Thread Tools
Oct 20, 2003, 09:15 PM
Registered User

Does anybody have any experience with the Mega 16/25/xx series

Hey there,

I am thinking of buying a 16/25/4 or a 16/25/6 (more likely the 16/25/6) for my warmliner 150cm wingspan o/d glider, with a 10 x 6 or a 11 x 7 prop. The think is that since that these b/less motors are quite new I am having trouble finding people that are using these motors yet.

With the 16/25/6 it's Kv is 900 rpm/volt. Does this mean that you can put more cells in the pack before you get the the motors exceptable rev limit???

Basically I have been told that the 16/25/6 is better at turning the 10 x 6 / 11 x 7 props than the 16/25/4, but the 16/25/6's max amps are only 18 amps with the 11 x 7 prop. That's ok I guess but one other question that I need to ask is that if I run a 11 x 7 prop on the 16/25/6 at about 18 amps then am I running at the max efficiency (about 86% I believe). Then this would be good right, and thus the best motor for my application. I am looking for a climb with authority NOT ballistic vertical climbs in 3 seconds.

Thanks for any advice guys,

Sign up now
to remove ads between posts
Oct 20, 2003, 10:31 PM
high-speed freak
opualuan's Avatar
for a glider, something like a 3t mega with maxon 4.4:1 would do well turning a large prop... I'd go geared.
Oct 24, 2003, 11:36 PM
Registered User

Yes BUT...... I need advice about this motor NOT alternatives


Thanks for the advice, but it's not really what I needed. I have looked at the 16/15/3 with a Maxon g/box BUT I prefer to not use a gearbox HENCE my reason for the Sp480 size 16/25/xx Mega preference.

Using a 16/25/xx is about the same weight as a 16/15/3 with gearbox BUT a tad shorter and DEFINATELY cheaper.

Any advice about the Kv's though. Can I use more cells with a lower Kv??? And will my efficency be at it max if I get the motor up to it's max amps???

Oct 25, 2003, 12:56 AM
Permanently Banned
Larry3215's Avatar
I too have been considering this motor. Waiting for replies from actual users.

Oct 25, 2003, 03:54 AM
sloping addict
Protocooler's Avatar
assuming your complete plane w/o motor / ESC and battery weights 700g, and using Snayo HR 4/5 A cells (about the best for 20-30A) - Motocalc says:

16/25/6 DD would have to work over its amp rating and with a small prop. One setup that should work OK since you're only using throttle for 10-30 sec and losses are still low @ 37W could be:
8 cells, 9*5 Cam folder, 35A, 2:54" est runtime (less in practice), 45 climb rate at 7.8m/s, Motor eff 86.6%

Not too good, the prop sounds still too big for th emotor. A geared setup is much better, or try an Outrunner to get the biggest possible prop (12*7 would be good target) w/o raising amps too much...

I first wanted no GB, but finally chose the 16/25/3 + 4.4:1, as nothing comes close enough at full throttle for climbing efficiently. Still waiting to receive the motor....

Here you have many examples of outrunners use that will help:

Oct 26, 2003, 02:33 AM
Registered User

Hmmmmm, interesting.......

Thank you to all for the advice,

I am thinking that I might be best to go with my original idea with the 16/15/3 with a gearbox. Originally I looked at a maxon gearbox (in the ratio 3.3:1) with the 11 x 7 (my largest prop).

Is this ratio the best to get or should I go to the 3.8:1 or the 4.4:1???

My reason not to go with a gearbox, was that I might have to add an extra bulkhead at the back of the motor for support. This is what I was told by one member at my club, and also that I will lose out a bit of the efficiency with a gearbox. What do you think??? Is this true?

Oct 26, 2003, 03:20 AM
It's a Great Day to Fly
LenBFP's Avatar
There is the mechanical losses in a gearbox, but typically the motor is being moved into a more efficient operating range for it.

I love the outrunners.

At 78 grams is the AXI 2808/24 driving an Aero Naut carbon folder 10 x 6 on 8 1100 mah 2/3 A cells I measured my motor at 7500 rpm 7.8 volts 15 amps. It should be about 80% efficient here.

Last edited by LenBFP; Oct 26, 2003 at 03:59 AM.
Oct 27, 2003, 11:03 PM
Registered User

The outrunners sound good too BUT ....


I would consider the outrunner type b/less in my larger e gliders 2.5m +, BUT with this model of mine the nose front is only 32mm in diametre, and I believe that most outrunners are usually bigger in diametre to able to afford a better torque than the usually b/less motors. BUT correct me if I am wrong as I haven't really researched the outrunners that much (just what I've read in magazines such as Q & EFI).

Thanks for the suggestion.

Is though the 16/15/3 with a 3.3:1 or a 4.4:1 the best route to take without going outrunner? What is the best gear ratio for this motor with a 11 x 7 or a 10 x 6 prop???

Oct 28, 2003, 12:30 AM
Permanently Banned
Larry3215's Avatar
Have you checked out the Mega USA site? They have some data on different props for all the motors. The 16/25 series is a bigger/more powerfull motor than the 16/15 series.

