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Oct 03, 2012, 01:16 PM
30 degrees, 8 poles, timing monitor OFF. Those are the settings for the JETI SPIN controller.

The timing has to do with how the controller handles the commutation of the motor. With the higher pole motors, you need higher timing (30 degrees is the max possible).
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Oct 18, 2012, 05:35 PM
Proud RC Addict
Air Head.. been a while since you posted. Did you spin things up? Results?

I have my Fan and controller now but I have a bit of work before I'm actually ready to put it in the airframe.
Oct 18, 2012, 11:36 PM
Registered User

Its on the test stand

I am waiting for some batteries that are scheduled for a Monday delivery - so it should be soon.
Oct 19, 2012, 11:29 AM
There are lots of videos of our fan system on YouTube and other places. Just to keep you entertained while you wait.
Oct 19, 2012, 12:02 PM
Registered User

Thanks Jim

What would be nice is some performance figures for the 20 KW you list your fan at.
Oct 19, 2012, 04:04 PM
Proud RC Addict
I actually did go watch some of your vids for kicks again. It's been a couple years since the infamous E-Victory speed pass. The vid said you'd build another one. Is that in the works still? Change of plans? I'd love to see one of those things full powered fly by.
Oct 20, 2012, 12:24 PM
We actually did finish the mold for the fuse for the twin Victory. With the original one (that crashed) we had to cut the top scoop off and fill in the big hole. We made a completely new mold and we have a brand new fuse... just no time to get it all done because of the other projects.

I don't have any aircraft that can handle 20Kw of performance.. it would take something huge to be able to carry the batteries necessary to get that performance (I figure somewhere around 50,000mAh of capacity). At that point, the weight is going to become and issue. This is one thing that people don't seem to understand about high power setups. With the Dynamax in particular, it takes about 1.2 HP ^ 3 for every additional 1000 RPMS after 32,000 RPMs. You just don't double the power input to get double the RPMs. Tom Cook says that the power requirement is basically cubed.
Oct 20, 2012, 06:39 PM
Registered User

OK Jim would you think this is close?

Since I am limited to 300 amps I don't think ill be able to run on 18 cells but if I consider some voltage drop it may be close. This is close to 19,000 watts.

How does this estimate look?

15S 36000 200
16S 37000 240
17S 38000 300

or is this more realistic?

Est Watts
32000 7700 150 Amps 14S
33000 9938
34000 12176
35000 14414
36000 16652
37000 18890
38000 21128

Is there a way to estimate the thrust at 38,000 RPM?

How about efflux?

I need to take it easy on the batteries to break them in but I plan to start blowing some air.

I did some quick number crunching and a 50,000 mAh 18 cell Zippy pack would weigh only 50 pounds. Gee Wizz whats wrong with this?

Ill be honest - you show 16 cell 205 amps 29 pounds of thrust on 6800 mAh batteries and then you jump to 50,000 mAh to get at the 20,000 Watts advertised.

Really 50 THOUSAND?

You also state a 15 cell 10,000 mAh battery provided 197 amps is this not a 20C discharge?

Now if were talking about specifics it would be nice to know the wattage at your listed performance. I estimate your 16 cell numbers at a bit over 12,000 Watts. So jumping 2 cells to make up the additional 40% to get to the 20KW is again an estimate but seems to be in line. Also I am estimating 66 volts on 18 cells and this adds up to 19,980 Watts which again I can only guess.

If I take 20,000 watts at 300 amps and pump this through a 12,000 mAh battery is this not a 25C discharge rate? This seems to be reasonable.

Why do I need a 50 pound battery to do this?

I guess it was my mistake that I assumed when you posted the information on the controllers you said you would have - the 24 cell would be the one for the 20 KW setup.....By the way where are these?

Yes, that is true. We have 3 types that we will be releasing:

14S / 175A - $199
18S / 200A - $249
24S / 250A - $299

It just seems a bit deceptive to advertise a setup that you cant even run. To say I need a 50 pound battery is a bit of disclosure that may have made a bit of difference with my fan selection. No controllers and a 50 pound battery - now I don't really understand what to do here

I will agree with this though- there are no airframes for this. I am looking at 15- 17 pounds for the fan, battery, and speed controller. 50,000 Really


As far as understanding. I am a licensed electrical contractor and have 30 plus years in the trade. Stating that there is something that people dont understand - well I am going to pass through this. Again you have PLASTERED 20KW and I bought this to run the fan there. I do not agree that I need a 50,000 mAh battery to do this.

I bought this as a 20 Kilowatt Fan - with the intent of running it there!

