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Old Dec 20, 2010, 10:31 PM
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MAX Kp?

Well, i found in another post that the MA 3 Blade props have a Kp of about .76.
I re-ran Scorpion Calc and found my output watts to drop significantly (i.e. 4020 13X8 @ WOT from 808W to 676W)

It still seems I have more power than needed, but maybe not by that much
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Old Dec 20, 2010, 10:52 PM
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Victorville, CA
Joined Jun 2006
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Originally Posted by Doug Bartley View Post
Hi Terry First, Look up Innov8tive Designs.com, download the Scorpion Calculator. You will have all the info you need to make a possible selection.
Second: In order for anyone to help you, we will need far more info than general specs of a nitro engine! What nitro engine do you have now that can spin this 14x14N @ 10500rpm? I'm pretty sure it won't be a 40 sized engine!

Expected AUW, wingspan, plane manufacturer. What cell count do you want to use, or is it wide open? How fast do you think your plane should go? Can the plane be easily converted to electric - some are really poor choices do to weight, setup. if the plane doesn't have a battery hatch, they can be real bears to convert!!
I have a Kelly Racer (Kyosho), it weighs 6lbs,6ozs RTF with a Scorpion 4020-12 on 6S/5000/25C spinning a 12/12 Apc E prop. It goes 124.6 mph according to GPS. prop is spinning @ 10200 rpm. Just an example of what to expect! Doug Bartley
Hi Doug,

Thanks for the detailed answer.

I am flying a Phoenix Models Strega with a YS 1.40. It turns the 14X14N at about 9800. Unfortunately, that is not quite enough to reach breakout in our Gold class. We changed the rules this year and now electric power is allowed so I am looking at different options to see if I can build something cool for next season.

There is guy who is building an E-flite P-51B wit a Scorpian 4045, 560kV and is turning a 13x13.5 around 10,500.

Thanks, Terry
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Old Dec 21, 2010, 12:26 AM
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Canada, ON, Owen Sound
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Quote:
Originally Posted by Edgar Perez View Post
Well, i found in another post that the MA 3 Blade props have a Kp of about .76.
I re-ran Scorpion Calc and found my output watts to drop significantly (i.e. 4020 13X8 @ WOT from 808W to 676W)

It still seems I have more power than needed, but maybe not by that much
Hi again Edgar: I have not tested either of the proposed motors here. What I have found is that the generic testing is based on some formula that in reality doesn't work for any combo I've tested. i don't know any way to get accurate measurements except to do it yourself. I see at least a 20% lower amp numbers in my tests.
Here's an example: 4025-12 15/8/3 blade, Scorpion Calc shows 86.5amps and 1921 watts. My test showed 58 amps and 1400 watts. 27% difference!
I'd be tempted to buy one of each motor size, and one of each prop size, and run my own tests on your preferred cell count.
On a project of this scope and costs, it may be the only way to assure results unless someone here has already done it!! FWIW Doug Bartley
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Old Dec 21, 2010, 12:35 AM
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Canada, ON, Owen Sound
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Originally Posted by still4given View Post
Hi Doug,

Thanks for the detailed answer.

I am flying a Phoenix Models Strega with a YS 1.40. It turns the 14X14N at about 9800. Unfortunately, that is not quite enough to reach breakout in our Gold class. We changed the rules this year and now electric power is allowed so I am looking at different options to see if I can build something cool for next season.

There is guy who is building an E-flite P-51B wit a Scorpian 4045, 560kV and is turning a 13x13.5 around 10,500.

Thanks, Terry
Hi Terry: I just knew you had to have a MONSTER in there to spin that prop. Huge prop for a 40 size plane!! I don't recognize the other guys 4045,560kv, maybe its something new I missed!
Is cell count unimportant (you can use whatever you need)? I'm intrigued enough to do some more digging!! What kind of speed are you looking for?
Higher cell counts lower amperages, higher rpm's isn't the issue, it is turning that big nitro prop!! I'll see what I can find, Doug B
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Old Dec 21, 2010, 01:04 AM
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Victorville, CA
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Hi Doug,

I may be wrong about the motor. I am repeating what I was told. My friend who shared it with me in not the guy who is actually building it. They have flown it and are getting around 130 MPH. it takes about 145-150 MPH to breakout in gold. The majority of the gold planes run YS engines on high nitro. The new YS 1.15 will most likely dominate this season unless we can come up with some killer EP planes. My backup gold plane is a cub with a Nelson. There are a few ways to get there but I would really like to see what I can do with electric.

