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October 18, 2019, 12:47:31 pm

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Went flying this morning...

Started by PDR, August 03, 2019, 17:11:58 pm

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PDR

...to try my newly refitted Graupner Micro Show Flyer. I "built" this model back in 2006 and it was OK, but it didn't really suit the 2s setup I was trying to use, and it suffered from a banana-shaped fuselage (an early ARTF issue) so it got set aside. A few weeks ago I happened to see it lurking in the workshop so I decided to refit it with new servos and a new motor with a 3s2200 setup.

I think the "ideal" motor would be an Axi 2820/10 but both of mine are in other things so I looked through the Hobbyking lists and selected a Propdrive V2 2836 (1200RPM/v). According to the specs this is a 48A motor, and at 12000rpm/v I would expect to to pull about 40A on an APC 11-6 which would suit this model well. When the motor arrived it was a bit smaller than I expected. I found that it pulled under 30A on an 11-7APC, but a 12-8 pulled 36A after the first few seconds, which sounded healthy (although the ground clearance was marginal on a 12" prop). I reckoned that full power would never be used, so the 2200 packs should be OK, and the CG came out bang on the recommended rearward limit (often the best place to start with 3d models in my experience). Ready to go it looked OK:

micro show flyer.jpg

So I flew it with a fresh battery. The take-off was "brief" and the climb with the throttle at mid-stick was vertical (accelerating, actually). It flew very nicely other than the need to constantly fly the rudder - I suspect this is a legacy of that bent fuselage. At full +/-45deg aileron rate the roll rate os something more than 800degrees/sec at 30% throttle, but the 4-point rolls are crisp and the slow rolls remarkably good. Handling balances nicely upright and inverted, although at this CG it seamed a bit reluctant to flick.

I pulled into a half throttle vertical climb to gain height for a spin when I had the first dead stick I've ever had from an electric model(!). I glided down to an uneventful landing with the prop windmilling. I picked it op and tried a a little throttle only to see the prop kick a bit a smoke pour from the cowl, so the battery was quickly disconnected. The motor bearings felt OK and in turned over smoothly, but it was sizzling hot (probably over 100degC based on a damp finger test). So I'm guessing that it was simply way over-propped and I've burned out a winding or two, implying that either this one is faulty or (more likely) it's not really a 48A motor...

So I guess I'll be fitting something else, because the model flew well enough to want to keep flying it. I may go with my initial estimate and nick the Axi 2820/10 from my Skycat - that airframe is getting a bit long-in-the-tooth anyway.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

British Victory

I'd have thought the skycat was almost as old as you pdr, my one was assembled with a hot glue gun and relegated to the loft. after a couple of summers with heatwaves thrown in I fished it out only to discover the glue was dribbling out of the joins and it was virtually rekitted. As so many of the social services say, we (I) have learned from our mistakes.
there's only one f in RCMF,
               John

PDR

Pah - I'm MUCH older than that!

My skycat was first built in 2002 and has had four different motors and four different battery configurations over the last 17 years. The hot glue on mine has held perfectly - in fact the only damage it has ever sustained was a few weeks ago when the fin hinges pulled out (the tailwheel snagged on tuft of heather). But I think I can be reallocated to the "reserve fleet" so I can nick the motor out of it.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

Bad Raven

The AXI "should" be a better motor, capable of more punishment, but then......... 

Assuming it had been a theoretically more capable AXI, the 2820-10 GOLDLINE on their own website is stated as 10x6 for Aero, 11x5 for 3D.  They only quote a 10x8 for a Hotliner.

And you used 12x8?

OK, you wattmeter tested, etc, but the two results are WAY away from each other which I feel is food for some thought?   $%&


AND/OR, given your "When the motor arrived it was a bit smaller than I expected", is it possible you fell foul of the "difference in measurement standard syndrome", as some makers use external rotor/casing and some internal stator/pole diameter/length as the size numbers.

I use Suppo 2212/6 motors a lot and that company uses the stator size but the Hobbyking version of the same thing is listed with external magnet ring rotor dimensions so has bigger numbers!!

The user formerly know as Bravedan........... Well if Prince can do it....................

PDR

Quote from: Bad Raven on August 04, 2019, 08:10:19 amThe AXI "should" be a better motor, capable of more punishment, but then......... 

Assuming it had been a theoretically more capable AXI, the 2820-10 GOLDLINE on their own website is stated as 10x6 for Aero, 11x5 for 3D.  They only quote a 10x8 for a Hotliner.

And you used 12x8?

The specs of the Axi aren't really relevant because I was using the Propdrive. the propdrive was claimed to be a 48A motor, so propping it for 36A should have been fine.

QuoteAND/OR, given your "When the motor arrived it was a bit smaller than I expected", is it possible you fell foul of the "difference in measurement standard syndrome", as some makers use external rotor/casing and some internal stator/pole diameter/length as the size numbers.

No, because I don't rate motors by physical dimensions anyway - I rate them by Kv and Imax.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

paulinfrance

Quote,
No, because I don't rate motors by physical dimensions anyway - I rate them by Kv and Imax.

size doesn't matter,,  ^-^

I have an A2Pro in my 5kilo glider and 2/3 of the size of the HK motor, and at least 50% more powerful,, :af
Mode 2 THE only way to fly

PDR

Quote from: paulinfrance on August 04, 2019, 11:20:48 amsize doesn't matter,,  ^-^

I used to think that, but then my new wallpaper fell down.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

itsme