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Old Dec 13, 2011, 08:29 PM
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Originally Posted by AirX View Post
Hommel,

Go with a 2500 kv motor of your choice on 4s, just make sure that the motor mass is ~140-150gr to handle heat issues.

Et al the byproduct of heavier motor is that it is either larger diameter or it is longer providing a stinger magnetic field to handle the fans load making it more efficient. There is no getting more from a motor that is too small even if the kv is right.
I really wonder how many people here in this thread measure the rpm the fan turns or just calculating it because they do themselves and others a disservice by giving misleading information. Basically there is no way the average short can 28mm motor could turn this fan 40000 rpm much less 35000rpm without smoking. I think this is what ERH7771 is trying to say in some of his posts.

Cheers,
Eric B.
Right on Eric, I wish that everyone posting results in this thread would include RPM readings (calculated is meaningless) either from a Castle ICE or Eagle Tree or some other device measuring true RPM. This fan (and any other for that matter) takes power to turn it. The higher the RPM the higher the required power (measured in watts). Some motors are more efficient than others so that power in is greater than power out. But, for practical use the efficiency of most of our motors is close enough to be considered almost the same.

What I am trying to say is that to spin this fan at 45000 RPM it will take around 2500 Watts...... no matter what motor, KV, battery cell count, Battery capacity or ESC you use. In other words 45000 RPM with this fan is not practical. There are not any 28MM motors that I know of that can handle sustained 2500 Watts.
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Old Dec 13, 2011, 08:42 PM
Formerly "Heli Copter"
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For the record!

Quote:
Originally Posted by rfodor View Post
Right on Eric, I wish that everyone posting results in this thread would include RPM readings (calculated is meaningless) either from a Castle ICE or Eagle Tree or some other device measuring true RPM. This fan (and any other for that matter) takes power to turn it. The higher the RPM the higher the required power (measured in watts). Some motors are more efficient than others so that power in is greater than power out. But, for practical use the efficiency of most of our motors is close enough to be considered almost the same.

What I am trying to say is that to spin this fan at 45000 RPM it will take around 2500 Watts...... no matter what motor, KV, battery cell count, Battery capacity or ESC you use. In other words 45000 RPM with this fan is not practical. There are not any 28MM motors that I know of that can handle sustained 2500 Watts.
FYI, my previous rpm's are all from my Phoenix Ice Lite 100. I agree with you that we have to spin this fan at 45,000 rpm's to get decent thrust, but the load this fan creates at that rpm is more than a 28mm motor can handle. Maybe the reason this fan is so quiet is because it's not moving any air. LOL:
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Old Dec 13, 2011, 08:54 PM
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+1
Heli Copter you beat me to it, I was just going to post that our numbers were actual and have smoked two motors. guys this is why I said it doesn't look promising for this fan its load is way too high for 28mm motors, however we have not given up yet two more motors on the way to try
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Old Dec 13, 2011, 09:01 PM
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duplicate mssg
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Old Dec 13, 2011, 09:43 PM
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Is there any benefit for a 10 bladed fan versus say a 5? Is one better than the other for speed or maybe thrust or is it just the sound? Just curious.
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Old Dec 13, 2011, 10:13 PM
Hey Ya'll!! Watch THIS!!
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Here's a quote to answer your question: (Stuart Maxwell...Stumax)
"BTW, Stone, blade count means very little in absolute performance as long as you're sensible about the fan design (ie keep blade Re within usable limits). Tam's TJ120 powered Electra is a good example, another is a test we did between an SM89-45 and DS51, same model, same power, we measured the same top speed. A lot depends on how the multi blade fan is designed. You can design it for smaller exhaust diameters and get high efflux velocity and therefore very good dynamic thrust from it, but you do need to know what you're doing as the blades begin to interfere with each other and if you don't know how to deal with that the efficiency will be poor. The Chinese rip off fans are a classic example of copying something and not knowing what you're doing, their performance is way down compared to a well designed fan."
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Old Dec 13, 2011, 10:15 PM
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So I guess the answer would be .. The sound.
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Old Dec 14, 2011, 03:13 AM
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Quote:
Originally Posted by Michael Paxton View Post
Here's a quote to answer your question: (Stuart Maxwell...Stumax)
"BTW, Stone, blade count means very little in absolute performance as long as you're sensible about the fan design (ie keep blade Re within usable limits). Tam's TJ120 powered Electra is a good example, another is a test we did between an SM89-45 and DS51, same model, same power, we measured the same top speed. A lot depends on how the multi blade fan is designed. You can design it for smaller exhaust diameters and get high efflux velocity and therefore very good dynamic thrust from it, but you do need to know what you're doing as the blades begin to interfere with each other and if you don't know how to deal with that the efficiency will be poor. The Chinese rip off fans are a classic example of copying something and not knowing what you're doing, their performance is way down compared to a well designed fan."
To be honest, I don't think this is a poor design... I think Extreme_RC showed us that. Anyone claiming that +1500g at a decent 1.5 g/W is not practical should stick to a HET or Wemo and push those to the limit. Fact is that a lot of builders/flyers are not looking for the last extra mph... It makes more sense to put design effort in your airframe than forcing your fan into doing something it wasn't designed for in the first place...
This fan shows efficiency up to 2g/W in the lower power set ups which makes it ideal for your typical scale jet with a genuine bonus i.e. the turbofan sound.

