What else do we want?

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Posted by Andy Baker.

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

Posted on 6/22/2000 7:12 AM MST



Last year, FIRST asked the question: 'what else do you want to use to build your robots?'

We said that we wanted more freedom with gears, sprockets and belts... we wanted more freedom with materials... and we wanted the ability to use aluminum extrusions.

And FIRST delivered! I think that they suprised us all when they allowed us these freedoms.

So, now I ask...

What else do we want?

Unlimited bearing use?
More freedom with plastics?
To be able to use ANY adhesive?

What do YOU think?

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 6/22/2000 7:51 AM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



Andy,

I think we should have complete freedom with the mechanical output of the armature for ALL of the motors in the kit. I've never understood why we should be restricted to leaving the worm gear output unaltered on the door, window, and seat motors.

I agree with limiting the performance envelope by allowing only use of motors supplied in the kit. That's like limiting size and weight. But we should be able to treat stators and rotors as components, as long as we don't begin rewinding, changing magnets, etc., ie: changing the performance curves. (Other than staying in the cooler parts of the map. We should be able to use as many cooling fans as we want, too - not for thrust, tho', Joe)

Teams with lots of people/time/shop/$ resources can go off and really optimize the application of these little motors' performance potential to the FIRST game task at hand, and less endowed teams can continue to innovate with methods for mounting and adapting the wormed-down output from these fairly stout and reliable packaged units. Put the two different bots head to head in a match, and who knows how it will go?

My 2 cents. I'll probably expand the wish list.

Dodd

: Last year, FIRST asked the question: 'what else do you want to use to build your robots?'

: We said that we wanted more freedom with gears, sprockets and belts... we wanted more freedom with materials... and we wanted the ability to use aluminum extrusions.

: And FIRST delivered! I think that they suprised us all when they allowed us these freedoms.

: So, now I ask...

: What else do we want?

: Unlimited bearing use?
: More freedom with plastics?
: To be able to use ANY adhesive?

: What do YOU think?

: 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 6/22/2000 3:01 PM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



Ok, I think duct tape is a definte must....it has so many uses!! And talk about a quick fix on the field..hmmm..... =)

Lora

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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 6/27/2000 3:41 PM MST


In Reply to: Duct Tape!! posted by Lora Knepper on 6/22/2000 3:01 PM MST:



I think that a rule modification that would allow tape as long as it is not in view is overdue.

I have heard that Woodie is sort of an anti-duct tape zealot, but I think that the competition has progressed to the point that we can allow the use of tape without fear of machines totally taped together.

I think it would be reasonable to allow tape but only if it is not visible during the operation of the machine.

This addresses the cosmetic concerns I think FIRST worried about without tieing our hands when a piece of double sided tape is the right answer for the job.

Thoughts?

Joe J.

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Posted by Matt Leese.

Student on team #7 from Parkville High School and NASA, Black & Decker, AAI, Raytheon.

Posted on 6/22/2000 8:35 PM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



Personally I'd like to see more sensors. Including them in the kit would be fine too. I think some sort of timing device and ampmeter would be great. Can you tell I work on the control system?

Matt

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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 6/23/2000 8:21 AM MST


In Reply to: Re: What else do we want? posted by Matt Leese on 6/22/2000 8:35 PM MST:



: Personally I'd like to see more sensors. Including them in the kit would be fine too. I think some sort of timing device and ampmeter would be great. Can you tell I work on the control system?

: Matt

I know that since this message has the word 'rumors' in the title, it should be in the other board, but anyway...when I was talking with some of the Innovation First folks as they were packing up in Florida this past year, they mentioned a few new sensors and other things being in the works...that's all I know, so that's all I can say...

Nate

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Posted by Justin Stiltner.

Student on team #388, Epsilon, from Grundy High School and NASA, American Electric Power, Town of Grundy.

Posted on 6/23/2000 5:52 PM MST


In Reply to: Rumors of Sensors for 2001 posted by Nate Smith on 6/23/2000 8:21 AM MST:



Some more pnumatic gear would be nice maby a $ amount that you can order from smc kinda like the small parts stuff. Also bring back the Compressor and maby a small air tank. I think that this year The weight of that tank and the limited Cylinders avalible made the pnumatics not evean an option for some teams. 24 Volt Motors and an extra battery would be nice.
Justin Stiltner
Team #388
Epsilon
Grundy Va,

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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 6/23/2000 7:24 PM MST


In Reply to: Re: Rumors of Sensors for 2001 posted by Justin Stiltner on 6/23/2000 5:52 PM MST:



a smaller compressor would definitely be a good thing... plus a smaller tank... that was way too big unless you expressively decided to build around it...
a kompressor would be nice to bring back.

jon 190

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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 6/27/2000 3:35 PM MST


In Reply to: Re: Rumors of Sensors for 2001 posted by Jon on 6/23/2000 7:24 PM MST:



Two very obvious improvements would be to be able to know wheel speed and to know ground speed.

With sensors like these we could do some very interesting traction control stuff -- not to mention the idea of having the joysticks control wheel speed rather than the voltage at the motor. This would allow folks to get around all those silly schemes folks use to get their beloved robot to drive straight ;-)

AND WHILE I AM AT IT...

a current sensor or four would be a very very useful addition to the above sensors. Using wheel speed and current together with the known input voltage would allow us to get maximum performance from our motors without having to risk an overzealous driver in the heat of the battle turning the drive motors into toasters!

AND ONE MORE THING...

A temp. sensor could be nice too -- same idea -- detecting and avoiding smoking motors.

Joe J.

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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 6/30/2000 9:14 AM MST


In Reply to: wheel speed & ground speed sensors.. ..and a current sensor posted by Joe Johnson on 6/27/2000 3:35 PM MST:



: Two very obvious improvements would be to be able to know wheel speed and to know ground speed.

Hello All;

I agree wholeheartedly with Joe - these things would be great. They are also surprisingly easy to implement...so I've suggested to FIRST that maybe they should allow us the use of any off the shelf analog or digital IC (maybe specify the catalogs we can use)...with a frequency to voltage converter IC and a reed switch on a shaft, we get RPM (speed) as a DC voltage which can be input directly to the RI analog port...current sensing can be done with a coil and an op-amp with some filter caps (current shunts are a bad idea if you plan on inputing to the RI)...a photo transistor could be used as a trigger for things...it would be more fun for the EE's... :-)

Tom

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Posted by Matt Leese.

Student on team #7 from Parkville High School and NASA, Black & Decker, AAI, Raytheon.

Posted on 7/1/2000 6:58 PM MST


In Reply to: Re: wheel speed & ground speed sensors.. ..and a current sensor posted by Thomas A. Frank on 6/30/2000 9:14 AM MST:



If they allow any IC's, someone's going to stick a Pentium onto the robot. Although that would be very cool it would give them a distinct advantage because of increased available computing power (and ease of programming...am I the only one who hates PBasic?). What I'd like is a C Compiler for the RC. Well, one can wish can't he?

Matt Leese

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Posted by Adam Krajewski.

