Help out rookie/less experienced teams

[Otaku]

Why yes, that DOES look familiar. =]

I'll take some higher-quality photos at Nationals and post-season, though. Post-season will also give me a chance to take the ramp off and focus on the chassis and drivetrain designs.

I'll talk to our Electrical guy and see if he can write up some tips.

By the way, how do I create a "whitepaper"?

[MrForbes]

I just made a white paper (on Center of Gravity)...it's pretty easy just go to CD-Media and click upload on the center white paper menu. I entered the text in the description box. Get your paper in good shape (complete, proofread, etc) before you upload it though...

[AdamHeard]

A few things I want to clear up;

There is nothing wrong with the kit wheels and there is no such thing as "too much traction". The kit wheels have even less traction than the IFI traction wheels that are recommended above.

High traction wheels can make turning difficult if the robot is not designed correctly. A 4 wheeled robot, with high traction wheels on all four corners, will not turn well... It probably won't even turn.


the best advice I can give to rookies on drive trains isn't to necessarily ditch the KOP chassis, but to go to a 6-wheel drive. The KOP frame is amazingly useful when you have limited resources.

A good thing for rookies with limited resources to do would be to design a 6 wheel drive (remember to lower the center wheel for turning, the KOP frame conveniently has this built in) that uses the KOP frame and an off the shelf gearbox (not banebots!). The easiest two would be the AndyMark single speed and the AndyMark 2-speed shifters.

A rookie team would get an amazing drivetrain with little advanced fabrication required, and would then be allowed to work on more ambitious things without worrying about a competitive drivetrain.

Also, unless you have the resources... don't get too ambitious with the drive train; If the drivetrain fails, it makes everything else useless as well.

[Otaku]

Originally Posted by AdamHeard

A few things I want to clear up;

There is nothing wrong with the kit wheels and there is no such thing as "too much traction". The kit wheels have even less traction than the IFI traction wheels that are recommended above.

High traction wheels can make turning difficult if the robot is not designed correctly. A 4 wheeled robot, with high traction wheels on all four corners, will not turn well... It probably won't even turn.


the best advice I can give to rookies on drive trains isn't to necessarily ditch the KOP chassis, but to go to a 6-wheel drive. The KOP frame is amazingly useful when you have limited resources.

A good thing for rookies with limited resources to do would be to design a 6 wheel drive (remember to lower the center wheel for turning, the KOP frame conveniently has this built in) that uses the KOP frame and an off the shelf gearbox (not banebots!). The easiest two would be the AndyMark single speed and the AndyMark 2-speed shifters.

A rookie team would get an amazing drivetrain with little advanced fabrication required, and would then be allowed to work on more ambitious things without worrying about a competitive drivetrain.

Also, unless you have the resources... don't get too ambitious with the drive train; If the drivetrain fails, it makes everything else useless as well.

I've found that teams have had trouble turning at a reasonable speed with KOP wheels. IFI Traction wheels seem to break traction more readily when turning, and 675 uses the Blue tread (the really tough stuff) and we haven't had problems turning.

I'm not suggesting an overly-advanced drivetrain, just a good, effecient one.

The BaneBots Gearboxes are just fine as long as you don't get the 2:1 motor adapter and you get the Hardened Carrier Plates. 675 is running 4 56mm 12:1 gearboxes (one per wheel), and the only drive issues we had was a loose PWM cable once, and re-greasing one of the gearboxes. And that was after two regionals.

Also, make sure the Carrier pins are the correct length. I've read about BaneBots shipping the short ones and robot drivetrains failing. Not good.

That all being said, I've seen bots with KOP wheels have a harder time turning than IFI Traction V2 wheeled robots.


Most of what I was writing about, however, was intended for non-Kitbots. I've already stated this, as I do not know how to build a Kitbot (This is the first year I've been really involved in building, and also the year that we've had money for raw metal for a chassis).

That being said, perhaps somebody else could make a detailed post on how to build a good Kitbot Chassis/Drivetrain?


EDIT:

Oh, and Squirrel, thanks for telling me that. After I make some revisions, I'll probably upload it.

[AdamHeard]

Originally Posted by Otaku

That all being said, I've seen bots with KOP wheels have a harder time turning than IFI Traction V2 wheeled robots.

Just want to reiterate.

The Kit wheels have a lower coefficient of friction than the IFI traction wheels. Any robot that has trouble turning with KOP wheels, would have more trouble with the IFI wheels.

The way to improve turning is in the drivetrain design (lowering the center wheel on a 6 wheel drive, etc...).

In general, it is best to use the maximum possible coefficient of friction for the wheels (I'm going to get some flack for that). Sure, high coefficient of friction wheels will make it harder to turn (compensate for that in design....) but will increase the robots traction.

