So what exactly is a Danny lift? And what are the benefits of it and how is it different than a 4 bar? And also, as we have to work somewhere else for the next week, we have to make sure exactly which parts to bring to make the Danny lift. So can you give us a list of what we need or a CAD drawing?
Thank you in advance,
Rougescales,
P.S. I know. This is a lot. But I am very new to VEX and started only about 8 months ago. I seriously have no idea what I’m doing.
A danny lift is a double reverse four bar (dr4b) with both the top and bottom pieces the same length, so the top of the arm moves linearly instead of at an arc. It’s built exactly the same as a standard dr4b, just making sure the lengths are the same. You can find countless pictures/videos of dr4bs and how they’re built on Youtube and across the forums, as they’re a popular choice this season
You just described the way a dr4b should be built to be perfectly linear… this is why the danny lift should not have it’s own name because it is literally just a dr4b lol
Indeed it is, and that’s why a lot of people get confused as to what it actually is, because in truth it’s just a specific kind of dr4b.
It’s also really not all that great.
Here’s a link to a video about it:
You don’t get consistent linear movement, your lift just maxes out at a much different point. During Skyrise I messed around with the concept of one, but quickly came to realize that it was a really terrible lift.
How is it so bad when it’s just a dr4b?
It loses all of the good traits of a DR4B in favor of going fully vertical, which makes the lift extremely unstable and shifts your center of gravity far more drastically than a standard DR4B.
Additionally, this lift does not scale well; the max extension on this lift was only about 30" and while that may be enough for a game like this year’s, this concept was initially conceived during Skyrise, where teams generally ended up going up to 80". Adding a third tier to this would up your MAX extension to 45", but you’ll run into even greater stability issues and an even more terrible CoG with an added tier.
If you want a linear lift, I’d really suggest considering other options.
I understand. However, you could easily design it so that both motors are placed at the bottom, and if you use that as your top tier, maybe it’s not bad?
Were using the danny lift for the arm. Not the DR4B itself. We use a DR4B AND a danny lift. We are replacing our chain bar arm with a danny lift bar
So… you are having a dr4b on top of your dr4b…
As @meng said, a DR4B on top of DR4B? If I understand correctly what you’re suggesting, then this is useless. I believe you don’t understand Danny lifts correctly. They are supposed to be linear, as are DR4B’s (they’re basically the same thing). The point of a chainbar on the top of the DR4B is to provide translational motion, which is needed for internal stacking. It seems you will be going from an internal stacker to an external stacker… may I ask why? The robots have evolved throughout the season and it has been seen that there are almost no external stackers among the top robots.
I suspect they’re putting a 4-bar (single, not DR4B) on in place of a chainbar attached to their DR4B. That would be to remain an internal stacker. But it wasn’t stated that way, making it sound like two DR4B’s on top of each other instead of having a shared arm. Though two DR4B’s could still be used for internal stacking, I doubt moving the stack back and forth underneath a linear lift would be very efficient. So @meng and @Easton questioning the substitution makes a lot of sense.
As for “translational motion,” that is the point of basically any 4-bar, forget if it’s a DR4B or not. Same thing with a chain bar. Though in both cases you could make a rare choice to avoid purely translational motion.
I wanna make a tr4b now
It will be easier to do a scissor lift instead of a tr4b.
I am guessing you tried 
@meng always with the reality check
Sorry for the late reply. As @Callen said, we are putting a 4 bar on top of the DR4B for stacking. But I’m not sure what we’re doing either!