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Old Aug 25, 2006, 07:14 PM
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L0stS0ul's Avatar
Virginia
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I run 4 servos on my Corsair and the BEC is fine on my thunderbird controller. Once in the air you won't be using the rudder channel anymore anyway
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Old Aug 25, 2006, 07:49 PM
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kensp's Avatar
Darwin Australia
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Quote:
Originally Posted by HawkLover
Thanks guys for the useful information. I think I may have my answer now. I want to see if I can run to of the BP motors on a single ESC ... I've got a spare 35 amp Jetti ESC I'm not using at the moment. I'm also thinking reduced prop length and increased pitch it the ticket here. That advantage of dual props makes it easier to prop down while still having enough thrust!

BTW, I agree that anything over 30 - 35 ounces of thrust is just too much, depending on the final weight.

Lastly, because I like to modify things, I'm thinking I will do my ailerons with a single servo. Lets not stress the BEC on the ESC!
HawkLover

I have tried a Jeti 018 3PBEC-ADV Controler for runnibng "2 on 1" and it did not work.

I think that the Tower Pro 2208-21 on two cells and GWS 10x8 HD might be worth looking at. Two cells makes four servos an achievable goal.

MotoCalc predictions for the two Tower Pro 2208-21 on 2 cells and GWS 10x8 HD propellers are:-
Motor Amps = 21.5
Motor Volts = 7.2
Input (W) = 154.4
MGbOut (W) = 74.4
MotGb Ef(%) = 48.2
Prop RPM = 5160
Thrust (oz) = 23.0
PSpd (mph) = 39.1
Predicted top speed 48 MPH

Ken
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Old Aug 25, 2006, 08:09 PM
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spinnetti's Avatar
USA, KY, Verona
Joined Nov 2001
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Quote:
Originally Posted by kensp
HawkLover

I have tried a Jeti 018 3PBEC-ADV Controler for runnibng "2 on 1" and it did not work.

I think that the Tower Pro 2208-21 on two cells and GWS 10x8 HD might be worth looking at. Two cells makes four servos an achievable goal.

MotoCalc predictions for the two Tower Pro 2208-21 on 2 cells and GWS 10x8 HD propellers are:-
Motor Amps = 21.5
Motor Volts = 7.2
Input (W) = 154.4
MGbOut (W) = 74.4
MotGb Ef(%) = 48.2
Prop RPM = 5160
Thrust (oz) = 23.0
PSpd (mph) = 39.1
Predicted top speed 48 MPH

Ken
Careful on those numbers in motocalc... I ran numbers for my F-82 and selected 9x7x4 FSK props with 2210-09 stars, and got 1/2 the predicted amps and rpm ... now I gotta get new motors with more KV I guess
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Old Aug 25, 2006, 08:31 PM
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Quote:
Originally Posted by spinnetti
Careful on those numbers in motocalc... I ran numbers for my F-82 and selected 9x7x4 FSK props with 2210-09 stars, and got 1/2 the predicted amps and rpm ... now I gotta get new motors with more KV I guess
The Motor Parameters that I used for the Tower Pro motor are those that I have measured myself not the ones given in advertisements. Like you I have found that the parameters given for these cheap Chinese motors are mostly incorrect.

Ken
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Old Aug 25, 2006, 09:51 PM
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Blaze.45's Avatar
Seattle WA, USA
Joined Aug 2005
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Your Towerpro model numbers are incorrect also.

It's 2408-21... and 2410-12.

Can you run some numbers on a 3-blade 9x7 and BP-12 Delta and BP-21? Would 2s or 3s be better by your calculations?

-Chris
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Old Aug 25, 2006, 11:14 PM
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Darwin Australia
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Quote:
Originally Posted by Blaze.45
Your Towerpro model numbers are incorrect also.

It's 2408-21... and 2410-12.

Can you run some numbers on a 3-blade 9x7 and BP-12 Delta and BP-21? Would 2s or 3s be better by your calculations?

-Chris
I am sorry Blase but the BP motor parameters I have are incorrect so any MotoCalc predictions would be incorrect.

Because of all the testing I have been doing on the new GWS motors I seem to have 22xx locked into my brain. Of course the Tower Pro is a 2408-21

I have just mounted a Tower Pro 2408-21 onto my test stand and am about to do some tests on it.

Ken
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Old Aug 25, 2006, 11:30 PM
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Its ok Kemsp, it seems the best way to know is to test it myself.

Thanks

-Chris
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Old Aug 26, 2006, 02:20 AM
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Preliminary results from testing the Tower Pro 2408-21 indicate that on 3 cells it draws more current and delivers less thrust than the GWS 2208-18T.

Ken
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Old Aug 26, 2006, 06:16 AM
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My Tower Pro 2408-21 has not survived running on 3 cells with the GWS 8 x 6 HD propeller.

The test Data was :-
12.07......Amps
11.58......Volts
139.8......Watts
15.5.......oz thrust
7,680......RPM
43.64......MPH Pitch Speed

On two cells and a GWS 9 x 7.5 HD propeller I got :-
8.42......Amps
7.23......Volts
61.........Watts
8.6........oz thrust
5430......RPM
38.5.......MPH Pitch Speed

Ken
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Old Aug 26, 2006, 06:43 AM
Confused? Who, me?
Roger Lombard's Avatar
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Joined Jan 2005
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Since a 2408-21 on 3 cells with an 8060HD is a combination I use regularly I'm curious to know what the time to failure was! (I don't normally run more than about 20 secs on WOT)
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Old Aug 26, 2006, 10:38 AM
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Good timing...

