20-05-2010 09:26

ADZDEBLICK

Re: pic: WCD Chassis Idea

I like the cross braces, but the frame will have a tendency to twist without some more support.
Consider where chains/belts will run.
Also as someone suggested a while back, if you model your gearbox with all cims, you won't run into any space issues when you put in the fp/planet.

20-05-2010 09:27

ttldomination

Re: pic: WCD Chassis Idea

6 FP is a bit of stretch...isn' it?

20-05-2010 09:41

JesseK

Re: pic: WCD Chassis Idea

Not necessarily; if it's their offseason prototype then perhaps they have many FP's lying around. They're easily swapped with CIMs if AM FP Planetaries are used.

I would consider trying to simplify the gearbox to two reduction stages instead of three. This may or may not interfere with an encoder mount on the output shaft, but the tradeoff is that it would lower all of the motors (and thus the c.g.) by an inch or two. I like the frame thus far though; adding a super structure for manipulators or cross bars at either end would solidify it enough I think. Given the previous years' bumper rules, those cross bars may also aid in compliance.

20-05-2010 10:27

Peter Matteson

Re: pic: WCD Chassis Idea

If those cross braces are welded it will be a nightmare to keep your frame true and parallel without very good solid fixturing and welding.

The X-brace also lends itself to allowing you to get bent out of shape and not box when, not if, you get hit from both sides at the same time or sandwiched against a wall. It's a novel idea but I would at least put smaller crossmembers all the way across to make it practical for how rough the games are.

20-05-2010 11:08

Rion Atkinson

Re: pic: WCD Chassis Idea

I'll probably be taking the entire cross brace area actually. It's simply not need. And cutting holes in the metal for the chains would be a pain. It's easier to use the electronics board (The thing made out of glass right now) as the main structure.

With modeling with CIM vs. FP. It actually doesn't matter. I had those things with one CIM in it. Turns out the FP is only like a 1/4 inch shorter. So it doesn't really matter.

I was actually going to be changing it to a two speed gear reduction today.

As for the cross bars, I do believe you are right. I'll probably have some sheet metal fun and make the belly pan those cross bars as well.

Why would those braces be and harder to weld than anything else? (I'm not a welder so this is a legitimate question.)

I have a feeling that the biggest problems with bending would be on the outside edges rather than in the middle. Which as you said is easily fixed with more cross braces. Or as I said earlier. I belly pan.

20-05-2010 11:19

Andrew Schreiber

Re: pic: WCD Chassis Idea

The volume of space taken up by a FP is significantly smaller than that of a CIM. This year at West Michigan we replaced a FP with a CIM and had to move around our compressor because two objects seem to have an aversion to occupying the same point in space. Long story short, model with the largest thing you might ever put in there and then be pleasantly surprised when you have extra space.

20-05-2010 11:54

TJ Cawley

Re: pic: WCD Chassis Idea

usually how many CIM or FP motors are allowed during the FIRST competitions? I heard during the build for Breakaway that we could only use 5 CIM motors. So there would be a shortage of one motor for that system. plus, that uses up all of your allowed CIM motors. so there would be a bit of a sacrifice using those transmissions if your team needed a strong motor for another mechanism.

20-05-2010 13:00

Rion Atkinson

Re: pic: WCD Chassis Idea

Typically you are only allowed 4 CIMs. A lot of teams use all 4 in the drive train. The plan for this gearbox would be to use 2CIMs and 1fp for each one.

Can anyone tell me the typical limit on Fisher Price motors? (Or is there not one?)

20-05-2010 13:09

Peter Matteson

Re: pic: WCD Chassis Idea

The reason welding would be difficult is you have to make sure you angles are perfect and lengths are identical. If you have any gaps the material will suck into the mating part during the weld and distort the frame. This is why you have to properly clamp and fixture everything.

If you clamp everything tightly,fixturing your angles correctly you can use welding rod to fill the gaps, that will probably be between the parts, and keep everything true. It is just not as easy and straightforward as most teams seem to go for. It is possible just not easy and you have to spend the time fixturing and planning before you weld so that the finished product comes out correct.

20-05-2010 13:48

ADZDEBLICK

Re: pic: WCD Chassis Idea

this year and in years past we have been limited to 2 FP motors.

