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Old Nov 12, 2008, 01:49 PM
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N99JH's Avatar
Hartsville, SC
Joined Apr 2006
848 Posts
Quote:
Originally Posted by Lynxman
Here are a few pics. I'm going to make a new reduction system with a more advanced propeller soon. I'm mostly into jets at the moment though.
Lynxman

I don't mean to hijack your webpage but was curious about your system. I ran the numbers through Motocalc and it shows very low efficiency for you drive system, something like 52%. The video clip shows very impressive flight performance though. Can you tell me at what RPM your 21.5-14.5, 3 blades prop turned at motor wide open please?
Thanks
Joshua
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Old Nov 12, 2008, 01:55 PM
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Lynxman's Avatar
Troms, Norway
Joined Jan 2004
7,098 Posts
Motocalc does not calculate Axi motors accurately based on the numbers from Model Motors. The wide open static prop rpm is ~4000-4100 rpm, which gives about 7000 motor rpm and a current draw of 48-49 A.

To more accurately estimate performance at 8S I use the following motor constants:
kv: 285
No-load Current: 1,6 A
Resistance: 0,045
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Old Nov 12, 2008, 02:00 PM
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N99JH's Avatar
Hartsville, SC
Joined Apr 2006
848 Posts
Quote:
Originally Posted by Lynxman
Motocalc does not calculate Axi motors accurately based on the numbers from Model Motors. The wide open static prop rpm is ~4000-4100 rpm, which gives about 7000 motor rpm and a current draw of 48-49 A.

To more accurately estimate performance at 8S I use the following motor constants:
kv: 285
No-load Current: 1,6 A
Resistance: 0,045
Thanks. I appreciate the quick response and will run the numbers again. I am building a belt reduction with 2.5:1 ratio to drive a 31.5 X 31 scale prop with a Hacker A60 18L on 12S 5000 mAh.
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Old Nov 12, 2008, 03:35 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,996 Posts
Quote:
Originally Posted by Lynxman
Here are a few pics. I'm going to make a new reduction system with a more advanced propeller soon. I'm mostly into jets at the moment though.
Very VERY cool.

The prop looks great also.

Thanks, DAG
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Old Nov 12, 2008, 03:44 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,996 Posts
Quote:
Originally Posted by Lynxman
Motocalc does not calculate Axi motors accurately based on the numbers from Model Motors. The wide open static prop rpm is ~4000-4100 rpm, which gives about 7000 motor rpm and a current draw of 48-49 A.

To more accurately estimate performance at 8S I use the following motor constants:
kv: 285
No-load Current: 1,6 A
Resistance: 0,045
I thought anytime you used a belt drive that you would lose at least 20% efficiency. Your design looks very clean though. Are you turning that 20" 3 blade at 4500rpm??? Because I had written of having the true scall size prop of 20" on this plane. Your set up X6 for my B-36 would fly it fine.

Thanks, DAG
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Old Nov 12, 2008, 04:31 PM
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N99JH's Avatar
Hartsville, SC
Joined Apr 2006
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Quote:
Originally Posted by dag214
I thought anytime you used a belt drive that you would lose at least 20% efficiency. Your design looks very clean though. Are you turning that 20" 3 blade at 4500rpm??? Because I had written of having the true scall size prop of 20" on this plane. Your set up X6 for my B-36 would fly it fine.

Thanks, DAG
Properly designed belt reduction system will provide AT LEAST 90% efficiency, usually even better than that!
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Old Nov 12, 2008, 05:41 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,467 Posts
Quote:
Originally Posted by dag214
Hi Jack,
I am not trying to turn a 20" prop, I am cutting a 20" down to a 18" to get the preformance I need.

Attached is what I will be putting on the motor.
Am am at about 52 amps, and that's at 100 power. I will be running at about 2/3 throttle.

Thanks, DAG
Just trying to be helpful, I've had 4 planes running Axi 4130/16 setups and they routinely draw more than 75 amps (on 6S @ 7,450 RPM) turning a 17 x 10 or 18 x 8. I know you're looking at a 4130/20 but it's pretty easy to see even with the different KV you're loading that motor up too much. I'm rooting for you no matter what, nice build so far...

Jack
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Old Nov 12, 2008, 05:46 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,996 Posts
Quote:
Originally Posted by jfetter
Just trying to be helpful, I've had 4 planes running Axi 4130/16 setups and they routinely draw more than 75 amps (on 6S @ 7,450 RPM) turning a 17 x 10 or 18 x 8. I know you're looking at a 4130/20 but it's pretty easy to see even with the different KV you're loading that motor up too much. I'm rooting for you no matter what, nice build so far...

Jack
Jack you are 100% correct that I will be getting close to the 55 amps, I just need to do some testing and see what happens. Every electric that I have built has been over powered. I never use full throttle, but that is just me. I like a long ground roll and a scale climb-out. I still feel that a 18-10 will fly this plane all day even with a prop pitch speed of 49mph. And everyone's input is very welcome.

Thanks, DAG
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Old Nov 12, 2008, 06:11 PM
JR > Futaba
pvtzemerak's Avatar
Green Lane, PA
Joined Mar 2008
341 Posts
SUBSCRIBED!!!
man, nice looking plane, goodluck!
--pvt
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Old Nov 12, 2008, 06:50 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,996 Posts
Quote:
Originally Posted by pvtzemerak
SUBSCRIBED!!!
man, nice looking plane, goodluck!
--pvt
Thanks,
DAG
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Old Nov 12, 2008, 06:52 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,996 Posts
More fuse pics. Been working a bunch and not much more done, just a few bulkheads. Will try to get more cut out tonight.

DAG
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Old Nov 12, 2008, 07:24 PM
Übung macht den Meister..
Deuce's Avatar
United States, OR, Fairview
Joined Jul 2006
3,013 Posts
I've been lurking since the start of this thread, and have been most impressed! I have to second the sentiment about the long, scale takeoff runs, with a graceful climb-out! I've watched too many videos of nice scale models that are flown like toys...

One question that's been on my mind about this: Will the motors/props really produce the incredible sound that could only come from the B36? Hehe!
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Old Nov 12, 2008, 08:27 PM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
Looking better and better Dag !!!

That P-40 is awsome Lynxman !!!!

Seeya, Tim
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Old Nov 12, 2008, 10:11 PM
Vintage Flyer
Indiana
Joined Jan 2005
1,674 Posts
Nice P-40 Lynxman

Tim and Dag and Lynxman

Here's a picture of great piece of aviation by artist John Shaw.
I have a copy of it signed by many of the Flying Tigers.
Great investment!
It has went up in price 250% since I purchased it.
I have another one called The Warrior and the Wolfpack,
and this one is called
"Tigers In The Gorge" when in 1942 the Flying Tigers with just 8 airplanes and led by "Tex Hill" stopped the Japanese cold from crossing the Salween River at the Salween River Gorge.
had the Japanese got across, they would have easily conquered China.
So you can say the Flying Tigers changed the course of the war and the course of history.
The last picture is of a B-29 at Iwo Jima.
All three paintings are by artist John D. Shaw
My painting of The Warrior and The Wolf Pack is signmed by Gunther Rall ( German Luftwaffe ace, Bud Mahurin, American fighter ace from my hometown of Ft Wayne Indana, and also signed by Francis "Gabby" Gabrieski.


Ed
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Old Nov 12, 2008, 10:23 PM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
Very nice Ed !!!

Thanks for shareing it with us !!!

Seeya, Tim
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