Treads, Tracks, Tank system Talk/Help
 

The Background:
Alright, I would like to say to start off I love treads/ tracks/tank drive and feel the need to please the tank gods. My team has had a tank drive system for one year and support after that year for tank type drive systems have died and have be replaced with others systems aka wheels, omnis, mecanum, etc. The robot equipped with the tank drive system was for a while my roommate as i had made repairs but found out why then bot had so much issues like fractured lex sand framework and really bad gearboxes but yet it holds true to my heart. I'm revamping its design which is near completion but has some questions that need answering before it can be completed and also it may have more questions that i may have not thought of.

The Question:
1. What gear ratios should i have for the tank tank system (motor to gearbox output)?
Note: I'm not stupid i know there is a series of equations to find the right ratio but I'm looking mainly for what others have done that might work for me.
2. How to solve the walking effect where i seen some robots with treads hobble as they turn and even become unbalanced that the driver has to stop?
I assume this is from the tracks not being held center because of certain belt track systems.
3. How to correctly tension the tank system, such as spring loaded or motor controller tension or to have the tracks at a fixed tension set by the frame?

General Talk:
I'm also looking for just a general what you may have done in this field of drive train and certain things you may have experienced that may help me and everyone have a better idea on how to produce tank systems to please the tank gods.

Re: Treads, Tracks, Tank system Talk/Help
 

997 has a very impressive tank drive, might want to ask them.

Re: Treads, Tracks, Tank system Talk/Help
 

as do the RoboWizards 522. Feel free to contact any of their active CD members.

Re: Treads, Tracks, Tank system Talk/Help
 

Some of the issues you are asking about are typical of tank tread systems. One that you have not mentioned is the bane of tank drive using treads or locked wheels, i.e.stalled motors.
When using treads on carpet, the side friction (during turns) with the carpet is so high that robot has to hop to break free from the carpet surface. Since the motor/transmission is usually capable of enough torque to overcome the friction, the robot hops when turning. However, during these moves the motors are at, or very near, stall. In a four motor drive using the CIMs, that is potentially over 400 amps. In the IFI control system, this causes the battery voltage to temporarily fall below the drop out voltage of 8 volts, and the controller goes into protect mode disabling all outputs and switching to the backup battery. (We don't have any data yet on what the new controllers might do under these conditions.) A wheeled robot in the same kind of drive could have a little less side friction but the problem remains and they also will hop to some extent in turns. Drivers can minimize the hopping by turning in conjunction with forward or backward motion. The AndyMark style wheels that have no side friction were developed for this reason. Everyone tries tank treads from time to time, but the tradeoffs are usually significant enough that teams go back to wheeled drive systems. Any game in which turning is required will have a minimum number of robots with treads. This year's game is a good example.

Re: Treads, Tracks, Tank system Talk/Help
 

I have no robot experience with tank treads, but most tractors used a single powersource into a differential with turning brakes. This is common on wheeled tractors too (they are often called plow brakes). Using the differential and side brakes essentially allows for torque vectoring and keeping from a stall condition. A couple of teams did this style of drive system this year to help with Car-style steering robots. This probably won't help with the side traction hopping, but it may help keep the current loads lower.

Re: Treads, Tracks, Tank system Talk/Help
 

I watched a couple of shows on Discovery (one was JYW where their task was to build a tank) and I believe actual tanks used to be built the same way.

An idea I played around in CAD a few months ago took the 6WD rocking-style drive train and converted the front four wheels into tank treads. The design put most of the weight in the back so the 'bot never really rocked forward onto the treads, however the tank treads would greatly improve the ability to climb ramps. Maybe it's worth exploring, maybe not...I didn't have time to fully CAD it out and consider the possibilities.

Re: Treads, Tracks, Tank system Talk/Help
 

You can greatly increase the mobility of the tread system if you decrease the surface contact.

Take team 522 for example. Year after year they produce a successful tread system.

http://www.chiefdelphi.com/media/photos/17294

Their surface contact basically creates a square profile on the ground and allows the robot to turn with more ease.

Re: Treads, Tracks, Tank system Talk/Help
 

Thinking about tank treads and other drive configurations is probably a good idea. The past few years many teams have gone to 6 small wheel designs. For the most part the games have been played on flat surfaces. This has not always been true. What would your team do for a drive system if this years game required going up stairs or getting up on a platform?

