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Old Apr 10, 2002, 01:40 PM
an earth bound misfit, I
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St. Pete, Florida
Joined Sep 2001
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Best prop for Switchback / Astro 010?

I need some advice ya'll. Just got the Astro 010 installed in my Switchback Sport and would like to know if there is a better prop than the APC 9x6".

The AUW with 8 cell 720AAA NiMH is 13.7 ounces / 387 grams.
The weight without batteries is 9.9 ounces / 279 grams.

I also have some 5/4AAA 800mah NiMH and 2/3A 800mah NiMH packs. They weigh 4oz/113gr, and 5.8oz/164gr respectively.

I would like to try some 9 and 10 cell packs. Any advice on what I should get? I was thinking 10 720AAA NiMH's.

I used part of the GWS EPS 370 motor mount to install the motor and gearbox to the stock mounting stick. Fits perfectly. The prop shaft is about 3/16" lower than it was before. Hope it won't make too much difference. The prop is also a little farther out front ~3/8".

Altogether the motor, gearbox, speed control and prop added .9 ounces / 26 grams.

Thanks in advance,

BC
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Old Apr 10, 2002, 01:42 PM
an earth bound misfit, I
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St. Pete, Florida
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After I took the pic I gave in to paranoia and added a second tie wrap.
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Old Apr 10, 2002, 01:44 PM
an earth bound misfit, I
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Can't wait for the wind to allow a test flight.
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Old Apr 10, 2002, 02:05 PM
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Dallas,TX
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i have zero experience with the astro motors (too exp for my flying budget) but I have lots of experience with props. The APC 9x6 is an excellant prop! In fact, I like all the APC props. I have them ranging from 8 to 11 inches with varying pitches. Very tough props.

As ive said before, I don't like the GWS 9x7. Maybe im just a crummy flyer but mine break easily when landing in tall grass. However the 10x8 gws prop works very well if it isn't too much for your motor setup. Just make sure you balance the GWS props as mine always need some adjustment from the package. Without balancing, my plane feels buzzy when I power up.

Also worth looking at some of the carbon fiber props if you are looking for that last 5% performance edge. BTW, nice looking setup, let us know how she flies!
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Old Apr 10, 2002, 02:22 PM
What Canary?
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Huntsville, AL USA
Joined Jul 2000
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BC,

How many turns is your 010? I have a 14 turn with the 3.3 GB and used a graupner slim-cam 9x6 prop with 10 720NiMH cells. Right after a peak charge (cells still warm) I get 6.1A. This drops down below 6 amps (rating for my version controller) after about 10 seconds. I'm sure it unloads in the air to much less than that (I'm at 6500+ ft ASL so YMMV). I had it in a Champion which I crashed, so it needs a new home. Problem is, My Switchback flies so well with the 370 and 8 600AE's, I don't want to change it. But on the other hand, the 010 flies so well (and long) that I am going to try and pull the pinion gear this weekend and attach the motor to a GWS gearbox. That should bring the weight down considerably. Am interested to know how you like it.
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Old Apr 10, 2002, 02:34 PM
Mountain Models Wannabe
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Ithaca, NY USA
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BC,

I'm jealous.

Hang on tight when you try it!

Doug
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Old Apr 10, 2002, 02:37 PM
an earth bound misfit, I
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St. Pete, Florida
Joined Sep 2001
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Thanks, My motor is the 14 turn with the 3.3 gearbox.

I was happy with the power from the 300 too. But with 8 cells I used up the brushes in 30 flights, or 5 1/2 hours. I'm not complaining, I could just stick in another motor but wanted to try it with a little more power and duration.

If you're using 8 600AE's it won't be long before you need a motor too.

I know the gearbox is heavier but I'm hoping that it will be quieter than the GWS gb.

Matt, thanks for the prop info, I hadn't even thought of a carbon prop. I was thinking it might be better for me to use a GWS 9x7 so if I hit the ground with it it'll break the prop insted of ripping the nose off. I really haven't had any problems with the 9x7 in my moth.

Hi Doug, glad to hear you approve.

BC
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Old Apr 10, 2002, 06:32 PM
BEC
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Auburn, Washington USA
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FWIW, Motocalc predicts that will be about 5000 RPM and about 4A. Since I'm seeing around 4500 on the GWS 300 - B at 7+A this sounds like a really good combo. Please let us all know how it goes!
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Old Apr 10, 2002, 06:51 PM
jah
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North Georgia
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BC, looks awesome. I think the APC electric props are great, so are the Graupner Slimcam props. Got a 9X7 APC on a speed280bb and 5:1 gbox, and 8X6 slimcam on a speed280bb and 4:1 gbox. Both work great. The speed280bb fits in the GWS 370 gearbox, but can't find a 12 tooth pinon for the speed 280. Did you just pull the pinon on the old 370 motor, and did it fit the Astro. Where did you get the Astro?

