ScissorsLift vs. DoubleJointed Arm.

[Joe_Widen]

What would you say the Pros and Cons are for both. Also, please vote in the poll. And can you post picture, or links to pictures of past double jointed arms or scissor lifts. Thank you.

[DonRotolo]

Poll?

Scissors Lift suffers fron robustness problems, kinda floppy and each joint is critical. DJ Arm is often heavier and technically more challenging, but stable, strong and potentially more robust

Don

[eshteyn]

Both can be used for their own purposes. However i like the scissor lift better because if you build it to support all 4 corners it will be a lot more stable and safer. the most important part is to have cross bars and the joints must be made very well

[Lil' Lavery]

Scissor lifts are (typically) more difficult to manufacture, more complex, heavier, and often slower. Additionally, they cannot articulate as accurately, or create any horizontal displacement or manipulation.

[kjohnson]

From an engineering standpoint (even though I'm not an engineer by any means) a scissor lift is not meant to work without springs and/or pneumatics. To build a scissor lift that is robust enough to not sway would take considerable weight, and you may not have enough weight left over for a full pneumatics system. Also, I believe springs are still outlawed in the rules.

I guess this makes a double jointed arm your best choice.

[Rick TYler]

It's a lot harder to build a good scissors lift than an arm. I assume the OP was talking about a device to lift tubes, right? I wouldn't use a scissors lift unless I was picking up something heavy. You could build a pretty light arm for the tubes, although it's tempting to build a heavier one that could right the robot if it tips.

[DB_UPS]

Originally Posted by eshteyn

Both can be used for their own purposes. However i like the scissor lift better because if you build it to support all 4 corners it will be a lot more stable and safer. the most important part is to have cross bars and the joints must be made very well

Thank you, thats is the same points i brought up.

[Donut]

Uh, neither? Our team has had bad experiences with both; a scissor lift in 2002 had trouble supporting any kind of weight at all (similarly, team 898 from next door to us tried it in 2004 and had to toss it when it couldn't support weight), and a double jointed arm in 2003 could not even support its own weight and destroyed itself (part of this was due to a miscalculation in the strain on sprockets, but regardless it still wouldn't have gone well).

We're convinced the way to go is a combination elevator/arm like we used in 2005; we've already decided we'll be doing it for this year's bot, it's just a question of exactly how they are given power to move that is up now.

[Joe_Widen]

My team and I were having a debate, and for some reason there was a red flag shooting up in my mind whenever I hear scissor lift. I'm just trying to figure out what the red flag is....?

[Guru]

Originally Posted by nukemknight

Also, I believe springs are still outlawed in the rules.

I believe energy storage through springs is perfectly legal, although i cant find the rule right at this moment.

[Jonathan Norris]

Originally Posted by Joe_Widen

My team and I were having a debate, and for some reason there was a red flag shooting up in my mind whenever I hear scissor lift. I'm just trying to figure out what the red flag is....?

you are right whenever I hear scissor lift i see red flags in my head, they are unstable, uncontrollable, and not durable, oh and really really heavy. There really isn't and comparison between scissor lift and a double jointed arm, a properly designed double jointed arm wins. If created properly they can be very controllable and far more flexible than a scissor lift. If you are looking for a vertical moving arm look at an forklift (elevator) type system (111 in 2005 for example). I have only ever seen one, yes one, effective scissor lift.. and too many non-effective ones.

[Cody Carey]

For the application of lifting a robot (or two) 12 inches, none of the sway problems stated above would really apply to the situation, and since you would only need a single joint, neither are the "every joint being critical" arguments. The single joint would allow you to Brace the lift in multiple places.(Shown by red circles in the below picture)

Now, in addition to keeping the scissor lift from swaying, the braces would also keep it from closing all the way, as is pictured below... but that is still adequate for the amount of space we have available to us.

A scissor lift could be a wonderful Idea for this years competition, It just depends which application you are using it for

For a scoring arm, however this would be an entirely different story...

[Joel J]

Originally Posted by Joe_Widen

My team and I were having a debate, and for some reason there was a red flag shooting up in my mind whenever I hear scissor lift. I'm just trying to figure out what the red flag is....?

Maybe its that the best scissor lifts (beings used as an "arm") still ends up being garbage, and is still inferior to a mediocrely designed jointed arm.

[Cody Carey]

I have only ever seen one, yes one, effective scissor lift.. and too many non-effective ones.

These pictures are for you ... They are all "effective" scissor lifts. All that is needed to reveal a wealth of effective Ideas is a look into the past.
Some of what has been being said in this thread is nothing but a bunch of rash generalizations. If you look into Industry... you will see numerous instances of scissor lifts being used, because they are good at what they do. some mechanisms are better than others at certain tasks, It all depends on the application.
You can't just say: "Scissor lifts aren't good because they haven't been made to work yet. They will always be inferior. " It doesn't work that way.

Taken from HERE

Taken From HERE

[Joe_Widen]

Yeh, the scissors lift would be primarily an arm. I think that Mr. Norris nailed it on the head. Maybe I just think that those red flags were more evident. Anyways, feel free to keep posting, I find this quite interesting.