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Old Aug 27, 2008, 06:47 PM
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5-year WeMoTec Fan Overhaul

I have been flying the Aeronaut Rafale for about five years now,

http://www.rcgroups.com/forums/showt...&page=7&pp=100


it was time for a fan service. The first flight was back in November 2003, and it had been flying continuosly since then ...

In particular I wanted to switch to a more powerful (but slightly heavier) motors.

So did fans, motors and esc's hold up after five years of flying ?

Rafale 2005 video, takeoff at ca. half throttle:

Rafale twin 90mm EDF by Aeronaut (1 min 20 sec)



.
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Old Aug 27, 2008, 06:52 PM
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So far most of the apparent wear and tear has been in endless tire changes and frequent Springair retract dust cleaning, and of course LiPo batteries which don't last

Otherwise the airframe is in remarkable good condition after five years, the paint has to be regularly re-touched every six months or so.

.
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Old Aug 27, 2008, 06:58 PM
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The Aeronaut Rafale is in fact rather easy to service - the back end comes off with a few screws and other retainers, and exposes the fans.

I think this was the first time I opened the back end in five years ...

.
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Old Aug 27, 2008, 07:06 PM
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The most recent flight I had with this Rafale was last weekend ... It was flying nicely but I think the Megas were overworked a bit. In the 1000W+ range their efficiency drops a bit and it is noticeable in flight: batteries get hot.

So the plan is to replace them with Hacker B50's

The Megas look like they are in excellent condition, a tribute to the quality of the manufacturer.

On the other hand the duct tape used, besides silicone, to hold the exhausts, has turned to powder!

.
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Old Aug 27, 2008, 07:12 PM
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After a few years the tough glass-fiber reinforced fans still get badly pitted on takeoff...

Even though the Rafale sits relatively high, it sucks all sort of dust into the intakes on takeoff.

The problem is not purely an esthetic one - it is known that a pitted or otherwise imperfect leading edge tends to reduce any airfoil's efficiency significantly.

I needed therefore to sand and reshape the LE of all fan blades

.
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Old Aug 27, 2008, 07:21 PM
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Even though the two large Megas were still firmly secured in the fan shroud (I used masking tape as well as special glue), both fans were cracked from edf flying fatigue where the screws are seated.

This confirms the old wisdom that the WeMoTec Midifan should probably not be used on more than 1500-1800W or so - unless you plan from the beginning to have very few flights .

.
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Old Aug 27, 2008, 07:28 PM
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At this point one (or any reasonable person for that matter) could just replace the fans, maybe with two DS-51 on sale on e-bay ...

Or just carefully and patiently sand the fan blade LE, add an aluminum plate on the shroud motor mount, re-balance magnetically both rotors, and re-seat the new Hacker B50 motors with plenty of back support & cooling spacing...

.
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Old Aug 27, 2008, 07:33 PM
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I ended up using the original plastic spinners, which I had balanced with tape (and which was still there after five years).

The aluminum ones would not slip on no matter what I would do, when I pushed eventually hard enough one deformed, so I stuck to my trusty old ones...


.
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Old Aug 27, 2008, 07:45 PM
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The wiring needed to be redone as the old one looked worn and I will put better gold connectors.

The Hacker Master 70A esc's will be replaced by twin Hacker Master 77's.

The old 70A ones were not doing too well at half throttle, another reason for the 5-yr overhaul.

Still, the two esc's look like new after five years of abuse and 50+A peak currents (on a 70A rating), and so do the caps. It pays to read the instructions.

The instructions say: 20cm max from esc to batt. So it helps to read the instructions and the caps still look like new, no heat damage from switching so far.

.
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Old Aug 27, 2008, 07:49 PM
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Thats a great report Herb, I think I only have 1 EDF out of too many thats lasted that long.
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Old Aug 27, 2008, 07:52 PM
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The old Mylar tubes looked still in good shape, but the original suggestion of Aeronaut of using 76mm diam worked maybe in 2002 but is way off for power levels above 2000W ...

So the Mylar tubes needed to be re-opened at the seam, and taped back to a 64mm outlet. Luckily there was no need to make new ones, Mylar is quite resilient and seemingly lasts forever ...

.
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Old Aug 27, 2008, 07:54 PM
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Ken we all do, it's part of the hobby

Some designs last longer than others, and weight has something to do with it. Internet flying, well that's another story
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Old Aug 27, 2008, 08:04 PM
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The new thrust tubes need to be aligned very carefully at the end, otherwise I noticed trim issue with power on/off.