Student on team #68, Truck Town Terror, from Walled Lake Central High School and General Motors Truck Group.

Posted on 7/2/2000 11:44 PM MST


In Reply to: Re: wheel speed & ground speed sensors.. ..and a current sensor posted by Matt Leese on 7/1/2000 6:58 PM MST:



What I'd like to do is to tap into the power of SX-Blitz on the Robot Controller. Is that possible/legal on the Innovation FIRST controllers? THAT would help make loop times accurate enough to really tap into the power of the GyroChip for PID controls and physical models.

And my robot would be AMD Athlon Thunderbird powered. :)
Just think... By next year the AMD 760 chipset will be out... A SiMPy robot would be a work of art. :)
THEN we'll need the Freeze-It. :)

Adam

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Posted by Matt Leese.

Student on team #7 from Parkville High School and NASA, Black & Decker, AAI, Raytheon.

Posted on 6/25/2000 9:16 PM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



I forgot what is needed most of all in my previous post: a better cooling system.

I'm not sure about the other teams out there but I know my team had problems with drill motors (for the drive system) over heating. If we could have a better way to cool them on the robot it'd be much nicer (yes, I know better gear ratio's would help too....)

Matt

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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 6/27/2000 5:13 AM MST


In Reply to: Re: What else do we want? posted by Matt Leese on 6/25/2000 9:16 PM MST:



Hmmm, sound like 7 needed a way (and a rule to allow) to carry on board Freez-It =) ....

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Posted by Lloyd Burns.

Other on team #188, Woburn Robotics, from Woburn Collegiate and Canada 3000, ScotiaBank, Royal Bank Financial.

Posted on 6/27/2000 8:13 AM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



Personally, I've never understood why bearings should be in limited supply. I doubt if any commercial venture would tell the Engineering Department 'Well, make a machine to do this and this and that, but don't use many bearings ... company policy forbids more than three on any project.'

The other chafing point is the requirement to use 10 AWG for ALL the motor wiring, without supplying the limp 10 guage wire which would be useful for flexibility in the tight quarters around the connection to the motors. The manufacturers who supply wire with their motors usually don't supply 10 AWG, and last year I was very happy to be allowed to use Fisher Price wire on the FP motor; it had a right angle disconnect on it too, so that was one motor we didn't have to manufacture a rt. angle connection for.

(You could probably manufacture springs from the supplied 10 AWG, but by way of contrast, I found locally, some 4 AWG clear plastic wire that felt like the old headphone (tinsel) wire, it was sooooo limp.)

Lloyd

: Last year, FIRST asked the question: 'what else do you want to use to build your robots?'

: We said that we wanted more freedom with gears, sprockets and belts... we wanted more freedom with materials... and we wanted the ability to use aluminum extrusions.

: And FIRST delivered! I think that they suprised us all when they allowed us these freedoms.

: So, now I ask...

: What else do we want?

: Unlimited bearing use?
: More freedom with plastics?
: To be able to use ANY adhesive?

: What do YOU think?

: Andy B.

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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 6/27/2000 3:24 PM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



As for me, I am pretty happy with the kit as it is.

For my own selfish reasons, I would really like to have some electromechanical clutches & brakes. To my way of thinking, this would open up a whole new area of exciting mechanisms that would be possible.

How about a reliable shifting transmission? Clutches can make this more easily done.

How about a lift mechanism doesn't let you down after time expires? No problem with a brake in the kit.

What do you think?

Joe J.

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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 6/30/2000 9:16 AM MST


In Reply to: I vote for electromechanical brakes & clutches... posted by Joe Johnson on 6/27/2000 3:24 PM MST:



: For my own selfish reasons, I would really like to have some electromechanical clutches & brakes.

I'll second that motion also!

The ratchet we built for our extension mechnaism was a work of art, but I would have preferred something simpler.

Tom

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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 6/27/2000 3:48 PM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



I vote for more wheels.

How about a rule that allows any 'off the shelf' wheel (including casters) with a diameter under 10 inches?

This could make for some very cool looking robots. Think of all the bike wheels, tractor wheels, etc. that teams could use. Scan though the pages of McMaster just to get a feel for the variety that is out there.

Very cool -- I say bring it on.

Joe J.

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Posted by Jason Iannuzzi.

Engineer on team #11, Marauders, from Mt. Olive HS. and BASF, Rame Hart, CCM.

Posted on 6/30/2000 7:27 AM MST


In Reply to: Wheels Wheels Wheels posted by Joe Johnson on 6/27/2000 3:48 PM MST:



Yes, wheels!

I've never been a big fan of the wheelchair wheels, and it seems like such a waste of time to have to design/manufacture custom wheels. This seems like a no-brainer to me.

I'm starting to think they should dump the pneumatics. We actually used them this year, just for the challenge of course, but they seem like such a waste of space and weight. I'd rather see a few more motor options instead, maybe another high torque one. Sorry SMC.

Other than that, I'm pretty content. Removing the limit on the structural materials and gears/sprockets/chain was all I ever wanted.

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Posted by Andrew Rudolph.

Student on team NASA KSC/Michael Krop Senior High School from Michael Krop Senior High School sponsored by NASA Kennedy Space Centre.

Posted on 6/29/2000 6:17 PM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



Well i Feel that some good servo motors would be real handy..Not like the little Hobby servos im talking like the ones used on equipment... THey are very good for making small manipulator arms and such...

Andrew

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Posted by Justin Ridley.

Engineer on team #221, MI Roboworks, from Michigan Technological University.

Posted on 6/30/2000 10:08 AM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



I want all of these things. . . and you know what else. I want a couple more drill motors. Just think of having 4 of them in the kit. You could use all four of them in the drivetrain or if you didn't you would have two awsome motors to use somewhere else in the robot. I'm sure it won't happen, but it'd be nice. If not I think we're gonna need something similar to the drill motors only stronger. . .I think were getting close to weight limits these two motors are going to be able to throw around as hard as some teams do for two minutes. Maybe not. Then again maybe the wieght limit will continue to stay where it is. Either way I want two more motors :).

-Justin

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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 6/30/2000 7:33 PM MST


In Reply to: Re: What else do we want? posted by Justin Ridley on 6/30/2000 10:08 AM MST:



I could go for this in a big way. BUT... There are two issues that will have to be addressed.

#1) FIRST BUYS these motors more less at retail prices. This is one of the most expensive parts of the kit for FIRST. How would folks feel about FIRST allowing people to use the two in the kit plus 2 more that they could purchase as desired? This would be acceptable to me, but I know that many teams struggle to buy stuff for the robot. Having to buy $100 - $200 more may be a struggle for some teams. Your opinion?

#2) 60 Amp fuses are already a problem for a number of teams. There is a work around but it is not widely known (look for a whitepaper if FIRST does not provide a better fusing solution in 2001). Even the work around I have may be challenged with 2 more current hogs on board. What do you think about more teams blowing fuses and watching the rest of the match as spectators? Is this sort of a case where FIRST gives us enough rope to hang ourselves, but we are expected to be careful to avoid problems? It is okay by me. What do you think?

