How To Ice Up Your Motor? (Cooling Ideas)

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New Concept

Seems that air conditioning is the ultimate answer for cooling. Here's what you need:

1. Compressor

2. Radiator

3. Pressure Nozzle

...this system will act like "air conditioning" and provide cooler air than a fan fed system. It's still a good idea to have the air intake be on the side with the brushes.

 

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Now the quest is to find a 12 Volt air compressor that does not use too many amps. This might be the "achillies heal" of this idea. (I've been looking at some electric air brushes that might do the job, but they don't list the actual amps)

If anyone knows of an air compressor that is "thrifty" with the amps please post that information here.

 

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Throttle Controlled Fan Cooling

It seems kind of obvious that the fan should be connected to the throttle so that full throttle means full fan. This also allows you to stop riding and not have to turn off some fan switch when you do.

Is there plenty of voltage in the throttle to use some of it for such a purpose?

Circuit realities?

 

[fechter]

You could connect the fan to the motor, so it gets the same voltage (use a resistor if necessary to lower the voltage).

I found it useful to have the fan run full time so it can cool when going downhill or at a stop. The armature has enough thermal mass that it takes quite a while to change temperature. The power consumption of the blower is quite small compared to the main motor.

Some kind of temperature sensor in the motor to control the fan might be a good solution. In the winter, the fan might never run. When the motor is hot, the fan runs until it isn't. Many computer CPU cooling fans have a temperature control that varies the speed of the fan.

With a brushed motor, it's hard to measure the temperature of the armature, but a thermistor located as close as possible to the windings might be good enough.

 

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The armature has enough thermal mass that it takes quite a while to change temperature. The power consumption of the blower is quite small compared to the main motor.

This is something that I exploit on my bike right now. If I start the ride fairly conservatively (as far as power and heat) I can get the 2 miles to my track without any serious heating taking place. Then I open it up and produce some heat. Then the batteries eventually start to sag and the motor heats up and so I limp home. When I get home the motor is very hot, but the batteries are used up anyway so it doesn't matter.

If I had a longer runtime then heating will be even more of a problem and you're right you might as well run the fan all the time. I suppose a switch is the easiest. There are times when I want absolute quiet as I coast through some serene stretch of road... I go "full race" a lot, but now with the heat building up I'm often riding without my protective gear and just shorts and a t-shirt, gloves and a helmet. Dressed like that you just putt around and feel the breeze... (not a time that you want a fan blowing hard)

 

[JEB]

Hi, what one needs is a high speed brushless pressure blower;

I picked one up from all electronics (year or more ago)

-- 12vdc 1.8 amp 18,200 rpm p/n 071036 series 3029rf eg&g rotron rcbp/vs203-ccw-fx2c-n-3029rf --

It looks like a expensive unit, I have not been able to find one on the net. For its size I have never seen one that will put out so much air with a high pressure. Inlet & outlet 5/8 inch id ,over all 3 3/8" blower od 2 3/4"~.

If anyone can fine some let me know!

 

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With this motor it's small size is going to make any sort of velocity based fan not effective. It seems to me that a diaphram like device like an electrical bike pump is a better way to go. Or maybe something like a worm gear that compresses in a long tube. The motor comes with three holes on one side and they pass through the motor from one side to the other and back. So the easiest way would be to insert air in one of these holes and then let it dribble out the other two. The air volume is going to be small... all that is needed is a positive FORCEFUL flow. I'd be afraid that a fan would simply back up into itself too easily and you would get very little actual air passing through such small holes. The bigger motors have larger holes and so the fan related solutions look better.

Thoughts?

 

[vanilla ice]

That jaycar fan only draws .85 amps, you can get similarly sized ones that draw over 2 amps. Well if space is a concern and you need more cfm you could. The one I got for a dell server has auto rpm adjust with increased temps. So it should only draw the full power when the the bike needs the cooling the most. They're on ebay all the time for like $15.

 

[TylerDurden]

Small compressors deliver air in CCs... you want CFt.

A small turbine style Like Richard's or blower like Reid's will help keep the pressure on AND move enough air to cool the motor. More holes to reduce the restrictions would help.




.

 

[Malcolm]

What Tyler said: you need pressure AND flow. I have a small diameter centrifugal fan unit on my bike. It does the job, keeping the motor temperature down to 50ºC or so, but I'd like more flow so that i can increase the current a little. The cheapest option would be to find a small centrifugal heater blower from a car, but I'm also considering one of the smaller versions of these: http://www.gbdmodelaircraft.com/products.php?id=96
Should make an interesting noise too!

 

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Well I might have to go ahead and start drilling into the motor to open up a big enough hole to pass some air through it with a fan. The advantage of something like a diaphragm pump (like the fuel pump in a car) is that you could use a very small hole to pass the air through.

Water cooling is another option that I'm reconsidering for these small motors...

These really small motors just don't have the room to pass much air through them without some forceful pressure. Water transfers heat at a rate that is something like 25 times the rate of air. But then there's that nasty problem of the heat being most critical in the rotor and not the stator and it's the outside that the water cooling would be easiest to implement.

Also... what about VACUUM pressure verses positive pressure?

When you create a vacuum it lowers the pressure and lowers the temperature. So if your motor is small and has a tightly closed seal to it the idea of a vacuum instead of a blower makes more sense.

 

[TylerDurden]

Achieving a vacuum requires restricting the airflow.

