umm.. heat sinks. sorry, we're roookies.....

[Kevin Sevcik]

If it's going to have any hope of working, you need to have something thermally conductive between the heatsink and the motor. If you have another method for securing the heatsink to the motor, buy a packet of heatsink compound from your local Fry's or Radio Shack.

If you want to take care of it all at once, you can use thermal epoxy.
Here's a link to some cheap epoxy:
Thermal Epoxy
If you want it to be non-permanent, mix up the epoxy, then mix in about 33-50% plain old heatsink compound.

Chances are any heatsink compound is a bit of overkill, but if you are actually needing to worry about heatsinks, then you might as well make sure they work as well as possible, and it doesn't cost that much.

----------------

If we're worrying about extreme heat, Artic Alumina Thermal Adhesive says it's rated to over 150C I'd be worried about a motor that got hotter than that.
Arctic Alumina

[KenWittlief]

what kind of drive train are you using? how low is your transmission geared down?

ifyou are using either of the FIRST transmissions and you have the drill motors in low gear, and you have a two wheel drive set up (with skid plates or castors) then you will not need to put heatsinks on the drill motors.

they have blowers built into them, and as long as you dont block the openings next to the brushes, they will cool themselves.

the problem with heatsinks is, if your motors are getting so hot that you think you need them, you are destroying your motors and the heatsinks wont really help anyway. The reason is the current in the motor flows through the windings, which are on the armature in the center of the motor - the part that spins. The outside of the motor is only the magnets - so if the armature is getting so hot that the magnets are cooking, imagine how hot the windings are.

and when you put a heatsink on, what are you makeing contact with???? the metal case around the magnets - not the armature - so all you are doing is cooling the magnets down, and not providing any additional cooling to the windings - the part that WILL fail when it gets too hot (the insulation will bake off the wires, or the silver solder holding the wires to the commutator will melt.

Robots usually dont cook their drive motors unless they are geared up too high, or they are using tank treads, or 4WD with front wheels that dont slide sideways very easily. And even then, if you have your bot geared down enough (say 3 feet per second) then the motors will still be able to spin fast and keep themselves cool - on the windings, where it counts.

[Joe Johnson]

Originally Posted by KenWittlief

...the problem with heatsinks is, if your motors are getting so hot that you think you need them, you are destroying your motors and the heatsinks wont really help anyway. ...

I am with Ken on this one. 9 years in FIRST and we have never used them. We have cooked a fair number of motors in our day, but I doubt that any heat sinks would have helped.

I think it is better to pick the right motor(s) for the job and then gear them right than to bother with heat sinking them.

Joe J.

[KenWittlief]

someone else pointed out in another thread on heatsinks, if you are in the elim rounds and you REALLY want to cool your motors between matches then instead of using heatsinks

you can buy spray cans of component cooler (try radio shack). it use to be freon but now its something else - and you can blast your motors with it and get them icy cold for the next match

cool (pun!) thing about this, with the drill motors you can spray it inside the motor, where it needs it the most.

but there is another aspect to hot motors that everyone must keep in mind. When you play at the events the matches are 120 seconds long - no much time really

but before you ship your bot your team is going to want to practice practice practice with it for hours at a time

its best to design your drivetrain so it can be driven for hours without heating up - this will also mean you are not sucking your bats dead in a manner of minutes either - A well designed machine will only required a large amount of power when it is pushing or dragging something heavy - just driving around, collecting balls, steering around the field, should not require much power - if it does, your robot is fighting against itself.

[sanddrag]

Cooling the motor too fast is bad for the magnets and can crack the brushes rendering it useless. A light bit of spray on the outside is okay but I never get them too cold.

[Joe Johnson]

Originally Posted by sanddrag

Cooling the motor too fast is bad for the magnets and can crack the brushes rendering it useless. A light bit of spray on the outside is okay but I never get them too cold.

We have used the cool in a can stuff for years, freezing the snot out of the motors. While I am sure that it is not particularly good for the motors, we have not had a failure that we trace to this practice in 8 years of competitions.

Joe J.

[Wetzel]

I bet most people here will agree that rapidly cooling the motors will shorten the life span of the motors.
However, the typical use period is still far shorter then the design life of the motor. My dad has a 20 year old drill thats seen alot of use, and still runs fine.

Point being, yes, it is bad for the motor but it won't matter in the time it is needed to work.


Wetzel
~~~~~~~~~~~
Design to meet criteria, don't worry a whole lot beyond that.

[KenWittlief]

Some how I doubt you can cool a motor faster by spraying it will a coolant, than it heats up when the motor is stalled and draws a hundred amps for a second or two without spinning

the coolant isnt that powerfull - its not like a magic freeze ray - when you blast it on something in only looks like it has been instantly frozen because dry ice forms on a very thin layer on the surface.

its neat stuff - a powerfull tool when you need it - get a couple cans and experiment with it to get an intuitive feel for how it works - just dont....um....play with it in any way that can be harmfull or dangerous.

[Adam Y.]

We have used the cool in a can stuff for years, freezing the snot out of the motors. While I am sure that it is not particularly good for the motors, we have not had a failure that we trace to this practice in 8 years of competitions.

One thing that strikes me as dangerous to the motors is that condensation that would develop on something being blasted with that cold air.

[Solace]

we've never used heatsinks per se (although i guess you could argue that our mounting brackets have doubled as heat inks in the past). what we usually do is mount small muffin fans directly under the motors. if you drill holes in the floor of your bot directly under the muffin fan, it will suck the colder air up from outside the bot and directly into the motor. works pretty well, we never tripped our breakers last year even though we had a high speed bot (12 ft/sec) with a grossly inefficient turning process.

oh, and by the way, although gearing your bot to lower speeds like 3 ft/sec will definitely solve your overheating problems, you will be far too slow to actually compete in the game.

[greencactus3]

yeah... thanks everyone, I'm not worried about overheating yet. cuz we ahven't even finished the drivetrain yet. we reeaally need to work on it. I was just wondering. and if we have time, wouldn't having heatsinks be better than not having them even if we don't need them? unless we cover the openings (drill motor), is there a possibility its a bad idea to have them on?
you know, the " better safe than sorry" thing

[Alavinus]

A better option then the heat sinks would be to use the small muffin fans found in the KOP. They require less machining, cost less, and get the air to where it is needed. (The inside of the motor) The fans can be zip-tied on and will aid in cooling.

Of course in your'e really worried about heat, there are always those other fans in the kit...

[Wetzel]

Originally Posted by greencactus3

yeah... thanks everyone, I'm not worried about overheating yet. cuz we ahven't even finished the drivetrain yet. we reeaally need to work on it. I was just wondering. and if we have time, wouldn't having heatsinks be better than not having them even if we don't need them? unless we cover the openings (drill motor), is there a possibility its a bad idea to have them on?
you know, the " better safe than sorry" thing

We've never had hinksinks, nor had any problems attributed to overheating.

We've always been to close to being overweight to worry about it.

Question: Whats the best way to cool most motors, like the drill motors we have?
Answer: Run them full speed at no load.

If you run the drill, you will notice a draft from them. They are designed such that they will such air in and air cool the windings and other hot things. This is then exhasted (the draft) out the back. Cover those, and you will likely overheat and get nice baked motors. Leave them clear and don't worry about heatsinks.


Wetzel

[greencactus3]

just one more question. do the drill motors suck in air going in reverse too?

[Rhs953]

you can drill a hole on the bottom of then and mount them with screws....:/