30-01-2007 16:53

TD78

Re: pic: FRC488 2007 Robot

Nice!

Some questions:

-what material are you using for the top of your platforms?
-what is the angle of those ramps?
-how much does each "wing" weigh?

Looking good!

30-01-2007 17:03

Madison

Re: pic: FRC488 2007 Robot

The design is shown with 16 mm Polygal sheet (www.polygal.com), a type of corrugated polycarbonate. It's .55 lbs. per square foot, so about 13 lbs. for both sides, and exceptionally rigid. We're considering trading down to something like regular, 1/16" polycarbonate. It's about 50% lighter, but considerably more flexible. It's hard to argue with the rigidity of the Polygal stuff, though.

The ramps are angled at approximately 30* -- and there will also be similar ramps on at least one more side per lift. That may seem to be steep compared to a lot of ramp robots, but the overall height of the ramp is only about 2", so we anticipate most robots ought to be able to clear it with little trouble.

Each 'wing' is weighs entirely too much. If I conservatively overestimate, as the models are missing hardware, I'd say they're about 30 lbs. each right now. They're heavier than we anticipated because the first iteration of the design buckled the rectangular aluminum tubing when we tested it to a safety factor of two. I'll be able to iteratively remove material from the lifts after they're assembled and we're able to better test how well they handle stress.

30-01-2007 17:05

Dylan Gramlich

Re: pic: FRC488 2007 Robot

the teams that drive the long way (38") will not ba able to fit on that ramp though? and if you are relying on them turning they may fall off. i could be looking at this wrong so please help me to better understand your very nice design.

30-01-2007 17:07

Madison

Re: pic: FRC488 2007 Robot

There is no 'step', really. There're deployable ramps on the front and side of each lift for access. In any case, it's about 2" high, so even it were a vertical step, most robots ought to be able to get up with little trouble.

The platforms are 38" x 45" and will accomodate robots of nearly all orientations. They're designed to require a minimum of alignment to function correctly, as we feel strongly that ~75% of all teams will not be able to drive their robot with the accuracy required to line up to ramps. Thus, small deployable ramps on two (or maybe even all three) sides of our lifts mean that teams need only be able to maneuver their robot into an area of about 12 square feet.

30-01-2007 17:08

Dylan Gramlich

Re: pic: FRC488 2007 Robot

sry changed my question. i got the concept after i re-read the post.

30-01-2007 17:20

Lil' Lavery

Re: pic: FRC488 2007 Robot

Have you considered adding "ramps" to the outside edges of the platform, allowing teams to approach and climb then from angles (also allowing wider robots a chance to get on)?

30-01-2007 17:22

Madison

Re: pic: FRC488 2007 Robot

Yes -- they will definitely be present. We're only trying to decide if we'd like them on all three sides or if two will suffice. They're not shown because I'm still trying to come up with a clean way of getting two separate pieces to fall into place and form a neat miter joint at the corners.

30-01-2007 17:28

Rob Colatutto

Re: pic: FRC488 2007 Robot

I'm very interested in your lift mechanisms there under the ramps. What do you use to power them? Looks very intriguing though, one of the more creative designs I have seen thus far. Nice looking model.

30-01-2007 17:45

Madison

Re: pic: FRC488 2007 Robot

The lifts are each comprised of two four bar linkages. Each linkage is driven by a 125 lbf. gas spring that is held closed by a mechanism that's not shown -- it, too, was a fatality of the recent redesign. The gas springs allow the lifting to occur without the need for power or stored air -- so we feel that it should be a reliable mechanism for lifting robots at the last possible moment. Also, we like that the gas springs of the same extension are available in different values of output force, so if we find that 250 lbs. per side is too much or too little force, we can change it quickly and easily.

30-01-2007 21:11

Graham Donaldson

Re: pic: FRC488 2007 Robot

I like! My team was theorizing of something like that. Only second complete Inventor design/photo I've seen of a robot with no ringer capacity (as far as I can tell). Although, it appears to me like you've got a good, steady lifting design that (correct me if I'm wrong) can lift to 12", giving you a guaranteed 60 points, which is very valuable, IMHO. Very nice overall.

Can you shed some light onto what the two small protrusions at the bottom (picture-wise, top right) of the robot are? They look almost like tower supports, but in the bottom right head-on view, there's no tower. Can you describe what they are?

It's interesting to me that for a (I assume) defensive robot you chose the omnis with powered middle wheels. From what I've heard, you could get turned around your axis pretty easily. Did you choose to put two motors to each side to counteract it?

Nice design overall.

31-01-2007 13:15

Madison

Re: pic: FRC488 2007 Robot

We've not abandoned all hope to have a ringer scoring implement, but it's been a secondary priority since day one and so it's been treated as such. We've prototyped manipulators and designed arms, but our push is to do everything we can to first ensure that our lifts are working as well as they possibly can. If after that we have the time and resources to think about adding the arm, we'll do so.

Those are Fisher Price motors coupled to the 42mm BaneBots 256:1 gearboxes. They drive the rotation of the lift mechanisms. The arm, should it be added to the robot, sits in the space between each of those motors.

If we end up acting as a defensive robot, we're prepared to replace two of the omniwheels with a second set of the kitbot wheels for some added resistance to rotation. Our gearboxes are geared lower than kitbot drivetrains and a second motor gives us some extra torque at reasonable speed, so we feel pretty comfortable that our drive is powerful enough to prevent many teams from scoring.

Thanks.

31-01-2007 13:22

Dave McLaughlin

Re: pic: FRC488 2007 Robot

Looks Really nice

31-01-2007 14:22

Travis Hoffman

Re: pic: FRC488 2007 Robot

Looks sweet, Madison!

I was wondering, what would happen if only one robot could climb up onto your ramps (say, your other partner was broken/disabled during a match)? Do you have the stability to lift one robot while the other side is empty, or is that an impossibility?

31-01-2007 14:41

Lil' Lavery

Re: pic: FRC488 2007 Robot

I believe that the 4-bar support actually lowers from the bottom of their platforms, granting support underneath their platforms. So they shouldn't have any stability issues.

31-01-2007 15:15

Travis Hoffman

Re: pic: FRC488 2007 Robot

OK, I see the outline of the linkage under the ramps in the one view. Groovy.

01-02-2007 13:17

Madison

Re: pic: FRC488 2007 Robot

The four bar linkages lower to the floor and react against it while lifting other robots. Their rotation into place and lifting mechanisms are all operated independently. Our frame only need absord the horizontal force of the gas spring (I think) -- which amounts to about 50 lbs. on each side.

04-02-2007 01:56

silicon_ghoti

Re: pic: FRC488 2007 Robot

Oh! Question? Question?.. Does it come in anodized black and green?