Oh, hey this is your thread, sorry Wayne!
Later on, and good luck with the Astro
Jerry
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Old Apr 10, 2002, 09:57 PM
an earth bound misfit, I
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St. Pete, Florida
Joined Sep 2001
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Hi Bernard, that's really good to know. I will report, whatever happens. I was kinda hopin' someone would calculate it on Motocalc. Thanks

Hi Jerry, I'm going to have to try some other props too. I got the Astro from Todd's Models. The motor, gearbox and esc were all completely assembled, (with a deans polarized connector for the battery) all I had to do was plug it in. The gearbox weighs twice as much as the EPS gb. All together the SB gained .9 oz.

The pinion is still on the remains of the 300. I don't have a puller. Do you want it?, if so drop me an email. It could be drilled out if needed to fit the 280.

BC
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Last edited by Basketcase; Apr 10, 2002 at 10:28 PM.
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Old Apr 12, 2002, 09:11 AM
an earth bound misfit, I
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St. Pete, Florida
Joined Sep 2001
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It works! Got in three flights this morning of about 12 minutes each.

The 010 on 8 cells, 720mah AAA & 800mah 5/4AAA and the APC 9x6" prop has a little less power than the EPS B, and about a minute more duration. Time for more cells??

I'm not complaining though. It's just what I hoped for. Still plenty of power, quieter and sounds smoother, better.

Would like to try 10 720 NiMH, should I anticipate any problems with voltage sag or anything? Would any other cells be better?

I modified my GWS motor mount again but want to try moving the motor back 1/4" (6mm). In fact I have a new idea how to do it, if anyone has a EPS gearbox they would like to sell please email me. Mostly to help the CG but also to make it look better.

One thing we noticed was with the old setup it used to hum when at high speed like in a dive. I always thought it was the covering vibrating. With the new setup there is no hum at all and it seems to dive at the same speed. One of my flyin buddies thinks it was the prop that was making the noise. Has anyone else heard this? Prop, covering, control surfaces, what do you think it is/was?

Off topic > I used to have a Hobie Cat and when it really got moving the rudders would hum very similar to the plane noise.

The more I fly it the more I like it!

BC
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Old Apr 12, 2002, 09:24 AM
Real Men Fly Pink Planes...
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United States, TX, Rockwall
Joined Jun 2001
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Did you take any pictures of the motor mount modifications...

Kirby
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Old Apr 12, 2002, 10:01 AM
an earth bound misfit, I
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St. Pete, Florida
Joined Sep 2001
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Hi Kirby, I'm using the mount backwards after cutting out the stop where the stick goes thru, to let the gearbox sit flush. I originally cut the back (ex-front) loop off and was going to use it stock length.

Then figured out that if I cut the legs that hold the front and back together I could have used both loops for motor saddles instead of the piece of popsicle stick I have now.

Then I'll have two choices, get the motor stick loose to move it back, or cut 1/4" off the end of the stick.

I can see where the GWS gearbox would cure both these problems as well as weigh less but I really like the way the plane sounds now.

If I hadn't already cut the second loop off I would have made it shorter still. You can see the cut off pieces in back.

BC
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Old Apr 12, 2002, 10:35 AM
an earth bound misfit, I
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St. Pete, Florida
Joined Sep 2001
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P Calc is showing:

8 cells 720mah 9x6" APC
3.7 amps, prop RPM 5409, static 12.5oz, inflight 7.3oz, 11:35 minutes

9 cells 720mah
4.4amps, prop RPM 5884, static 14.8oz, inflight 8.6oz, 9:51 minutes

10 cells 720mah 9x6" APC
5.0 amps, prop RPM 6323, static 17.1oz, inflight 9.9oz, 8:34 minutes

This is very close to what Bernard reported from Motocalc and I feel it's close to what my flight testing showed. Am going to try some other batteries.
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Old Apr 12, 2002, 01:53 PM
BEC
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Auburn, Washington USA
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Does P-Calc have good constants for the APC SF props? I've been using the same ones as for the Thin-E, which is the "thin carbon folder" in E-calc/M-calc. Those worked well matching measurements to calculations when the Thin-Es first came out.....

If you're really getting 5400 out of only 4A you've got a super deal there - much better than what I've seen with the EPS-300C B ratio I've in my plane. And I just got the spare motor from Perry at AeroMicro.....
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