Re: Treads, Tracks, Tank system Talk/Help
 

Your center of gravity has a very impact on this issue also. Assume you have a four cog setup (three similar to a six wheel drive setup and one tensioner) and your weight is either towards the front cog or the back cog you will run into this issue. However by finding the happy medium between center cog drop and your center of gravity as close to the center/low as possible many track systems level out on that center wheel as they reach. My understanding is that this is due to the tread actually sinking a little. This gives the robot a slightly larger footprint to balance on. Account for that and the length of the belt touching the carpet,its like turning a very short but wide wheel base. Another thing that drivers tend to do is not let the robot settle for a second before trying to turn this often throws off the center of gravity way over to the front/rear cogs. To settle the robot you don't necessarily have to stop the machine but just let up slightly to bring down the robots acceleration and allow the robot to tilt back on plane with the center cogs. However I do agree with Al in saying if it is not necessary for the game why implement it. Tread's are superb and often faster at vertical obstacles(stairs, bumps, etc.) but in a flat floor game it tends to be prohibitive.

Best of luck,

Pat

Re: Treads, Tracks, Tank system Talk/Help
 

Pull yourself up to it from the floor :D

Re: Treads, Tracks, Tank system Talk/Help
 

I'd suggest triwheels.

But I'm just a programmer, so when it comes to mechanical design I don't get too vocal about my preferences.

Re: Treads, Tracks, Tank system Talk/Help
 

We did that once with a 2-wheel-drive setup. It all depends on the specifics.

Re: Treads, Tracks, Tank system Talk/Help
 

Well first off, half the things we do in life is what we want and the other half is what we do. I personally choose the tank system for its ability to have the power to climb over any planed or unplanned obstacles. Tracks provided a larger footprint to the floor allowing for greater traction that no other dive can compare with equivalent materials (such at same gear ratio and tread material). Tracks due to their larger footprint can be harder to push around and with the right gear setup push others that may be friend or foe.

If you ever sit down and think about these robots as if part of a video game where you have different characters with different abilities you see all have advantages and disadvantages you never thought of but depending on how you do it could have some unexpected combination. Depending on the parts used, a tank robot could drive just as fast as any other bot but could never match the maneuverability of mecanum, swerve, 4(or 3) way omni, yet anyone can push around mecanum or 4(or 3) way omni, but is is far less likely for a Track system to be pushed around. So in the end what is truely necessary for a great machine because from what i see tracks offer no less than any other drive system.
Note: I'm not saying tracks are the best since their greatest disadvantages is weight and turning but yet this all depends on how you do things. Yet when you say something like "it not necessary" i can't agree. Please think about the world from both views as in the glass in half empty and half full.

Re: Treads, Tracks, Tank system Talk/Help
 

Actually, it's twice as big as it needs to be.

You have to consider this from all angles. The "cool" factor, pushing power, maneuverability, speed, maintainability, simplicity if you like the KISS principle... All of those are going to affect whether or not a tread design will be better than a 6WD/mecanum/3WD omni/swerve system for a given application. Demo robots, who cares. "Cool" factor will probably win. Prototype/practice will have a different dominant factor. Competition, yet another.

From what I understand, you're looking at doing a prototype/competition treaded robot design, not that you're actually going to use it, but that you'll have it in your bag of tricks. Whether or not you use it in competition is up to you, and you'll have to decide whether it'll fit the game requirements when the time comes. For now, design help:

I'm not a tread drive expert, but I believe that the gearing is similar to that of a normal skid-steer robot. Look at it this way: The robot lays down its floor, rolls on it, and then picks it up.

Correct tensioning: have an idler wheel that is adjustable. Slide up or down to tension. That's one way; there are others.

Oh, and for Gdeaver: 6WD (and the other systems, for the most part) is plenty good at ramps. Stairs are a different problem, but can be solved in many creative ways.

Re: Treads, Tracks, Tank system Talk/Help
 

when I was a mentor with 226 we had a tank drive for two years. We used brecoflex belts for tank treads. The hobbling that we experienced was from the track trying to scrub off the friction while turning. We ended up using an adjustable center wheel that was lower than the rest to provide better turning similar to what is used on 6-wheel bots. Not sure how low it ended up being, but I know it was between 1/8" and 1/4" lower than the rest. Gear ratios depend on the game for that year. We used a two speed shifter to give us more flexibility. Older games tended to need a lot of traction and had a lot of pushing/pulling, so we had one gear that was real low. We also had a high gear that provided around 12fps. As far as belt tension, we used a wheel that pushed down on the belt that adjusted using a jack bolt. We would tighten the bolt until the wheel was putting the right tension on the tread and then tighten a jam nut so it would not come loose. Feel free to PM me if you want any other info.

Re: Treads, Tracks, Tank system Talk/Help
 

Nicely put EricH.

Re: Treads, Tracks, Tank system Talk/Help
 

Power depends on the motors and any mechanical losses in the drive system. All else being equal, wheels and tank treads should have no significant difference in pushing or climbing power. Tanks are better at dealing with unstable surfaces, but unless what you're driving on moves or shifts there probably isn't a good reason to use them.

A larger footprint does not have any theoretical advantage in traction. With the same coefficent of friction and the same weight, the amount of surface contact is not a factor.

