Effective Drive Base
 

What are everyone's opinions on what could be an effective drive base for this year and why do you think so?

I had a thought of a swerve drive with treaded wheels. The treaded wheels could provide the necessary traction to move over the BUMPS but the swerve drive provides extreme mobility.

Re: Effective Drive Base
 

I agree. Crab (swerve) drives will most definitely be effective this year.

Mecanum drives will also be effective, because they are both able to get up the bumps and move with extreme maneuverability and moderate speed. The one downfall is that they have to be dead perpendicular to the ramp, or they will just drive sideways along it.

I think the best drive trains will be those built specifically for this game, such as a drive like this one:
http://www.youtube.com/watch?v=xby0SOphLUg

Re: Effective Drive Base
 

I keep thinking tank treads would be a good idea. The bumps would be no problem whatsoever.

Re: Effective Drive Base
 

I tried this year to think about not using my favourite drivetrain (our linkage). But the more and more I thought about it, the more and more I think that our system would work out well. Basically a swerve system with a little less mobilty and less complexity should be well and capable of climbing bumps in at least one or both set ups.

Re: Effective Drive Base
 

a graduated member of my team suggested using belts that have been flipped inside out to use as tank treds

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Some things to consider if you want a swerve drive. Will it high center? How will it climb? Can it take the shock load of falling off the bump? Do you have the resources to ensure this works?

And unfortunately, Simswerve looks somewhat impossible this year. :( Design idea number 40 billion killed by bumpers.

Re: Effective Drive Base
 

I'd like to encourage teams to draw lots of diagrams, mock up rolling chassis, and think about the assumptions you are making before designing a "drive base".

Basics
4WD skid - simple, effective, stable climber. If it's designed to stand a chance in a pushing contest, it won't be very maneuverable.
6WD skid / tank tread - a bit heavier, more moving parts, NOT a very stable climber, much more maneuverable, still good at pushing (Usually the best "compromise" chassis, but not this year).
Omni / Holonomic - very versatile, simple, maneuverable, but you're on roller skates, and can't climb well (or at all).
Crab / Swerve - similar to above but with superior traction, superior handling, more complex, many moving parts, not likely to be a good climber. Does not (usually) rotate the chassis efficiently which could lead to more complex (multi-sided) game mechanisms.

I think the best drive systems will be some sort of hybrid between two of the basics. I would NOT use a tread or a crab to climb... good luck to those who try it! (And do you really need to climb anyway?) If you do, you might want to bring a big tool box to the competitions!

Enjoy!

Re: Effective Drive Base
 

Why would a tank tread design do poorly while climbing those bumps? I've heard the exact opposite: that tanks are great at it, and that they *almost* never break. I'm on an iPhone, so I can't link to YouTube, but search up the Ripsaw MS1 made by Howe and Howe Tech (yeah, the ones from discovery channel).

Re: Effective Drive Base
 

Drive system mobility and ball control are going to be the two most important aspects of robots this year, and likely the two most over looked in the design process.

Re: Effective Drive Base
 

The advice about checking assumptions and making design drawings and models is excellent, and there is a good list of drive concepts to consider here, as well.

However I would strongly encourage teams to check the assumptions made in the "basics" section of this post for themselves by looking at successful ramp climbers from the Aim High game, and step climbers from the First Frenzy game. Some of what is listed there, although no doubt well-intentioned, doesn't reflect my personal observations of drive train abilities over the past six years.

Jason

Re: Effective Drive Base
 

You beat me to this post.

Never rule out unconventional drivetrains that would seem like a waste on a flat field either. Maybe it's not so good to limit your options to the 5 drivetrains on that list. I don't know.

I would completely rule out swerve drive if you've never built one before. Knowing your limits is key.

Re: Effective Drive Base
 

What is the reasoning behind not using a crab to climb?

Re: Effective Drive Base
 

Your reasoning behind many of these suggestions is very flawed. Your references to 6wd robots that fail to climb the ramp are inaccurate generalizations. I have yet to see a ramp that a well designed and well thought out 6wd with very good CG cannot overcome.

Also, this may be the year we see a 6 wheel swerve system. Although I would never doubt someone like WildStang designing a 4 wheel system that can overcome the bump this year.