It is surprising to notice what a small effect a few mm's of thrust tube mis-alignment can have of the handling at speed.

Thrust tubes secured temporarily in place for alignement, outlet reduced to 64mm, 12mm less than before.

.
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Old Aug 28, 2008, 04:57 AM
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Sweet Herb nice job.
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Old Aug 28, 2008, 09:21 AM
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Nice review Herb!

You might reconsider the Jepe shrouds too in future. The sound is as like the full carbon fibre versions
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Old Aug 28, 2008, 10:00 AM
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Herb,

Good information, thanks for sharing.

Regards, Bill
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Old Aug 28, 2008, 12:25 PM
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very good stuff Herb! like the detail on the fan housings too, this gets overlooked a lot! we get so fixated on rotors we forget. also with EDF being hard on front bearings anyway, when they things flex a lot and rotor can rub but not fail, it still does yet even more damage to front bearing.

Barry
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Old Aug 28, 2008, 01:31 PM
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Thanks for the comments ...

I did consider at some point using two JePe fans, but one had a stripped grubscrew, which lead eventually to the fan coming apart when removing the rotor aluminum hub from the motor shaft. The stators had been glued back/reinforced already several times before on this fan.

The one-piece WeMoTec MidiFan shroud is actually quite a bit stronger - apart from the mentioned motor mount area - than the Jepe fan.

.
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Old Aug 28, 2008, 01:39 PM
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It would seem to me that either the WeMotec MidiFan shroud gets re-designed a bit in the motor mount area to take it to higher power levels, or the present design could be limited by this issue to ca. 1500-1800W max.

It is my experience that the rotor itself is very sturdy (in spite of the recurring "blade stretch" nonsense that's repeated here occasionally and has developed into some sort of urban myth to "explain" why unbalanced fans & motors blow apart).

It would be nice if WeMoTec were to add a new 90mm fan with a higher pitch rotor (and maybe one less blade). Then it would not be necessary to sacrifice efficiency to reduce the exhausts in order to get high efflux, as I have done in the Rafale.

.
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Old Aug 28, 2008, 01:49 PM
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Quote:
Originally Posted by Herb
The aluminum ones would not slip on no matter what I would do, when I pushed eventually hard enough one deformed, so I stuck to my trusty old ones...
I had the same problem with the new aluminum minifan spinners. Like you, I elected to set them aside rather than try to force them into place.
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Old Aug 28, 2008, 02:21 PM
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Good thread Herb.

You had me reaching my similarly aged Vector II down from the workshop wall to check the DS51 blades. They are somewhat pitted, not as much as yours, but I do fly from tarmac and the model probably hasn't had the amount of flying yours has. Besides, the over-wing intake should inhibit FOD ingress. My main problem has always been wet (well it is England!) grit jamming one or other Springair 600 series main gear.

My current plan is to replace the FUN600/17 on 6S Lipos with a Lehner 1950/10 on 12S A123s (= 9S lipo but heavier) to up the power from around 1kW to 1.7kW. The A123 pack will be about 10oz lighter than the 20-cell GP3300s the ship flew with before lipos came on the scene.

Good luck with your refit.

Gordon
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Old Aug 28, 2008, 03:22 PM
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You have a positive view on the weight penalty. NiCd edf pilots are smarter LOl!!
Good luck on your new pack.

I found the lehners and hackers to be heavy. Do some math with the Megas. The lower Amp draw needs less iron Cools down faster and it will be faster in operation for the next flight
grtz, Erik
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Old Aug 28, 2008, 03:31 PM
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what size plane is that?
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Old Aug 28, 2008, 04:06 PM
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and flat out less depression in flight too! even within c limits of a cell.
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Old Aug 28, 2008, 04:21 PM
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Quote:
Originally Posted by Erik v. Schaik
Do some math with the Megas. Erik
Nope. I already have two unused Lehners (and the DS51s for them) so I don't need to buy any more 90mm EDF motors for a long time

Gordon
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Old Aug 28, 2008, 05:06 PM
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Quote:
Originally Posted by Gordon
... My current plan is to replace the FUN600/17 on 6S Lipos with a Lehner 1950/10 on 12S A123s (= 9S lipo but heavier) to up the power from around 1kW to 1.7kW. ...
If it was my plane I would keep the Fun 600 (a hell of a motor), remove any tailcone from the fan to ensure max cooling, and go fly it on 7S.