With carpet deforming more under the concentrated weight of wheels, the actual traction of a FRC robot is somewhat complicated to predict in advance. Experiments seem to show that wider wheels are better in practice than narrower ones, but long tank treads don't give the benefit you attribute to them. On the contrary, the difficulty they create in turning is usually considered to be a good reason to avoid them.

Re: Treads, Tracks, Tank system Talk/Help
 

This is sort of true. With compliant surfaces like carpet, rubber tires and treads there is some degree of mechanical interlock that can change the grip level to normal load.
While you can generally equate a coefficient of friction as a constant, there are noticeable changes relative to load. I think 494 did a neat project on this.
%slip also makes a huge difference.

Any students interested in a good/simple science fair project, this is a solid one. Map the coefficient of friction between two materials (let's say carpet and brown ruff belting) vs. contact area and load. You will get a really cool 3D curve and likely win some scholarship money (and might even learn something) in the process.

Re: Treads, Tracks, Tank system Talk/Help
 

Has there been a game yet that REQUIRED teams to climb obstacles? Seems a lot of the successful teams from 1999 and 2004 found clever ways to avoid climbing things.

Re: Treads, Tracks, Tank system Talk/Help
 

There have been games with obstacles that needed to be climbed. But I understand what your saying.

But treads, WHEN DONE RIGHT, are a great option for maneuvering up and over obstacles such as steps, ramps, etc...

There is a reason why tanks use treads.

Re: Treads, Tracks, Tank system Talk/Help
 

Now to get back on subject. His question wasn't "Should I do treads?", but "How can I best do treads?".

1. I can would agree with some other posts in this thread that 2-speed is a great way to go as far as treads go. A lower gear for turning, pushing, and getting over obstacles and a higher gear for everything else. I would recommend something like a 15:1 for low gear and a 10:1 high gear but this is really something you have to play around with. I don't know what your target range is. The low gear is the most important to figure out, as the high gear is really just what you want your speed to sit at. You have to make sure with your low gear to not get screwy with the amperage.

2. The walking effect as others have mentioned is from the treads overcoming the enormous amounts of friction. A great way around this is decreasing your floor contact. Look at the picture of 522 i posted earlier.

3. From experience, I know you do want to go with some sort of tensioning system. Look at the way many teams tension chain. Many of the techniques can be replicated with belting. You want to make sure to get a good wrap on your drive pulley(s). So keep that in mind as well.

The one thing you need to realize is that More Tension = More Current Draw. Less Tension = More Slippage. You need to find a good spot.

As far as general experience goes, when I was on 269, we tried treads in 2006. We made the mistake of using friction belts instead of timing belts. Needless to say, we failed miserably and stripped out the whole drive at our second regional and replaced it with 2 wheels.

Re: Treads, Tracks, Tank system Talk/Help
 

I see tank treads as having two advantages. One is in the real world where you have heavy vehicles on very soft and irregular ground. They do help reduce the ground pressure, as is beneficial for tanks and agricultural tractors. The other is in climbing over irregularly shaped objects, as there is a piece of tread that can catch whatever traction surface is available and not leave you "high-centered". The downside comes on a somewhat regular and relatively high traction playing surface where you have to contend with turning and keeping the tread on.

My personal experience only extends to 4 wheel drive using fairly large, pneumatic tires (Skyway). Those things had more than enough traction to make turning difficult, despite a very short wheelbase. In one regional competition shoving match, we and the opponent both flipped over backward as a result of a standoff pushing match. Neither robot moved more than a couple of inches one way or the other.

In terms of "best doing treads", what are peoples opinions on the number of drive and bogey wheels, and methods of tensioning?

Re: Treads, Tracks, Tank system Talk/Help
 

Before you start, really do consider tires if this is for a FIRST robot. We used tracks in '04 and '06, and found tires to be far superior ('08). 6WD or a 6x4 have proven to be great drive trains.

For us, a sliding/clamping tensioner proved very effective. Our favorite and lightest tensioning scheme was on our '06 robot. The last wheel mount point was on a seperate piece of aluminum which has a slot milled out of both of it's sides which slid in and out of a groove milled into the main part of the frame rail. So, to tension, you just took something like a screwdriver and pried the tensioner away from the frame rail hard as you could, then tightened two bolts that clamped down the tensioner (the two sides of the tuning-fork-like cutout in the end of the man frame rail). As a note, the only problem with our '06 robot's track system was in the design of it's bearings: the design of the bearing mounts had too loose of tolerances, which allowed the end sprockets to deflect slightly, allowing the track to work itself off if hit from the correct angle while doing a turn. As a redesign, simply taking more time to make each bearing pack would have eliminated this problem.

We used BrecoFlex both in '06 and '04 on custom FDM sprockets.

-q

p.s. If anyone wants a picture of the tensioner clamp system, just let me know and I'll see if I can dig up one or two to post.