Re: Effective Drive Base
 

Tracks. Finally we have a year where tracks are useful again! As for the weight concern, how does 18lbs for simple track modules sound? 38 for simple modules with gearboxes and motors?

I like this year.

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When I first started analyzing the game I figured that a basic 6 WD robot with 8" wheels could easily climb the bumps. In this configuration there is no bottoming out issues, and the CG can be kept quite low.

However, we discovered a critical flaw when we tested this.

When a 6 WD robot climbs a ramp*, the center wheel acts as a pivot as the robot climbs over the crest. This results in half the robot being lifted into the air :eek: Highly unstable!

Take a look at the demo bots in the game vid (The non-animated ones of course!). They all have FOUR wheels. This is a much more stable configuration b/c all four wheels remain in contact as the robot climbs. There are no sudden rocking movements forwards or back.

Of course, as Dean himself pointed out, 4 WD robots don't turn very well... :)

*or a tracked drive

Re: Effective Drive Base
 

False. There is indeed a 6 wheeled robot.

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Checking your assumptions at the door is definitely important. For instance, the Aim High ramp was only 30 degrees to a nice flat with a wall behind it. The Bump (caps make it scarier) is 45 degrees up, to a flat with a 45 degree faceplant just waiting for the unwary or timid driver.

Before picking a drivetrain, you should consider how it's going to rest on the slope, what that implies for your CoM, and what a sudden stop will do to you on the down slope. Or a sudden start on the upslope. You may want to mock up a bump and throw a drivetrain at it to see the effects momentum can have on your robot. I can tell you that a robot with more than 3 contact points per side should worry about having a CoM higher than 12". The case for a 6 wheeler is going to depend on the wheel sizes and separations, though it should be somewhat better.

EDIT: As Martin Taylor pointed out, numerous contact points on a side means you significantly raise your CoM before your robot tips onto the flat of the bump. Which would be survivable if the flat was, say, 24" long. But a 12" flat isn't a large landing pad. If you have a CoM over 12" in the center of your bot, then once you tip over to the flat of the bump, your CoM is already past the far side of the flat. Which means you just keep tipping forwards. Which means you're going to faceplant on the far side of the bump. Moving your CoM rearward helps, but not as much as you'd think. Accelerating off the backside of the bump will probably spare you the faceplant at the price of an even rougher landing.

Re: Effective Drive Base
 

Something I don't think has been mentioned yet, but is important:

At the kickoff, after the Game Animation, Dean and Woodie demonstrated the difference between using the "slick" wheels and "stick" wheels when it came to the vision tracking.

If we use the "slick" wheels, the robot will have an easy time sliding around lining up with the vision target. However, it pretty much can't make it over the bump (gets stuck at the top)

If we use "stick" wheels, we can make it right over the bump, but it can't move sideways to line up with the target.


So if we go with treads, what kind of sideways motion is there to be expected? Sure, treads can go right up and over the bump, but you'd have to resort to tank-drive driving to line up with anything. Not exactly an effective solution, at least in my mind.

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I've had no problem with tank-drive steering in regards to vision tracking in 2006 or 2007.

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I just wanted to point out that the actual grade of the bump is approximately 38.7 degrees (or something to that effect) using simple trigonometry based on the height and width provided by FIRST.

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We designed these articulating drive pods back in 2005 and have been waiting for a game like this to use them.

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In response to several comments and questions regarding my reasoning for my dislike for 6WD and tread designs as a climber... Understand I'm not suggesting that they cannot climb. Of coarse they both can be extremely effective on inclines. But their MAIN advantages are massive weight distribution on unstable surfaces (tanks with treads in sand) and maintaining contact with extremely unpredictable terrain (rovers) when used with a suspension system.

So, my original post was under the heading "Basics"... and I was not considering anything with a suspension a basic design. In a basic (kit-bot) configuration the 6WD and tread option give you the same see-saw effect as you crest the peak of this games "bump". Not exactly the picture of stability. Toss in a reasonably high CG (needed for clearance in a static system) and the likelihood that your weight distribution will be biased in one direction to some extent, and well, I'm not interested. Two points in contact are by definition more stable…

We tested this out this evening as well (on a kitbot rolling chassis) and that's all I needed to see! Throw it together and see for yourself. Good luck.

