Team 2980's Open Source FIRST BOT

[eedoga]

Team 2980 has decided to go completely open source. We will be posting everything about our robot, how its put together, how it works out...Everything. We don't mean for this to spoil creativity, more because we have gotten so much from the users of this forum and we feel it is our responsibility to start contributing. So here goes.


This is a back view of our robot. The base is 27" wide, 37" long, and 8" inches tall. The wheels are Mecanum and will be driven by 4 CIM motors. The arm will be driven by window washer motors.

Here is how we are mounting our Denso windshield washer motors

The minibot will be mounted on the platform on the back, and will be deployed using a 20" piston. We are planning on mounting the platform on a turn table so that if it isn't lined up right the cavity in the platform will help orient the minibot.

We only have a flat view of our gripper, but that will be mounted upside down on the arm. The idea is that the arm will flip around to the front. A camera will be mounted on the arm.

STP files are available upon request. We would love feedback on the design. and will keep this thread up to date as we make progress.

Thanks.

Edoga 2980

[Jester]

I would love to give you feedback, but your pictures aren't loading for me

[AllenGregoryIV]

I like the window motor to sprocket mount. We might use that at some point.

What are some stats of your robot? How fast is it going to go? (what are the gearboxes and gear ratio?)

How high is it going to be able to reach?

Keep updating I love the idea of giving away designs to other teams, it just makes sense.

[eedoga]

So our current design uses 4 wheel mecanum drive. We have the tough boxes set up in the standard gear ratio of 12.75 to 1. We are using 6 inch wheels....Not sure how fast it will go...We have only used 8 inch sticky wheels in the past, or the slippery wheels we used for lunacy.

The arm in its current design has a maximum reach of 8' 8" not including the gripper which adds a few inches. We are hoping to squeeze a few more inches out of the sliding mechanism and to make the arm a few inches longer, but we were not originally planning to go for the top row. (last year we tried to do everything and ended up doing nothing much.) We would love to do more, but we currently only have access to a band saw, drill press, welder, and angle grinder. :-)


This is the tower that our arm sits on. it is 1 inch aluminum that we are drilling 1/2 inch holes in.


This is the arm, we are using a 60 tooth sprocket to turn it. We figured out a way to use the key shaft to couple the sprocket to the arm so we won't be using the set screws as depicted in the model. We should have updated pics by the end of the weekend. We are using the slides to extend the arm. We had to cut 4 inches off of the ends of a 3rd slide to give us 28 inches of travel.

Here is an exploded view.

This is how we are mounting our jaguars. We are doing this so that each motor is a unit


Thanks,

Edoga 2980

[eedoga]

So we are hoping to get our robot running by the end of the day tomorrow. It really depends on how well we can pull together. Putting in 2 weekend days every week has been amazing, and has made the whole process a lot less stressful...though tiring.



Here is what we have...pretty much...so far. I think we added a bit more with the pneumatics system after this picture was taken. We have the electronics roughed in, and we are starting to rough in the pneumatics. I realized we have a frame perimeter violation that we need to fix tomorrow. One of the linear bearings for deploying the "baby bot" sticks out past the frame barrier so we have to shift that over by an inch to make sure we don't violate any rules.
If you look carefully you can see it closest to the camera...Probably should have caught that in the CAD model. We should have a rough idea as to how much this thing weighs tomorrow. It feels heafty, but hopefully not too heavy.

Here is a pic of our gripper. I think we are adding surgical tubing to make it stick to the shapes a bit better... The back part of the top of the gripper is wood...We ran out of 1/8th aluminum sheet...We are also pretty much out of money so...

To be honest I'm amazed with how much like the CAD model the robot is turning out. Last year we only had 2D CAD, and only one person knew how to use it.

This design was done using turbocad deluxe. Next year we should have a team that knows how to use AutoDesk Inventor. We are just growing and growing.

I'm hoping we can post tutorials on all of our different sub systems early next week.

[eedoga]

Things are going so smoothly I'm starting to get scared. We drove our robot today. It took a little figuring out, and some polarity switching at the motors, but we drove our robot today...And not even as a last minute thing, we drove it before we broke for lunch. Not only did we drive it then, but we got to drive it a bit after. Our driver said "I am amazed that it drives so smoothly." We've never had that happen before. We also finished welding the tower, and the arm, and got up to the first arm segment roughed in. We even got to clean the classroom up. :-)

Ok...So some pictures.

