Re: Week 2: Any new lessons learned?
 

It depends on what you mean 'not made to play defense'. You can play defense with Mecanums etc. It's more about the driver and strategy. Defense isn't all about blocking/pinning/pushing...

Re: Week 2: Any new lessons learned?
 

In the past mecanums have been able to get in front/between the opposing robot and objects. This year with zones and penalties for contacting a tower if you are trying to keep hostbots from towers, mecanums are toast! With no pushing power you will get zone violations.

Re: Week 2: Any new lessons learned?
 

Jim and Brendan-

Thanks for setting me straight. 2 CIMs with 2 or more speed transmissions can work for some games.
Do you have an idea how prevalent it is for top robots for the different games?

I can understand the value when a robot is mostly driving around a track or when the field has little traction.

But the race to an object and then race to somewhere else (and maybe push some bot out of the way) type games seem to me to be more conducive to 4 CIMs. (But I'm relatively new to this)

Thanks again.

Re: Week 2: Any new lessons learned?
 

If it is legal next year, I will push for a 8 or 6 CIM drive... Yep thats right, 6 or 8 wheel drive with a motor powering each wheel.

Re: Week 2: Any new lessons learned?
 

2006 and 2009 seem to be the years in which 2 cims were popular as 2009 didn't need cims and 2006 saw a lot of teams using the cims for their shooters.

Every once and a while a top robot may have a 2 cim drive but it depends on the game and it is rare.

Re: Week 2: Any new lessons learned?
 

in 06 both 968 and 254 actually had 2 CIM's and 2 FP's in the drive. It was a miserable year in terms of drive reliability. We smoked more FP's than I can even remember and swore from that moment on we'd never use them in the drive again.

Re: Week 2: Any new lessons learned?
 

Was it the FPs that caused the drive issues or the CIMs? I can't remember us having issues in 08 but our transmissions weren't shifting which I'm sure adds to the likelihood of malfunction.

Re: Week 2: Any new lessons learned?
 

Defense this year is not always about robot defense. We had a non-functional lift at Wisconsin this week and were forced to play defense. We had a mecanum drive, with aggressive gearing. Even with this "disadvantage" we were able to play a good defense. Tubes can be moved out of position, robots can be hit while trying to acquire the tubes, and robots can be blocked as they travel towards the minibot tower. Its not always about the shoving match, its about hitting them at the right time, moving the tubes, and getting in the way.

During eliminations, we were on a primarily defensive alliance. We managed to almost tie the number 2 alliance based solely on defense and minibot.

Re: Week 2: Any new lessons learned?
 

Pretty sure it was the FPs. I remember 968 picking up at least one FP at Spare Parts in L.A.

Re: Week 2: Any new lessons learned?
 

The FP's were the problem. Part of the problem was due to seizing AM planetaries, if I remember correctly. AndyMark has since made improvements to the transmissions that would probably yield better results today.

Re: Week 2: Any new lessons learned?
 

My reading of the CD spreadsheet on motor/drivetrain simulations does not bode well for much improvement for 6 to 8 motors over 4.
With 4 CIMs, a bot can accelerate faster than a real athlete. Typical distance to target is 5 to 30 feet.
Special Gearing and traction are probably more useful than more weight on generating force/work into the drivetrain.

If your strategy is to push robots and not much else, then being ALL legs might be useful- if you can do it without ripping up the carpet.)

Re: Week 2: Any new lessons learned?
 

This has yet to be legal in FRC.

Even if it was, you have serious considerations with battery loading, current draws, etc. You also have to consider that because FIRST robots are traction limited, you have a hard limit on the amount of pushing power you can add.

The net effect of adding more motors to a drive is allowing you to gear a robot to be traction limited at a higher top speed. At 2 CIMs, gearing for ~3 FPS makes you traction limited with roughtop at 40 amps. 4 CIMs gets you there around the ~5.5 - 6 FPS range. 6 CIMs takes you up around 9 FPS.

Of course, few teams do this as most of those numbers are quite slow. 2791's drive this year is traction limited a bit above stall - not designed for pushing. our 6 motor configuration is traction limited at about 55 amps.

Re: Week 2: Any new lessons learned?
 

our 2007 bot was a brutal defender with only 2 CIM's. Good gearing, AM shifters
and the ability to transfer the power to the ground efficiently was they key.

Re: Week 2: Any new lessons learned?
 

Thanks! Learn something new everyday and if it is FRC learn two new things a day! :p

Re: Week 2: Any new lessons learned?
 

Are you sure about this 6 point thing?
I count the score for a single ubertube LOGO to be 30 points and not 36... am I reading this wrong? 6 for the autonomous ubertube
one ubertubed score plus two non ubertubed scores in a logo would b 6 + 3 + 3 = 12
which is doubled to make 24 ... now add the original 6 points in and you get 30 points for that single ubertubed logo.

We hope to be able to do this...and in practice we can get it done in just over 1 minute so far. We hope to bring that speed up during competition... so perhaps 2 logos are possible..

So a single ubertubed logo would be worth exactly the same as the fastest minibot.


Your second comment is a good one (along with your other observations..:0))

I agree that IF you are short on time and you can complete a logo... it might be worth the penalty... the complete logo (assuming it is NOT an ubertubed one....) would actually give you 3 points for the tube and then double the other six points... so your 3 pt penalty could net you + 3 for the tube and + 9 for the logo bonus... subtract the penalty of 3 and you get a net benefit of 9 points...

Definitely something to think about.

Of course all of the above scenarios only hold for the top rack... diminishing returns as you move down the rack...

good points!!