Robot Speeds - Opinions sought

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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 2/7/2000 9:16 AM MST



Hello All;

I'm assuming that most of you have a running chassis by now.

When we started out this year, we theorized that the vast
majority of teams would fall into the 4-6 feet per second
range, or about 8-12 seconds to cross the field, and designed
accordingly.

Did we guess correctly?

Tom Frank

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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 2/7/2000 1:17 PM MST


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



4-6 feet per second...

hmm...

okay, with an 8 inch wheel thats about 2-3 rev per second or 120-180 RPM

The Drill motors has a free speed of about 20,000 RPM so...

From Drill motor to 8 inch wheel we'd be talking about a 170-110 to 1 ratio.

I suppose that is about right.

With the transmission in low that would mean about a 2 or 3 to 1 ration from the output of the drill trans to the wheel.

Every year I tell a bunch of rookie teams that your robot shouldn't be able to out-run you, but it should probably be able to make you walk kind of fast. Somewhere in between is the right ratio.

The 4-6 ft per second falls into that range.

What ratio will Chief Delphi V have? Not ready to commit yet ;-)

Joe J.

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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 2/7/2000 3:50 PM MST


In Reply to: guessing on ratios posted by Joe Johnson on 2/7/2000 1:17 PM MST:



Our robot is going be fast, and powerful too. Faster than anything you've mentioned so far. (without shifting the drill trannys) How you ask? Not tellin' !

Tom Wible
Team #131

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Posted by Dodd Stacy.

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

Posted on 2/7/2000 4:16 PM MST


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



We've set up to change our main drive wheel gear ratio fairly easily, a la bicycle derailleur (?) - 2 variable ratios in series. Top speed depends only on what we find our drivers are able to control, for all practical purposes. A second pair of motors, direct drive at relatively low ratio to a second pair of wheels through over running clutches, provides traction-limited acceleration off the line, for when the main drive is geared tall. We're looking forward to interesting drag races for the balls at the far end.

Dodd

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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 2/7/2000 5:04 PM MST


In Reply to: Ditto posted by Dodd Stacy on 2/7/2000 4:16 PM MST:



Dodd,

I have long been in awe of the machines out of Lebanon Robotics!

From the amazing ball extruder you had in Ladder Logic to the Omni Directional Goal Emptier you had at the Rumble last year, you never fail to impress me.

I am sure that this year will be no different.

As to the over-running cluthes, do they work in reverse as well? What happens to your machine if you try to back up? I would think that the slower motors may make you kind of creepy in reverse.

Am I missing something?

Joe J.

P.S. Perhaps you should write a book about all the clever mechanism you have put on your machines over the years. It would be a thick volume as well as a best seller (at least in the FIRST community). Think about it.

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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 2/7/2000 7:28 PM MST


In Reply to: Leave it to Lebanon posted by Joe Johnson on 2/7/2000 5:04 PM MST:



I'm with Joe 100% on this one! Every machine produced by your team had never failed to amaze me. I remember the first time we realized that our doublers were disapearing in 1998! Talk about shock! And you saved us last year at Rumble. I look forward to yet another ingenious machine from you guys!

Lora

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Posted by Andy Grady.   [PICTURE: SAME | NEW | HELP]


Coach on team #42, P.A.R.T.S, from Alvirne High School and Daniel Webster College.

Posted on 2/7/2000 10:37 PM MST


In Reply to: Re: Leave it to Lebanon posted by Lora Knepper on 2/7/2000 7:28 PM MST:



Definately alot of credit to Lebanon, I don't know what was more impressive, their unbelievable multi directional drive system, or the even more unbelievable puck tipping mechanism. One of the matches that stuck out most in my mind was when lebanon was tiping the puck at an angle that looked to be nearing 45 degrees on Assabet at River Rage last year. They were definately among my top 10 favorite teams to watch last year, i can't wait to see what tricks they have up their sleeves this year.
Good Luck all,
Andy Grady, DWC/Alvirne

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Posted by Dodd Stacy.

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

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


In Reply to: Leave it to Lebanon posted by Joe Johnson on 2/7/2000 5:04 PM MST:




: As to the over-running cluthes, do they work in reverse as well? What happens to your machine if you try to back up? I would think that the slower motors may make you kind of creepy in reverse.

: Am I missing something?

: Joe J.

