Best Drivetrain

[R.C.]

I am posting this because a rookie team in Davis was having a hard time deciding and creating a drivetrain for their robot. There have been many different types of drivetrains used in FIRST. So in order to help all the rookie teams for nex year, what drivetrain has been the most dominant from the 2005 season and on?

-rc

ps Pictures please

[Rick TYler]

Originally Posted by rc_cola1323

what drivetrain has been the most dominant from the 2005 season and on?

I would say the KOP transmission with 2 CIM motors per side, driving six wheels via chains. More robots use this than all other layouts put together. My observation. YMMV. Offer not valid in Michigan.

[sdcantrell56]

6 wheel drive with either lowered center wheels (~1/8") or omnis on the corners. This has without a doubt been the most successful drivetrain in the past and is very simple to build. As long as you can build a 4 wheel drive you can fairly easily add 2 more wheels. If you really want to improve it, add traction wheels such as ifi and a 2 speed transmission. An even better addition is directly driving the center wheels off the transmission shaft so that even if all of the chains break the robot will still be powered. This requires a little bit more work though and most likely precise machining capabilities.

[JesseK]

If you really want to improve it, add traction wheels such as ifi and a 2 speed transmission. An even better addition is directly driving the center wheels off the transmission shaft so that even if all of the chains break the robot will still be powered. This requires a little bit more work though and most likely precise machining capabilities.

Specifically, it requires a longer output shaft than any standard transmission will give you.

Usually it's just as much weight to do the bearing blocks for a direct drive setup as it is to do an AM hub with AM flat sprockets with extra chains. Since it's more difficult to do the former, most teams stick with the default method.

[Rick TYler]

Originally Posted by JesseK

Usually it's just as much weight to do the bearing blocks for a direct drive setup as it is to do an AM hub with AM flat sprockets with extra chains. Since it's more difficult to do the former, most teams stick with the default method.

My old FRC team has never built a really great robot (sad, but true), but their chain-driven, 6WD chassis with the KOP gearbox has been bulletproof all four of the last seasons. The concerns about breaking #35 chain (in my experience) are exaggerated -- if you don't do anything weird or stupid, they simply won't break before the motors stall out. When you start getting into more exotic choices, stuff starts breaking. It might be worth it if you have a sophisticated robot and build process, but I think most teams would be well-advised to go with a proven drive-train and spend their brain cells on building better game mechanisms.

[sdcantrell56]

Direct drive does require modifiying all but the andymark super shifters. Although getting a longer shaft machined is really not that difficult. My preference for direct drive is that even if all chains somehow snap, the robot will still perform just as well since the center wheels are always in contact with the ground. This also makes it slightly more reassuring to use #25 chain since no matter how many chains break the robot will still run. #25 chain saves a ton of weight over #35 and it also only uses 4 chains versus at least 6 in a normal 6 wheel drivetrain. The only thing to remember with #25 and really even #35 chain is to have a way to easily tension the chain. If you can keep the chain tensioned and lined up properly then you will never break a #25 chain.

[EricH]

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.

[Brandon Holley]

Originally Posted by EricH

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

While this may be good advice a good chunk of the time I feel as it may be a little bit of blanket statement. Although I'm sure you had no mal intent.

I have seen very capable rookie teams that would be able to handle making a swerve or holonomic and I've seen many many many veterans who would not be able to pull one off.

Judge your teams capabilities...if a task looks daunting, it probably is...if you think your team may be able to pull it off, go for it. FIRST isn't about winning, its about learning. Go for the design that will knock peoples socks off...who cares if you dont get 2 weeks to drive it around before competition. Thats just my honest opinion.

[Tom Bottiglieri]

Originally Posted by Brandon Holley

Judge your teams capabilities...if a task looks daunting, it probably is...if you think your team may be able to pull it off, go for it. FIRST isn't about winning, its about learning. Go for the design that will knock peoples socks off...who cares if you dont get 2 weeks to drive it around before competition. Thats just my honest opinion.

