Posted by Eric Rasmussen.
Engineer from FIRST.
Posted on 1/28/2000 4:12 PM MST
Check it out.
-Eric
Posted by Joe Johnson. [PICTURE: SAME | NEW | HELP]
Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.
Posted on 1/28/2000 5:35 PM MST
In Reply to: Team Update #6 is Out! posted by Eric Rasmussen on 1/28/2000 4:12 PM MST:
How many other folks out there were under the wrong impression about bumpers prior to Update #6?
We were very much so.
Under our interpretation, we thought that we had essential an ENVELOPE that was vertically centered about 6.5 inches above the floor.
Now, we learn that the BUMPERS must be vertically centered at 6.5 inches above the floor.
This is a very different thing indeed!
Now I begin to wonder what other rules on bumpers did we miss. My first thought was that the bumpers were perhaps required to have the wood backing (sink-o). But, thanks to a later Q&A:
Q175. Does the hard backing for the bumper have to be made out of wood?
A175. No, the hard backing does not need to be made out of wood.
But questions still abound:
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Is ‘hard backing’ required? If so how hard is hard?
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A bumper the is ‘vertically centered’ at a given height may be interpreted to imply some rough symmetric shape that is ‘center-able.’ So, my next question is, is there a requirement that the bumpers have some sort of symmetry about the centerline?
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This, of course, leads to another question, is it the whole bumper that must be ‘vertically centered’ or is it the outermost edge of the bumper that must be ‘vertically centered’?
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Yet another question, does each cross-section of the bumper have to be ‘vertically centered’ or can the entire bumper be ‘vertically centered’? The difference is VERY important. If all I have to do is have the highest and lowest point of the entire bumper be equal distances from 6.5, then this is an easy met condition. However, if EVERY section of the bumper must have its highest and lowest point equal distances for 6.5 inches, this is a Very tough rule to follow.
Rereading the rule in question (M6), I now wonder about many other things that I may have gotten wrong.
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Does the bumper have to be fastened with ‘bolts with recessed heads’ or are other fastening methods acceptable?
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Does the mounting surface of the robot have to be PRECISELY at the edge of the robot as shown in the figure or may we mount to our robot frame somewhere a bit inboard?
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My last question involves the definition of ‘energy absorbing material.’ I have heard of strength of materials Profs, who started each lecture with the question, ‘What happens when a fly lands on an anvil?’ The answer that the class was required to recite was, ‘It deflects’ (‘It’ in this case referring to the anvil.) The point was that regardless of how strong a beam seems, it bends when loaded without regard to the magnitude of the load. Ah well, I have gone far afield, my point is that, one man’s energy absorbing material is another man’s anvil! So… Would a ‘hoop skirt’ type affair made from thin walled aluminum tubing qualify as an ‘energy absorbing material’ or not? How about sheet of 0.020 thick aluminum formed into some (hopefully legal) shape?
Finally, I think that this is going to be VERY hard to judge fairly & consistently what is legal and what is not.
So… I beg that FIRST reconsider the interpretation of the rule that is has currently proposed in favor of a rule that basically allows teams to put whatever they want in the envelope defined (not material limits on stuff inside the bumper zone) but the bumper must be rigidly fixed to the robot (no moving bumpers) and a team must be able to remove & re-install it in less than XXX minutes.
What do you think?
Joe J.
Posted by Joe Johnson. [PICTURE: SAME | NEW | HELP]
Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.
Posted on 1/28/2000 8:33 PM MST
In Reply to: Bumper issues (long & complex) posted by Joe Johnson on 1/28/2000 5:35 PM MST:
Here is another thought and a reason for FIRST to reconsider this ‘vertically centered about 6.5 inches’ idea:
For the veteran teams, think back to any game with rubber balls. How many times have you seen teams design robots that contact a ball at or above the tangent point of the ball? Just about as many times as you have seen a machine that could not push a ball out of the way and ended up having to drive AROUND balls rather than face the embarassing truth – a ball in the way may as well be a mountain, go around it 'cause we ain’t going to push it out of our way.
