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Old Dec 12, 2011, 09:01 PM
Bypass Ratio = Infinity
scatsob's Avatar
United States, NC, Jacksonville
Joined Apr 2006
1,653 Posts
Man that 3994 Turnigy motor is heavy for 90mm planes. I wish they would come out with some motor in different lengths.

I guess I did not think about the insulating properties of a sealed motor and agree that an open motor will cool faster than a sealed one but it makes little difference while the motor is running.
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Old Dec 12, 2011, 09:14 PM
Fly it like you stole it !
bobbit4447's Avatar
Australia, QLD, Coolum Beach
Joined Oct 2011
372 Posts
erg
Quote:
I wish fans manufacturers would give calculated rpm to thrust figures
I think the reason for not doing it is all the variables that affect thrust (duct configeration, air density etc) so that there is not 1 simple answer. Commercial fan manufacturerers do graphs for that reason.
Quote:
1900kv motor will give > 9lbs of thrust on 6s 21 volts around 140 amps
Doing the calculations the 1700kv Tacon will do 3.2 kg thrust - my AUW will be 3.2 kg giving me 1:1 thats OK for me - just have to stop it from frying itself !
GOOD NEWS
Postie has just delivered my CS90/12 - It has slots on the inner drum - This will allow fitting 7off x 55mm aluminium fins to the motor can. Maybe they know something we are just finding out. Fins would probably have to be glued on. Whats epoxy like at transferring heat?
B
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Old Dec 12, 2011, 09:51 PM
3DHOG
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USA, CA, Aromas
Joined Sep 2010
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all of the heat created by your motor is lost to heat transfer to the air, the surface area of the motor determines how fast it can dissipate heat to the air so larger diameter and longer can motors do this better than smaller motors. adding a heat sink increases the heat transfer area and thus improves it further add 150mph airflow increases the transfer rate and you get an ideal cooling condition. this is what allows us to run these motors well over their stated watts/amps ratings. having cooling holes in the end caps of your motor is a very good thing for cooling, when the fan is running and high airflow is running thru the duct air pressure differences are created in front and behind the motor that causes air to flow thru the motor. I dont remember but it seems logical to think the air is drawn thru the back of the motor but I think I remember reading that it actually draws thru to the front of the motor. in any case it doesn't really matter you just need to know that air goes thru the motor and that further increases the heat transfer area. so cooling holes are good
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Old Dec 12, 2011, 09:52 PM
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United States, TX, Grand Prairie
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Quote:
Originally Posted by bobbit4447 View Post
erg

I think the reason for not doing it is all the variables that affect thrust (duct configeration, air density etc) so that there is not 1 simple answer. Commercial fan manufacturerers do graphs for that reason...
Calculated RPMs are pretty static and they can throw in sea level etc, not doing it leaves folk guessing. Intake lip and no thrust tube at said temp and sea level can give a person a good idea of what motor to buy and cell count
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Old Dec 12, 2011, 10:08 PM
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Joined Apr 2004
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Hi All

This 12 blade fan is balanced pretty good as is. However, the adapter on mine is a bit loose on the motor shaft (on all my motors) so it creates a wobble if not centered.

So after a few tries to correct with luck of the draw, I got tired of screwing around ( and don't want to break another one).

Here's what I did to center it. 10min and perfect. Harbor Freight, $20.00.

Really helps.

Very Smooth.

Shroud haoya
motor 1650kv outrunner
CS 12blade

Lets see what happens on 6s.

By the way, the 1650kv outrunner motor I have is 9oz and the Tacon 1700kv 1lbs 1oz

