Posted by Anton Abaya at 1/12/2001 10:50 PM EST
Coach on team #419, Rambots, from UMass Boston / BC High and NASA, Mathsoft, Solidworks.
We are a group of ninnies with power tools… So with that thought, please post as MUCH info as u can abt TANK TREADS…designs, ideas, concepts, problems…etc…
-antoninny
Posted by Lora Knepper at 1/13/2001 8:02 AM EST
Other on team #419, Rambots, from UMass Boston / Boston College High School and Seeking Sponsorship.
In Reply to: TANK TREADS…welp.
Posted by Anton Abaya on 1/12/2001 10:50 PM EST:
Anton,
People may be nice enough to help us, but people aren’t going to design this bot for us…
To all:
We are exploring the use of tank treads on this year’s bot…any one have thoughts? Pros? Cons? Suggestions?
I drove a tank 'bot in '99 and there were a few problems that I’m not sure how to address in this one. Mainly speed and steering. The friction was so great when we’d turn that the timing belt would pop off frequently and the turning would often be painfully slow when driven like a tank with 2-joys. Also, there only seemed to be a point that we could push the drills to to power it, cutting our speed drastically. Would reducing the width of the tank treads help these issues? I have seen some decently fast and tight turning tank bots in past years…though I myself am a wheel girl all the way ;o)
I’m not an engineer…not even close, though myself and Anton are about the closest to engineers this team has. Any insights would be greatly appreciated!
~ lora T419
Posted by Anton Abaya at 1/13/2001 9:02 AM EST
Coach on team #419, Rambots, from UMass Boston / BC High and NASA, Mathsoft, Solidworks.
In Reply to: 2 Specific Issues (at least in my mind)
Posted by Lora Knepper on 1/13/2001 8:02 AM EST:
: Anton,
: People may be nice enough to help us, but people aren’t going to design this bot for us…
: To all:
: We are exploring the use of tank treads on this year’s bot…any one have thoughts? Pros? Cons? Suggestions?
: I drove a tank 'bot in '99 and there were a few problems that I’m not sure how to address in this one. Mainly speed and steering. The friction was so great when we’d turn that the timing belt would pop off frequently and the turning would often be painfully slow when driven like a tank with 2-joys. Also, there only seemed to be a point that we could push the drills to to power it, cutting our speed drastically. Would reducing the width of the tank treads help these issues? I have seen some decently fast and tight turning tank bots in past years…though I myself am a wheel girl all the way ;o)
: I’m not an engineer…not even close, though myself and Anton are about the closest to engineers this team has. Any insights would be greatly appreciated!
: ~ lora T419
indeed… i just want to know what other teams have done and learn from them. instead of starting from a blank page, i say we learn as much history about treads (both good & bad) and proceed from there…before we even speculate whether or not it can be built or should be. At this point, it seems it’s our choice.
-anton
Posted by Anton Abaya at 1/13/2001 9:03 AM EST
Coach on team #419, Rambots, from UMass Boston / BC High and NASA, Mathsoft, Solidworks.
In Reply to: oh but of course …
Posted by Anton Abaya on 1/13/2001 9:02 AM EST:
: : Anton,
: : People may be nice enough to help us, but people aren’t going to design this bot for us…
: : To all:
: : We are exploring the use of tank treads on this year’s bot…any one have thoughts? Pros? Cons? Suggestions?
: : I drove a tank 'bot in '99 and there were a few problems that I’m not sure how to address in this one. Mainly speed and steering. The friction was so great when we’d turn that the timing belt would pop off frequently and the turning would often be painfully slow when driven like a tank with 2-joys. Also, there only seemed to be a point that we could push the drills to to power it, cutting our speed drastically. Would reducing the width of the tank treads help these issues? I have seen some decently fast and tight turning tank bots in past years…though I myself am a wheel girl all the way ;o)
: : I’m not an engineer…not even close, though myself and Anton are about the closest to engineers this team has. Any insights would be greatly appreciated!