The Fun 600 should do fine on 1600W with good edf cooling, in any case you will not need full throttle most of the time. Keep in mind that you are in the 6g/Watt region with a 90-92% efficient 270g motor which is pretty safe.

But on the other hand since you already have that Lehner 1950 (a pretty hefty 360g motor) ....

Keep in mind that some two pole motors don't like long runs at half throttle (discussion with DS), eddy currents heat up the rotor like crazy, and even major cooling on the windings might not help (how do I know ).


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Old Aug 28, 2008, 07:25 PM
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I thought 2 polers didnt like to run at half or full? lol sorry couldn't resist Herb! But I agree on the Kontroniks, bang for the buck there tough to beat.


Barry
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Old Aug 29, 2008, 01:44 PM
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Quote:
Originally Posted by DanSavage
I had the same problem with the new aluminum minifan spinners. Like you, I elected to set them aside rather than try to force them into place.
In my case the alu spinners went on well on the MiniFans but not on the MidiFans ... I think there might be some slight manufacturing tolerances involved, in the rotors themselves more than in the spinners.
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Old Aug 29, 2008, 01:59 PM
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Same thing on my midis. I hung the complete pod on the shaft in a drill machine and at low rpm I placed a file against the rotor side to fit the spinner. A small chamfer is nice as well.

hope this helps,

Erik
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Old Aug 30, 2008, 04:44 AM
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aluminum spinner and old rotor

DanSavage & Herb
If I remember it right those aluminum spinners are good tight fit to new midi rotors but not with older ones. This is what I have read here somewhere.
My Pro's and metal spinners are still on their way to me so I have no way to actually confirm this - yet.
/Jyri
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Old Aug 30, 2008, 12:22 PM
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Hi Herb

I seem to remember a pic of your FUN600 with vented end bells, which my 5 year old one hasn't. The Lehner has lots of thin (around 2mm thick) slices in its magnets to reduce eddy currents - I believe that Lehner invented that rotor setup for 2-polers - whereas the FUN 600 only has 3 slices so would suffer more from eddy currents than the Lehner at mid-range currents.

Also, I want to power the plane with what I have already, and I couldn't make up a 7S lipo, though I could do a 10S A123 by connecting exisiting 6S and 4S, which would be a bit too hot. I've been running the FUN600 on 8S A123 and that's been pretty good and could knock up one 3S from cells I have laying around, so could try a 6+3= 9S A123 with the FUN600. That'd be a tad less pokey than a 7S lipo so the motor ought to survive. But my escs max at 55A cont 70A burst and are already approaching 55A with 6S lipo or 8S A123, so they'd be at risk with the FUN600 on more cells, especially at part throttle which Schulze and Kontronik say is a big no-no if you overcurrent the esc and rely on part throttle to keep the currrent down. With the Lehner option current wouldn't be very much over the 55A ... which is why I'm thinking of going with the Lehner.


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Old Aug 30, 2008, 12:46 PM
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Sounds all good Gordon, I see your motivation.

Lehner is now permanently off my list, I think he should just stick to making motors for boats

Here's what Oliver stated about the WeMoTec MidiFan in that thread:

" Same fan unit, but balanced, with aluminum spinner (which was silently introduced at an earlier point).

I must clearly say, the cracks that Herb detected after five years of use happen, no question, but they do not make the fan fail, otherwise he would not have detected them only do to maintenance.

The inner tube itself stays intact, so the motor is fixed in the shroud.
Although I currently think about a way to make this section stronger with the next batch to be prepared for future abuse.

One thing I would definitely NOT recommend is to use the old plastic spinners on more than 1000 W. They show fatigue over the years and should be left aside, at least the early long ones, not the shorter ones we delivered for the last five years, until we switched to aluminum.
BTW aluminum spinners will sometimes not match very old rotors. If you experience this, please contact the manufacturer for a solution.

I personally see the limit of proper use for the Midi Fan at about 2.000 - 2.200 W.
Above that I recommend Schuebeler for now.

Oliver
"

http://www.rcgroups.com/forums/showp...&postcount=283
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Old Aug 30, 2008, 02:17 PM
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Quote:
Originally Posted by Herb
Lehner is now permanently off my list, I think he should just stick to making motors for boats
You're probably right Herb If mine go the same way I'll most likely replace them with Neu 1515/1.5Y which guys seem to be using with success in 90mm at up to 2kW.