Re: Treads, Tracks, Tank system Talk/Help
 

"...really do consider tires..."

I agree. If we were competing on a course of loose gravel or shale, I'd seriously consider tank treads. Otherwise, I think it is overkill. Do not confuse cool-looking with effective. As they say, "Run what you brung". The results will tell...

Re: Treads, Tracks, Tank system Talk/Help
 

In the context of FIRST, the only real advantage treads has is in climbing obstacles/uneven terrain.

I also believe that in every game so far, there were much simple ways to traverse the obstacles than treads. It'd take some really rough/odd obstacles to get me to advise my team to use treads.

Re: Treads, Tracks, Tank system Talk/Help
 

Yes, the reason is that they are better at spreading the weight of an 80 ton battle tank when crossing mud.

I won't advise you how to do tank treads because I don't know how, but I will advise you to look to the military and their move away from treads. (run a search on Stryker) Tank treads are great for uneven and shifting terrains but for speed and maneuverability they are not the most effective.

Now, would it be cool to do a tank tread system that could climb a 70 degree incline as a demo? Oh you bet it would be. My best suggestion would be to look at the military tanks and how they work. An interesting thing to do might be to have a way of letting your treads lose friction as they are moving sideways (similar to omni wheels) Might be interesting to make work, dont know how useful it would be though.

Just my (programmer's) $.02

Re: Treads, Tracks, Tank system Talk/Help
 

I started this thread to help myself and other to improve and create ideas about track systems. Though it seems most here are rather happy to bury them in the ground and call it a night. I admit that a track system may not be the best drive system or easiest to build but that doesn't mean that they wouldn't be as effective to a game as any other drive system. It truly depends on how you build you machines and how you operate it.

To step back to the main part of my project folder which i didn't want to do . Here is the true purpose:
To create a universal framework that can be use for the most of the FIRST drive trains and to be suitable to the challenge.

So in my work I'm at the final part of this which is adapting it to a tank type since the wheeled versions are completed. Though since for track systems i only know a few minor things about I figured I might ask around to team who have tried them to get a better idea. I really don't want to talk about my projects since i filled in the gaps to this point and wanted to keep the thread focused on what i didn't know and what could be done for track systems. The funny thing is i didn't expect it to get unfocused and try to push me away from a track system.

Re: Treads, Tracks, Tank system Talk/Help
 

Image from back in the day

I'm not sure if I can be much help to the cause but our team ran tank track back in the day, though now we are know by those who visit our pit for drum wheels.

Recently two of us attempted to resurrect this robot and learned a little about how the treads worked. It was tensioned with a worm gear, and before the old gear boxes gave way seemed to maneuver fairly well with the tension on the looser side of tight. It wreaked havoc on the breakers though you could year them popping clear across the shop when the tension was too great and it tried to draw more current.

Re: Treads, Tracks, Tank system Talk/Help
 

You've gotten a pretty consistent answer: the best way to do tank treads is not to do them. :) It seems that most teams who have tried tracks don't do them anymore. There's probably a good reason for that.

Re: Treads, Tracks, Tank system Talk/Help
 

Do people fail to see i will not take that answer, i will not quit if i fail the first time, I'll try again until i get it right. I feel that since i put help into the title i would get only help and some talk about track systems. So in my mind i feel that if you going to post anything about going to wheels or saying flat out that tracks should not be used i will close this tread and only communicate to those that have given interesting ideas and help. So help me if enough people do this I'll close the tread and not support the post count that it has generated for you just to try to kill a plausible idea.
People seem to think i know nothing about wheels here or any other type of drive systems, That i may lack the understanding of advantages and disadvantages, that i may not know strategies or something...............................I'm sorry just please for the love of something just help me with my questions and not put some tiny little post saying not to do this. Personally i never said it was for competition, i never said it was for cool factor, i didn't say it was for a lot of thing but people here seem to assume. I don't know what to do anymore i think i have enough to live by that i don't need some people here being bias and persecuting a idea. Man i feel like i might as well be in the past trying to challenge the church or something for wheels.

Re: Treads, Tracks, Tank system Talk/Help
 

I am inclined to agree with Void, I've lurked on many a threads about this topic and all too often people assume it will be used for competition. The honest truth as he stated is he never once mentioned competition use, He might have mentioned a design of a universal chassis but that is all.

