Re: Top speed?
 

this is where is all goes awry, since that does not exist :yikes: :yikes: :yikes:

Re: Top speed?
 

Along with the need to draw more amps than our breakers provide, the ability to accelerate hard enough that your tires rather than your motors are the limiting factor, the ability to turn controllably without losing velocity, the assumption that nobody would get in your way while you lapped, etc. It was all just a thinking exercise to figure out the absolute fastest laptime possible. The next step would be to constrain it so that your power output is less than 120amps and see what happens then.

Re: Top speed?
 

It's all relative... ;)

It all depends on what type of drive system you are going to be using I guess.

Re: Top speed?
 

There is no rule that specifically states that you must obey the law of physics during the competition. This may be an oversight.

Re: Top speed?
 

I believe that is covered by <General Rule 0>: the part about "...recognition of science..."

Re: Top speed?
 

last year we had a 16fps robot and if anyone was at the Milwaukee regional they would have seen our programming error where we went full forward for 2 secs and for got to put the stop in. Needles to say it was devistating we hit the far wall at full speed and thewheels just kept moving. Head ref estoped us and that was the end of that. It truly was a sight to see.

Re: Top speed?
 

This makes me chuckle a little bit. Last year, we had a 7fps crab system. Driving full forward and doing a 90 degree crab maneuver put a ton of stress on the drive modules. We cracked the hubs on quite a few wheels due to the tremendous side load. I can only imagine what would happen if the wheels of a robot moving 20fps were suddenly turned perpendicular to the direction of travel. :eek:

Re: Top speed?
 

I think you should consider that just like last year - in the absence of other robots you might be able to hang 10 or 11 tubes. When other robots are present, however, you are sometimes lucky to hang 3 or 4.

I would bet with slow movers on the course and having to dodge other robots, even disregarding hurdling and pushing balls, you'll average 8-10 second lap times.

Re: Top speed?
 

As I remeber hearing once. I don't care about the car that goes 0-55 inn 2.5 seconds. I want the car that can go from 80 - 50 in 1.2 seconds. It's not gonna just be how fast you get around the straightaway but can you survive the hairpin turn.

Re: Top speed?
 

I've been thinking. With a speed of 10fps it would take you about 5 seconds to travel the length of the field. Double that and add about 5 seconds overall turning time and you get a lap average of 15 seconds. This is of course without anything in your way.

If you did average 15 seconds a lap, the max number of laps you could do in two minutes is 8. Now if you started at the right spot, you can cross the finish line 9 times, scoring 18 points. This is even with traffic.

I'm not really expecting more than 5-7 laps for one robot in a match. No matter how fast you are going.

Re: Top speed?
 

Going around this turn reminds me a lot of autonomous mode of 2003, some teams would steer (mine included) and some teams had tank but would have wheel lowered on an angle that would steer them around the corner then bring it up into the chasis (312 did this and a few others but I can't remember them now)

Re: Top speed?
 

This is somewhat related to the topspeed discussion so I figure I'll ask it here. When determining the "top speed" of a robot in relation to it's gearing, wheels, motors, ect. what point on the motor curve are you taking the RPM numbers from? My team is a second year team with little or no help from any Mech E's and we are looking to do a bit more in terms of drivetrain design than we did last year.

So when someone says they have a 15fps or 16fps robot what RPM is that on the motor (assuming 2.5" CIM)?

Re: Top speed?
 

It depends on the size of your wheel. If you go 16 fps with 8 inch wheels then your motors will be rotating twice as fast at 16 fps with 4 inch wheels

Re: Top speed?
 

I can easily see teams doing laps under 10 seconds with a great line of travel, and no interference.

Whether or not this will happen is to be seen.

But it can, which to me is pretty darn awesome.

Re: Top speed?
 

It also depends on the team reporting that speed. Relatively few teams measure actual speed (I think the Martians do, but beyond that I can't think of anybody). So, then you get into theoretical calculations. Some teams approximate inefficiencies (JVN's famous .81% of free speed is an example), some just use the 12V free speed, and some report numbers based off of operation at 40A draw.

I wouldn't use the 40A one, because most of the time you aren't going to draw that much just driving around, and if you are you're probably in trouble. (40A per motor doesn't leave much wiggle room at all on either the motor breakers or the main breaker) Similarly, I highly doubt teams will be driving with their motors running at 12V free speed; however, there is something to be said for the argument that the battery doesn't output 12V, more like 13.5ish, and that can make up for some of the inefficiency losses. The approximation method may end up more accurate than either of the above, but that is obviously dependent on how accurate the inefficiency approximation itself is.

Personally, I just use free speed in calculations because it is easier to work with. In my experience, underestimating speed has worse consequences than overestimating (to many interrupts per sec, dead-reckoning autonomous driving too far, etc). Whatever you choose stick with one; you can then compare speeds year to year much easier than if you had to convert from one method to the other.