As usual, Dr. Joe misses nothing, sees right through the smoke screen. I guess it was the clutches that tipped you off. OK, I'll come clean - it's actually a retrohyperdrive for achieving warp speeds in reverse. We rewound the low speed (Globe) motors with HTS wire and immerse them in liquid nitrogen. Then when the high speed main (drill) motors overdrive the Globes in reverse, through those pesky clutches, the Globes become superconducting generators. We couple the Globe output back to the drill inputs through multiple #6 wire direct shunts, and the whole thing just goes faster and faster till our watches slow down and everybody starts talking slow with real deep voices. One of the kids dreamed it up after my lecture about perpetual motion machines.

Actually, this year we're 'just' trying for a modest offensive competance, something we haven't given enough attention in past years, in our shameless efforts to entertain. I admire every team that shows up with a rolling robot, and I really respect the teams and machines that consistently and reliably play the game well and quickly and put the numbers on the board. And then, one (or two, or three) of them are the champs. Sounds so simple. Is so hard.

Good luck, everybody.

Dodd

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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 7:21 AM MST


In Reply to: Ditto posted by Dodd Stacy on 2/7/2000 4:16 PM MST:



That will be the trick this year: the ability to change to a lower gear on the fly. Kudos to you and your team, Dodd!

We were trying to go with a CVT (continuously variable transmission)... but without success. We bailed on the CVT due to some many losses in the system. It works, but there is too much friction and some binding between the toroidal plates.

What this CVT would've done is have constant acceleration... we figured that it could've run into the far wall (48 feet away) at 20 mph.

We'll have the contraption in our pits at the competition... please come by and take a look, 'cause you'll probably see it on our 'bot in 2001 (depending on field size).

Andy B.

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Posted by Dodd Stacy.

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

Posted on 2/8/2000 9:02 AM MST


In Reply to: Way to Go! No CVT for us posted by Andy Baker on 2/8/2000 7:21 AM MST:



: That will be the trick this year: the ability to change to a lower gear on the fly. Kudos to you and your team, Dodd!

Andy, sorry I must have overstated. We can't shift on the fly. It's the old fashioned way, changing sprockets in the pits. With the drill gearbox (which we prefer to run in high) in series with a chain and sprocket pair, we chose two different driving sprocket sizes that give a reasonable spread of the 4 ratio steps between low-low and high-high. We just decided to make that easy to do for once. It's only 'quick change' compared to drifting and driving pins. I'm assuming we'll settle on an overall ratio during test/practise/break/fix 'week' and leave it there.

Dodd

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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 2/8/2000 10:02 AM MST


In Reply to: Way to Go! No CVT for us posted by Andy Baker on 2/8/2000 7:21 AM MST:



: We were trying to go with a CVT (continuously variable transmission)... but without success. We bailed on the CVT due to some many losses in the system. It works, but there is too much friction and some binding between the toroidal plates.
---------------
Dear Dodd;

I find the fact that you folks built a prototype and had it working is amazing in itself! I anxiously look forward to seeing it.

We thought about such things for a few brief moments, and realized that it was well beyond our ability to construct in the time available, and went for conventional.

That teams are even considering such things, much less building them and trying them out, is what brings me back to FIRST year after year. It's sort of like being inside a living version of Popular Science from the 50's and 60's...FIRST demonstrates quite clearly the amazing things that can happen when the creative talents of engineering community are unleashed.

Tom Frank

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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 2/8/2000 10:06 AM MST


In Reply to: Re: Way to Go! No CVT for us posted by Thomas A. Frank on 2/8/2000 10:02 AM MST:



Dear Dodd;

Meant Dear Andy...

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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 9:24 PM MST


In Reply to: Re: Way to Go! No CVT for us posted by Thomas A. Frank on 2/8/2000 10:02 AM MST:



Tom,

We'll have it at the competitions (MI, IL, Epcot), but it's designer will not be able to make it. Our multi-talented ME/EE Mark Koors will be in Haiti on missionary work during our Regionals and on a family vacation during Nationals.
BUT, I'll be taking notes about what all of you think of this contraption and how to make it better.

Andy B.

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Posted by Jon.

Engineer on team #190, Gompei, from Mass Academy of Math and Science and Worcester Polytechnic Institute.

Posted on 2/8/2000 8:17 AM MST


In Reply to: Ditto posted by Dodd Stacy on 2/7/2000 4:16 PM MST:



We're building a DualSpeed system as well, but all i can say is that we will not be using a deraileur design...
all other details are classified... for now...
New Jersey, Hartford, then the World!

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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 2/8/2000 8:34 AM MST


In Reply to: Ditto posted by Dodd Stacy on 2/7/2000 4:16 PM MST:



Hmmm, seems like a lot of people are going for two(or more) speed drive trains right now...unfortunately, that's all I can say at this time...