Shifting Gears

[DanL]

Originally Posted by Matt Adams

The most common way to cool your breakers is to take some of that keyboard cleaning compressed air. For long days of demonstrations, we've used compressed air to cool our motors down. However, this is honestly a pretty terrible engineering practice, and is NOT recommended.

They actually make something called "freeze spray" - it comes in the same size and shaped bottle as the keyboard cleaning stuff, though. Yeah, you get the same effect, but since freeze spray is designed for cooling rather than blowing, you could probably get more for your money or cooler temps. It's also antistatic.

Can't give you any product brand or where my team got it... look around - I'm sure you'll find it.

[sanddrag]

Originally Posted by SuperDanman

They actually make something called "freeze spray" - it comes in the same size and shaped bottle as the keyboard cleaning stuff, though. Yeah, you get the same effect, but since freeze spray is designed for cooling rather than blowing, you could probably get more for your money or cooler temps. It's also antistatic.

Can't give you any product brand or where my team got it... look around - I'm sure you'll find it.

The only difference between "canned air" and "freeze spray" is that on the inside of the can one is up-side-down.

[Ken Patton]

Originally Posted by Cory

If Im not mistaken, while it draws more current, you are drawing less current per motor since the load is being shared between four motors rather than two. Since weve all basically agreed that the main breaker isnt going to trip, this would help keep individual motors from tripping their respective 40 amp breakers.

Cory

You are right Cory, 2002 was the last time a lot of teams had problems with this. Although, I'm not sure that its simply a matter of us agreeing that it doesn't happen anymore. I remember an extremely fast machine (25) that appeared to have breaker problems in the finals at Houston last year. I don't know for sure if this was a main breaker problem or not.

Ken

[Rob Colatutto]

Originally Posted by Ken Patton

You are right Cory, 2002 was the last time a lot of teams had problems with this. Although, I'm not sure that its simply a matter of us agreeing that it doesn't happen anymore. I remember an extremely fast machine (25) that appeared to have breaker problems in the finals at Houston last year. I don't know for sure if this was a main breaker problem or not.
Ken

That was them tripping thier main breaker. What team 25 had in 02 and in 03 was a servo actuated break that pushed into a whole drilled into one of thier drive gears that they used as a break since they were geared high both years so not much pushing power. The pin didn't come out all the way and thus when trying to moved they pulled a nice 220A or so and popped the breaker.

Matt, what method of shifting does that transmission that 461 is working on use? The only thing I could think of that does not require more than a lathe or mill would be a mesh shifter.

[Matt Adams]

Originally Posted by Joe Johnson

I agree with 80-90% of what Matt has to say, but the above quoted comment is one that I feel I need to say something about.
<SNIP>
This is not to say that there are not multiple reasons NOT to use N motors per side -- there are many, but tripping the 120 Amp breaker is not one of them (imho).
<SNIP>

Sit right back folks, it's story time from Matt Adams.

Sit, honest. This might get long.

I'm rehashing one of my very first posts (my very first?) and this reply made by Dr. Joe.

First off, I'd like to say that I absolutely respect Dr. Joe and many of the brilliant things that he's shared with the first community through Chief Delphi and other venues. He's a brilliant guy. So brilliant, in fact, that when he said the above statement back sevearl months ago, I really appreciated the engineering experience ahead of the the theoretical calculations I do in school. I used that advice while doing calculations for our machine, and we didn't have a single problem with our 120 Amp breaker over the course of the entire season, minus a single match. That single match is why I'm posting now.

Let me immediately remark that I am in no way trying to put any blame on Dr. Joe for the success or lacktherof of 461 this season. Ultimately any sort of machine failures are the responsibility of the design engineers and the people who give designs the stamp of approval (or signature in our case). That person was me.

With that all said...
461 had 4 motors (no transmission) for their drive train this past year, as well as a few supplimental motors to control other functions, namely a fisher price for a small ball roller and a van door for a big ball grabber.

The reason I post now is to share some more real-life experience using this breaker, in hopes that similar mistakes are not made in the future.

Curie Field, 2004. Last match of the division finals. 461 had played at least 8 consecutive matches without swapping out with an alliance member for strategic reasons... both joysticks were pushed forward, and the robot does too... for about 5 seconds after autonomous before tripping the 120 Amp breaker... costing the alliance the match and perhaps winning the division or more.

The 120 Amp breakers are thermal devices... over the course of several matches, they heat up, and become more likely to trip. While several teams know to use compressed air to cool motors during the final rounds, most teams don't think about the main breaker. If you're pulling 160 amps or so through it for several consecutive matches, this is an important fact to remember.

