If you’re looking for a superior drivetrain, I strongly suggest you look hard into the possibility of a track system. Well designed, a tracked 'bot will push anything else on the field, forward, backward, or sideways. Tracked bots can turn on their footprints, and with the right transmission can go as fast as any other bot.
753 has racked up a bit of a record on the strength of our drivetrains. Last year we won the PNW regional and went to nationals, where we took a divisional third along with 254 and 71. We did it on the strength of our drivetrain; our scorer hardly worked at all but we could guarantee to stop other bots from scoring. 254 knew it was a very strong complement to their scoring, and they drafted us in PNW and at nationals.
This year we’re pleased to partner with our sponsor, Outback Manufacturing, to make our award-winning drivetrain available to other teams. Outfitted with a 2-speed transmission, the 'train can go 17 FPS in high gear, and in low has more pushing power than last year’s bot!
Because of the lead time to do with the belts from Breco-flex, we need to know whether you’re doing it pretty soon so you can get the belts early in the season. Email me at ari.allynfeuer@gmail.com or use a forum PM to talk about it.
First, and most important, what do you want out of it? Do you want speed, maneuverability, or power? To some extent, these three will not work together without a shifting transmission.
For speed: high gearing with any transmission/wheel pattern will work, if you do your calculations right.
For maneuverability: 2-wheel, 6-wheel with a dropped center, swerve, or mecanum are your basic options. You want to avoid using swerve and mecanum until you have explored them. Some teams make these look easy, but they aren’t.
Power: low gearing with anything, but no speed.
Tank treads: Be careful. One tread comes off, you are disabled for the rest of the match. You have to design right for treads.
Bottom line: Explore a bit. If you are a rookie, you should be somewhat conservative on complexity. After that, explore all the options you like. Do the power curves to find out what the trannies will behave like. Try shifting.
If you’re expecting teams to order now so that you’re able to provide these units “early” in the build season, you are not in compliance with the 2006 rules regarding what constitutes a vendor. The rules require that you ship your product no more than five days after receiving an order. Unless the rule changes drastically or you take measure to stock belts, teams cannot use a drive purchased from your team on a competition robot.
Can you explain more about the mechanism your team has in place to comply with FIRST’s rules defining what a vendor is?
I don’t mean to doubt anyone’s abilities but you want a rookie team to build a track system? And it will be superior? Track systems are riddled with all sorts of inherent problems, and unless there is a step to climb (which I’m actually fairly certain there will be, but we’ll see) I haven’t seen a compelling argument for the use of them.
The lead time has nothing to do with Outback. Breco-Flex, one of three official FIRST suppliers cooperating on this, has a manufacturing lead time of 3 to 4 weeks. We need to have a sense of who’s doing this so we can get the first production run from Breco-Flex in their pipeline in time to deliver the system early in the season.
These kind of delays are not an unfamiliar prospect to FIRST teams or any other intercorporate purchasing arrangement, and the rules from 2006 (And, it is safe to assume, 2007) allow for the delays inherent in this kind of thing. Would you say Breco-Flex is not a Vendor?
What we’re trying to do is simplify the insane free-for-all of custom ordering from Breco-Flex that goes on. To make it easier for Breco-Flex by using a single size, and to make it easier for the teams by reducing the lead time by keeping the tracks in stock.
Outback is an established manufacturing shop with all the requisite tax numbers, and the delays are the result of a third-party supplier which is an official FIRST supplier. We don’t anticipate any rules issues.
I think this highlights some interesting issues that I’d like to continue discussing, so I’m going to begin a new thread in the General Forum to address those concerns so as to avoid derailing the continuing valuable discussion about drive trains.
Team 2199 as of now is not interested in buying anyones drive train although we appreciate the offer and admire your entrupenuerial spirit. I was just looking for some guiding princilples and ideas. Right now (unless this years comp throws a monkey wrench in our plans) we are looking at a six wheel drive. We are a rookie team but the officers are all veterens from another team so we have have a bunch of rookies under veteren leadership.
The tracks that 195 has used for the last few years have been ordered from Breco-Flex. Overall great quality, but like Eric H said, one track slips and your completely disabled from the match, we experienced alot of that in the 2006 game, which we partially attribute to the defined defensive period, in which we got pushed from angles that never quite hit us before. My main concern with Breco-Flex is that return time on ordering tracks was anywhere between 5-7 weeks, which made it pretty hectic after we snapped 8 tracks at our first regional =O
Actually, to be precise, no they are not. There are only five organizations that have been sanctioned by FIRST as “official suppliers” for FRC. These companies are not included in that set.
Until the rules for the 2007 FRC challenge are released and everyone has a chance to read and understand the requirements, constraints, and limitations specified for the 2007 game, I think that that this is something that NO ONE will want to do. Teams do not yet know what may be included in the 2007 rules that may constrain sources for additional (non-KOP) parts, limit purchased components to a given level of complexity, restrict the cost or size of additional elements, proscribe the permissibility of pre-ordering parts and components, or define the timing under which materials for the competition robots may be purchased. It would be a shame if a team were to commit a significant portion of a limited budget on a component pre-ordered before the 2007 kick-off, only to find once they read the rules that the component was not permitted in the 2007 FRC competition.
As far as a drivetrain, keep it simple and to the point. What is the goal and the game? 2 wheel drive with skids is highly maneuverable, 4 wheel drive will do it in most cases. Tank treads and 6 wheel drive are Ok if you can do it, but do you need it? My advice is to keep it simple and reliable. Think in terms of maneuverability and traction and always remember the game.
The Drivetrain Improvements white paper from IFI is an excellent read, as are all the white papers at IFI’s page about the kitbot. (I especially like the one about the chassis design process) Anyway, the “Drivetrain Improvements” whitepaper essentially compiles and distills a lot of drivetrain advice and knowledge into 10 succinct pages. (With lots of diagrams) Many of the whitepapers on Chief Delphi go into greater depth, and have many other, more radical, designs, but this one goes through lots of simple alterations to the kitbot that can make your robot more competitive. From personal experience, I can say that a kitbot with 6WD and tread added to the wheels makes a very nice and competitive drivetrain, and only requires 2 additional KOP wheels, sprockets, and 4 more hubs. (Although, if you’re like us and spend $160 on sprockets it could get a tad pricey)
Does anyone know what size chain and sprockets have been in the KOP for the past 2 years? Our team is looking at ordering some general stuff ahead of time ( some aluminum stock, sprokets, chain, etc) and we are willing to take the risk of ordering unnecessary parts and a minor hit in the purse if it could keep us from having to wait two weeks into build season for crucial drivetrain parts.
Chain’s been #35 for as long as I remember. The sprockets have been 21T on the transmission and 28t on the wheels. You can get any and all of these parts off of IFI’s site, or go to a site like McMaster-Carr or MSC for more selection.
This is crucial to your success
1: Measure 3 times, cut once
2: Make absolutely sure beyond all reasonable doubt that everything is perfectly aligned in all dimensions.
Have one up front and 2 in the back.