Re: pic: Uber 3.0
 

Really great design, looks solid, well put together mechanically and probably will translate well to almost any potential competition from that perspective.

The speed issue will really be determined when the game happens and should be a factor of where the game pieces are set up and the driving lines that will happen (consider 2010's layout vs 2011). It just so happened this past years game called for really high speeds but others (2010) called for slower speeds/higher acceleration.

The inspectors, FTA's, programmers and anybody else on the field would really love it if you repositioned some of the core electronics like the Main Switch, cRio and Router (yeap include that too) into one highly visible and easy to access location. You also might want to get some input from some Electrical guys on how to set up the "non-core" electronics better from a wiring perspective to maximize accessibility when stuff doesn't go as planned.

Those who pay attention to that type of detail on all perspectives don't go unnoticed and it makes everyone else's life easier.

(Like consider the possibility of having somebody else's arm crash into the hardest to get to Victor while severing the wire and you need to replace all of it in 2 minutes because your alliance partner already burned your only time out on Einstein, thats the type of detail I'm talking about)

But don't get me wrong, you are seriously on the right track right now.

Re: pic: Uber 3.0
 

Nice design!

I have to agree with Mr Lim that my favourite feature is the 1" ground clearance. Last year I think you were driving a hovercraft ;)
I wouldn't worry about all of the comments about your choice of speed. It may well be that 16 ft/s is too fast for a single speed, but the way you have set up the gearbox makes it very easy to change the ratio. Just swap out the sprockets in the gearbox, shorten the chain, and away you go. Actually, this is a very good reason not to design with the gearbox directly driving the middle wheel.

Unless we get ourselves a sheet metal sponsor, feel free not to share the CAD with our guys. As pretty as your design is, 610 can't build that way.

Re: pic: Uber 3.0
 

YES 16fps is WAY to fast, im sure you already know that by now, but i will show you how to fix it by just getting 1 part. The AM 12t double sided sprocket http://www.andymark.com/product-p/am-0736.htm. This will bring your gearing total down to ~8:1, as a driver i would enjoy a 8:1 reduction.

Hope this helped.

Re: pic: Uber 3.0
 

What do you mean by 8:1? A reduction means nothing without wheel size and a reference point.

Re: pic: Uber 3.0
 

Here's my logic on the gearing:

If you gear for high speed, and can play the game very well:
- Defenders will come block you
- If you only have 16ft/s as an option, the defenders will succeed in blocking you most of the time
- If you can push through the defense via a low gear, you will be a power house.

If you gear for high speed, and can play the game decently enough for a 2nd pick:
- Defenders may not block you
- You can do cross-field 'under the radar' things, such as carrying a specific shape for an alliance this year. Game dependent though (wouldn't work in 09/10)

Thus, IMO, single-speed gearing for high speed is a risk and a tradeoff. The decision is inconclusive until the game is announced, yet the great thing about single speed gearboxes is that they're easily adjustable.

Re: pic: Uber 3.0
 

If you are going to spend the money for a sheet frame, go for 2 speeds. 16 is too fast to be the only gear, but assuming the game next year involves complicated and minute maneuvering, an 8/16 or nearby ratio could be a good gearbox

Re: pic: Uber 3.0
 

You would be surprised how few teams actually have high traction drives that can play effective and smart defense. Teams like 233 and 1503 had single speed drivetrains and I don't think anyone would argue that they were "successfully blocked most of the time".

Re: pic: Uber 3.0
 

Kaj,

Here are some links to similar 6wd drivetrains:

http://www.chiefdelphi.com/forums/sh...ad.php?t=68613
http://www.chiefdelphi.com/forums/sh...ad.php?t=68825
http://www.chiefdelphi.com/forums/sh...ad.php?t=68847
http://www.chiefdelphi.com/forums/sh...ad.php?t=77678
http://www.chiefdelphi.com/forums/sh...ad.php?t=78065
http://www.chiefdelphi.com/forums/sh...ad.php?t=78101
http://www.chiefdelphi.com/forums/sh...ad.php?t=86155
http://www.chiefdelphi.com/forums/sh...ad.php?t=86732

The guy seems to know what he's doing, except for the fact that he seems to having something against ground clearance. There's some epic story about how his 2009 Curie division finalist drivetrain got high-centered on a flat field...and how he fixed it by building a drivetrain with even less ground clearance in 2011. Then again, in 2011 he made the Galileo finals at Champs.

I think the key is less ground clearance = more success.

There is no doubt in my mind, that if you can finally figure out a way to have negative ground clearance, a trip to Einstein is in the books.

P.S. Honestly Kaj, you're now more in a position to give advice on these matters as opposed to receive it. I don't know too many students OR mentors who have actually designed, sourced, machined, assembled, and driven IN COMPETITION as many quality drivetrains as you. Ian Mackenzie, Tristan Lall or Hinkel Yeung can't even boast resumes as extensive - certainly not as students.

P.P.S. Ground Clearance

Re: pic: Uber 3.0
 

Yes we did all of this analysis as part of our standard approach to drive design. The original intention was to come in significantly underweight which we were able to do to some degree. This helped to counteract the drop in acceleration you would expect from gearing for such a high speed.

On full field runs, our gear ratio worked as we wanted it to. To go along with all of this, we had a control scheme (known as Cheesy Drive) that allowed us to control the robot remarkably well at high speed. Our problem was misreading the game slightly, where full field runs weren't as necessary as we thought they may be. Knowing what we know now, we wouldn't have shot for such a high speed.



-Brando

Re: pic: Uber 3.0
 

Actually, I'd estimate that I understand the world of FRC robots as much as you. Rather than "surprised", I am fully aware of this probability year to year, including my own team's inclusion in it. Regardless, you ignored part of my logic: were PINK and Spartronics geared for 'high speed' such that they (even unknowingly) traded off the pushing torque for more speed?

PINK, iirc from DC, was geared for 12 ft/s after friction. They traded the extra speed for more torque so they could go to a single-speed drive without the worry of being pushed around most of the time. This tradeoff was obvious from just a short conversation with them, so I'm not deducing it deduced so much as I'm re-stating it. Only they can say how much they felt they were pushed around this year since video seems to be rare for 2011. For the first 0:45-ish of the 3rd Finals DC match, we totally shut them down*.

*Then our chain broke, and all of the coulda-shoulda-woulda's set in :ahh: ... lessons learned for the future, heh.

Re: pic: Uber 3.0
 

Nice modeling, and I LOVE the V8 look!

Re: pic: Uber 3.0
 

at champs we went down to about 7-8fps, but the ratios weren't our only problem earlier on. our arm was still geared waayyyyy to high. it was about 1 second to rotate from collecting on one side to collecting on the other with a single banebot. as a result power and acceleration seemed to tank when the arm was moving about (which is ideally quite a lot).

in the end we just weighted up to 120 and geared to be traction limited because we don't like getting pushed around

Re: pic: Uber 3.0
 

What is this cheesy drive you speak of?

Re: pic: Uber 3.0
 

Check out the drive code in this: http://www.chiefdelphi.com/media/papers/2397. For more information, talk to Austin, Tom or Kiet would be your best bet.

Nick

Re: pic: Uber 3.0
 

Sorry, I'm not a programmer so I don't have the software to view it (CAD actually takes up most of my computer) but i will have one of my guys look at it and explain it to me, but thanks for sharing!!