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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Mike Scholtes on February 27, 2011, 07:01:42 PM
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Bob Hunt is using E-Flite motors in his new Twin, so they must be good. Anyone have experience with the E-Flite Power 25 or Power 32 motors, which by the specs look like the most appropriate for our purposes? I think Bob commented that the Power 25 compares to the Axi 2826-10, very similar specs. Given E-Flite's experience in electric power I have to think their motors would be first rate, but they are not built with Stunt in mind. Anyone here actually using one in a plane?
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Well, Mike ...
None of 'em are designed with Stunt in mind, and this is what we have been battling on and off for a while now.
Our abrupt corners stress these outrunners mechanically in ways that most E-folk do not. The Pattern guys share this problem, too.
The jury is still out on the Power 10's though we do not expect any unusual issues.
later,
Dean
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Mike,
I have been using the power 32 and 25 with success. I would suggest front mounting for both, I have done both front and backplate mounting and agree with Dean on the stress issues of rear mounting. The 32 is more stable than the 25 but both suffer from bearing stress. I have two seasons on one 32 that has been rear mounted and it has been working well, but if I were to do it again, I would definitely front mount it.
I am running APC 12-6 on the 25 and 13-4.5 on the 32's. The KV of the 32 at 700 is marginal with the 13-4.5. It works for my application but I suggest a 5S to make sure you have the reserve rrr's you will need.
Let me know if you have any other questions
Tim
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It's easy enough to twist some more pitch into that 13 x 4.5!
Dean
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Personally, I am NOT comfortable twisting props (I know people do it all the time) so for simpletons like me, APC also makes a 13x6.5P that likes to fly (as I recall) around 7800 - 8000. That would make it a cinch on that 700 kv & 4S.
Forgot to mention, I have a E-Flite 15 (shorter than the ones Mike is looking at) but it is built like a brick sh__ house and runs smooth. I would be perfectly comfortable with any of the E-Flites.
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Thanks guys. I also got a pm from a local stunt flyer and excellent builder who has been using the Power 25 for several seasons and reports no troubles at all. As soon as I posted my query I realized "Nobody builds e-motors for stunt, come to think of it." I believe Rudy Taube has pointed out that 3-D RC flyers put stresses on their models that exceed anything we do in stunt (not counting crashes I suppose), with no problems on front or rear mounted motors. But I do see the mechanical benefit of front mounting and the stress reduction that would result.
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Dean,
Rudy provided me with his pitch gauge just for this purpose. Have not had a chance to play with it yet......Darn Work Traveling HB~>. I still need to figure out how to reverse it for pusher props, I assume it will be easy, just have not looked into it yet.
Tim
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None of 'em are designed with Stunt in mind, and this is what we have been battling on and off for a while now.
Our abrupt corners stress these outrunners mechanically in ways that most E-folk do not. The Pattern guys share this problem, too.
Dean
Good Morning, Dean
Do you know of actual mechanical (bearings, I suppose) problems caused by p-effect/precession forces in Pattern and/or 3D airplanes? Or C/L stunters, of course?
rgds, Peter Germann
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Hi Peter,
If I understand, you are asking me to count the many ways that aerobatic flight seeks to tear an outrunner apart, right?
Okay, it beats asking the poetic question of how many ways I love electric ... let me count the ways: that we tear outrunners apart, that is.
For one thing, the "bell" is just that, and it rings and distorts under load.
In extreme cases, the armature scuff is obvious from inspection of the magnets and the end of the winding pole material.
Another contributor to this armature scuff is the flexibility of the bearing mounts.
The bearing in the fixed end of the motor is usually bigger and better supported. (This is a large part of why front-mounting is a good idea)
The bearing at the crown of the bell (the prop mounting end in firewall mounted installations) is supported by a center pylon/tube.
This tubular center pylon is not overly large because its diameter steals from copper winding room inside the motor and if enlarged it would also force the magnetic path through the stator iron to be longer.
Both these compromises improve the efficiency at the expense of rigidity. For these reasons, the pylon is small and thin walled.
Extreme loads wiggle the pylon and combined with bending of the motor shaft, this will tend to wiggle the bearing at the end of the center pylon in its mounting until it loosens.
Gyroscopic loads are the worst because any bending is then turned into a wobble by GP.
You can easily imagine this wobble walking the bearings out of their press-in seats and loosening anything it can.
In addition, the "bell" has a resonant frequency, and when either the commutation frequency or the RPM match that resonance, then awful things happen.
Nobody talks about this, but the folks at AXI were actually quite forthcoming and discussed the issue with Igor regarding the 2826 chassis.
They said that the 2826 would resonate around 12,000 RPM.
Maybe that's why Bob and I were going through them very early on back when we ran ungoverned at full throttle and 11,500 RPM HB~>
I hope that's at least part of what you were looking for.
Regards,
Dean
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Hi Mike,
E-Flite MOTORS = :-)
As others have said, you should have no problems with the E-Flite motors.
