pic: GUS Team 228's 6WD Sheet Metal Prototype Chassis

[artdutra04]

[cdm-description=photo]32179[/cdm-description]

[gorrilla]

why did you design it with all double wheels?

[Elgin Clock]

That may be just the parting line from the mold of the wheel shown.
Yeah, some people like to get fancy with their CAD representation of things, & knowing Art, if he helped in this project, it may be just that.

But then again...

Edit: Yeah, looks like just the mold of the Colson wheels going by the description now.

[artdutra04]

why did you design it with all double wheels?Those aren't double wheels, it's just the raised center of the Colson Performa (http://www.robotmarketplace.com/products/BPDWC16.html) wheels.

[daltore]

They actually offer the Colson wheels in SolidWorks premade at 3D Content Central, it's just how accurate they already come. Nice desing, looks like it'll hold up very nicely to anything, and I really like how the gearboxes and the frame are essentially one part, less to go wrong.

[Tanwad11]

Nice choice going with the colsons. We've had great success with them. Let us know how it turns out if u decide to use it.

[gorrilla]

Those aren't double wheels, it's just the raised center of the Colson Performa (http://www.robotmarketplace.com/products/BPDWC16.html) wheels.

do you know why they have a raised center?

[Madison]

do you know why they have a raised center?

They're probably made in a split mold and require draft away from the seam line to get the mold off.

[gorrilla]

They're probably made in a split mold and require draft away from the seam line to get the mold off.


oh yeah, never thought about that

[EricVicenti]

Very nice, its almost like a perfect kit bot. We also used that ratio in our practice drivebase this year, and its fantastic. 12 fps and some real pushing power.

[artdutra04]

Always listen to your gut instinct. ;-)

Something inside of me was screaming that 41.5 pounds was way too high, that something was wrong.

And after looking through all the models again, the error was found; I never manually entered in the weight of the downloaded Colson wheel model, so it used whatever the default density was. This estimated weight ended up being about 1.58 pounds per wheel! :eek:

Properly entering in the weight droped the total weight down to 39.30 pounds.

And since I was already on this train of thought, I went back to the specs on the Colson wheels and found that by dropping from 2" width wheels* to the 1.5" width Performa wheels, an additional 1.932 pounds could be lost, bringing the total weight to 37.37 pounds. On top of this, a slight modification to the aluminum inserts pressed into the Colson wheels loses another 0.3 pounds, which brings the weight down to 37.07 lbs. (Which is right in the 36-38 pound range I was expecting).


* The original reason for using the 2" Colson wheels was because we already had a set on our 2008 competition and practice robots; of these the practice robot set would make the migration onto our 2009 practice robot.

[CraigHickman]

I'm not seeing any tensioning system. Am I missing something?

[artdutra04]

I'm not seeing any tensioning system. Am I missing something?No, there isn't any modeled yet.

The final one will probably be either a set of Delrin floating chain tensioners, or an eccentric Delrin disc (http://www.team228.org/media/pictures/view/3009). But I didn't feel like modeling actual roller chain, so I used a simple loop with the weight set to what equivalent roller chain would weigh.

Either way it's a simple lightweight part with simple operation, and that's all I'm concerned about.

[CraigHickman]

Either way it's a simple lightweight part with simple operation, and that's all I'm concerned about.

Yeah, makes sense. I really like the look of this design, and I wish you much luck in building this or something similar. I really wish my team had sheet metal sponsors, then I'd be able to do something similar.

Do you think the gearbox will be stiff enough?

[artdutra04]

Do you think the gearbox will be stiff enough?There shouldn't be any problems.

Every time another flange or bend is added to the part, the cold rolling operation strain hardens the material. Both of sides (which would replace standoffs) have a flange on the top, and the face where the CIM motors are mounted has a flange along the bottom. I'd love to do some advanced FEA on the part, but I'm still learning Cosmos. :)

So until then, I mostly rely on past experience. Like this bracket I modeled for our 2007 robot, which would have been near impossible to make out of anything except sheet metal.

http://www.team228.org/gallery/61/slideshow/weeksix-001.jpg (http://www.team228.org/media/pictures/view/2816)

And mounted on the robot:

http://www.team228.org/gallery/61/slideshow/weeksix-087.jpg (http://www.team228.org/media/pictures/view/2902)

http://www.team228.org/gallery/61/slideshow/weeksix-096.jpg (http://www.team228.org/media/pictures/view/2911)

... which took all kinds of abuse (http://www.youtube.com/watch?v=KR6daSCFjSM) the entire season and never had any structural problems.