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Electric Stunt => Gettin all AMP'ed up! => Topic started by: RC Storick on May 11, 2013, 11:37:04 PM

Title: Motors?
Post by: RC Storick on May 11, 2013, 11:37:04 PM: Will in runers work and if not why not?
Title: Re: Motors?
Post by: linheart smith on May 12, 2013, 09:06:10 AM: 1. KV to high
2. RPM to high
3. Less torque
4. No brake (due to no iron magnets.)
5. Usually run with gears

Linheart
Title: Re: Motors?
Post by: RC Storick on May 12, 2013, 11:37:23 AM: Quote from: linheart smith on May 12, 2013, 09:06:10 AM
1. KV to high
2. RPM to high
3. Less torque
4. No brake (due to no iron magnets.)
5. Usually run with gears
Linheart

http://www.hobbyking.com/hobbyking/store/__9449__Turnigy_540L_V_Spec_Inrunner_w_Impeller_810kv.html

(http://www.hobbyking.com/hobbyking/store/catalog/D480S-3200(1).jpg)

Just wondering
Title: Re: Motors?
Post by: Dan Bregar on May 12, 2013, 01:07:58 PM: Quote from: linheart smith on May 12, 2013, 09:06:10 AM
1. KV to high
2. RPM to high
3. Less torque
4. No brake (due to no iron magnets.)
5. Usually run with gears

Linheart

Yeah, but other than that they are fine ! :##
Title: Re: Motors?
Post by: Tim Wescott on May 12, 2013, 01:20:39 PM: 4: All the inrunners that I know about do have iron magnets, it's just that the cogging torque (which is, I believe, what you're calling braking) is in general lowered right along with the running torque.

Edit, May 13: Inrunners used for model airplanes, that is. There are industrial servo motors that have no moving iron, but those are used when you need precise torque and low inertia, not when you need lots of power in a small space.
Title: Re: Motors?
Post by: jim welch on May 12, 2013, 07:27:15 PM: I think Mike Palko's airplane is an inrunner and it seems to be a pretty competitive set up. Jim
Title: Re: Motors?
Post by: Dean Pappas on May 13, 2013, 12:09:49 PM: Hi Sparky, Hi Gang,
Linheart laid out the reasons generally given, but ...

There are low KV inrunners like the Neu 1900 series. There are two suitable motors in the Neu 1900 (a.k.a. ORK for OutRunner Killer) series; the 1905-2.5Y has a KV of 865 (4 cell) and the 1905-3Y has a KV of 720 (5 cell) and both weigh 6 1/2 ounces. They are probably right for your high 50's / low 60's ounce ships.
There are also the MVVS hybrid in/out-runners which use an outrunner armature running inside a case ala inrunner. There is s small weight penalty, but they work very well for some folks.

On the other hand, I am quite convinced that a geared/belted high RPM inrunner will have tremendous advantages in efficiency, load-change response speed, and braking if only the gearbox longevity problems can be overcome. Dennis and Archie tried a geared motor and were very impressed right up until the motor spit all the gear teeth back at them ... Ptooooey!

take care,
Dean
Title: Re: Motors?
Post by: Dan Bregar on May 13, 2013, 07:33:07 PM: Yes Dean, if gearboxes/reduction drives were not so problematic then certainly they have advantages. Except for the additional weight penalty, which of course in not an advantage. Out-runners have me spoiled. ;)
Title: Re: Motors?
Post by: Dean Pappas on May 13, 2013, 08:39:31 PM: Hi Dan,
in the Pattern world, the geared inrunners actually have the slight weight advantage. VD~

Dean
Title: Re: Motors?
Post by: Andrew Borgogna on May 13, 2013, 10:23:55 PM: Dean
Instead of a gear drive why not a belt drive similar to what Byron first put in their Pitts Special a couple of decades ago. They tied a 21K RPM piped Rossi .60 to a 3 to 1 belt drive and turned 18x6 props around 6-7K. They worked great until the Quadra gas engines relegated them to the boneyard. If I remember right the "Byrodrive" had two V belts connecting a pair of pulleys running in tandem between the engine and the prop. A miniature version of this could be built for stunt applications, at least I think it could.
Andy
Title: Re: Motors?
Post by: Mark Scarborough on May 13, 2013, 11:12:36 PM: It would seem to me that a belt drive system would generate some issues, mass for one,, building something to align the belts reliably that did not weigh much but was structurally sound..... then trying to maintain enough friction on the belts so they dont slip,,, then trying to accelerate all that mass in some manner so that it can respond to loads promptly,,
I think it would be challenging just mechanically but it could be,,
In my uneducated view it would be very difficult to compete economically or performance wise with a gear box

just an observation,,
as to inrunners,a freind had one of the ORK inrunners and it seemed powerful for its size but I never flew it on anything.
Title: Re: Motors?
Post by: Dennis Adamisin on May 14, 2013, 04:57:13 AM: As Dean said we had an Astro motor running through a 3.29:1 gearbox. That meant the motor was running around 33k to deliver 10k to the prop. Using the reubualr programming for Phoenix it was a cinch to set-up - the only difference was filling in the drive ratio where it asks.

