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Old Dec 10, 2002, 08:23 AM
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Phoenix 10 or 25 for MiniAc 1215/16

Hey, guys, putting my x-mas list together and wanted to know what would work better for a MiniAc 1215/16 mated to a GWS C or D gearbox going into a Miniflash. The D would be turning a 12x6 and the C a 10x7 or an 11x8. Battery packs would be 8x1100 nimh's.

I'm not sure if I'll be pulling more amps than the 10 could handle but I'd sure like to save the extra weight over the 25. Or will the weight even matter with the Mini?

Thanks for your help.

Ron
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Old Dec 10, 2002, 10:42 AM
Mountain Models Wannabe
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Ron,

I'm evaluating the MiniAC motor and if I can find a combination I love, I will package it. If I do it will have the Phoenix 25, not 10. The weight won't matter and the extra capacity is worth the money IMHO.

Doug
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Old Dec 10, 2002, 10:48 AM
A Clinger
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What Doug said . Phoenix-25 is the one to get.
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Old Dec 10, 2002, 10:51 AM
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Thanks, guys. I'm just so used to being weight conscious that an extra 8.5 grams sounds like a ton to me especially after adding in two extra ounces for the 1100's. I imagine the extra power will more than make up for it.

Ron
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Old Dec 10, 2002, 11:24 AM
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oh yeah . You'll be going 'why did I worry so much ' LOL after that first flight!
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Old Dec 10, 2002, 11:32 AM
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RC, did you notice any difference in the fight characteristics? Other than more vertical than you had before?

Thanks

Ron
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Old Dec 10, 2002, 01:36 PM
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Hi Doug, Ron...

Doug as you know I've been running the AC1215/16 with a Phoenix 10 in my 3D for a while now. Started with a 9x7 prop and moved over to a 10x8 (both GWS). The EPS 'C' gearbox was modified to fit the motor as well as a DX-A shaft installed with a 2mm thick bearing race to minimize friction at the 'C'-clip/washer interface. 'C' spur gear (64T) and 'B' pinion (12), ratio is 4.57:1.

So far with the 10x8 running WOT, the Phoenix has yet to current limit on me and I've been carefully watching the temps of the FETS. So far they've never gone above 115F while my batteries have seen 140F and the motor 125F.

Of course this has been with cooler weather (48F to 68F) and I suspect come summertime, I would see at the least a 10-15F jump in temperatures. Being a slower flyer and combined with the thicker airfoil, the MF would require more watts to fly her with equivalent airspeed as the thinner airfoiled 3D. So I would agree that the 25 would be the wiser choice. I'll be experimenting with some cooling ideas which if they work, would only add a few grams to the plane yet be able to dump an additional amount of heat away from the controller. The motor I'm not worried about as MM states the danger zone to be above 200F.

FWIW, I think the Mini1215/16 is an excellent alternative to the Hacker set-up, and hopefully we will be able to have a side by side comparison of these power systems in the future as more pilots convert their planes over to BL.

Regards,
Roger
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Old Dec 10, 2002, 01:51 PM
BEC
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Quote:
Originally posted by ronrandle
Thanks, guys. I'm just so used to being weight conscious that an extra 8.5 grams sounds like a ton to me especially after adding in two extra ounces for the 1100's. I imagine the extra power will more than make up for it.

Ron
Most of that extra weight is thicker wiring - and the plane will never notice that 1/3 ounce with the HECells!

I just received a Phoenix-10 that will be used to drive a 20 turn miniAC for the MiniFlash (to be used on 3S2P 1020 Kokams), but there I'm going to prop for 8-9A tops.

In the SB and with the 16T miniAC I'd go with the -25.

OTOH, I flew my 16T miniAC powered SB for awhile on an 8A MGM ComPro controller, but ONLY with 720s - peak draw was right around 7A. With the HECells it goes up to 10-11, and going up to the 10X7 prop and HECells it peaks at 14 and settles in around 12.5.
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Old Dec 10, 2002, 02:05 PM
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Guys, thanks for replying.