Re: Effective Drive Base
 

(stares with amazement)
...I...WANT...THOSE

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I'd like to thank everyone for all of their input! :D

I was hoping this thread would generate a good place for a few people to reference and learn. I've learned a lot from everyone's posts. Thanks all =]

Re: Effective Drive Base
 

Nicely put... I guess I was not as clear. And with all due respect to those that posted earlier, I've been doing this a while too, and played the games you referenced... and climbed with ease each time without a tread and less than 5 wheels! Very stable! Just trying to simplify a problem that’s easy to make unnecessarily complex.

Re: Effective Drive Base
 

Currently, as a team, we're trying to decide between using mechs or a swerve system. I happen to be privy towards a swerve system, but it would be our first year using it, so a lot of people are nervous. I think that swerve would give better traction than mechs as well as the ability to have a multi-direction robot, but there are arguments against swerve as well (mainly how complicated it is). I guess I'm just a teensy bit biased :rolleyes:

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i think some fast robots are going to be surprised to see how much air they can get flying over that bump, such instances will make for some cool pictures for sure, structural integrity of the chassis not withstanding.

Re: Effective Drive Base
 

that is a concern my team will have when we have the drive base argument. we built our first mechanum base this year in off season. so we are fairly new to exotic drive systems.

a big factor with a swerve drive though is that is a lot of weight added to your robot. the more weight you have on the robot the riskier it will be to drive over the bumps.

im really interested to see how teams approach this challenge.

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For the sake of discussion, I'm attaching a picture that shows an 8WD system going over the bump.

Re: Effective Drive Base
 

Thanks.

We're debating between a 6wd with 8" wheels or an 8wd with 6" wheels. I'm personally leaning towards the 8wd.
False.

This weight is at the bottom of your robot, low to the floor. This amounts to a low center of gravity as long as your arm or hanger is also lowered while driving over a bump. Low CG= easier movement over the bump.

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Would four wheel drive be effective, would it be able to make it over the bumps, how would the turning be?

Re: Effective Drive Base
 

can someone explain to me how the serve/crab drive will not be an effective climber? I don't understand how the fact that a swerve is complected would matter when climbing. Climbing is all about traction and a swerve with the right wheels would have the same traction as other systems.

Re: Effective Drive Base
 

It depends on how you build it. If you make a typical swerve with small wheels, then have fun going through the tunnel. But if you use larger wheels and put them directly in the corner of your robot without any frame to inhibit contact between the wheels and bumps, then I would say that you have a very good chance of getting over the bumps.

Mecanum would seem like a very poor choice this year, especially with such a small area to get through the tunnel. But some will do it and someone will do a great job with it. There always is at least one good team with mecanum!

Re: Effective Drive Base
 

The kit bot rolls over the bump with ease because of the large wheels, it does not bottom out on the top of the bump. However, turning with 4wd is a pain. The robot "jumps" as it counters the friction while turning with skid steer.

Re: Effective Drive Base
 

Sir, you should perhaps examine the official field drawings for the bumps that will be on the field. The chamfer on the rib that supports the bump happens to be 10 1/4 high and 10 1/4 wide. Simple trigonometry tells me that the bumps FIRST is going to be building will be at an angle of 45 degrees.

Re: Effective Drive Base
 

Madison,

You should put a CG marker on your sims, things get more interesting when you start looking at where your robot starts tipping, and where you end up after you tip.

Re: Effective Drive Base
 

Thanks, Kevin... before I read your post I was thinking... "NOOoooo... we didn't screw up when we built 45 degree angle bumps... did we?", and actually went and re-downloaded the drawings to check.

I've attached the relevant image here.

45 degrees is correct... and wow... it sure looks scarier in person when you see an actual bump first hand than it does when you look at the drawings.

On a seperate note, a student drew up some drawings very much like Madison's this afternoon... and while I don't think ground clearance will be an issue, so long as teams plan for it, CoG is certainly going to be.

After watching teams like 254 climb the ramp, drive sideways across the ramp, basically jump off the ramp and show off what a low CoG can do in Aim High, however, I'm pretty convinced that we can build an even lower CoG for this game. In fact, I wouldn't be surprised if some of those old Aim High robots have already made it over the bump....

I think the really maneuverable robots this year will not only be able to "get air" off the ramp, but to climb a flight of stairs.

