Quick Q for "noob" at first

[V8GTORacer]

For cooling of the bot, are we allowed to use regular computer fans (in addition/to replace supplied fans)? I heard somewhere that last year we werent and couldn't find anything in this year's manual about it.

[Al Skierkiewicz]

Some teams find that the mechanical design they have chosen causes the motors to run hot. Frequently teams use a 12 volt fan blowing directly on the motors. You can find these fans at Digikey or any of the other common vendors. There is no real need to cool the other components, the speed controllers have their own fans and the rest of the electronics do not run hot in normal operation..

[John Gutmann]

Yes, you can use the computer fans.

It helps if you mount the fan to the same plate you mount the motor to.

[coastertux]

Make sure you mount the fans so nothing can get pushed into them...
It's no fun bringing a 10,000 RPM fan to a complete stop with your finger (or any other object for that matter)!

[V8GTORacer]

ok thanks guys

[Conor Ryan]

Heres something intresting, good topic.

Now most of the motors in the kit tend to run pretty cool, and the further away from stall torque they are, the cooler they will run. From experince and what I've heard from other teams is that if any motor in the Kit run hot, it's the small Fisher-Price motors (not the Really Big Cims, or the Mini Bike Motors) What do people do to combat that effectively?

Fans do take a bit of time to move the heat out of the area with the motor, whats an easy way of speeding this up? Add a heat sink. How? Take some copper or the best heat conducting material you can find, and wrap some of the motor in it. Add a fan or two, and it'll run nice and smooth. The kit muffin fans are good enough, if you wanna go and deck your robot out in all fancy computer case fans, check the electronics rules first, and check the connections on them.

[SoftwareBug2.0]

Originally Posted by Conor Ryan

...if any motor in the Kit run hot, it's the small Fisher-Price motors (not the Really Big Cims, or the Mini Bike Motors) ...

...Add a heat sink. How? Take some copper or the best heat conducting material you can find, and wrap some of the motor in it. ...

My team did this in 2004. We used the drill motors which did tend to get hot.

We had two big aluminum blocks that were both mounts and heat sinks. Each piece had half of a circle on one side, and then screwed together to make a whole circle that the motor would go into. We used some thermal paste next to the motor and where those blocks attached to our main frame. That part of our frame was fairly heavy stock so that helped transfer even more heat.

[KenWittlief]

At this point in the design cycle I would recommend looking at your drivetrain design, to keep the motor RPMs high, so you dont need a fan

it should be easier to design in one more set of gears in your drivetrain, to get the motor RPMs up, than to design for bad design and fabricate monster heat sinks and fans.

You can run those drill motors all day long, at their intended speed and load, and they will not get hot.

Every team should take a motor apart (one you dont need anymore) and see whats inside. The heat that is generated in a stalled motor comes from the armature, the part that spins. This does not touch the case of the motor at all, except at the bearings. You will also discover the drill motors and FP motors have blowers built into them, by the commutator. This blower does an excellent job of pulling air through the motor where you need it: across the windings (as long as you dont block the openings where the air comes out).

If your motor gets so hot that you cant touch it, and it smells like burnt varnish, the armature windings inside must be almost glowing! Blowing air across the case will only cool the magnets that are in contact with the case. The windings on the armature will continue to cook.

[KathieK]

V8GTORacer - welcome to FIRST and to ChiefDelphi! We hope you have a great rookie season this year and don't hesitate to ask questions in these forums - just a hint, though, you might want to look through all the different forums that are available to see if there is one that is more specific to your question. For example, this topic might be better addressed in the Technical > Motors section (click on the link to ChiefDelphi forums at the top of each page and it should bring up the screen with all the topics listed on it) rather than in the General section. Also, CD encourages all users to use the search feature before starting a new thread just to be sure that someone else hasn't already started a thread on the very same topic!

Good luck to your team!

[SoftwareBug2.0]

Originally Posted by KenWittlief

At this point in the design cycle I would recommend looking at your drivetrain design, to keep the motor RPMs high, so you dont need a fan

it should be easier to design in one more set of gears in your drivetrain, to get the motor RPMs up, than to design for bad design and fabricate monster heat sinks and fans.

You can run those drill motors all day long, at their intended speed and load, and they will not get hot.

...

Of course you should try to design things so they don't get hot, but this was using the kit gearboxes to the kit 12" wheels, and the motors certainly did get hot, as did the blocks surrounding them and to a lesser extent the parts of the frame they were attached to.

On a FIRST robot, you're likely to be using parts outside of their intended specifications even if you think it should be totally safe.

[KenWittlief]

Originally Posted by SoftwareBug2.0

Of course you should try to design things so they don't get hot, but this was using the kit gearboxes to the kit 12" wheels, and the motors certainly did get hot, as did the blocks surrounding them and to a lesser extent the parts of the frame they were attached to.

ok, thats a good starting point. So what could you do differently this year?

smaller wheels?

not use skid steering?

limit the amount of power the driver can command to the motors if they are stalled?

Use the kit gearbox but add one more stage of gear reduction before the wheels?

this is the time to make those decisions.

[SoftwareBug2.0]

Originally Posted by KenWittlief

ok, thats a good starting point. So what could you do differently this year?

smaller wheels?

not use skid steering?

limit the amount of power the driver can command to the motors if they are stalled?

Use the kit gearbox but add one more stage of gear reduction before the wheels?

this is the time to make those decisions.

That year, our team had neither the expertise nor the time to go back and do things right, so we did what we could when we realized that there was a problem.

I and my team members understand that it was not ideal. The next year, which was last year (I have mentioned that the crazy heat sinks were from 2004 and on drill motors) we did not have the same problems.

A big element of FIRST competition is thinking on the fly. At this point, you should be trying to design a system that doesn't have motor stalling and overheating problems, but it's good to know some techniques that have worked in the past, even if they're not ideal. You might need to use them.

BTW, I'm also thinking that normal, non-kit, electric fans would not be legal.

[Q Branch 4327]

Originally Posted by Conor Ryan

Heres something intresting, good topic.

Now most of the motors in the kit tend to run pretty cool, and the further away from stall torque they are, the cooler they will run. From experince and what I've heard from other teams is that if any motor in the Kit run hot, it's the small Fisher-Price motors (not the Really Big Cims, or the Mini Bike Motors) What do people do to combat that effectively?

Fans do take a bit of time to move the heat out of the area with the motor, whats an easy way of speeding this up? Add a heat sink. How? Take some copper or the best heat conducting material you can find, and wrap some of the motor in it. Add a fan or two, and it'll run nice and smooth. The kit muffin fans are good enough, if you wanna go and deck your robot out in all fancy computer case fans, check the electronics rules first, and check the connections on them.

I have a question for you we have plugged in fans to a main source of power and now they are burnt out would u have any clue why?

[EricH]

Originally Posted by Q Branch 4327

I have a question for you we have plugged in fans to a main source of power and now they are burnt out would u have any clue why?

Can you give any more details on the connection and where the fans are? At a guess, you ran 'em through a breaker that was too big--I'd suggest no more than a 20A breaker, and several fans on it at that.

I've never seen a fan fry if connected to its speed controller's inputs, BTW.


Oh, and one other thing:

Holy ancient thread revival Batman!

[Alan Anderson]

Originally Posted by Q Branch 4327

I have a question for you we have plugged in fans to a main source of power and now they are burnt out would u have any clue why?

What kind of fans, what voltage are they designed to run at, and what voltage did you connect them to?

(After a quick reading of your question, my first impression was that you connected a 12 volt fan from the Kit of Parts to a wall outlet providing 120 VAC. That would indeed burn them out quite effectively.)