The interesting thing is, the folks at Castle Creations recommended the 10. With only a ten dollar price difference it's not an issue, but I'm still interested in saving weight even though RC has assured me I won't notice.

I suppose I'll be getting the 25 to be on the safe side. Since I'm a fairly new convert to e-powered planes I'm not sure of all the implications in gearing/prop size amp draw calculations and I want to avoid a costly mistake.

Roger, what were you describing for the shaft and ball bearings for the GB? Since all the parts are now available at aeromicro you can mix a match pretty easily.
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Old Dec 10, 2002, 02:10 PM
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Hi Ron,

Check out this thread

Regards,
Roger
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Old Dec 10, 2002, 02:13 PM
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Go With Phoenix-25 (IMHO)

FWIW, I think I'm taxing my MiniAC1215/16 & Phoenix-25 a little more using the A-gearbox on my SB3D. Wanting to use an RC car pinion instead of pressing on the GWS pinion, I was forced to use the A-gearbox since the smallest 64P pinion I could find was a 16T. Anyway, I've never had the ESC cut out (overheat/current limit) either & I figure the 25A version would give me a little more flexibility later.

In addition to Roger's input, I feel the MiniAC is a good alternative to the AstroFlight 010, since the AF setup apparently requires ten cells to perform well. I wanted to run no more than eight cells, and I've found the MiniAC setup is an excellent option.

I've posted this before, but here's my setup...

SB3D
MiniAC1215/16
Phoenix-25
EPS-300C-AS
APC 10x7SF
8 600AEs = unlimited vertical (freshly-charged cells) & 4-5min spirited flight
8 HECells = ~200ft vertical & 8-9min spirited flight
8 720AAA NiMHs = ~15ft vertical & 6-7min mild (3/4throttle) flight (voltage drop cuts ESC @ ~15sec of full-throttle)

Good luck!
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Old Dec 10, 2002, 10:52 PM
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Wild Moose

Roger, I saw that thread on the shaft mod and wondered if you could just make a bushing out of brass tube? I don't have any old bearings and it sounds to me like it's primarily a matter of keeping the c-clip from contacting the washer or bearing.

What do you think?

Ron
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Old Dec 10, 2002, 11:49 PM
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Hi Ron,

Yes you are correct, the main problem occurs when the washers' OD contacts the aft bearing' outer race. Since this race is fixed you have a major source of friction as now the thrust force generated by the prop literally compresses the washer and C-clip together.

Any tube will do fine as long as it contacts the inner race of the aft bearing and is a smooth fit onto the shaft. If there is slop you run the risk of having the tube contact the bearing outer race and your back at square one.

Another thing you could do is to distort the washer into a Belville shape (conical shape where the ID of the washer extends in one direction). The idea being the ID will contact the aft bearing inner race much as the race sleeve I'm using.

It won't take much force to do this to a washer and would be a simple way to correct this interference without having to get a new shaft...

Regards,
Roger
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Old Dec 11, 2002, 12:29 AM
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Quote,

"RC, did you notice any difference in the fight characteristics? Other than more vertical than you had before? "

The 'fight' characteristics No. Didn't notice any of those ; However 'Flight' charactistics -- well yes. You go a little faster (rolls are quicker), since you have more vertical it opens up more things to try like the 'humpty bump' which is pityful stock, vertical 8 and 9 maneuver are much improved. Just gives you more options to play with -- a new flight envelope (as the experts call it; I am not one of those folks.... far from it).
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Old Dec 11, 2002, 07:42 AM
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Guys, thanks for the feedback.

Moose, I took a look at an old 300-A gearbox and found the same gray mess that you mentioned in your other post, and yes, there was a lot of play in the fore-aft movement of the shaft. I'm definitely going to try and correct that for the MiniAc.

RC, yeah, those dang 'fight characteristics' get you every time. I was more curious if the added weight of the 1100's made the plane seem heavy at all. From what I've read about brushless and the Miniflash it doesn't sound like it's an issue.

Talk to y'all later.

Ron
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