: : ~ lora T419
: indeed… i just want to know what other teams have done and learn from them. instead of starting from a blank page, i say we learn as much history about treads (both good & bad) and proceed from there…before we even speculate whether or not it can be built or should be. At this point, it seems it’s our choice.
: -anton
Posted by Ted Jones at 1/15/2001 12:33 PM EST
Engineer on team #486, Positronic Panthers, from Strath Haven High School and Drexel University / Boeing Company.
In Reply to: hehe, wanna bet? 
Posted by Anton Abaya on 1/13/2001 9:03 AM EST:
Our team discussed tank treads vs. wheels this weekend, and I came to a realization. Since friction is relatively independent of surface area, it appears tank treads would not buy you much in this competition. Friction is based on the normal force (weight) multiplied by the static friction coeficient. The static friction coef. is based on the nature of the two materials that are interacting, in this case the wheel/tread and the low-pile carpet that is the playing field. So, if surface area is not a factor, then I don’t see how tank treads gain much over wheels in terms of maximizing traction. So why does the US Army have tank treads? Because Army tanks are designed to drive over soft, unprepared surfaces. The tread distributes the vehicles weight over a larger area, which deforms the ground less. This keeps the vehicle from getting bogged down in the mud. Think of a car in the snow, or mud, or sand, essentially any soft surface. For the competition then, I can’t really justify using a tank tread system, unless you want to climb over obstacles that are lower than the top of tread. That, BTW, is another benefit of treads.
Given the time we have to design/build/test/fix and ship, I would spend more time finding an optimum wheel treatment to maximize traction. I plan on having our team conduct some experiments using a wheelchair wheel, a known weight, and the sample carpet, to find experimentally the static friction coefficients of various configurations. Once the coef is found, you can estimate the maximum pulling power of your robot, given its weight and power available.
Hope this helps,
Ted
Posted by Dodd Stacy at 1/15/2001 2:01 PM EST
Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.
In Reply to: Re:Tank Treads
Posted by Ted Jones on 1/15/2001 12:33 PM EST:
: Our team discussed tank treads vs. wheels this weekend, and I came to a realization. Since friction is relatively independent of surface area, it appears tank treads would not buy you much in this competition. Friction is based on the normal force (weight) multiplied by the static friction coeficient. The static friction coef. is based on the nature of the two materials that are interacting, in this case the wheel/tread and the low-pile carpet that is the playing field. So, if surface area is not a factor, then I don’t see how tank treads gain much over wheels in terms of maximizing traction. So why does the US Army have tank treads? Because Army tanks are designed to drive over soft, unprepared surfaces. The tread distributes the vehicles weight over a larger area, which deforms the ground less. This keeps the vehicle from getting bogged down in the mud. Think of a car in the snow, or mud, or sand, essentially any soft surface. For the competition then, I can’t really justify using a tank tread system, unless you want to climb over obstacles that are lower than the top of tread. That, BTW, is another benefit of treads.
: Given the time we have to design/build/test/fix and ship, I would spend more time finding an optimum wheel treatment to maximize traction. I plan on having our team conduct some experiments using a wheelchair wheel, a known weight, and the sample carpet, to find experimentally the static friction coefficients of various configurations. Once the coef is found, you can estimate the maximum pulling power of your robot, given its weight and power available.
: Hope this helps,
: Ted
The traction limit, in the world of FIRST, is defined by the point at which carpet damage occurs. This is some combination of the maximum shear stress and the “sharpness” (on a very small scale) of the wheel or tread surface. If any “tufts” or carpet are observed on the floor after robot traffic, the FIRST officials will be scrutinizing the robots - I can assure you from experience - for telltale signs of carpet thread wound up around your axles or stuck to your wheels or treads.
I will also tell you that the “carpet damage test” that will be applied to your machine during tech inspection can be arbitrarary, unrealistically severe, and can disqualify your bot from competition - period. There is no way around this. My advice - from direct experience with aggressive wheels - is to take spares with you that are a notch or two less abrasive/aggressive, to expect very direct scrutiny during practise if your wheels/treads LOOK particularly aggressive, and to expect no slack in FIRST’s judgement re carpet damage. And never mind if there are other bots that make it in with much more aggressive carpet interface than yours - it’s not uniform, and tough for you.
