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Old Dec 03, 2012, 06:14 AM
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Australia, VIC, Melbourne
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I have a few open motors... so I will have to dig out the magnifying glass!! LOL
They must be small clips!
Do they have the 'eyelets' that C-clips normally have? They would be WEENY then! hehe
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Old Dec 03, 2012, 10:42 AM
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The43rdHammer's Avatar
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Joined May 2010
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Can I ask the class a question (not bearing related sadly).

I recently installed a Changesun 10 blade fan into my FMS F-4 Phantom and having read through some of these posts it would seem like the lip makes a big difference to the fan's performance.

In the F-4, the air intakes funnel down to roughly the same diameter as the fan housing, therefore I can't fit the lip to the front of it. I'm assuming that in this instance having, or not having, the lip installed is going to make very little difference?

Also, I'm using a 2,660kv HET 2W-25 on 5S to drive the fan and although the combination produces a lot more thrust, I don't get the whoosh ?

I also have a HET 6904 5 blade fan and am thinking that if I'm not getting the desired noise it may be more efficient to switch the CS10 to the 6904?

Any help much appreciated.

Andy
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Old Dec 03, 2012, 10:53 AM
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United States, AZ, Gilbert
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Quote:
Originally Posted by PAPE View Post
No peter. The bearings have a "c" clip. And yes they can be opened you just don't know how to do it. The metal face (seal) is removable. Both sides are removable on rc bearing. I have been opening bearings on rc use for over 15 years. I know what am talking about. If more questions come from this I will open one up and takes pics.
I would love to see some pics showing how to do this. I'm not doubting what you're saying PAPE, I would just like to learn more about it as I have never done anything like this and it seems like a useful thing to understand. Thanks!
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Old Dec 03, 2012, 11:06 AM
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Quote:
Originally Posted by The43rdHammer View Post
I recently installed a Changesun 10 blade fan into my FMS F-4 Phantom and having read through some of these posts it would seem like the lip makes a big difference to the fan's performance.

In the F-4, the air intakes funnel down to roughly the same diameter as the fan housing, therefore I can't fit the lip to the front of it. I'm assuming that in this instance having, or not having, the lip installed is going to make very little difference?

Andy
Correct.


Iin fact, if I may use this occasion to unfold my soap box for just a minute....

This whole thing about the lip has, IMHO, often been completely misconstrued, blown out of proportion, and led to huge urban legend and some wild ideas.

It's very simple: When tested IN FREE AIR, and AS A UNIT, then EDF efficiency is, and was long ago proven, to be much affected by the presence, size, and shape of a 'lip' to guide the air into the tunnel section of the fan unit.

Nothing really shocking or unusual, and conforms to both standard aerodynamic theory, and common sense.

Now, let us move to the case of a EDF unit embedded into the tunnel of a common EDF plane. The case of air entry, versus static surrounding air follows the exact same principles as before, and the same rules apply. However, the physical model has just become nearly impossible to model, because these little foamies typically have serpentine tracks, non-circular air inlets (and multiple and/or bifurcated inlets!), cheater holes, complex curves, sharp edges, etc, all for the sake of scale appearances.

The key thing to remember though, is that those entry points for the air into the intake have collectively become the proxy for the idealized lip!

THERE IS NO ADVANTAGE TO DISTURBING THE EDGE OF AN EDF BARREL BY PUTTING A LIP ON IT, IN AN OTHERWISE SMOOTH AND MATCHING FUSELAGE AIRWAY!!!!!

The EDF housing is merely an extension (at best) of the duct work, and smooth uninterrupted, and contiguous, is better.
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Old Dec 03, 2012, 12:11 PM
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Thanks, thought so.

Any thoughts on 6904 vs. CS10?

Andy
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Old Dec 04, 2012, 05:42 PM
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No "thoughts" yet?? LOL

Lower blade count fans are more efficient. So you will get more thrust for your Watts.
Not tons, but enough to make a difference in flight times.
But then you don't get the great "CS10" sound..... sort of.

The real source of 'great jet-like sound' is a fan actually being QUIETER. Which then allows you top hear the airflow generated noises far better. The White Noise of the airflow system.
A low blade count fan sounds like a leaf blower and drowns all of that sound out.... but a well balanced and very high RPM lower blade count can at least be 'better'.

So if you want optimal jet-like sound, use the CS10 or CS12 (70mm).
If you want optimal power/flight-time, use a low blade count fan. eg that HET 6904

Personally I won't touch anything under the CS10 !! Because the sound result moves your models to far nearer 'real jets' than 'garden leaf blowers'!!! I do hate the loss it costs, but just have to accept that.
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Old Dec 04, 2012, 05:58 PM
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Hello,
I made some tests with a HET 2w23 motor on 5S to find the most efficient rotor for this motor on 18,5v (21v full). As I went to the limits of my wattmeter (100A), I'm not really sure about the results but I found that the HET6904 rotor (mine is 4 blades, not 5 as you said) and the CS10 have approx the same "effect" on 5S with this motor (99,9A, around 1900W!) and the trust is nearly the same too (only 100-150 grams less for the CS10). As this motor is specified for 1100w max (peak), I won't use it with this fan but I think your 2w25 could be a winner for it in 5S, due to the 150 kv less and normally more power compared to my 2w23. Concerning the "whoosh" sound, as the F4 has a bifurcated outlet you should normally have the sound....(noise is normally increased in the case of turbulent velocity). Did you try it in 6s to see if it changes something?
Just a funny story for me today to tell you guys before leaving, I tried my 2w23 with the CS 4 blades rotor (70mm), and during the second test I had a very bad surprise......the rotor dissapeared (no I'm not Coperfield ) . I was very satisfied with the results (approx 1300w, 55A and 1,26kg of thrust) but when I made a second run to be sure of my results, I ear a big noise and then nothing else except the motor only.....so I immediately stopped and search..... I was looking for the rotor everywhere in my garage, and suddenly I don't know why I had a look on the ceiling....I found it picked deep in the styrofoam!
Hopefully I had no injury, but imagine if it went in my head, even with the googles I think it hurts!
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Old Dec 04, 2012, 06:17 PM
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Have to dis-agree with you a little, Peter. High speed props are more efficient with fewer blades. The most efficient racing prop is a single blade. But..at slow speeds, a higher blade prop is more efficient. My experience comes from racing boats in my younger yrs, and now with the American Bass boat. A 5 blade SS prop will hole shot a 3 blade SS prop everytime, with the same boat and motor same diam prop. But the top end is where the 3 blade comes alive. But of course pitch is usually higher on less blade counts.