@EricB. thanks for the guideline, I more or less came to a similair conclusion, but it is always a good thing to have someone else verify own findings.

Cheers,
H.
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Old Dec 14, 2011, 04:07 AM
Life begins at transition
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If it's lower efficiency than others of the same size, doesn't that mean it is poor?
Being a relative term, it of course implies 'compared to something else'.

There is no reason a well designed fan can't perform the same as a Wemo, regardless of the number of blades (per Stu's thing above). Design however costs serious time. I spent about two weeks' a while ago doing one, and that was only a first cut.
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Old Dec 14, 2011, 04:43 AM
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Quote:
Originally Posted by Odysis View Post
If it's lower efficiency than others of the same size, doesn't that mean it is poor?
Being a relative term, it of course implies 'compared to something else'.

There is no reason a well designed fan can't perform the same as a Wemo, regardless of the number of blades (per Stu's thing above). Design however costs serious time. I spent about two weeks' a while ago doing one, and that was only a first cut.
I disagree :-) What efficiency at what power level is the question one should ask. At "low" power levels, with the right motor this fan is as efficient as others. Only when pushed further it hits the ceiling before Wemo or Het do.

My findings with the CS show that at very low power levels (100-300W) the efficiency in terms of g/W is better than Wemo... Keep in mind that Wemo's were designed initially for speed480 brushed motors on max 200W. From that perspective the CS should be superior to a Wemo :-).

Given the right motor to my knowledge/experience so far the thrust/W curves look like this:



It shows that if you are not looking for imo insane thrust numbers the CS will do very well, even better than a Wemo...
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Old Dec 14, 2011, 04:55 AM
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Efficiency can't be expressed as g/w, or any other units for that matter. That confuses the issue, just like stating thrust and power without RPM. Half information and misleading assumptions.

Do you happen to know what that graph is based on? Which motor, exaust diameter etc? If that is indeed the case, the CS looks good for a parkie!
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Old Dec 14, 2011, 04:58 AM
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Quote:
Originally Posted by Michael Paxton View Post
So I guess the answer would be .. The sound.
Agreed....
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Old Dec 14, 2011, 05:19 AM
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Quote:
Originally Posted by Odysis View Post
Efficiency can't be expressed as g/w, or any other units for that matter. That confuses the issue, just like stating thrust and power without RPM. Half information and misleading assumptions.

Do you happen to know what that graph is based on? Which motor, exaust diameter etc? If that is indeed the case, the CS looks good for a parkie!
I know... efficiency is usually a percentage. But g/W is to us a very useful characteristic, though I agree that knowing other parameters is vital in understanding why a fan behaves like it does, I wouldn't call that half information, certainly not misleading...
One thing that is very clear to me in regard of the CS fan is that finding a matching motor on a given battery pack is much harder than with a Wemo or Het.
The graph is based on my own findings, hardly scientifically done. But I do know for sure that the CS fan initially puts out more thrust/W and drops off quickly if pushed further. Where the 2 curves cross, I don't know yet, but guestimated I would say somewhere around the 800W for the best optimized fan/motor combo.

The only point I try to make is that the CS is a very good fan for certain applications, top speed probably not being one of them, agreed!

I think Mark (Extreme_RC) tried some modifications on blade width on the CS fan in order to be able to push it further than the stock one. And without a doubt, if Wemo put some effort in this they will come up with a similar, probably better performing fan on high power set-ups.
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Old Dec 14, 2011, 07:35 AM
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Quote:
Originally Posted by rfodor View Post
Right on Eric, I wish that everyone posting results in this thread would include RPM readings (calculated is meaningless)..
If you take the 10-15% off the calculated you get +-5% on the actual, that's been proven over and over again.
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Old Dec 14, 2011, 07:37 AM
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Originally Posted by Heli Copter View Post
FYI, my previous rpm's are all from my Phoenix Ice Lite 100. I agree with you that we have to spin this fan at 45,000 rpm's to get decent thrust, but the load this fan creates at that rpm is more than a 28mm motor can handle. Maybe the reason this fan is so quiet is because it's not moving any air. LOL:
There have been a number of people including myself that have gotten wemo mini thrust numbers on this fan +-5% on watts.

It's very close, you have to calculate the RPM correctly or you'll get not so good results.

I've had almost 10 flights with my set up and have not smoked the motor and the performance is no different from SAPAC...

My results have been very close, extreme_rc showed earlier on 6s his 10 blade with his shroud is nearly identical to a wemo watts to thrust

Also, I don't see many people giving amps AND volts along with watts....if your setup isn't giving the thrust to watts you have to look at the volts also...if your pack is sagging that's going to affect thrust.

I'll give up 100 watts or so to be able to do dual 70mm setups without them sounding like fighting bees in the air or having to by over 200 dollars in fans
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Last edited by erh7771; Dec 14, 2011 at 07:47 AM.
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