So, classical physics may say that contact area doesn’t matter in determining frictional force, that it’s all in the static friction coefficient. And those of us who drive in the snow may know that small, narrow, “sharp” tires that exert high contact pressures are the key to traction in the winter. But treads or tracks with low contact stress and low surface shear stress in transmitting a fixed Friction Force = mu x Normal Force are easiest on the carpet and hence more likely to pass tech and not get flagged off the field.
This is a tough area and a classic issue of engineering balance. Good luck, and watch for fiber wisps on your machine as you get down to practising. And follow Andy Baker’s excellent advice to load up your running drive platform to full weight and drive it hard when you are looking for signs of carpet damage.
Dodd
Posted by Anton Abaya at 1/15/2001 11:56 PM EST
Coach on team #419, Rambots, from UMass Boston / BC High and NASA, Mathsoft, Solidworks.
In Reply to: Re:Tank Treads
Posted by Ted Jones on 1/15/2001 12:33 PM EST:
: Our team discussed tank treads vs. wheels this weekend, and I came to a realization. Since friction is relatively independent of surface area, it appears tank treads would not buy you much in this competition. Friction is based on the normal force (weight) multiplied by the static friction coeficient. The static friction coef. is based on the nature of the two materials that are interacting, in this case the wheel/tread and the low-pile carpet that is the playing field. So, if surface area is not a factor, then I don’t see how tank treads gain much over wheels in terms of maximizing traction. So why does the US Army have tank treads? Because Army tanks are designed to drive over soft, unprepared surfaces. The tread distributes the vehicles weight over a larger area, which deforms the ground less. This keeps the vehicle from getting bogged down in the mud. Think of a car in the snow, or mud, or sand, essentially any soft surface. For the competition then, I can’t really justify using a tank tread system, unless you want to climb over obstacles that are lower than the top of tread. That, BTW, is another benefit of treads.
: Given the time we have to design/build/test/fix and ship, I would spend more time finding an optimum wheel treatment to maximize traction. I plan on having our team conduct some experiments using a wheelchair wheel, a known weight, and the sample carpet, to find experimentally the static friction coefficients of various configurations. Once the coef is found, you can estimate the maximum pulling power of your robot, given its weight and power available.
: Hope this helps,
: Ted
thanks for this wonderful and lengthy info… it does bring light to a lot of dark areas.
i must say though that we are using treads based on the reasons you have said above. i am just not sure if you know what we mean exactly… just look for 419 :)… wheels are cool too :)…
we did envision some kind of L.A. tank getaway with our robot where we launch off the playing field and start heading out into the crowd…
i’m kidding 
-anton
Posted by Josh at 1/16/2001 1:13 AM EST
Engineer on team #419, Rambots, from Wentworth Institute of Technology.
In Reply to: thanks for the comment…but here’s a clue…
Posted by Anton Abaya on 1/15/2001 11:56 PM EST:
: we did envision some kind of L.A. tank getaway with our robot where we launch off the playing field and start heading out into the crowd…
: i’m kidding
: -anton
SSSSSSHHHHHHHHHHHHHH!!!
Don’t give them too many hints!
They might find out about our mounted rotating paintball turret…
OH, SHOOT, you did NOT JUST READ THAT!
Josh
“Not all who wander are lost” J.R.R. Tolkien
Posted by Anton Abaya at 1/16/2001 1:28 AM EST
Coach on team #419, Rambots, from UMass Boston / BC High and NASA, Mathsoft, Solidworks.
In Reply to: Re: thanks for the comment…but here’s a clue…
Posted by Josh on 1/16/2001 1:13 AM EST:
just make sure you dont say anything about the “Death Star”…
-anton
Posted by Jim Meyer at 1/16/2001 9:06 AM EST
Engineer on team #67, HOT Team, from Huron Valley Schools and GM Milford Proving Ground.