I use mostly Hacker motors, from my little foamies to my 17 lb. planes. But I do have 4 E-Flite motors and I like them. I fly my multiplex Acro Master at my local park (2 blocks away). It weighs 34 oz. and uses the excellent E-Flite 10 with an APC 12 x 6 on Hyperion 3S2200 batteries. I only have about 250 flights on this plane but I am always amazed at the power from this little 10. My plane will go straight up after launch doing rolls OOS. This is one powerful little motor.
FORWARD vs REWARD MOUNT
The above E-Flite 10 is FORWARD mounted and it works well. I have another E-Flite, the 480 in another forward mounted installation, and two other Hackers in a front mount. They all seem to work OK. But my other 6 electric planes are rear mounted, and they seem to be OK too. I have the E-Flite 110 REAR mounted with no problems.
Most of the guys at our large E flying field have their motors rear mounted. Some of these get stressed to the limits and they still work. I have to admit that I have not gathered any real data (# of flights before failure, etc.) from others, but I have not heard of any bearing problems with name brand motors. The turnigy motors are the only ones that seem to have problems. Some fail early (bearings and throwing magnets), but some seem to have a reasonable life span and perform OK.
I like to look to the Pattern guys for the LE in technology and way cool installation stuff. At the AMA Expo here in LA there was a drop dead gorges Pattern plane on display. It had a Hacker motor FORWARD mounted. They said they really put the nose ring/MM in SOLID with a lot of CF reinforcement. It was a beautiful install. They had a large CF spinner with long (about 1 1/2" x 3/16") curved slots cut out all around the spinner. I think there were about 5 of these cutouts. The curves looked like they were well thought out and looked like they would scoop up the air and force it through the very cut out backplate into the motor. The gaps around the prop were very small so the air had nowhere else to go but into the motor for cooling. They said they tested the motor temps before and after this slot mod. It dropped the motor temps by 25 f. I thought this was a way cool solution. :-) I wish I had my camera there, a photo would be nice here. Maybe Dean can help us here. ..... BTW, these guys told me Pattern has really gone to E power. So if anyone wants a nice big powerful supercharged YS engine, I'll bet you could get one cheap! ;-)
Below is a photo of my E-Flite 10 powered, 34 oz. Acro Master.
PS: I wrote this while Dean was posting. My reply above is not to Dean's post. ... The reply below is. ;-)
Hi Yoda, (AKA Dean :-)
Yikes! What were you guys doing up at 11,500 RPM? That's down right cruel to our little motors. ;-) You guys just have to get away from your WET "no pitch" props. Maybe this is why we don't see as many motor problems in ERC? We use larger pitch props and keep the RPMs down. 12 x 6, 14 x 7, 17 x 12, etc.
Regards,
Rudy
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Hi Peter,
If I understand, you are asking me to count the many ways that aerobatic flight seeks to tear an outrunner apart, right?
....
I hope that's at least part of what you were looking for.
Regards,
Dean
Thank you very much for that detailed insight, Dean.
I have chosen to rear-mount the motor for two reasons:
- Simpler design allowing generous airflow.
- Following advice from friend and former Pattern World Champ Wolfgang Matt stating "I've never had a problem with rear mounted motors"
Perhaps I am over-pragmatic, but for me it all comes down to practical testing where time will tell how many flights I will get from the rear-mounted 2826/12 turning at 9'700 RPM.
Again, thanks for explaining, rgds. Peter G.
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Hello Peter,
I suspect that you'll be alright, but if you do have issues, they will happen between 75 and 100 flights; and that is what Bob and i saw two times after dropping into the nine-thousands after "going governed".
Now, i thought that Wolfgang was running either the geared hacker C50 or the new "Q" series outrunner. In any case, if he was running the 60S or 60M series hacker outrunners, it is important to note that they have the third, big-diameter, bearing at the circumference of the bell. This makes a big difference, as it prevents much of the center pylon bend and shaft bend!
In any case, it makes sense that Wolfgang had no problems. Stunt is way more violent to the motor than almost any 3-D ... and I realize that could be argued. 300+ degrees per second pitch rate at running RPM is the culprit.
Please give Wolfgang my regards.
Hi Rudy,
I did say that we ran those RPMs before we figured out how to run on the governor, so that was at full throttle. No ... throttling back was not an option. S?P
take care,
Dean P.
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I did say that we ran those RPMs before we figured out how to run on the governor, so that was at full throttle.
take care,
Dean P.
Hi Dean,
You probably posted this info somewhere. I would appreciate it if you could point me in that direction.
Thanks,
Phil
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Guys,
I'm looking at the E-flite 32 vs 25 to replace an AXI 2826_10 in a 62oz ship and wondering if there is any significant disadvantage to the 2 bearing set up in the 32? I like the idea of the lower Kv motor to get me a little higher in governor range, I like to run around 9200. I see it was recommended for a couple ships but that was a while back, any new thought before I buy this motor?
Best, DennisT