Joe J.

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Posted by Matt Leese.

Student on team #7 from Parkville High School and NASA, Black & Decker, AAI, Raytheon.

Posted on 7/1/2000 7:56 AM MST


In Reply to: 60 amp fuse problems... posted by Joe Johnson on 6/30/2000 7:33 PM MST:



The main problem I could see with this whole plan is that drill motors is that drill motors have varying strengths and this could give an advantage to teams that are able to spend more money on the drill motors themselves. Now if it was only limited to buying the same drill motors that come in the kit, that may work. I think that could be a good idea but it does give more of an advantage to those teams that can spend, yet again.

I really think that if you're blowing the 60 amp fuse you're really doing something wrong. It usually is symptomatic of bad wiring or bad motor outputs (i.e. bad ratio, etc.). I don't think the extra drill motors would add to this because I know many teams used two drill and two fisher price motors on the drive and didn't seem to have problems. I personally think this is more of a non-issue.

Matt Leese

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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 7/1/2000 8:41 AM MST


In Reply to: Re: 60 amp fuse problems... posted by Matt Leese on 7/1/2000 7:56 AM MST:




I know of a number 'good' teams that had problems in 1999 & 2000 with blowing 60 Amp fuses in the heat of battle.

I don't want to name names, but believe me it is possible to have things 'right' yet still draw enough current to blow that 60 amp fuse.

Adding two more 100+ amp stall load motors to the robot will only increase the number of teams that will blow that fuse.

Joe J.

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Posted by Matt Leese.

Student on team #7 from Parkville High School and NASA, Black & Decker, AAI, Raytheon.

Posted on 7/1/2000 6:53 PM MST


In Reply to: The drills are not FP or Delphi Power Sliding Door Motors... posted by Joe Johnson on 7/1/2000 8:41 AM MST:



I think the fact that they're 100+ amp stall motors should have little to do with it because the 30 amp circuit breakers should trigger before that. Also, I was under the impression that the drill motors were of higher quality meaning that overall they should draw less power for most use (correct me if I'm wrong). I haven't seen all that many fuses blow on the so called 'good teams' (I'd prefer not to use it as it sounds too elitist) but from what I've seen it tends to occur when those teams try to push their robots too hard. The 60 amp fuse just places a good limit on how far the robots can be pushed. It also helps to limit the amount of complexity of the robot because you can't really run every single motor provided or the fuse will blow.

Matt Leese, who thinks this discussion will go on for awhile now....

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Posted by Justin Stiltner.

Student on team #388, Epsilon, from Grundy High School and NASA, American Electric Power, Town of Grundy.

Posted on 7/1/2000 7:36 PM MST


In Reply to: Re: The drills are not FP or Delphi Power Sliding Door Motors... posted by Matt Leese on 7/1/2000 6:53 PM MST:



This is the way i see it
you have 10 motors and the rotating becon
that means if all the motors draw the same amount you have 5.45 amps for each motor not enough to run a robot very well... but most teams dont use all of them but most robots had 4 the drills and then 2 others which left you with 15 amps for each one &thats not including the becon or the control system or the speed controllers. I dont think that the fuse is big enough evean thow we have the 30amp breakers if you have one close to tripping and then 2 more at about half capacaty that would blow the fuse. I think we should have either 2 batterys or 2 fuses.

Just my 2 Cents

Justin Stiltner
Team #388
Epsilon
Grundy Va,

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Posted by Matt Leese.

Student on team #7 from Parkville High School and NASA, Black & Decker, AAI, Raytheon.

Posted on 7/2/2000 2:34 PM MST


In Reply to: Re: The drills are not FP or Delphi Power Sliding Door Motors... posted by Justin Stiltner on 7/1/2000 7:36 PM MST:



Well, obviously using all four drill motors would in no way be required. You could use none for all anyone would care. You'd have to engineer with trade-offs (isn't that more like the real world then?).

Adding a second fuse isn't going to do anything at all -- you have to use a higher amp fuse. They'd need to raise the weight limit if we were to use two batteries (they're at least 1/10th of the robot weight right now and there's no way you're packing a second one on). It'd also be much more of a pain to wire.

Matt Leese

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Posted by Justin Stiltner.

Student on team #388, Epsilon, from Grundy High School and NASA, American Electric Power, Town of Grundy.

Posted on 7/2/2000 7:50 PM MST


In Reply to: Re: The drills are not FP or Delphi Power Sliding Door Motors... posted by Matt Leese on 7/2/2000 2:34 PM MST:



What I ment by the second fuse was to have 2 main supply lines running different parts of a robot (the left side motors be on one and the right side motors be on another ect.)
but this is also like Dean said 'we give you too little time, too little resorces...' What I think it all boils down to is that it is an engineering challange to make your robot more efficent while still being effective. And im shure that the engineers know what I am talking about.

Justin Stiltner
Team #388
Epsilon
Grundy Va,

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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 7/3/2000 1:55 PM MST


In Reply to: Re: The drills are not FP or Delphi Power Sliding Door Motors... posted by Matt Leese on 7/1/2000 6:53 PM MST:



Let me begin by saying that I didn't mean to be elitist by the 'good' teams comment so much as I wanted to convey that it is not a problem with yahoo teams with no engineering help and no experience.
Believe me, there were a number of very well thought of teams with a number or regionals champ banners hanging in their gyms that ran into problems with the 60 amp fuse. That said, I also I know of a number of rookie teams that had difficulties as well.

As to your assessment that the drill motors are somehow of higher quality and that this higher quality allowing them to draw less current, this is just nonsense. The drill motors are motors just like any other in the kit. They follow the same laws concerning speed, torque & current that the other motors in the kit follow. As to quality, I would argue that other motors have higher quality based on my observations of % failures on FIRST robots.

To my mind, the drill motors have two significant differences from all the other motors in the kit that make the special:

#1 They are, by far, the most powerful motors in the kit (and, not coincidentally, they draw by far, the most current of any motor in the kit)

#2 They are the most difficult motor to mechanically interface to (specifically, the output shaft is difficult to reliably connect to & the overall shape of the housings makes the drills the most difficult motor to hold reliably).

After saying all this, I would actually welcome more of these motors in the kit. However, I am quite sure that without some help or a rules change, a lot of teams (veteran & rookie alike) will have 60 amp fuse problems.

Just my two cents.

Joe J.

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Posted by James Jones.

Engineer on team #267, The Demolition Squad, from North Broward & St Andrews and Motorola.

Posted on 7/5/2000 11:19 AM MST


In Reply to: 60 amp fuse problems... posted by Joe Johnson on 6/30/2000 7:33 PM MST:



Joe, your killing me. If you have a way of increasing the capacity of that fuse and you plan on sharing it with us later why not share it now? Anecdotaly (sp?) I think the fuses degrade with severe use over time so we started replacing them every round and that seemed to help although the people manning the spare parts booth gave us dirty looks.

Just a few comments on this discussion as well.