There have been a few responses that have been made with the honest intentions of help, and there are others who insist on thoughts based entirely on FIRST competition environments. This is a little news flash for some of you there are robots built outside of the little FIRST robotics bubble. I hate to see the witch hunt against free thinkers continue on this little ragtag forum, but it seems that there isn't a genuine desire to think differently

Re: Treads, Tracks, Tank system Talk/Help
 

Team 48 has used tank tread drive trains of various designs with great success since '04. As a team that loves to play defense, we utililize the traction and stability that tank treads provide. Examples of our past tank drives:

2004 - triangular design to climb the vertical side of a 6" high platform
2007 - combined with 2-speed transmission, provided superior pushing power
2008 - a year where no one in their right minds would have thought to use treads, we wanted them for stability around the corners while carrying the trackball

As for the issue with turning, we were able to solve that with a couple methods:
- including one or two bogey wheels located under the CG point that could be lowered 1/8" to 1/4"
- instead of full-length treads, use a half-track system with omni wheels, such as our '08 robot shown above. A more typical method is moving the treads to the rear of the robot and a pair of omnis at the front. You maintain your pushing power, but the turning is much smoother.

Also, drivers need to develop "tank steering". With older tanks, you don't often see one turn on the fly--often they drive in a straight line, then stop forward momentum to turn with one tread going in the opposite direction of the other in a zero-radius turn.

For belt tensioning, our shop teacher developed a system that tensions the dead axle of the non-powered outer wheel. This was used in all of our systems and can be seen in the pictures above.

One of the biggest issues we had to deal with was the sheer stress on the belts brought on by side contacts, as our driver liked to interfere with another robot by drivng in front of it perpendicularly. If your robot is pushed from the side, the belt can twist (sometimes right of the tread wheels) or sheer a steel-reinforced belt in half--and that's not pretty when the belts run between $150-300 each. You have to have a system in place that keeps the entire length of the belt in contact with the carpet (or at least at minimum intervals) from sliding sideways, be it with bogey wheels, slider blocks, etc. Keeping the belt in line is critical in a successful tank drive. With a half-track system, we found that the side stress were much less due to the shorter length and extra lateral support was not needed.

Please feel free to PM me about this.

Re: Treads, Tracks, Tank system Talk/Help
 

If you come to a forum devoted to the FRC competition, and ask for help, people are going to assume it's for the FRC competition. People will then post the best advice they have. This is what happened, you can't blame the people that replied for it. If the original post had said, "Hey, we're just having fun here, this isn't for FRC, help me out with this tank drive", people would not have offered him the good advice for FRC, they would have offered him a different set of good advice for just getting his tracks working.

If I go and post in a forum for battlebots about making a drivetrain and not say it's for FRC, and then get mad when people suggest many things that are contradictory to a FRC drivetrain or not helpful, I really can't get mad at them for that.

Re: Treads, Tracks, Tank system Talk/Help
 

But does that really give a reason to tear an idea apart even if it were to be used for a competition purpose or personal project.


And thanks M. Mellott i will take you up on that offer sometime

Re: Treads, Tracks, Tank system Talk/Help
 

Because you didn't indicate otherwise, the masses assumed this would be for FRC competition (as is most of the technical posting on here) and offered some good advice; tanks aren't ideal for the FRC competition. In fact, your original post makes it seem very much like it was for FRC competition. You can't really fault anyone for what they said, they offered good advice.

Now, as a personal project, go ahead, have fun, get it done. They may not be the best choice for a FRC robot, but they sure are cool.

Re: Treads, Tracks, Tank system Talk/Help
 

Fine what ever you want to think, yes i admit the initial post is very opaque on that. But isn't it unfair for a person to ask a question and get answers that you didn't ask for. i expected help would bring the essence of the word to my questions and not some little post going off on how treads are bad, wheels are good. If i ask what color the sky was and they said 4 or something i would be irritated like i am now.

Re: Treads, Tracks, Tank system Talk/Help
 

Tear apart? No. However, Adam is right; put a thread in Technical Discussion without some frame of reference to the contrary, and people will default to thinking about FRC applications.

Of the teams I've worked with, only one has ever attempted treads; that would be 1293 in 2007, the first season I was not active with them. Their entry that year, Atlas, had some limitations. Their approach was solid, with the exception of their gearbox mount; the BaneBots gearboxes they used were mounted in the front of the robot using an open-front frame for their grabber. This left their setup particularly exposed to hits, and left them scrambling to move in their last match where they partnered with us. Some might argue it to be too solid; each of their drivetrain pods weighed over ten pounds. (That thread actually has a lot of tread lessons learned; I'll see if I can get a member of the team to offer any further insights here.)

You may also want to read Chris Hibner's paper on drivetrains. Much of it carries over from wheels to treads.

For the side talk about the appropriateness of treads, I say this: I care about whether your robot can successfully execute a strategy that complements our own. Wheels, treads, kiwi, swerve, it doesn't matter; all that matters is that I can rely upon you to execute.

If you ask me a question about how to step on a car's gas pedal, I would feel obligated to make sure you were aware of how to step on the brake as well. The ability to relay both sides of an issue is important in any regard.

Re: Treads, Tracks, Tank system Talk/Help
 

My advice would be to go look at teams who have done treads well in the past-45, 48, 1114, etc.

