Speed to Goal?

[Ian W.]

actually, this idea of mine is simple enough that even a programmer, like me, could put it together in about a total of 5 minutes, provided that i had the right materials for the job. i fyou want to here my idea, tell dennis to stay after school one day, and i'll explain it to all. it's come up before as an idea, but everyone shunned it for reasons unknown to me. anyways, it seems that this is the best idea that we have, considering anything else won't be legal due to excess weight.

on another note, does anyone know if small parts is still selling parts to us? for my idea, i need some parts that aren't on the AHL.

[GregT]

Originally posted by SuperDanman
Well it all depends on the robot's drive train and how they are aligned according to you.

The problem was that we were trying to move TRIBE by essentially going broadside into them. TRIBE was latched onto two goals, one on the front, one on the back. We were trying to move them by pushing them right in the center at 90 degrees to their movement path.


If you try and do this, it all depends on how much surface area they have touching the carpet. If they just have 4 wheel-chair wheels touching the carpet, then yes, this is possible. If they have treads running the lengthwise of their robot, doing something like this becomes a lot harder - no matter HOW much power you have. When trying to push a bot this way, what it basically comes down to is their drive system and how much surface area they have in contact with the ground. Our problem is that we tried to push TRIBE like this more than once. Had our drivers pushed them at an angle, pushed the goal (not their center of balance), or better yet, gotten parallel to them and pushed the goal, theres a strong chance that we would have moved them. Either way - thats why we have videos of the event - to see what we did wrong and improve on it next time.

BTW, that picture didn't work. You sure you have the link right? I'd like to see this bot of yours

Surface area has very little to do with pushing power (it has NOTHING to do with friction), the only real way to get a holding advantage is to add more force on your wheels, lift the goals or somehting else. I was talking to a team at the canadian regional and I asked them what they would do to increase their pushing power, their answer was "we would use more motors"

There are ways to max traction but if you really want an advantage you have to get more then 130 pounds pushing down.

[Madison]

Originally posted by GregT


Surface area has very little to do with pushing power (it has NOTHING to do with friction), the only real way to get a holding advantage is to add more force on your wheels, lift the goals or somehting else. I was talking to a team at the canadian regional and I asked them what they would do to increase their pushing power, their answer was "we would use more motors"

There are ways to max traction but if you really want an advantage you have to get more then 130 pounds pushing down.

I'm writing this out, mostly, to try to get things straight in my head. Because, honestly, I don't entirely understand all of this.

Here's how surface area plays into things, in my mind. . . I could be off, or flat out wrong, or just somehow miscommunicating my ideas or whatever, but I'll try.

Friction, as everyone seems to know, is calculated by multiplying the coefficient of friction with the normal force of the floor on the robot. . . and, as such, by increasing the force (i.e., increasing your mass by lifting a goal) you increase the force of friction at the contact point with the floor.

Now, your drivetrain needs to overcome that additional friction to make the robot accelerate. Again, a natural delineation as a result of the increased friction.

The available torque of the motors is finite. By increasing the minimum amount of torque required to accelerate your robot, you're limiting your ability to accelerate at a greater rate, than, say, a similar robot without the additional friction.

Now, when it comes to wheel slip, the increased friction seems like it should be beneficial. You've made the force of friction greater, and thus it's harder to overcome . . .leading to a higher threshold (of sorts) before wheels slip. . .

Our design, though, doesn't rely on the added friction. Physically, in a tangible, lie-down-and-see-it sort of way, our belt material interacts with the loops of the carpeting. In this way, they are entangled (but not in a way that's damaging

So, this is how we harness the available torque in our drivetrain. Rather than make friction hard to overcome, we reduce slippage. While a wheel has a very small contact area, our belts are 194 in. sq. So, should one part slip, and lose it's grip on the carpet, the remaining part of that area has a good shot at reengaging that grip. Additionally, since we aren't overcoming extra friction, it stands to reason that we have a greater availability of torque (??) and can accelerate faster. . . That doesn't sound right, somehow, and probably isn't.

To me, it's just a slightly different method of achieving a similar end result. On a flat floor, I'd imagine, our design wouldn't be as effective.

But, that's how I see it, I think. Like I said, I don't quite understand it myself, and if someone with a degree (preferably in engineering or physics!!) wants to step in and make sense out of this for me, I'd love it. . .

In the end, though, I know what we did works. Whether our belting is excessive or not is debatable, though.

[238junior]

Our robot from team 238 runs at 15 feet a second on wheels. So we can get to the goal in about a second or two. We also have track that we can drop up in down for more traction. SO we have a two drive system.


238 Wat??

[Ian W.]

Michael-
Don't underestimate our bot on a hard floor. Remember, we pushed Mr. Drexel down a tiled floor (not sure if you were there) on the treads. There's plenty of friction in our robot and treads to push stuff on a flat, tile floor. Sure, the carpet really helps with our traction (or whatever keeps us from slipping), but we can still push more than our own weight on a tile floor. Not that moving on a flat floor even matters.

238junior-
how does your track system work, and do you have a goal grabber? cause your robot sounds strangly very much like ours. although, if you really can do 15 fps, you have an ever so slight speed advantage. if your going to nationals, i'd like to see your robot, sounds like another interesting design, cause the way we did our treads, well, ask Michael about that design.

