Robot Speeds - Opinions sought

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Posted by Greg Mills.

Engineer on team #16, Baxter Bomb Squad, from Mountain Home and Baxter Healthcare.

Posted on 2/8/2000 10:29 AM MST


In Reply to: The Year of the Shifter posted by Nate Smith on 2/8/2000 8:34 AM MST:



:
A strange world - we have been shifting since '96 and have always had a high & low - until this year. We are going the other way - back toward a robust, reliable, single speed system. Not super fast - a little over 8fpm - but highly controllable and alot of powered wheels on the floor.

That is what is great about going to the competitions - seeing what everybody else thinks is the best way.

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Posted by Greg Mills.

Engineer on team #16, Baxter Bomb Squad, from Mountain Home and Baxter Healthcare.

Posted on 2/8/2000 11:45 AM MST


In Reply to: Re: The Year of the Shifter posted by Greg Mills on 2/8/2000 10:29 AM MST:



: :
: OK - OK try 8 fps - I was off by a factor of 60

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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 2/8/2000 2:06 PM MST


In Reply to: Re: The Year of the Shifter posted by Greg Mills on 2/8/2000 11:45 AM MST:



I don't know what you folks are thinking but if what I read here is any indication, a lot of you are heading for a world of hurt (imho -- Greg Mills, Baxter Mountain Home, and other bastions of sanity excluded as usual).

If you are talking about gear ratio where you realistically expect to reach 20mph I think you're crazy.

Shifting is tricky business, not for the faint of heart.

20 mph is way to fast to actually control unless you are in a parking lot somewhere (again imho).

Also, do you realize what rpm an 8 inch wheel has to spin at to go 20MPH? 840rpm!!!!

We are talking about a 25:1 ratio from the armature of the drill motor to an 8 inch wheel!!!

If any team uses such a low ratio, I predict that either the Victors or the Motors or both will literally catch fire at some point during the competion.

(Teams bold enough to shift on the fly are free to tell me that they told me so, but I don't expect a lot of teams to actually be able to carry this off effectively).

Shut my mouth at the Nationals.... Until then, I will remain skeptical about 20 mph robots.

Joe J.

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Posted by Kevin Sevcik.

Other on team #57, Tigers, from BT Washington and the High School for Engineering Professions and Exxon, Kellog Brown & Root, Powell Electrical.

Posted on 2/8/2000 2:33 PM MST


In Reply to: Try this: Year of the Flaming Victor (or Motor) posted by Joe Johnson on 2/8/2000 2:06 PM MST:



Actually, I think it'd be interesting to see a robot going 20 mph. I mean, imagine what would happen if they had to go over the ramp at that speed. :^) I think a robot goind at that speed is either going to have to be a limbo bot, or really robust and well balanced.

Kevin Sevcik

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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 2/9/2000 9:25 AM MST


In Reply to: Try this: Year of the Flaming Victor (or Motor) posted by Joe Johnson on 2/8/2000 2:06 PM MST:



: If you are talking about gear ratio where you realistically expect to reach 20mph I think you're crazy.


Thank you Joe, for confirming my engineering opinion/overall suspicion. If anyone succesfully breaks the 10 fps avg velocity barrier (on the field, over the 48 feet, at full match weight), I'll be very impressed (amazed might be a better word) indeed.

In fact, if any team achieves 12 fps average for the full field length (4 seconds wall to wall, full match weight, we'll let FIRST be the judge), I'll personally bring that team a case of soda (aka pop for you mid-westerners; their choice of brand) the following day!

Tom Frank

P.S. - I'd say the motors will ignite before the Victor's...

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Posted by Dodd Stacy.

Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.

Posted on 2/9/2000 9:31 PM MST


In Reply to: Try this: Year of the Flaming Victor (or Motor) posted by Joe Johnson on 2/8/2000 2:06 PM MST:



I hate to be a wet blanket on the 20 mph robot business, but let's put some numbers on that. A 130 lb robot traveling 20 mph possesses a kinetic energy in excess of 2,000 Joules (sorry about the mixed units, but this is America). I believe Joe has cast the drill motors as about 250 watts (J/sec) of max power output each. Postulate lossless CVT transmissions that allow the two drill motors to run always at their peak power rpm as the robot accelerates from rest to 20 mph. We need 4 seconds for 500 watts worth of motor to increase the kinetic energy of the robot by 2,000 Joules, to accelerate from rest to 20 mph.

Anyone care to calculate whether the robot will achieve the 20 mph velocity before hitting the end wall?

Dodd

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Posted by Dodd Stacy.

Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.

Posted on 2/10/2000 10:05 AM MST


In Reply to: Reality Check posted by Dodd Stacy on 2/9/2000 9:31 PM MST:




: Anyone care to calculate whether the robot will achieve the 20 mph velocity before hitting the end wall?

OK, time's up. Our highly idealized 130 lb dragbot with 500 w lossless CVT drive hits the end wall at just under 15 mph about 2.6 seconds after the start. There's a brief period of wheelspin (0.05 sec) at the start, during which the bot travels 0.03 ft and gets up to 1.9 mph before hooking up for the rest of the sprint. So don't bet your pink slip on a 20 mph trap speed.

I will buy a case of cola (or?) for any team whose bot can touch the balls at the far end of the field within 4 seconds after it moves from the starting position. (And I'll help scrape the bot off the end wall, too.)

I'll also wager no bot will clear the downslope of the ramp in the air, ie; land on the floor - not the ramp - after crossing the peak of the ramp. The gauntlet's down!

Dodd

(Disclaimer: Professional drivers shown on closed course. Do not attempt with your bot.)

