My team is facing some problems with our arm. We are trying to stay 4 feet tall and our arm is going to be 59.96 inches long. It is going to be resting at a 45 degree angle going to the floor. Now here is our problem, it is too long for our base and too short to reach the top. Can anyone help me? I want to keep it at 4 feet taller, no higher. Thank you!
How about trying a double jointed arm. This way you can fold up the arm and still stay within your size limits and reach the top row. There are other methods that you may look into. This is just one idea.
i agree u should do a double jointed
we are going for the 12 inches and we are using the double jointed arm too much like the pic…
also try to set the arm less than the degree mesure u first tried…
Agreed. There are other options (such as a telescoping, or scissor-type) which are also possible, but I think that a double jointed arm is the easiest to do. I’ve had experience working with all three of those types of designs, so if you have any additional questions about them, just ask!
Remember that you are not REQUIRED to reach the top row. Although this is a desirable trait, and there are many ways to achieve it, you do not NEED to be able to do this.
It may turn out that being able to score on the two lower racks, repeatedly and reliably… because you got the arm finished a week earlier and had time to tune and test… is more valuable than stressing over reaching the top row.
Of course this is a question only your team can answer, and I encourage you to push the limits of what your resources (mental, physical and financial) allow you to build… but a robot that gets 6 tubes in a row on the bottom rack will always beat a robot that only gets four on the top.
Jason
P.S. That said, we are going for all three levels… but I do wonder if we are making the best decision.
Some of my unused arm ideas from earlier on in build season:
Both are simplified versions of a double-jointed idea, fit within 38" at start and within 72" when fully extended, and assume a 13" high chassis. I hope they give you a few ideas!
I would look into drawer slides. You could easily add a stage of forklift style elevation with some drawer slides and angle or box aluminum to mount them on, sort of like the 229/217 arm from '05. (A video of this arm design can be found here if how I am describing it is confusing)
Or possibly a spring loaded hinge?
Here is some of th picture of the idea showing where our problem is, maybe this will give a better example of my team’s trouble. (See Below,.zip file) THANKS!!
Robot Pics.zip (624 KB)
Robot Pics.zip (624 KB)
I couldn’t extract your zip archive. No files to extract?
EDIT: thanks, I forgot I had 7-Zip on my computer. Unzipped fine.
try using a program called 7-zip. it works for me using that
Stuffit Expander worked for me on my macbook as well
winRAR also works nicely
but to help answer your problem: you could make your arm a little shorter and have a manipulator that grabs the tubes from the bottom, so it doesnt have to reach all the way to the top, but enough that the top of the tube clears the rack
From the drawing, im not sure exactly how the heights are going to work out. You say the max. height your robot can reach is 107.67’’, which is when your robots arm is completely vertical. To me, that seems fine, as David said, if you pick the tube up from the bottom, you may not have a problem reaching the top spider leg.
From the picture though, the arm is at an angle, making the max. height significantly lower. Is that the problem you were referencing? If so, we can discuss further improvements on the design. 
Have you tried a 4 bar linkage?
Yes and no, the problem is that it is too long for our body and to short to reach the top rack but we have decide to add a third joint like your elbow to fold in the arm in the beginging so it is not too big. THX for all the help! Also, Should we use pnematics or motrs for our torgue? Also, How much torgue (spelling error?) can the motors and other stuff in the K.O.P can handle???
I would strongly suggest using motors, if you can. Pneumatics can be easier to implement in some arm designs, but motors are easier to control accurately. It is also a lot harder to run out of electricity for motors than it is to run out of air. You can find specs on the various motors and pneumatic components in the FIRST Guidelines, Tips, and Good Practices document and the FIRST Pneumatics Manual, both available here.