rotational torque.

Of-course! Two counter rotating fans would be the ideal solution, but also much more costly $ wise. Just need to figure out the after burner feature; might hang out the back a bit though....

And the winner of the GOLD STAR is- DrKnow65! :yipi: :party: :yes:

Exactly. Rotational torque, and a lot of it with this thing at 50000 rpm. If that fan was in the middle of the chassis it would probably flip over during on-power right-hand turns! I've had it happen with previous versions of this type of craft (yeah I've built them before).

Neil I've looked all over for a set of fans that could be used for a counter-rotating setup. The only ones I found are way too small (50mm) and nowhere near as powerful.

Hey DrKnow65 I like your signature a lot. The only difference is I can draw pretty good :mdr:, but I'm still dirt poor.

one day cnc's will be dirt cheap... I'll be dead just before that happens hehehe.

When I read "nitro" it dosn't look like it spelled with four letters, but I know better :)

Answer me this:
 

Have any of you guys ever run a Lehner reliably at high speeds? Like in the 46-50K RPM range? I'm having second thoughts about dropping a $330 motor into this car, only to have it self-destruct on the first run. :no:

Is there anything I could do to further protect the rotor from the huge centrifugal forces that are put on it? The Plettenberg motors have wrapped rotors - would this be possible on a 1950? Given what I've seen/heard about Feigao, I would never attempt this with their motors even though they're cheap to replace.

I have been past the 50K with a Basic 5300. Lehner claims the 19 series can go up to 50K and I've heard of some guys going up to 100K in those crazy fast planes.

I think the lehner claims up to 100K with the 19 series... before they had English on their websites, they use to post that the 19 series can do 100000u/min.. I'm guessing that's the same as rpms.. ?
.. ... anyways.. the 1930/6 was my first good brushless motor.. went into stock emaxx... I ran at 12 Cells (around 45-50K).. no problem.. I then ran 18 Cells(70-75K).. although it got hot... it was never damaged...

i've melted a bearing in a 5300 on 12 cells (75k rpm). but I ran that setup in my tc3 for about two three months before I had any problems. the rotor came apart on one of my Hacker 8S' on 16 cells (75k rpm). that was when i blipped the throttle unloaded. loaded, I never had any problems w/ my other 8s on 16 cells.. I'd stay away from 75k, as that's the only time i've had motor problems.. 50k, I don't worry though.

Okay, I don't know how I missed this project.

First of all, great idea! I have that same ducted fan unit in a completely different project of mine.

Second, the manufacturer may say that the fan unit can take more than 27,000 RPM. Don't pass 30,000 RPM. I was using a Feigao 12XL and 24v lead acid through a Phoenix-60. Here are some numbers after the fan was running for a minute or two:
-21v
-110amps
~2300 watts (3HP)
-~25,000 RPM
And yes, the Phoenix-60 with some copper heatsinks and 6 extra capacitors was pushing 110amps. Unfortunately my watt meter couldn't, and was smoking/melting a bit.

I've already broken two of the fan blades while keeping the fan around 25,000 RPM tops, without a load on the fan (just spinning the fan in open air). That said, my setup is a bit different, so that could have cause the blades to break, or it might not have.

Without modifying the unit, it can only accept motors with a diameter up to about 37mm. That means Neu 15xx series motors won't fit, unless you cut the shrouding around the motor.

If you don't have the ESC already, look into the OEMRC Sentilon 100amp 12s airplane ESC:
https://www.unitedhobbies.com/UNITED...idProduct=4691
https://www.unitedhobbies.com/UNITED...idProduct=2169

And let me say it again, don't spin the unit too much past 30k RPM.

Thanks everyone. Metalman I didn't see that bit about 30K RPM anywhere in the instructions for the fan. Thanks for mentioning it. It is good to know that the Lehner can take the beating without kerploding, but I guess I have to find another fan. I really want to stick with a single fan setup to save the extra weight. I need a MINIMUM 9# of thrust for the project because I'm aiming for at least a 1:1 thrust-to-weight ratio. Also, I want to stay with the 90mm size fan, or smaller if such a thing exists.

Please, no more links to those R/C turbines. I know they're awesome but unless you want to donate one then they are out of the question.

Have you thought about the carbon fiber EDF units? I'm pretty sure that is what those 200MPH+ EDF planes use.

Oh, CF units- I've seen a retailer of those somewhere...I'll be back in 10.

It's not in the instructions, I think of it as more of a mechanical limit. An older guy at the LHS I work at is a retired aerospace engineer, and big RC airplane afficionado, said that the fan unit shouldn't be used past maybe 15,000 RPM. But asking 9lbs of thrust out of it is most likely too much.