Thanks, Terry
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Old Dec 21, 2010, 11:50 AM
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Fourdan's Avatar
Antony (France)
Joined Sep 2003
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Quote:
Originally Posted by Doug Bartley View Post
Hi again Edgar: I have not tested either of the proposed motors here. What I have found is that the generic testing is based on some formula that in reality doesn't work for any combo I've tested. i don't know any way to get accurate measurements except to do it yourself. I see at least a 20% lower amp numbers in my tests.
Here's an example: 4025-12 15/8/3 blade, Scorpion Calc shows 86.5amps and 1921 watts. My test showed 58 amps and 1400 watts. 27% difference!
I'd be tempted to buy one of each motor size, and one of each prop size, and run my own tests on your preferred cell count.
On a project of this scope and costs, it may be the only way to assure results unless someone here has already done it!! FWIW Doug Bartley
Hi Doug
As a 15/8/3 (3 blades) is not in the library you are using the "generic prop" mode.
In this case you could change the Kp coefficient to around 0.6 to match your results (Power Into or current)
A lot of 3 blades prop have narrow blades so the Kpower coefficient is generally 0.6 .. 0.7
What is the brand of your 15x8x3 prop ?(for my info)
Regards
Louis
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Old Dec 21, 2010, 11:56 AM
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Antony (France)
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Hello (to Edgar Perez)

Don't forget that generic props (case of 3 blades) are leading to some incertitude regarding the Power Into.
Generally the coefficient Kpower should be set to 0.7 instead of default 1.0
It could depend of the prop brand, blades narrow or medium or large.
So take the results with a grain of salt
Regards
Louis
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Old Dec 21, 2010, 12:36 PM
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Dennis Everett's Avatar
United States, CA, Ontario
Joined Mar 2002
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Louis , any ideas on chipped magnets as posted above ? post 7541 .
Are thease motors seconds ? Two out of two ? , Really ?, you pay three times what a Turnigy cost and get really poor workmanship/QA ...Dennis
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Old Dec 21, 2010, 12:57 PM
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Fourdan's Avatar
Antony (France)
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Originally Posted by Dennis Everett View Post
Louis , any ideas on chipped magnets as posted above ? post 7541 .
Are thease motors seconds ? Two out of two ? , Really ?, you pay three times what a Turnigy cost and get really poor workmanship/QA ...Dennis
Hi Dennis
I don't see clearly on your pictures post 7541
Probably Lucien will answer about your problems.
Note that I am not a Scorpion employee, but independant.
Anyway I find Scorpion motors are high quality like some other brands.
Probably the risk of having a problem is higher with a Turnigy.
Nothing is perfect.
Louis
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Old Dec 21, 2010, 02:18 PM
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United States, CA, Los Angeles
Joined Mar 2007
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Originally Posted by Dennis Everett View Post
I received my scorp 3026-710 in the mail today


I had a problem with a earlier motor having the magnets chipped out of the box so i took this one apart , it also has small chips in the magnets , WTH ! its hard to get a clear picture , maybe you can tell if this is gonna be a problem ?

The last one i flew before looking inside , power was way down .......

black dots are where chips are ..
I'd say give them a call and also reference this post when you do. Inovative is a first rate operation and they do take care of thier customers.

We all hate to get something bad, but considering the volume of motors that goes thru, it's always possible to get the lemon, twice? not as likely but hey it can happen, been there done that.

Lucien and his cmpany will see to it your taken care of and I'd be willing to bet the farm you will be posting as such after talking to them.

