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Dec 21, 2012, 08:38 AM
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performance restrictions on Change Sun 10/12 bladers


Quote:
Originally Posted by v8truckin
Well it would be nice if they did do CR fans on the CS10/12.

Ya my power loss was about 25% on the SU35 w/ CS10 in FW shroud, makes sense now.
well that's probably only part of the story - the CS is working fine in an environmetn with rather open (i.e., not restricted below 60mm or so) exhaust, and a plentiful supply of air via good intake ducting. So even a CS in a CS shroud might not provide as much thrust as a 5-blader... In the best of circumstances the CS is only slightly less efficient than the low-blade count fans, but it can be a lot worse. Don't know the inlet ducting and exhaust diameter on the SU-35.

In nacelles the CS usually does very well for the obvious reasons - as can be seen in the Dynam 262. The Freewing has more scale, i.e., smaller inlets and exhausts.
It remains to be seen if the cheaters provide enough air for the CS to be happy. The exhausts will be easys to determine (and sand a bit to 60mm, in case they are smaller :-)
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Dec 21, 2012, 09:30 AM
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Maxthrottle's Avatar
Getting confused here; are you guys talking about loss putting two ccw CS or any other for that matter, in the FW duct, or loss placing a ccw fan rotor in a cw FW EDF housing? A cw housing will see greater loss because the stators are pointing in the wrong direction.
Or are we talking how the CS need 90-95% FSA unless used fo high speed? Cause if comments were in reference to the cheats, the don't add swirl direction to the duct.

I'm not sure if everyone is talking about the same thing.
If you go CS and the duct is lower than 60mm you may want to open up the tail some.
Dec 21, 2012, 10:32 AM
Should've, Would've, Could've
v8truckin's Avatar
Thread OP
I'm talking about putting the CS10 fans into a FW counter rotating shroud, which I did on the Su 35. Wasn't thinking about the stator direction and would explain the loss in thrust on static. Hoping better thrust on the nacelles of the me262.
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Dec 21, 2012, 11:18 AM
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genghiskt's Avatar
V8,

Can I check with you on SU35, are the fans rotating inward ? Viewing from the nose of the plane.

Thanks.
Dec 21, 2012, 11:36 AM
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v8truckin's Avatar
Thread OP
honestly I do not remember, but I know they do have more thrust if they rotate in a certain direction vs. the other (inward or outward). Wonder if the cheaters also played a role. This all can come in play for the Me262 setup as it is using CR fans and cheaters like the SU35.
Last edited by v8truckin; Dec 21, 2012 at 02:29 PM.
Dec 21, 2012, 01:50 PM
Registered User

One CAN buy Freewing shrouds...


...so there is a solution (if you want to use other rotors which do not come in counter rotating variants), actually there are several, and maybe someone might point to the cheapest (just buy the Freewing shroud). I had thought that HK would sell the 70mm Freewing fan, but they're only selling the 64mm variant.
But at RC Castle you can get:

The Freewing 70mm fan (normal rotation), but only complete with rotor etc., and therefore not soo cheap
http://rc-castle.com/shop/product_in...roducts_id=501

Therefore, if you want to have a drop-in solution and need a 10-blade rotor anyway, you might buy one of those. Beware, the rotor is NOT identical to the Change Sun product, rather it seems to be the variant Lander / Cyclone power is using in alloy variants. There were rumors that the rotor would be inferior to the Change Sun (unbalanced etc.) but I don't know if that is true, but anyway I wouldn't mix a CS rotor with a Cyclone Power rotor on one plane...
http://rc-castle.com/shop/product_in...oducts_id=2880

cheers
Clemens
Dec 21, 2012, 02:20 PM
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Maxthrottle's Avatar
Its either rotating inward at the top or its in wards at the bottom. The vortex from under a foiled surface or body is bottom center outward unless changed by a strake. So you'd perceivably want the starboard side rotating ccw facing the fan, and on the port, cw facing the fan to rotate against the direction of the vortex flow. But that rotation is only noted once released from the body. I.e. it is linearly moving from center into the underside cheats into the duct linearly and only comes into play if the cheats are less that 70mm from the fan face. I.e. is the cheat sitting less than 70mm from the fan face?

If the cheat is lower offset it may create a rotational moment but it looked to be just in line to center from 8 and 4 O'Clock making it just straight air going into the duct.

I thought we didn't find a difference with the SU? Two ccw's performed as well if not better than the counter rotating fan indicating the cheat placement having no notable influence.
If that cheat was on the belly as it has been on twin EDFs for years how is it there has been no notice of one side developing less thrust? And if the tube is round moving the cheat at any angle shouldn't influence the direction of fluid rotation. Only maybe if it were linear off center, vanes vertical to center placed at the bottom perpendicular to the circle.

OK this sounds a bit interesting if there is an influence............

In fact looking at the picture the cheat doesn't appear lower offset to influence fluid mass rotation and it sits away and ahead of vortex influence. It just appears parallel to duct center.


Quote:
Originally Posted by genghiskt
V8,

Can I check with you on SU35, are the fans rotating inward ? Viewing from the nose of the plane.