Ref the Midifan cracks, I had one do that very quickly several years ago because unlike you I hadn't supported the rear of the motor. I epoxied a fibreglass disc, with slots for air passage, inside the front of the motor tube and supported the rear end of the motor, with no further problems.

http://www.rcgroups.com/forums/showthread.php?t=156604

Gordon
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Old Aug 30, 2008, 03:51 PM
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55A is only 2.3minutes full throttle flight time right? your pack wil have a short lifespan as well.
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Old Aug 30, 2008, 03:53 PM
My project: FAIREY DELTA 1
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55A is only 2.3minutes full throttle flight time right? your pack wil have a short lifespan as well. You might toy around with fancalc for a bit.

Good luck, Erik
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Old Aug 31, 2008, 01:22 AM
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Nice thread!
5 years of takeoffs and landings on that dirt field is a pretty remarkable feat!
Maybe I missed it, are you replacing the fanunits or repairing the cracks?
Is repair even an option?

Bruce
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Old Aug 31, 2008, 12:33 PM
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How long now have I been saying this stuff about the lehners! And I know I still have most, if not all, of my kontronik and mega's bought years ago. But any lehner I either got rid of right away or it cooked.


Barry
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Old Sep 01, 2008, 02:22 PM
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It was my first and last Lehner ... some people swear (or should I say: used to swear) at them being the best - and I did trust the testing.

I think Gordon will be fine as he is only pulling 1700W out of that big 365g 1950 motor. The revised rating for it (and I am talking about the open ended latest and greatest one I had) is 2200W max.

DS's new revised rule (don't ask me how it got revised ) is 6g/W max on the Lehner 1950's in DS-51 applications. It is supposedly much higher for the latest generation Plettenberg 220's ... I won't go here into the issue of temperature rating of the magnets, and winding coverings.

Bruce, I replaced one Midi fan and kept /fixed the other one which was only slightly cracked. In any case the Rafale flies fine on just one fan . The two Hacker B50's I used are also five years old ...
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Old Sep 02, 2008, 08:32 AM
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Hi Herb

Iím confident that my 1950/10 will be OK as I chose that motor using calculations based on Danielís guidance which I posted on this thread some 2.1/2 years ago: http://www.rcgroups.com/forums/showthread.php?t=463710

At that time my original Schuebeler lipos were good for up to 3.4V/cell (now nearly 4 years old and after much usage they manage 3.2V/cell at about 40A), but all modern lipos such as your Kokams are much better than that. Looking back at my notes I wanted 9s at 3.4V/cell and 55A for around 1700W input, and the calc produced a 1271 rpm/V motor weighing 432g, the nearest Lehner wich would fit the DS51 being the 355g 1950/10.

Modern 9S lipos at 3.7V/cell will risk smoking the motor, and 8S would be safer. A 12s A123 pack at around the 2.6V/cell Iíve measured on load should be safe. Regarding motor weight, Iím not too worried as the additional 3oz or so is swamped by model and A123 weight, and Lehner + 12xA123 is still much lighter than FUN600 + 20x2400 (at about 50A) which the model started life with 5 years ago.

From your F-16 thread: Setup: DS-51 hdt fan with Lehner 1950-9, Jeti Spin 99 esc with fins in the ducting, Kokam 4000 30C H5 9S, Watts 2500, Amps 82 (measured in dry run at home, after 1 min), battery still at ambient temp after 3 min mixed throttle run.

Doing the same sums for 2500W input at say 90% efficiency (which your motor clearly wasnít) equates to 2250 W shaft power which requires the DS51 graph extrapolating to get the rpm figure which is around 42k rpm. The 2500W at 82A equates to 30.5V, which equates to a Kv of 42000/30.5 = 1377 rpm/v and the nearest 1950 is the 9-wind.

BUT Ö doing Lehnerís motor weight calc produces a required weight of 2500/4.2 = 595g, and Lehner donít make such a motor in their 1950 range

So if Daniel supplied you with a plug Ďn play setup, it looks as if he must have missed the weight part of the calc.

I note that using your figures, Fancalc misses this too.

FWIW, plugging 30.5V, 2500W and 42k rpm into the Lehner Rechner: http://www.lehner-motoren.de/rechner.php comes up with the 2240/11 which weighs 450g and which certainly wonít fit the DS51.

