Team 2980 2013 Open Source Robot

[eedoga]

Hey All,


So we are making progress, slowly, but progress none the less. Our frame is starting to come together. Our robot looks a lot like a cube right now...We'll have to figure out how to break up the shape to make it more visually attractive, but it it coming together nicely.

We are in a sort of holding pattern though, We are having a few parts cut out for us by a material sponsor/mentor. We can't really continue doing much until those things get done.

We also have a small sub team that is welding up our frame. So again, until the frame is done being welded and powder coated, we will be waiting patiently. During the down time some members have been planning out our pit area. Some of the team members are researching for our theme this year. Some are working on our robot reveal video...This one has stunts and fast cars in it!

Me...I am a happy lead mentor who is actually stress free during build season for the first time ever. This plan of ours will work, or it won't, and if it doesn't we will modify it until it does...

Here is to turning a bunch of 1s and 0s into cold hard reality.

Edoga

[eedoga]

We've started the programing and building the electronics. We just got a large shipment of gears, gearboxes, bumper materials, and other parts, so it's a lot like Christmas around here.

[Nuttyman54]

This is a really neat design. Have you guys prototyped the climbing tri-wheels at all?

Also, I can't tell how you intend to get the robot from the floor to the climbing orientation.

[eedoga]

Originally Posted by Nuttyman54

This is a really neat design. Have you guys prototyped the climbing tri-wheels at all?

Also, I can't tell how you intend to get the robot from the floor to the climbing orientation.

Hey Nuttyman,

SO...the tri-wheels were a sort of...all or nothing sort of idea. The kids made something out of legos...but as for a genuine prototype I don't think they did anything. I'm sort of hoping they got it right. They modeled it in inventor and are going to town building it/ordering parts...At this point it might be a suicide mission where they end up with no robot. I'm sort of hoping that isn't the case. In the least the idea is that they will keep fixing/figiting until it works.

As for the transition...I'm not sure the kids have figured that one out either. The original idea was to just ram into the pole...There is an arm mechanism that mounts on the top and folds down which they will probably end up using, and they are planning on having the tri-wheels whirring away as they drive into the pole. Worst case they are going to mount a teflon-V in the center square to slide onto pole.

Absolute worst case situation the kids will add a pusher to the back to help tilt the robot up.

great...now I'm worried.

Edoga

[Nuttyman54]

Originally Posted by eedoga

Hey Nuttyman,

SO...the tri-wheels were a sort of...all or nothing sort of idea. The kids made something out of legos...but as for a genuine prototype I don't think they did anything. I'm sort of hoping they got it right. They modeled it in inventor and are going to town building it/ordering parts...At this point it might be a suicide mission where they end up with no robot. I'm sort of hoping that isn't the case. In the least the idea is that they will keep fixing/figiting until it works.

As for the transition...I'm not sure the kids have figured that one out either. The original idea was to just ram into the pole...There is an arm mechanism that mounts on the top and folds down which they will probably end up using, and they are planning on having the tri-wheels whirring away as they drive into the pole. Worst case they are going to mount a teflon-V in the center square to slide onto pole.

Absolute worst case situation the kids will add a pusher to the back to help tilt the robot up.

great...now I'm worried.

Edoga

Lego prototypes are often sufficient, and any prototype is better than nothing. most of your weight is centered around the bar or below, so you shouldn't be dealing a large torque trying to pry your robot off the bar.

As far as getting on to the bar, if driving up it with the tri-wheels spinning doesn't work, I could see a wheelie-bar linkage or two (Like 33's stinger last year) that just props the front of the robot up on omnis and drives on the rear wheels towards the bar. You've got plenty of space on the top of the robot if you need it.


All-or-nothing designs are not inherently a bad thing, and neither is letting the students try and fail. If they're excited about it, that's what matters. If it works, they've really accomplished something. If it doesn't, failure is a very good lesson if you analyze what happened. As long as they learn something either way, it's a successful exercise. Some of my most memorable design lessons came from things that DIDN'T work in FRC (ie don't use set screws instead of keys on a CIM shaft to transmit torque to your drivetrain).

