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  #16   Spotlight this post!  
Unread 06-26-2003, 07:22 AM
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Al Skierkiewicz Al Skierkiewicz is offline
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We have several...
Over the years we have used servos to activate a microswitch on the robot for a program branch jump, to drop an anchor to hold us on a ramp, release a magic tongue and this year we used servos to brake the drive mechanism for our wings (that is what holds them up at the end of the match!) Sometimes you don't need a lot of power, just the will to move.
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Unread 06-26-2003, 10:06 PM
Sully Sully is offline
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At one of the regionals in 2003 I noticed one team (I don't recall the no.) that was using a servos to interface with the Victor 884. The servo was used to activate a switch that was wired to the brake / coaster jumper on the Victor. This enabled the team to actively change the drive system from a dynamic brake system to a coast system. I am not sure what their reasoning was but it was a very clever way to overcome a problem. Simply put the servos can be used to activate switches of all types to suit the needs of the robots.
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Unread 06-26-2003, 11:28 PM
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James114 James114 is offline
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Cool

In 2001 my team used a servo to wave a small American flag back in forth
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Unread 07-14-2003, 11:56 PM
Veselin Kolev's Avatar
Veselin Kolev Veselin Kolev is offline
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My team has never used the servos, but we will next year...

Anyway, you can use it to shift gears as many say, or do useless stuff, but I saw one team that put two servos on their lamp and raised or lowered it every time they had to go under the bar. The only problem was it took too long to move one time, and they broke their lamp. You can buy servos withing a huge range of power, from about 5 oz/in of torque to about 1000 oz/in.
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Unread 07-15-2003, 12:01 AM
sanddrag sanddrag is offline
On to my 17th year in FRC
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Quote:
Originally posted by Veselin Kolev
You can buy servos withing a huge range of power, from about 5 oz/in of torque to about 1000 oz/in.
You can buy wheelchair motors with a huge range of power that doesn't mean you can use them. Servos not provided in the kit are illegal since they have a motor inside. Sorry.
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Unread 07-15-2003, 12:34 AM
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Rookie power

This is really a neat and compact design. We used the plastic drill motor mounts and mounted them to our steel frame. We then added a little L shape piece of aluminum on all four sides to serve two purposes:

1) Mount four small muffin fans to cool our motors down

and

2) Support the servo mounts

The airflow was superb, we didn't overheat once after they were installed, and being able to switch from high to low gear allowed us to have a quick/precise autonomous mode followed by a powerful low gear. It all worked out nicely =)

I would also like to point out that it was one of our wonderful students who designed that little gear-shift mechanism. Hope the picture helps
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Unread 07-15-2003, 12:52 AM
WakeZero WakeZero is offline
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Oh, one more use I forgot about! Some of you may remember Gila III from 2000 (Team 64). We used a servo to release the gate that let out all of the balls in our basket into the trough.

The RED arrow is where the servo is mounted (I know its not very visible) and the BLUE arrow is what it was actually moving. There is another BLUE arrow thing on the opposite side, and it works almost exactly as the gear shifting mechanism in my post above. BTW, that is Mike Rush in the picture... my personal hero, and the man responsible for me being so involved with FIRST
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Last edited by WakeZero : 07-15-2003 at 12:54 AM.
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Unread 07-16-2003, 09:43 PM
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Veselin Kolev Veselin Kolev is offline
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Quote:
Originally posted by WakeZero
Rookie power

The airflow was superb, we didn't overheat once after they were installed, and being able to switch from high to low gear allowed us to have a quick/precise autonomous mode followed by a powerful low gear. It all worked out nicely =)

Quite impressive transmission. Even more so for a rookie team. But on the subject of motor cooling, we never did it. You think it would help, but not really. Blowing air on the motor doesn't do much. The motor doen't have enough surface area. Even if you make a custom heat sink and use silicon thermal gel, you still won't do much. You'll cool the outside of the motor, so you'll cool the magnets. You don't really cool the wire windings, and that's what you want to cool. Even if you manage to cool the wires, you won't lower the temperature too much, so you won't really improve the conductance enough to ever notice. Cooling works, but not with fans. For example, team 254 injected liquid oxygen (or something like that, i forgot exactly) from a can into their motors right before competing. This cooled the wires to about 250 kelvin (-23 C) or so they say, and I think that is close. This gives their robot a hugh advantage during autonomous mode, since they can really shoot up the ramp. But after a minute the motors heat up again.
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Unread 07-16-2003, 10:34 PM
sanddrag sanddrag is offline
On to my 17th year in FRC
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We used a heat sink and heat sink grease on each of our drill motors. This lowered the temp on the surface of the can nearly by half. They worked really great and we never had any overheating problems. Here's where you can buy them and a pic. You should also be able to find them at any quality hobby reatailer such as Hobby Town USA.