I do agree with you that in these days of power figures we used to only dream of, Lehners probably arenít the best motors to choose for EDF as motors and batteries have moved on since the days when Lehner was one of only a very few motor manufacturers making anywhere near suitable motors back in the late 1990s.

However, as I don't know anyone with an electric boat which needs a 1950/10, I'm stuck with my two

Gordon
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Old Sep 02, 2008, 12:52 PM
Julian T
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I wouldn't fret too much Gordon. At least Lehners are obtainable ;-) And my 1950/11 spins a Midi beautifully smoothly and fuss free at just under 2000 watts on 9s! A bit much for a Midi Pro possibly so the Schubi is around the corner :-)

Cheers

Julian
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Old Sep 02, 2008, 07:44 PM
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Quote:
Originally Posted by Gordon
... From your F-16 thread ... 1377 rpm/v and the nearest 1950 is the 9-wind. BUT Ö doing Lehnerís motor weight calc produces a required weight of 2500/4.2 = 595g, and Lehner donít make such a motor in their 1950 range ... So if Daniel supplied you with a plug Ďn play setup, it looks as if he must have missed ... Gordon
Yes, as I said, your setup should be fine.

Gordon, Lehner's calc is not for fans. His calc is for props or maybe boats , some setups envisioned with minimal cooling. Also, his way of measuring kv differs slightly from the usual one (under load vs. no load).

Wheras DS test all motors in his fans. Cooling is a crucial issue in power rating, as you found out smoking your Plettenbergs ...

What the max amps or better watts is for each motor is a matter of testing, in the intended enviroment. Keep in mind that lots of other motors get their specs exceeded in edf, sometimes as much as a factor of two. It is an issue of cooling. That was the issue with the Lehner 1950.

Btw no. 2, there are very few larger (ie larger than the 1950) motors for the DS-51, in particular none by Lehner, otherwise that would have been the preferred route.

The warranty replacement will be most likely, as I already discussed in the F-16 thread, a Plettenberg roughly in the same weight class as the Lehner ... I had a Plettenberg Ultra 930 and it lasted me five years of the heaviest abuse; the Mega motors which form part of the subject of this thread weigh 167g and lasted five years @ ca. 1100 Watts .

.
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Old Sep 02, 2008, 10:00 PM
Hey Now
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Hey guys-I posted awhile back about having cracks in my Midi fan housings. I actually have 2 of them sitting here on my computer desk that have cracks along the screw holes. One is really bad and the other one is cracked but the cracks don't show up in pictures. I had another shroud that was cracked but I threw it away.

I also have an aluminum spinner that I can't get off the rotor for the life of me. I really want to inspect the motor mount but the spinner just won't come off!!!!

Here is the badly cracked one from the front and the back. From the back it is pretty much trashed and I think I got lucky nothing happened in flight. The last flight I noticed a noise. I landed and quit for the day, went home and this is what I found.....

These fans were used at 1000-1500 watts with Mega 22/30/3, 8s.


Scott
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Old Sep 03, 2008, 09:11 AM
Julian T
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Would heating the spinner with a heat gun get it hot enough to expand slightly and reduce the release force required?

Julian
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Old Sep 03, 2008, 09:31 AM
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Hi Herb

Daniel's calc does allow for Lehner publishing loaded Kvs when other makes publish unloaded ones. You're right of course about the Lehner calc being for environments with less cooling.

After de-magging a motor in the Schubi in my Bandito I took off the Schubi tailcone and scalloped out the motor tube in the same fashion as seen in the Midifan pic below. I noticed no change in model peformance, but never demagged a motor in that plane again, even after converting from short flights on GP3300s to long and even more energetic flights on 6200 Lipos. So when my Lehner goes inside the Vector, the Schubi will have been modded the same way.

The FUN600 that's in there already hasn't needed this drastic motor tube mod and has the tailcone still on there. So I do echo your confidence in the FUN600.

Oops! Better let you get back on topic Herb

Cheers

Gordon
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Old Sep 03, 2008, 12:18 PM
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Quote:
Originally Posted by juliant
Would heating the spinner with a heat gun get it hot enough to expand slightly and reduce the release force required?
Yes, definitely for the aluminum hub (which is generally for good reason a tight fit).

For the spinner you could run the risk of melting or softening parts of the rotor, so you have to be careful.

