Help out rookie/less experienced teams
 

Alright. I've seen some people ask how to make drivetrains, how to organize electronics, etc, so I think the CD community as a whole should help them out.

First off:

Building a Non-Kitbot chassis:

To build a very robust, non-kitbot chassis, you want the outside of the frame to be the largest part of your robot, then you want to make sure that there are plenty of supports and good fasteners. 675 uses 3/8ths inch Grade 8 bolts with a shoulder on them, and a washer on each side of the bolt. Gloria Machina, 675's bot, is layed out like this.



The thin black lines are vertically-mounted peices of quarter-inch thick, 3 inch tall aluminium.
The maroon rectangles are the wheels.
The dark blue strips are the same type of aluminium, but bolted on top of our gearboxes to support the chassis and gearboxes.
The thick black strips are some other sort of material, and hold the stump of our arm, along with our ramp bracket and battery.

Not to scale.



Building a good Drivetrain:

First off, unless you want insane traction and a hard time turning with tank drive, steer clear of the KOP wheels. They're very grippy and to lose traction, teams have had to cover them in plastic or zipties.

There are several different kinds of drivetrains you can do. You can do a direct-drive system with all wheels powered by their own motor (4 or 6 wheels works best for this), a chain-drive system with all wheels powered with their own motor/gearbox (again, 4-6 wheels), chain-drive for each side (2 motors generally, 4/6 wheels total), or some other interesting systems (like a 6-CIM drive system, or a 12-wheel system, not recommended for rookie or less experienced teams).

There are also several different types of wheels. Traction, Omniwheel, and Mecanum are the three most well known. Traction wheels have a grippy tread that gives, as the name implies, traction. The design on the tread can be all sorts of things, from a crisscross pattern, to a pseudo-car-tire design, to the kind of stuff that comes on IFI Traction wheels.

IFI Traction V2 wheels:



Not the two different types of tread. The kind on the left is called "Roughtop", and the type on the right is called "wedge".


Omnidrive wheels are cool. They are normal wheels in the sense that they are round and give you traction, but only forward and backwards. A common design for omniwheel useage is traction wheels in the center of a 6-wheel chassis, and omniwheels at the corners. This improves turning speed greatly over an all-traction wheel chassis.

AndyMark Omnidrive Wheels, 6in Diameter:



Mecanum wheels are probably the coolest, however. The wheel design is similar to Omnidrive, however different in such a manner that the robot using them can move in any direction and rotate easily, allowing it to slide around much like a hockey puck. There is a special way of mounting them, however, and that is so that the 4 wheels form an X when looked at from the top down.

Mecanum Wheel, 8in diameter:


Notice the staggered rollers.



Alright, well, that's about all I can post about, as that's about all I know how to do. If anybody who has experience with Pneumatics or Electronics would like to speak up, please do.


Thanks to AndyMark.biz and InnovationFIRST.com for the pictures, and making good prodoucts.


EDIT:

And to anybody who's interested, I hope to find pictures or acquire pictures of our robot's chassis and drivetrain. I know that a simple MSPaint diagram of a bot isn't as helpful as one might make it out to be, but hey, it's a start.

I also might make more diagrams later.

Re: Help out rookie/less experienced teams
 

Here is Team 1345's 2007 Chassis. Kids wanted to have a low ground clearence chassis and 6wd. We used 4.5"x4.5" box aluminum tubes for 2 modules (on the side).

In this case, we were inspired by team 1114's prototype chassis. All we needed was some 4.5"x4.5"s. It is 37 inches long and 27 inches wide. The C channels you see are 4.5"x4.5" cut in half with a notch. There are L brackets that connect the C channels to the modules. One side of the L (the side that is connected to the module) is riveted on with .25" steel rivets, the other side is bolted on with quarter inch bolts. We ran a single #35 chain through each module and used a vertical tensioning system. The final product weighed 53 pounds (including electronics).

Here are some links to pictures of the modules and the chassis. If you have any questions, or would like to discuss, feel free to send me a message.

http://www.flickr.com/photos/7634503@N04/444303299/
http://www.flickr.com/photos/7634503@N04/444303297/
http://www.flickr.com/photos/7634503@N04/444303281/
http://www.flickr.com/photos/7634503@N04/444303255/ (last minute cheeseholes).

Re: Help out rookie/less experienced teams
 

does this look familiar? from Thursday morning at Davis....

Re: Help out rookie/less experienced teams
 

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"?

