pic: Team 1687 Doherty Technical Forces - Chassis

[Paul T.]

[cdm-description=photo]38463[/cdm-description]

Yes its under 112"

[AllenGregoryIV]

What was the intent of the two inset back wheels?

[ehfeinberg]

Maybe I can't see from the picture, but what caused you to put your back wheels on the inside of your robot?

And how do you believe the drive train will react with not all the wheels co-linear?

[Jay O'Donnell]

Looks fantastic! I can't wait to see your full robot this year, you guys always have great designs. Good luck!

[Paul T.]

I hate to be the person to ask but do you have 8" of bumpers on the two front outside vertices, it looks really small in the picture.

Also, what was the intent of the two inset back wheels?

the front two pieces are 8.5" and the back two tucked in wheels allows us to make our bumpers go like this

l l
\_/

it allows us to fit in the cylinder better.

[dodar]

Maybe I just cant visualize the bumpers but I dont see the point of having those back wheels inboard. That also looks like it will greatly affect the maneuverability of the robot.

[Paul T.]

Maybe I just cant visualize the bumpers but I dont see the point of having those back wheels inboard. That also looks like it will greatly affect the maneuverability of the robot.

Yeah we thought it may, but were pretty certain that it will be ok.
were also using 4 CIMS and an andymark to power it so we have the power to make up for it

[EricH]

Maybe I just cant visualize the bumpers but I dont see the point of having those back wheels inboard. That also looks like it will greatly affect the maneuverability of the robot.

You might ask 179 how having wheels offset in a similar pattern affected them a few years back. I think it was their 2005 robot that had 6 wheels in a diamond-ish pattern; it did fairly well.

It doesn't do much to affect maneuverability, not at that level, at least that I know about.

Visualizing the bumpers... It sounds like an interesting idea; I assume that bumper supports just aren't shown in this render. (Magic doesn't count as a support, sorry. Neither does simply constraining in CAD...)

[Paul T.]

You might ask 179 how having wheels offset in a similar pattern affected them a few years back. I think it was their 2005 robot that had 6 wheels in a diamond-ish pattern; it did fairly well.

It doesn't do much to affect maneuverability, not at that level, at least that I know about.

Visualizing the bumpers... It sounds like an interesting idea; I assume that bumper supports just aren't shown in this render. (Magic doesn't count as a support, sorry. Neither does simply constraining in CAD...)

you only see the chassis in the picture, we are planning to use the full 20 lbs for bumpers to include almost all mounting in the bumpers.

[Paul T.]

Looks fantastic! I can't wait to see your full robot this year, you guys always have great designs. Good luck!

If you liked the savage soccer robot you will love this, without giving too much away, we have an "awesome bar" type mechanism

we finally got some really great companies to support us so we can reach our full potential (assuming we can get some hex bearings)

[dodar]

You might ask 179 how having wheels offset in a similar pattern affected them a few years back. I think it was their 2005 robot that had 6 wheels in a diamond-ish pattern; it did fairly well.

It doesn't do much to affect maneuverability, not at that level, at least that I know about.

Visualizing the bumpers... It sounds like an interesting idea; I assume that bumper supports just aren't shown in this render. (Magic doesn't count as a support, sorry. Neither does simply constraining in CAD...)

I do believe 179 did it in 2008 as well. They had a pretty wicked turn rate. But it might have just been a 3-wheeler with the front wheel being a swerve module.

[Paul T.]

I do believe 179 did it in 2008 as well. They had a pretty wicked turn rate. But it might have just been a 3-wheeler with the front wheel being a swerve module.

http://www.chiefdelphi.com/media/photos/21631

that's actually what inspired it.

[dodar]

http://www.chiefdelphi.com/media/photos/21631

that's actually what inspired it.

Well that was their 2005 bot not 2008.

[Paul T.]

Well that was their 2005 bot not 2008.

yeah sorry about that, just thought team 179 didn't really think about the year.

