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Old Jun 24, 2012, 08:09 PM
Lee Liddle
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Carrollton, Tx
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Question
Fastest Efflux Speeds for EDF??

Don`t ya just love these Fastest, Best, Highest, Biggest, Coolest, threads?

I`ve been pushing a couple of fans to stupid levels lately and have recorded so pretty high efflux speeds. So I`m wondering what are some numbers that you`ve either personaly seen, or have seen a video showing.

This isn`t a contest, I`m just looking for some input for comparison. The size and type of fan is important data as well as the aprox watt level at which the speed was measured.

If I get enough data, I`ll make a graph that can give us an idea of what is going on in this area. Any input is appreciated.


I`m particularly intrested in high speeds, but also need lower speeds at lower power levels to fill in the graph

70mm

CS-70-10blade.....260mph at 3.5kw








90mm

Hayoe 90mm shroud with a 100mm rotor fitted.......290mph at 7.6kw
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Old Jun 25, 2012, 12:27 AM
Carbon fiber is our friend
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United States, CA, Lodi
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Quote:
Originally Posted by Knife Liddle View Post
I`ve been pushing a couple of fans to stupid levels lately
Um, you mean always, not lately

Measured in the plane, or on a stand? Eagle tree for airspeed?
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Old Jun 25, 2012, 02:26 AM
Lee Liddle
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Carrollton, Tx
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Quote:
Originally Posted by Steve C View Post
Um, you mean always, not lately

Measured in the plane, or on a stand? Eagle tree for airspeed?
Well, only for the past 5 years or so.

To compare data, it should be with a lip and an open exhaust on the bench I think.

I`m using the two tube ET airspeed sensor. I don`t know what other meathods are available, but I`m just looking for any data that I can find at this point.
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Old Jun 25, 2012, 02:34 AM
Lee Liddle
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Carrollton, Tx
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Here`s Something Interesting

Well have you ever wondered why we have all liked the Midifan so much and thumbed our nose at the Haoye? This may give some insight.

I went back to Carl Rich`s data on the Midifan and plotted it on a graph, then added my recent data on the Haoye 90mm (with a 100mm rotor). I think this tells the tale.

At power levels from zero up to the 3.5kw range the Midi is clearly better, but after that the Midi looses it`s punch and then the higher pitched Haoye takes it to a different level.

The red line of the Midi data also explains why most 90mm EDF jets seem to hit a wall in the area of 190mph. It`s a simple fact that you won`t be able to go any faster than about 80% of you efflux speed due to drag and losses. So, since the Midifan taps out at about 230mph that will get you to about 185mph on a good day.

So, now, with all of the R&D going into the bigger Heli outrunners, we have the power plants to put the Haoye`s agressive pitch to good use. I think we will eventually find out a similar situation with the Ramtec fan. With it`s more agressive pitch, with enough power supplied,it should be able to reach higher speeds than other fans in its class.
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Old Jun 25, 2012, 08:23 AM
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Quote:
Originally Posted by Knife Liddle View Post
Well have you ever wondered why we have all liked the Midifan so much and thumbed our nose at the Haoye? This may give some insight.

I went back to Carl Rich`s data on the Midifan and plotted it on a graph, then added my recent data on the Haoye 90mm (with a 100mm rotor). I think this tells the tale.

At power levels from zero up to the 3.5kw range the Midi is clearly better, but after that the Midi looses it`s punch and then the higher pitched Haoye takes it to a different level.

The red line of the Midi data also explains why most 90mm EDF jets seem to hit a wall in the area of 190mph. It`s a simple fact that you won`t be able to go any faster than about 80% of you efflux speed due to drag and losses. So, since the Midifan taps out at about 230mph that will get you to about 185mph on a good day.

So, now, with all of the R&D going into the bigger Heli outrunners, we have the power plants to put the Haoye`s agressive pitch to good use. I think we will eventually find out a similar situation with the Ramtec fan. With it`s more agressive pitch, with enough power supplied,it should be able to reach higher speeds than other fans in its class.
Was the midi ran with a thrust tube in that graph?

regards
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Old Jun 25, 2012, 09:07 AM
Lee Liddle
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Carrollton, Tx
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I'm pretty sure it was open exhaust, but I'd have to go back and read his text.
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Old Jun 25, 2012, 10:24 AM
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Lee,
It is interesting to note that fan manufacturers market high pitch, lower blade count fans for the highest performance. For scale sound it seems they go with higher blade counts and less pitch.

For the speed:
http://www.stumaxaircraft.com/pages/SM110-45.htm
http://www.schuebeler-jets.de/en/hdt...4-dia-hdt.html
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Old Jun 25, 2012, 10:54 AM
Lee Liddle
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Carrollton, Tx
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Quote:
Originally Posted by pdawg View Post
Lee,
It is interesting to note that fan manufacturers market high pitch, lower blade count fans for the highest performance. For scale sound it seems they go with higher blade counts and less pitch.

For the speed:
http://www.stumaxaircraft.com/pages/SM110-45.htm
http://www.schuebeler-jets.de/en/hdt...4-dia-hdt.html
Yes you are right. That seems to be the general rule, but it may be because they are focusing on power levels below 4kw. But the chart shows that the "speed " fans max out in the low 200's while the higher blade count fans can approach 300mph if you add enough power.

This chart seems to verify that and if you look at efflux speeds posted for Dynamax you'll see speeds approaching 300 also. The key is how much power a given rotor can handle before it blows up.
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Old Jun 25, 2012, 11:20 AM
Bypass Ratio = Infinity
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Quote:
Originally Posted by Knife Liddle View Post
The key is how much power a given rotor can handle before it blows up.
Bingo.
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Old Jun 25, 2012, 12:24 PM
BVM Viper Fever
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Lee,
If these charts you're referring to are the result of static testing one could argue that a high blade count fan has an advantage accelerating static air. A higher pitched, low blade count rotor might not perform as well statically but you might be surprised with inflight conditions. It would obviously need a slick airframe to go with it.
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Old Jun 25, 2012, 12:36 PM
Lee Liddle
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Carrollton, Tx
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I'm thinking about doing some tests that would simulate in flights conditions. That would be interesting for sure. I've read over and over that edf don't unload in flight, but I've already seen evidence that they do. The unloading might take the form of lower amp draw for the same rpm level instead of higher rpm, but my observation is that they do unload.
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Old Jun 25, 2012, 12:47 PM
BVM Viper Fever
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Once upon a time...

Not saying EDF's should have just one blade but given a certain amount of watts to work with I would have that power turning fewer, high pitched blades as opposed to many lower pitched blades. Again, a very low drag airframe would be needed for a setup like that.
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Old Jun 25, 2012, 02:24 PM
smug in granny panties
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Hitting the nail on the head again lee! Now we all need to come up with a system of checking static in flight in line with efflux. Ie one might have gobs of static at full with efflux but! How much is left at half. And visa versa, tons of efflux but at speed how fast does that fall off. This was my next goal in life to create a load sensor setup for in flight, but alas sidelined with youngins right now so it has to wait.
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Old Jun 25, 2012, 06:30 PM
shut up & fly
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Quote:
Originally Posted by Steve C View Post
Um, you mean always, not lately
hillarious!!
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Old Jun 25, 2012, 07:22 PM
smug in granny panties
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Oh well fright Cept for unload part, they just don't, but! I have seen a duct or shroud cause varying feed problems.

Barry
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