Will in runers work and if not why not?

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


Just wondering

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.

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

Hi Dan,
in the Pattern world, the geared inrunners actually have the slight weight advantage.

Dean

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.

.....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?

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. 

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