Need help in deciding the configuration for an off season chassis prototype

[lamk]

We used the long configuration AM14u for aerial assist. It got us to St. Louis. As an off season activity I would like to prototype a 3 cim 2 speed 6 wheel west coast drive. I am leaning towards a 28 x 28 square configuration. My student wants to stick with the 23x32 long configuration. Any suggestions.

[EricH]

How possible is doing both?

Generally speaking, WCDs are run long configuration. Sometimes someone will try a wide configuration. Not too many try a square.

It's the offseason. If you can't decide based on some other parameters, play a couple games of rock-paper-scissors-lizard-Spock to pick one, and put the other one on the list for next offseason.

[lamk]

Originally Posted by EricH

How possible is doing both?

Generally speaking, WCDs are run long configuration. Sometimes someone will try a wide configuration. Not too many try a square.

It's the offseason. If you can't decide based on some other parameters, play a couple games of rock-paper-scissors-lizard-Spock to pick one, and put the other one on the list for next offseason.

There is a few reason why I am leaning towards a square 6 wheel WCD. Our driver has experience driving a long configuration for a whole season so I want them to drive something different to see how this configuration handle. I don't know it it matters: all the Einstein drivetrain this year were square drive including the poofs.
Once we have some experience building this chassis I don't think it'll be difficult for us to build a long configuration.
I'll be using the vex versachassis and 3 cim two speed ball shifter gear box.

I do like the suggestion of building a chassis that has the same dimension as our competition bot and put this year superstructure on it.

[ehfeinberg]

Originally Posted by lamk

I don't know it it matters: all the Einstein drivetrain this year were square drive including the poofs.

I feel that has less to do with a square drive being "better" then a long drive and more of due to perimeter constraints, it was hard to acquire a ball being long. Thus many teams were forced to be much more square.

That said, there are a few things that I forgot to mention in my first post, that being long allows you to be taller without having to worry about tipping over as much as being square (or wide and having a shorter wheel base). But being square (or wide and having a shorter wheel base) usually enables you to turn easier with less scrubbing of the wheels.

I am not sure how much different it is to drive a square vs. long robot, but I doubt it would be significantly different. Maybe someone can chime in about that?

[Brandon_L]

Originally Posted by EricH

Generally speaking, WCDs are run long configuration. Sometimes someone will try a wide configuration. Not too many try a square.

WCD generally has nothing to do with wide, long, square, or even the amount of wheels or type of wheels. It comes in all shapes and sizes, just like any other drive style. This style seems to be defined by the cantilevered wheels, which makes it easy to service.

Originally Posted by lamk

There is a few reason why I am leaning towards a square 6 wheel WCD. Our driver has experience driving a long configuration for a whole season so I want them to drive something different to see how this configuration handle.

Our drivetrain (WCD) this season would of been square, if not for the balls being so wide. Our base ended up being 28x27, wide. (We need just that extra inch for our intake to work ) With a six wheel drop center, the thing handled like a dream.

For an example of a square 4 wheel WCD, see 2590's 2013 robot Athena

Its all about the effective wheelbase compared to the track. When building a skid style drivetrain where unlike cars or bikes the front wheels wont pivot to turn, too small of a wheelbase will result in uncontrollable turning (turning to well). Too big of a wheelbase, and you'll have trouble turning. Its simply a ratio.

[Tim Lehmann4967]

4967 Decided to cut the KitBot chassis into a 27.5inx27.5in square. This gave us a lot of frame rigidity. I can post pictures if interested.

[lamk]

Originally Posted by Tim Lehmann4967

4967 Decided to cut the KitBot chassis into a 27.5inx27.5in square. This gave us a lot of frame rigidity. I can post pictures if interested.

Please do!! My original plan was to exactly do that for the off season chassis but decided to try WCD because I feel WCD is likely more easier to configure and maintain.

[Bryan1625]

Team 1625 was a 27x28 bot (wide). I absolutely loved the drive this year too. It ran very smooth with a quick turn radius

[Brandon_L]

Originally Posted by Bryan1625

Team 1625 was a 27x28 bot (wide). I absolutely loved the drive this year too. It ran very smooth with a quick turn radius

4wd? 6wd? 8?

Frame dimensions generally don't decide how smooth your bot turns or doesn't turn, it's all about the wheelbase/track width. A 4 wheel drive of X by Y size will have more trouble turning then a base of the same size with a six wheel drop center.

[Oblarg]

We ran the kitbot wheel setup in a 29x26.5 configuration this year, and it turned like a champ. Probably worth noting that it was also very well-balanced; CM was maybe an inch or two forward of the geometric center of the robot.

[Bryan1625]

Originally Posted by Brandon_L

4wd? 6wd? 8?

Frame dimensions generally don't decide how smooth your bot turns or doesn't turn, it's all about the wheelbase/track width. A 4 wheel drive of X by Y size will have more trouble turning then a base of the same size with a six wheel drop center.

Its a 4 Wheel drive with 6 CIMs

[Abhishek R]

Originally Posted by Bryan1625

Its a 4 Wheel drive with 6 CIMs

Though I don't think it applies to this thread as much because your turning radius will be largely improved by having 2 omnis and 2 traction wheels.

[pmangels17]

Just a reminder, off the subject of dimensions, make sure you test the base under full weight. If your team generally build way under the weight limit and is 30lbs underweight, make sure you account for that. If your team pushes the limit to 119.9 lbs like we usually do, then your base when being tested should be around 140 lbs total (robot, battery, bumper). If you don;t test with weight you will see dramatically different traction results

If you want to get fancy you should even raise the weight a bit to account for how high your Center of Mass will be. Accurate testing in the offseason yields predictable results in the onseason.

[Brandon_L]

Originally Posted by Abhishek R

Though I don't think it applies to this thread as much because your turning radius will be largely improved by having 2 omnis and 2 traction wheels.

While that is true, there is also the major downside of being spun around in every collision that teams usually try to avoid.

[Tim Lehmann4967]

Originally Posted by lamk

Please do!! My original plan was to exactly do that for the off season chassis but decided to try WCD because I feel WCD is likely more easier to configure and maintain.

I'm having some issues uploading the photographs from my phone due to the weird format it saves them in. I will have them converted/uploaded later this evening. Sorry about the wait.