For the 16/25/6 see...

It would seem that no one has any actual experience with this motor yet. The 16/25 series just came out recently.

Good luck!

Oct 28, 2003, 03:12 AM
Registered User
vintage1's Avatar

Re: The outrunners sound good too BUT ....

Originally posted by Masterpiece

Is though the 16/15/3 with a 3.3:1 or a 4.4:1 the best route to take without going outrunner? What is the best gear ratio for this motor with a 11 x 7 or a 10 x 6 prop???

If you mean 16/15/3 and not 16/25/3 then your ratios and props are IMHO close to ideal

Maybe a little more diameter and a little less pitch - 11x5 or whatever?
Oct 28, 2003, 03:23 AM
high-speed freak
opualuan's Avatar
for a 10x6, you might also consider a 16/15/2 4.4:1. should be right near it's max output on 10 cells. I run this on 3s lithium on a 9.5x7 at 28A, motor spec'd for 31A max continuous. I like maxing out my motors. for burst application (glider LMR) you could even prop higher.

I'd pick a 16/15/2 4.4 over a 16/15/3 3.3 because of the gearbox. I really like the maxon 4.4:1. much quiter than other boxes I've tried.
Oct 28, 2003, 06:55 AM
sloping addict
Protocooler's Avatar
if you look at the other threads, you'll see I just got a 16/25/3 with the Maxxon gearbox. The Maxxon looks very good and is supposed to hold up to 700W. I haven't tried it yet.
However this setup requires a very big prop (17") and many cells (12-14) or you'll get poor results / stalled prop. My setup will yield to ~400-450 W for 1.5 kg AUW.
The real "hot" liners will request about 700W+ for same weight but heat losses are 4 times as much for a minimal gain (12/13 m/s raising to 16 m/s climb rate), not useful IMHO for leisure use, especially as every component in their power train is strained a lot (batteries will be trash after a few dozen flights at most)

The 16-25-6 route will lead to a small prop (8", maybe 9") and will not be a very good setup for a LMR.

I would agree with 16-15-2 recommendation, rated 38A. Don't exceed about 10 cells if you don't want to take a risk of throwing a magnet (40000 max rated RPM although some report OK at 70k) as kV is 4600. Then gear it deeply for most efficiency, Maxon 4.4:1, or even better, Reisenauer Micro-edition 5.2:1 and you'll have a winner. However this will only be a winner in relation with Sanyo 4/5 FAUP cells (7 to 10), nothing else will deliver the amps / voltage properly otherwise (bar a lot of Lipos in //). Prop that for 35-40A.
Maybe 13*11 depending on #cells (guessing there).

drawback: you'll get the performance but that costs ! You have the wallet, you choose
Oct 28, 2003, 12:27 PM
high-speed freak
opualuan's Avatar
ken of megamotorsusa said 31A continuous, 45,000 rpm. are you quoting burst current? I can understand it for LMR usage.... just wondering. the /2 gets pretty warm at 30A on the ground, I think 38A would be getting pretty inefficient.
Oct 28, 2003, 02:06 PM
sloping addict
Protocooler's Avatar
Well, not sure what MEGA states exactly, the info was taken from Aircraft-world... I have a MEGA datasheet (coming with my motor) and 16-15-2 is the only one NOT listed !...

Anyway, here is an efficiency curve (for Mega 16-25-3, rated 30/50A), not taking into account heat effects. I'm not sure how accurate it is, and anyway I would not rely on it for a non LMR / non geared setup.
But you will note that Motor eff. is within about a 2% range for a very wide range of input Amps, in LMR use you *should be able* to use motor above its rating w/o decreasing efficieny (actually the overall powertrain eff. will increase). The factors to look at are RPM, and that the power runs are short enough to avoid heating effects.
Oct 30, 2003, 11:04 AM
Balsa Flies Better!
Ever hear the expression - 6 on one, half a dozen on the other? If you're getting advice from Ken he's generally not far off- nor are the spec sheets on these motors- I'd take them over Motocalc.

A couple of things- making certain of your batteries and optimizing prop for airframe generally beats worrying about a couple of percent of motor efficiency. I like DD solutions a lot, and since you're not looking for ultimate performance, you'll probably be happy. One thing though- max rated current and max efficiency are generally two different numbers- and how heavy is this glider anyway? Why not just run watts/ lb (at least 100 or more) and check the pitch speed with the rpm you want.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Does anyone have any experience with the "Jabo" brand heli? ben1101 Micro Helis 2 Dec 08, 2006 04:20 PM
Question Does anyone have any experience with the new Hacker outrunners? viva_peru Power Systems 4 Dec 09, 2005 03:53 PM
anybody have any experience with OS film? may-day Scratchbuilt Indoor and Micro Models 5 May 28, 2005 08:36 AM
Does anyone have any experience with randall1959 Parkflyers 16 Mar 27, 2004 05:24 AM
Question anybody have any experience with these chargers? asjeep Batteries and Chargers 4 Feb 12, 2004 12:59 PM