We used 2 drills and 2 FP's for the drive system this year and had fuse problems. Since the problems don't generally show up until your robot is fully loaded with all its parts and the students are driving aggresively many teams are not going to find out they have a fuse problem until right before the robot ships or at competition. If the only way to fix the problem is a gear ratio change, many teams are going to be stuck because they won't have the time or resources to do this.

Even if you allow 2 fuses, 4 drills can suck the system voltage down so low that the controller starts acting up, so now you need 2 batteries and a higher weight limit.

My opinion is that the robots are fast enough. We were 10 ft/sec at 127 lbs and if we hit another robot hard pieces tended to fly (you should'a had bumpers). Some people thought that we were just out to destroy people but that was not the design intent of the robot, it was the speed. If the robots get even faster I think there is going to be serious carnage on the field. The other thing that makes me nervous about faster robots is debug and practice sessions as well as demos where people may be near a running robot. If our robot hit somebody hard it could very easily break an ankle. I think the robots are fast enough.

That said, we're planning on being faster next year :~)

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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 7/5/2000 3:02 PM MST


In Reply to: Re: 60 amp fuse problems... posted by James Jones on 7/5/2000 11:19 AM MST:



Okay, here's the deal.

As it turns out, three 30 Amp circuit breakers in parrallel will trip before the one 60 Amp fuse. This fact was experimentally determined using a big power supply and an even bigger potentiometer ;-).

So, knowing this fact, you can build from legal kit materials a device that can be put in series with the 60 Amp fuse that has the purpose of protecting the 60 Amp fuse.

The effect of this device is to trade a death sentence for a 2 second reboot of the Robot Interface. Not a bad deal.

The reason that I need to write a 'white paper' on the topic is that it is a bit tricky to actually wire the 3 circuit breakers in parallel.

Actually, we made a few of the devices at the Nationals that plugged between the battery and the robot that we used as 'loaners' for teams having 60 Amp fuse problems. They worked like a charm.

Joe J.

P.S. It has not been my experience that fuses get 'old' after hard useage. I have seen a few 'semi-melted' fuses, but even they seemed to be functioning just fine, it was only inspection that made them know to us, not performance.

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Posted by Jerry Eckert.

Engineer from Looking for a team in Raleigh, NC sponsored by .

Posted on 7/6/2000 11:11 PM MST


In Reply to: 3X30 posted by Joe Johnson on 7/5/2000 3:02 PM MST:



: Okay, here's the deal.

: As it turns out, three 30 Amp circuit breakers in parrallel will trip before the one 60 Amp fuse. This fact was experimentally determined using a big power supply and an even bigger potentiometer ;-).

: So, knowing this fact, you can build from legal kit materials a device that can be put in series with the 60 Amp fuse that has the purpose of protecting the 60 Amp fuse.


The device is constructed from legal kit materials, but is using them in this manner legal?

Rule C5 states that 'Electrical devices may only be wired as described in Section 2
and/or the Robot Rules.

The wiring diagram in section 2 does not show two or more 30 amp breakers wired
in parallel connected to a single device.

Rule C15 states 'ONE [emphasis mine] 30A circuit breaker (provided in the Kit)
must be installed in series with each speed controller on the +12 Vdc input.

Jerry

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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 7/7/2000 7:21 PM MST


In Reply to: Re: 3X30 posted by Jerry Eckert on 7/6/2000 11:11 PM MST:



As the the rules you site, you make good points. Perhaps I have been involved too long in FIRST. The rules from year to year are blurring in my mind. I honestly remembered the rule to be something along the lines of 'only things on the electrical components list may be used to conduct electricity.' Reading the rules more closely, I concede that it seems to be a stretch of the rules.

All I can say is FIRST folks have known about it for years and have never said it was illegal. One of the teams that used the technique told me they were given the green light as well. Beyond this, FIRST folks were involved in looking for teams that might be interested in the 'loaners' we had available at the Nationals.

Anyway, I don't think the spirit of the rules were broken by allowing teams conduct LESS current than the 60 Amp fuse would provide (though for a shorter period of time).

Going forward, I hope that FIRST makes this option explicitly legal. It is a needless worry for a number of teams.

Joe J.

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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 7/10/2000 11:43 AM MST


In Reply to: Con-Fused.... posted by Joe Johnson on 7/7/2000 7:21 PM MST:



I didn't realize that people were doing this. Rule C1 in update #2 is pretty explicit: '... circuit breakers, and fuse may not be tampered with, modified or adjusted in any way...' Figure 2.1 in the rulebook is pretty explicit too.

If there are any performance gains to be made - say, by allowing more motors at a given gear ratio - then I would question whether this is even within the spirit of the rules (its not within the letter in any case). It seems to me that the reason you would want to do this is to allow more stuff (features or performance) to go on in your robot at any given time.

Does this have an effect on how much current you can draw in a transient condition (say, the initial start of the match)?

Ken

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Posted by Mike Dubreuil.

Student on team #175, Buzz, from Enrico Fermi High School and UTC/Hamilton Sundstrand.

Posted on 7/10/2000 3:03 PM MST


In Reply to: Re: Con-Fused.... posted by Ken Patton on 7/10/2000 11:43 AM MST:



Well you have to look at the reasoning behind a rule like this: safety and so you don't fry anything. The only real gain we experienced was that if our 60 amp fuse blew we wouldn't be dead in the water. The circut would not allow any more than 60 amps. So, we did not receive a performance gain. In fact, if my memory serves me correctly we did not use the circut as 'the 60 amp fuse'. The 60 amper was still wired in but the circut would protect it.


: I didn't realize that people were doing this. Rule C1 in update #2 is pretty explicit: '... circuit breakers, and fuse may not be tampered with, modified or adjusted in any way...' Figure 2.1 in the rulebook is pretty explicit too.

: If there are any performance gains to be made - say, by allowing more motors at a given gear ratio - then I would question whether this is even within the spirit of the rules (its not within the letter in any case). It seems to me that the reason you would want to do this is to allow more stuff (features or performance) to go on in your robot at any given time.

: Does this have an effect on how much current you can draw in a transient condition (say, the initial start of the match)?

: Ken

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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 7/11/2000 3:41 PM MST


In Reply to: Re: Con-Fused.... posted by Mike Dubreuil on 7/10/2000 3:03 PM MST:




Does it really make the system safer? Specifically how?

It doesn't change the likelihood that you will fry something, other than the 60A fuse itself (and thats what its there for).

As you say, you experienced a gain because you would not be dead in the water due to a 60 amp fuse blowing. Why would your 60 amp fuse tend to blow? My guess is because you were on the ragged edge in terms of motors being driven at one time, or gear ratios chosen for robot speed, or both. What would you say to teams that didn't use Joe's mod, but instead backed off on gear ratio a little and settled for less speed than you guys did? Do you think it was an equal playing field?

The fact that people are doing this doesn't bother me as much as it surpises me. Its technically cheating isn't it?