Scott, yours seems worse than mine. I think you need a replacement. It is crucial though that you support the back of the motor with masking tape as I do to reduce vibration.

As a general note, this thread should not be considered as a criticism but instead as a tribute to an outstanding design, which has by far outlasted any predictions. The WeMoTec Midi was originally sold, for what, 600W max brushed motors ?

.
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Old Sep 03, 2008, 12:27 PM
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Yup the fans last a long time and work like a charm

In my earlier post a year or so ago I think there was some ideas that thread lock would damage the plastic. Is there any further info on this?

Yes, my motors are supported in the rear to reduce chances of damage.


Scott
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Old Sep 03, 2008, 12:32 PM
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Yes I think some threadlocks eat at the plastic. It is possible that some do not; I use a generous amount of GE Silicone II to lock the screws in place.
The threadlock can still be used where the bolts go into the motor I suppose.
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Old Sep 03, 2008, 12:52 PM
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Incidentally I am switching the Rafale over to a Futaba Fasst 2.4GHz reciever, as there's a guy at my field who occasionally flies his Multiplex MiniMag on my channel . He's very nice and all but you never know.

To those who do not think that regular FM can ever work in an edf, all I can say that this Rafale has flown five years glitch free on a Hitec superslim 8ch rec. with separate Sanyo 820mAh 4-cell rec. battery.

.
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Old Sep 04, 2008, 02:05 AM
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Herbs going 2.4!
I'll have to check out your setup.
Been planning to switch my 9CAP over to spread spectrum for some time now.
Bruce
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Old Sep 04, 2008, 04:03 AM
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heck i still have 90m stuff flying for almost a decade on 555 or upgraded 4-5 years ago to electron6. You know tinfoil isnt just for cooking!


Barry
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Old Sep 04, 2008, 11:43 AM
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Quote:
Originally Posted by bmiller
Herb is going 2.4. I'll have to check out your setup...
Yeah since May ... you need to come to the field more often

At $100 a pop conversion of my edf fleet to Futaba Fasst 617's is going a bit slowly ...

.
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Old Sep 06, 2008, 08:40 PM
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From the sound of it today at the field, Your Rafale is ready for another 5 years worth of flying! Very smooth sounding fans.
Yup the price of converting all my stuff to 2.4 is intimidating.):
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Old Sep 07, 2008, 02:30 PM
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I finally had one short flight of the Rafale with the new setup - sweet

After the flight, and then after a second test run on the ground, I looked at i) esc temp, ii) wiring & connector temp iii) battery temp and all seemed within the safety zone.
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Old Sep 20, 2008, 10:54 PM
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how about this one :http://www.rclander.com/default.aspx...e-34c88306a5f6
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Old Sep 21, 2008, 01:30 PM
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For the upgrade I put two large Hacker Master 77 esc's in the Rafale, with large heatsinks, and they work very well. They barely get warm after a mixed throttle flight, which was not the case of the old setup (twin Hacker Master 70)...

.
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Old Sep 21, 2008, 01:44 PM
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We also tested some of the new Hobbycity chinese low cost LiPos, for possible use in high powered 90mm edfs.

So once more we wanted to put the hype to the test.

The one pictured below is a Hobbycity Hext G3 20-32C LiPo, its unit cost (2.2Ah) was around $32 delivered.

It lasted 26 flights at < 20C , then the middle cell plastic casing started to bubble. It is actually reasonably well assembled, it's just that chinese cells still seem far behind the korean ones in quality and endurance.

At $32 unit cost, that's around $1.2 per flight. On a Kokam, FP evo or TP LiPo pack at twice the price and twice the quality/duration, the unit cost is comparable (plus the far better service).

In the end you still get what you pay for

.
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Old Sep 25, 2008, 01:37 PM
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Quote:
Originally Posted by Gordon
... You had me reaching my similarly aged Vector II down from the workshop wall to check the DS51 blades. They are somewhat pitted...

I took out the DS-30 and the blades, after three years of flying, are slightly pitted too ... The main problem I've had on the DS fan is the stators coming unglued from the shroud possibly due to motor (B50L) vibration at very high rpm. A bit of laminating epoxy seems to have solved the problem.

.
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Old Sep 25, 2008, 04:22 PM
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Quote:
Originally Posted by Herb
The main problem I've had on the DS fan is the stators coming unglued from the shroud
I had a stator come loose on the Vector's fan a long time back. I put it down to the unit suffering severe jarring due to some rather heavy landings flipping the plane inverted, as the FUN600 has always been vibration-free. I glued it back with CA, with no further trouble ... maybe my landings have been better since then

Gordon
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Old Sep 25, 2008, 06:18 PM
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This was a nice report, Herb.