Worked great for 10 flights til the pinion wore a perfect groove through the idler gear. Speculation is that it might work better with one metal and one delrin gear similar to Heli proctices. If I ever try these again it would be driving through belts.

My brother tried some of the Turnigy ORKs, quickly burned them up then reverted to outrunners for a power-up at less weight.

Outrunners outperfrom inrunners or ORKs because the power is being generated at nearly the outermost shell of the motor, so the torque is superior to a motor where the power is being generated closer to the diameter of the shaft. Put another way, a belt drive driven by high kv heli-outrunner would be awfully strong.

Let me know how it works out for you...
Title: Re: Motors?
Post by: Doug Moon on May 14, 2013, 10:28:26 AM: Quote from: Dennis Adamisin on May 14, 2013, 04:57:13 AM
.....Put another way, a belt drive driven by high kv heli-outrunner would be awfully strong....

Yes it would. Use a belt with teeth and the slipping is solved. Go for it!!

You have any pics of your gear drive system?
Title: Re: Motors?
Post by: Tim Wescott on May 14, 2013, 10:43:36 AM: Quote from: Dennis Adamisin on May 14, 2013, 04:57:13 AM
Worked great for 10 flights til the pinion wore a perfect groove through the idler gear. Speculation is that it might work better with one metal and one delrin gear similar to Heli proctices. If I ever try these again it would be driving through belts.

More speculation: if you do use gears, have it running in an oil bath, and use the highest-quality gears you can find, of dissimilar materials and rated for strength. The aerospace gearboxes I've seen are sealed, and use grease or oil that's carefully selected for the service. Off-the-shelf gearboxes (say from Maxon) generally limit the input RPM to less than 10K, and they're generally shrouded but not sealed, and use grease. You have to go to a gearbox specialist to get something that's rated for higher speed, and they generally want to know absolutely everything about the application before they go off and design a custom gearbox just for you (which, in my experience, then works like a charm).

What do the RC aerobics guys use for gearboxes? Has anyone tried them for CLPA, or are they just too big? If they were tried, did they work (or is that what chewed itself apart?)
Title: Re: Motors?
Post by: Dan Bregar on May 14, 2013, 06:40:07 PM: Tim

A few years back when I was flying pattern, there seemed to be two camps. One group used outrunners and the other group used a gear dirive. Surprising to me, the gear drives seemed to work all season long with only a couple of grease jobs for maintenance. I've been away from it for a few years now, so don't know what has evolved since. Of course I was one of the rapidly dissapearing glow engine flyers, who are all but gone these days. :)
Title: Re: Motors?
Post by: Dennis Adamisin on May 14, 2013, 07:14:57 PM: Hi Doug
The system was the AstroFlight, I think they call it their "superbox" A robust chunk of aluminum mounting the prop shaft on a couple sealed bearings and the motor on the other end. Here's the thread where I first showed it, and the subsequent post-mortem with folks checking in on what possibly to try next. There were some ideas on how to make the gears last but seems most folks thought a belt drive would be the way to go. Instead I just converted the bird to an outrunner...

http://stunthanger.com/smf/index.php?topic=12856.0

There are a few other pix in the "List your Set-ups" thread

I believe Tom Hampshire also messed around with gearboxes, but also had no joy.
Title: Re: Motors?
Post by: Dean Pappas on May 16, 2013, 08:09:56 AM: Hi Gang,
Yes, the gear-drives are working beautifully in F3A, but only after some-ahem- development.
Gearboxes that worked just fine for very high power electric glider setups were getting "ratty" in 50 or so flights with 20" props on planes that did maneuvers like snap rolls.
The snaps are the only place where Pattern ships do anything that approaches the pitch rates of a Stunter.
The cure (for Neu's P42 gearbox) was a little more beef and, more importantly, to space the prop shaft support bearings a whole 1/4" apart!
ALL, and i do mean all, other planetary gearboxes have the output bearings practiacally touching each other.
We, on the other hand probably need 3/4" between them as a minimum.
If you go the the Neu website ...
http://www.neumotors.com/Site/Welcome.html
and find the downloads page, you can look at the Pattern gearbox case drawing (it's the P42)
Then you can find the lightened version of the old P32 called the P29 and you'll see there is a whole millimeter between the output support bearings.
I think we want a version of the P29 with more than 20 mm between them.

Oh yes ... and I almost forgot: they'll be more expensive too!

Meanwhile, my doodles have all involved HTD toothed belts and I have yet to come up with a setup that pleases me enough to spring the bread to get a machine shop to make the pieces.

Regards,
Dean
Title: Re: Motors?
Post by: Dan Bregar on May 16, 2013, 07:28:39 PM: Dean

I am very interested in what you come up with. Having spent 21 years in the power transmission industry and having designed a few HTD drives of my own, I am interested in what you are proposing. Perhaps more will be revealed sooner rather than later. I will certainly stay tuned. :)