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compwiztobe
09-23-2010, 11:51 AM
https://netfiles.umn.edu/users/siekm008/Shared/demobot/demobotsmall.PNG

We've been kicking this around for a bit as an off season project idea. The basic concept is that it would be an exercise in multiple disciplines. It will employ the following:

Holonomic Drive (4 perpendicular omni wheels) - to explore the capabilities, limitations, and what is otherwise involved in omni directional drive systems
CAN - to play around with what this can for us in future years
Sheet Metal - to see just how able we are to do this and hopefully learn some useful techniques applicable for sheet metal and other design

It will also be somewhat of a software exercise, playing around with how to best control omnidirectional drive, as well as getting the CAN to work as desired. We intend to use the 2can, since we've heard it has a faster bus than Black Jaguars, and we don't need a cRio on the robot. When completed, we would hope to use it for demos, protoypes, driving practice, etc. since none of the parts would be in demand during (cRio) and we could hopefully easily attach things to the top.

So, I'm just wondering what sort of comments anyone would have.

Specifically, I'm wondering about the design:

I'm extremely new to sheet metal, and certainly don't have any background in analysis of static stress or whatever. Is this design sound? (and, where can I find helpful sheet metal fabrication resources?)
I've been wondering about the way the wheels are mounted. Is it ok to put a quarter of the bot's weight directly on the output shaft of the gearbox? Should I consider supporting the shaft or using a chain or belt?
Anything else you may notice or wonder...


The gearboxes are toughbox nanos (am-0518) at 12.75:1. Here is a screenshot of just the bellypan.
https://netfiles.umn.edu/users/siekm008/Shared/demobot/bellypan.PNG

You can download a .zip of the Solidworks collection at https://netfiles.umn.edu/users/siekm008/Shared/demobot/Demo Bot.zip.

mplanchard
09-23-2010, 06:54 PM
Hi Aren

I don't have access to download your beautiful model tonight but I can still comment based on the images. I assume you received your 2010-2011 robot sponsorship package. 2010 has many new enhancements to sheet metal so I would go through the sheet metal tutorial and weldment tutorial

I think your outside holes are too close to the edges. Rule on thumb 3times the hole radius to the edge.

Also don't change your hole diameter unless you really have to.

Find out from your nearest friendly sheet metal shop what standard tools do they keep at the ready. That way you are not asking for custom tools or ones they have to search for

If you can make this model I know you can do a simple stress analyst on the part. You know the weight of the tough box on other sub assembly. Go to the Evaluate tab and select on SimulationXpress. Select the cylindrical face of the holes along the outside to be fixed. Select the top face to apply the force. This Will be a rough approximation. But it will show you areas of high stress.

Also in the Evaluate tab use SustainabilityXpress to set a baseline with your current material and then select Find Similar to search for materials of similar tensile strength. There may be another material that costs less and is better for the environment too. Marie