Overhauling my 5 to 7 year old EDF-Jets is just dusting them off.

...and trying to make friends with LiPo's which is difficult. But I am hell-bent to fly electric jets again.

Michael
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Old Sep 26, 2008, 11:01 AM
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Dusting them off ??!!

Well mine often need new paint and esp. new decals, which regularly fade in no time in the CA sun ...
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Old Sep 26, 2008, 01:12 PM
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Yes there is (no: WAS) lots of dust on them as they were stored in the cellar. The interesting thing I found out today is that the cabin of my unbuilt Schreiner Albatros has become extremely brittle on one half. Maybe too much UV radiation in my cellar. Have to investigate this.

Did nothing at all with my Jets the last 4.5 or 5 years due to some private and job issues.

But I will be back. Hope you still know me Herb.
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Old Sep 28, 2008, 01:14 PM
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Originally Posted by MichaK
... Hope you still know me Herb.
Yes Time to get that sensational L-39 in the air ...

Herr Schreiner never quite got a world-wide distribution worked out, as Savex for ex did It is a pity.
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Old Nov 18, 2008, 04:07 PM
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Quote:
Originally Posted by speleopower
... Yes, my motors are supported in the rear to reduce chances of damage.
It is absolutely crucial that the motor be well supported in the back to avoid cracking the Midifan plastic shroud at the bolt location as shown
here: http://www.rcgroups.com/forums/showp...99&postcount=6

The above rear support issue is clearly a major obstacle in mounting an un-supported outrunner in the Midi : the front bolts won't prevent the motor from eventually vibrating at the back - which is likely to eventually crack and rip the shroud apart ...

It looks like the new Nue 1415 (thin case) motor is a very nice low cost high performance solution for the Midi fan - need to get one myself one of these days ...
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Old Nov 18, 2008, 07:21 PM
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Herb:

How much for that motor? Where can I find specs?
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Old Nov 18, 2008, 07:32 PM
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I don't see it listed on the Neumotors web page yet but it should be soon?

http://www.neumotors.com/2008/Root/S...0_series_.html

The price should be comparable to the 1515 series which I think is $255. It is basically a thin case machined down 1515 which now fits in the WeMotec MidiFan.

The efficiency should around 90+ % as the other comparable Nue motors ... that's ca. 1800 shaft Watts on 2000W in .

Not sure if he plans on having also a 1512 and 1509 "thin case" (which would be a bit lighter, thus perhaps more suitable for lower power setups).
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Old Nov 26, 2008, 11:56 AM
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Another possibility is to have the WeMotec MidiFan shroud machined down to hold the regular 1515 series motors, which according to the web page have a diameter of 1.53'' = 38.86 mm.

The inner diameter of the WeMotec Midifan is 37.50 mm, which means about 0.68mm has to be machined out of the shroud.

.
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Old Nov 26, 2008, 12:02 PM
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I did this already once. The guy at our machine shop had to custom-fabricate a solid aluminum holder, in order to machine out precisely a given amount of material.

Not sure though how the old 1406 (so called cuisinart) diameters compares to the new 1515. The machined out fan shown below works fine to this day ...

.
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Old Nov 26, 2008, 12:04 PM
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Nice to have friends like that Herb!
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Old Apr 10, 2009, 12:25 PM
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Another possible source of repair work is dented blades, from a variety of reasons including sucking in dirt and stones. In the first picture the cause was a shredded (older design) spinner. Yes I still do fly fans that are more than six years old

Here I used some epoxy to fix various dings and dents,

.
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Old May 20, 2009, 11:21 AM
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Just in case, I got my replacement WeMoTec Midifans (now the pro version which is pre-balanced)

.
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Old May 20, 2009, 01:55 PM
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when will wemotec release the new Midifan V2 then?

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Old May 20, 2009, 05:01 PM
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Natural development ... but I am told it will be a while

I think 100mm and 75mm wemotec fans for 36mm motors would be desirable.
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Old Jun 09, 2009, 11:26 AM
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... the new MidiFans Pro fans have now been installed in the black Rafale, they run very smooth with a slight resonance between the two at ca. half throttle.

The first flight this past weekend was uneventful, and the motors came down pretty cool.