The FIRST finals are truly a test for machines, and all of the design parameters need to be built around this. From personal experience, there's no feeling worse than losing a match because of a human error or an obvious potential failure that wasn't planned for. I hope that everyone who reads this post ensures they think carefully about power management, thermal conditions of their machine, and designing machines around their shining moments in the finals.

Good luck everybody!

Matt

[Matt Adams]

Originally Posted by Joe Johnson

I agree with 80-90% of what Matt has to say, but the above quoted comment is one that I feel I need to say something about.
<SNIP>
This is not to say that there are not multiple reasons NOT to use N motors per side -- there are many, but tripping the 120 Amp breaker is not one of them (imho).
<SNIP>

Sit right back folks, it's story time from Matt Adams.

Sit, honest. This might get long.

I'm rehashing one of my very first posts (my very first?) and this reply made by Dr. Joe.

First off, I'd like to say that I absolutely respect Dr. Joe and many of the brilliant things that he's shared with the first community through Chief Delphi and other venues. He's a brilliant guy. When he said the above statement back several months ago, I really appreciated the engineering experience instead of the theoretical calculations I do in school. I used that advice while doing calculations for our machine, and we didn't have a single problem with our 120 Amp breaker over the course of the entire season, minus a single match. That single match is why I'm posting now.

Let me immediately remark that I am in no way trying to put any blame on Dr. Joe for the success or lacktherof of 461 this season. Ultimately any sort of machine failures are the responsibility of the design engineers and the people who give designs the stamp of approval (or signature in our case). That person was me.

With that all said...
461 had 4 motors (no transmission) for their drive train this past year, as well as a few supplimental motors to control other functions, namely a fisher price for a small ball roller and a van door for a big ball grabber.

The reason I post now is to share some more real-life experience using this breaker, in hopes that similar mistakes are not made in the future.

Curie Field, 2004. Last match of the division finals. 461 had played at least 8 consecutive matches without swapping out with an alliance member for strategic reasons... both joysticks were pushed forward, and the robot does too... for about 5 seconds after autonomous before tripping the 120 Amp breaker... costing the alliance the match and perhaps winning the division or more.

The 120 Amp breakers are thermal devices... over the course of several matches, they heat up, and become more likely to trip. While several teams know to use compressed air to cool motors during the final rounds, most teams don't think about the main breaker. If you're pulling 160 amps or so through it for several consecutive matches, this is an important fact to remember.

The FIRST finals are truly a test for machines, and all of the design parameters need to be built around this. From personal experience, there's no feeling worse than losing a match because of a human error or an obvious potential failure that wasn't planned for. I hope that everyone who reads this post ensures they think carefully about power management, thermal conditions of their machine, and designing machines around their shining moments in the finals.

Good luck everybody!

Matt

[Joe Johnson]

Originally Posted by Matt Adams

...Let me immediately remark that I am in no way trying to put any blame on Dr. Joe for the success or lacktherof of 461 this season...

Let me just start by saying that all my remarks more or less come with a "your mileage may vary" disclaimer. I don't take blame or credit so easily.

Now to the 120Amp breaker issue. I am surprised that even with this condition you tripped the breaker, but I suppose that with all the improbablities piled up on top of eachother, it is possible. Well... ...to say "I suppose" is wrong. I should say, now I realize that given a long enough time of stalling 4 motors plus others you can trip the 120A breaker.

But evenso, I pretty much stand by my thought that it is almost impossible to trip it in a 2 minute match.

If anything, Matt's story is a cautionary tale to spray the 120A breaker with "cool in a can" while you are spraying your motors, especially if you are stalling many of the drive motors for significant portions of the match (search for my messages on "Cool in a Can" if you want to know my feelings about the importance of this product -- especially during elimination rounds where you play many matches in a row).

Joe J.

[sanddrag]

Originally posted by MBosompra
http://jaw.iinet.net.au/crustyquinns/gears.html

I would hate to have to make that. Although I would feel very proud after I did.

[Madison]

Why shift gears when you can shift wheels?

[Rpifirst]

Yeah kickers. 190 did this very sucessfuly in 2001. But i think it takes up amuch more weight than a transmission.

[Madison]

Originally posted by Rpifirst
Yeah kickers. 190 did this very sucessfuly in 2001. But i think it takes up amuch more weight than a transmission.

It is heavier, usually, but can offer more advantages as well. Not only does it allow you to change speed and output torque, but other things like wheel base, tread, width and type.

I've helped do it very successfully in 2002 and, with luck, I'm going to do it even better in 2004.