Chief Delphi - Best Drivetrain

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Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Technical Discussion (http://www.chiefdelphi.com/forums/forumdisplay.php?f=22)

- - Best Drivetrain (http://www.chiefdelphi.com/forums/showthread.php?t=67367)

Nikhil Bajaj

30-04-2008 17:19

Re: Best Drivetrain

Quote:

Originally Posted by Lil' Lavery (Post 744499)

I was not trying to suggest that any drive-train was superior, I was just supplying facts. Notice how I didn't even post any conclusion, just raw data. Some may have drawn erroneous conclusions from this, and I apologize for that, but that was not my intention. It would be silly to judge this data without full numbers on the amount of teams, teams with each drive, and other data. But, sadly, most of that data either doesn't exist, or would be next to impossible to compile, and to make any assumptions about it could and would lead to equally erroneous conclusions. It would be plain stupid to ignore the manipulators, software, electrical reliability, drivers, strategy, and alliance formations of each of the champions as well.

Take it with a grain of salt. It isn't showing the relative superiority of any drive method, rather showing the drives that a handful of successful teams have selected and done well with, for whatever reason, since 2005. Strong teams with strong engineering principles selected these drive-trains for various reasons, that's all I'm saying.

I guess I just wanted to make sure that nobody was making those erroneous conclusions ;) . I didn't mean to imply that you were in particular, my apologies.

On another note, and somewhat drivetrain related, does anyone have experience with using the Gates synchronous belting that has been supplied with the kit on a drivetrain?

Lil' Lavery

30-04-2008 17:27

Re: Best Drivetrain

Quote:

Originally Posted by Nikhil Bajaj (Post 744528)

On another note, and somewhat drivetrain related, does anyone have experience with using the Gates synchronous belting that has been supplied with the kit on a drivetrain?

See the post by Shan of 612 earlier in this thread.

T3_1565

30-04-2008 17:31

Re: Best Drivetrain

I like direct drive myself! Mainly because our linkage wouldn't work without it (generally... I suppose I could find a way.. but direct drive is the easiest way). That and because we don't have precison tools, tension is harder to maintain (it can be done, but is done much better with pecison)

We used all direct drive this year (4 omnis), those banebot transmissions have a nice long output shaft for that!!:D

roboticWanderor

30-04-2008 22:21

Re: Best Drivetrain

Quote:

Originally Posted by Jeff Waegelin (Post 744074)

An addendum on the #25 versus #35 question: I consider myself to be a pretty experienced designer, but I will ALWAYS use #35 for drivetrains. It doesn't matter how well you can CAD a drive base, if your fabrication tolerances are not tight enough, you WILL have problems with #25. I will take the reliability and forgiveness of #35 over the weight savings any day. I've seen too many #25 systems fail due to misalignment to do it any other way.

Team 418, Purple haze has been using #25 chain for 5+ years and never had any failure in the chain itself. we have very limited machining and fabrication capabilities, limiting to a manual lathe, chop saw, band saw, and drill press. it really is not difficult to construct a functioning drive train with those tools and a large Tsquare. not only that but since before 2007 they had 3/4" plywood bases with aluminum pillow blocks (made form box alum wit ha band saw and drill press) and bearings from mcmaster.
honestly there is little trouble from #25 chain besides tension, and there are plenty of easy solutions to tensioning the stuff, that require little more than a idler sprocket or delrin or something like that, and you probably wont need to tension that chain more than once, unless you go to multiple regionals and nationals and i double that many rookies are doing ALL of that. in other words #25 is perfectly sufficient for the purposes of a FIRST rookie team, and allows that extra 5 lbs to go towards something else more deserving

Jeff Waegelin

01-05-2008 13:06

Re: Best Drivetrain

Quote:

Originally Posted by roboticWanderor (Post 744629)

Often the key to meeting proper tolerances is not the equipment, but rather the people using it. If you have experienced people using basic manual tools, they will produce good results. If you're involving high school students with minimal experience in your build process, sometimes those tolerances don't end up quite as tight as you would like. I'd rather just use #35, and then not have to worry about it.

zivo123

01-05-2008 13:32

Re: Best Drivetrain

Quote:

Originally Posted by EricH (Post 743982)

Sorry, guys, but you are ALL wrong.

The correct answer is: we don't know.

The game hasn't been released yet. Maneuverability might be key, power might be key. We don't know. We won't know until January.

That said: Rookies should NOT attempt a swerve or holonomic. Even veterans have trouble with those sometimes.

4WD or 6WD skid steer, Kit frame, would be my best advice. Those are really versatile, especially the 6WD drop center. Kit trannies would be recommended, but I'd have to see the game before committing to anything. Exactly what setup depends on the game. Chain drive, due to ease of use. Because this is a rookie team, tensioner of a block of delrin under or over the chain mounted so the chain digs into it a little. While it is possible to get away with not using a tensioner, that's something that only a veteran team or a team with decent CAD/manufacturing ability should attempt.

I saw this, especially the sentence i've bolded out, and had to comment. 6WD isn't a hard or expensive thing to build. I was a rookie this year but if you ask me, I believe it should be built before the kickoff. just have a vote on the second or third day wether you want to change it or keep it after you see what the game will be like. This year, we didnt do that. Our lead mentor insisted on what Eric said, and we ended up finishing our drivetrain on the second week (we've ordered sprockets on the end of week one). So here its a bit differen because after you order something here it takes it a week and a half to come.
So that was my 0.02$ :)

Rick TYler

01-05-2008 13:46

Re: Best Drivetrain

Quote:

Originally Posted by zivo123 (Post 744786)

6WD isn't a hard or expensive thing to build. I was a rookie this year but if you ask me, I believe it should be built before the kickoff.