You will probably have 2 or 3 big issues to overcome. One is tensioning the belts adequately. Another is making sure that when you get pushed from the side they don't fall off/shear. The last being to make sure that you can actually turn (Drop one of your idler pulleys to reduce your contact patch with the floor).

Another concern is that the belts are VERY expensive. I believe most teams use the steel core heavy duty self tracking Brecoflex belts. They can be $300 EACH. Brecoflex also has a 2-3 week lead time on their belts. In addition many teams have had problems with their belts shearing. I believe some teams have had better luck with FN Sheppard (prices/quality/lead-time).

I personally think that there are very few (nearly zero) situations in which a treaded drive is a better use of resources/more useful for a FRC game than a standard 6WD chassis, but it can be a good learning experience for you and your team.

Re: Treads, Tracks, Tank system Talk/Help
 

Nicely put Billfred and thanks for the edit but i still have only one thing to say. I never said once if this project was or wasn't for competition. So to put it out there its both. It is how EricH said about having ideas in a goodies bag whether i use them or not it up to my team, but at least i have a plan if we do choose that road or even if i choose that road in my spare time. Also ideas from one systm can be used in other systems. So in result the thread is your you can choose what to do with it since i have gotten enough information and people to help me produce this plan for this road.

Re: Treads, Tracks, Tank system Talk/Help
 

Lynx,
You have to remember that the answers you receive here are tempered by our involvement in FIRST robotics competitions. The advice you receive is aimed at those competitions only. The comps are played on carpet which can be an unforgiving surface for tracked vehicles unless a particular game (and strategy) warrants their use. The picture above and the caption explains it pretty well, "It wreaked havoc on the breakers though you could year them popping clear across the shop". In addition, the type of treads used in this picture would not be allowed under 2008 robot rules as no metal can come in contact with the carpet. The only advantage in this picture is the curved ends of the tread cleats. In a turn, these tend to slide across the carpet while giving increased traction in the forward and reverse modes. I will say it again, treads in a turn or six wheels/no steering, create significant electrical loads that can comprimise the control system electrical power source. As such any good strategy would be to avoid, at all costs, mechanical designs that draw excessive currents. There have been (and likely will in the future be) games and strategies that use treads to a advantage. These games will likely involve climbing with little or no turning required.

Re: Treads, Tracks, Tank system Talk/Help
 

While it is conceivable that the GDC will put a difficult terrain on the field for all robots to traverse, I do not believe it will ever happen. First, rookies still have to have a way to be successful with the bot, hopefully just by driving and pushing something. Otherwise many would be discouraged in their second year.

Then there's the fact that the field itself is already alot to move around when it's just carpet. Volunteering at Battle O' Baltimore 2 and then sticking around for field teardown at the end really opened my eyes to what it takes to create something that's easy to setup. Whoever designed the field is a master of aluminum extrusions. On top of that, there was very little room left in the NASA trailer for additional field elements after the overpasses, electronics, and general field equipment was put in it.

So for tricky terrains -- you can always hope, but I think there will always be a way to not have to deal with it.

Re: Treads, Tracks, Tank system Talk/Help
 

Jesse,
Ramps, stairs and platforms are all field elements that have been used in the past and will be seen in the future. Those are the elements to which I referred.

Re: Treads, Tracks, Tank system Talk/Help
 

The TechnoKats' tank-treaded robot was built long before I became a part of the team. It is one of the few old drivebases we have that still function, but its relevance for current design is very limited. It was made with a major underlying feature: wide metal cleats. It looks a lot like the picture Mr.Rush posted. That helps maintain forward traction while allowing a certain amount of side slippage. It still won't turn without using a lot of power.

In the years I've been with the TechnoKats, we haven't seen a game where we would consider trying tank treads again. They just don't give an advantage over other drive systems. If the field were deeply covered with sand (or corn), they might make sense, and we'd probably apply a lot of thought to how best to design them. But on carpet, or tile, or concrete...nope.


Looking back on the first post, I see an issue I overlooked before. It looks like Lynx has already designed the frame with wheels, and just wants to know a good way to put tank treads on it instead. He probably isn't going to like my saying this, but I don't think a "good way" exists in such a case. Changing from wheels to belt-style treads will likely only make it perform worse.

Re: Treads, Tracks, Tank system Talk/Help
 

Al seems to have misunderstood my post (not the least bit surprised) the breakers were popping wile the chain tension was too high, not when properly adjusted, and at no point did the chain contact the ground the rubber cleats are a hair shy of a half inch in thickness. (its a vintage bot from the '01 game Diabolical Dynamics)

And yet again we have some one jumping to the rule book and its not even build season. I understand that FIRST experience guides your judgment, but if his project is out side of the FIRST bubble then why bring up the rules?