Ken


: Well you have to look at the reasoning behind a rule like this: safety and so you don't fry anything. The only real gain we experienced was that if our 60 amp fuse blew we wouldn't be dead in the water. The circut would not allow any more than 60 amps. So, we did not receive a performance gain. In fact, if my memory serves me correctly we did not use the circut as 'the 60 amp fuse'. The 60 amper was still wired in but the circut would protect it.

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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 7/11/2000 10:11 PM MST


In Reply to: Re: Con-Fused.... posted by Ken Patton on 7/11/2000 3:41 PM MST:



Ken,

Actually, I was sick when I saw the references that were sited that called into question the legality of the device I have proposed. My first reaction was to pull up the rules that would allow me to show how I had come to the conclusion that it was okay. Looking it up, I was really surprised to see that the rules were not as I had thought. If you doubt that I really believed this was okay, look at my first posting. It is clear from my wording that I THOUGHT the rule involved building things that carried electricity from legal kit materials. As to how I came to the conclusion that it was legal in the first place, I am afraid that it is lost at this late date. Another argument agianst my belief that the device was illegal is the fact that we openly shared the device with a number of teams and then posted a reference to it on this website.

Even so...

You call it cheating. I disagree for a number of reasons:

Many inspectors saw the device, inquired about it and said nothing negative and, more likely, compemented us on its cleverness.

A nunber of tech folks at FIRST knew about it and did not tell us it was illegal, on the contrary, they agreed to help us find teams that might be having 60 Amp fuse problems and could use one of our loaners.

A number of other FIRST teams tell us that they made a point of asking FIRST specifically if it was allowed and being told it was okay.

So...

I argue against the cheating label. Yet, at the same time, I promise to re-double my efforts to follow the advice I often give to rookie teams, specifically, to carefully read and fully understand the entire rule book.

As to the future, I hope that FIRST either make the device officially legal or find some other way to keep from having teams blowing the 60 amp fuse.

Joe J.

P.S. By the way, in the case of the Chief Dephi Team the advantage gained from this device has been more mythical than real. To my knowledge, this device has never been tripped by a Chief Delphi Robot, not even in practice, yet alone in a match. We installed the device in on CD4 in a fit of paranoia after a single blown fuse in a single match (that was as likely as not due to a programming bug coded by yours truly ;-) Paranoia dies hard. We never removed the device eventhough it has never been tripped either on CD4 or CD5.

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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 7/12/2000 2:53 PM MST


In Reply to: Cheating... posted by Joe Johnson on 7/11/2000 10:11 PM MST:



Joe-

I was not suggesting that you guys, or anyone else, intended to break the rules and gain an advantage by doing this. I totally believe that whoever was doing this was just trying to keep their machine from being stranded due to a blown 60A fuse. However, I think it's fair game for me to suggest that it might be possible to use this to create an advantage in terms of number of features that can run at one time, or the ratio that could be run for a given set of motors.

I want to raise my concerns because I think we competitors are all dependent on each other actively choosing to follow the rules. So hopefully I'm doing my part to exert some peer pressure.

Here's what is really bothering me: I think FIRST needs be more careful. I know they are dependent on the experienced teams for some new developments, because its usually the experienced teams that help solve the new problems (as you guys did here). And thats important - it makes for a better game if the robots run well. But these new developments - IF they depend on changes or clarifications in the rules - should be rolled out by FIRST to all teams in an update. That way (in my opinion) we won't have any concerns about anyone having an advantage.

So, sorry to stir things up - I don't think you guys cheat, you beat (nearly) everyone fair and square :)).

Ken

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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 7/13/2000 8:17 AM MST


In Reply to: Re: Cheating... posted by Ken Patton on 7/12/2000 2:53 PM MST:



I agree with you concerning rules clarifications/interpretations/updates/etc.

FIRST should make sure that all teams have access to the same information.

Perhaps they should have a web based forum to ask about rules & answer questions ;-)

Joe J.

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Posted by Dodd Stacy.

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

Posted on 7/13/2000 3:04 PM MST


In Reply to: seconded! posted by Joe Johnson on 7/13/2000 8:17 AM MST:



Joe, Jerry, Ken, et al,

I'm just a gearhead, but I've been confused since this '3x30

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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 7/13/2000 5:26 PM MST


In Reply to: Dumb Question posted by Dodd Stacy on 7/13/2000 3:04 PM MST:



Dodd,

The thing about fuses is that the amp rating does not tell all. Time is a very important factor.

A fuse that is rated for a particular amperage will be able to carry that amount of current forever at the rated temp (e.g. 20 deg C). They can carry twice that current for a shorter period of time, 3 times the current for an even short time, etc. As I recall, the 60 amp fuse can carry 120 amps for something on the order of 100 seconds.

Circuit breakers have a similar method of rating EXCEPT they typically have a much lower margin of safety (if you want to call it that -- it could be thought of as a higher margin of safety if you thing about 'safe' as being 'sure not to start a fire' rather that as 'sure not to trip' but I digress...) For example a 30 amp breaker while never tripping at room temp at 30 amps may trip in 30 seconds at 40 amps and 10 seconds at 60 amps.

Using the example numbers above, 3 thirty amp curcuit breakesr carrying 120 amps would trip in 30 seconds (each breaker carrying 40 amps). A fuse would require 100 seconds to trip. SO... 3 thirty amp circuit breakers would protect 1 sixty amp fuse. Yes, 2 thirty amp breakers would protect the fuse as well but it would be TOO well in a sense limiting current to much less than would normally go through the fuse without trouble -- note that 120 amps would trip them in just 10 seconds . Also note that 4 thirty amp breakers would do no good what ever as they could carry 30 amps each (120 amps) forever without tripping while the fuse would blow in 100 seconds. The numbers are approx. but the idea is the same.

As to mfg. variation, this is not a problem. Yes, one of the breakers blows first but as soon as it does, the other two blow almost instantly after because they are carrying 50% more current all of a sudden!

I hope this clears things up a bit.

Joe J.

[archiver]

Posted by Dodd Stacy.

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

Posted on 7/13/2000 8:40 PM MST


In Reply to: Timing is everything... posted by Joe Johnson on 7/13/2000 5:26 PM MST:



Thanks, Joe. Very clear. I hadn't realized that these devices (fuses) were so sluggish in their time response. I would not have thought they had sufficient thermal mass to absorb the I^2R loss above their rated current for so long before melting/vaporizing at the high resistance pinch point.

It's also interesting in the context of a 120 second match. If a 60 amp fuse will carry 120 amps for 100 seconds, perhaps it will carry 100-110 amps for 120 seconds? That would say we can run at a steady average system power of about 1 kw throughout a match, if the battery can maintain a 10 volt or so potential under a 100 amp draw. That's a lot of power.

Seems to me like it would be hard to blow the fuse unless you are stalling one or more motors for a significant period of time. But since each motor is protected by its own 30 amp breaker, and since the stall current on the 'big' motors is so high (I dimly recall), I would think the standard FIRST wiring schematic would provide adequate protection. At least if the drivers refrained from stalling multiple motors simultaneously for 10 seconds or more.