20-05-2010 14:45

Akash Rastogi

Re: pic: WCD Chassis Idea

Instead of adding more crossmembers, you would be better off using the plans of a traditional WCD and add on a belly pan. Another version which I personally love is 418's, designed by roboticwanderer (Lewis). The combination of 2x1 and 1x1 allows for clean chain runs too.

http://www.chiefdelphi.com/media/photos/31575

.

20-05-2010 14:57

EricH

Re: pic: WCD Chassis Idea

2 FP's (or however many are in the KOP--typically 2, since at least 2004), 2 CIMs from the KOP, up to X (typically 2, but 3 in 2010) extra CIMs allowed.

To do this, you'd need 4 CIMs and 2 FPs, leaving 1 CIM, the window motors, the RS-55Xs, and pneumatics to do anything else you wanted to do.

20-05-2010 18:34

Jamie Kalb

Re: pic: WCD Chassis Idea

Looks awesome, Rion! Thanks for sharing with us.

I know you said the gearbox is still in development, but is it going to be a two-speed? I'm excited to see the final version!

Keep up the great work!

20-05-2010 19:39

Rion Atkinson

Re: pic: WCD Chassis Idea

Thank you very much.

Yeah. I got to thinking about this after I posted it. RC gave me a few tips as well. The next version will have a belly pan.
It will indeed be a two speed gearbox. I'm taking the second stage out today, but yeah, two speed.

20-05-2010 19:53

Chris is me

Re: pic: WCD Chassis Idea

I always try and model stuff with CIMs anywhere I want to put FP+AMs. That way no matter what iterations you do involving switching motor position you know the biggest possible motor will fit everywhere.

20-05-2010 21:17

ttldomination

Re: pic: WCD Chassis Idea

I just meant it was a bit of stretch simply because we've been allowed to use roughly 2 FPs, but if this an off-season project, then do what you wish.

20-05-2010 21:25

Mike Schreiber

Re: pic: WCD Chassis Idea

It is good engineering practice to know your resource limitations before you start to design something. RTFM please.

20-05-2010 23:10

Rion Atkinson

Re: pic: WCD Chassis Idea

You have a very good point. I'll be sure to take that into account.

It's not really a project. More of a "I'm bored and need something do, oh look solidworks is open" type thing.

Ahahahaha! I would love to point out your new favorite smiley ->

Also, if you would love to quiz me on this years game. Go for it, and be shocked. I am the only one that read the manual this year, so I know this stuff. I just have a tendency to forget this after 3 months.

Know some background info before making assumptions.

20-05-2010 23:26

Mike Schreiber

Re: pic: WCD Chassis Idea

I'm going to start with

How many FP motors were allowed?

"We know what we have, and what we can do. Lets start with that."

Brushing up on the rules generally helps the design along.

20-05-2010 23:49

Rion Atkinson

Re: pic: WCD Chassis Idea

Okay you have a good point. But the way you came a cross seemed high and mighty; which I tend to have issues with. I agree. I could have gone looking. But sense we were on the topic, it was quicker just to ask the question sense i have other things to be doing as well. And seeing as I don't even have a team right now, or the means to make this. I don't expect the design to even come to life, so I wasn't exactly worried about the rules of how many.

21-05-2010 13:57

Chris is me

Re: pic: WCD Chassis Idea

The rules that haven't been released yet?

21-05-2010 14:17

Andrew Schreiber

Re: pic: WCD Chassis Idea

Or make them up. Adding constraints to your designs will cause you to think of interesting solutions. Say for example you don't want to use wheels to move, cad a solution to that. Or the ever popular Jello game, figure out how to move on Jello. Yeah letting your imagination go wild is great but without constraints your work is worthless as both a practical design and as an effective mental exercise.

Some suggested constraints:

Sub 30lb drive train (INCLUDING electronics)

Modular drive train

Drive train that can accept multiple types of wheels and still remain functional (Think mecanum or 6" plactions)

Get away from the all aluminum designs.

Robot that can traverse a 6" step (using 4" wheels).

Robots that could move up a wall.

Basically let's try to get away from the design mantra of Copy 254 that I keep seeing. "Oh, I know, let's all make pretty renders of basically the same darn thing" Show some creativity, show some uniqueness. You know the nonadrive was designed by a student over the summer right? That is new and I would LOVE to see something like that. Even if it has no practical use right now.