Best Double Reverse Four Bar Examples?

Lots of people seem to lean towards the DR4B lift this year. I wanted to make a thread based on some of the best DR4B’s we have seen these past years of VEX.

Please, if you can, include video examples.

Seriously, this thing is so stable, I’ve felt it myself and it’s just insane.
If you’re going for speed, 134D looked pretty good last year.

If you’ll excuse the music, we had a great time with our 11.7:1 RD4B during Skyrise.

Here’s one that’s a pretty basic design

BNS Skyrise:

BNS Starstruck:

1 Like

What’s the best ratio to use for a good balance of speed and torque on a DR4B?

1:7? 1:5.625?

(Ratios written Driving:Driven, so all ratios written provide higher torque)

In my opinion, a 1:7 high torque ratio would be good if you were lifting a mobile goal.

That entirely depends on what you are trying to lift and how high you are trying to lift it.

2587Z in 2015 Skyrise uses a DR6B and uses the the torque ratio of 7:1 with pistons and many rubber bands, and it is not insanely fast, so I’m guessing that 7:1 is the way to go.

I’ve been looking through the examples above but one thing puzzles me. How do the robots balance out their weight while being raised in the air? Most of these robots are clearly not dropping any sort of counter-balance device at the start of operation so are they using the batteries and cortex as a balance or is there something i’m missing.

Generally using elastics rather than weight, ill draw up a sketch,
edit: blue represents band possible positions
DR4B sketch.png

Has anyone had a lot of experience with using only two motors on there lift.

sure, i have one that works with only two motors all you have to do is balance the weight with rubber bands, and then all your motors have to do is move the inertia of the lift

so do we I guess im trying to gather more data and input on how well it is working for others.