Re: Treads, Tracks, Tank system Talk/Help
 

Don't forget one of the most famous tread bot Johny 5.

That robot seemed to move pretty smoothly on a lot of different surface materials and surfaces. (Could be movie magic)

Essentially that machine was a 1/2 track with articulating treads and a rear caster wheel set. It may be worth reviewing those movies just to watch the tread motions and the machines manueverability.

Re: Treads, Tracks, Tank system Talk/Help
 

Mr. Rush,
Treads of this type were common at one time and the color of the cleats that appear in your photo, appear to be made of aluminum, another common design of years past. It is to that type of design to which I made reference. As to the tripping of breakers, I would bet that on carpet they were tripping. Not as often as other designs due to the small turning radius but there none the less. Rack it up to thousands of hours of experience with FIRST robots gained over a 13 year period. As a rule of thumb, any drive with high side friction will send the motors into stall or near stall. On the van door motors in the photo , that is 69 amps per motor as I remember. As to the reference to rules, I have to interject that as a Lead Robot Inspector. Often team members make decisions based on their expectation of rules and neglect to examine closely the changes that occur every year following kickoff. For instance, there is no guarantee that the motors you have used in the past will be present in 2009.

Re: Treads, Tracks, Tank system Talk/Help
 

Well Al you're wrong the cleats as you have dubbed them are hardened rubber, The vandoor motors powered a set of arms not the drive train. You are making too many assumptions. It was powered by a pair of dewalt drills. Feel free to toss as many self important titles as you want around but quite frankly you can take you high horse and shove it.
I am more than aware that things change (the removal of the mini bike motor from the kit of parts as an example). I also under stand that the current changes based on load. And once again we point out that the discussed drive trains aren't necessarily intended for FIRST competition use. Aspects of them might be used if permitted, but if I understand void's goals this thread was meant to gather knowledge , no finalize any design.

Re: Treads, Tracks, Tank system Talk/Help
 

Watch it.

When someone asks for help, they ought to be grateful for what they receive rather than complain that they aren't getting what they want. Ask more questions, refine your language and clarify your thoughts if things don't go the way you'd like, but know that it's patently absurd to think that insulting anyone, threatening to close the thread, or anything like that is going to make things better.


Someone said it best when they said, "You take the good, you take the bad, you take them both and their you have the facts of life."

Re: Treads, Tracks, Tank system Talk/Help
 

The motors I see connected to the drive sure look like van door motors. Are you sure you're describing the same robot you posted a picture of? There is a lot of wiring blocking the view, but it doesn't seem to show either arms or drill motors.

Your understanding is incomplete. A totally unloaded motor still draws its stall current for a moment as it begins to spin.

Re: Treads, Tracks, Tank system Talk/Help
 

the arms are the two inch thick portions of lexan between the main body and the tracks them selves if need be I'll take a picture of the gutted and cleaned robot net shop day. The main drive is indeed drill motors.

As for my insulting people the Origional poster clearly said he understood that the tread style drive had its draw backs and he understood that, thus having people posting in this thread proclaiming the drawbacks have been unnecessary posts, and not contributing to the topic.

Of this I was also aware, My wording might not have been clear however.

Re: Treads, Tracks, Tank system Talk/Help
 

Lego NXT Johnny 5.

Pretty cool. I am amazed what people can do with legos.

Re: Treads, Tracks, Tank system Talk/Help
 

Mr. Rush,
You have jumped to a number of assumptions as well. The original poster and I have communicated privately and I am merely adding to the discussion for the benefit of those others that are reading this thread. Don't forget, there are many who lurk here who will gather wrong impressions if just reading uniformed posts. When someone asks for help (including you) I will give them as much information as I deem necessary for the original question(s).
As to the van door vs. drill, you have now taken it to another level as the drill motors draw between 95 and 100 amps depending on which factory they came from. Should there only be two motors then the issue with the power source remains but is lessened over the short term. Beyond about 4-5 minutes of run time, the battery will still fall to below the required eight volts at which the RC ceases to function or switches to backup battery. Since no backup battery is visible I can assume that the RC is an early version and will simply shut down during these high current situations and the result is a four to five second reboot. I believe it was stated earlier that this is a 2001 robot which would put the RC in the pre backup version.
As to the composition of the cleats, being plastic or rubber or aluminum does violate 2008 rule R06 "Traction devices shall not have surface features such as metal, sandpaper, hard plastic studs, cleats, or other attachments". Since this important for students thinking about their 2009 robot, I included it in my previous discussion.
As to gathering knowledge, is it better to fail and fail and fail yet again or ask and receive knowledge from one who has experience. It seems like the old adage "Don't reinvent the wheel" applies.