I only know that we've used all the more powerful motors (2 drills, 2 F-P's, and 2 van doors) and never popped a breaker or blown a fuse. Maybe we're not trying hard enough (but the GraceHopper wasn't exactly undergeared as it was).

Dodd

[archiver]

Posted by Michael Betts.

Engineer on team #177, Bobcat Robotics, from South Windsor High School and International Fuel Cells.

Posted on 7/14/2000 10:49 AM MST


In Reply to: Enlightenment, It's Electrifying posted by Dodd Stacy on 7/13/2000 8:40 PM MST:



First, let me say that I am more than a little concerned at the revelation that this 3X30 was allowed by FIRST and implemented by several teams without any mention of it in the Q&A section of the updates. I will bring this up at the Team Forum in August.

Secondly, I agree completely with Dodd:

'I only know that we've used all the more powerful motors (2 drills, 2 F-P's, and 2 van doors) and never popped a breaker or blown a fuse. Maybe we're not trying hard enough...'

The Bobcat has not blown a 60A fuse in the last few years (except once, when an attempt was made to connect the battery backwards). In fact, we used every motor (11) in the kit two years ago (to get onto the puck, et cetera) and never blew a fuse.

Many teams have demonstrated that competitive robots and 60 amp fuses are not mutually exclusive.

The Bobcat design team has always opted to err on the side of reliability within the restraints of the contest rules. In the last four years, we have never failed to make the cut for the finals in any contest we entered (in or off season).

It all comes down to trade offs.

One of the great challenges in engineering is the trade-off. Design requires a balance of functionality, reliability, efficiency, speed and power. Execution requires a balance of design, quality of manufacturing and strategy.

If you want high reliability, you will sacrifice some speed and/or power. It's that simple.

It is normal for someone to become frustrated if they are blowing fuses and, in a contest this size, someone always will (regardless of the size of the protection devices). After the frustration passes, it's time to review the design (Dr. J's superb white paper on motors was required reading this year), take some measurements and take corrective action (find the source of friction, reduce gear ratios, et cetera).

In the end, reality does not care about your design calculations and a real-world engineer has to learn to deal with it.

'We're gonna vent our frustrations,
And if we don't we're gonna blow a 50 [60] amp fuse
You can't always get what you want...'

With apologies to Messrs. Jagger and Richards.

- Mike

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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 7/17/2000 10:34 AM MST


In Reply to: Timing is everything... posted by Joe Johnson on 7/13/2000 5:26 PM MST:



From the manual, here are the specs for the circuit breaker (theres a plot on the data sheet also):

they will hold 100% of rating forever
they will be sure to trip when held at 135% of rating
they will trip in 2.5-6.5 seconds when held at 200% of rating

So for these short periods of time (which are long enough to 'launch' your robot from rest) you can overload the circuit breakers.

Ken

[archiver]

Posted by Nate Smith.

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

Posted on 7/16/2000 3:14 PM MST


In Reply to: seconded! posted by Joe Johnson on 7/13/2000 8:17 AM MST:



: I agree with you concerning rules clarifications/interpretations/updates/etc.

But the issue here seems to be only one of a creative use of components that, based on my readings, is not explicitly forbidden. I mentioned this somewhat in the other post that I just finished on this, but the only rules that I find on the use of the breakers is that they must be used in certain instances, and that they may not be modified. Without knowing the technical info behind the 3x30 device, it appears to fall into the rules that I have found...

Nate

[archiver]

Posted by Mike Dubreuil.

Student on team #175, Buzz, from Enrico Fermi High School and UTC/Hamilton Sundstrand.

Posted on 7/14/2000 4:24 AM MST


In Reply to: Re: Con-Fused.... posted by Ken Patton on 7/11/2000 3:41 PM MST:



It makes it safer because you can't pull as much power out of the battery as possible. I think that could add a hazard into the game: melting electrical wires (although I'm not sure with the generous safety margin FIRST has in effect on gauge), leaking batteries, fire, stuff like that.
When I made reference to the frying of components I was talking about fuses in general, spefically those that protect Spikes or Victors. They could easilly fry under too high of a load (without fuses).

:
: Does it really make the system safer? Specifically how?

: It doesn't change the likelihood that you will fry something, other than the 60A fuse itself (and thats what its there for).

: As you say, you experienced a gain because you would not be dead in the water due to a 60 amp fuse blowing. Why would your 60 amp fuse tend to blow? My guess is because you were on the ragged edge in terms of motors being driven at one time, or gear ratios chosen for robot speed, or both. What would you say to teams that didn't use Joe's mod, but instead backed off on gear ratio a little and settled for less speed than you guys did? Do you think it was an equal playing field?

: The fact that people are doing this doesn't bother me as much as it surpises me. Its technically cheating isn't it?

: Ken

:
: : Well you have to look at the reasoning behind a rule like this: safety and so you don't fry anything. The only real gain we experienced was that if our 60 amp fuse blew we wouldn't be dead in the water. The circut would not allow any more than 60 amps. So, we did not receive a performance gain. In fact, if my memory serves me correctly we did not use the circut as 'the 60 amp fuse'. The 60 amper was still wired in but the circut would protect it.

[archiver]

Posted by Matt Leese.

Student on team #7 from Parkville High School and NASA, Black & Decker, AAI, Raytheon.

Posted on 7/10/2000 7:12 PM MST


In Reply to: Re: Con-Fused.... posted by Ken Patton on 7/10/2000 11:43 AM MST:



: I didn't realize that people were doing this. Rule C1 in update #2 is pretty explicit: '... circuit breakers, and fuse may not be tampered with, modified or adjusted in any way...' Figure 2.1 in the rulebook is pretty explicit too.

I think that rule refers to tampering or modifing the ACTUAL circuit breaker or fuse (i.e. taking the 60 amp fuse apart) but doesn't refer to how they are wired. I don't think FIRST could really have much of a problem with this as we are already wiring a 30 amp breakers inline between most things and the 60 amp fuse (at least my team did -- it was easiest to use the transmission blocks that FIRST provided...). The only thing that has changed is that they we'd then be running three 30 amp circuit breakers in parallel as a master breaker over all the others. I don't remember any particular rule banning anything like that (I don't have a rule book handy and don't feel like downloading it). If you can come up with anything else that wouldn't permit it, I'd be interested in knowing.

Matt Leese

[archiver]

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 7/11/2000 3:27 PM MST


In Reply to: Re: Con-Fused.... posted by Matt Leese on 7/10/2000 7:12 PM MST:




As I said in my post, Figure 2.1 is pretty explicit. It, along with the wording in the rules and updates, doesn't leave any room for changes.

Ken

[archiver]

Posted by Nate Smith.

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

Posted on 7/16/2000 3:09 PM MST


In Reply to: Figure 2.1 is clear posted by Ken Patton on 7/11/2000 3:27 PM MST:



: As I said in my post, Figure 2.1 is pretty explicit. It, along with the wording in the rules and updates, doesn't leave any room for changes.

