The Comet Stinson SR-7 - Another Free Flight conversion project - Video Addeded - Page 7 - RC Groups
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Sep 25, 2010, 10:12 AM
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scrubs's Avatar
Thanks for the comments guys.

UNGN,
Ah but sometimes those few extra bucks add up for an old retired guy like myself.

Paul,
Thanks for the info. Aside from plans up the wazoo I've got a goodly number of old kits laying around that would work. Just happen to have a PZ P51 motor from a FF project and a brick too.

bill
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Sep 25, 2010, 11:01 AM
Power Wheels Guru
UNGN's Avatar
Quote:
Originally Posted by scrubs
Thanks for the comments guys.

UNGN,
Ah but sometimes those few extra bucks add up for an old retired guy like myself.

bill

A $17 5g 2S Brushless setup (motor+ESC+shipping) will outlast $60 worth of Mustang motors and deliver 2X the thrust for about 8g more weight, total (including the 2S battery).

With Mustang motor being what they currently are, I'm hesitant to recommend someone put them into a scratch built plane... at least until the quality gets better.
Sep 25, 2010, 11:42 AM
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scrubs's Avatar
I agree about the motor I've had one crap out already. But then again a 2 cell 10 gm $15 brushless I bought was DOA also. That was my first forray into brushless & made me hesitant.

bill
Sep 25, 2010, 10:29 PM
Registered User
ckreef's Avatar
Quote:
Originally Posted by UNGN
A $17 5g 2S Brushless setup (motor+ESC+shipping) will outlast $60 worth of Mustang motors and deliver 2X the thrust for about 8g more weight, total (including the 2S battery).
I'm into this idea. Please give us a link and I'll order a setup (or 2) on Monday.
Sep 25, 2010, 11:32 PM
Power Wheels Guru
UNGN's Avatar
Quote:
Originally Posted by ckreef
I'm into this idea. Please give us a link and I'll order a setup (or 2) on Monday.
6A ESC

5g Outrunner

Plugs to make 2S Serial battery connectors and plug into brick.

Wire it like this:

Sep 26, 2010, 11:03 AM
Registered User
ckreef's Avatar
Thank You for the links and the nice diagram/picture. Going to order a setup later today. A couple of quick questions.

Does it matter if I use a 1N4001 or 1N4003 or 1N4005 ???

Any prop recommendations for this setup?? I was thinking either a GWS 4530 or GWS 5030
Sep 26, 2010, 11:12 AM
Power Wheels Guru
UNGN's Avatar
Quote:
Originally Posted by ckreef
Thank You for the links and the nice diagram/picture. Going to order a setup later today. A couple of quick questions.

Does it matter if I use a 1N4001 or 1N4003 or 1N4005 ???

Any prop recommendations for this setup?? I was thinking either a GWS 4530 or GWS 5030
Any of those diodes will work. Both those props and the 5043, too will work fine. It depends on how much thrust or run time you want.

With a 60-70g plane, the motor is going to be at 1/3 throttle a lot.
Sep 26, 2010, 11:17 AM
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scrubs's Avatar
I guess my question turned into hijacking Paul's thread. You might want to beef up the Comet construction if you go with a setup like this. 90 gms of thrust would certainly test those wing spars, LE & TE.

bill
Sep 26, 2010, 11:30 AM
Power Wheels Guru
UNGN's Avatar
Quote:
Originally Posted by scrubs
I guess my question turned into hijacking Paul's thread. You might want to beef up the Comet construction if you go with a setup like this. 90 gms of thrust would certainly test those wing spars, LE & TE.

bill
Just because you have the power, doesn't mean you have to use it This is a good setup for 20-25" WS planes, not the 16" ones.

I found the 5g motor is a lot smoother than a Mustang motor gearbox and vibrates a lot less under power. Since the mounting flange of the gearbox is to resist motor toque, prop vibrations can cause it to rock back and forth, so the mount has to be strong in a few different directions.

The outrunner has motor torque and prop vibration along the same centerline so the mount can be a firewall on a bulkhead.