While I agree with Brandon on most topics, this is one we don't see eye to eye on.

In my experience a fully functioning, simple robot is much more effective and reliable than a figurative time bomb on wheels. Remember that reliability is a part of your scope, as is function. If this doesn't click, think about what you look for in a car. There's a reason Honda and Toyota have risen to the top of the proverbial food chain.

The enemies of scope are time and cost. (FIRST has a third enemy: experience. But that is for a different discussion!)

Broken robots = stressful = no fun = less inspiration

[Brandon Holley]

Originally Posted by Tom Bottiglieri

While I agree with Brandon on most topics, this is one we don't see eye to eye on.

In my experience a fully functioning, simple robot is much more effective and reliable than a figurative time bomb on wheels. Remember that reliability is a part of your scope, as is function. If this doesn't click, think about what you look for in a car. There's a reason Honda and Toyota have risen to the top of the proverbial food chain.

The enemies of scope are time and cost. (FIRST has a third enemy: experience. But that is for a different discussion!)

Broken robots = stressful = no fun = less inspiration

No one said the robot had to be broken...just because it is more complex, or took more time to develop doesn't mean it is going to break.

I dont know tom, i guess we'll have to agree to disagree here...it seems to me that learning some more complex engineering substance is just as valuable as any other part of FIRST.

[Chris Marra]

Originally Posted by Brandon Holley

No one said the robot had to be broken...just because it is more complex, or took more time to develop doesn't mean it is going to break.

I dont know tom, i guess we'll have to agree to disagree here...it seems to me that learning some more complex engineering substance is just as valuable as any other part of FIRST.

I have to back Tom on this one, mostly because I think he just has another take on the same issue. Teams sometimes need to make a decision about where they aim to provide the most inspiration to kids - in the workshop through innovation, or at the competitions through empowerment when they see their creation. Sure a complex design is an amazing feat to accomplish and everyone can take pride in it, but how much fun is it if you don't finish it or you don't get a chance to utilize it because your focus was on making it happen at all. If you can finish your design early you get to show kids another very important aspect of engineering - testing and training. If you took any talented driver and told them they would be driving a Wildstang robot for the first time at a competition right after the coders finish testing, they would flip out. Not everyone can take a positive message out of a complex design if they don't pull it off in time or they don't get to use it to its fullest. I don't want to come off saying that winning is the inspirational experience, but sometimes competing needs to take a little more precedence over designing and learning how to tackle a complex project like any robot within the constraints of the competition is something teams ought to consider too. So there is nothing wrong with attempting a complex design, because there is no reason it shouldn't succeed, but teams ought not lose sight of their final goal: to have a competitive, fully operational robot completed within six weeks (without forgetting about their drivers or coders!)

[Brandon Holley]

Originally Posted by Chris Marra

I have to back Tom on this one, mostly because I think he just has another take on the same issue. Teams sometimes need to make a decision about where they aim to provide the most inspiration to kids - in the workshop through innovation, or at the competitions through empowerment when they see their creation. Sure a complex design is an amazing feat to accomplish and everyone can take pride in it, but how much fun is it if you don't finish it or you don't get a chance to utilize it because your focus was on making it happen at all. If you can finish your design early you get to show kids another very important aspect of engineering - testing and training. If you took any talented driver and told them they would be driving a Wildstang robot for the first time at a competition right after the coders finish testing, they would flip out. Not everyone can take a positive message out of a complex design if they don't pull it off in time or they don't get to use it to its fullest. I don't want to come off saying that winning is the inspirational experience, but sometimes competing needs to take a little more precedence over designing and learning how to tackle a complex project like any robot within the constraints of the competition is something teams ought to consider too. So there is nothing wrong with attempting a complex design, because there is no reason it shouldn't succeed, but teams ought not lose sight of their final goal: to have a competitive, fully operational robot completed within six weeks (without forgetting about their drivers or coders!)