Thanks.
Quote:
Originally Posted by v8truckin
honestly I do not remember, but I know they do have more thrust if they rotate in a certain direction dogs the other (inward or outward). Wonder if the cheaters also played a role. This all can come in play for the Me262 setup as it is using CR fans and cheaters like the SU35.
Last edited by Maxthrottle; Dec 21, 2012 at 02:36 PM.
Dec 21, 2012, 02:33 PM
Registered User

does it play a role if the cheater is left or right?


NO

the fan rotates - 360 each rotation :-)

now if the cheater was on the bottom, would that have made you thinking if there was a difference between left- or right rotation? the fan blades go round and round, either clockwise or counter-clockwise and don't know where is up, down or sideways. And the air is getting sucked into the cheaters.
So for the rotor it doesn't make a difference. And I would also not think that it would make a difference for the manner the air is sucked in, i.e., the low pressure on the surface of the nacelle.
(for the flying, there IS of course a difference since there is air sucked in at the cheater, and if the cheater is on the bottom you get sucked down which leads sometimes to ballooning as soon as you go OFF the throttle)

The only problem when using different rotors which do NOT come in both rotation variants is that you will have to swap out the shroud which has the Freewing stock rotor turning left, i.e. counter-clockwise (when looking into the direction of flight), because the vanes (which are there to get the swirl out of the accelerated air) will be tilted in a direction which would only make the swirl of a fan rotating normally (clockwise) worse.
And that is why I tried to find shops selling Freewing shrouds, so far I know only of RC Castle and they would either sell you the whole Freewing fan, or a Cyclone Power fan sporting the Freewing shroud and a 10-blade CS lookalike.

Anyone knows where to cheaply buy Freewing shrouds (normal rotation)?

clear enough?

Of course, NOT having counter-clockwise rotating fans means that we have two torques which are not balanced. Well, the Dynam also flies with two identical fans, so there won't be a problem
Dec 21, 2012, 02:40 PM
Should've, Would've, Could've
v8truckin's Avatar
Thread OP
Max,

Yes on the Su35 cheaters didn't play a factor on thrust on CR fans vs CCW fans turning in the same direction (non CR fans). Just wondering if they do play a factor on the direction that CR fans spin inward vs outward, since there was 25% loss of thrust on my SU when I flip flopped the direction. However the CS10/12 setup is starting to look interesting again to me for the ME262 and my ditch the CR fans for them.

G,

Thanks ya I may have to look into those cyclone or Lander shroud as I don't want to hack up the nacelles. I di have some spare LX shrouds lying around from a ditched build, although they may be too flimsy. I've got time to think about my setups though and any input is welcome.
Latest blog entry: Freewing Me262
Dec 21, 2012, 02:46 PM
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Maxthrottle's Avatar
two rotating in sync don't have enough moment to create side slip but on their own counter their individual rotational moments.

So ya Either or.... Is it a problem to hog out foam for the CS units? why the search for ccw EDF shrouds? The CS housings are slightly longer with longer stators to better smooth noise/turbulence. I understood those going to shorter housing changed the note or tune of the CS sound.

Fascinating. Will wait and see.

Just saw your note V8.... I can't see that they would matter. As Mopetista said the fan rotates 360 so it doesn't care that its getting more air from the 360 orbit. If the entrance was lower which it slightly was with the SU it may have created a very slight moment by having the cheats below center but it appears the ME shouldn't suffer this.
Dec 21, 2012, 06:36 PM
Should've, Would've, Could've
v8truckin's Avatar
Thread OP
Quote:
Originally Posted by Maxthrottle
So ya Either or.... Is it a problem to hog out foam for the CS units? why the search for ccw EDF shrouds? The CS housings are slightly longer with longer stators to better smooth noise/turbulence. I understood those going to shorter housing changed the note or tune of the CS sound.
don't want to hack foam out for cs10 shroud and not end up using em then be left with a hacked up nacelle. Maybe once spare parts become available I can get spare nacelles.
Latest blog entry: Freewing Me262
Dec 21, 2012, 06:41 PM
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Maxthrottle's Avatar
I know what you mean. I have a 2 3/4" grind stone from the LHrdWS that I use for that situation. The lip should be the same but the OD of the EDF just needs to be removed. If I later use a smaller OD EDF I add a layer of foam rubber strip to make up what I removed.
Dec 21, 2012, 08:17 PM
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genghiskt's Avatar
Quote:
Originally Posted by v8truckin
don't want to hack foam out for cs10 shroud and not end up using em then be left with a hacked up nacelle. Maybe once spare parts become available I can get spare nacelles.
V8,
You will be when you see the price of the nacelle. It is ex, mate!

Dec 21, 2012, 09:17 PM
Should've, Would've, Could've
v8truckin's Avatar
Thread OP
Price... Someone has a price posted for spare parts? From the looks they might not be independent from the portion of the wing that mounts to the fuse.
Latest blog entry: Freewing Me262
Dec 21, 2012, 10:09 PM
It's watts for dinner
I have one of these on order too, but it's a kit from RC-Castle - I'm going to use the Cyclone Power 7010 10-blade 6S combos. I'm thinking that the recommended 3700 mAH battery is going to go bingo pretty quick on such a high powered setup. However, I already have a couple of GensAce 35C 3700s that I use in 90MM Freewing jets, so there's something to be said for standardization. Do you think the plane can handle a larger battery in terms of size or weight? What are you planning on using?


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