Any EDF flyers out there? Need input on EDF as AC system blower

[Discseven]

Am doing custom work on rear fender condenser with a challenge to solve. The challenge is to move/blow a measurable volume of air from an intake located ahead of the rear wheel to a condenser air-bucket located behind the rear wheel. (Spal fan has already been considered. Want more air than Spal delivers. Bilge blowers are also off the menu.)

Potential solution is an EDF. Good news = size and thrust work. A 100-90 mm unit would fit with 4" ducting planned. Challenges = a signal wire exists to control the engine's speed. Don't want that. When AC comes on... jet engine needs to come on. Might need to tests speeds and set ON speed so thrust is not TOO MUCH. Also am not familiar with what noise these engines make... moisture considerations... durability as an AC component... electrical service from 12v car battery.

...Need help sorting these challenges out.

[dad911]

I don't fly ducted fan, but planes & helicopters.

Brushless motor, You'll need a speed controller. And a servo tester to adjust the speed. Remove the signal (relay or kill the power) to the servo tester and it should kill the fan. (3S rating is about 12v)

https://hobbyking.com/en_us/12-blade-high-performance-90mm-edf-ducted-fan-unit.html
https://hobbyking.com/en_us/warhead-3545-1350kv-edf-motor-90mm.html
https://hobbyking.com/en_us/hobbykingtm-servo-tester.html
Speed controller (ESC) https://hobbyking.com/en_us/multi-rotors-drones/speed-controller-esc.html

You will need 5-6v for the servo tester. Either build one with a few caps and a voltage regulator, or get something like this: https://hobbyking.com/en_us/kingkong-5v-3a-ubec.html

EDIT: Quite a few speed controllers (ESC) have built in supply (5.5-6v ubec) which can be used to power servo tester.

I'd be a little concerned about a filter/screen in front of the blower, and duty cycle of the fan(not really meant for long periods of time) .

[SCadaddle]

I've been flying model airplanes for the last 42 years, and dabbled quite a bit in the electric models a few years ago. That being said, remember:

Amps x Volts= Watts

So you'll need to determine which brushless electric motor, Watts wise, will be most efficient for a given fan diameter and number of blades. Once you've got that, and you know the voltage the charging system of the car is delivering, say 14 volts, then will you be able to work the equation to find the number of Amps you will be drawing. With Lipo cells in a model, you want to have the wiring from the battery to the ESC (Electronic Speed Control) as short as possible. You also don't want to extend the wiring from the ESC to the motor.
A fully charged Lipo battery delivers 4.2V per cell. So a 3S pack is right at 12.6V "hot off the charger". Nominal voltage is 3.7V per cell. That's why you'll see the 3S batteries advertised as 11.1V, a 4S as 14.8V and so forth all the way up to 6S. Then you've got the "C" rating of the Lipo batteries, or how hard you can discharge them before they get too hot, swell up permanently and are toast.

With all that said, I would surmise a 100mm EDF would really require more than a 3S rating battery, minimal 4S, and the weight of the model airplane that could be flown "efficiently", with regard to thrust and flying weight (including the Lipo battery) would yield a flight time of no more than 10 minutes---at partial throttle. The proper ESC is going to get significantly warm, probably HOT in that amount of time, any more than that and it will "let out the magic smoke". You'd probably have to run a significant sized wire from the car battery to the ESC because you will be pulling a LOT of Amps to run the motor. You're not going to tap into the tail lights here!

Bottom line: I wouldn't attempt it.

[Discseven]

Thanks for input guys. A few notes back for you.

1. The ESC is clearly a problem---it has to be deleted from system. Fan needs to be either ON or OFF. If there's no way to "trick" the speed controlled motor... an ON/OFF motor needs to go in in place of the speed controlled unit.

2. Duty cycle of fan is "not meant for long periods of time." That's a good point. Obviously changing the fan every so often is not appealing. Whenever the car is running the AC will too meaning the fan too. (I'm in Miami.) What do you suggest will have the greatest durability---metal, plastic, or carbon fiber fan? Am willing to test the duty cycle (by default) but might as well start out with most durable unit.

This unit (below) is 101mm OD which fits planned 4" ducting perfectly. To swap out speed controlled motor for 12v ON/OFF a 40mm motor housing with 8mm shaft is needed. Am guessing at needed RPM being in 15,000 - 20,000 range. Will sort out later if that's too much or too little RPM. If you know of any 12v motor that fits this... please advise.