My understanding of Figure 2.1 in the rules is that is was an example of how things could be wired. After all, it was not required that a separate panel be used for distributing ground, nor were the panels required at all(the breakers could be wired directly inline[with spade connectors for example].) So, the fact that a 3x30 breaker setup inline between the power distribution panels and 60A fuse is not shown in the diagram would not appear to be grounds for it not being able to be used.

Also, when looking over the rules, the only ones I can find regarding the use of the breakers is that they must be used with certain motors. There appears to be nothing saying that they may not be used in other cases, such as the 3x30 combination...

Just my 2 cents..

Nate

[archiver]

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 7/17/2000 10:26 AM MST


In Reply to: Re: Figure 2.1 -absolute or example? posted by Nate Smith on 7/16/2000 3:09 PM MST:



Nate-

I don't see anywhere where it says Figure 2.1 is an 'example' as you suggest. Figure 2.1 says that the grounds are on a different fuse panel. In section 2.1 the manual says 'Teams will be required to correct wiring that is not configured according to this section...' In rule C1 it lists a number of exceptions to control system wiring, and it doesn't mention creative usage of the circuit breakers.

If I was a judge (and I'm not), I'd say rewire it, unless FIRST clarified the rules.

Ken

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Posted by Mike Dubreuil.

Student on team #175, Buzz, from Enrico Fermi High School and UTC/Hamilton Sundstrand.

Posted on 7/9/2000 9:16 AM MST


In Reply to: 3X30 posted by Joe Johnson on 7/5/2000 3:02 PM MST:



If any of you have been following Buzz you would know that in the begining we would blow the 60 amp fuse constantly (almost every match). This of course results in a catastrophic failure and leaves your alliance to fend for themselves (totally unacceptable). If my memory serves me correctly altogether Buzz has 11 motors on it. We checked and rechecked each motor and could not find anything wrong with our system.
Luckilly, Dr. Joe showed us his neat trick. We used resetable fuses in ours so it had to be approved by FIRST, luckily it did. From that point on, Buzz became a reliable robot. Sure, probably about twice each match Buzz would faulter but the next second everything was back online.

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Posted by Adam Krajewski.

Student on team #68, Truck Town Terror, from Walled Lake Central High School and General Motors Truck Group.

Posted on 7/14/2000 12:19 PM MST


In Reply to: 3X30 posted by Joe Johnson on 7/5/2000 3:02 PM MST:



Dr. Joe, which gauge wire did you use to wire the 3 30 Amp fuses together? 6 GA or 10 GA?

Adam

[archiver]

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 7/14/2000 2:39 PM MST


In Reply to: Wire GA posted by Adam Krajewski on 7/14/2000 12:19 PM MST:



6 Gauge wire -- it is carrying a lot of current.

Joe J.

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Posted by Dodd Stacy.

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

Posted on 7/14/2000 4:55 PM MST


In Reply to: 6 GA posted by Joe Johnson on 7/14/2000 2:39 PM MST:



Another dumb gearhead question. Is it really better, safer (lower resistance) to make crimp fitting connections on very heavy gauge wire - like 6 Gauge - than to make proper solder (or silver soldered) joints? I'm appalled to see the 6 Gauge battery wire connections (after they loosen up from many cycles of make and break) and think that they are carrying maybe 100 amps. In fact, a lot of the FIRST rule motor connections worry me in this regard. Give me a nice hefty chain and sprocket set, thank you very much.

Dodd

: 6 Gauge wire -- it is carrying a lot of current.

: Joe J.

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Posted by Michael Betts.

Engineer on team #177, Bobcat Robotics, from South Windsor High School and International Fuel Cells.

Posted on 7/15/2000 11:39 AM MST


In Reply to: Connections posted by Dodd Stacy on 7/14/2000 4:55 PM MST:



: Another dumb gearhead question. Is it really better, safer (lower resistance) to make crimp fitting connections on very heavy gauge wire - like 6 Gauge - than to make proper solder (or silver soldered) joints?

A 'proper' crimp is better than solder. PbSn solder cannot hold up to the physical stress and strain to which a large gauge wire is normally subjected to and silver solder has it's own set of problems, such as acid flux, making it unsuitable. In a 'proper' crimp connection, the wires actually cold flow within the crimp. Production, high reliability crimps are actually made with an pneumatic or hydraulic tool or press. Such a tool can exert pressures of over 15 tons on the crimp. At the high school, a manual crimp tool is often used.

The problem is that each connector has it's own crimp tool, unique to the manufacturer and model, which are expensive and long lead items.

To crimp 6 AWG wire, we use an old, manual, T&B crimp tool (2 to 8 AWG) which was 'donated' by IFC to the school. This old crimp tool we use has 20' handles and we add sheet metal shims (outside of the crimp lug) until it is 'almost' impossible for one person to crimp. In fact, when crimps are being made by some of my younger and/or female team members (I'm not being sexist here... it is a matter of upper body strength), I will slide a couple of 30' sched 40 pipes over the handles to improve the mechanical advantage.

Look up Team 177 at one of our future events and I'll have the kids demonstrate how we do it. We plan to be at Rumble, Riverrage, Bash and the Expo in the next few months.

A proper crimp is one of the strongest 'links' in your electrical chain and will NOT fail or loosen. You will rip the electrical terminal off of the lead acid battery long before the crimp fails (voice of experience here...).

Talk to an electrician in your facilities dept (school or company) and they can probably let you borrow (or have) an old tool.

Having said all that, the only crimp connection which I have the students routinely replace with solder is at the connections on the FP motors. These are meant for toys and, obviously, do not enjoy the quality inspections or standards that the automotive components in our kit do.

Remember to strain relief whenever a solder connection is used!


Good luck.

Mike

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Posted by Justin Stiltner.

Student on team #388, Epsilon, from Grundy High School and NASA, American Electric Power, Town of Grundy.

Posted on 7/15/2000 11:09 PM MST


In Reply to: Re: Connections posted by Michael Betts on 7/15/2000 11:39 AM MST:



I totally agree with what you said... our 'machinist' rebuilds mining equipment for a living so he has some pretty beefy tools 'the wire on a normal peice of equipment carries about 480 volts at about 300 amps so he knows about working with big wire, the crimpers we used on the 6ga. wire had 3 foot handels and was a slide type 'it looked more like a vice than a pair of pliers' and would make the finished crimp into the shape of a U when completed. We also put heat shrink tubeing on all of the crimp joints. You can never be too safe. At one time I considered running some of the wire in conduit... hehe lol

Also could Some one Possabley post a pic of the housing they used for the 3 breakers and they'r associated wireing? Or give a few hints as to how they housed it?

Justin Stiltner
Team #388
Epsilon
Grundy Va,

[archiver]

Posted by Dodd Stacy.

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

Posted on 7/18/2000 7:28 AM MST


In Reply to: Re: Connections posted by Michael Betts on 7/15/2000 11:39 AM MST:



Thanks, Mike and Justin. I guess there's no substitute for the proper tool, or at least one capable of adequately high crimp pressures (and constraining the fitting so it doesn't just flatten). We will need to pay closer attention to tools and technique in the future. I will definitely stop by team 177's pits at River Rage for a looksee and a lesson. Thanks, again.