Jason

Edit: And as for making a 4wd robot with big wheels turn... AndyMark might be able to help out a bit http://www.andymark.biz/am-0104.html

Re: Effective Drive Base
 

Madison's 8wd picture is looking pretty good...and similar to what we came up with when comparing 6 and 8 wd bots going over the bump.

You can get the CG way lower with 8wd than you can with a 4wd bot that clears the bumps. And playing with raised end wheels does neat things to steering ability.

Re: Effective Drive Base
 

Actually, the kitbot does not roll over the bump with "ease". The tough-boxes bottom out on the top of the bump, and unless you are moving with speed you will get stuck there.

I’ve confirmed this both in CAD and testing.

Of course you can mount the T-boxes on top of the frame, and solve this problem.

Interesting design feature AM... :rolleyes:

Re: Effective Drive Base
 

That's how we have them set up. I figured teams would have figured that out when trying out the kit base. Also, the kit base's "slick wheels" help a bit with turning the 4wd.

We are most likely going with 8 with the front sets raised slightly, I think it will be a common design among experienced teams.

Re: Effective Drive Base
 

Given that my model is symmetrical in two planes, the CG is right in the middle. The robot will obviously behave differently going over the bump if the CG is very far forward or aft, but my model isn't complete enough to capture that yet.

8WD may send the robot "higher" on its way up the bump, but the same behavior that causes that also prevents the end of the robot from falling quite as far as it might on a 6WD system. I am under no illusion that the robot will ever stop successfully on the flat top of the bump and understand that it's going to dive hard into the ground on its way down in all cases, though.

It's also possible to implement 6 or 8WD systems wherein the wheels are not equidistant from one another and see some altered behavior from that. In 8WD, moving the center wheels closer makes the system begin to approximate a 6WD frame -- so it won't ride up as high while climbing, but falls correspondingly further on the trip down. It's all about trade offs, obviously, but I am more concerned with minimizing the force of the giant thud that'll happen on the way down than I am with tipping to 45* on the way up.

Re: Effective Drive Base
 

Half-tracks, anyone? Short tank treads in the back, powered omnis up front. Power to push & climb with the addition of maneuverability...;)

Re: Effective Drive Base
 

Try mounting the transmissions on top of the chassis.

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Could 4 wheel crab steering make it over the bump?
Our team is looking into either that or standard 4 wheel skid steering.

Re: Effective Drive Base
 

I would love to see a version of 2004-71 style swerve.

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Is this possible with the BUMPER ZONE rules as they are? Would articulating your wheels change your BUMPER height?

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This is the reason I ruled it out as a possible design. Bumpers ruin everything.

Re: Effective Drive Base
 

We need to remember that the bumper zone is elevated this year, 10-16 inches above the floor when on a flat surface and may not be articulated.
8.2 DEFINITIONS
BUMPERS – Bumper assemblies designed to attach to the exterior of the ROBOT within the BUMPER ZONE, and constructed as specified in Rule <R07>. BUMPERS are excluded from the weight and volume calculations specified in Rule <R10>.

BUMPER ZONE – the volume contained between two virtual horizontal planes, ten inches above the floor and sixteen inches above the floor.

<R07>
A. BUMPERS must provide complete protection of the entire FRAME PERIMETER of the ROBOT (i.e. BUMPERS must wrap entirely around the ROBOT). The BUMPERS must be located entirely within the BUMPER ZONE when the ROBOT is standing normally on a flat floor, and must remain there (i.e. the BUMPERS must not be articulated or designed to move outside of the BUMPER ZONE).

If one uses 6 inch wheels, then the drive assembly would need to be a good distance behind the frame perimeter for any bumper to interfere with climbing. (The top of the bump is 12 inches high but also 12 inches set back from the base) This does not appear to rule out any type of drive system that would take into account the shape and height of the bump. As to whether a crab drive would succeed on the bump over a different drive system is up to the team to prototype and then make a decision. As is discussed in several other places, high center of gravity seems to be the more important issue if choosing to climb the bump. Considering all of the factors summed together, it appears to be a considerable challenge to design a robot that both climbs over the bump or drives through the tunnel.

Re: Effective Drive Base
 

My team has been doing some testing to see which drivetrain handles the bump best when driving over it at an angle (we assume that we won't be able to hit the bump perfectly straight every time). We have prototyped a few ideas, including 8WD with raised end wheels. Has anyone else considered how their drivetrain will work when driving over the bump at an angle (or if their robot gets hit when driving over the bump)?

