pic: OH GOD! WHAT HAVE I DONE???

[AdamHeard]

Originally Posted by roboticWanderor

I DO THIS STUFF FOR FUN.
Really, I do. I ran into a snag trying to figure out the gear ratio it needed for the design, so I decided to post it up here looking for help. I do most of my calculations using the JVN calc to make it easier, then optimize the ratios for part availability, machining complexity etc.

And yes, I have many other designs posted up here, and yes I put in all of my materials as I CAD my parts, this one in particular is made of 6010 (correct?) alum, and steel axles, sprockets, gears etc. what you saw is what SolidWorks did it's mass calculations from.

Also, i realize this design is completely, and utterly complex. I would not really even consider building something like this. But CAD allows us to dream right?

I think you mean 6061 Aluminum . Most hollow extrusion is most commonly available in 6061 alloy.

Originally Posted by EricH

He does. He's actually one of the three most shown Solidworks designers on these forums. One of your teammates and another Northern California member are the other two. Search CD-Media by the uploader using these three members' names and you'll find plenty.

However flattering that may be, I don't deserve any credit for Solidworks. I know how to use it, but I'm much more adept in Inventor right now. If you want to see some really nice CAD in solidworks, check out Madison's stuff; she's quite skilled in that department.

-Craig

[Kevin Sevcik]

Originally Posted by FoleyEngineer

Hi Kevin,

Where do you get this figure from? I'm looking at the performance curve for the CIM and it looks like at 40A it's generating about .8Nm of torque which works out to .59 ft-lbs, or about 7 in-lbs - not 25 in-lbs as you suggest.

Maybe I'm mistaken. Wouldn't be the first time! Anybody?

Thanks!

You're correct, that was a typo on my part, or some such. I intended to use the 100 oz-in at 40A figure you can get from the CIM dimension sheet, which puts it at 6.25 in-lbs. I used that figure in the rest of the math, however, so the ratio still stands.

Originally Posted by Jonathan Norris

Looks like he is taking about stall torque, which is a bit less then 25 in-lbs. Yes we run 40A breakers, but the amperage will spike a lot higher then 40A before the breaker trips. From my rough understanding with 40A breakers on a CIM we can get all the torque out of the motors. The only time I can remember hearing the breakers trip is stalling our drive against a wall...

You can't get anywhere near stall torque out of the CIMs. The circuit breakers, Victor/Jaguar, and motor will all eventually prevent you from doing so. In the past, FIRST has arranged things so it's the circuit breaker that keeps you from using stall torque for any length of time, to protect your investment in your motors and speed controllers. Rest assured, that circuit breaker trips somewhat before your Victor would melt, and that your Victor would melt before your motor did. But the motor would most certainly do so if you stalled it for too long.

The 40A breakers we use will trip in at most 0.6 seconds at the 133A that stall torque would draw, so it's not really available for a useful amount of time, beyond stating up.

[Triple B]

pink uses alot of 6063 AL tubing also.
nice cad work wanderer.
mike d

[joshy1323]

Originally Posted by roboticWanderor

Also, i realize this design is completely, and utterly complex. I would not really even consider building something like this. But CAD allows us to dream right?

why wouldnt u want to try to build this? it does not look too complex at all. it looks more like a few simple parts that are organized to form a complex arm. im new to this site so sorry if im asking too many questions but i am confident that if i had all the materials needed the task of making that arm would be easily done in a week. does your team have all the tools needed to make those parts or is that y u say it is too complex?

[roboticWanderor]

Originally Posted by joshy1323

why wouldnt u want to try to build this? it does not look too complex at all. it looks more like a few simple parts that are organized to form a complex arm. im new to this site so sorry if im asking too many questions but i am confident that if i had all the materials needed the task of making that arm would be easily done in a week. does your team have all the tools needed to make those parts or is that y u say it is too complex?

Many of the crucial parts of this design rely an a lot of mill work, something my team has very little access to, and the tid-bit that we do is very limited capacity. Piece by piece, yes this arm is relatively simple, but when put together, you need some very important parts (such as a nice big gearbox) to make the rest of it work correctly. As with any design, the more complex it is, the more specific its function, but the higher likelihood that your not going to get it to work. There are teams with access to lots of tools, and build impressive machines, with lots of complex systems that work together perfectly. Then there are the teams with less resources, yet create amazingly functional robots from the resources at hand, sticking with simple "why didn't I think of that??" solutions to problems. Each can create wonderful robots, and be very successful in the games. My team has to try and be the latter, but I dream of the former.

Thanks for all your help guys, I'm currently switching to SolidWorks 2009 SDK so I will return from finals next week in full swing. This should be completed and attached to a robot before kickoff.