In this pick the second arm segment is just stuck in. We still haven't mounted the linear bearings that will allow it to slide back and forth. We also haven't plummed or wired the piston, or mounted the cable organizers that will allow the arm to move back and forth without ripping the wires out.


This is a much better indicator of our actual progress. We may paint the base purple and the arm gold (our school colors) but I sort of doubt that that will happen before the competition. We may do it after the competition to help raise money and awareness for next year.


This shows a close up of how the arm rotation is going to work. The window washer motor is mounted below in back. The sprocket has two holes drilled and tapped to 1/4 * 20. We used the shaft from the gearbox that came with this years kit linked to the large sprocket on the other side. Some 1/2 inch inside diameter bearings complete it all so that power can be transferred from the 60 toothed gear to the arm. The gear ratio between the windshield wiper motor and the large gear is 1:2, so I'm hoping the motor will be able to turn the arm, while retaining a reasonable turning rate. If that fails, plan B is to add a second windshield wiper motor on the other side and tie the two together.


Here is a close up of our electronics bay. We are still trying to kill the spaghetti monster lurking in there. you can also see the Pneumatics which are coming along nicely. We are using two smaller tanks, and the bigger tank that came with this years kit of parts. We figure filling the 20 inch * 2 piston we are using to deploy the minibot will use up most of the stored air even though its on the low power side of the system.


Here you can see the relief valve and power switch which are both accessible without reaching in the way of any moving parts, or anything sharp. We are a bit concerned about the gauge that is mounted on the top of the frame rail might get hit by something if another team carelessly hits it, but hopefully not.

We weighed the base, and it was only 89 pounds with everything except the tower, arm, and battery. (Battery isn't included in the weight limit). The tower weighed in at about 5, and the arm was only about 8 total, so we are actually looking at coming in right around the perfect weight. (Again, something that has never happened to us before.)

We still have a lot of work to do, our minibot is still a figment of our imagination. We also have to finish up the arm extension, and then do a final tear down, prep, and rebuild where we use locktite on all the nuts, and make sure everything is where it should be. All in all, a great day for 2980!

[cire]

Very detailed description and nice pictures. I like what you are doing here, keep it up.

[mwtidd]

Can I ask why you chose to offset the arm to the left? Seems like an interesting design decision.

BTW the open source idea is awesome. I'm surprised more teams don't step out from behind the curtain.
I'm glad to see your team is taking a step in a nice direction.

[Nadav Zingerman]

I think you should consider how you will be covering up that giant sprocket. It would probably not pass inspection for safety in it's current form.

[Leav]

Originally Posted by Nadav Zingerman

I think you should consider how you will be covering up that giant sprocket. It would probably not pass inspection for safety in it's current form.

Even though it looks like a circular saw, it isn't very dangerous. many robots with a similar giant sprocket on an arm passed inspection in 2008, and I don't see why that would change in 2011.

[eedoga]

FIRST off, Thank you for the kind words.

We were thinking we would cut some lexane sheets and thin aluminum u brackets to minimize the risk of someone getting a finger caught in there. Another idea was to go get a bicycle chain cover from the recycling center and then make a bracket to mount over it. At this point it is a thought in the back of our mind...Of course the problem with covering it is that to cover it might increase the likely hood of fingers getting caught up. by creating new pinch points.

The arm and babybot launcher are offset to increase the length of the arm, and decrease the likely hood of an interaction between either of them. In its current configuration the arm will be able to reach well over 9 feet.

The camera will be mounted on a bracket on the side of the arm. This way we can use the camera during the autonomous period, and our driver can use it to line up both getting pieces and deploying the minibot. We are hoping that our driver will be able to see well enough to place the pieces on our side. If not the camera will provide the driver with an upside down view of the scoring grid.

Edoga

[Nadav Zingerman]

Originally Posted by Leav

Even though it looks like a circular saw, it isn't very dangerous. many robots with a similar giant sprocket on an arm passed inspection in 2008, and I don't see why that would change in 2011.

My concern isn't that it will cut something, as it is not going that fast, but rather that someone will their hair or finger caught in there. The sprocket must be entirely covered to prevent this. You might get away with just covering the bottom where the gears mesh, it's really a judgment call.