Was just a cool program on history channel on the P-38 - I'm sure it will be on a lot....
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Old Aug 26, 2006, 11:59 AM
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Dear all & Eric,

1. If you was on early brid program and did not get the mail, please contact Joyce@gws.com.tw. She will email you the info.

2. GWS is working on the box. Trying to make it the best size for delivery. Once it is all final. Will be able to email you the shipping cost.

3. As the power system or ESC, RDs are flying GWS38 every day. Trying to have the best recommendation for you. I will check with them on Monday to see if anything new.

4. As to the servo, NAROx4pcs -- I was told about one week ago. GWS38 there will be 2 servos in central nacelle - for steering nose gear & elevator. At this moment, there will be no servo for rudder. ( So I assume that there will be 2 servos for alerion. I think it is a easy set up for this airplane.) As I mentioned before it is a airplane that flyers can play and work on that.

5. Prop.& Battery -- most of the info Eric you posted here are all pretty close. RDs are still working on this. Bettery will be in the central nacelle too. 3 cells will be plent of power for Twin BL2208. I will check on 2 celles.

6. BL ESC -- 2 pcs, GWS BL ESC25A

Brushed Mtr -- can use one or Two pc(s), depends on the capacity.

** I try to update you the info that I know. Welcome any feedback from you & thank you first.***

Once I have more info, will update all of you.

Quote:
Originally Posted by L0stS0ul
Until GWS put up option of their motors I was thinking of going 2 BP-12's on either an 8x4 or maybe even a little smaller depending. I don't think this plane is gonna need almost 40 ounces of thrust I'd probably try to shoot for about 15 amps max on both BP-12's at full throttle. Maybe the 7x3.5 HD props on it. Otherwise I'd just stick with the 8x4's

What does GWS recommend as far as number of servos, speed controllers, and battery for the dual brushless setup they are selling? I see that there are dual aileron servos from the pictures so at least 4 naro size servos. 2 for ailerons 1 for nose steering, and 1 for elevator. Is it recommended to use 1 speed controller or 2. If 2 speed controllers are they recommending dual batteries or just doing 1 pack feeding both speed controllers. What size battery is recommended? I only use lipos so would you want to use 3 cells on the supplied motors or 2 cells?

Thanks I wanna start picking up the items when I see them at my LHS. I also need to put in an order for some new lipos soon so knowning that I can save on some shipping.

Thanks
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Old Aug 26, 2006, 01:11 PM
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Darwin Australia
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Quote:
Originally Posted by Roger Lombard
Since a 2408-21 on 3 cells with an 8060HD is a combination I use regularly I'm curious to know what the time to failure was! (I don't normally run more than about 20 secs on WOT)
Roger

The 2408-21 will start but as soon as it is throttled up it cuts out. I have tried a GWS15 Amp ESC, a Chinese No Name 30 Amp ESC and a Jeti 18 3PBEC-ADV ESC and the same thing happens with all of them. I think that I ran the motor WOT too long so it got hot and the insulation on the wires has broken down.The Chinese enameled wire seems to have a low heat tolerence.

The motor did not fail suddenly. It has just slowly gotten worse since the 8 x 6 on 3 Cells. The 3 cell battery being used was an EVO 1800mAh 20 C battery and the ambiant tempreature was 30+ deg C. The checking using the different ESCs was on two cells.

What is your static amp draw using the 8 x 6 on 3 cells?

Ken
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Old Aug 26, 2006, 02:12 PM
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L0stS0ul's Avatar
Virginia
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Thanks for the information Ray. That helps. I see now that I re-read your post that right now you all are recommending 2 of the 25 amp brushless speed controllers for the brushless motors.

Ken, I can only imagine that running the 8x6 on the 21 for an extend period WOT on the bench would kill it quick. On the 8x4 the motor is right at the limit and running WOT to long on the bench will hurt it as well (damaged one in testing as well but with the 8x4). In my tests I was seeing just under 13 amps WOT on the bench with the 8x4. The motor is only rated to 13. In the air the 8x6 should be ok due to unloading but on the bench its definitally well above 13 amps.
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Old Aug 26, 2006, 08:20 PM
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FWIW, I just ran a Tower Pro 2410-09 Star on a common sense 1250 3s pack (Tower pro 15a controller), with a FSK 3 blade 9x7 prop.

9.8A @ WOT
11.43V
5970 RPM indicated (I never quite trust this under incandesant lights)
This combo peaked at 21oz of thrust - more than I need (I wish I could get the FSK props in other pitches).

For reference, this is about the same numbers I get for the SK400 on 2S..., and about what motocalc predicted for 2s also... Is there a Tower motor in this line that would give similar performance on 2s (my 4 blade only pulls 5A on 2s)?

A couple of this setup with a 2400 pack would be nuts in the P-38


PS, Ken, what numbers are you plugging into motocalc? I'd like to tune it up to get somewhere close to actual performance...
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