[Eric Bareiss]

our team is about 2-2.5 to the goals but we don't grab them that fast, lately we haven't grabbed at at all, we just push, and i'll tell you it works great, with swerve drive we don't like to be tied down with a goal. But who i would be worried about is Kingman, During the playoffs in LA, they could literally hit two goals and latch in less than 2 seconds, after that it was over, they can't be moved. They never got beat to the center goal.

[Team238-aholic]

238junior-
how does your track system work, and do you have a goal grabber? cause your robot sounds strangly very much like ours. although, if you really can do 15 fps, you have an ever so slight speed advantage. if your going to nationals, i'd like to see your robot, sounds like another interesting design, cause the way we did our treads, well, ask Michael about that design.

Sine my brother is slow, I thought I could reply back....
Yes the team is going to nationals , and they can grab onto a goal....once they grab onto a goal, they can not come off until the end of a match... and thats basically all I know since I'm not on the team anymore...hehehe....I'll have Patrick explain more when he comes online....

[Tomas]

We can cross the field in 5 seconds...

[VP238]

Ian W.-
Hi i am the vice president of team 238. to let u know more about our drive system. It is a dual drive system. We start out on our wheels which are run by atwood motors so we r very fast going at about 15 fps like my bro said(238junior), ummmm we have one goal grabber which starts out inside of our robot and it detaches and when we latch onto the goal we can unlatch very easily also, with just a flip of a switch. The latch that keeps us on the goal or off is run by neumatics As so is our tracks. When we grab the goal we can drop on our tracks which gives us more traction and is harder to pull us around!! The tracks which our put down by neumatics then run on the fisher price motors if i spelt that right. This is very effective and it gives us the traction when we need it and we can switch back and forth very easily like i said with just a flip of a switch!

[Matt Reiland]

VP238 do you use only the Fisher price or the FP and the BOSCH, the FP would seem to overheat with all of the stress of tracks. Ours are practically overheating just driving 4.5" wheels (But our gearing is for hi-speed) maybe you have some super low gearing?

[DaveO'B365]

Originally posted by Matt Reiland
VP238 do you use only the Fisher price or the FP and the BOSCH, the FP would seem to overheat with all of the stress of tracks. Ours are practically overheating just driving 4.5" wheels (But our gearing is for hi-speed) maybe you have some super low gearing?

hey, just a thought, they couldn't be geared way down or they wouldn't be going that 15 fps that they say, but i guess i'll let them answer the rest for themselves
oh, and hey, i was not trying to be rude in my last post on this thread, i was just present when we decided to start this thread, and it was mind-boggling to see all these ultra-fast bots, i mean we've achieve the low 2-second range, but it destabilized our battery pulling that much amperage that quickly, so we've geared down a bit.
Dave-
Insanity is relative.

"Like olympic medals and tennis trophies, all they signified was that the owner had done something of no benefit to anyone more capably than everyone else."
-Catch 22

[238junior]

We have a dual drive system when on our tracks we use fisher price motors two of them which make the tracks go about 8fps. Also with a gear ratio of 112:1. On our wheels we use the Atwood motors which make us go 15fps, we can only go that fast on wheels!!!!!!! our gear ratio for this is 8:1.

[Phil Chang]

-after reading this forum and many threads on goal and ball grabbers, i failed to notice many users mentioning team 469, im unsure if you are well aware of our capabilities but it seems this team is under represented. Team 469 has won both regionals it has gone to, and also has been the dominating factor in both its wins. winning 2 regionals is unique in itself, but being the primary advocate of both wins is even more. 469 is a 2 goal grabbing bot and also has lift capability. 2 gear transmission and a low center of gravity. we have yet to be manhandled in power by any bot alone, and usually hold our own against 2 bots. we have been know to grab to goals, lift them, and score in the point zone within a 5 second time frame. we look forward to nationals and suprising everyone with our robot. when making lists of capable robots and dominant alliances, make sure to include Team 469-Las Guerrillas.

[Perseus]

i have a question for all the really fast robots out there.

Are you guys concentrated on gettng as many balls in th ebest time as possible?
the only reason i ask beause most of the time high speed = low torgque and if you were planning to grab a goal; you might grab it first but then get tugged around. There are solutions to this problem like being able to switch your motors from spped to torque (like team 345, a great bot from VA) and other stuff like that but i want to hear from the teams that dont do that kind of stuff.

[Matt Reiland]

This year we wanted to try swerve out (because it is soo cool) which doesn't lend itself well to gear shifting (though it could be done). After we decided to go swerving we figured we wouldn't win many pull offs with the wheels that we were going to put into steerable modules so we took the other extreme and went for all out speed all of the time. With our level of traction we can pull pretty good but we don't stall the motors we just start spinning. Is it the best strategy for this years contest, probably not, but it's fun to cover the whole field in under 5 seconds plus you can go get goals that other teams leave out there and get home quick. We will be using the speed in Florida to grab tethers and hopefully always make them come to our zone. One thing our team doesn't have is alot of designs on the shelf that we can call upon, which is changing. We would like to have a strong swerve drive which we call 'Sidestep' since swerve is pretty much a Delphi patented technology

We also want to build a killer tank this summer with a suspension, then onto gear shifting. When done we will have more parts and designs at the begining of each season and pick the best for that year. The previous 2 years had Many problems with reliability, this year we haven't broken anything on the drive yet. So that is why our robot is geared for all out speed and not power or both, hope it helps