drive train
 

where can i find info on drive trains?

i have been assigned the tentative drive train captain for this year and for the past two years have usually been on the other design teams
(manipulator, ball picker upper, etc). Anyhow, i don't know a whole lot about FIRST drivetrains although i understand torque and basic physics principles.

i just need some guidence and any tips and tricks on designing and building drive trains for a FIRST robot.

thanks alot

Re: drive train
 

Go to the FRC conference archives there is atleast 1 power point in there about drive systems

James

Re: drive train
 

Here are some transmission prints. Formally used at tkat transmissions.

Re: drive train
 

I believe this is the powerpoint that JamesBrown is talking about.
Also you may find these whitepapers useful:
http://www.chiefdelphi.com/media/papers/1705
http://www.chiefdelphi.com/media/papers/1443

Re: drive train
 

The gallery of photos maintained by the FIRST Robotics Canada folks is pretty helpful, too. There's not much exposition, but looking at the pictures can show you a lot about the practicality of implementing certain ideas.

http://www.firstroboticscanada.org/site/resources

Re: drive train
 

I always find the Chief Delphi white papers useful. There is a link to them on the portal page. You can search through a bunch of different transmission ideas and designs. No matter how many times you built and designed a bot in never gets old. Good Luck with your search and this coming season.

-Drew

Re: drive train
 

thanks guys

Re: drive train
 

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.

Ari.

Re: drive train
 

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.

Re: drive train
 

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?

Re: drive train
 

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.

Re: drive train
 

They don't want them to build a track system. They want them to buy it. :rolleyes:

Re: drive train
 

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.

Thanks,
Ari.

Re: drive train
 

And these systems would count as COTS parts, right? If they don't, then you should really be gauging interest, not ordering.

Re: drive train
 

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.

Re: drive train
 

Once again, you do not need to lower your center wheel.

Re: drive train
 

everyone else needs to :)

Re: drive train
 

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.

agian, many thanks

Re: drive train
 

I understand fully. It's not a thing everyone will want to do.

I'm glad you gave it a thought, and I hope we'll see you on the field in a few months. If you have any questions drop me a line.

Ari.

Re: drive train
 

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

Re: drive train
 

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.

Just a word to the wise...

-dave

Re: drive train
 

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.

Re: drive train
 

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)

Re: drive train
 

I think the best drive train you can have is 3 wheels. weight is everything. :D Have one up front and 2 in the back.

Re: drive train
 

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.

Re: drive train
 

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.

Re: drive train
 

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.

Your success depends on it.

Re: drive train
 

If you're ordering from one of the major suppliers like McMaster, Motion Industries, MSC, SDP-SI, etc they should all be able to get you your order in less than a week, on standard shipping.

Re: drive train
 

We can get things from MSC delivered next day from PA to VA and only pay ground shipping if we order by mid-afternoon. Your signature says you are in "E-burg", and I have no idea what you mean, so I can't help you on delivery times.

#35 has been the standard the last couple of years. If you have a local Graingers, you can get sprockets and chain readily. As for aluminum stock, see a real metals supplier in your area. They may be billed as a steel supplier, but they should also carry aluminum. It should cost you perhaps less than $3./lb. for tube and strap, $4./lb. for flat plate, depending on alloy, of course.

Re: drive train
 

I haven't looked at prices recently -- and I understand that they're rising -- but we've never paid more than $2.50/lb. for aluminum here. Are prices elsewhere typically that much higher?

Re: drive train
 

I was speaking generally. I don't recall if our 1" square tube was $2.65 or $2.95 per pound. It worked out to roughly $1.50 per foot or thereabouts, much better than On-line Metals or the local Lowes/Home Depot. And we did get maybe 10 pounds of odds and ends for free :)