As for the colling spray, it is canned air that you buy from Office Depot or Staples or Fry's. When the can is turned upside down, the compressed gas comes out as an ice cold liquid spray. This works very well for cooling the CAN of the motor between matches. It is also very useful for cooling breakers before matches to ensure that they don't trip as much.

The reason I'm telling you all this is from something Andy Baker said that I agree with:
Quote:
There are so many advantages to giving these designs out. We as a team
feel that giving these designs to other teams “raises the bar” of FIRST robot designs and all of
FIRST benefits.
Last, I would strongly advice against cooling any part of the motor except for the can. You can accidentally freeze the thin insulation off the armature windings or even more easily crack a brush. If you absolutely must spray the inside or endbell at all, do it on a room temperature motor.

PS. Sometime hopefully before the end of the summer I will have a little white paper made of "Tips, Tricks, and Field Side Fixes" that will cover the things above and much more.
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Last edited by sanddrag : 07-16-2003 at 10:48 PM.
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Unread 07-16-2003, 10:41 PM
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Veselin Kolev Veselin Kolev is offline
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Quote:
Originally posted by sanddrag
We used a heat sink and heat sink grease on each of our drill motors. This lowered the temp on the surface of the can nearly by half. They worked really great and we never had
Yes, note the word "surface". It's inside that you want to cool. Anyway, we never use cooling and we never have problems. I frequently touch the motors to check their temperature. I do it right before we lift it out of the field, and they're never very hot.
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Unread 07-16-2003, 10:44 PM
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Jeff Waegelin Jeff Waegelin is offline
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Quote:
Originally posted by Veselin Kolev
Yes, note the word "surface". It's inside that you want to cool. Anyway, we never use cooling and we never have problems. I frequently touch the motors to check their temperature. I do it right before we lift it out of the field, and they're never very hot.
True, but the surface temperature is usually an indicator of the internal temperature. If it's hot, the inside surely is, and if it's not, the inside is probably cool (relatively speaking).
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Unread 07-16-2003, 10:50 PM
sanddrag sanddrag is offline
On to my 17th year in FRC
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My post above got posted without being complete , it's all edited and finished up now.
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Unread 07-17-2003, 12:00 PM
WakeZero WakeZero is offline
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Quote:
Originally posted by Veselin Kolev
Quite impressive transmission. Even more so for a rookie team. But on the subject of motor cooling, we never did it. You think it would help, but not really. Blowing air on the motor doesn't do much. The motor doen't have enough surface area. Even if you make a custom heat sink and use silicon thermal gel, you still won't do much. You'll cool the outside of the motor, so you'll cool the magnets. You don't really cool the wire windings, and that's what you want to cool.
First, thanks for the compliment =)

As for the cooling fans, I forgot to mention that they are all pointing in the same direction. So you have:

Fan --> Motor --> Fan

The arrows represent the airflow, and the left fan brought in the cool air while the right fan sucked out the hot air. I can see your point about just blowing cool air onto the casing, but we actually took the hot air out

It may not have made a huge difference, but we did notice that after we installed them we never overheated like we did a couple times before
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Unread 07-17-2003, 02:46 PM
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Quote:
Originally posted by WakeZero


It may not have made a huge difference, but we did notice that after we installed them we never overheated like we did a couple times before

Wow, our motors never came close to overheating. Maybe it's because you guys used the drills and we used drills+chippies. Looks like they help each other out enough so that they don't overheat. Cool!
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Unread 07-17-2003, 03:40 PM
sanddrag sanddrag is offline
On to my 17th year in FRC
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Quote:
Originally posted by Veselin Kolev
Wow, our motors never came close to overheating. Maybe it's because you guys used the drills and we used drills+chippies. Looks like they help each other out enough so that they don't overheat. Cool!
And let's not forget about gearing and wheel size. Those both play an important part in current draw and heating.
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