Re: Effective Drive Base
 

Heres my problem with the rule...when your robot negotiates the bumps, or hangs from the bar, your bumpers will no longer be in the bumper zone. Thus aren't you violating R07?

Re: Effective Drive Base
 

I think that treads provide too high a probability of falling off the bot on turns. I think the grip wheels that came with the kit are the best option

Re: Effective Drive Base
 

The BUMPERS must be located entirely within the BUMPER ZONE when the ROBOT is standing normally on a flat floor, and must remain there (i.e. the BUMPERS must not be articulated or designed to move outside of the BUMPER ZONE).

I think this is the effective part of the rule.

Re: Effective Drive Base
 

I agree...I think that is a very important part of the rule. The part I don't like is "the BUMPERS must not be articulated or designed to move outside the BUMPER ZONE". To me this means that you shouldn't design your robot or mechanism on your robot such that the bumpers could move.

Re: Effective Drive Base
 

I would research the design of a proper tread system further before simply ruling it out. A proper tread system won't fall off on the turns, only a poorly designed one will.

Re: Effective Drive Base
 

How about discussing the different drive base styles relative to a strategy? It would seem that what works well for a "goalie" robot may not work well for a "midfield" or "forward" robot.

For a goalie, an omni-drive may make the most sense. You'd never have to traverse a bump and could shuttle from side to side with ease, clearing out balls as they came into the zone. As a mid-fielder a more powerful system may be better. I have a feeling that in the mid-field zone there will be lots of contact and jockeying for position beneath the ball returns (almost like boxing out in basketball after a free throw). As a forward, you'll want high accuracy and agility, but probably also want the ability to return to the midfield zone and help out if necessary.

Sorry for all the sports references, but it seems like that is the kind of teamwork they're nudging us toward this year. Specializing at doing a portion of the tasks particularly well will likely lead to an alliance selection, and if all goes well your alliance will do a good job of putting together a team of goalie, midfielder, and forward (all of which will, I'd imagine, look fairly different from one another).

Thoughts?

Re: Effective Drive Base
 

I agree with you. Teams would have to design their robots based on where they want to play at, either front, mid or far back. It seems almost impossible and time is very limited to make a robot that is able to do EVERYTHING. Strong specialization in a particular zone is important.

Re: Effective Drive Base
 

so what would be the disadvantage of 6 in wheels beside the obvious ground clearance problem when going over the bump ?

and what would the disadvantage be with mechanum ?

Re: Effective Drive Base
 

Wow. Simply amazing drive train.

I believe the best overall drive train is either full holonomic or Swerve drive. This would allow being able to rotate the robot to face the goal, as well as drive in the desired direction. Swerve drive allow the team to keep more motors free for other activities such as a kicker, but still retain the "any direction i want, i go, no worries".

Also, I do not see the reasoning behind why having smaller wheels will make it more difficult to go over the bump, as long as the wheels are extended further down. Though 4 inches may be pushing it.

Re: Effective Drive Base
 

a page or two back some one said that 4 wheel drive is hard to turn with:confused:
2006, 2007, 2009 (with traction wheels added) our team turn just fine with 4 wheels... granted we were in the wide configuration, but it is actually better at turning than a typical 6-wheeler (don't quote me on the being better part, in our experiance it is better, which is limited to 2 chassis in the 6 wheel genre)

Re: Effective Drive Base
 

I've never had a problem turning with 4wd either. Not sure what the fuss is about.:confused:

Re: Effective Drive Base
 

Our team has mainly had problems with the KoP chassis while using 4 wheel drive. The robot consistently hopped 4-6 inches off the ground. This was done with high traction wheels, which may have been the problem. This hop was greatly reduced with a welded chassis instead.

The turning with a 4WD, in our team's opinion, has never been superb.8WD would be much more efficient, and easier to travel over the bump as well.

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Simple physics and extensive experience with both types of drivetrains does not lie. Your wide orientation made the difference, by the way.

If you can't prove your logic to me then I highly suggest you learn the physics behind it and read this....

http://www.chiefdelphi.com/media/papers/1443

Note that the words "hard to turn" and "harder to turn" make a difference too.

