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Old Dec 06, 2012, 05:01 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
20,639 Posts
i dont pay much attention to Watts .....cause yeah are you turning the rotor or making waste heat??? is there a way to tell how many watts are actually turning the rotor?...but we need to give it to Mark those are great Amps/Thrust numbers,now lets see a vid of it flying ,that would be cool
on another note: Billy i shipped your other Nacelle ,i think that is about 85 or 90 of those things i've made.when fans and falcons are selling i get busy i really need another Falcon ,i just dont have the time right now.
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Old Dec 06, 2012, 05:24 PM
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San Diego
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Quote:
Originally Posted by Extreme_RC View Post
This is a Dynamax 127mm (5") fan unit? 5300w to get 7.3kg thrust doesnt sound all that efficient, I see 7.7kg at 4800w with the Ramtec setup. I will roll up a thrust tube 100mm diameter (80% FSA) and test it to see what sort of amp increase we get.

As for your thrust tube, you sure on the size? 3 & 3/8 inch is about 86mm, that seems extremely small, 80% FSA for a fan with 125mm rotor and a 57mm hub is 100mm.
First of all this fan is quite a bit lighter than yours so you have to factor that into the equation, and the fact that you think 3 3/8 is to small for a Dynamax tells me you donít know much about the Dynamax cause that is a very commonly used diameter....That diameter is tested based on minimal amp increase compared to productive efflux increase with minimal static loss!

You keep pushing, so this is my take: Ramtec fans were great on Glow because none of them had low end thrust they all took along time to get on step, once on step the high blade pitch allowed for higher top speed! The Ramtec does not have the low end thrust that I want to see in my aircraft. I have seen two of the same airframes one with a Dynamax and one with a Ramtec, the Ramtec setup had more thrust and a Less AUW of the aircraft than the Dynamax jet, The Ramtec powered jet had a better top end but lumbered to get off the ground despite being the same airframe, weighing less and having more thrust. Both aircraft had the appropriate thrust tube diameters. The Dynamax powered jet had much better take off and vertical performance and had immediate power to get out of trouble, both flew good.

I know you donít care and your going to go on about how efficient yours is, well different strokes for different folks.... Lets get back to talking about Falcon 120's.
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Old Dec 06, 2012, 06:03 PM
Extreme CNC Alloy EDF
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Australia
Joined Mar 2006
11,494 Posts
I am not pushing anything, simply asking questions and trying to understand another viewpoint. No I dont have a lot of experience with dynamax, unfortunately in Australia it was never that common, and getting hubs for Dynamax to use with electric is not easy.

What is the weight of the fan ready to run? You want to help or you want to simply antagonise with your replies?? Because so far I am feeling antagonism rather than someone who actually wants to outline their experiences, saying your fan is "quite a lot lighter" really doesnt tell any of us a thing.

End of the day I dont make the ramtec, nor the dynamax, I simply want to use the rotor/s and am more interested in an optimum setup, no interest in smack talk or dishing on one or the other.
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Old Dec 06, 2012, 06:26 PM
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San Diego
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Im not antagonising, I am at work and I can weigh it when I go home but I know it is lighter, its one of the lightest 128mm fans out there. I am just clarifing my and a couple others experiences that were dissapointing with that fan. Not that it cant be worked out and maybe you did it.
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Old Dec 06, 2012, 07:41 PM
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Arngeir Blakseth's Avatar
Molde, Norway
Joined Jan 2001
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The Dynamax does indeed work with a smaller thrust tube outlet diameter than the Ramtec, I would use 95-100mm on the Ramtec while the Dynamax will be fine at 86mm, even though that is on the small side optimized for speed so a little bit of thrust is lost. I run a 90mm exit in my MiG-15 which has a XPS Dynamax unit, and it works well.
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Old Dec 06, 2012, 09:34 PM
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Exactly 2 lbs ready to go.
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Old Dec 06, 2012, 09:35 PM
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San Diego
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Quote:
Originally Posted by Arngeir Blakseth View Post
The Dynamax does indeed work with a smaller thrust tube outlet diameter than the Ramtec, I would use 95-100mm on the Ramtec while the Dynamax will be fine at 86mm, even though that is on the small side optimized for speed so a little bit of thrust is lost. I run a 90mm exit in my MiG-15 which has a XPS Dynamax unit, and it works well.
At that diameter it was no short on thrust and it gave me a bit more top speed that I was looking for.
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Old Dec 06, 2012, 11:42 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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the Stus and Shubies need a larger dia too,when i install those in my nacelle i have to cut off some at the rear and install a ply wood former to get the 4" exit dia.
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Old Dec 07, 2012, 06:52 AM
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Originally Posted by bri6672 View Post
Exactly 2 lbs ready to go.
Impressive.

Terry
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Old Dec 08, 2012, 12:15 PM
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Joined Nov 2012
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ESC position

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Originally Posted by stumax View Post
If you wanna talk powerhouse fans, here's something I've been working on all year, the SM120-63. 120mm rotor dia, 63mm hub dia, which means it only has 8192sqmm FSA, yet it puts out close to what a 127mm fan with around 10,200sqmm FSA does at the same power. It's the same rotor as on Joe's 120-56 (which gives about 7.4kg thrust on 4500W, 8.8kg on 6kW) , but with a larger dia motor tube.