.
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Old Jun 09, 2009, 11:50 AM
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Herb:

Are those Turnigy inrunners? What kind of numbers are you getting?
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Old Jun 09, 2009, 11:53 AM
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On the MidiFan Pro one does not need to cut a slot in the adapter, a hole is already pre-drilled.

The green stuff is rotor balance putty.

.
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Old Jun 09, 2009, 11:55 AM
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Quote:
Originally Posted by Socomon
Herb:

Are those Turnigy inrunners? What kind of numbers are you getting?
Yes, BL36 , kv=1800 and 2300. 27 flights so far @ 1700W:

http://www.rcgroups.com/forums/showt...page=12&pp=100

They perform - so far - better than Mega 30 and Kontronic Fun 500 combined.
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Old Jun 09, 2009, 12:06 PM
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My Midi Pro adaptor had no pre-drilled hole. I bought it about 8 months ago! Must be a new thing.
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Old Jun 09, 2009, 12:09 PM
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Pretty impressive for the price. It would be nice of they had a 1600kv version for 6s midi fan set-up.
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Old Jun 09, 2009, 12:26 PM
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6S : http://www.rcgroups.com/forums/showp...&postcount=883
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Old Jun 09, 2009, 12:37 PM
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Hmmm . . . those numbers (watts) are about what I get from the 1600kv medusa on 7s. The amps are kinda high, but you are carrying around one less cell I guess.
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Old Jun 09, 2009, 02:02 PM
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... The Watts and Amps on mine are exactly what you expect based on the published motor constants (kv, Io, Rm).

And the efficiency is high as well. Since when can you have Watts without Amps ?
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Old Jun 09, 2009, 02:35 PM
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I understand that and probably did not explain what I meant well.

I was just weighing the trade-off of using a lower kv motor at higher volts and less amps (at the expense of carrying another cell) versus going lower cell count and higher amps on the higher kv motor.
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Old Jun 09, 2009, 09:01 PM
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You can, as always, do both.

It makes no difference, what counts as far as power is Watts (more appropriately, shaft Watts, which takes motor efficiency into account).

You can use a high cell count with lower amps. Or use a lower cell count with higher amps. The result in the end is the same. The battery has to be sized accordingly, and in the end, for the same amount of power, you will have to carry the same battery weight. More amps means higher battery capacity (a fact often overlooked in inefficient amp hog motors).

The new point about these HC motor is I think the availability of many different winds (because they are 2-pole).

So the motor can be tailored to the fan & cell setup (and possibly esc). And different fan setups can be experimented with without dishing out $$$ for a state of the art motor.

In the end, if you want ultimate performance and reliability at very high power levels this is probably not the motor to use.
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Old Jun 09, 2009, 09:12 PM
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Quote:
Originally Posted by 172AMD
My Midi Pro adaptor had no pre-drilled hole. I bought it about 8 months ago! Must be a new thing.
Yes it is . Now you don't have to cut a slot in the adapter.
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Old Jun 10, 2009, 11:19 AM
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Here's an example of what to expect on the 6S setup for the 1800kv motor, it closely matches the figures I measure in the Rafale setup:

It's clear that these motors are best suited for a twin setup, where the cost of two DS-51 fans & two Neu 15xx motors would be quite steep , although the efficiency would be a bit higher. Maybe next year

.
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Old Jun 10, 2009, 01:00 PM
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I know this is off topic. Quick question for Herb. Have you done any testing with the MEGA 16/35/1 in the minifan or het fan yet?
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Old Jun 10, 2009, 01:03 PM
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Quote:
Originally Posted by Herb
It's clear that these motors are best suited for a twin setup, where the cost of two DS-51 fans & two Neu 15xx motors would be quite steep .
The cost of one Schubie and a Neu is plenty steep enough to justify it for us 9-to-5ers.
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Old Jun 10, 2009, 01:18 PM
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Quote:
Originally Posted by tho98027
I know this is off topic. Quick question for Herb. Have you done any testing with the MEGA 16/35/1 in the minifan or het fan yet?
No not me - But it seems some have done so in pylons, and claim it's good to 120A in bursts.

Mega has a very good track record in producing quality motors.

Cooling, rigid mounting and a quality balanced fan is of the essence.

http://www.rcgroups.com/forums/showthread.php?t=991130

http://www.rc-network.de/forum/showthread.php?p=1074276
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