I would reccomend checking out the following teams drives (in no specific order); 1345, 217, 1114, 254/968, 330, 233, 45, 190, 234, 179, 1889, 177, 121 (excellent example of KOP frame use), 116, 1717, 125 and a whole bunch more... All are good examples of 6 wheel drives (of varying complexity), which I believe to be the most resource effective drive for most FIRST applications.

Shameless plug, but 294's drive is pretty good this year.

[Otaku]

Hmm.

Well, when I get some free time (probably after Nationals), I'll whip out some (very) basic 6 wheel chassis designs involving both omniwheels and rocker chassis (but not at the same time), and perhaps a few more 4 wheel Chassis designs (or rather, more detailed ones)

Also, any and all Diagrams that I have/will make are yours to manipulate, use, or otherwise take in any fashion, as long as you don't claim them as yours. I do not require that you say that I made them, however. Just say "I got them from a buddy" or "I got them from somebody on CD" or something to that effect.

[Otaku]

Alright, well, I can't edit my original post, So I'll have to update it some other way.

Here's a new diagram I made. It's mostly self explanatory.

[wilsonmw04]

we used the KOP chassis and the 6-wheel drive(middle lowered and the KOP wheels) during our rookie year. It worked VERY well for us. We used the banebot tranny with a supporting bearing at the end of the shaft. We had zero problems with it. Turning was easy (sometimes too easy). That's something i'm having the programmers work on this summer.

Here are a few pics of the drive train before it was finished. It's rough, but you get the general idea. If you want to see it in action, check out the VCU match #50 on SOAP. We did well until be broke the arm

http://www.chiefdelphi.com/media/img...426e384c_l.jpg

http://www.chiefdelphi.com/media/img...d32e6bc4_l.jpg

[Otaku]

Hmm. KOP Wheels + Rocker Chassis... not something I had thought of before.

Kudos to you and your team for coming up with that.

I'm thinking I might just go ahead and find some graph paper and draw up the other diagrams then scan them -- it'd probably be less legible that way (photoshop could fix that) but more precise.

[MrForbes]

Originally Posted by Otaku

Hmm. KOP Wheels + Rocker Chassis... not something I had thought of before.

Kudos to you and your team for coming up with that.

that's what comes in the kit....although you need to get two more wheels...so it's not something secret

[Otaku]

Originally Posted by squirrel

that's what comes in the kit....although you need to get two more wheels...so it's not something secret

Remember, I've stated that I've not built a KOP Chassis before. '05 was 675's last year of doing so (for Triple Play). For both Aim High '06 and this year, we've taken aluminium stock (3x0.25 in) and turned it into a chassis.

[MrForbes]

We used fiberglass for the 1726 chassis last year and this year. But we did spend some time looking at the kit chassis, and noticed the lowered center holes.

The fiberglass works very well as a chassis material...it's tough, easy to work with if you don't have a machine shop, and the shapes we use work well for robots. The side rails which hold the wheels are I beams turned on their side, the ends are channel, and it's all held together with bolted on aluminum angles (similar to those you've shown above). We learned about this material from our mentor team 842. We use a different frame layout than they do, though.

[Smaug]

baker post our design that you were given today it is a exact size to our bot. one of our teams drew it so each of our groups can have a copy. it is a extremely simple design. through out the comp. we were at there were quite a bit of teams who like our drive train and chassis cause it was so simple and it is an awesome test plat form.

[1359th Scalawag]

Our official rookie year was 2004, but because 90% of our team were newcomers and the rest had senioritis, 2006 became our unofficial rookie year. Our drivetrain was built badly. Because of how we built it, we had to slow it down or it wouldn't turn. At the Portland Regional, we had the slowest robot on the feild but by the end of qualifying we somehow got 1st seed. Our robot was mostly made to do 3 things: score autonomously, push, and get on the ramp. First thing into finals, our drive train finally caught up to us and our opponents didn't let us do any of those things.

What i'm trying to say is that a "bad"(slow) drivetrain can have upsides such as accuracy in autonomous or torque, but any good team can and will take advantage of it.

(you can't push something you can't catch)

[Tim Delles]

Originally Posted by AdamHeard

A few things I want to clear up;

There is nothing wrong with the kit wheels and there is no such thing as "too much traction". The kit wheels have even less traction than the IFI traction wheels that are recommended above.

Just want to clear this up.

You can have to much traction (depending on the gearing of your drive train) All teams should (after the drive train is complete) should bring the robot up to proper wieght (using paper wieghts or what not to load down the robot) and then push against the wall. If your wheels begin to slip you are good. However if your wheels do not move, thus forceing the motors to stall a course of action must be taken to keep the motors from stalling.

There are a number of ways, the most common is reducing the coefficent of friction of the wheels.