Scissort Lift vs. Crane vs. 4-Bar Lift vs. Gas Springs

[dtengineering]

Originally Posted by hipsterjr

I have been curious as to exactly how much force it would take to launch a ball 10 ft at a 60 degree angle. ( for about 7ft high and between 5 and 7 ft horizontal from overpass.) I think arms and lifts are going to be too slow.

Take a look in your physics textbook for kinematics formulas. The math to solve these types of problems is quite simple and is a common part of the Physics 11 curriculum here in BC. My estimates are that to launch the ball six and a half feet (roughly 2m) requires an accelleration of 2g over a distance of 1m.

In other words if you have 20lbs of force behind the ball for about 40" you should be able to get it to go 6 1/2' straight up from the last point you contacted it. To account for your desired 60 degree angle, take a look at breaking a vector down into orthogonal vectors (ie, how much "up" and how much "over" you will need). These are actually quite useful formula for many types of questions and are not that difficult to use and understand.


Jason

[Cory]

Never use scissors lifts is a cardinal rule on our team.

[thefro526]

we used a scissor lift in our 04 year that was plenty fast but it wasn't strong

[Peter Matteson]

Originally Posted by Cory

Never use scissors lifts is a cardinal rule on our team.

For our team too.

[Dan Richardson]

4 Bars With Gas Springs have been used before, and quite effectively. However I feel like not in the way your describing.

http://www.chiefdelphi.com/media/photos/26796

http://www.chiefdelphi.com/media/photos/21477

http://www.chiefdelphi.com/media/photos/27982

Thats 1902, 1369, 217 in 2005, 2056 in 2007 just a few examples that I can think of.

[JHSmentor]

Originally Posted by Stud Man Dan

4 Bars With Gas Springs have been used before, and quite effectively. However I feel like not in the way your describing.

http://www.chiefdelphi.com/media/photos/26796

http://www.chiefdelphi.com/media/photos/21477

http://www.chiefdelphi.com/media/photos/27982

Thats 1902, 1369, 217 in 2005, 2056 in 2007 just a few examples that I can think of.

These are great examples of 4 bar designs - does anyone have some CAD drawings that we can look at for how to opperate something like this (mechanically)? We are a new team and are tossing a lot of ideas around but don't have enough knowledge on any one system to make a good guess.

[Cartwright]

I'm interested why those are your four options. Why not some sort of grabber? A scissor lift is quite difficult and a crane seems quite unwieldy. I don't know...we've not decided on our design, but we haven't really considered lift systems much.

[Greg Needel]

Originally Posted by Peter Matteson

For ours team too.

I agree, never use a scissors lift.

[seanl]

Originally Posted by Greg Needel

I agree, never use a scissors lift.

we had to learn that the hard way although it was extremely powerful, enough to lift a 150lb person. but it was slow and heavy..
you can look at my avatar thats the bot, it does look cool though.

[Ianworld]

From my experience almost every rookie team has to build their one scissor lift to learn firsthand why they're a tough choice for FIRST. In almost every robot situation a different mechanism will be just as effective and really the key point easier to make. A scissor lift requries a large amount of careful machining and has certain issues such as how to start it and stability when fully extended.

I'm a big fan of keeping things simple. This year the object is spherical, a 4 bar linkage on the arm isn't necessary. The main advantage of sucha mechanism is that it keeps an object at one end level throughout the whole motion. A ball is a ball no matter which way you rotate it.

Anyhow think simple and functional. I'm a big fan of just simple rotating arms. You just need to think of the torques and the power necessary to move a ball at a distance.

[AdamC]

Thank you all. We've become very interested in a gripper that pinches the ball from the sides, and retracts into the body of the robot to secure it. It's a real debate as to whether or not we should hurdle the balls, or if just having a powerful robot that can push impeding robots out of the way and run lots of laps. I have a personal want to hurdle, because with 6 robots on the track, running a lot of laps is highly unlikely.
If we do go for hurdling, it will probably be an articulating arm, somewhat along the lines of (I believe it was Swampthing's) robot in '04 (or was it '01? I'll check on that).

[fordchrist675]

scissor lift is also not that sturdy given you have to lift a 10 pound ball up 7 feet kind of a challenge but hell more power to you. crane top heavy, 4 bar lift possible


a forklift hey theres an idea haha

[Bomberofdoom]

Think it's been said in this post before, but our team discussed some of the ideas, especialy the crane idea, and we found out that the crane that we would might want to use would require a 12.7 battery at the back of the crane because of power and balance (center of gravity) issues. It came out to be too dangerous and unreliable.

So IMTeam'sO, don't go for the crane.

[Urban Hawk]

id say use the forklift

[BK Lounge]

i am researching the scissor lift right now. what is the best way to extend it.