[Nuttyman54]

Well that was their 2005 bot not 2008.

179 did this in 2005, 2007 (only the front pair) and 2008 (only the front pair).
234 also did it in 2007. All four robots were highly successful, I don't think the inset wheels will cause an issue for you.

[Joe G.]

To answer some questions:

-We have complete confidence in the turning and stability of this drivetrain. In addition to past success by team 179 and others with this style of drive, we've done the math -- it will turn with comparable scrub to a 38*28 6WD. The system is just structured somewhat differently than 179's, taking liberal inspiration from the West Coast Drive, the sheet metal work of teams 148, 228, 488 and others, and 2791's "belt in tube" system.

-Why bother? Some reasons we considered:

Tucks us further back in the 54" cylinder, giving us much needed room in the front for our multi function drop down system
(slightly) reduces perimeter for a given rectangular footprint, giving us a bit more space within the robot. The impact is slight, but it's enough to make all our desired functionality fit comfortably.
During strategy analysis, we foresaw frequent head-on collisions due to cross-field traffic, and situations where a defender may attempt to blockade access of some part of the field. The beveled edges allow our robot to glance off and pass by other robots more effectively (I believe this was also the intent behind 179's design)


-Here's a sketch showing our robot's bumper perimeter. The two front segments are each the minimum length. Framing which supports the bumpers on this odd-shaped perimeter not shown, much of the real load-bearing hardware does come off with the bumpers, but there is enough support on the robot to legally support the bumpers, and create a well-defined frame perimeter for inspection.

http://i.imgur.com/fxIv5Ut.png

[AllenGregoryIV]

you only see the chassis in the picture, we are planning to use the full 20 lbs for bumpers to include almost all mounting in the bumpers.

I'm still not sure if I understand this comment with how I understand R29.

The bumper hardware can be extensive but there still has to be a frame perimeter for which the bumpers are supported against. When you wrap the string around your robot with out the bumpers where does the frame perimeter support your bumpers?

[JesseK]

I agree with Allen. The bumpers (or any attached bumper hardware) do not define the frame perimeter -- only what's on the robot defines the frame perimeter.
FRAME PERIMETER: the polygon defined by the outer-most set of exterior vertices on the ROBOT (without the BUMPERS attached) that are within the BUMPER ZONE. To determine the FRAME PERIMETER, wrap a piece of string around the ROBOT at the level of the BUMPER ZONE - the string describes this polygon.

Since your wheels & axles define your perimeter, the plywood backing of the bumpers must butt up against them at every exterior vertex per R22.

Additionally, that is definitely a bit of stretch for the definition of "bumper mounting hardware" that I wouldn't stake my season on without a clearer definition from Q&A.

Fortunately, it looks like it's easy to accommodate hard mounts on the frame itself for bumpers & a frame perimeter everywhere except the front corners. Quite honestly, nothing defines what materials hard frame mount must be made out of, so it can technically be 1/32" sheet metal for the front corners.

The perimeter shape in a nice way of ensuring the 112" distance is met. Kudos to whomever thought of that idea on your team!

[Nuttyman54]

Fortunately, it looks like it's easy to accommodate hard mounts on the frame itself for bumpers & a frame perimeter everywhere except the front corners. Quite honestly, nothing defines what materials hard frame mount must be made out of, so it can technically be 1/32" sheet metal for the front corners.

I think this is what Joe is referring to. What's shown is only about 4" tall, they have quite a bit of room in the 6" of bumper zone above that to put a "frame perimeter". They'll be putting small/thin frame members in this area to meet the perimeter/frame rules, but the majority of the structure behind the bumpers is part of their mounting hardware.

[The_ShamWOW88]

Looks like a unique design. Can't wait to see it in action at WPI.

[Jeffrafa]

On a slightly different note, do I spot two pneumatic actuators on each gearbox?

And a pretty interesting layout of 4 larger actuators in the top view, I am very curious to see how this turns out.

Good luck!