Re: Help out rookie/less experienced teams
 

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...

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

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

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

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

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

wow what a thread to find! Being on a less experienced team myself and being one of the few that wish to prototype sweet design, we have decided to try a crab drive (to keep up with you vetren-like). I don't mean to be rude or anything and I understand this is a thread to posted ideas, not ask questions but is there any chance someone could ethier post or PM me on the simpliest way to start a crab drive. And before you ask I do understand it is complicated to do, thats why I am starting now :D

Re: Help out rookie/less experienced teams
 

Feel free to ask them to post it here!

This isn't just a thread for more experienced teams to help out less experienced ones, but a place where less experienced teams can come to ask for help. Remember, we're all gracious professionals here.


That being said, I don't know anything about Crab or Swerve drive. Sorry.

EDIT:

Oh, but I did find this article on Wiki Books...

http://en.wikibooks.org/wiki/Robotic...hysical_Design


Enjoy. =]

Re: Help out rookie/less experienced teams
 

Yup, you're right.

...Sometimes you get so focused on something (traction affecting turning), you forget basic facts...

sorry about that.

Re: Help out rookie/less experienced teams
 

...Woah. Fiberglass?

I'll have to mess around with that after I get a job. I'd love to see it's potential.

Re: Help out rookie/less experienced teams
 

Thanks for that! :D I have done some research on crab drives and thats why I want to make one! unfortnatly I'm not sure how to go about starting said crab drive so any team who has done a crab drive before, it would be great to know how you started lol!

Re: Help out rookie/less experienced teams
 

71, 111, 114, 118, 16, 469 and 1625 have all done crabs.

71, 111, and 118 have been doing them for years, so I would talk to them.

Re: Help out rookie/less experienced teams
 

cool thanks a lot. all I need now is there phone number! :p

Re: Help out rookie/less experienced teams
 

Click "Members" at the orange bar here on CD (right next to "User CP"). Click "Search Members"

Insert Team Number.

That should help some.

Re: Help out rookie/less experienced teams
 

to quote some famous FIRST personalities:

The three most important things on a FIRST robot are:

1. Drive
2. Drive
3. Drive

Spend time getting it right and making it faster than you really think you need - you won't regret the decision.

The best way to learn is to wander around at competitions and see what other teams are doing and what works and ask them how they do it.
Also, try to go to some off season forums or the forums at the Championships.

The last bit of advice - build prototypes and experiment, but don't decide in December what drive you want to use. Wait until the game is announced, decide how you want to play the game, and then decide what drive is best for that.

For example (these are general comments only - please don't blast me),

a swerve or mechanum drive lets you get all around the field quickly, but they don't push / play defense well for the very reason they work well getting around the field.

a tank drive is quick to turn and great for pushing and defending, but not very efficient so they consume a lot of battery power

a four wheel drive is easy, but can be tough to turn with traction wheels - or easy to push around with the wheelchair wheels or other rollers

a six wheel drive is easy to turn and can be a good defensive drive, but uses a lot of weight in sprockets and chain.

Bottom line, there is no "perfect" drive and each game strategy lends itself better to one particular type. several drive types have been successful this year - it depends on how the team wants to play the game.

Re: Help out rookie/less experienced teams
 

Team 852 has been with FIRST for several years, so maybe some aspects of its robot design can be used by rookies:

THE FRAME:
Our frame is made out of 80/20. This is amazing stuff because it can be bought in very large stock lengths and cut down to size, and there are plenty of different connectors one can buy that make it easy to build a very versatile chassis.

The bottom plate is simply 1/8in aluminum plate, cut out and attached to t-bolts in the 80/20. This allows the electronics people to do whatever they want with the bottom of the robot (drill holes and bolt things down, for example).

The plates we use to cover the sides of the robot are made out of Lexan. It is soft enough not to crack in the heat of a FIRST battle, but hard enough to protect your electronics.

THE DRIVE TRAIN:
This year, we changed our drive train a little bit. We used four CIM motors in our drive train, two per side. Each CIM has a small gear on its axle. Each pair meshes with a larger gear, which has two sprockets on the same shaft. Those two sprockets attach via chain and sprocket to the wheels adjacent to the gearbox. Then, since we have 6 wheels, the wheels in back of the gearbox attach via chain and sprocket to the rear wheels.

Our front four wheels are traction wheels. The rear two wheels are omniwheels. The 6-wheel drive train allowed us to put the traction wheels closer together, which allowed for better turning. The omniwheels keep us stable and allow us to pack our arm away (by making more room in the back of the bot).


