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Unread 01-13-2008, 12:44 PM
cjtenny cjtenny is offline
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2349's drive

We'll have the back 8"s (traction, roughtop) driven by 2 CIMs each through an AM toughbox, the front not driven. Chances are, our hurdling device will be mounted on the "back", making it the front. Battery will go on omni side, then, to reduce chance of tipping.

We've built the kitbot chassis part, and are ordering the wheels / extra CIMs / etc.

This took probably 3x as long to model as it will have to build. It was my first time using CAD.

Thanks, SolidWorks!

Edit / Note: These all may be upside down, as we may flip this over for a lower COG / wheelbase... depends on how easy it is to mount the Toughboxes that way, though.

Image one, rendered with PhotoWorks: What we've built so far


Image two, screencapped from SolidWorks because it's "View-->Screen Capture" has bugs in Vista Ultimate (too bad it didn't run nicely in linux):
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Unread 01-13-2008, 08:11 PM
Lawry Goldstein Lawry Goldstein is offline
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Re: 2349's drive

First of all, WOW! That is a great job of first time modeling. You already have a great start, so keep practicing.
----------------------------------
As for the more helpful part of my post, I just wanted to give you a quick heads-up to make sure you understand the electrical limitations.

Here is the basic problem:
Each CIM has to be run off a Victor; each Victor is generally run off the 40 amp breaker. The main robot breaker is only rated for 120 amps continuous current.

*Quick Math*

That means if you’re driving at full power your running at 160 amps which is more than your robot can run consistently, so while it will work be careful because if you have a compressor running (20 amps) and possibly some motors for a feature (20-30 amps each) you could very quickly overrun both your breakers and your battery.

Understand that this doesn't mean you can't do it, for example if you have seen 'crab' drives, they run 4 CIMs as well as 1-2 motors for rotating those CIMs plus features. I mention this so that you understand you can run these motors over the 120 amp breaker since it is a CONTINOUS breaker, but you cannot run everything for 2 minutes. Try and finish building your drivetrain with time to drive the robot around and see what happens over 2 minutes, put in a new battery and drive it for another 2 minutes. This is unfortunately what happens sometimes during competitions, so you may need to have a few bottles of 'compressed air' so that you can cool the breakers during heavy back-to-back matches.
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Unread 01-13-2008, 08:56 PM
cjtenny cjtenny is offline
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Re: 2349's drive

Thanks!

We've done some stuff with the victors before -- I, with Shane (team 97 mentor; don't know his CD forum name), coded / did the electronics for http://web.mit.edu/first/segway/ (Although I didn't do the modeling, this was my first CAD that wasn't lego and my second, including lego) -- so I'm fairly sure the CIMS will be able to push it all. Hopefully, anyway.

We had some almost-falls off the segway when we'd been running it and tripped the breakers. AKA, offroad tests at my hs. (We brought it out to demo, from MIT)
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Unread 01-14-2008, 09:17 AM
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Re: 2349's drive

2 CIMs each through the AM gearbox will definitely be able to push it all, you don't need to worry about that.
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Unread 01-14-2008, 09:49 AM
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Re: 2349's drive

just out of curiosity, why do you want your bot sideways? wouldnt that make it more difficult to get around other bots? well, i suppose it makes it harder for other bots to get around you as well...

very good job with the modeling!
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Unread 01-14-2008, 10:29 AM
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Re: 2349's drive

Thanks, modeling update coming soon.

It's all because of our hurdling design... I guess I'll just have to say, "you'll see"!
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Unread 01-14-2008, 11:30 AM
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Re: 2349's drive

Quote:
Originally Posted by cjtenny View Post
Thanks, modeling update coming soon.

It's all because of our hurdling design... I guess I'll just have to say, "you'll see"!
Looks good, but i am scared of you guys tipping easily, have you thought about that?
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Unread 01-14-2008, 11:34 AM
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Re: 2349's drive

We were worried about tipping as well, as we initially thought of a lifting device closer to the front of the robot.

Then we fully inflated the ball and realized that wouldn't work very well.

Cam: did we decide on the traction wheels being in the front or in the back? I remember you saying in front not too long ago, because that way we can drive in the event that we tilt up just a little bit.
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Unread 01-14-2008, 11:49 AM
cjtenny cjtenny is offline
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Re: 2349's drive

The traction wheels are the front -- the battery & electronics will go on the back to balance out the weight of lifting the ball. That way, we can always maintain driving wheel contact, yeah.
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