Dodd

: A 'proper' crimp is better than solder. PbSn solder cannot hold up to the physical stress and strain to which a large gauge wire is normally subjected to and silver solder has it's own set of problems, such as acid flux, making it unsuitable. In a 'proper' crimp connection, the wires actually cold flow within the crimp. Production, high reliability crimps are actually made with an pneumatic or hydraulic tool or press. Such a tool can exert pressures of over 15 tons on the crimp. At the high school, a manual crimp tool is often used.

: The problem is that each connector has it's own crimp tool, unique to the manufacturer and model, which are expensive and long lead items.

: To crimp 6 AWG wire, we use an old, manual, T&B crimp tool (2 to 8 AWG) which was 'donated' by IFC to the school. This old crimp tool we use has 20' handles and we add sheet metal shims (outside of the crimp lug) until it is 'almost' impossible for one person to crimp. In fact, when crimps are being made by some of my younger and/or female team members (I'm not being sexist here... it is a matter of upper body strength), I will slide a couple of 30' sched 40 pipes over the handles to improve the mechanical advantage.

: Look up Team 177 at one of our future events and I'll have the kids demonstrate how we do it. We plan to be at Rumble, Riverrage, Bash and the Expo in the next few months.

: A proper crimp is one of the strongest 'links' in your electrical chain and will NOT fail or loosen. You will rip the electrical terminal off of the lead acid battery long before the crimp fails (voice of experience here...).

: Talk to an electrician in your facilities dept (school or company) and they can probably let you borrow (or have) an old tool.

: Having said all that, the only crimp connection which I have the students routinely replace with solder is at the connections on the FP motors. These are meant for toys and, obviously, do not enjoy the quality inspections or standards that the automotive components in our kit do.

: Remember to strain relief whenever a solder connection is used!

:
: Good luck.

: Mike

[archiver]

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 7/19/2000 1:24 PM MST


In Reply to: Re: 60 amp fuse problems... posted by James Jones on 7/5/2000 11:19 AM MST:



: Anecdotaly (sp?) I think the fuses degrade with severe use over time


Hello All;

That is a correct belief. Fuses have a definite 'lifespan'. Even when operated below their rated limit, the link heats up slightly, and over time begins to crystalize. Eventually, it fails, sometimes well below the rated value. If you have a fuse blow in your home electrical panel, and it isn't from an overload, buy a box of spares because the rest will likely be going in the not to distant future (actually, consider replacing the panel with circuit breakers, but I digress).

If you operate a fuse above it's rated current (in this case 60 amps), this process will accelerate substantially. We reached the point at the NJ regional where the fuse would only last 2 rounds, even though we were still 'on the curve'. We replaced the fuse every round, and regeared for the Nationals.


Perhaps with a little luck, next year we will get a circuit breaker instead of the 60 amp fuse. Much easier to turn the machine on and off, and not subject to the deterioration problems that fuses are (at least, not in the timeframe we work in...).

Tom Frank

[archiver]

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 7/19/2000 2:14 PM MST


In Reply to: Re: 60 amp fuse problems... posted by Thomas A. Frank on 7/19/2000 1:24 PM MST:



Tom,

It is my experience that if you find an exact make and model for a part you want in the kit the chances of getting the item in the kit is greatly increased.

If you then go the next step and buy one and ship it to Eric or Frank at FIRST, the odds increase even more.

The only thing beyond that is to contact the supplier and get them to donate the parts. In this case you have the best chances you can get.

SO...

...if you want a circuit breaker in 2001, you know what to do.

Joe J.

[archiver]

Posted by Mike Carron.

Engineer on team #343, Oconee's 2000 Crew, from Hamilton Career Center and Nasa/Square D Company.

Posted on 7/29/2000 11:36 AM MST


In Reply to: Do you have a breaker in mind? posted by Joe Johnson on 7/19/2000 2:14 PM MST:



: To whom it might concern,
I am an Engineer on team #343 who works for Square D company. We are currently trying to donate a breaker to replace the 60A fuse. This will allow for a 'disconnecting' means (not pulling the fuse out) and also provide more consistant protection for the motor loads. The only issue with breakers however, is that they tend to trip with electrical pressure (amperage or short circuit pressure). This means that an impact onto a breaker mechanincally can cause it to trip. The breaker is basically the same size as the fuse used this year and allows for wires to be terminated via a screw type lug (rated for #6 wire, actually #4). Several teams are testing this breaker as we speak as well as my team#343. Hopefully we'll have some good news for next year.
Later,
Mike Carron
SR. Applications Engineer
Square D Company
Seneca,SC.

[archiver]

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 7/29/2000 1:00 PM MST


In Reply to: Re: Do you have a breaker in mind? posted by Mike Carron on 7/29/2000 11:36 AM MST:



Mike,

This sounds LOVELY.

Can you give out model numbers? I would like to at least get a peek at the specs for trip time vs current.
If I really get whacky I may buy one and install it on our 2000 robot in time for one of the upcoming afterglow tourneys in Sept. just to see how they work out in live competition situations.

Anyway... ...Thanks a heap for advancing the technology for all FIRST teams.

Now if only someone from Parallax Inc. hosted a FIRST team. I have some suggestions for the STAMP 2 language that would help out a lot....

Joe J.

[archiver]

Posted by Mike Carron.

Engineer on team #343, Oconee's 2000 Crew, from Hamilton Career Center and Nasa/Square D Company.

Posted on 7/29/2000 8:55 PM MST


In Reply to: Can I kiss you??? posted by Joe Johnson on 7/29/2000 1:00 PM MST:



Joe,
As I sit here at home right now, I can't seem to remember the exact part number. I can send you some information on Monday when I get back to the office. We actually submitted several breakers but FIRST has settled on one them. The characteristic curve of the breaker seemed to tickle their fancy. Is their an email address that I can send this to? Why don't you jog my memory Monday by dropping me an email at carronm@squared.com.
Later and happy botting,
Mike C.

[archiver]

Posted by David Kelso.   [PICTURE: SAME | NEW | HELP]


Coach on team #131, C.H.A.O.S.-, from Central High School and OSRAM SYLVANIA/ Fleet Bank.

Posted on 6/30/2000 8:16 PM MST


In Reply to: Re: What else do we want? posted by Justin Ridley on 6/30/2000 10:08 AM MST:




Remember that buying a couple more drill motors also requires buying a couple more speed controllers at $120?? each..

[archiver]

Posted by James Jones.

Engineer on team #267, The Demolition Squad, from North Broward & St Andrews and Motorola.

Posted on 7/5/2000 11:28 AM MST


In Reply to: What else do we want? posted by Andy Baker on 6/22/2000 7:12 AM MST:



Lighten up on the Bumper Rules!

Let us put them where we want, however big we want (within reason) and give us a little extra weight for them (5 - 10 lbs). Many people didn't use them (including us) because they we didn't have the weight or couldn't legaly put them in areas where they could have helped mitigate damage to other robots during a tussle because they would have been at the wrong elevation.