What's your estimated weight at? With all these 5-gallon bucket, pneumatic fed, small wheel banebots shooters we're seeing here on CD, I wouldn't be surprised if you could fab one of those quickly and slap it on top of the robot for a quick HP load 2 or 3pt shooter. If I recall correctly, Discotechs 1099 had a video on youtube where they used the kit-channel as shooter guide rails with great success. Just some food for thought, if you've got the weight I'm not convinced this has to be an all-or-nothing design.

[Paul Copioli]

So I am going to post some things to consider since I really don't want this thing to fail to an unrecoverable point. Here are some questions / suggestions:

1. Are you depending upon the actual weight of the robot to generate the normal force required for the wheels to drive up? If so, please realize that you will need a coefficient of friction greater than 1.732 (tan (60)) to get enough traction no matter what your weight.

2. If not, then your coefficient of friction + other method has to generate an effective coefficient of friction of 1.732 or this will not work.

The above is THE limiting factor for this type of design. I have analyzed this to the nth degree and it is a undeniable fact that you must figure out the traction problem before proceeding down this road. These poles are slippery, really slippery.

I hope it works ...

Paul

[eedoga]

Originally Posted by Paul Copioli

1. please realize that you will need a coefficient of friction greater than 1.732 (tan (60)) to get enough traction no matter what your weight.

2. If not, then your coefficient of friction + other method has to generate an effective coefficient of friction of 1.732 or this will not work.

I hope it works ...

Paul

I shortened the quote but I hope I didn't change the meaning at all.

Hey Paul, I hope it works too, The kids did a bunch of math and then ordered a specific rubber from McMaster Carr. A few sheets of it are here and to be honest it doesn't seam very sticky to me, but if I put any weight on the sheet it is relatively hard to slide across my counters. I'm hoping it is sticky enough, if not I hope we can find a way to find softer/stickier rubber in time.

We may have to go with a stinger or wheelie bar idea, and in I have an idea as to how we could maybe do it, I'll have to look at the cad drawings.

As for the room in the top of the robot, there is a bucket that goes there for dumping disks in the top of the tower.

Thanks for the advice, I'll share it with the kids!

Edoga

[BJC]

Originally Posted by eedoga

I shortened the quote but I hope I didn't change the meaning at all.

Hey Paul, I hope it works too, The kids did a bunch of math and then ordered a specific rubber from McMaster Carr. A few sheets of it are here and to be honest it doesn't seam very sticky to me, but if I put any weight on the sheet it is relatively hard to slide across my counters. I'm hoping it is sticky enough, if not I hope we can find a way to find softer/stickier rubber in time.

We may have to go with a stinger or wheelie bar idea, and in I have an idea as to how we could maybe do it, I'll have to look at the cad drawings.

As for the room in the top of the robot, there is a bucket that goes there for dumping disks in the top of the tower.

Thanks for the advice, I'll share it with the kids!

Edoga

What I believe Paul is getting at is that you can't rely on a tractive surface alone. No rubber from Mcmaster has a CoF of 1.7 on a smooth steel pole, coefficients between two objects must mechanically interlock for the coefficient to get above 1.0 and steel poles really don't offer much of anything to interlock with. Even Roughtop wheels against carpet are only 1.4 when brand new. Basically you need something actually attached/ reaching around the pole to keep the robot from sliding/falling down.. I would have your students begin brainstorming ways to do this so when the traction-only plan doesn't work out you have a plan B.

I really hope you can pull it off.
Good Luck, Bryan

[eedoga]

Looks like we are going with electromagnets run off of a solenoid breakout. I'm hoping this is a legal, and b doesn't melt the battery or cRio. Won't know until wednesday if the magnets we ordered will work, but I have fingers crossed.

Edoga

[eedoga]

http://www.chiefdelphi.com/media/photos/38508?

http://www.chiefdelphi.com/media/photos/38506?

We had a long weekend of welding and cutting, We are almost done with Fabrication and assembly at this point, we are really waiting on a couple of parts which are in the mail, and a couple of things we still need to make. The tri-wheels are going to be a serious challenge to assemble, mostly because they have to be partially assembled in the bracket that holds them into the robot, and because the tolerances of the brackets themselves are super tight. Somehow everything constraining properly in inventor doesn't square up to actual assembly.

