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.

[ehfeinberg]

Originally Posted by 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.

Honestly, I don't feel it really matters what the dimensions are for your offseason drive. However, I would make them so they fit all of the previous years rules to give you practice designing a drive that not only works and looks cool, but also follows all of the perimeter (and maybe even bumper rules if you think that far ahead).

Offseason drives are also great bases for offseason manipulators. Think of what you might put on top of it. Yes, this is hard thinking about future years offseason projects, but next offseason you might decide to prototype a elevator or whatnot. Building a complete robot over the course of many seasons is a extremely rewarding task.

You might also want to use the same dimensions you used for your 2014 robot, because you could possibly (if time permits) take the manipulators of your 2014 robot, and place it on top of your fancy new drive base.

So in short, plan the dimensions of your drive base with what you might possibly build or place on top of it.

[orangemoore]

Originally Posted by 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.

I hope you mean 6 cims in total and not just 3.

[Billfred]

Just a notion: Traditional West Coast Drive is just (relatively cheap) 1x2 tubing, creatively machined and assembled. Do you have the resources to machine the tubing, then transplant the gearboxes/wheels/axles to try it both ways?

[asid61]

Make sure you have somebody who can do the machining. Also, make sure your chain tensioning is good. We had a lot of problems because we did not use screw tensioning or cam tensioning. We did a thing with slots, pulling, and locknuts. Bad plan.

[ehfeinberg]

Originally Posted by asid61

Make sure you have somebody who can do the machining. Also, make sure your chain tensioning is good. We had a lot of problems because we did not use screw tensioning or cam tensioning. We did a thing with slots, pulling, and locknuts. Bad plan.

Have you seen these?

We used them this past year, and were nothing but happy with their performance. Not only do they provide easy tensioning by just sliding the blocks in and out, but they only require a drill press for machining.

[lamk]

Originally Posted by orangemoore

I hope you mean 6 cims in total and not just 3.

Yes 6 cim total 3 cim per gear box

[lamk]

Originally Posted by ehfeinberg

Have you seen these?

We used them this past year, and were nothing but happy with their performance. Not only do they provide easy tensioning by just sliding the blocks in and out, but they only require a drill press for machining.

That's exactly what I am planning to use!!

[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?

[ErvinI]

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.

Team 254 was 27.75"x28". Technically wide, although it was pretty much square.

Is there a specific reason why you believe that WCD's are run in a long configuration? Is it just what you've seen, or is there an underlying design advantage for a WCD that is best seen in a long configuration?

[cadandcookies]

Square chassis have a major advantage with the advent of the "perimeter" rule, as they maximize volume. With a WCD/generic 6wd they also let you avoid a drop center (if you space things correctly).

That being said, go with whatever the students are motivated to do. Don't lose valuable time and energy debating the chassis dimensions when the point is giving the team practice.

Speaking of the point, when your team is making the decision, make sure to take into account the intended purposes-- to practice machining? To prove that you can do it? To have an excuse to hang out in the shop over the summer? The core purpose of this project should guide it from beginning to end.

[Madison]

Originally Posted by cadandcookies

Square chassis have a major advantage with the advent of the "perimeter" rule, as they maximize volume.

For a given perimeter, a circle's your best bet. A square is a pretty inefficient shape, actually.

[Torrance]

Originally Posted by ErvinI

Team 254 was 27.75"x28". Technically wide, although it was pretty much square.

Is there a specific reason why you believe that WCD's are run in a long configuration? Is it just what you've seen, or is there an underlying design advantage for a WCD that is best seen in a long configuration?

At least for the past 3 years I've been on the team, usually the primary driving (pun not intended) force behind the shape of the Drivebase frame is due to what we predict the superstructure will require. In 2012 we needed a long bot to fit a large hopper in the back, in 2013 having it be square made us more compact and thus easier to climb and drive under/through the pyramid. In 2014 we had to be a little wider to fit the ball inbetween the superstructure tubes on the sides.
So I guess my point is this: While your driver may prefer a specific shape of chassis, at some point you'll have to differ from previous years to fulfill design requirement and rule changes so I recommend prototyping lots of shapes of frames and getting your drivers used to all of them over time!

While I am not a driver, I have heard that our drivers prefer driving square 6WCD over long 8WCD because it easier to get out of T-bones.