You want as much air moving past the coils as reasonably possible.

 

[Malcolm]

If you want to get clever you could try injecting liquid butane (from one of those neat little lighter fuel canisters). As the butane evaporates it will extract its latent heat of evaporation from the motor and keep it nice and frosty

 

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You want as much air moving past the coils as reasonably possible.

But in order to get air to move through a small hole you have to either compress it or create a vacuum to suck the hot air out. The issues are different for big motors verses small motors because the bigger motors have more room to allow air to pass. The small motors are very tight and can't pass much air naturally. Unless you drill big holes into the motor (which potentially weakens it... at the same time you are overvolting and doubling the power output ) you have to force air through very small holes. The vacuum approach seems better suited to the smaller motor.

A high volume of air makes no difference if it can't penetrate the shell of the motor.... it's more important to be able to be certain to get SOMETHING through rather than blasting from the outside with a fan that does next to nothing. Most regular fans back up when confronted with a restriction and cannot force even 1 psi forward. A diaphragm pump might be able to pass air at 3-4 psi. (and the diaphragm operating in reverse as a vacuum also reduces the temperature)

A very low powered 1 psi diaphragm pump could do as well as a larger fan because the fan is designed so that the other side is supposed to be unrestricted...

 

[Drunkskunk]

if you run air through in a vacume, you'll lower the air density inside, and reduce it's ability to cool. you might get more air through, but its cooling effect will be reduced.

a normal blower fan, as you stated, will stall at pressures above just a few pounds, but an impeller won't, and can generate many mpounds of pressure..

the trick is getting enough air through to make a diffrence. air realy can't hold that much energy in heat, so you need large volumes of it to effectivly cool anything. Unless this motor is the size of a watch motor, a diphram pump isn't going to have the volume of air needed. you'll need a high CFM to do any effective cooling.

 

[fechter]

With the centrifugal blowers I use, the pressure difference is less than 1 psi, so it doesn't change things much whether you suck or blow.

If you suck, the heat from the motor heats up the blower.

The butane idea is not too bad

Actually liquid CO2 would be pretty good for short runs, like a dragster.

You really need big holes and lots of CFM. That Unite motor is about the same size as my Zappy motor, so I know it can be done. Reid Welch had one just like that with forced air. It worked.

 

[vanilla ice]

The 1018 Reid used at least had a semi-finned zinc outer case. Looks like the geared 1016 has a steel outer case with no fins, so it could probably benefit from the blow even more.

 

[Malcolm]

Actually liquid CO2 would be pretty good for short runs, like a dragster.

How about methanol mist? Safer than butane, lighter than a CO2 tank. Put it in a perfume spray with remote activation on the handlebars. Boiling point 64ºC, latent heat of vaporization 1008 joules/gram. Cool!

 

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I agree that the "Conventional Wisdom" is that you need to bore some big holes and then use a centrifugal blower which works like crazy to push the air, but in reality they only really push 1 psi worth. Seems to me that a simple diaphragm, something that forces little bits of air through a small tube, could achieve the same result and not require a bulky fan. My thinking goes like this:

Big centrifugal blower can "in theory" push (say) 1 GPM of air, but in reality it actually can only push 0.25 GPM because it gets so backed up.

Small diaphragm pump can only push 0.25 GPM, but the holes needed to pass the air are pretty insignificant because what air is pushed is "forced" and not "thrown". Rather than trying to carry the momentum of the air through the motor you instead have a "conveyor belt" of air that cannot do anything but move forward.

It's sort of like a jet engine verses a piston engine... if the jet can't get enough air to pass through it stalls. The piston driven solution would give a more certain exchange rate of air.

The main issue is drilling lot's of holes in the motor... if you can achieve the same result and keep the motor intact then this is an advance in thinking.

Does my logic make sense?

 

[vanilla ice]

Hrm, I think the natural gas line to our place is only 1psi. Flows enough for our 200,000 btu water heater and several other appliances to run at the same time. I was surprised when I found out how low the pressure was.

Be interesting to test both methods of cooling a motor with a temp meter back to back. Also it is a little scary having huge holes in your motor where debris or water can get inside. Not a show stopper type issue, but still a little worrisome.

 

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Here's an example I found of such a diaphragm motor. At a rate of 1.0 liter per minute that should empty the air inside the motor many times since there is probably less than 0.1 liter of actual free space inside these small motors. It also only draws 120 mA (0.12 A) so that's very low.

No more need to drill holes into your motor?

I wonder how much these things cost?

(ouch.... the sample price is $140)


http://www.xavitech.com/products.htm

 

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These are more affordable, but might suck up some current... $10 each.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=43520

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=4077

 

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Don't Forget the Fish! Only $9.

http://www.thatpetplace.com/pet/group/2627/product.web

OSI Backup air pumps let breathe a little easier the next time the power to your aquarium is off. These handy devices are designed to provide battery-powered air to your tank in the event of power outages, transport, or can act as an aerator on fishing trips. Low energy consumption designs are designed for long term use.

 

[vanilla ice]

That stuff would melt if you tried to use it as a vacuum pump. My motor sometimes gets hot enough that I can't hold my hand to it.

 

[TylerDurden]

That crap will be about as effective as trying to put out a California wildfire with a squirtgun. :lol:

If you are squeemish about drilling holes, you'll need a high-pressure high-volume blower/sucker like a mini supercharger or shop-vac.

Think "impeller", forget diaphram or piston.