30-01-2013 21:47

AllenGregoryIV

Re: pic: Team 1687 Doherty Technical Forces - Chassis

What was the intent of the two inset back wheels?

30-01-2013 21:47

ehfeinberg

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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?

30-01-2013 21:48

Jay O'Donnell

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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

30-01-2013 21:52

Paul T.

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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.

30-01-2013 21:54

dodar

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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.

30-01-2013 21:57

Paul T.

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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

30-01-2013 21:58

EricH

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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...)

30-01-2013 22:00

Paul T.

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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.

30-01-2013 22:04

Paul T.

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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)

30-01-2013 22:04

dodar

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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.

30-01-2013 22:10

Paul T.

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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

that's actually what inspired it.

30-01-2013 22:21

dodar

Re: pic: Team 1687 Doherty Technical Forces - Chassis

Well that was their 2005 bot not 2008.

30-01-2013 22:26

Paul T.

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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

30-01-2013 22:36

Nuttyman54

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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.

30-01-2013 23:20

Joe G.

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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.

30-01-2013 23:20

AllenGregoryIV

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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?

31-01-2013 09:47

JesseK

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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.

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!

31-01-2013 12:15

Nuttyman54

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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.

31-01-2013 13:13

The_ShamWOW88

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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

31-01-2013 13:40

Jeffrafa

Re: pic: Team 1687 Doherty Technical Forces - Chassis

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!