We have also been going through mill bits like it is going out of style. For some reason the 1/8th inch bits are super easy to break and we are hand cutting the keyway for our wheel shafts out of aluminum. The goal is to save weight by using aluminum instead of using steel.

course they will still be really heavy. Hopefully not too bad though.

We lost a few hours because we were filming our "robot reveal video" Like last year this one is a doozie...It even includes "stunts" and explosions! :-)

One of the kids said that in addition to micro biology and engineering she wants to be an actor so that someone else can do her hair and makeup...From what I have seen she is a natural. :-)

I will try to get more detailed pictures as we get them.

Edoga

[eedoga]

So in looking at the robot it got ugly in a hurry. Things were coming together pretty well, but a set of brackets we made just came out much uglier than they looked in CADD...I know...aesthetics aren't everything, but the flip side is that the brackets are too narrow and the tri-wheel assembly is grinding on the inside of it. Again, this illustrates the difference between assembling something in Autodesk Inventor and making it in the real world.

So, we are lucky and our material sponsor is going to cut out new brackets for us. We redesigned them so that they are stronger and made from one piece instead of three welded together. The upside is the new brackets give us much more clearance on the inside while saving us critical space on the outside also making the whole thing a major win win...Only lose part is time...We are losing time... :-(

Our team has also become sort of fractured. We designed everything in CADD, and tried to make a layout and plan for the year, but small changes have been made by various people meaning that no one has a complete picture of the overall robot. Our programming team also took off on its own and is doing things no one but them currently understand. I am a bit worried about this.

Today we are doing a "stop build" and we are going to redraw the robot so that everyone can see the big picture. We are sort of dead in the water build wise because we have to have a couple parts made, and some other parts are still in the mail...So we might as well all get caught up and regroup.

Now is the time when everything falls apart before it comes together right!?

Here is to hoping.

Edoga

[eedoga]

Sometimes it is good to stop and take stock of where you are. It feels late in the build season, too late for us to not have seen this thing actually move. Things are going slowly but deliberately, and we hope we have thought of everything. We will post updated CAD files in the next day or so. Hope someone somewhere finds them useful.

Edoga

[cmrnpizzo14]

Originally Posted by eedoga

Hey Nuttyman,

SO...the tri-wheels were a sort of...all or nothing sort of idea. The kids made something out of legos...but as for a genuine prototype I don't think they did anything. I'm sort of hoping they got it right. They modeled it in inventor and are going to town building it/ordering parts...At this point it might be a suicide mission where they end up with no robot. I'm sort of hoping that isn't the case. In the least the idea is that they will keep fixing/figiting until it works.

As for the transition...I'm not sure the kids have figured that one out either. The original idea was to just ram into the pole...There is an arm mechanism that mounts on the top and folds down which they will probably end up using, and they are planning on having the tri-wheels whirring away as they drive into the pole. Worst case they are going to mount a teflon-V in the center square to slide onto pole.

Absolute worst case situation the kids will add a pusher to the back to help tilt the robot up.

great...now I'm worried.

Edoga

I'm not sure if you have already tested this, but our team tested a similar idea when we were making our climber. It worked very well for getting over the knuckles. I don't want to lead you the wrong way, but I think that it should be able to work if you follow Paul's advice.

Goodluck! Can't wait for the real reveal!

[eedoga]

Originally Posted by cmrnpizzo14

I'm not sure if you have already tested this, but our team tested a similar idea when we were making our climber. It worked very well for getting over the knuckles. I don't want to lead you the wrong way, but I think that it should be able to work if you follow Paul's advice.

Goodluck! Can't wait for the real reveal!

Our final brackets came it at 7PM tonight. They look awesome and we will post pics tomorrow.It is tight inside of there, and things are really close to each other...The smaller brackets will be a big help in making everything fit and move the way it should.

I had a dream that the robot worked the other night. In the dream I didn't get to see it go up the pole, but everyone was really happy about it.

We are using electromagnets to stick to the pole. greatly increasing our normal force Hopefully we will be rolling by the end of the day tomorrow, and will get our first test/fitting climb in Monday night.

Edoga

[josephus]

We've powder-coated the robot frame, it looks incredible. Programing is finished and the electronics board has been installed. motors are connected.
-Josephus, 2980 team member