[Tristan Lall]

Originally Posted by Nadav Zingerman

My concern isn't that it will cut something, as it is not going that fast, but rather that someone will their hair or finger caught in there. The sprocket must be entirely covered to prevent this.

It's not even the sprocket itself that is the most significant hazard—rather, it's the point where the chain wraps around the sprocket.

Generally speaking, this is not an issue at inspection, however the precedents* for that are complicated. In 2006, for example, based upon guidance issued to robot inspectors, FIRST was adamant that the test for hazards in ball-shooting devices ought to follow from modern North American industrial practice, where finger-sized (or larger) pinch points on moving mechanisms are generally guarded. Although there were various exceptions made (mainly because that was rather difficult to implement when these mechanisms had to release balls), technically, the drive sprockets for shooter mechanisms had to be protected, because there were pinch points there. This led to quite a few unexpected rejections at inspection.

In more recent years, even with similar rules, the interpretation has been drastically different—presumably in recognition of the fact that FIRST robots are all dangerous if you stick your hand inside, but tend to be significantly less hazardous at a distance. To that end, nowadays only the most evil of mechanisms will get singled out because of close-range hazards.

In fact, you're much more likely to be called on it because of entanglement, than because of the hazard to humans. (A robot that gets its arm looped into there, or something.)

That doesn't relieve teams of the responsibility to minimize the risks to their pit crews. There's plenty of impetus for that flowing from real-world implications—but there's no universal standard or right answer to the question of "how safe is safe enough?".

*Bear in mind that precedents (recorded or not) are of limited value, firstly because the rules change every year, and secondly because FIRST doesn't recognize them as authoritative sources, even when the rules are the same. They're only guidance, made relevant principally because of the desire to keep things consistent.

[Leav]

Originally Posted by Nadav Zingerman

My concern isn't that it will cut something, as it is not going that fast, but rather that someone will their hair or finger caught in there. The sprocket must be entirely covered to prevent this. You might get away with just covering the bottom where the gears mesh, it's really a judgment call.

I see your point now, but I still disagree... The robots are very dangerous when powered, no matter what safety precautions are introduced.

I think that In the past the requirement was mostly focused on stuff which are unsafe when the robot is turned off, for example springs which store energy (2008,2010 mostly), or the requirement for a quick release valve for pneumatic systems to make sure it's easy to disarm the pneumatic pistons.

It is always a good idea to make the robot more safe, but one should be careful from being lulled into a false sense of security and safety.

[Nadav Zingerman]

Originally Posted by Tristan Lall

It's not even the sprocket itself that is the most significant hazard—rather, it's the point where the chain wraps around the sprocket.

Generally speaking, this is not an issue at inspection, however the precedents* for that are complicated. In 2006, for example, based upon guidance issued to robot inspectors, FIRST was adamant that the test for hazards in ball-shooting devices ought to follow from modern North American industrial practice, where finger-sized (or larger) pinch points on moving mechanisms are generally guarded. Although there were various exceptions made (mainly because that was rather difficult to implement when these mechanisms had to release balls), technically, the drive sprockets for shooter mechanisms had to be protected, because there were pinch points there. This led to quite a few unexpected rejections at inspection.

In more recent years, even with similar rules, the interpretation has been drastically different—presumably in recognition of the fact that FIRST robots are all dangerous if you stick your hand inside, but tend to be significantly less hazardous at a distance. To that end, nowadays only the most evil of mechanisms will get singled out because of close-range hazards.

In fact, you're much more likely to be called on it because of entanglement, than because of the hazard to humans. (A robot that gets its arm looped into there, or something.)

That doesn't relieve teams of the responsibility to minimize the risks to their pit crews. There's plenty of impetus for that flowing from real-world implications—but there's no universal standard or right answer to the question of "how safe is safe enough?".

*Bear in mind that precedents (recorded or not) are of limited value, firstly because the rules change every year, and secondly because FIRST doesn't recognize them as authoritative sources, even when the rules are the same. They're only guidance, made relevant principally because of the desire to keep things consistent.

You're right, I was basing my opinion on precedents mostly. It's up to the team to determine if they are comfortable around that sprocket, safety-wise and inspection-wise. I would personally want to cover it up.