GAME PLAY DEVICES:
You probably already know this, but whatever you do, keep it simple. It's easier to diagnose and fix problems that way, and you might win the GM industrial design award. Whenever you design a component, come back to it a day later and ask yourself the question: can I make this device in fewer parts? Some of the best engineers can turn a 5-part device into a single masterpiece.

If you got this far in my extremely long post, congratulations (I'm done).

Good luck rooks, I have respect for you guys.

Re: Help out rookie/less experienced teams
 

If you can't drive, you can't play. Well, you can, but the last time non-driving robots could really play was 2001, and those spent the entire match on a stretcher. This year, even pure ramp/lift robots need drives to clear out their home zone, and that's assuming that they don't play defense.

If your drive is lousy, your arm will not be very effective, even if it is the best arm in the competition! How far would teams 234, 254, 1114, 67, 111, 330, 118, 45, and 217 have gotten without drivetrains? Not very far, I'll tell you that.

Prototyping is good. In 2005 we prototyped a mecanum drive. After analysis, we decided to go with a six-wheel dropped center. Why? The mecanum wasn't the best way to go for us. We felt it had disadvantages that were unacceptable to us. But in recent years, mecanums have become increaingly common. I'm not sure if that's because teams are deciding that they need them, advantages outweigh disadvantages, or just the cool factor. I also don't really care, because that's the team's choice.

Bingo. But in addition to the drivetrain capabilities, what can your driver handle? I mean, if the driver can't control the drive you give him/her, then you just wasted a lot of time. Does your team know how to use the drive you want effectively? (I've seen examples in recent years of good drives not being used to their full potential or not being used "right" for the game.) Do you want to innovate (e.g. 703's 14-wheel or 118's V-6)? If you can answer these questions, you are in a much better position than someone who can't. There is no one ideal drive solution, just as there is no one ideal any-other-aspect-of-robot-design solution.

Re: Help out rookie/less experienced teams
 

Just to fix a generalization, swerve drives can be very defensive like we were this year. One match we held Wildstang to one tube and in Quarterfinals we held the Beast to one tube in four matches. Mecanums are just a little different.


If anybody wants help with swerve drive stuff contact Gear from 1625 he is my brother and designer of our ever so amazing swerve drive this year.

Re: Help out rookie/less experienced teams
 

thaats cool I may get in contact with this "Gear" I would really like to make a swerve / crab drive because our entire team seems to think in that sort of manner (that being to deak around people and not get caught in shoving matches)

Re: Help out rookie/less experienced teams
 

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.

Re: Help out rookie/less experienced teams
 

I've yet to get around to putting it into Sketchup or anything. Blake left some dimensions missing (no big deal, it's a 1:1 blueprint after all), so I'll find my tape measure then mark those in.

That, and I'm not used to CADding things, so chill out a little bit. It'll get done. Maybe not today, but it will.

Re: Help out rookie/less experienced teams
 

Doodeelaadoo...

Click it. It's a thumbnail.


I'm still working on it, but I suggest that if you're going to want to maniuplate it and view it, you'll want Google sketchup. It's free (well, the free version is).

This is just a teaser, btw. I'll upload the .sku (or whatever the filetype is) when I finish.

Re: Help out rookie/less experienced teams
 

Talk to whoever does firstbase on your team and download a 30 day inventor trial.

that will give you plenty of time to learn inventor well enough to make your base. (2-3 hrs is all it should take)

Re: Help out rookie/less experienced teams
 

Eh.

I'm on the Manufacturing team, and I don't really have any desire to become a good CADder. Just well enough to do some simple stuff on free platforms.

Besides, I odn't even know if my team has an animator. D=

I have the basic frame CADded out. I plan on uploading the .skb once I get to the computer it's actually on.

Re: Help out rookie/less experienced teams
 

For between the side rails, instead of one huge piece of angle, use u channel or a cut piece of box tubing. This way for the inner piece you have support from both sides. Or just weld 2 pieces of inderstrial angle, so that you have the corner support. Or tig wil the inside corners of the channel.

Also I don't know if you plan on including it or if you even care, but for attaching the angle, just make tapped holes this way you dont need nuts. And 1/4-20 screws should suffice. If you do a 2 pattern, it should be fine:Doing a 3 hole pattern should stop rocking if you only have the support on on side:-John

Re: Help out rookie/less experienced teams
 

The bolts are all in the 3-bolt pattern you showed.


