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**SGD** · 11-03-2013, 11:13 PM

Is it a Zagi type model and I take it you want to stick a prop on the motor and not the whole DF unit on the model?
I've used these in DF models before and if you look at the spec they recommend them for a pylon / 70mm EDF jets up to 1300g with a APC E 4.7 X 4.7 prop the pylon model

[URL="http://www.giantshark.co.uk/typhoon-edf2w20-p-405097.html"]Typhoon EDF-2W-20[/URL]

Or this for a bit more get up and go

[URL="http://www.giantshark.co.uk/typhoon-motor-2w25-p-405100.html"]Typhoon EDF Motor 2W-25[/URL]

To pick a motor you would really need to know what all up weight the finished model is likely to come out at and work back from there.
Hopefully, this will get you going in the right direction

**Ruston** · 12-03-2013, 07:09 AM

Ducted Fan Motor, question

I have this motor in a hotliner and it is amazing for the size. At 2200 kV it is very fast. A 6x3 APC prop on 3s gives around 1kg of thrust at 500watts, more if you can go to 4s. It would work well on a 1200mm wing.

[url]http://www.hobbyking.com/hobbyking/store/__21481__NTM_Prop_Drive_28_36_2200KV_696W.html[/url]

**waveydavey** · 12-03-2013, 07:23 AM

I'm going a little more out there, 6S and the all up weight is around 2Kg so based on that was looking at around 800Watts. This is what I was thinking

[url=http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=29357]Dr Mad Thrust 1200kv 3700watt 90mm EDF Inrunner 6-8s version (40mm)[/url]

**Red3** · 12-03-2013, 07:48 AM

hi dave me and ian c expermented with this some years back i never did locate a better motor than the j perkins enrg 4000kv and 4in prop for out and out speed it was an animal i would say it was well over the 100m.p.h but would suck a 2200mah 3s dry in about 3mins.
the problem with the ducted fan motors is they get far to hot when running a small prop.

**SGD** · 12-03-2013, 07:52 AM

There's a small program called MotorCalc that's designed to help you select a power train, motor, esc, battery and prop, by inputting a pile of data about your model. Take a look at the tutorial page here:

[url=http://www.motocalc.com/tutorial/index.html]MotoCalc Tutorial - Model Aircraft Power System Selection Using Your Computer[/url]

One basic guide to start with is the power to weight ratio and this is from the above page:

Regardless of the motor, battery, and propeller eventually chosen, any aeroplane needs a certain amount of power to achieve a desired level of performance. One simply cannot get around the laws of physics. Because of this basic fact, a number of "rules of thumb" have been proposed based on a plane's power to weight ratio. For example, it is suggested that a plane have about 40 to 60 Watts of power per pound (88 to 132 W/kg) of aircraft for typical "sport" type flying. More aggressive aerobatic flying requires about 70 to 100 Watts per pound (154 to 220 W/kg).

The EDF boys look at 300W/kg.

**waveydavey** · 12-03-2013, 07:54 AM

Prop size I'm thinking of 6 or 7x5 to 6. The heat was the thing I was worried about although at that sort of speed theres going to a bit of self generated wind :D

I'm not really bothered about the flight time as it is only for speed and I can always leave the left stick alone. I can't find much info about the heat build up at all but realise that a motor sitting in a tube with half a dozen blades pulling the air over it help with the cooling. So difficult to find something with the go you want able to handle 6S at a reasonable price

**Ruston** · 12-03-2013, 09:03 AM

Ducted Fan Motor, question

This is the link to the online version of motocalc, you can see what sort of thrust and speed your proposed setup will deliver, it also indicates case temperatures so you'll see if you are likely to have a heat problem [url]http://www.ecalc.ch/motorcalc_e.asp?castle[/url]

**coolice** · 12-03-2013, 09:15 AM

Hi Dave.

As SGD has suggested for ultimate speed you want a small prop going really fast, as it will cut through the air better. I don't truly know the science behind it but a ducted fan setup by comparison will not work as well, I think its something to do with the in flow and out flow of air through the unit making it less efficient past a certain speed.
The small prop going fast is from the pylon racing boys and they know about going fast.

There was a good motor for the wings, even better than the Perkins ones, Baz has one I think and I can't remember their name at present. Back in the day I looked at one for my wing, but at £100+ you had to be dedicated. I know they were very powerful on 6s, custom wound stuff. Of I remember their name I'll be back.
.

**SGD** · 12-03-2013, 09:20 AM

[QUOTE=Ruston;990326]This is the link to the online version of motocalc, you can see what sort of thrust and speed your proposed setup will deliver, it also indicates case temperatures so you'll see if you are likely to have a heat problem [URL="http://www.ecalc.ch/motorcalc_e.asp?castle"]eCalc: propCalc - Propeller eMotor Calculator** (c) by Markus Mller[/URL][/QUOTE]

Thanks for the link, very useful :encouragement:

**coolice** · 12-03-2013, 09:28 AM

Mega motors, various ones here; [url=http://www.effluxrc.com/MEGAmotor_c8.htm]MEGAmotor[/url]

These are known to be..... well...... quick!
.

**waveydavey** · 12-03-2013, 10:13 AM

Hi Ian it's not ducted fan as such, I'm thinking of using only the motor from a 90 size ducted fan with a pusher of say 6x5 6x6 maybe a touch bigger. It's the motors just seem a little more powerful and better rated for 6S

**coolice** · 12-03-2013, 10:34 AM

[QUOTE=waveydavey;990350]Hi Ian it's not ducted fan as such, I'm thinking of using only the motor from a 90 size ducted fan with a pusher of say 6x5 6x6 maybe a touch bigger. It's the motors just seem a little more powerful and better rated for 6S[/QUOTE]

Ah, I see your logic mate as most EDF models use 5/6s+.
I'd just suggest choosing which motor you go with carefully, reason being in my pursuit of out-running IanH I choose a ducted fan motor which proved to be the wrong decision.
It turns out that some motors which work well in a ducted fan installation, do not then work as well when mated to a prop. The Mega's seem to be able to do either setup quite well, but in my case the high Kv ducted motor I chose just didn't have the torque to spin a prop. A small ducted impellor needs less torque to spin up than a larger pitchy prop.

NEU motors are also showing to be good, in my Google for the memory jog about Mega's, I saw reference to 150mph+ NEU powered wings :hurray:
.

**miniman** · 12-03-2013, 10:46 AM

We have a small Pylon racer called a VIP, this was originaly designed for a brushed 400. The fus can only take a 3s 1600 pack, ad so to get more speed the onlyb way was a ducted fan very high Kv motor.

We switched out the 400 for a 4000 Kv motor driving a 2.5" x 5" hand made prop. The prop was originally a 5" x 5" prop, ad it was reduced to keep the Amperage down to a maxium of 20 amps, giving a measured 43,500. We estimated by timing this over a 100mtr patch at over 120mph.

DAve if you want to see it, I can bring it down to the club for you to look at.

Peter

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Ducted Fan Motor, question

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