If it were not so unfunny it would be hilarious. It was not uncommon to find a machine unable to move in a sea of balls because a ball was in front of them and another had rolled behind them. They were stuck in the middle with no way of pushing the balls out to the way because they did not contact the ball below the center of the ball. If they did try to push a ball, they rolled up on top of it causing them to loose traction and sometimes even flipping them over. In fact, we won a match in the semi-finals due to this exact problem in 1998.
Anyway, my point is that FIRST is sort of requiring teams with bumpers to face this problem. The problem will be especially bad with bumpers that are like the one shown in the example in the rules (if the energy absorbing material is somewhat grippy, they don’t stand a chance in this game).
Just my two cents worth.
Joe J.
Posted by Nate Smith.
Other on team #66, GM Powertrain/Ypsilanti HS/Willow Run HS, from Eastern Michigan University and GM Powertrain.
Posted on 1/28/2000 9:54 PM MST
In Reply to: And another thing… posted by Joe Johnson on 1/28/2000 8:33 PM MST:
: In fact, we won a match in the semi-finals due to this exact problem in 1998.
: Just my two cents worth.
: Joe J.
I think I remember seeing this round on one of the videotapes from '98…luckily, it wasn’t our machine with that problem(we had a ‘scoop’ on the front of the machine that, among other things, helped us position the balls for our arm to get them), but I remember seeing this problem come up a few times, and with the smaller balls this year, I would recommend a very low frame, in order to prevent balls getting stuck behind your machine as you try to back up.
Nate
Posted by Thomas A. Frank.
Engineer on team #121, The Islanders/Rhode Warrior, from Middletown (RI) High School and Naval Undersea Warfare Center.
Posted on 1/29/2000 3:32 PM MST
In Reply to: And another thing… posted by Joe Johnson on 1/28/2000 8:33 PM MST:
> of the way and ended up having to drive AROUND balls >rather than face the embarassing truth – a ball in
>the way may as well be a mountain, go around it 'cause >we ain’t going to push it out of our way.
Hi Joe;
We’re the one’s who posited the question because of this exact problem, and because all we really wanted to use was a little piece of rubber boat fender (sort of like the rubber gasketing that goes under garage doors).
Now that Eric has made it clear that the bumpers are just another little FIRST engineer trap (like the pneumatics tend to be for the inexperienced:-)), we’re going to skip this bumper nonsense and just build a strong side.
TAF
Posted by Michael Betts.
Engineer on team #177, Bobcat Robotics, from South Windsor High School and International Fuel Cells.
Posted on 1/30/2000 9:35 AM MST
In Reply to: Re: And another thing… posted by Thomas A. Frank on 1/29/2000 3:32 PM MST:
I agree with Messrs. Frank and Johnson. The bumpers, in their present ‘configuration’, will definitely cause driving problems when they encounter the balls.
It is highly unlikely that this year’s Bobcat will have bumpers… It’s just asking for trouble.
My advise to rookie teams, don’t waste precious time and effort to develop bumpers. If at all possible, it as far better to build a ‘bulletproof’ robot.
Posted by Ken Patton. [PICTURE: SAME | NEW | HELP]
Engineer on team #65, The Huskie Brigade, from Pontiac Northern High School and GM Powertrain.
Posted on 1/30/2000 2:02 PM MST
In Reply to: Re: And another thing… posted by Michael Betts on 1/30/2000 9:35 AM MST:
We haven’t really wanted a bumper as of yet. Its possible we might have one on one side of the robot, but so far it seems to create more problems than its worth.
Ken
Posted by Scott Strickland.
Engineer on team #21, ComBBAT, from Astronaut & Titusville High School and Boeing/NASA.
Posted on 1/28/2000 8:34 PM MST
In Reply to: Bumper issues (long & complex) posted by Joe Johnson on 1/28/2000 5:35 PM MST:
I think you have to look at the context in which the question was asked. The rules look unchanged to me.
They asked if they could use a smaller bumper than the envelope and if it could be positioned at the bottom of the envelope. Answer: Yes and No.