What I am showing is 675's chassis design for this year -- sans fasteners (if people really want to replicate it, they can improvise).


We have supports for the middle, but we don't use them. The strength given by the wheel axles and driveshafts (with bearing plates on the outside of the chassis securly fastened) is more than sufficient.


Trust me... It's a tested platform. This chassis design has seen 3 competitions without failure (and it's dished out and received some good hits).

Re: Help out rookie/less experienced teams
 

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)

Re: Help out rookie/less experienced teams
 

I figured that I would bump this thread, with all the new teams that are probably going to be joining FIRST this year. Who knows, maybe our (so far) combined knowledge will do some good! If anybody else wants to add to what's already here, don't hesitate.

Re: Help out rookie/less experienced teams
 

although.. we may not be an experienced team and I may not be experienced at autodesk I did over the summer make some general frames for basic wheel deisgns (4 wheel drive, omni drive etc) so I will try to post them when I get home (I'm at school right now lol)

Re: Help out rookie/less experienced teams
 

Two people suggested it, so I just edited the first post a bit and uploaded it.

The whitepaper, that is. Go ahead and check it out.

http://www.chiefdelphi.com/media/papers/2023

Re: Help out rookie/less experienced teams
 

I think you should add a few sections;

Gearboxes/Transmissions. List the common off the shelf gearboxes along with the pros and cons.

Also, maybe suggest different frame materials. Plate isn't the best material to use on it's own, and may be difficult to get all the dimensions required. Recommend 80/20 extrusion and maybe even aluminum extrusion.

But, if this truly is for rookies, I would stress that they stick with the KOP frame. The current iteration of the KOP frame is pretty awesome and easy to work with. What will make a bigger impact on rookies is using better gearboxes/wheels.

Re: Help out rookie/less experienced teams
 

Hi I'm a new student in a robotics class in Arroyo Grande and i'm rather new to robotics but the team is thinking of possibly using the BaneBot 56mm Planetary Gearbox and I was wondering if there are any bugs with this system or problems that we might need to be aware of currently. I saw that there were some bugs last year though I've been informaed those have been resolved, are any of these bugs still present or have any new ones arose? The BaneBot aside, is there a better gearbox that anyone knows about that's possibly cheaper or at least under 100$? If someone could message me with details (I assume there's a messaging system on this site) it would be much appriciated. I'll also be looking back to this thread regularly to check up on it, thank you.

Re: Help out rookie/less experienced teams
 

The AndyMark single speed is far superior to the banebots in performance/reliability (strength safety factor), weight, cost, efficiency etc.... It can also take both a big and small CIM, or two small CIMs with no modifications.

The banebots will work if used right, but there are far better solutions.

Re: Help out rookie/less experienced teams
 

Just as a note, the AM Gearbox has a smidge more gear reduction than the standard BaneBots 56mm gearbox (12.75:1 versus 12:1). You'll have to run the math yourself to see how it affects your application.

Re: Help out rookie/less experienced teams
 

Ok then thanks for the information I'll look into the AM gearbox, it looks pretty nice. Now I have a new question, what wheel speed is the best? What are teams going with and what do you guys, personally, think is the optimal wheel speed to use?

Re: Help out rookie/less experienced teams
 

It all depends on what you need it for. 675 uses 12:1 gearboxes and only one team has honestly pushed us. We're a defensive 'bot, however. If you want offence, you'll need to get a higher speed.

Re: Help out rookie/less experienced teams
 

Well what is your wheel speed with a 12:1 gearbox?

Re: Help out rookie/less experienced teams
 

I don't honestly know -- but it's not the fastest in the world. It's actually quite slow.

I'll find the speed later, assuming the bot's running.

Re: Help out rookie/less experienced teams
 

The answer: It varies according to strategy and the games.

As I recall, 1618's drive system this year was geared to around 12 feet per second in high gear and around five in low--I can't confirm those numbers, but they sound about right. Most folks agree that 12 is about the upper limit of usefulness on an FRC field, but we wanted a fast scorer. (We actually wound up with a fast defender, but often the two concepts are intertwined.)

Re: Help out rookie/less experienced teams
 

Ok then thanks for the info, and, sorry for the newbie question, but how do you access the white papers on chief delphi?

Re: Help out rookie/less experienced teams
 

Go to CD-Media (up at the top) and on the righthand side should be the whitepapers section.