Disclaimer: I am not taking into account possible varying CoF between the front and back sets of wheels.

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I always found 6wd and 8wd to have a harder time turning then 4wd. more points of contact = more friction... making it harder to turn.

toss up between getting over the bump easy and driving easy.

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6 wheel drive, drop center is the case in point.

On the matter of 8wd, I can't comment yet because I lack the experience in this type of drivetrain.

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but I think a lot of teams are going to know something about it by this time next week

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We'll be sure to post our results too*. I predict really slight differences in teams' 8wd set ups (slight elevations of wheels/drops/pivoting wheels). Should be fun!


* LOL at 8wd vs. Crab drive debates

Re: Effective Drive Base
 

More points of contact with less normal force at each point of contact. Its not as black and white as you described it.

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Oh, well I never said I was an expert on the subject, just never found it hard to turn with a 4wd bot

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14-wheel drive anyone? http://www.chiefdelphi.com/media/photos/26312

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We were talking about 14wd in our meeting today. We can't afford that many wheels.

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We just put these set of screen shots together with a 6WD, 6" wheeled system with a 0.25" drop center. As a powerpoint slideshow it shows the angle changes as the wheels change contact the bump. One can envision the crash at the tipping point on the down slope. Enjoy.

Re: Effective Drive Base
 

That was one of the most impressive drive trains I've ever seen.

As a brand-new rookie drive going into the Detroit Regional in 2007 I was totally intimidated by the sight of that robot. It went anywhere it wanted whenever it wanted, and there was nothing you could do about it.

:yikes:

Re: Effective Drive Base
 

Some thoughts...

Does a robot "need" to go over the bumps to be effective in Breakaway?

Consider which potential scenarios would require you to "have" to go over the bumps. How often might they occur?

Would designing for bump crossing capability (as a priority) force you to compromise other perhaps more important attribues like scoring manueverability, or ease and speed in passing balls zone to zone?

Re: Effective Drive Base
 

All the strafing of holonomic or swerve in the world isn't worth anything other robots violently push you across the floor (holonomic) or if your drive breaks (swerve) :P

My personal favorite for this year (not tied to any teams i'm working with) is a hang up between 3 different skid steer designs.

Re: Effective Drive Base
 

I think this is a great point. I know that with our robot we've had some issues with scoring design because of our clearance. On another note for the tank treads. Couldn't you just use a dual sided timing belt? Say 3/8" pitch? and 3" wide?

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Going with tank treads we have a good way to make em :D

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The team I'm working with is sponsored by Outback Manufacturing, and they'll be going with tracks built with the sponsor. If people have heard of these or have questions, I'd be glad to answer anything about them.

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Hey I have a question:

Do anyone have any idea to build swerve drive wheels?:confused: :confused:
Our team needs help designing the wheels and distributing the power from the motors.

I hope anyone can help and i cant wait till i see you all come to my hometown of the St.Louis regional!!! :cool: :cool:

Re: Effective Drive Base
 

My team thinks that the treads would slow us down to much.

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I would recommend looking at the WildSwerve (look at the Andymark website) if you're interested in doing a swerve. However, if you aren't confident in the design principles behind a crab, I would not recommend undertaking it this late in the season.

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There seems to be a lot of mis-communication and conjecture in this thread. I would suggest you simply build the kit bot using the wheels that came in the KOP and make a determination from that experiment/prototype. Each type of drive carries it's own set of pros and cons and risks for this game. Tank treads will climb but can cause excessive (near stall) current in turns if not implemented properly. Crab drive can be hard to control and requires a ton of practice to get it right. Drive systems that have a low COG on the floor may not have the same stability when crossing the bump. Prototype and then let the team decide which drive seems to work for the strategy and brainstorming you have (should have) done.

Re: Effective Drive Base
 

i have also thought of a 6wd base but i am leaning for a 4wd with 8in stickes in the front and 8in omnies in the back this allows for the traction that you will need to go over the bumps it has its drawbacks you have yo go over stright othrwise you will just slide the back sideways. it is also very manoverable used the drive system in 2008
you can easily overcome the botoming out issues by putting a type of rub rail system on the robot like the sample ones had or moving your wheals front to back and even the size of them will help im open to sugestions

Re: Effective Drive Base
 

On mecanum wheels: I saw a video of one team (who will remain anonymous) having issues steering with a mecanum drive. If that doesn't turn your mind away from mecanum, AndyMark is coming out with a lighter version of mecanum wheels on Jan. 22.