18 cells at 3.7 volts and 300 amps is right there. I do not need a 50 pound battery to produce this unless I have been doing the math wrong for the past 30 years.
Last edited by Air Head; Oct 21, 2012 at 09:44 PM.
Oct 22, 2012, 07:57 PM
If your batteries will hold the voltage, then that would be fine. They won't. That is where your math is off. You need about 50,000mAh of capacity to hold that kind of voltage, yes, even with "80C" batteries that are now available. I would expect about 3.4v to 3.5v peak after 10 seconds with 10,000mAh packs, and you will likely see around 235A.

There is nothing deceptive. Nobody, not even us, will ever see the 20KW figure with 18S in an aircraft. We have this figure to show the head room that is available. You won't be able to "run it there" unless you are going to lug around 42 pounds of batteries (which is what a 18S 50,000mAh setup weighs). That would be a bit ridiculous. You would be better off with 16S/10,000mAh and a lighter aircraft.

One thing I will definitely warn you about - if you are going to play with this kind of power, make damn sure that your controller will handle it!! One simple miscalculation in the commutation will end up in utter disaster. We have seen it happen a couple of times where the controller stuttered, causing it to blow up, and in one case jolted the motor hard enough to sheer the shaft at the C-clip location. If the motor is suddenly trying to stop or run backwards, the rotating mass wins and something has to give - causing the sheer and the rotor blows up. This is why we don't have C-clips cut into our shafts anymore. Now, it would probably bend the shaft and beat the rotor inside housing, tearing it up. Just be careful. Do lower cell runs first to get an idea of just how scary this is. It spooks me to even run these on a test stand anymore, and ours is bullet proof (literally!)

Other than the controllers that we sold (mentioned above in your post), I have not seen a single 18S controller that has been tested with an 8 pole outrunner motor, so be sure you test whatever controller you are using to make 100% sure it is compatible!
Last edited by JimDrew; Oct 22, 2012 at 08:16 PM.
Oct 22, 2012, 09:05 PM
Proud RC Addict
Are there even any controllers? The specs on the Jeti 300 say up to 14S. Not sure if you can use the jetibox to program it to take a higher cell count or not. What else is out there?
Oct 22, 2012, 09:14 PM
Registered User

Jesus Christ I am getting a headache

Where the hell are the friggin controllers. Man I have an overweight 12 cell setup. This is making me crazy!!!!

Like I mentioned id be willing to drive to you to run this up. The more this goes on the more reluctant I am to even run the fan.

Right no controllers so I have a 20KW fan and I can do what 10KW?


Nothing deceptive at all I agree but I work with specifications all day long and I cant seem to get a grasp on a 20 KW fan that will never be run at 20KW. You can have all the headroom you want but you sell an advertised 20KW fan and now you say ill never be able to run that unless I carry a 42 pound battery and a speed controller that does not exist.

I did not buy headroom I bought an advertised 20KW FAN

" The factory tested our motors to 23Kw"



"We will have them at the AMA show next week".

I now have a $2000.00 pile of controllers and now I am hesitant to even run the fan. Plus the pile of batteries that ill photograph later

WHY THE HELL AM I A GUINEA PIG ????????????????\

Now I am afraid to run the fan...

Oh jeee the battery is 42 pounds not 50 sorry I missed that, but I used a listed specification in my calculation and ill bet you a 20KW speed controller that my math is correct. 42, 50 does it even matter.

I need a beer!
Last edited by Air Head; Oct 22, 2012 at 10:45 PM.
Oct 22, 2012, 10:14 PM
Registered User

38,000 rpm

Jim is it possible to get the thrust at 38,000 rpm? Id like to know where the mythical target I am chasing even is.
And the efflux velocity......

Last edited by Air Head; Oct 22, 2012 at 10:31 PM.
Oct 23, 2012, 10:11 PM
Registered User

make damn sure that your controller will handle it!!

and how might I be able to do that?????????????????

Oct 24, 2012, 08:05 PM
Originally Posted by mulicheng
Are there even any controllers? The specs on the Jeti 300 say up to 14S. Not sure if you can use the jetibox to program it to take a higher cell count or not. What else is out there?
Yes, there are some controllers that do exist. We sold them for awhile, but the company in China wanted to redesign the controller to make it safer. These came from hang glider systems. We still don't have access to this new 'safer' controller. I think that just like Castle, Scorpion, and a few other companies, the danger is just too severe with anything over 50VDC.

JETI controllers work to 15S. You just need the SPIN BOX to set it to handle 15S. I have been using 15S for years now without a single controller failure.
Oct 24, 2012, 08:07 PM
Originally Posted by Air Head
Jim is it possible to get the thrust at 38,000 rpm? Id like to know where the mythical target I am chasing even is.
And the efflux velocity......

We calculate the thrust at over 31 pounds. Efflux is a function of the exist diameter vs. the volume. You can calculate the CFM based on 5" diameter and thrust. From there, you can calculate the efflux and approximate thrust using different exit diameters.

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