The bumper must fit within the envelope specified by the original rules. If it is smaller, it must be on the centerline of the envelope specified. It must be removable. It must be stationary (and be on a ‘fixed’ portion of your robot).
The material of the bumper can be anything (I think even stuff not allowed for the rest of the robot), but it counts against you for weight. Anvils are usually very heavy!
Anyway, that’s the way I see it. I guess it’s not so short and simple after all.
Scott
Team 21 ComBBAT
Posted by Jan Enderle.
Engineer on team #191, X-Cats, from Wilson Magnet High School and Xerox.
Posted on 1/31/2000 10:35 AM MST
In Reply to: Bumper issues (long & complex) posted by Joe Johnson on 1/28/2000 5:35 PM MST:
Has anyone ever seen or been involved in a rear-end accident where both cars brake hard, and massive damage ensues? You know the kind - where it takes some doing to get the cars apart afterwards?
Have you heard insurance companies talking about inreasing the rates for SUV’s because the accidents they are in with sedans are very costly?
The common element here: mismatched bumpers.
I believe the intent of FIRST in requiring all bumpers to be centered at 6.5’ is to get everyone’s bumpers at the same height. Is 6.5’ the right height relative to the centerline of the balls, and the issue of getting caught up on them? I’m not sure - we’ll have to do some experimenting before we decide what to do.
Posted by Dodd Stacy.
Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.
Posted on 1/31/2000 7:54 PM MST
In Reply to: Re: Bumper issues (long & complex) posted by Jan Enderle on 1/31/2000 10:35 AM MST:
>Is 6.5’ the right height relative to the centerline of the balls, and the issue of getting caught up on them? I’m not sure - we’ll have to do some experimenting before we decide what to do.
The frictional interaction of the ball with the floor and the robot can be so squirrely as to really make you wonder about your grasp of the physics. In Orlando in 1998, we backed up against a loose (20’) ball on the floor and the rear end of the robot was lifted off the floor.
Considering that the back of our machine was a flat lexan panel inclined forward (away from the ball) about 15 degrees, I still don’t see how the ball ‘crammed,’ but it did. And that was repeatable.
Also be aware that your experimenting needs to include temperature/humidity conditions similar to Orlando to cover the design envelope. Those balls get positively sticky.
Dodd
Posted by Nate Smith.
Other on team #66, GM Powertrain/Ypsilanti HS/Willow Run HS, from Eastern Michigan University and GM Powertrain.
Posted on 1/28/2000 8:08 PM MST
In Reply to: Team Update #6 is Out! posted by Eric Rasmussen on 1/28/2000 4:12 PM MST:
For those of you who may be a little confused after reading the messages in the Tech forum regarding the Dashboard Decoder project that I have been working on, and now seeing the information on it in Update 6, let me just clarify some of the information:
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There is a dashboard decoder program, written in Visual Basic 6.0 and packaged as an OCX, available at http://www.hollandfirstrobotics.com/dash_beta/finalrev2/. The source code for the OCX is also available at that site.
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My current team is Team 66, GM Powertrain Group and Willow Run High School. For the '98 and '99 competitions, I was with Team 74, and still work with them on their web site. They allowed me to use a portion of the site in order to provide a place for the program to be downloaded from. I am also working on uploading the program to the team066 section of SharingFIRST.
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Despite the appearance of the URL from which the program can be currently downloaded, the version available is the official release version. It was simpler to use an existing directory and just update the files on the server than it was to create a new directory for the release version.
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I am glad to help teams with any problems they run across while attempting to program their custom dashboard application. For help, e-mail me at njsmith@online.emich.edu.
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If you use the OCX without modification, I ask that you credit my work as follows in an ‘about box’ to the program. This information can be in addition to any that you add personally:
Decoder Library by Nate Smith
E-Mail: njsmith@online.emich.edu
Team 66 - GM Powertrain & Willow Run HS
Decoder Library OCX Version 1.0
Any other questions? Just drop me an e-mail…
Nate Smith