[dad911]

Replace flight battery by connecting to 12 car battery, about the same voltage as 3 cells. Replace receiver with servo tester.

You can cut 12v power to turn on and off. Why is the ESC a problem?

[Discseven]

Originally Posted by dad911

Why is the ESC a problem?

Thanks for diagram Dad911 and "replacing receiver with servo tester" note.

Not liking ECS because: is more hardware, more cost, more stuff to potentially go wrong compared to having 12v high RPM motor that turns ON/OFF.

What's your take on this union:





That's a 100mm JetFan. Comes without motor. Motor is 12v static 18,000 rpm. Need to modify fit of motor housing to turbine slightly and also fan-to-shaft fit but is doable.

Am thinking about durability as mentioned.... general life cycle operation. There's also moisture and debris intake to address. Also wondering about noise levels. Am seeing this path---provided I dive in---being experimental until any number of challenges are sorted.

Your input is much appreciated.

[dad911]

We've used rs550s, different brand, for First Robotics Competition. Basically they are inexpensive drill motors, typically geared down. Don't last if stalled or overheated. Don't block those front vents. As I recall motor built-in fan pull air in back, and out those front vents(by shaft)

Brushed motors with plain bearings will likely not last as long as brushless/ ball bearings? I don't know in your application. Weigh the cost against machining & time. At 18,000 rpm, it needs to be good. You're saving $10 on motor, and $20-30 on ESC?

There are people using brushless hobby motors for other things, like milling/routing. You may want to research a few forums and see how they hold up: Can RC Brushless Motors be used as Spindle Motor ???

And what the hell, if it doesn't work for the A/C, duct it into the intake and market next generation E-Ram! eRAM electric supercharger ( a brief description) & some responses to the many post

[dad911]

Used RS550 & RS775 from these guys: Motors - banebots.com

Also realize that if your motor has a free-speed of 18,000 rpm, you won't get that when loaded by fan.

Typically design for 1/2 freespeed RPM, gives reasonable current draw and power.

[Discseven]

^^^ Am digesting all input... TY!

Am turning away from brushed. Clearly brushless has advantages. But thanks for link to Banebots---I see the 550 has high RPM. 1/2 freespeed note... nice!

IF going with an ESC controlled motor, with a "servo tester" (SR) the motor is either ON or OFF as I understand it. Is it necessary to attend the SR or can that be set once and tucked away with the ESC?

Did look at the electric supercharger (below) but didn't get into because of it being throttle controlled---like and ESC. That unit now returns as a possibility.

[SCadaddle]

The "duty cycle of the fan" has a lot more to do with the life cycle of the brushless motor than the fan and housing itself. By far, all of the model aviation ducted fans are considered "tractor" fans and not "pusher" fans. They take air in at the front of the fan and discharge air through the housing. Now in a model, you want to keep the ESC cool and thus require adequate airflow to it. But you don't put it in the fan housing downstream of the fan.

Brushed motors are ancient technology to Brushless motors. The problem with trying to take the ESC out of the equation with a brushless motor is that the ESC controls the current "pulses" that the motor requires to actually run. You can actually modify the timing of the motor via the ESC.

At some point, after realizing this EDF technology has been around for many many years now, you have to ask yourself "why hasn't anyone else already done this?"

[Discseven]

^^^ SC... thanks for input, particularly on cooling the ESC. NOt sure how am going to do that if it cannot be in the air stream.

Am buying into EDF program. There are 2 main considerations yet to answer. First is whether EDF will hold up operating in "moist" conditions. This refers to car being driven in rain. The EDF would be located in duct at least 2' from actual intake and there will be a 45 degree bend before it. (Using 4" smooth bore duct, picture the intake located ahead of left rear wheel near the torsion bar. Duct runs up at around 45 degrees then turns with ducting continuing above the wheel. Duct then turns down 45 degrees after rear wheel and enters air bucket connected to condenser. The EDF will be somewhere along the ducted path.)

If an EDF can hold up under "moist" conditions, next question is noise---can the system be insulated adequately? In regard to noise, it seems the more blades on a fan the quieter it is. 100 mm EDF fits the 4" duct nicely.

[Discseven]

Originally Posted by dad911

Radio receiver will be replaced with servo tester (ST). I believe ST will need power. Will it take 12v from car?