be clear I’m not bashing you. Don’t feel bad for having the idea, it’s just that the reality is that stacking atop preexisting stacks is not feasible in my experiences with my lift tray. It’s possible, though. I’ve been able to stack 4 on 4 with a primitive version of my current robot. It’s feasible to score an 8, lift 3 cubes up, and then intake that 8h cube and score the stack.

Tray lifts main power is their tower swapping ability. Rollers are great at gripping those cubes a weird angles and the tray allows you to quickly swap a cube out in seconds, regardless if it’s fully nested or if it’s at a weird angle.

E: to add onto the design challenges, many robots don’t have a configuration where cubes can shift down when the tray is fully vertical, at least in my region. This allows the stack to be nice and straight on release, which is vital if you plan to put more cubes up. This is a challenge on a lift because it’s a balancing act between maximizing compression and compliancy.


i definitely see what you mean, but one of the reasons i had this idea in the first place is watching liftless tray bots be unable to make a sack when there is one lone cube resting in their scoring zone

Well, if they don’t use sliders or have an end cap then it’s easy to just intake that cube.

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Ideally it would take the best of both worlds, but at the same time it takes the bad parts of each type of robot as well.

Most robots during autonomous are realistically only going to score 5 cubes . How would they then put more cubes on top ,they would then not gain as many points.

optimal tray teams are doing 8 stacks in autonomous. If you have a long tray and the cubes are already scored then you can just intake the stack you stacked and create a higher stack that way. I’d say the extra cubes lift trays can provide is only useful in certain situations. Compared to tube bots I’d say tray bots are much heavier, especially with a longer tray. Mine struggles to lift more than four cubes at once, and that’s with excessive bands.


To be honest, I really dont think traybots will be very practical for stacking on top of existing stacks. Its overly complicated to pull it off with a tray.
I see that being a niche role for claws and cube tubes.


lol what? if there’s a lone cube in the scoring zone just intake it???

If there is one cube in the zone, a tray cant stack, but you can intake the cube which would take out the only obstacle in the way of stacking. I doubt this would happen much late season, but u can do this if it does.

Some Chinese teams can score stacks of 11. There are probably even stacks of 12 that are not featured in youtube videos. As youtube does not work in the People’s Republic of China

Mine is a tray lift and I’ll prove you wrong


Challenge accepted :wink:
If you can do it, then looks like ima going to have to rip you off lol

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I would go with attaching it to the base because if the robot is top heavy, the robot could fall over in a match.

I feel like a base would be more sturdy

The base mount is more sturdy for sure.

My bot has the tray attached to the base, while the dr4b is free to move up and down with the rollers to effectively score and descore cubes in the towers. Sry can’t send pic, can’t leek yet, will do so in future

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In my experience, the tilting mech can be made super light and easily liftable, and it doesn’t make much or a difference if it’s on the ground or on the lift. Putting it on the lift makes things slightly more complicated but your not completely giving up on stacks on stacks. Sticking it on the ground means slightly more stable tilting but the difference is rather small. I think we can all agree that we won’t see crazy stacks on stacks (9 on 9 or whatever) but being able to stick 2 or 3 extra cubes up on pre-existing stacks is an end of match advantage that shouldn’t be ruled out or overlooked.


just put the tray on the lift and have a big tray, don’t add stacks to the towers, not worth it.

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good to see you actually pulled this off

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