Re: Effective Drive Base
 

no mecanum if properly installed will work fine. Are team went with them this year and we think they will work fine for getting over the bumps

Re: Effective Drive Base
 

Have you driven a mecanum drive over the bump yet?

Re: Effective Drive Base
 

But if you had a well practiced driver, wouldn't it be easy to avoid other robots with a holonomic drive base? unless of course a couple of robots decided to go into your field area...

Also, rules say a robot can only be pinned for a maximum of 5 seconds.

Also with holonomic, you can just forget about traversing. If it's even important to your strategy.

Re: Effective Drive Base
 

Field areas are smaller than you think.

Pinned, yes, slid across the floor for all of eternity, no.

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Joe,
Please be careful in suggesting this or implementing something that violates the robot rules. You can't have metal in contact with the carpet as part of your regular drive design.

Re: Effective Drive Base
 

Also going off what Al is saying...

Make sure that this kind of system WILL WORK! I saw many teams in 2006 that decided to put some kind of slick rail on the underside of the robot. When the robots attempted to climb the ramp, they would either a. not make it at all b. make it after several attempts, usually ending with a half field ram of the ramp or c. end up on their back side. Just a word of caution.

-Brando

Re: Effective Drive Base
 

can you tell me how to post cant find it we are registered and all
thanks

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this i not what i ment in the sample with woody and dean thay showed the plastic and bunge cord things on the robots by the weals they can also be used as somthing to slide you across the bump to prevent hanging up

Re: Effective Drive Base
 

Post what, and where? Obviously you've figured out how to post on ChiefDelphi.

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Ok first of all tanks just crawl over cars in war. which means it should be able to go up the ramp. a skid steer would be effective with the right wheels. but i think that the tanks might actually be dominant in this game.

Re: Effective Drive Base
 

Edison,
I've seen you post this same question in at least four other threads. It is usually bad form to ask the same question multiple times, especially in different threads. I've seen your question was answered multiple times. Are you still having issues?

Re: Effective Drive Base
 

yeah with meccanum this can help your strategy allowing you to be super manuverable and get away from defensive bots

Re: Effective Drive Base
 

It surprising how little conversation there has been here regarding how much a particular drivetrain will limit ball interaction mechanisms.

With a drivetrain which covers an entire side of a robot (6WD, 8WD, tread) you largely lose ability to manipulate balls on that side. (owing to bumper height and ball incursion rules) With a 4WD system (mechanum, holonomic, swerve, or tank with modified CoF) a mechanism can exist on any side of the robot.

To example this I've been mocking up a prototype bot designed to be able to guard the goal.

with 4WD you can park it in front of a goal, raise a shield, and utilize a kicker which extends between the wheels. Should you need to get to the other goal your already oriented to do so. High CoF wheels in the rear provide shoving power and increased turning while the front wheels with moderate CoF keep the robot in a line and add to pushing power. A gearbox + motor for each wheel allows for dynamic power shifting between the different CoF wheel sets.

While much discussion has been devoted to the maneuverability of crab, holo, and mechanum, a 4WD using the kitbot frame,wheel drop downs, and wheels with different CoF (roughtops and modified kit delrins and or rubbers) you should have more than enough maneuvering for most teams. (not to mention the cost and complexity advantages)

With regards to high siding a robot, with a 4WD system and a bottom plate, without any modifications you can and will high side.

However if you install a simple textured drum in the middle of the frame which extends slightly below the skid plate and drive it with a window motor you can effectively crawl to a point where at least one set of wheels gains traction again.

Re: Effective Drive Base
 

We tested two of our traditional 6 wheel chassis that preformed very well in '07 and '08. Need less to say, six wheel bots do not like the bump. After fighting just to get on top of the bump, we knocked out a wheel coming back down.:eek: So we are going back to the articulating 8 wheel drive that we developed in '04. Hope this helps anyone still designing.

Re: Effective Drive Base
 

they're out of stock

Re: Effective Drive Base
 

and prohibited, unless they posted the designs, due to rule R25, but you could post the CAD files on this thread to make the design COTS

Re: Effective Drive Base
 

What in the quoted post is prohibited?