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Posted by Joe Ross.   [PICTURE: SAME | NEW | HELP]


Coach on team #330, Beach Bot 2000, from Hope Chapel Academy and NASA/JPL & J&F Machine.

Posted on 2/10/2000 2:35 PM MST


In Reply to: SPLAT! posted by Dodd Stacy on 2/10/2000 10:05 AM MST:



Before we changed our gear ratios, we timed 3.8 seconds from starting position until we were stopped at the other end, for our 120 lb robot

We don't have new times yet and we didn't try to go over the ramp.

FYI no drill motors were harmed!

Joe Ross
Team 330


: I will buy a case of cola (or?) for any team whose bot can touch the balls at the far end of the field within 4 seconds after it moves from the starting position. (And I'll help scrape the bot off the end wall, too.)

: I'll also wager no bot will clear the downslope of the ramp in the air, ie; land on the floor - not the ramp - after crossing the peak of the ramp. The gauntlet's down!

: Dodd

: (Disclaimer: Professional drivers shown on closed course. Do not attempt with your bot.)

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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 2/23/2000 3:31 PM MST


In Reply to: SPLAT! posted by Dodd Stacy on 2/10/2000 10:05 AM MST:




: I will buy a case of cola (or?) for any team whose bot can touch the balls at the far end of the field within 4 seconds after it moves from the starting position. (And I'll help scrape the bot off the end wall, too.)

: I'll also wager no bot will clear the downslope of the ramp in the air, ie; land on the floor - not the ramp - after crossing the peak of the ramp. The gauntlet's down!

Hi Dodd;

I made the same wager (on the four seconds). I expect to have to pay off.

You see, our machine achieved both of the criteria you set forth above. Unfortunately, the power needed was so high that it had really bad effects on the drivetrain (I'll bring some of the stripped gears with me), battery (life expectancy was very low), and main fuse (it was getting HOT), and the drivers found it almost uncontrollable, so we detuned it to a much more reasonable level.

Now what we lack in speed we more than make up for in pushing power :-)

I miss the flying...

Tom Frank

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Posted by Dodd Stacy.

Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.

Posted on 2/23/2000 6:14 PM MST


In Reply to: Re: SPLAT! posted by Thomas A. Frank on 2/23/2000 3:31 PM MST:




: Hi Dodd;

: I made the same wager (on the four seconds). I expect to have to pay off.

: You see, our machine achieved both of the criteria you set forth above. Unfortunately, the power needed was so high that it had really bad effects on the drivetrain (I'll bring some of the stripped gears with me), battery (life expectancy was very low), and main fuse (it was getting HOT), and the drivers found it almost uncontrollable, so we detuned it to a much more reasonable level.

: I miss the flying...

: Tom Frank

Tom,

You guys did it, you win the bet. Name your sugar water. We'll settle at Rutgers or in Orlando, wherever we see the fabulous (ex) flying Rhode Warrior 2000 first. Bravo Zulu!

Dodd

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Posted by Tom Wible.   [PICTURE: SAME | NEW | HELP]


Coach on team #131, chaos, from central high school manchester and osram-sylvania.

Posted on 2/9/2000 7:14 PM MST


In Reply to: Re: guessing on ratios posted by Tom Wible on 2/7/2000 3:50 PM MST:



We will be having a two speed robot, without shifting anything! The low speed will be for pushing, and the high speed for getting around town. I can't wait to see it hit the ramp in Hartford!

Tom Wible
Team C.H.A.O.S.

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Posted by Andy Baker.

Engineer on team #45, TechnoKats, from Kokomo High School and Delphi Automotive Systems.

Posted on 2/8/2000 7:12 AM MST


In Reply to: Robot Speeds - Opinions sought posted by Thomas A. Frank on 2/7/2000 9:16 AM MST:



Tom,

I think that you're guessing too low. I think that there will be some teams at 15 fps (10 mph) and the majority at 6-8 fps.

Reminder to all teams: don't even think about running your drive base around without weighing it down to the maximum weight of 130 lbs. Get some boxes of screws or something and send them for a ride on your drive base. You will find out very soon if the carpet is your friend or enemy.

Use plenty of duct tape... those boxes will want to fall off!

Good luck,
Andy B.

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Posted by Lora Knepper.

Student on team #69, HYPER (Helping Youth Pursue Engineering & Robotics), from Quincy Public Schools and The Gillette Company.

Posted on 2/8/2000 4:14 PM MST


In Reply to: Remember to WEIGH IT DOWN posted by Andy Baker on 2/8/2000 7:12 AM MST:



I second that from experience. Not only does it show how you affect the carpet, but it also gives you a pretty good idea on how your 'bot will handle. From just driving a proto base, to a fully loaded robot, nothing usually handles more differently. This is especially essential if your drivers won't have a lot of practice time.

Lora

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Posted by Nate Smith.

Other on team #66, GM Powertrain/Willow Run HS, from Eastern Michigan University and GM Powertrain.

Posted on 2/10/2000 12:51 PM MST


In Reply to: Re: Remember to WEIGH IT DOWN posted by Lora Knepper on 2/8/2000 4:14 PM MST:



Speaking from experience...if you're going to add weight to your machine, make sure to put it where it can be anchored securely. Also, try not to have any of the weight outside the footprint of your machine...if you hit something with your extra weight and it shifts that weight, who knows what it's going to hit?

Nate

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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 2/8/2000 10:13 AM MST


In Reply to: Robot Speeds - Opinions sought posted by Thomas A. Frank on 2/7/2000 9:16 AM MST:



I think there will be a lot of teams going faster than that. We are planning to be pretty fast for the initial drag race across the field.

Ken