Re: Treads, Tracks, Tank system Talk/Help
 

I too have been talking with the Original poster (the room mate he mentioned) and neither of us are students at this time. The robot is currently using the radio from the past two years not the old radio, and even in this design there was a backup battery mounted underneath the rest of the electronics board. We've installed a new "brain" using parts left over from the past two years. We've talked to more than a few of the old guard for reason for the design. It was built to fit under the fence and the balance beam utilized in that years game, It was they admit not the greatest of robots but it was a niche robot one of the few capable of both functions. On its own it couldn't score very well on its own, yet was desired on an alliance.

Its good in my opinion to think about the past and understand the odd ball designs that have worked in the past and consider how they differed from the others to push the envelope that much further. Bomb Squad is one of those teams who make a good show, Metal Emotion back in the day, and who can forget the Overdrive exploits of the robot Tumbleweed.

I apologize for my out burst earlier as well. I know you mean well its just a pet peeve of mine to see topics blown apart by people spouting rules.

Re: Treads, Tracks, Tank system Talk/Help
 

In other words, there has been a slight redesign for a newer controller. That is good. (I say this because pre-2004, there wasn't even a capability for a backup battery.)

Yes, it is good to think about the past. You can get some great ideas that way. However, you have to re-engineer them to fit current rules. Let's take the 1998, 2001, and 2004 big-ball robots and see how they play Overdrive. They'd do fairly well, with a little rebuilding to comply with ball size. Now use the 2008 motors.

Re: Treads, Tracks, Tank system Talk/Help
 

Oh it seems there were some typos in my post weren't there? Now that was an honest mistake....need to not be writing these post on an I-pod touch...

Re: Treads, Tracks, Tank system Talk/Help
 

Interesting idea for treaded vehicle manueverability.
Have the treads be speparate articulating pds from the main body. do a high pivot on the rear structure that way when turning it would jack the inside tread pod and give a single point of contact on the inside.

Re: Treads, Tracks, Tank system Talk/Help
 

I would love to do a tank design using links like a real tank and the rollers from an AM 6" mecanum wheel mounted sideways. Kind of like a omni tread. Or maybe even a few rubber links spaced in the tread to help give a little resistance to sideways pushing.

Re: Treads, Tracks, Tank system Talk/Help
 

Interesting idea. It'd be easy to put that setup on a steel cable around pullies and create the same effect as tank treads. At $3 per roller, 7 feet of belting is only $156 + the cable and shipping...comparatively cheap. Your other option is to use a full-length track of those and a separate short-track belt tread (that runs off the same transmissions) in the middle to provide resistance to sideways pushing.

I wonder what the initial expression on A/M's face would be when they see an order for 100 of these and no associated mecanum wheels :ahh:

Re: Treads, Tracks, Tank system Talk/Help
 

Hmm this would highly interesting i had have some ideas about this but didn't know if the effort would be to much or if the robot could be anything more than a push bot but, since i haven't done the measurement and only have done coffee napkins of this i wouldn't know what is possible. but i do know you would still have to obey the laws of mecanum with 4 individually power track (mecannum version) systems. now the only component i see that would be troubling is making those tracks but other than that the system would be simple. Also just thinking about it you could lower the inner wheels a little to get the turning a little bit better like the other track systems. If anyone plans to do this let me know. I know i will try again at it but whether or not i use it all depends but as far as i know no one else has done it.

Re: Treads, Tracks, Tank system Talk/Help
 

im confused here for a sec...

I've heard when treads are used that people call it tank drive BUT when people use 6 wheels drive they also call it tank drive. What??:confused:

Re: Treads, Tracks, Tank system Talk/Help
 

Tank steering is a control method in which the two sides of the drive train can be controlled with independent joysticks. It allows for turning without having to stop moving forward, and is an alternative to just a single stick steering choice.

Tank treads can be used in a tank drive, which is just the drive train.

Re: Treads, Tracks, Tank system Talk/Help
 

Also, Tank steering is also known as skid steer.

Re: Treads, Tracks, Tank system Talk/Help
 

Yeah i started realizing that error in my writing and started to use tracks in place of tank since like most first robots that use a tank drive with either wheels or tracks.

Re: Treads, Tracks, Tank system Talk/Help
 

Re: Treads, Tracks, Tank system Talk/Help
 

I at one point had a detailed plan drawn up for our little four tread mecanum drive. The one issue I ran into was the one mentioned in the pictures comments, The lack of a simple and reliable way to join the link/rollers together. I never did make it to the prototyping phase due to the lack of materials and funds.

Treads, Tracks, Tank system Talk - Help Needed
 

Hey guys, my team is researching new drive systems and my group is doing the tread/tank drive system. I would greatly appreciate it if anyone would give me lots of tips and information on how to design such a system. If you could give me some sites to look at to get some more ideas that would be greatly appreciated. I especially would like to know what types and suppliers of belts/treads have been used in the past and which ones are the best to use. Thanks.