If it ends up with too much power, you can always limit the throttle % in the radio.

The way this plane is constructed, he could make a 5g power module that swaps right in place of the Mustang unit.
Sep 26, 2010, 10:21 PM
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PaulBrad's Avatar
Great discussion on the use of the 5g brushless motor in an airframe like the Stinson. I certainly agree that going brushless is the best long term solution. When I selected the P-51 power package I was looking to keep the single cell built in ESC set up of the radio brick. I was also interested in knowing if the P-51 motor/gear drive would handle the model adequately. I have been able to answer that question.

The comment about being able to easily swap out the brushed motor with a brushless is spot on. The slide out tray makes the motor change and going to a two cell battery pack pretty easy. I probably will not do that with this model as it has all the power it needs to be a happy flier. If the motors don't last then I may revise that decision.

Regarding the airframe strength, the Stinson is actually very robust in terms of handling aerodynamic flight loads. It could handle the thrust of the 5g brushless motor with no problem. The strut braced wings can take a lot of flight load. Flying the model in a scale fashion would certainly leave much of the available power in the can so to speak. Some of the stick and tissue war birds would be great applications for the motor. You would have the power to fly the aerobatics the full scale aircraft could handle.

Thanks again UNGN for your insight and the information on setting up the brushless motor with the AR6400 receiver brick.

Paul Bradley
Sep 26, 2010, 10:48 PM
Registered User
ckreef's Avatar
Quote:
Originally Posted by PaulBrad
Thanks again UNGN for your insight and the information on setting up the brushless motor with the AR6400 receiver brick.
I too really do appreciate that information as I now finally understand this setup. Something my noobie brain was lacking before now.

When reading through the reviews for that ESC someone posted that "yes it can run with 1S lipo!!!" . Would make a great test to try it out with a large Hyperion 1S lipo.
Sep 29, 2010, 12:29 AM
Registered User
PaulBrad's Avatar
The wind spirits cooperated with me today and provided a nice dead calm evening. As a result I was able to get in two nice flights with the Stinson. The new motor is not showing any signs of stress so I guess the failure of the original motor was just one of those early mortality issues.

My wife was with me to run the video camera but she has limited experience following small model airplanes with the camera. She did her best but we did not get any useable footage. Hopefully I will get some presentable video sometime in the not to distant future.

I still have some trim tweaking to do with the model. The left wing panel has developed a very slight washout warp. That is causing the model to crab just a bit to the left. It is easily managed with a small amount of rudder input but does need to be addressed. Overall she is a very happy flier. In the dead calm wind conditions cruise was maintained at 1/3 throttle.

Paul Bradley
Sep 29, 2010, 01:13 AM
Lawn dart pilot/builder
Prime_8's Avatar
great news.
too bad about footage .
Oct 02, 2010, 12:33 AM
Registered User
PaulBrad's Avatar
The forces of nature are keeping me grounded as far as the Stinson goes. It has been very windy and the forecasters say that will continue for several more days. I hit the road Monday for nearly two weeks of traveling. There will hopefully be a few windows for flying during this two week period. If not then I should be able to get some video at KIEF in two weeks.

While watching the trees moving like a hurricane was passing through I decided to bite the bullet and get the dummy engine made up and installed on the model. I have received several very good suggestions in this thread for handling the restrictive geometry I gave myself with the disk that retains the slide out equipment tray. I finally decided to use the decal suggestion. My only deviation was the addition of a 3D simulated front crankcase. I found a really good head on photo on the Internet of the Lycoming 9 cylinder radial engine used in the SR-7. That photo got the background trimmed out and was then re-sized to the proper diameter. The rocker covers don't show as they are tucked away under the cowl. While not as good as something more three dimensional, it is an upgrade from the previous flat black disk. The photo was printed on white ink jet water slide decal paper. The simple geometry of the front disk made trimming the decal pretty easy.

Paul Bradley
Last edited by PaulBrad; Oct 02, 2010 at 12:30 PM.
Oct 02, 2010, 04:52 AM
Lawn dart pilot/builder
Prime_8's Avatar
very cool man .


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