Chris/Tom

I agree with you guys, but I think your missing my point. I am not saying to go out and build some ridiculous design...but as a rookie team I feel it is good to set a precedent that you are going to do your best to make a robot that is to your ability every year. Some teams simply cannot machine an entire drivetrain, that is understood...but if a team has the means to make a part of their drivetrain, a little complicated, or innovative, why not?

I think it is important to balance the idea of "being competitive" with learning science and technology too.

I guess what I fear is a team saying, well yeah we could do that, but why don't we just buy this and call it done...

[Tom Bottiglieri]

Originally Posted by Brandon Holley

I guess what I fear is a team saying, well yeah we could do that, but why don't we just buy this and call it done...

I don't think anyone is doing that. I just think the drive base aspect of FIRST robots has gotten to a point where it is more economical to "drag and drop" components. Design considerations for "learning" can be made in other areas of the robot.

You have when to hold your cards and when to fold your cards. Take the ace that FIRST has given us and build the kit chassis or a simple 6wd setup with COTS. The time you save will allow you to invest more into your functional designs, which are usually the things that make or break a robot design.

[Jeff Waegelin]

Originally Posted by Tom Bottiglieri

While I agree with Brandon on most topics, this is one we don't see eye to eye on.

In my experience a fully functioning, simple robot is much more effective and reliable than a figurative time bomb on wheels. Remember that reliability is a part of your scope, as is function. If this doesn't click, think about what you look for in a car. There's a reason Honda and Toyota have risen to the top of the proverbial food chain.

The enemies of scope are time and cost. (FIRST has a third enemy: experience. But that is for a different discussion!)

Broken robots = stressful = no fun = less inspiration

This was probably one of the biggest lessons I took away from this year. Over the course of my FIRST career, my designs have ranged from the super-simple to the super-complex, and everywhere in between. This year was by far the best robot I've ever worked on, and it was also probably one of the simplest. Coincidence? I think not. Everything was simple and reliable, and it worked every time (barring a mishap with a wire and the terminal block). After 4+ years of constantly having to fix things at every event, I had two stress-free competitions, both of which were greatly successful.

The takeaway from all of this: especially for drivetrains, most teams will benefit from something simple and reliable. The less experience and assistance you have, the more critical this becomes! The last thing you want is to spend your whole competition season getting the robot to move. A 6WD chain drive may not always be the perfect drivetrain for every competition, but it's easy, simple, and reliable, and it will always be serviceable and successful for any game. (Until we get that water game, or Dave punishes us by banning all wheels.... )

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.

[Doug G]

I have to chime in here as well.

1) There's no rookie team in Davis, maybe they were referring to a rookie team that attended the Davis Regional.

2) Not to stiffle creativity and the thrill to innovate, but for a rookie team or 2nd year team - I highly suggest a robust 6WD setup with kit transmissions (if supplied).

Pic... http://www.travisusd.k12.ca.us/vande...n/DSC05175.JPG

Last year was probably our most reliable drive system (yes - even with banebots). Kit transmissions, chained to a center-traction wheel (kit wheels), the center wheel chained to the front and back wheels. Tensioned with UMHW off-center cams. The whole drive system was put together using nothing more than a cordless drill and a band saw (neglecting the welded frame which could be replaced by a kit frame).

THE MOST IMPORTANT THING FOR A ROOKIE TEAM IS TO GET THEIR DRIVE SYSTEM WORKING BY THE END OF THE THIRD WEEK. Our team was very competitive last year, simple because of it's dependablity and driver practice. Our drive team had over a week of practice before ship.

3) Use innovative ideas to develop a cool manipulator or strategy. There's absolutely nothing more troubling than to have your robot unable to drive.

I think back to the days of 2000, 2001, 2002 when there was no simple drive system that came in the kit. You had some cordless drill motors, transmissions, and skyway wheels that you had to make work. That took our team the bulk of the 6 weeks.