233 telescoping arms how do they work?

[smart1]

i have seen pictures but i still can't figure how they work. I want to know how to make one this summer. any pics or cad would be great.

[ehfeinberg]

Although I can't vouch for the pink team, on FRC-Designs team 75 has posted a CAD of their 2011 robot with a telescoping arm.

48 also seems to have a telescoping arm, but theirs uses a pneumatic cylinder instead of a lead screw for the telescoping motion.

I would still like to hear how 233 (and 2016) did their telescoping arms.

[Nemo]

I had a chance to ask 254 a bunch of questions about theirs. Thanks to 254 for having a model out for fan boys and girls to look at and answering lots of questions. I was trying to explain some of it to people, but if somebody has a nice picture of a 233 or 254 arm, that make it a lot easier for us to develop something of our own. Figuring out a good telescoping arm that we're capable of fabricating is high on our list of generally useful things we want to learn how to do.

[ehfeinberg]

Originally Posted by Nemo

I had a chance to ask 254 a bunch of questions about theirs. Thanks to 254 for having a model out for fan boys and girls to look at and answering lots of questions. I was trying to explain some of it to people, but if somebody has a nice picture of a 233 or 254 arm, that make it a lot easier for us to develop something of our own. Figuring out a good telescoping arm that we're capable of fabricating is high on our list of generally useful things we want to learn how to do.

I don't believe 254 ever made a telescoping arm. Wicked fast elevator, yes. But telescoping arm, I believe not.

About 233, not a picture but a video.
Here is a picture, but you cant really see anything close up...

[Thad House]

Originally Posted by ehfeinberg

I don't believe 254 ever made a telescoping arm. Wicked fast elevator, yes. But telescoping arm, I believe not.

About 233, not a picture but a video.
Here is a picture, but you cant really see anything close up...

254 used 2 233 style telescoping arms for their 30 point climber this year, and had a spare one for people to look at at championships this year. It was really cool, but I could not explain it even if i tried.

[smart1]

they had 2 this year on their climber.

[R1ffSurf3r]

I'm on sketchy Internet in Germany right now so I can't post any pics, but the arm is relatively simple. Our best example would definitely be 2011, which in my opinion is the best robot 233 has ever produced.

We use three different sizes of box tube, with fancy bearing blocks holding it all together. The telescoping action is powered by a motor at the bottom and chain.

The most complicated pieces are probably the bearing blocks. I believe they are cut with a wire edm and milled, and everything moves smoothly with rollers. Its hard to explain without pics, but there are blocks on the inside of the tops of the tubes, and the outsides of the bottom of the tubes. If you find a good pic this will make a lot more sense. We keep about 6 inches of overlap when fully extended. In 2010 we tried out using waterjetted delrin in place of these rollers and blocks, and honestly it just sucked so don't bother.

Some other cool features of the arm include dual constant force springs that entirely counterbalance the telescoping portion, and a less slick system of surgical tube to balance the rotation. There are also delrin springs that act as shock absorbers when the arm retracts and slams closed. For rotation the whole arm sits in split bearings. But honestly the coolest addition to the 2011 iteration is how the rotation was powered. Instead of using chain like usual, there was one giant wire edm cut gear that fit directly to the arm.

Now all of these features aren't entirely necessary for an effective arm, but are the result of continuous improvement over the years. Effective programming and intuitive driver control should be considered the highest priorities in my opinion.

[coalhot]

Originally Posted by bliz213

My team came to Champs this year with the goal to scout robots, sadly not to compete. A small crew of my team members and I went to close to 70 teams and took close up pictures of different their robots.

https://www.dropbox.com/sh/3fxabc28nvvkcr8/A2tQie9tgK

We spent Friday and Saturday running from pit to pit to get all of these pictures. There are close to 1000 pictures neatly organized by team number.

Hope those teams that couldn't make it can enjoy these pictures.

From one of the post photos threads. Look at 254's set, there are a few really good shots of the arm, and the bearing assemblies it rides on.

[smart1]

thanks for the pics

[Mike Marandola]

Originally Posted by coalhot

From one of the post photos threads. Look at 254's set, there are a few really good shots of the arm, and the bearing assemblies it rides on.

This is awesome. I wasn't able to check out some robots up close at worlds so this is great.

[Tom Line]

I understand the structure - the roller bearings and ball bearings etc.

How exactly are the belts driven and cascaded through the system? I'm not seeing how they are connected or function.

[coalhot]

Originally Posted by Tom Line

I understand the structure - the roller bearings and ball bearings etc.

How exactly are the belts driven and cascaded through the system? I'm not seeing how they are connected or function.

I'm not sure. The closest photo I could find is this.

Maybe someone from 254 or 233 could chime in, or you could spend about an hour looking at old 233 posts. I remember coming across a thread where 233 explained how their arm extended and operated (2007 version). Also, 254 talked about how theirs worked in the 7 second climb revel thread.

If I remember correctly (and don't quote me on this), 233 used a spring extend, while 254 didn't.

[ablatner]

I remember it's a single belt going all the way through that's fixed to the stage that extends the most. I could figure out the belt path and pulleys from memory, but I'd have to spend some time drawing it out.

[DampRobot]

Originally Posted by Tom Line

I understand the structure - the roller bearings and ball bearings etc.

How exactly are the belts driven and cascaded through the system? I'm not seeing how they are connected or function.

Imagine a single stage system for simplicity. The belt is pulled by a pulley at the bottom of the "zeroth" stage, and runs over a idler at the top of the zeroth stage. The belt then connects to the bottom of the first moving stage. When the stages are together, the length of the belt is ~2*stage length. When the first stage is extended, the length of the belt is ~1*stage length. Retraction works in the opposite way.

A two stage system works similarly, but with the bottom and top of the first stage being idlers, and the belt being connected to the bottom of the second stage.

I believe there's a pretty good paper on CD-Media which explain all of this in more detail.

[coalhot]

Also, specifics on this thread link

Spending a few minutes searching can get you a long ways along...