So the HET 6904 will be more efficient at high speeds as compared to a higher blade count. But I'm willing to bet, that at lower watt numbers, the CS10 will produce higher static thrust than the Minifan or the 6904.

I changed my Lander Cougar from the minifan to the CS10. Both consumed 650W, the CS 10 flys it with better accelleration. And it verticals much better with the CS10. But, if I was after top end speed, I would not hesitate to put the minifan back in or the 6904 and run 2000W.

But what fun is watching a scale jet fly in a non-scale manor?

Fuzz
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Old Dec 04, 2012, 07:12 PM
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Originally Posted by St. Martin View Post
But what fun is watching a scale jet fly in a non-scale manor?

I see what you did there!

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Old Dec 04, 2012, 07:38 PM
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You said you changed a minifan to a cs10, but not what motor used in each. (or kv). So those results mean nothing without knowing that.

Also, the 'more blades, higher/lower speeds' etc also don't tell much because what is a 'higher speed'? A CS10 at 1200w might be a 'low' speed for its design. (not that it will be). So any given situation, application, of a design is not directly linked to another. eg plane prop, boat prop, or even proper within the same use (due to different designs aimed for different speed/purposes).
Plus the most typical use of CS10 is 800W to 1100W range.... and it is less efficient than lower blade counts for that. That is all that really matters.

Their design does seem to produce a result that is more 'torque' focussed than 'speed'. And if you try to direct them to speed, via exhaust ratio, you lose efficiency. But that is also fine, because as you alluded to, most models go way too fast anyway, so the CS10 is perfectly suited to producing more scale/realistic flight behaviours.
If you want FAST.... go to Wemo.
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Old Dec 04, 2012, 08:09 PM
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Aboslutley.
These rotors max out at about 1300w (or about 46K rpms)
There OK if ya wanna putt around and dream about turbines.
If you want your jet to perform like one (up to 2500W), The HET6904, and Wemotec minifan pro have long been the powerhouse 70mm EDFs (and still are) for a reasonable cost.
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Old Dec 04, 2012, 08:54 PM
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LOL... well I wouldn't call it "putt around".
Rather CS10 "go adequately fast", Wemo/HET "Go screaming fast"
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Old Dec 04, 2012, 09:32 PM
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Quote:
Originally Posted by efflux RC View Post
Aboslutley.
These rotors max out at about 1300w (or about 46K rpms)
There OK if ya wanna putt around and dream about turbines.
If you want your jet to perform like one (up to 2500W), The HET6904, and Wemotec minifan pro have long been the powerhouse 70mm EDFs (and still are) for a reasonable cost.
not exactly sure what you are trying to say but ours on 6s 2150kv runs around 43k and 1600watts and it is very adequate and fast. we have done many PK Habu's with this and are fast........see our habu vids.......nicks projet A10 has two of them on it at 3kw+ and has rediculous vertical and speed.

I would love to hear what motor your using that gives you 46k at 1300watts, maybe you are not saying that but it certainly will take more than 1300watts......46k was our max I agree but then they have been playing with the blend of plastic so who knows on the more recent batches

not exactly putting around lol!!!
78Amps, 1800 Watts, 42,000 rpms
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times two on a single 6s 5ah 65c batt
Nicks A10 (7 min 48 sec)
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Old Dec 04, 2012, 11:40 PM
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Australia
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Lots of talk, but where are the videos bar jcfrd's??

F16 running at 850 odd watts with CS10 and a restricted 56mm exhaust, its pretty slow so you may not want to bother watching the video

Extreme RC F-16 with 10 blades Changesun rotor (2 min 22 sec)
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Old Dec 04, 2012, 11:53 PM
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Well that is a 'weeny' plane. And F-16's (like that design) would be the fastest 'shape' you can use. So put those two factors together and it will be FAST on any power system.
But none of the videos mean much without recorded speeds (truly accurate) seeing videos make any plane look 1.5x faster than when you are there anyway. My 900W Vampire flies as fast as that!! LOL. In video... (well, not really.. but it looks FAST in video!)

And for whatever power they are using, a Wemo would do that bit more thrust/speed for that same power. Typically 1000W in a CS10 will be 0.2Kg sort of area lower than the same in a low blade count Lander or Wemo. That is more what counts in the comparisons mentioned.
The CS10 costs power... some amount.

Plus I think Efflux said more that the CS10 runs out of power (1800w area? Kaboom), when the Wemo is still going over 2000W, to even 2400W.... alive.

Now the CS12-70.... that solves that power limit problem, but (same as the CS10) it will still not give the same result as the Wemo for the same power input.
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