You are not allowed to build your competition robot before the build period starts, which is the kickoff. Anything you build before that date is not legal for competition.

Quote:

<R27> Prior to the Kick-off: Before the formal start of the Robot Build Season, teams are
encouraged to think as much as they please about their ROBOTS. They may develop
prototypes, create proof-of-concept models, and conduct design exercises. Teams may
gather all the raw stock materials and COTS COMPONENTS they want. But absolutely no
fabrication or assembly of any elements intended for the final ROBOT is permitted prior to
the Kick-off presentation
<R28> During the Build Season: During the period between the Kick-off and ROBOT shipment
deadline, teams are to design and fabricate all the COMPONENTS and MECHANISMS
required to complete their ROBOT.

EricH

01-05-2008 14:18

Re: Best Drivetrain

To add to what Rick said: There were possibly rumored cases of this happening in the 2004 season. Size constant, build now, we'll do the manipulator later.

The result: Instead of 36" x 30", you now have to fit in a 38" x 28" box. If you try that and say that on here, there is a risk that the GDC will decide to change the sizing on you.

The size has changed AT LEAST three times that I know of. Something small, 36" x 36", 36" x 30", and now 38" x 28".

zivo123

01-05-2008 14:18

Re: Best Drivetrain

Quote:

Originally Posted by Rick TYler (Post 744789)

You are not allowed to build your competition robot before the build period starts, which is the kickoff. Anything you build before that date is not legal for competition.

Oh cmon. The Robonauts are using the same compex mechanism for three years now (correct me if i'm wrong). I'm sure the didnt build the whole thing from scratch this year. And even if the did i know of a lot other teams doing that..

Anyway, I do thank you for the comment, I personally didnt know that and Its good to know. Its probably best not to educate the rookie teams to bend the rules..

Triple B

01-05-2008 14:23

Re: Best Drivetrain

[quote=zivo123;744793]Oh cmon. The Robonauts are using the same compex mechanism for three years now (correct me if i'm wrong). I'm sure the didnt build the whole thing from scratch this year. And even if the did i know of a lot other teams doing that..

I would be interested in the list of all those other teams that you know about
mike d

EricH

01-05-2008 14:24

Re: Best Drivetrain

Quote:

Originally Posted by zivo123 (Post 744793)

They have used the same basic drive and arm strategy for a while now.

But I am sure they do NOT use the same mechanism from year to year! We were all surprised when they unveiled the V6 in 2007. They improved it the next year.

Oh, by the way, if you're going to accuse 118 of this, then you also need to go after the following:
--254/968 (drive)
--60 (drive)
--25 (drive)
--330 (most of the robot, 2005, 2007-2008)
--16 (drive)
--233 (arm and drive)

You see my point? A lot of teams build on old designs. They don't necessarily use the same parts (which is also prohibited--no build pre-kickoff, and no re-using mechanisms from old robots). So I'm guessing that they just say, "Does this work for the game? If not, how do we change it?" and then re-engineer to optimize for the new game. They build in 6 weeks just like every other team.

AdamHeard

01-05-2008 14:32

Re: Best Drivetrain

Quote:

Originally Posted by zivo123 (Post 744793)

That is quite an accusation, and I am sure they did build the whole thing from scratch after the kickoff date.

T3_1565

01-05-2008 14:38

Re: Best Drivetrain

once you build a drivetrain, it becomes very easy to build again from scratch, so although it may seem prebuilt (because they finish so fast) its not, its just they have all the resources set up to build something, all bugs were worked out on the other system, and all upgrades were prototyped.

I know for a fact it took us 3 weeks to build our Linkage drive during build season, and I know we could put another one together (given we have metal to do so) in about 4 days. Once you have a plan, things come together very easily.

Brandon Holley

01-05-2008 14:56

Re: Best Drivetrain

Quote:

Originally Posted by zivo123 (Post 744793)

wrong answer my friend...

Your first assumption that is completely wrong is that they have been using the same mechanism each year. Look at their DT last year and this year....they are not the same, although they may accomplish the same result (swerve/crab drive that totally rocks)

What else have you heard about other teams?

I guarantee they build the entire thing in their given timeframe.

You cannot make allegations with no support against other teams on this forum, its not fair to them, or to anyone else that cruises chiefdelphi because then someone has to take the time to explain to you how wrong you are about this.

There is no rule in FIRST about tweaking an old design and using it again in a year, this is the advantage experience brings.

Lil' Lavery

01-05-2008 15:02

Re: Best Drivetrain

Quote:

Originally Posted by zivo123 (Post 744793)

The robonauts have been using a swerve drive since 2005. Each of their robots have had turreted manipulators seated on top of it during those 4 years. The similarities end quickly after that. They have constantly evolved, just unveiling their "V6" last year, and updating it again this year (no DeWalt this time). They have made massive updates and advancements to their electronics each year, and their manipulators have varied greatly as the games vary.
Just because a team uses similar designs each year, doesn't mean they cheat. It means they have found a system that they find works for most games, and ways to implement it year after year successfully. And just because its complex doesn't mean it's cheating either. 118 has a history of technical proficiency, some of the best mentors, and very smart and dedicated students. I'd suggest you do a little more research before making such bold claims.

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