MIke R
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Old Dec 21, 2010, 02:42 PM
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United States, CA, Ontario
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I bought it from RC Dude , i contacted them and they will exchange it if i want , so im happy about that , the last one i got (chipped worse and magnets had very uneven spacing) Lucien exchanged it , but they were out of stock and it took 6 weeks to get a replacement , im really supprised its happened to two motors in a row , when i opened this one up my heart sank , the first one was really down on power thats why i took it apart , this one hasnt been flown ( crappy weather)
I had a monster power 32 in the plane ( 55 span airfield p-51, my avatar) and it flys very nice with it and they are 20.00 with free shipping , i wanted a little more power so i got the scrorp .....
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Old Dec 21, 2010, 05:16 PM
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Joined Aug 2005
109 Posts
Quote:
Originally Posted by Fourdan View Post
Hello (to Edgar Perez)

Don't forget that generic props (case of 3 blades) are leading to some incertitude regarding the Power Into.
Generally the coefficient Kpower should be set to 0.7 instead of default 1.0
It could depend of the prop brand, blades narrow or medium or large.
So take the results with a grain of salt
Regards
Louis
Hi Louis,
Thanks. My guess is that the 4020 will be a better choice, since its has more power than the 3032 and can take these 3 blade props with low Kpower. I will likely be using Master Airscrews 13X8 or 12X8
Thanks
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Old Dec 21, 2010, 11:32 PM
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Canada, ON, Owen Sound
Joined Oct 2008
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Quote:
Originally Posted by Fourdan View Post
Hi Doug
As a 15/8/3 (3 blades) is not in the library you are using the "generic prop" mode.
In this case you could change the Kp coefficient to around 0.6 to match your results (Power Into or current)
A lot of 3 blades prop have narrow blades so the Kpower coefficient is generally 0.6 .. 0.7
What is the brand of your 15x8x3 prop ?(for my info)
Regards
Louis
Hi Louis: In this case, it is an EMP prop, also sold under the Hobby King brand, actually a very good prop for the price and far lighter than the MAS, graupner props. this one flies my 15 lb Turbo beaver very nicely!! Doug B
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Old Dec 21, 2010, 11:41 PM
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Canada, ON, Owen Sound
Joined Oct 2008
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Originally Posted by still4given View Post
Hi Doug,

I may be wrong about the motor. I am repeating what I was told. My friend who shared it with me in not the guy who is actually building it. They have flown it and are getting around 130 MPH. it takes about 145-150 MPH to breakout in gold. The majority of the gold planes run YS engines on high nitro. The new YS 1.15 will most likely dominate this season unless we can come up with some killer EP planes. My backup gold plane is a cub with a Nelson. There are a few ways to get there but I would really like to see what I can do with electric.

Thanks, Terry
I will with the new info posted here have another look at specs. the trick here will be to find a light system but few can handle the 14x14 prop. thanks for posting the speed your looking for, that helps!
How much does your Strega setup weigh with the 140 in it?
How long is a race? Is it a required number of laps? This will help determine the C ratings/ cell counts/ and sizing for the required time to fly an event!
We can see where we could go from there!! Doug B
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Old Dec 22, 2010, 03:27 AM
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still4given's Avatar
Victorville, CA
Joined Jun 2006
1,114 Posts
Hi Doug,

The race lasts about 1 1/2 minutes. It is 10 laps on a 700' two pole course. There is a 90 second period to get the plane started and launched and a 45 second countdown to the flying start, but the actual race is only about 90 to 110 seconds.

My Strega weighs about 7 1/2 lbs. It could be flown with a smaller prop at higher rpm. I think my friend is presently using a 13x13.5 which is what I use on my YS 1.10. I used the 14x14 as an example since I know what I need with that prop. I'm sure there are several different combinations that would work. It's just the idea of using the larger prop is appealing me.

This is the info I got from my friend on their setup

"APC 13x13.5 @ 10,400 rpm, 6S 5000 LiPo, 136-138 mph. Wing area 460 square inches, finished weight (with battery) 7 lbs 12 oz. The motor is a Scorpion outrunner 4045 heli motor (560kv) with a reversed airplane shaft from Innov8tive Designs
"


I couldn't find the 4045 on Scorpion's list. Maybe he has the number wrong.

Thanks, Terry
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