# Cooling airstream direction



## major (Apr 4, 2008)

z_power said:


> Are there any disadvantages of airflow direction reversed from original? Factory setup was radial fan on drive end sucking air along entire rotor like this:
> outside > CE > armature > DE > outside
> Since I'd use forced cooling I'm thinking about removing original fan and pushing air into drive end, this way blowing brush dust shortest way out of motor.
> outside > DE > armature > CE > outside
> I know that comm area is to be cooled most intensive so putting it on an end of airflow might not be the best idea, what's your opinion?


Hi z,

It probably won't matter which way the wind blows 

There are number of reasons why most motors use the radial fan at the DE. You hit on the reason most commonly given. Especially if your application is a street traveler opposed to heavy overloader, the brushes may not actually be the hot spot. But then why do you expect all that brush dust?

Personally I liked to use both the internal fan and external blower. Sorta belt and suspenders. The shaft mounted fan works better at high rotor speed than most blowers. But at low rotor speed or zero, the blower does the task.

Regards,

major


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## Woodsmith (Jun 5, 2008)

It's an interesting question, airflow direction.
On my 11" motor there was no fan. The armature had axial holes through it, with ventilation holes at each end of the frame end caps. I wasn't sure which way the airflow would have been from original as there was grease, muck and brush dust everywhere.

Run at 12v with a smoke test showed that the natural airflow was from DE to CE through the armature.

I will be fitting an axial flow fan at the CE for forced ventilation.

I have an open chain drive at the DE and have no idea if I should be forcing air through the motor onto the chain or sucking air from the chain through the motor.
Pondering motor dust (?) going on the chain or chain oil going through the motor.


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## z_power (Dec 17, 2011)

Major - I don't have even 2% of your experience with motors, I just think brush dust even in "normal" quantity is dirty and conductive - better blow it away instead of feeding motor with it.
Original fan on my motor has straight blades so it isn't super efficient, removing it would allow me to: 
a) use taper lock on "flat" part of shaft instead of custom machined coupler for conical shaft end 
b) cut this cone end and gain ~6 cm space in transverse engine bay - motor can be these 6 cm closer to transmission 
I'd need custom endplate to go this way but it doesn't add to much to amount of work on adapter plate. I've access to machine shop with equipment to do it right at first take.
The easiest way for delivering air to drive end seems to be placing blower so it pumps filtered air into transmission bellhousing, adapter plate and motor endplate must allow airflow - cutouts etc.


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## major (Apr 4, 2008)

z_power said:


> Major - I don't have even 2% of your experience with motors, I just think brush dust even in "normal" quantity is dirty and conductive - better blow it away instead of feeding motor with it.
> Original fan on my motor has straight blades so it isn't super efficient, removing it would allow me to:
> a) use taper lock on "flat" part of shaft instead of custom machined coupler for conical shaft end
> b) cut this cone end and gain ~6 cm space in transverse engine bay - motor can be these 6 cm closer to transmission
> ...


I don't see a cooling problem with reversing the air flow. But I don't see a brush dust problem on the regular flow. It sounds like you have other reasons to go that route. Cool  

Just pay attention to positional as well as dimensional tolerance when altering the shaft and end head. And likely the armature was balanced with the fan in place originally, so plan on re-balance.


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## z_power (Dec 17, 2011)

major said:


> Cool


 pun un/intended 


major said:


> Just pay attention to positional as well as dimensional tolerance when altering the shaft and end head. And likely the armature was balanced with the fan in place originally, so plan on re-balance.


Balancing - how about taper lock, are it's parts balanced neutral? Would it be useful to balance rotor with taperlock on it's place?


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## major (Apr 4, 2008)

z_power said:


> Balancing - how about taper lock, are it's parts balanced neutral?


I think so. I've used them (a while back) and did not balance with them. In one case, ran to over 10kRPM with no apparent issue.



> Would it be useful to balance rotor with taperlock on it's place?


Seems like a good idea, but might be tough to do. Usually balance is done on the bearing journals, so you'd be taking it off. I guess you could scribe it and reassemble it in the same orientation.


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