pic: WCD Chassis Idea



With all of the Chassis CAD’s that have been posted I realized it’s time I put a new one up.

6 wheel drive
Center Drop of 1/8"
2x1 tubing
Custom Wheels (Diameter - 4" )
Gearboxes are custom and still in the works.

No, the plate with the holes is not actually made of glass. But I figured you would like to see beneath it.

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.

6 FP is a bit of stretch…isn’ it?

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.

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.

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. :slight_smile:

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.

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.

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?)

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.

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

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

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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.

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!

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.

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.

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.

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

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. :slight_smile:

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

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.

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.