In Reply to: Re:Tank Treads
Posted by Ted Jones on 1/15/2001 12:33 PM EST:
: Since friction is relatively independent of surface area, it appears tank treads would not buy you much in this competition.
I’m not so sure I agree. If friction is independent of surface area then why do drag cars have really wide tires and how can a tank brake from 60-0 on pavement faster than most sports cars. In my experience friction is a fickle thing that really needs experimentation to understand it well.
In my experience the way to generate lots of traction on carpet without damaging it, is to contact lots of carpet. Using double sided timing belt on a tank tread is one way to do this, albeight a difficult one though.
Tall skinny tires are good for swamp racers and snow tires because they dig through the soft top and get down to the hard bottom. This method would seem to be a little more likely to damage carpet to me.
Good luck!
Posted by Dodd Stacy at 1/13/2001 10:37 AM EST
Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.
In Reply to: oh but of course …
Posted by Anton Abaya on 1/13/2001 9:02 AM EST:
: : Anton,
: : People may be nice enough to help us, but people aren’t going to design this bot for us…
: : To all:
: : We are exploring the use of tank treads on this year’s bot…any one have thoughts? Pros? Cons? Suggestions?
: : I drove a tank 'bot in '99 and there were a few problems that I’m not sure how to address in this one. Mainly speed and steering. The friction was so great when we’d turn that the timing belt would pop off frequently and the turning would often be painfully slow when driven like a tank with 2-joys. Also, there only seemed to be a point that we could push the drills to to power it, cutting our speed drastically. Would reducing the width of the tank treads help these issues? I have seen some decently fast and tight turning tank bots in past years…though I myself am a wheel girl all the way ;o)
: : I’m not an engineer…not even close, though myself and Anton are about the closest to engineers this team has. Any insights would be greatly appreciated!
: : ~ lora T419
: indeed… i just want to know what other teams have done and learn from them. instead of starting from a blank page, i say we learn as much history about treads (both good & bad) and proceed from there…before we even speculate whether or not it can be built or should be. At this point, it seems it’s our choice.
: -anton
Try putting a VERY slight amount of front to back rocker (curvature) or vee in the tread path (on the bottom). Most of the weight is then carried near the center of the tread length, so there is less side skid drag by the front and rear portions of the tread, and it steers MUCH more easily. Good luck.
Dodd
Posted by ChrisH at 1/13/2001 12:11 PM EST
Engineer on team #330, Beach 'Bots, from Hope Chapel Academy and NASA JPL, J & F Machine, Raetheon, et al.
In Reply to: oh but of course …
Posted by Anton Abaya on 1/13/2001 9:02 AM EST:
Treads were invented to prevent heavy vehicles from sinking into soft ground. We don’t have that problem in FIRST yet. Maybe next year?
Focus on traction
Posted by Anton Abaya at 1/13/2001 8:35 PM EST
Coach on team #419, Rambots, from UMass Boston / BC High and NASA, Mathsoft, Solidworks.
In Reply to: Re: oh but of course …
Posted by ChrisH on 1/13/2001 12:11 PM EST:
: Treads were invented to prevent heavy vehicles from sinking into soft ground. We don’t have that problem in FIRST yet. Maybe next year?
: Focus on traction
thanks for this info. one reason we are into it is the traction is provides and yields. we have a robot design that needs treads. on the other hand, despite the ability to use other drive train systems, we figured we’d give this one a try considering other teams have been successful with em…
thanks for the info. if u got ideas on material etc, pls help us out with ideas.
-anton
Posted by Chris at 1/13/2001 9:51 PM EST
Student on team #69, HYPER Team 69 Quincy Public Schools Gillette , from North Quincy High and The Gillette Company.
In Reply to: 2 Specific Issues (at least in my mind)
Posted by Lora Knepper on 1/13/2001 8:02 AM EST:
Welcome to the new year laura!
Are team is fuction greatly!
We are proto typeing about 3 different ideas!
I say go ahead with the tank treads your will probaby need the tank treads to go along with your design!
Have fun being the “ENGINEER” w/out any collegiate training
An old friend