It's got a few very special things about it which set it apart from anything else out there. Most noticeable is the motor tube design. Notice it has a bearing housing at the front, supported by 6 legs. The motor is a custom made 6 pole motor which uses 6 screws to screw it into the motor tube, there's no front bearing cap on the motor, the bearing is in the front of the motor tube. This gives the setup immense rigidity and allows for huge cooling holes in the front to pass air thru the motor. It has the benefits of having the motor built into the motor tube without the disadvantage of not being able to change it if it melts or you wish to try another kV or length. Like all my other fans, the motor case is a precision fit inside the motor tube and uses thermal grease to help thermal conductivity. This one uses 9 stators, which gives the shroud a lot of extra rigidity.

Performance is right up there, 6kW gives 8.6kg (almost 19lb) thrust, 4.5kW gives about 7kg (15.5lb) thrust. Comparing these numbers to a 127mm Dynamax or Ramtec fan, don't forget it has about 80% the FSA of a 127mm fan, and so its static thrust should be about 90% (ie square root of 0.8) of their values at the same power. As it only has 8192sqmm FSA it can handle smaller inlets and smaller exhausts. The motor in this one can handle 8kW or so (possibly more, I need a better esc to go up there), which will net about 10kg (22lb) thrust, with about 250mph exhaust velocity at 100% FSA. AUW with this motor is 1120g. There's a shorter motor option which is about 200g lighter and can go up to about 6kW, but for those power levels the 120-56 is a better choice (even lighter), the HET800 series 680kV motor works very well on 12S, same as the Neu 1915-1Y in Joe's one.

I'm planning to make it available before Christmas if I can get my component suppliers to play ball, price should be around the $450-480 mark + motor, depending on my actual manufacturing cost.

Stu.
Very nice unit Stu. I wonder if the ESC can be placed inside that rear carbon airfoil for better cooling? It seems that there is enough place behind that big motor housing. However if the ESC is behind the motor with very short wires then I have to ask if the LiPo batteries should be placed around the edf unit (BNM EVF style) ? Also what would be the price of your custom motor ?
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Old Dec 11, 2012, 03:31 AM
The blade numbers go up to 11
stumax's Avatar
Sydney, Australia
Joined Aug 2002
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Quote:
Originally Posted by BeeStinger View Post
Very nice unit Stu. I wonder if the ESC can be placed inside that rear carbon airfoil for better cooling? It seems that there is enough place behind that big motor housing. However if the ESC is behind the motor with very short wires then I have to ask if the LiPo batteries should be placed around the edf unit (BNM EVF style) ? Also what would be the price of your custom motor ?
Thanks! Actually, I reckon the worst place for the esc is behind the motor for 2 reasons:

1. the motor is hot, putting the two hottest items in the aircraft right next to each other (without any heat shielding in between) is not such a smart thing to do.
2. Usually the lipos are ahead of the fan, which means the wires from the esc to the lipos become a lot longer than they should be. Long batt leads = high inductive spikes = hot capacitors = short capacitors life = short esc life (sometimes very short!), unless you put a bunch of low ESR caps across the batt leads at the esc.

I did some temperature testing with an SM110-45/ Neu 1527-1.5Y/12S 5000's a while back. The air exiting the end of the tailcone was 15-20degC warmer than ambient. This tells me that there is a decent amount of heat removed by airflow thru the motor. Imagine a hot summer's day when it's 35-40degC (typical summer here in Australia), the air exiting the tailcone will be 55-60degC. Put the esc in this warm air and it's not going to cool very effectively, and it's likely to restrict the airflow thru the motor, making the motor run hot. My preferred way is to mount the esc half way between the battery and the fan, and use a small 5V CPU type fan mounted on the esc to keep it cool. These little fans draw a few mA and so you can power them directly from the Rx batt without worrying about flattening it. The only way I'd mount the esc in the tailcone would be if you block the back of the motor tube and provide air exit scoops to draw the motor cooling air out, then have a hole in the wire fairing part of the tailcone to force cool air into the esc. Cooling efficiently is tricky stuff, you have to guide air and make it go where you need it to, not just let it find its way. A good look at how the control line team race guys (F2C) cool their engines will tell you how important it is to get it right.

The custom motor will be in the order of $150-170. Right now I'm super busy getting dealer orders out for 80's and 90's, as well as get some new 110-47's built for guys who've ordered the new Jet Teng xXx. The new 120-63 will need to wait until early Jan before it's ready for full production.

Stu.
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Old Dec 16, 2012, 11:19 AM
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Thanks Stu for the valuable information.
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Old Dec 16, 2012, 03:57 PM
Extreme CNC Alloy EDF
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Australia
Joined Mar 2006
11,494 Posts
I been fitting the ESC in front of the fan for years, either inside the ducting buried into the walls if foam, or with heatsink side protruding through a cutout if in glass. I always recommend this to customers as the reasons are obvious, wiring length balance, temps, and increased risk of joint and component fatigue over time especially if placed in the duct without the protection of a cone. Main one is wiring balance though, you can save a good 20-30cm of batt wiring which helps your ESC caps greatly.
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Old Dec 17, 2012, 11:06 AM
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Quote:
Originally Posted by Extreme_RC View Post
I been fitting the ESC in front of the fan for years, either inside the ducting buried into the walls if foam, or with heatsink side protruding through a cutout if in glass. I always recommend this to customers as the reasons are obvious, wiring length balance, temps, and increased risk of joint and component fatigue over time especially if placed in the duct without the protection of a cone. Main one is wiring balance though, you can save a good 20-30cm of batt wiring which helps your ESC caps greatly.
Is it better, when you have to cover a distance, to have the long wires between the Motor end the ESC ?
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Old Dec 17, 2012, 12:56 PM
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USA, TX, The Colony
Joined Dec 2005
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Quote:
Originally Posted by BeeStinger View Post
Is it better, when you have to cover a distance, to have the long wires between the Motor end the ESC ?
Yes
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