Needs an intake duct adapter for my K&A F-100
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Old Dec 12, 2011, 10:09 PM
Fly it like you stole it !
bobbit4447's Avatar
Australia, QLD, Coolum Beach
Joined Oct 2011
372 Posts
Quote:
Originally Posted by erh7771 View Post
Calculated RPMs are pretty static and they can throw in sea level etc, not doing it leaves folk guessing. Intake lip and no thrust tube at said temp and sea level can give a person a good idea of what motor to buy and cell count
Agree they should be able to give figures +/- 20%
B
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Old Dec 12, 2011, 10:17 PM
3DHOG
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USA, CA, Aromas
Joined Sep 2010
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Quote:
Whats epoxy like at transferring heat?
not good, you need to find a good high temp epoxy that is good to 300+ degs, JB weld comes to mind I think its good to 600f or 500F Machinable Aluminum Putty, Pre-Measured Kits Epox-EEZ™ RK454
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Old Dec 12, 2011, 10:20 PM
edf flyer
Mannyman535's Avatar
United States, CA, Marina
Joined Feb 2009
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im thinking of using the rotor out of this fan and put it into another shroud that accepts 36mm
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Old Dec 12, 2011, 10:23 PM
3DHOG
jcdfrd's Avatar
USA, CA, Aromas
Joined Sep 2010
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Originally Posted by Mannyman535 View Post
im thinking of using the rotor out of this fan and put it into another shroud that accepts 36mm
or have Tam make you an aluminum motor heat sink adapter to fit the cs fan
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Old Dec 12, 2011, 10:25 PM
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United States, TX, Grand Prairie
Joined Nov 2005
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Originally Posted by SCALECRAFT View Post
Hi All

This 12 blade fan is balanced pretty good as is. However, the adapter on mine is a bit loose on the motor shaft (on all my motors) so it creates a wobble if not centered...
If you have a 3/4 motor shaft try it on that, it'll center better..the 70mm have the same issue; if the motor shaft isn't long enough it'll vibrate at certain RPMs.

Quote:
...Here's what I did to center it. 10min and perfect. Harbor Freight, $20.00...
I don't get it...what did the HF tool do?

Quote:
...Needs an intake duct adapter for my K&A F-100
Does the intake adapter you're talking about cover the blades that are sticking out of the hoaye shroud? I tried to fit mine in the haoye shroud and the shroud wasn't deep enough

If so does K&A sell the intake duct adapter by itself?
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Old Dec 13, 2011, 01:07 AM
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South Africa, GP, Pretoria
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Originally Posted by bobbit4447 View Post
Graham mate - You gotta worry about something called a SUXFLY !
Do you have a link for data on this one?
B
Hey B

I am sure this name had to be at the bottom of the pile....
Here is a pic and I will soon find out if it Sux or if it fly's.
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Old Dec 13, 2011, 01:32 AM
Fly it like you stole it !
bobbit4447's Avatar
Australia, QLD, Coolum Beach
Joined Oct 2011
372 Posts
Quote:
Originally Posted by Graham d View Post
Hey B

I am sure this name had to be at the bottom of the pile....
Here is a pic and I will soon find out if it Sux or if it fly's.
Fingers crossed !
It looks like a Tacon under a different brand - except colour.
B
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Old Dec 13, 2011, 02:58 AM
edf flyer
Mannyman535's Avatar
United States, CA, Marina
Joined Feb 2009
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Quote:
Originally Posted by jcdfrd View Post
or have Tam make you an aluminum motor heat sink adapter to fit the cs fan
Tams a very busy person. But when I see him I'll ask him
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Old Dec 13, 2011, 08:15 AM
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FlyBoyTha1's Avatar
The Greater Bay Area
Joined Sep 2008
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I'll be trying out these C/S 12 Bladed Rotors in these TamJets TJ90MM 7 stator shrouds

These shrouds are setup for a 40mm motor cans, i do believe he has them for 36mm motor cans also
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Old Dec 13, 2011, 08:29 AM
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Joined Apr 2004
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Quote:
Originally Posted by erh7771 View Post
If you have a 3/4 motor shaft try it on that, it'll center better..the 70mm have the same issue; if the motor shaft isn't long enough it'll vibrate at certain RPMs.



I don't get it...what did the HF tool do?



Does the intake adapter you're talking about cover the blades that are sticking out of the hoaye shroud? I tried to fit mine in the haoye shroud and the shroud wasn't deep enough

If so does K&A sell the intake duct adapter by itself?
Hi. I have motors with .75" shafts, but still upon tightening, mine are off center more than I like for a finely machined adapter. Even if the shaft was 1", probability and luck is more involved than the size of the shaft when it's loose. I can see the vibration problem though.

The dial indicator easily shows how much and which side needs to be tighten or loosened to get centered as one turns the rotor by hand. Each set screw position I have numbered from 1 to 4 on the spinner to keep track.

True, hoaya shroud falls short of the rotor coverage, but I'll make a duct to seamlessly flow into the shroud and eliminate that problem.

K&A does not have what I need. We make a lot of our own composite stuff as needed. Well, when time permits, and motivation is high.

Steve
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